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Arcee AI 207

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039716988

description

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawings this shows a nuclear reactor fuel element assembly comprising an outer tubular casing 1 of hexagonal cross-section; the casing 1 is of stainless steel. Within the casing 1 there is arranged an assembly of thirty-six breeder pins 2 and one hundred and twenty-seven fuel pins 3. The fuel pins 3 extend longitudinally through the casing 1 parallel one to another and are arranged in hexagonal lattice form. The breeder pins 2 are arranged in an outer row surrounding the assembly of fuel pins 3. Each of the fuel pins 3 comprises a tubular sheath of stainless steel containing fissile nuclear fuel material which is of ceramic form. Spacing means for the fuel pins 3 comprises a helically wrapped wire 4 on the sheath of each fuel pin 3. Likewise each of the breeder pins 2 comprises a tubular sheath of stainless steel containing nuclear breeder material which also is of ceramic form. The sheaths of the breeder pins 2 are also provided with helically wrapped wires 4 serving as spacing means. The breeder pins 2 and the fuel pins 3 are supported at their lower ends within the casing 1 by a bottom support grid 5 which is mounted from a support ring 6 fitted inside the lower end of the casing 1. Referring now especially to FIG. 2, the outer ring of breeder pins 2 is separated from the inner assembly of fuel pins 3 by a barrier construction 7. Being of hexagonal cross-section the casing has six flat sides 8. The barrier construction 7 comprises six individual separator baffles 9 which extend longitudinally inside the casing 1 parallel to the inside faces of the sides 8. Each of the separator baffles 9 is formed from a strip of stainless steel sheet the longitudinal edges of which are bent over to form flanges 10. The flanges 10 are welded along the internal corners between adjacent sides 8 of the casing 1. Passageways 11 are thus defined between the separator baffles 9 and the inside faces of the sides 8 of the casing 1. Each passageway 11 contains the six breeder pins 2 which extend adjacent the corresponding side 8 of the casing 1. As shown in FIG. 1 an extension sleeve 12 is fitted into the lower end of the casing 1. The extension sleeve 12 is of hexagonal cross-section corresponding to the cross-section of the casing 1. The end of the casing 1 engages an external rebate 13 on the extension sleeve 12 and is secured to the sleeve by a circumferential edge weld 14. The extension sleeve 12 has a bore 15 of circular cross section. At its upper end the bore 15 opens into a conical throat 16. At its lower end the bore 15 has a counterbore 17 of large diameter. A main gag assembly 18 is fitted in the bore 15 of the extension sleeve 12. The gag assembly 18 comprises an outer sleeve 19 which is a close fit in the bore 15, a collet sleeve 20 which is split longitudinally in two halves 21 and fits inside the outer sleeve 19, and a series of toroidal rings 22 having wire mesh discs 23 and fitting in longitudinally spaced annular grooves 24 inside the collet sleeve 20. The lower end of the barrier construction 7 is shaped to fit about the upper end of the outer sleeve 19 of the gag assembly 18 the outer sleeve 19 forms a lower extension of the barrier construction 7. Six longitudinal slots 25 in the bore 15 of the extension sleeve 12 connect between the conical throat 16 at the upper end of the bore 15 and the counterbore 17 at the lower end of the bore 15. The longitudinal slots 25 in the bore 15 of the extension sleeve 12 are disposed in alignment with the passageways 11. As shown in FIG. 3 a gag ring 26 is fitted in the counterbore 17 at the lower end of the bore 15 in the extension sleeve 12. The gag ring 26 fits about a raised circumferential land 27 on the outer sleeve 19 of the gag assembly 18. The gag ring has six ports 28 which correspond to the six longitudinal slots 25 in the bore 15 of the extension sleeve 12. A spike member 29 at the lower end of the fuel element assembly comprises an upper end adaptor sleeve 30. The adaptor sleeve 30 has a head 31 corresponding in shape to the lower end of the extension sleeve 12 with which it is cojoined. The adaptor sleeve 30 has an external cylindrical bearing surface 32 of smaller diameter than the head 31 and a bore 33. The head 31 of the adaptor sleeve 30 has a circumferential rebate 34 which fits inside the lower end of the extension sleeve 12. As shown in FIGS. 4 and 5 the extension sleeve 12 and the upper end adaptor sleeve 30 are fastened together by twelve high tension socket headed screws 35 which, as shown in FIG. 3 extend through external longitudinal slots 36 in the gag ring 26. As shown in FIGS. 1 and 4 six longitudinal slots 37 inside the head 31 of the adaptor sleeve 30 lead from the bore 33 therein and are disposed in alignment with the ports 28 in the gag ring 26 and with the longitudinal slots 25 in the bore 15 of the extension sleeve 12. The spike member 29 also includes a strut member 38 which extends co-axially from the adaptor sleeve 30. The strut member 38 has three radially extending spider arms 39 at its upper end and the spider arms 39 fit inside the upper end of the bore 33 in the adaptor sleeve 30. The bore 33 of the adaptor sleeve 30 has an internal circumferential land 40 and the spider arms 39 of the strut member 38 have rebates 41 at the ends of their outer faces 42, which rebates 41 engage with the internal land 40 in the bore 33 of the adaptor sleeve 30 and thus locates the strut member 38 longitudinally with respect to the adatpor sleeve 30. The lower end of the strut member 38 has a cylindrical boss 43 over which there is fitted a lower nose piece 45. The nose piece 45 has an external cylindrical bearing surface 46 and is located on the cylindrical boss 43 of the strut member 38 by two straight pins 47 secured in holes in the body of the lower nose piece 45 and serving to hold it loosely to the strut member 38. The pins engage with a groove 48 around the cylindrical boss 43 of the strut member 38. A filter assembly 49 forming part of the spike member 29 comprises upper and lower toroidal ring members 50 and 51 which are joined by longitudinal rods 52. Intermediate spacing of the rods 52 is by inner ring members 53 which engage with grooves 54 in the rods 52. The upper ring member 50 of the filter assembly 49 fits around a rebate 55 at the lower end of the adaptor sleeve 30 of the spike member 29. The lower ring member 51 of the filter assembly 49 fits around a rebate 56 at the upper end of the nose piece 45 of the spike member 29. The sub-structure of the filter assembly 49 comprising the upper and lower ring members 50, 51 and the longitudinal rods 52 is covered by a wire gauze filter sleeve 57. In use the fuel element assembly of FIG. 1 forms part of the core structure of a nuclear reactor with the spike member 29 plugged into a bottom core support structure or diagrid 58. The diagrid 58 comprises upper and lower plate members 59 and 60. The spike member 29 fits in the diagrid 58 with the cylindrical bearing surface 32 of the adaptor sleeve 30 fitting in an aperture 61 in the upper plate member 59 of the diagrid 58 and with the lower nose piece 45 of the spike member 29 fitting in an aperture 62 in the lower plate member 60 of the diagrid 58. In operation of the reactor liquid sodium coolant is passed into the fuel element assembly from the interspace between the upper and lower plate members 59 and 60 of the diagrid 58. Sodium flows into the fuel assembly through the filter assembly 49 of the spike member 29. The main sodium flow is through the main gag assembly 18 and then over the assembly of fuel pins 3 inside the barrier construction 7 within the casing 1. However a proportion of the sodium passes through the ports 28 in the gag ring 26 and then passes through the longitudinal slots 25 in the bore 15 of the extension sleeve 12 to enter the passageways 11 which are defined between the separator baffles 9 and the inside faces of the sides 8 of the casing 1. The sodium passes up the passageways 11 over the breeder pins 2 contained therein. It is arranged that the rate of sodium flow through the passageways 11 over the breeder pins 2 is greater than the rate of main sodium flow over the fuel pins 3. Thus the sodium flowing over the breeder pins 2 will be at a lower temperature than the sodium flowing over the fuel pins 3. The sodium flowing over the breeder pins 2 will also be inherently at a lower temperature because of the lesser heat generation in the breeder pins 2. This means that the casing 1 of the fuel element assembly will be operated at a lower temperature than would be the case if the casing were subjected to the temperature of the main sodium flow over the fuel pins 3. Operation of the casing 1 of the fuel element assembly at a lower temperature reduces the amount of irradiation induced voidage growth which occurs in the casing 1 of the fuel element assembly. Therefore where the fuel element assembly is located in a position in the reactor core structure where it will be subjected to a transverse gradient in the neutron flux the amount of bowing of the fuel element assembly due to differential growth of the casing under irradiation will be reduced. The gag ring 26 can be adjusted in angular position before charging of the fuel element assembly into the reactor core structure so as to adjust the degree of overlap of the ports 28 in the gag ring with the longitudinal slots 25 in the bore of the extension sleeve 12. By this means the rate of sodium flow over the breeder pins 2 can be preset to the required amount. In FIG. 6 a fuel assembly with a casing 1 of circular section is shown. The separator baffles 9 are fitted with additional pad members 63 which locate the breeder pins 2 against the inside faces of the casing 1. The pad members 63 are continuous over the full length of the baffles 9 but they may be made discontinuous along the length of the baffles 9 to serve as local supports only. The continuous pad members 63 form open ducts for coolant flow but alternatively they may be arranged to enclose stagnant columns of coolant. At the upper end of the fuel element assembly the separate sodium flows from each side of the separator baffles 9 are allowed to mix giving a uniform coolant outlet temperature from the fuel element assembly. This can be achieved by means of V-slots cut in the upper ends of the separator baffles 9 allowing gradual mixing of the two flows.

abstract

The invention relates to sealing a fuel rod composite cladding tube composed of silicon carbide regardless of the fuel rod cladding design architecture (e.g., monolithic, duplex with monolithic SiC on the inside and a composite made with SiC fibers and SiC matrix on the outside) preferably with sealed SiC end plug caps, additionally sealed with an interior braze and exterior SiC final coating, thus providing a double sealed end plug barrier effective at retaining gas tightness and providing mechanical strength for the sealed end joint while providing high chemical resistance.

043483518

description

The following examples relate to the method according to the invention utilizing specific numerical values in the preceding mathematical relationships. Specifically, a commercially desired neutron doped silicon material specification is listed hereinbelow with example I illustrating the shortcomings of art taught selection while example II illustrates the method according to the invention and application of the mathematical selection process listed hereinabove. EXAMPLES A commercially meaningful neutron transmutation doped single crystal silicon material would require resistivity of 50 ohm-cm.+-.15%. The resistivity limits are hence 42.5-57.5 ohm-cm. Converting resistivities to dopant concentrations according to the mathematical definition, we have; ##EQU2## EXAMPLE I Example I utilizes the prior art taught selection method wherein resistivity limits for starting materials provide maximum dopant concentration in starting material equal to 0.1 times average concentration in final product which is equal to 0.1 times 1.92 which is equal to 0.192 ppb (parts per billion dopant impurity), Minimal resistivity for "N" type starting material would equal to 500 ohm-cm while minimal resistivity for "P" type starting material would equal 1300 ohm-cm and no starting material would be utilized with p-n junctions. EXAMPLE II Resistivity limits for starting material under the method according to the invention utilizes maximum dopant difference in starting material equal to .DELTA.C.sub.s equal to C.sub.D max-C.sub.D min=0.59 ppb. Homo geneity factor as defined herein and for the purposes of this invention of the final product is a.sub.D equals .DELTA.C.sub.D /C.sub.D equals 0.59/1.92 equals 0.307 and homogeneity factor for starting material as defined for the purposes of this invention is represented by a.sub.s and equals 0.600. The homogeneity factor of starting material is based on the results of measurements on many pieces of starting material, and is the maximum inhomogeneity likely to be encountered. The maximum average dopant concentration in the starting material is equal to C.sub.s which equals a.sub.D /a.sub.s times C.sub.D equal to 0.307/0.600 times 1.92 equal to 0.98 ppb "N" or "P" type. Minimal resistivity equals 98 ohm-cm "N" type or 255 ohm-cm "P" type. The selection of material containing p-n junctions will be illustrated with two examples, the first example showing an acceptable piece, the second example having a rejectable piece. Donor concentrations will be considered positive numbers and acceptor concentrations as negative numbers. EXAMPLE III Max donor concentrations=0.3 ppb Max acceptor concentrations=0.1 ppb Max difference=0.3-(-0.1)=0.4 ppb which is less than 0.59 ppb Material is acceptable. EXAMPLE IV Max donor concentrations=0.3 ppb Max acceptor concentrations=-0.4 ppb Max difference=0.3-(-0.4)=0.7 ppb which is more than 0.59 ppb; thus, the material must be rejected.

claims

1. A floating nuclear reactor, comprising:a tank having water therein which includes;(a) a horizontally disposed bottom wall having a first end, a second end, a first side and a second side;(b) a vertically disposed first end wall, having a first side, a second side, a lower end and an upper end, extending upwardly from said first end of said bottom wall;(c) a vertically disposed second end wall, having a first side, a second side, a lower end and an upper end, extending upwardly from said second end of said bottom wall;(d) a vertically disposed first side wall, having a first end, a second end, a lower end and an upper end, extending between said first ends of said first and second end walls;(e) a vertically disposed second side wall, having a first end, a second end, a lower end and an upper end, extending between said second ends of said first and second end walls;each of said first end wall, said second end wall, said first side wall and said second side wall of said tank having inner and outer sides;said tank being partially or completely buried in the ground;a barge, having a first end, a second end, a first side and a second side, floatably positioned in said tank;an upstanding nuclear reactor positioned on said barge at said second end of said barge;said nuclear reactor including an upstanding first containment member having an upper end and a lower end;a first cone mounted on said upper end of said first containment member which extends upwardly therefrom so that the apex of said cone is uppermost; anda roof extending over said barge and said first cone. 2. A floating nuclear reactor, comprising:a tank having water therein which includes;(a) a horizontally disposed bottom wall having a first end, a second end, a first side and a second side;(b) a vertically disposed first end wall, having a first side, a second side, a lower end and an upper end, extending upwardly from said first end of said bottom wall;(c) a vertically disposed second end wall, having a first side, a second side, a lower end and an upper end, extending upwardly from said second end of said bottom wall;(d) a vertically disposed first side wall, having a first end, a second end, a lower end and an upper end, extending between said first ends of said first and second end walls;(e) a vertically disposed second side wall, having a first end, a second end, a lower end and an upper end, extending between said second ends of said first and second end walls;each of said first end wall, said second end wall, said first side wall and said second side wall of said tank having inner and outer sides;said tank being partially or completely buried in the ground;a barge, having a first end, a second end, a first side and a second side, floatably positioned in said tank;an upstanding nuclear reactor positioned on said barge at said second end of said barge;said nuclear reactor including an upstanding first containment member having an upper end and a lower end;a first cone mounted on said upper end of said first containment member which extends upwardly therefrom so that the apex of said cone is uppermost;a second containment member, having an upper end, positioned on said barge;a second cone positioned on said upper end of said second containment member with said second cone being comprised of metal material whereby an aircraft or missile striking said second cone will be disintegrated and deflected by said second cone; anda roof extending over said barge and said first and second cones. 3. A floating nuclear reactor, comprising:a tank having water therein which includes;(a) a horizontally disposed bottom wall having a first end, a second end, a first side and a second side;(b) a vertically disposed first end wall, having a first side, a second side, a lower end and an upper end, extending upwardly from said first end of said bottom wall;(c) a vertically disposed second end wall, having a first side, a second side, a lower end and an upper end, extending upwardly from said second end of said bottom wall;(d) a vertically disposed first side wall, having a first end, a second end, a lower end and an upper end, extending between said first ends of said first and second end walls;(e) a vertically disposed second side wall, having a first end, a second end, a lower end and an upper end, extending between said second ends of said first and second end walls;each of said first end wall, said second end wall, said first side wall and said second side wall of said tank having inner and outer sides;said tank being partially or completely buried in the ground;a barge, having a first end, a second end, a first side and a second side, floatably positioned in said tank;an upstanding nuclear reactor positioned on said barge at said second end of said barge;said nuclear reactor including an upstanding first containment member having an upper end and a lower end;a first cone mounted on said upper end of said first containment member which extends upwardly therefrom so that the apex of said cone is uppermost;a roof extending over said barge and said first cone; anda suspension system connecting said barge to said tank which permits said barge to move downwardly in said tank should an aircraft or missile strike any part of said roof to absorb some of the impact experienced by said roof. 4. A nuclear reactor, comprising:an upstanding containment member having a nuclear reactor vessel positioned therein;said containment member having an upper end;a protective cone mounted on the upper end of said containment member;said protective cone extending upwardly from said upper end of said containment member whereby the apex of said protective cone is uppermost;said cone being comprised of a metal material whereby an aircraft or missile striking said first cone will be disintegrated and deflected by said cone; anda roof extending over said cone. 5. A nuclear reactor, comprising:an upstanding first containment member having a nuclear reactor vessel positioned therein;said first containment member having an upper end;a hollow protective cone mounted on the upper end of said first containment member;said protective cone extending upwardly from said upper end of said first containment member whereby the apex of said protective cone is uppermost;a second containment member having an upper portion;a hollow protective cone mounted on said upper portion of said second containment member which extends upwardly from said upper portion thereof whereby the apex of said protective cone is uppermost;each of said protective cones being comprised of metal material whereby an aircraft or missile striking said protective cone will be disintegrated and deflected by said cone; anda roof extending over said protective cones.

description

The present invention relates generally to ion implantation systems and methods, and more particularly, to a method for addressing ion beam discrepancies during ion implantation. Ion implantation systems are used to impart impurities, known as dopant elements, into workpieces such as semiconductor substrates or wafers. In a typical ion implantation system, an ion source ionizes a desired dopant element, and the ionized impurity is extracted from the ion source as a beam of ions. The ion beam is directed (e.g., swept or scanned) across respective workpieces to implant ionized dopants within the workpieces. The dopant ions thus alter the composition of the workpieces, causing them to possess desired electrical characteristics, such a may be useful for fashioning particular semiconductor devices, such as transistors, upon the substrates. The continuing trend toward smaller electronic devices has driven the need to form a greater number of smaller, more powerful, and more energy efficient semiconductor devices onto individual workpieces. Thus, careful control over semiconductor fabrication processes such as ion implantation, and more particularly, the uniformity of ions implanted into the workpieces, is necessitated. Moreover, semiconductor devices are being fabricated upon larger workpieces to increase product yield. For example, wafers having a diameter of 300 mm or more are being utilized so that more devices can be produced on a single wafer. Such wafers are expensive and as such, it is highly desirable to mitigate waste, such as having to scrap an entire wafer due to non-uniform ion implantation. However, larger wafers and high density features can make uniform ion implantation challenging, since the ion beam is scanned across greater angles and distances in order to reach the perimeters of the wafers, yet not miss implanting any region therebetween. In addition, the high voltage typically necessary to supply the ion source is subject to occasional arcing between various extraction and suppression electrodes and other components associated therewith. This tendency for arcing often fully discharges one or more affected high voltage power supplies until the arc naturally self-extinguishes at a much lower supply voltage. While arcing, the beam current may become erratic or interrupted until the supply voltage is restored, during which time ion implantation may experience intermittent ion implantation. Such an arcing and subsequent intermittent ion implantation is commonly referred to as a “glitch”. During serial wafer processing, when a glitch along a path of the ion beam is detected, conventionally, the region or portion of the beam path that failed to be implanted during the glitch is specifically “repaired” by various techniques of re-tracing the path with ion beam in order to “fill in” the non-implanted region. Such repairs are time consuming and sometimes lead to further undesirable effects caused by the starting and stopping of the ion beam in the glitch region, especially when very short glitches occur. Accordingly, there is a need for a dynamic determination of the appropriate action to be taken when a glitch or non-uniformity in the ion beam is detected. The present invention overcomes the limitations of the prior art and provides an inventive method for addressing discrepancies in an ion beam during ion implantation into a workpiece. Accordingly, the following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later. In accordance with the invention, a method for addressing a discrepancy in current or voltage of an ion beam (also called a “glitch”) during an implantation of ions into a workpiece is provided. The method, for example, comprises providing an ion beam, such as spot or pencil beam, wherein one or more of the ion beam and workpiece are scanned with respect to one another in a first direction (e.g., along a first scan path or first axis, also referred to as a “fast scan” axis, path, or direction) and a second direction (e.g., along a second scan path or second axis, also referred to as a “slow scan” axis, path, or direction). The ion beam, for example, may alternatively comprise a ribbon beam. In one example, the workpiece is mechanically scanned in the second direction (e.g., along the second axis) through an ion beam that is electrostatically scanned in the first direction, wherein the second direction (e.g., the direction of travel of the workpiece) is generally perpendicular to the first direction (e.g., the direction of scanning of the ion beam). In accordance with one aspect, a duration for which a glitch in the ion beam is to be disregarded is initially established, therein defining an ion beam glitch duration threshold. The ion beam glitch duration threshold, for example, is based, at least in part, on one or more of a desired final dose uniformity on the workpiece, a number of passes or translations of the workpiece through the ion beam, a velocity of the translation of the workpiece through the ion beam, and a size of the ion beam. The size of the ion beam, for example, is determined based on one or more of direct measurement and a knowledge of beam size based on predetermined system inputs. During implantation of ions into the workpiece, one or more properties, such as a current of the ion beam, are iteratively measured concurrent with the translation of the workpiece through the ion beam. In one example, a counter is reset (e.g., set to zero) whenever the current of the ion beam is greater than a predetermined anomaly current, such as about 10% of normal operational implantation current. A position of the workpiece is stored when the measured current of the ion beam is initially less than the predetermined ion beam anomaly current, therein defining an onset of a glitch. For example, the position of the workpiece in the second direction is stored when the counter is zero and the determined current of the ion beam is less than the predetermined anomaly current. The counter, for example, is incremented for each subsequent iteration that the current of the ion beam is continuously determined to be less than the predetermined ion beam anomaly current. In accordance with the invention, the ion implantation is halted only when the measured current of the ion beam is lower than the predetermined ion beam anomaly current for an amount of time that is greater than the predetermined glitch duration threshold (e.g., the period of time in which the glitch occurs exceeds the predetermined glitch duration threshold). For example, if the counter exceeds the ion beam glitch duration threshold, the ion beam is suppressed and the ion implantation is halted. The portion of the ion implantation associated with the glitch, for example, is subsequently repaired by repositioning the workpiece at the stored position, restarting the ion beam, and again translating the workpiece through the ion beam, therein implanting the portion of the workpiece associated with the glitch. To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. The present invention is directed generally toward ion implantation systems and a method for addressing an intermittent ion beam, wherein a determination regarding an appropriate repair operation is made in-situ. Accordingly, the present invention will now be described with reference to the drawings, wherein like reference numerals may be used to refer to like elements throughout. It should be understood that the description of these aspects are merely illustrative and that they should not be interpreted in a limiting sense. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be evident to one skilled in the art, however, that the present invention may be practiced without these specific details. In the implantation of ions into a workpiece, such as a semiconductor wafer or substrate, it is common to encounter temporary arcing between various components upstream of the workpiece, wherein a temporary loss of ion beam power or beam current occurs. In conventional serial ion implanters, such a loss of ion beam power or current, also called a “glitch”, typically lead to repairs being made to the workpiece being processed. Such repairs, however, have the potential to cause more significant problems on the workpiece, and furthermore, take valuable processing time to perform. Heretofore, no determinations have been conventionally made as to the necessity of the repair, as most all such glitches were considered to be cause for repair. The present invention advantageously uses a quality threshold, such as one provided by a customer or by statistical data, to determine whether a repair to a glitch should be performed. FIG. 1 illustrates an exemplary ion implantation system 10 having a terminal 12, a beamline assembly 14, and an end station 16. The terminal 12, for example, comprises an ion source 18 powered by a high voltage power supply 20, wherein the ion source produces and directs an ion beam 22 through the beamline assembly 14, and ultimately, to the end station 16. The ion beam 22, for example, can take the form of a spot beam, pencil beam, ribbon beam, or any other shaped beam. The beamline assembly 14 further has a beamguide 24 and a mass analyzer 26, wherein a dipole magnetic field is established to pass only ions of appropriate charge-to-mass ratio through an aperture 28 at an exit end of the beamguide 24 to a workpiece 30 (e.g., a semiconductor wafer, display panel, etc.) positioned in the end station 16. In accordance with one example, an ion beam scanning mechanism 32, such as an electrostatic or electromagnetic scanner, is configured to scan the ion beam 22 in at least a first direction 33 (e.g., the +/− y-direction, also called a first scan path or “fast scan” axis, path, or direction) with respect to the workpiece 30, therein defining a scanned ion beam 34. Furthermore, in the present example, a workpiece scanning mechanism 36 is provided, wherein the workpiece scanning mechanism is configured to selectively scan the workpiece 30 through the ion beam 22 in at least a second direction 35 (e.g., the +/− x-direction, also called a second scan path or “slow scan” axis, path, or direction). The ion beam scanning system 32 and the workpiece scanning system 36, for example, can be instituted separately, or in conjunction with one another, in order to provide the desired scanning of the workpiece relative to the ion beam 22. For example, the ion beam 22 is held generally stationary (e.g., not electrostatically scanned by the ion beam scanning mechanism 32), and the workpiece scanning mechanism 36 is configured to scan the workpiece 30 with respect to the ion beam in both the first direction 33 and second direction 35, therein providing a two-dimensional mechanical scan of the workpiece relative to the ion beam. In another example, the ion beam 22 is electrostatically scanned in the first direction 33, therein producing the scanned ion beam 34, and the workpiece 30 is mechanically scanned in the second direction 35 through the scanned ion beam 34. Such a combination of electrostatic and mechanical scanning of the ion beam 22 and workpiece 30 produces what is called a “hybrid scan”. The present invention is applicable to all combinations of scanning of the workpiece 30 relative to the ion beam 22, or vice versa. According to another example, one or more sensors 38, such as one or more Faraday cups, are further provided along the path of the ion beam 22 in order to measure one or more properties (e.g., ion beam current) of the ion beam. The one or more sensors 38 can be provided upstream or downstream of the workpiece 30, wherein the one or more sensors are configured to sense the one or more properties of the ion beam 22 when the ion beam does not intersect the workpiece. The one or more sensors 38, in another example, are associated with the power supply 20, wherein a current or voltage associated with the power supply is determined. A controller 40 is further provided, wherein the controller is configured to control at least one or more of the ion source 18, high voltage power supply 20, beamguide 24, mass analyzer 26, ion beam scanning mechanism 32, workpiece scanning mechanism 36, and one or more sensors 38. Due, at least in part, to high voltages utilized within various components of the ion implantation system 10, high voltage arcs or sparking can occur at unanticipated times. Such arcs or sparking quite often causes a loss of ion beam current, generally referred to as an ion beam “glitch”, for a short duration of time. The duration of the ion beam glitch, for example, often ranges between tens of microseconds to tens of milliseconds, depending on one or more of the particular component causing the high voltage spark, the condition of the particular high voltage, the voltage load, and the current load. When an ion beam glitch occurs, the workpiece 30 does not receive the desired implant dosage from the ion beam 22 during the duration of the glitch, and, as a result, the ion beam glitch affects the final dose uniformity on the workpiece. The workpiece 30 is generally much larger than a cross-sectional size of the ion beam 22. The present invention contemplates various schemes for providing a uniform dosage of ions across the entire surface of the workpiece 30. One scheme employs one-dimensional scanning of the workpiece 30 in the second direction 35 (e.g., the +/− x-direction) through the ion beam 22, wherein the ion beam comprises a broad ribbon beam 42, as illustrated in FIG. 2. In the one-dimensional scanning, the workpiece scanning mechanism 36 of FIG. 1 mechanically scans the workpiece through the generally-uniform ribbon beam, wherein a width 44 of the ribbon beam is wider than the workpiece, but a thickness 46 of the ribbon beam is substantially thinner than the width. FIG. 3A illustrates a two-dimensional scanning scheme, wherein scanning of the workpiece 30 and ion beam 22 relative to one another in two directions is employed. For example, the two-dimensional scanning illustrated in FIG. 3A can be accomplished by the hybrid scan described above, wherein a “fast scan” of a pencil or spot ion beam 22 in the first direction 33 (e.g., the +/− y-direction) at a relatively fast frequency (e.g., approx. 1 KHz) generally defines the scanned ion beam 34 of FIG. 1, and a relatively slow mechanical scan (e.g., less than 1 Hz) of the workpiece 30 in the second direction 35 (e.g., generally orthogonal to the first direction 33 of the scanned ion beam) provides exposure of the entire workpiece to the spot ion beam. Such a hybrid scan of FIG. 3A, for example, generally defines a raster scan pattern 48 across the workpiece 30, as illustrated in FIG. 3B, wherein a scan pitch 50 (e.g., on the order of approx. 0.1 mm), or distance between two fast scan traces, is significantly smaller than the size of the spot ion beam 22 (e.g., greater than approx. 10 mm). Referring now to FIG. 4, a dose accumulation or distribution 52 along the center line 54 of the workpiece 30 of FIG. 3B is illustrated, wherein the dose accumulation is generally associated with the amount of exposure the workpiece 30 is subjected to the ion beam 22 of FIG. 1. Due to the mechanical scanning of the workpiece 30 in the second direction 35 (e.g., the slow scan or x-direction) of FIG. 3A, for example, the ion beam center position shifts a small distance in the second direction (e.g., associated with the scan pitch 50 of FIG. 3B) for each scan of the ion beam 22 across the workpiece in the first direction 33. The resulting dose distribution 52 is a superposition of all beam profile passes 55, as illustrated in FIG. 4. In order to provide adequate dose uniformity, as well as to build up an adequate final dosage of ions on the workpiece 30 of FIG. 1, for example, the slow scan (e.g., the slow mechanical scan in the second direction 35) is repeated one or more times, typically with a minimum of two passes (e.g., a forward and backward pass along the x-axis) of the workpiece through the ion beam 22. When an ion beam glitch (e.g., an anomaly in the ion beam 22) occurs, the effect of the glitch on final dose distribution is determined by several factors, including the total number of passes of the workpiece 30 relative to the ion beam. The inventors contemplate that if, for example, an implant comprises one hundred passes of the workpiece 30 in the second direction 35 through the scanned ion beam 34, and only one out of the total one hundred passes contains a glitch, the maximum effect of the glitch to the final dose is less than or equal to 1% for the entire workpiece, and this may be well within the acceptable level of uniformity of the implant. However, if the total number of passes in the second direction 35 for a particular implant is small, such as one complete forward and backward pass along the slow scan path, dose distribution from a glitch can become quite important. Dose distribution from a glitch, for example, is not a simple shape of ion beam dropout, but rather, is given as a superposition (or a convolution) of shifted ion beam profiles and beam dropout length, where beam dropout length is given by beam dropout time duration and slow scan velocity. FIG. 5A, for example, illustrates a scenario where a current of the ion beam drops out for a short period, identified as a glitch 56. FIG. 5B illustrates the superposition of beam profiles 57 similar to that of FIG. 4; however, several beam profiles are missing in FIG. 5B during the dropout during the glitch 56. FIG. 5C illustrates, in general, a final dose distribution 58 as a superposition of the beam profiles 57 of FIG. 5B, showing the much milder total effect of the on the final dose distribution during the glitch 56 or beam dropout. The effect of a glitch to the dose distribution 58, i.e., the depth and width of the reduced dose, generally depends on three factors: the length of beam dropout (glitch duration), the beam size in the second direction 35 of FIG. 3A (e.g., the slow scan direction), and the speed of travel of the workpiece in the second direction (e.g., the slow scan speed). The present invention contemplates that even if a current of the ion beam 22 entirely drops to zero for a short duration, the resultant dose of the pass (e.g., as illustrated on FIG. 5C) will rarely see a complete disappearance of the final dose. On a short beam dropout (e.g., a short glitch duration) with wide beam size and relatively slow scan speed in the second direction 35 of FIG. 3A, for example, the effect is minimal. However, as evidenced in FIGS. 6A-6C, for example, a long beam dropout (e.g., a relatively long glitch duration) with a narrow beam size and relatively fast scan speed in the second direction 35 of FIG. 3A, the overall final dose may reach to zero in portions of the workpiece, as shown in FIG. 6C. The effect of a glitch on the dose distribution 58 is diluted, however, if there are more passes without any glitches, as illustrated in FIG. 7. On a particular implant, good estimates are provided on the total number of passes in the second scan direction 35 of FIG. 3A, the scan velocities in the first direction 33 and second direction, as well as the size and shape of the ion beam 22. Therefore, the degree of dose uniformity deterioration by a glitch can be well estimated according to duration of the glitch, in accordance with the present invention. FIG. 8 is an exemplary graph 60 further illustrating an example of the depth of missing implant dosage during a glitch according to glitch duration at two differing scan velocities for a single scan pass in the second direction 35 of FIG. 3A. For an implant having two or more passes in the second direction 35, the total uniformity deterioration is obtained by dividing by the total number of passes in the second direction. The graph 60 of FIG. 8 illustrates, for example, that a glitch should be shorter than 5 msec if the maximum acceptable missing dose is 2% for a single-pass implant at a velocity in the second direction of 10 cm/sec. Otherwise, a glitch longer than 5 msec, under the same criteria, will result in a dosage uniformity (e.g., dose distribution 58 of FIG. 6C) that is unacceptable. For a two-pass implant, as will be understood from the graph 60 of FIG. 8, the glitch duration can be up to 10 msec, since the effect of the glitch is “diluted”, or roughly halved, by the additional pass. For example, according to the graph 60, a glitch duration of 10 msec in a single pass implant will result in an approximately 4% non-uniformity. Providing a second pass roughly halves the non-uniformity to approximately 2% in a manner similar to that shown in FIG. 7. On most conventional serial processing ion implanters, whenever a glitch is recorded, the position of the slow scan at the onset of the glitch is recorded, and the beam dropout is artificially elongated to a fixed length or to the end of the slow scan (i.e., the beam is intentionally suppressed), so that the missing part can be later filled with precision (also called “repainting”). Typically, this repainting has been done whenever a glitch is recorded, regardless of whether the glitch has a short or long duration. Repainting is a commonly a special “non-routine”process to fill-in a gap created by a particular glitch. Typically, this non-routine process deleteriously consumes extra time in processing, especially when there are many short glitches. As highlighted above, however, the present invention appreciates that damage done by a glitch is generally dependent on factors such as the duration of a glitch, as well as a number of total scans, scan velocity, size of the ion beam, and other factors. The total number of passes of the workpiece through the ion beam, scan velocity and beam size/shape are generally known for a particular implant. The present invention thus establishes a glitch duration threshold for which a glitch can generally be disregarded, as will be further discussed infra. For example, if an experienced glitch duration is longer than the glitch duration threshold, in accordance with the present invention, damage to uniformity would be determined to be too large to be ignored, and the repaint process would be initiated. Alternatively, if the experienced glitch duration is shorter than the glitch duration threshold, the resultant damage to uniformity would be considered to be acceptable in accordance with the present invention, and repair or repainting of the workpiece is not performed, thus saving valuable processing time over conventional methods. The present invention thus provides a method for determining how to proceed when a glitch occurs during implantation of ions into the workpiece. Acceptable maximum dosage dip is 2% on a two-pass implant having a 10 cm/sec slow scan speed, and the ion beam size is estimated to be 2 cm FWHM Gaussian. In this case, according to the graph 60 of FIG. 8, a dose dip of 4% from the pass is acceptable, since it is two pass implant, and any glitches longer than 10 msec would need to be repainted. Acceptable maximum dosage dip is 2% on a ten-pass implant having a 10 cm/sec slow scan speed with 2 cm FWHM Gaussian beam. Since this is a ten-pass implant, a single glitch to cause up to a 20% dip in a single pass is allowed. From the graph 60, the maximum glitch duration is approximately 50 msec. That is, for this particular implant, a glitch up to 50 msec is permitted without repainting in order to meet the uniformity requirement. However, since most glitches commonly experienced are shorter than 50 msec, repainting will most likely not be required at all for such an implant. In order to determine if repair or repainting of the workpiece is necessary, in accordance with the present invention, a determination is made as to whether the glitch is longer than a predetermined glitch duration threshold, wherein the predetermined glitch duration threshold is calculated from uniformity requirement for the implant, the total number of passes through the ion beam, a scan velocity and a size of the ion beam. Since the duration of a glitch cannot be predicted at the onset of the glitch, however, a position of the workpiece in the second direction (e.g., along the mechanical scan in the slow scan direction 35) at the onset of the glitch is recorded when the glitch is detected. The scanning of the workpiece is continued, however, wherein the presence of an adequate ion beam is checked at short intervals (e.g., per millisecond). Only when the ion beam fails to recover adequately within the predetermined duration, however, is the glitch treated as a required-repair glitch, and a decision is made as to whether to perform a repair procedure, wherein the area of the workpiece that experienced the glitch is “repainted” or implanted again. The repair procedure artificially elongates the absence of the ion beam (also called suppression of automatic beam comeback) to a predetermined position (e.g., the end of the pass or scan in the second or slow-scan direction 35). In accordance with the present invention, when the ion beam adequately recovers within the predetermined glitch duration threshold, however, the effect of the glitch to dose uniformity is ignored and no special actions are taken. Furthermore, according to another example, a “glitch budget” is introduced in the present disclosure. For example, an implant with many passes in the second direction 35, such as ten or more passes in the second direction, has a larger glitch budget than an implant having five or fewer passes in the second direction, as the implant with a greater number of passes is more tolerant to a small number of glitches. However, each glitch experienced for a given workpiece, even if the glitch duration is too short to warrant a repaint by itself, considering the dilution by the rest of “glitch free” implant, subtracts a certain amount from the overall glitch budget, and the implant becomes less tolerant to glitches after each subsequently encountered glitch. For example, an experience of an additional glitch after several previous glitches have already been ignored can cause the glitch budget to reach a point where any further glitches will necessitate a repair or repainting of the workpiece. It should be noted that the present invention is applicable to both broad-beam (ribbon) type and hybrid scanned implants of FIG. 2 and FIGS. 3A-3B, respectively. Therefore, in accordance with another aspect of the present disclosure, FIG. 9 illustrates an exemplary method 100 for addressing a discrepancy during an implantation of ions into a workpiece. It should be noted that while exemplary methods are illustrated and described herein as a series of acts or events, it will be appreciated that the present invention is not limited by the illustrated ordering of such acts or events, as some steps may occur in different orders and/or concurrently with other steps apart from that shown and described herein, in accordance with the invention. In addition, not all illustrated steps may be required to implement a methodology in accordance with the present invention. Moreover, it will be appreciated that the methods may be implemented in association with the systems illustrated and described herein as well as in association with other systems not illustrated. The method 100 of FIG. 9 begins at act 102, wherein an ion beam glitch duration threshold is determined. The determination of the ion beam glitch duration threshold is based, at least in part, on one or more of a desired final dose uniformity final implant dose uniformity on the workpiece, a number of translations or passes of the workpiece through the ion beam, a velocity of the translation, and a size of the ion beam. The size of the ion beam, for example, is determined based on one or more of a direct measurement, a knowledge of beam size based on predetermined system inputs, and an estimate of beam size based on a Gaussian distribution of previous ion beam sizes and known system inputs. In act 104, an implant routine is performed, wherein ions are implanted into a workpiece. The implant routine, for example, comprises translating the workpiece through an ion beam. The ion beam, for example, comprises the scanned ion beam 34 of FIG. 1, wherein the ion beam 22 is scanned along a fast scan axis (e.g., the first direction 33). The workpiece is thus translated through the ion beam along the slow scan axis (e.g., the second direction), therein implanting ions into the workpiece. A current of the ion beam is determined (e.g., measured) and a determination is made in act 106 as to whether the current is greater than a predetermined value (also called an ion beam anomaly current) for adequate or satisfactory implantation. For example, a current of the ion beam above a predetermined noise level (e.g., 10% of normal operating current) is satisfactory for implanting ions into the workpiece. If the determination made in act 106 is such that there is sufficient ion beam current, a counter is set to zero in act 110, and the workpiece is concurrently implanted with ions. The determination of ion beam current in act 106, for example, comprises determining the current of the ion beam via a Faraday cup when the ion beam does not intersect the workpiece. In an alternative example, the determination of the ion beam current in act 106 comprises measuring one or more properties associated with a source of the ion beam, such as a high voltage power supply. If the beam current is not adequate (e.g., the ion beam current is lower than the predetermined noise level, such as less than 10% of normal operating current), a determination is made in act 112 as to whether the counter is zero. If the counter is determined to be zero in act 112, a glitch is determined to have been initially encountered, and a position of the workpiece in the second direction is stored in act 114. The counter is then incremented in act 116. If the determination in act 112 indicates that the counter is non-zero (e.g., a glitch is already occurring), the counter is compared to the glitch duration threshold in act 118. If the counter is less than the glitch duration threshold, then the implant routine continues, and the ion beam current is checked again in act 106. In accordance with one example of the present disclosure, acts 106 through 118 are performed in a predetermined time interval (e.g., 1 millisecond intervals), such that act 106 is repeated at each predetermined time interval. As such, the counter is either set to zero in act 110 or incremented in act 116, and act 106 is performed again at each predetermined time interval (e.g., 1 millisecond). Accordingly, in the present example, the timing of the duration of a glitch encountered during implantation is thus associated with the incrementation of the counter. If the determination in act 118 is such that the counter is greater than the glitch duration threshold, then the implant routine is halted, and a repair or repaint routine is performed in act 120. The repair routine, in one example, comprises recalculating the ion beam glitch duration threshold in act 122, wherein the recalculation is based, at least in part, on one fewer translations of the workpiece through the ion beam. The workpiece, for example, is returned to the position in the second direction that was previously stored in act 114, wherein the implant routine is again performed starting with providing the ion beam again in act 104. In accordance with the present example, if the determination in act 118 is such that the counter is less than the glitch duration threshold, but the ion beam current resumes to an acceptable level prior to again performing act 106, the counter is reset to zero in act 110, and the implantation started in act 104 continues. As such, the glitch is generally ignored. Thus, process efficiencies can be realized by the present invention, wherein time, material, and other savings can be evidenced by selectively ignoring and/or repairing glitches based on the aforementioned methodology, as opposed to performing traditional repairs every time a glitch is encountered, as is done conventionally. Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, etc.), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiments of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several embodiments, such feature may be combined with one or more other features of the other embodiments as may be desired and advantageous for any given or particular application.

046655417

claims

1. The method of x-ray lithography which comprises the steps of generating a single pulse of light having a wavelength in the ultraviolet and a duration not exceeding about one ns, translating said light pulse into a pulse of x-rays, and exposing an x-ray sensitive resist with the x-ray pulse to produce a pattern therein. 2. The method according to claim 1 further comprising the step of increasing the temperature of said resist after exposure to said x-ray pulse. 3. The method according to claim 2 wherein said temperature increasing step is carried out by placing a shield of x-ray transmissive material in the path of said x-ray pulse to said resist and thermally coupled to said resist. 4. The method according to claim 2 wherein said temperature increasing step comprises the step of placing a shield of material which blocks a target material and is heated thereby in thermally coupled relationship with said resist. 5. The method according to claim 1 wherein said translating step is carried out by directing said light pulse to be incident upon a target to produce a plasma of target material which emits said x-ray pulse. 6. The method according to claim 1 wherein said generating step is carried out by producing a beam of laser light, and said translating step is carried out by placing a target in the path of said laser beam to produce a plasma which emits said x-ray pulse. 7. The method according to claim 6 further comprising focusing said laser beam upon a spot approximately 100 .mu.m on said target. 8. The method according to claim 1 wherein said generating step is carried out by producing a single pulse of infrared laser light and tripling the wave length of said infrared laser light pulse, and said translating step is carried out by making the tripled laser light pulse incident on a target which faces said resist. 9. The method according to claim 8 wherein said infrared laser light pulse has a wave length of approximately 1.05 .mu.m and said tripled laser light pulse has a wave length of approximately 0.35 .mu.m. 10. In apparatus for laser lithography wherein an x-ray mask defining a pattern is positioned in proximity to a substrate having an x-ray sensitive resist material thereon, the improvement comprising means including a laser for producing a single pulse of ultraviolet light having a duration of about 1 ns, a target upon which said laser pulse is incident to produce a plasma from which an x-ray pulse corresponding to said laser pulse is transmitted to expose said resist through said mask. 11. The invention according to claim 10 further comprising a shield of material which intercepts target material in said plasma and is heated thereby and which transmits said x-ray pulse disposed between said target and said mask and in close proximity to said mask and thermally coupled thereto for heating said resist upon exposure thereof by said x-ray pulse. 12. The invention according to claim 11 wherein said shield is a body of beryllium. 13. The invention according to claim 12 wherein said beryllium shield is a sheet approximately 18 .mu.m thick placed approximately 25 .mu.m from said resist. 14. The invention according to claim 10 wherein said means including a laser includes a laser operative in the infrared and a tripler which translates the output of said laser to the ultraviolet. 15. The invention according to claim 14 further comprising means for focusing the ultraviolet light from said tripler on the surface of said target to a spot of 100 .mu.m diameter or less. 16. The invention as set forth in claim 10 wherein the laser output wave length is approximately 1.05 .mu.m and said tripler output wave length is approximately 0.35 .mu.m. 17. The invention according to claim 16 wherein the energy of said laser pulse of 0.35 .mu.m is about 35 J. 18. The invention according to claim 10 wherein said resist is selected from PBS, COP, and PMMA. 19. The invention according to claim 11 wherein said target consists of pure iron. 20. The invention according to claim 10 wherein said x-ray pulse presents an energy for absorption by said x-ray resist of approximately 1 J per cm.sub.3.

description

The present application claims priority based on Japanese Patent Application No. 2005-225453, filed on Aug. 3, 2005, the contents of which are hereby incorporated by reference within this application. 1. Field of the Invention The present invention relates to a stencil mask for limiting an irradiation area of charged particles on a surface of a substrate to a predetermined shape. The charged particles may be ionized atoms, electrons, etc. The stencil mask is suitable for manufacturing a semiconductor device that works as a switching element, light emitting element, light detecting element. The stencil mask is also suitable for manufacturing a micromachine. 2. Description of the Related Art In the process of manufacturing the semiconductor device, a process is widely used wherein a local area on a surface of a semiconductor substrate is irradiated with the charged particles, and an area apart from this local area is not irradiated with the charged particles. The local area where the charged particles are irradiated is termed an irradiation area in the present specification. The charged particles are introduced into a surface layer of the semiconductor substrate at the irradiation area. The introduced ionized atoms generally work as impurities. A pattern of the area where the charged particles are introduced into the semiconductor substrate can be controlled by a masking film that prohibits penetration of the charged particles. Generally, the following method is performed for this type of process: a masking film is formed on the entire surface of the semiconductor substrate, penetrating holes are formed in the masking film, and the surface of the semiconductor substrate that is exposed from the masking film is irradiated with the charged particles. This method requires a step of forming the masking film on the surface of the semiconductor substrate, a step of forming the penetrating holes in the masking film, and a step of removing the masking film, etc. This method therefore has the problem that many steps are required for manufacturing the semiconductor device. Stencil masks have been developed in order to solve this problem. Stencil mask is a masking member in which a penetrating hole has already been formed. In a method of utilizing a stencil mask, the stencil mask is disposed above the semiconductor substrate. The charged particles are irradiated toward the surface of the semiconductor substrate through the penetrating hole in the stencil mask. The stencil mask limits the irradiation area of the charged particles to be substantially equal to the pattern of the penetrating hole. The stencil mask can be used repeatedly for a plurality of semiconductor substrates. The method of utilizing the stencil mask does not require the step of forming the masking film on the surface of the semiconductor substrate, the step of forming the penetrating hole in the masking film, nor the step of removing the masking film. The method of utilizing the stencil mask can therefore considerably reduce the number of steps required for manufacturing the semiconductor device. The stencil mask comprises a flat plate-shaped member in which the penetrating hole is formed. The penetrating hole has a shape that substantially corresponds to the irradiation area of the charged particles. The penetrating hole is usually formed by etching the flat plate-shaped member using the RIE (Reactive Ion Etching) method or the like. Since there are limits as to the value of the aspect ratio (the value when the depth of the penetrating hole is divided by the width of the penetrating hole) in the currently available etching processes, a thin flat plate-shaped member must be used for forming the penetrating hole whose width is narrow, or for forming a pair of penetrating holes which are separated with a thin wall. Various types of patterns of the irradiation area are required to be formed on the surface of the semiconductor substrate. Therefore, the penetrating hole or holes of the stencil mask must also be formed in various shapes. As a result, the problem can arise that forming the penetrating hole or holes causes deformation of the plate-shaped member to easily occur near side walls defining the penetrating hole or holes. Techniques for preventing the deformation of the plate-shaped member are required. Further, there is a case that the pattern of the irradiation area has a looping shape. In this case, the penetrating hole must also have the looping shape. However, when the penetrating hole is in the looping shape, the part of the flat plate-shaped member surrounded by the looping hole becomes separated from the part of the flat plate-shaped member surrounding the penetrating hole. Techniques for preventing this separation are also required. In order to deal with these problems, a technique was taught in Japanese Patent Application Publication No. 2002-280290, in which beam members are formed within the penetrating hole of the stencil mask. The beam members pass across the penetrating hole, thus connecting one part of the flat plate-shaped member, which had been divided by the penetrating hole, with the other part of the flat plate-shaped member. The beam members strengthen the stencil mask near the side walls defining the penetrating hole, and can prevent the deformation of this part. Further, in the case where the penetrating hole has a looping shape, the beam members connect the part of the flat plate-shaped member surrounded by the looping hole and the part of the flat plate-shaped member surrounding the penetrating hole, thus preventing the inner side of the flat plate-shaped member (island portion) separated from the outer side of the flat plate-shaped member. If beam members are formed using the technique taught in Japanese Patent Application Publication No. 2002-280290, deformation of the stencil mask can be suppressed even when various patterns of the penetrating hole or holes are formed. However, when the charged particles were introduced with this type of the stencil mask, a part of the irradiation area was masked by the beam member, and the density of the charged particles becomes uneven within the irradiation area. If the distance between the stencil mask and the semiconductor substrate is increased, a scattering phenomenon of the charged particles may be used to essentially eliminate this shadowing effect by the beam member. However, in this case, the scattering phenomenon causes the charged particles to be introduced over a wide area, and it is no longer possible to accurately control the irradiation area to the predetermined pattern at the surface of the semiconductor substrate. With semiconductor devices, it is often desirable that the density of the charged particles has a uniform distribution over the irradiation area. It is often also desirable that a very small pattern of the irradiation area is formed at the surface of the semiconductor substrate. In this case, the conventional stencil mask cannot be utilized. Furthermore, when this type of stencil mask having beam members was utilized and the charged particles were introduced, the temperature of the stencil mask is increased because the charged particles collide with the stencil mask, and as a result, deformation of the stencil mask frequently occurred. Deformation of the stencil mask causes the problems that the irradiation area of the charged particles would shift, or that the dimensional accuracy of the irradiation area would be worsened. If a very small pattern of the irradiation area is desired, a very thin stencil mask must be used due to the limitation as to the aspect ratio of etching the penetrating hole. However, collision of the charged particles causes the temperature of the thin stencil mask to increase greatly, and consequently there is an increase in the amount of deformation. Further, a thin stencil mask has weak mechanical rigidity and therefore, in order to suppress the deformation, the width of each of the beam members must be increased. When the width of the beam member is increased, the density of the charged particles within the irradiation area readily becomes uneven. With the conventional stencil mask, it is not possible to form a very small irradiation area while adjusting the density of the charged particles to have a uniform distribution. The present invention teaches a stencil mask for limiting an irradiation area of charged particles on a surface of a substrate to a predetermined shape. The stencil mask of the present invention comprises a first layer disposed at a side of the stencil mask facing the substrate to which the charged particles are introduced, and a second layer disposed at a side of the stencil mask to which the charged particles are irradiated. At least one first penetrating hole having a shape corresponding to the intended irradiation area is formed in the first layer. A plurality of second penetrating holes is formed in the second layer within an area encompassing the intended irradiation area. The plurality of the second penetrating holes is widely distributed within the area. In the stencil mask of the present invention, when viewed along the traveling path of the charged particles, a portion between adjacent the second penetrating holes of the second layer cross across the first penetrating hole of the first layer. Two portions of the first layer separated by the first penetrating hole are connected by the portion of the second layer separating the adjacent second penetrating holes. Two portions of the first layer separated by the first penetrating hole are connected at a height different from the first layer. The substrate to which the charged particles are irradiated is typically a semiconductor substrate. However, the stencil mask of the present invention can also be utilized for irradiating the charged particles into a material other than a semiconductor substrate. The irradiation area means a portion of the surface of the substrate where the charged particles are irradiated. The term irradiation area usually means a pattern in which the charged particles are introduced. The charged particles that have been irradiated to the substrate surface are usually introduced into the surface layer of the substrate. However, the charged particles may pass through the substrate. Therefore the irradiation area is not necessarily equal to the pattern where the charged particles stay. Furthermore, the charged particles that have been irradiated to the substrate surface may penetrate the substance for a certain distance and stay at the certain depth. The pattern where the charged particles stay at the depth is not necessarily equal to the irradiation area at the surface of the substrate, because the charged particle scatter while penetrating the distance. The irradiation area is not necessarily equal to the area where the charged particles stay. The first penetrating hole formed in the first layer of the stencil mask has a shape substantially corresponding to the irradiation area which is not necessarily equal to the pattern where the charged particles stay. The stencil mask of the present invention may comprise other layers than the first layer and the second layer. The first layer and the second layer may be formed integrally. Alternatively, the first layer and the second layer may be formed separately. The first penetrating hole is formed in the first layer of the stencil mask in a shape substantially corresponding to the predetermined shape of the irradiation area. However, the shape of the first penetrating hole is not restricted to being entirely identical with the irradiation area. The shape of the first penetrating hole may be designed taking into account a spread of the charged particles caused by the scattering phenomenon of the charged particles that have passed through the first penetrating hole. Further, the charged particles may be irradiated onto the surface of the substrate by passing through the first penetrating hole from an oblique direction. The shape of the first penetrating hole may be designed taking into account this type of method of use. In this type of case, the shape of the first penetrating hole is not strictly identical with the shape of the area where the charged particles are irradiated. The shape of the first penetrating hole is designed so that, after various phenomenons have proceeded, the charged particles can be irradiated to the intended irradiation area on the substrate surface. In the present specification, this is referred to as ‘the shape of the first penetrating hole corresponds to the predetermined shape of the irradiation area.’ The plurality of the second penetrating holes is formed in the second layer. The charged particles that are being irradiated are led to the first penetrating hole after passing through the second penetrating holes. The plurality of second penetrating holes is distributed and forms a distributing area. The distribution area may be the same shape as of the first penetrating hole, however, it is preferred that the distribution area is slightly larger than the first penetrating hole and encompasses the first penetrating hole. The distribution area may be much larger that the first penetrating hole, and second penetrating holes may be distributed over the entire area of the second layer. There are portions present between adjacent second penetrating holes in the distributing area. In the stencil mask of the present invention, these portions extending between adjacent second penetrating holes allow the first penetrating hole to have a variety of shapes. That is, when viewed along the traveling path of the charged particles, the portions extending between adjacent second penetrating holes and separating adjacent second holes pass across the first penetrating hole. As a result, the portions between adjacent second penetrating holes can increase mechanical rigidity near side walls of the first layer, these side walls defining the first penetrating hole. The portions between the second penetrating holes allow a stencil mask to be configured in which deformation does not readily occur. Furthermore, the stencil mask of the present invention can effectively utilize the scattering phenomenon of the charged particles. Since the charged particles are electrically charged, there is repulsive force operating between each of the charged particles. The charged particles consequently scatter while proceeding along their traveling path. In the stencil mask of the present invention, a plurality of second penetrating holes is formed in the second layer, and the portions extending between adjacent second penetrating holes pass above the first penetrating hole. The charged particles that have passed through the plurality of second penetrating holes scatter within the first penetrating hole while passing through the first penetrating hole. The charged particles are therefore able to proceed, within the first penetrating hole, toward a space below the portion of the second layer separating adjacent second penetrating holes. The charged particles that have passed through the second penetrating holes and the first penetrating hole can therefore be irradiated in the pattern that crossly corresponds to the shape of the first penetrating hole. The irradiation pattern of the charged particles that have passed through the second penetrating holes and the first penetrating hole is hardly affected by the shadowing effect created by the portion separating adjacent second penetrating holes. With the stencil mask of the present invention, even though the portion separating adjacent second penetrating holes is present, it is possible to eliminate the shadowing effect by that portion. In order to eliminate the shadowing effect by the scattering phenomenon of the charged particles, a certain distance is required between the stencil mask and the surface of the substrate. In the conventional stencil mask, a long distance is required between the stencil mask and the surface in order to eliminate the shadowing effect. In the present stencil mask, the distance between the stencil mask and the substrate can be decreased because the charged particles are scattered while passing through the first penetrating hole. The thickness of the first layer may be used to promote the scattering. When the distance between the stencil mask and the substrate is decreased, the charged particles that have passed through the second penetrating holes and the first penetrating hole do not spread over a wide area, and can be irradiated on the surface of the substrate in a shape that closely reflects the shape of the first penetrating hole. When the stencil mask of the present invention is utilized, the charged particles can be irradiated within the irradiation area that is very similar to the shape of the first penetrating hole. Further, there are no problems in increasing thickness of the second layer of the present invention. When the second layer is thick, the thick second layer gives strong mechanical rigidity to the first layer; therefore, the first layer can be made thinner. When the first layer is thinner, a very small first penetrating hole can be formed in the first layer even if the aspect ratio of the etching for forming the first penetrating hole is limited. In the stencil mask of the present invention, the first layer has the role of limiting the irradiation area, and the second layer has the role of increasing the mechanical rigidity of the stencil mask. Each of the first layer and the second layer has its own role. Consequently, even if the second layer is thick, it is possible to form a first penetrating hole with a desired shape in the first layer. Increasing the thickness of the second layer allows the mechanical rigidity of the stencil mask to be increased. Further, increasing the thickness of the second layer allows the heat capacity of the stencil mask to be increased. When the heat capacity of the stencil mask is increased, it is possible to suppress an excessive increase in the temperature of the stencil mask when the stencil mask is exposed to the charged particles. The stencil mask of the present invention is therefore able to suppress deformation caused by an increase in temperature. With the stencil mask of the present invention, it is preferred that the distributing area of the second penetrating holes is larger than the shape of the first penetrating hole when viewed along the traveling path of the charged particles. The traveling path of the charged particles does not mean the directions in which the charged particles are caused to travel by the scattering phenomenon, but refers to a direction that links an irradiation source of the charged particles to the surface of the substrate. With the aforementioned stencil mask, a large amount of charged particles can be guided into the first penetrating hole of the first layer through the second penetrating holes. With the stencil mask of the present invention, it is preferred that the first layer and the second layer are made of semiconductor material. Further, it is preferred that the first layer and the second layer are in contact with each other. A stencil mask that utilizes a stack of semiconductors can therefore be manufactured easily. The stencil mask of the present invention is particularly useful in the case where the first penetrating hole is shaped as a closed loop, and an island portion is included within the closed loop. Even though the first penetrating hole forms the loop, the portions separating the second penetrating holes can connect the island portion surrounded by the closed loop and the part of the first layer outside the closed loop. With the stencil mask of the present invention, therefore, it is possible to prevent the island portion inside the first penetrating hole from separating from the part of the first layer outside the first penetrating hole. Since the stencil mask of the present invention can utilize the scattering phenomenon of the charged particles, it is possible for the charged particles to arrive at the surface of the substrate positioned below the portions separating adjacent second penetrating holes. When the stencil mask of the present invention is utilized, a looped irradiation area can be formed by performing the irradiation of the charged particles a single time. With the stencil mask of the present invention, it is preferred that each of the second penetrating holes has a convex polygonal shape. In the present invention, each of the second penetrating holes is formed into a convex polygonal shape by adjusting the shape and positional relationship of the portion separating the adjacent second penetrating holes. When the second penetrating hole has a convex polygonal shape, there are no longer positions where stress readily accumulates near the side walls of the second layer that demarcate the second penetrating hole, and deformation of the second layer is therefore prevented extremely well. With the stencil mask of the present invention, it is preferred that distance between adjacent second holes is long at the side of the second layer to which the charged particles are irradiated, and short at the side of the second layer facing towards the first layer. In other words, with the stencil mask of the present invention, it is preferred that the width of the portion separating adjacent second penetrating holes becomes shorter along the traveling path of the charged particles. The above feature is obtained when side walls of the portion extending between adjacent second penetrating holes are inclined with respect to the traveling path of the charged particles. With the aforementioned stencil mask, the portion between adjacent second penetrating holes has a longer width at the side away from the substrate, and has a shorter width at the side by the substrate. Since the portion between adjacent second penetrating holes has a longer width at the side away from the substrate, these portion is able to firmly join portions of the second layer that are separated by the second penetrating holes. Deformation near the side walls of the second penetrating holes can therefore be suppressed. Further, since the portion between adjacent second penetrating holes has a shorter width at the side by the substrate, a large amount of the charged particles that have passed through the second penetrating holes are able to arrive at the surface of the substrate at the area below the portion between the second penetrating holes. The effects on the masking pattern by the portions between the second penetrating holes are thus reduced. A device for irradiating the charged particles adopting the stencil mask of the present invention is extremely useful. The device for irradiating the charged particles of the present invention comprises a charged particle generator, a mass analyzer for selecting predetermined charged particles from the charged particles generated by the generator, an accelerator for accelerating the selected charged particles, an irradiating chamber where a substrate is to be accepted, and the stencil mask of the present invention disposed between the accelerator and the substrate which is accepted within the irradiating chamber. In conventional devices equipped with stencil masks, deformation of the stencil mask caused by an increase in temperature, etc. was a serious problem. The conventional devices for irradiating the charged particles were therefore utilized within a range in which the stencil mask did not deform, and consequently the devices for irradiating the charged particles could not work efficiently. In the stencil mask of the present invention, deformation of the stencil mask caused by an increase in temperature is suppressed. As a result, by providing the stencil mask of the present invention, an extremely efficient device for irradiating the charged particles can be realized. It is preferred that the stencil mask of the present invention is disposed above the substrate, and that the charged particles are irradiated through the stencil mask toward the surface of the substrate. When the stencil mask of the present invention is utilized, it is possible to form a variety of irradiation areas on the surface of the substrate. Furthermore, because it is possible to suppress an increase in temperature of the stencil mask, the output of the charged particles generator can be increased, and a large amount of charged particles can be irradiated to the surface of the substrate. Further, when the stencil mask of the present invention is utilized, a useful semiconductor device can be obtained. That is, in a method of manufacturing the semiconductor device, the stencil mask of the present invention is disposed above a semiconductor wafer, and the charged particles are irradiated through the stencil mask to the surface of the semiconductor wafer. It is thus possible to form a variety of irradiation areas on the surface of the semiconductor wafer. Furthermore, because an increase in temperature of the stencil mask is suppressed, the output of the generator of the charged particles can be increased, and a large amount of charged particles can be irradiated to the semiconductor wafer. By using the manufacturing method of the present invention, it is possible to obtain a semiconductor device that has a variety of very small semiconductor regions. The present invention also presents a method of manufacturing the stencil mask. The manufacturing method of the present invention comprises: forming a plurality of second penetrating holes distributed on a semiconductor lower layer; filling up the plurality of second penetrating holes with a sacrifice material; forming a semiconductor upper layer continuously on the surface of the semiconductor lower layer; forming a first penetrating hole in the semiconductor upper layer, the first penetrating hole communicating with the plurality of second penetrating holes and having a shape corresponding to the predetermined shape; and selectively removing the sacrifice material by using an etching material which etches the sacrifice material but does not etch the semiconductor lower layer and semiconductor upper layer. With this manufacturing method, the second layer of the stencil mask is formed using the semiconductor lower layer, and the first layer of the stencil mask is formed using the semiconductor upper layer. The stencil mask of the present invention can thus be manufactured easily. When the stencil mask of the present invention is utilized, deformation of the stencil mask is suppressed when the charged particles are irradiated. Furthermore, when the stencil mask of the present invention is utilized, a variety of very small irradiation area can be formed on the surface of the substrate. Further, with the method of manufacturing the semiconductor device of the present invention, it is possible to obtain a useful semiconductor device. Moreover, with the method of manufacturing the stencil mask of the present invention, it is possible to efficiently manufacture the stencil mask for the semiconductor device. Description of the Preferred Features The preferred features of the present invention will be described below. (First Preferred Feature) The stencil mask comprises a semiconductor stack in which a first semiconductor layer and a second semiconductor layer are stacked. The first semiconductor layer is disposed at a side of the stencil mask which faces toward a substrate, and the second semiconductor layer is disposed at a side of the stencil mask to which charged particles are irradiated. A first penetrating hole is formed in the first semiconductor layer in a shape corresponding to an area where the substrate surface is exposed to the charged particles. A plurality of second penetrating holes is formed in the second semiconductor layer, these second penetrating holes communicating with the first penetrating hole. The second penetrating holes are distributed, and the plurality of second penetrating holes forms a distributing area. The distributing area is wider than the first penetrating hole and encompasses the first penetrating hole. Beam members separating adjacent second penetrating holes extend above the first penetrating hole. The beam member connects portions of the first layer separated by the first penetrating hole. The semiconductor stack may further have a supplementary semiconductor layer that is stacked on the second semiconductor layer. In this case, a large penetrating hole is formed in the supplementary semiconductor layer, and this penetrating hole communicate with the first penetrating hole and the second penetrating holes. Beam members may also be formed at the supplementary semiconductor layer. (Second Preferred Feature) The second semiconductor layer is separated by the distributing area of the second penetrating holes into an outer second semiconductor layer and an inner second semiconductor layer. The beam members that connect the outer second semiconductor layer and the inner second semiconductor layer pass across the distributing area of the second penetrating holes. The beam members are not formed within the first penetrating hole. As a result, the traveling path of the charged particles that have passed through adjacent second penetrating holes can join within the first penetrating hole. The thickness of the first penetrating hole can be adjusted to eliminate a shadow pattern caused by the beam member extending between adjacent second penetrating holes. (Third Preferred Feature) The width of the beam member separating adjacent second penetrating holes is wider at a non-substrate side, and is thinner at a substrate side. When the beam member has a thinner width at the substrate side, the charged particles that have passed through adjacent second penetrating holes join while traveling the short distance after passing through the second penetrating holes. A large number the charged particles can arrive at the shadow area below the beam member, even if the first layer is thin. (Fourth Preferred Feature) The beam members separating the second penetrating holes are remnants from when the plurality of second penetrating holes was formed in a distributed manner in the semiconductor layer. An embodiment of a stencil mask will be described below with reference to figures. A stencil mask of the present embodiment is used for limiting an irradiation area of ionized atoms to a predetermined shape on the surface of the semiconductor substrate and locally introducing ionized atoms into the semiconductor substrate. The area where the ionized atoms are introduced and the area where the ionized atoms are not introduced are controlled by the stencil mask. When the stencil mask of the present embodiment is utilized, it is possible to form the ion introducing area in a loop shape at the surface of the semiconductor substrate. Moreover, the ion introducing area is not restricted to being formed in a loop shape, but can be formed in various shapes by modifying the pattern of penetrating holes formed in the stencil mask. A simple description of the figures will be given first. FIG. 1 is a longitudinal cross-sectional view schematically showing the basic configuration of a stencil mask 10. Since FIG. 1 schematically shows the basic concept of the stencil mask 10 of the present embodiment, it does not conform with the configuration of the embodiment shown in FIG. 2. The stencil mask 10 comprises a flat semiconductor stack 40 in which a first semiconductor layer 20 (an example of a first layer) and a second semiconductor layer 30 (an example of a second layer) are stacked. Although this will be described in detail later, a plurality of patterns are formed in the semiconductor stack 40, these patterns corresponding with a plurality of ion introducing areas in a surface portion of a semiconductor substrate. FIG. 2 is an enlarged perspective view of essential parts of the semiconductor stack 40 of the stencil mask 10 of the present embodiment. The configuration shown in FIG. 2 shows one of the pluralities of patterns formed in the semiconductor stack 40. The pattern shown in FIG. 2 corresponds to the irradiation area that forms a loop. A plurality of patterns the same as the pattern shown in FIG. 2 may be formed in the semiconductor stack 40, or patterns differing from the pattern shown in FIG. 2 may be formed therein. With the stencil mask 10, the plurality of ion introducing areas can be formed at the surface portion of a semiconductor substrate 72 by performing irradiation a single time. FIG. 3 is an enlarged perspective view of essential parts of the first semiconductor layer 20 in the semiconductor stack 40. FIG. 4 is an enlarged perspective view of essential parts of the second semiconductor layer 30 in the semiconductor stack 40. The first semiconductor layer 20 and the second semiconductor layer 30 have been shown separately in FIG. 3 and FIG. 4 for the purpose of clarity. FIG. 5 is a cross-sectional view along the line V-V of FIG. 2. FIG. 6 is a cross-sectional view along the line VI-VI of FIG. 2. FIG. 7 is a cross-sectional view along the line VII-VII of FIG. 2. When the stencil mask 10 is utilized and the ionized atoms are irradiated, the ionized atoms are irradiated from the top side of the page in FIGS. 1˜7. With the stencil mask 10, the first semiconductor layer 20 is disposed at a side of the stencil mask 10 that faces toward the semiconductor substrate 72, and the second semiconductor layer 30 is disposed at a side of the stencil mask 10 to which the charged particles are irradiated. An ion implantation device 100 (an example of a charged particle irradiation device) in which the stencil mask 10 is disposed will now be described with reference to FIG. 8. The ion implantation device 100 comprises an ion source 2 (an example of a charged particle generator) for generating ionized atoms, a mass analyzer 3 for selecting required ionized atoms from among the ionized atoms that have been generated, an accelerator 4 that accelerates the selected ionized atoms, and an irradiation chamber 6 in which the semiconductor substrate 72 is disposed. The stencil mask 10 is disposed above (at an anterior side of) the semiconductor substrate 72. The stencil mask 10 is disposed between the accelerator 4 and the semiconductor substrate 72. The ionized atoms accelerated by the accelerator 4 are swept out by a scanner 5, and are irradiated in an approximately planar manner toward the stencil mask 10. Ionized atoms that have passed through the penetrating holes or windows formed in the stencil mask 10 are irradiated to a surface of the semiconductor substrate 72, and are introduced into a surface portion of the semiconductor substrate 72. Viewed from the stencil mask 10, the side with the accelerator 4 is termed the upper side or the anterior side, and in the present specification the side with the semiconductor substrate 72 is termed the lower side or posterior side. Next, the figures will be described in detail. As shown in FIG. 1, the stencil mask 10 comprises the semiconductor stack 40 in which the first semiconductor layer 20 and the second semiconductor layer 30 are stacked. A surrounding support layer 62 is formed in a loop along a peripheral part of the semiconductor stack 40, and is separated from the semiconductor stack 40 by a silicon oxide layer 52. The surrounding support layer 62 is considerably thicker than the semiconductor stack 40. The silicon oxide layer 52 and the surrounding support layer 62 increase the mechanical rigidity of the semiconductor stack 40, and prevent damage to the stencil mask 10 while the stencil mask 10 is being manufactured. Further, when the stencil mask 10 is installed above (to the anterior of) the semiconductor substrate 72 (see FIG. 8), the surrounding support layer 62 is also utilized as a contacting part for other installing devices. A cooling device (not shown) may be formed on the surrounding support layer 62. In this case, heat from the semiconductor stack 40 can escape to the exterior via the silicon oxide layer 52 and the surrounding support layer 62. A first penetrating hole 24 is formed in the first semiconductor layer 20 in a shape corresponding to the ion introducing area of the semiconductor substrate 72. A plurality of second penetrating holes 34 is widely distributed in an area of the second semiconductor layer 30 that corresponds to the irradiation area of the semiconductor substrate 72. The first penetrating hole 24 and the second penetrating holes 34 communicate, and pass from one face of the semiconductor stack 40 to the other face thereof. In order to show clearly that the first semiconductor layer 20 is being supported by the second semiconductor layer 30, FIG. 1 shows a cross-section in which some of the first penetrating hole 24 and the second penetrating holes 34 do not communicate. Although some of the first penetrating hole 24 and the second penetrating holes 34 do not communicate in the cross-section in FIG. 1, they do communicate in the other longitudinal cross-sections of the semiconductor stack 40. The ionized atoms can thus reach the surface of the semiconductor substrate 72 by passing through the second penetrating holes 34 and the first penetrating holes 24. It should be noted here that FIG. 1 shows the stencil mask 10 schematically in order to aid understanding of the basic configuration of the stencil mask 10, and differs greatly from the actual configuration. FIG. 2 shows one of the pluralities of patterns formed in the semiconductor stack 40. In FIG. 2, part of the second semiconductor layer 30 has been cut away to make the figure clearer, and a part of the first penetrating hole 24 of the first semiconductor layer 20 has been exposed. The first semiconductor layer 20 of the stencil mask 10 is disposed above (to the anterior of) the surface of the semiconductor substrate 72 and is separated therefrom by a distance Dg. Further, as will be described below, the stencil mask 10 has the advantage that this distance Dg can be reduced. As a result, when the stencil mask 10 is utilized, it is possible to control a scattering phenomenon of the ionized atoms after these ionized atoms have passed through the first penetrating hole 24, and it is possible to form a very small ion introducing area on the surface portion of the semiconductor substrate 72. In order to aid comprehension of the first semiconductor layer 20 and the second semiconductor layer 30 that compose of the semiconductor stack 40, the first semiconductor layer 20 and the second semiconductor layer 30 will be described with reference to FIG. 3 and FIG. 4 respectively. As shown in FIG. 3, the first penetrating hole 24 is formed in a rectangular loop in the first semiconductor layer 20. The first penetrating hole 24 passes through the first semiconductor layer 20, and the first semiconductor layer 20 is thus separated by the first penetrating hole 24 into an outer first semiconductor layer 23 and an inner first semiconductor layer 26. Unless there is something to connect the outer first semiconductor layer 23 and the inner first semiconductor layer 26, the two will become separated. The first penetrating hole 24 is provided in a shape that corresponds to the irradiation area of the semiconductor substrate 72. In this example, the irradiation area has a pattern in which it forms a loop on the surface of the semiconductor substrate 72. The first penetrating hole 24 therefore also forms a loop that corresponds to the loop-shape irradiation area of the semiconductor substrate 72. A thickness T20 of the first semiconductor layer 20 can be adjusted in accordance with the pattern of the irradiation area to be made on the semiconductor substrate 72. As will be described below, mechanical rigidity of the first semiconductor layer 20 is increased by the second semiconductor layer 30, and consequently the thickness T20 of the first semiconductor layer 20 can be reduced. If the thickness T20 of the first semiconductor layer 20 is reduced, a very small first penetrating hole 24 can be formed by etching in the first semiconductor layer 20 even if the aspect ratio of the etching is limited. The thickness T20 of the first semiconductor layer 20 of the present embodiment is approximately 20 μm. A hole width W20 of the first penetrating hole 24 is approximately 1 μm. The aspect ratio of the first penetrating hole 24 is approximately 20. With this aspect ratio, the RIE (Reactive Ion Etching) method or the like can be utilized to etch the first penetrating hole 24. Furthermore, utilizing the thin first semiconductor layer 20 is also required for other reasons than the limitations of the aspect ratio during etching. For example, if a thick first semiconductor layer 20 is utilized, a part of the ionized atoms that enter the first penetrating hole 24 are introduced into side walls of the first penetrating hole 24, and the amount of ionized atoms that pass through the first penetrating hole 24 is therefore reduced. If the thin first semiconductor layer 20 is utilized, the phenomenon is controlled wherein ionized atoms are introduced to the side walls of the first penetrating hole 24, and the amount of ionized atoms that pass through the first penetrating hole 24 can therefore be kept large. That is, it is preferred that the thickness T20 of the first semiconductor layer 20 is thin not just in order to make the first penetrating hole 24 small, but also to increase the amount of ionized atoms that pass through the first penetrating hole 24. As shown in FIG. 4, the plurality of second penetrating holes 34 is widely distributed in an area 34c (hereafter termed distributing area 34c) that is enclosed within the broken line 34a and the broken line 34b. The distributing area 34c corresponds to the shape of the irradiation area on the surface of the semiconductor substrate 72. The second penetrating holes 34 communicate with the first penetrating hole 24. The distributing area 34c is formed as an approximate loop extending along the first penetrating hole 24 that forms a loop in the first semiconductor layer 20. The distributing area 34c forms a rectangular loop in the second semiconductor layer 30, and has four comer penetrating holes 35. Devices to control deformation are provided in the comer penetrating holes 35. This will be described in detail below. The second semiconductor layer 30 is separated by the distributing area 34c into an outer second semiconductor layer 31 and an inner second semiconductor layer 32. Beam members 33 are present between the second penetrating holes 34 in the distributing area 34c. The beam members 33 connect the outer second semiconductor layer 31 and the inner second semiconductor layer 32. Viewed along the traveling path of the ionized atoms, the distributing area 34c is larger than the shape of the first penetrating hole 24. Specifically, a hole width W30 of the second penetrating holes 34 is larger than the hole width W20 of the first penetrating hole 24. This hole width W30 refers to the distance between a side wall and an opposing side wall in the semiconductor layer 30, these side walls demarcating the penetrating holes 34. The distance between a side wall of a beam member 33 and an opposite side wall of the beam member 33 is not included in the hole width W30. The second penetrating holes 34 introduce the ionized atoms toward the first penetrating hole 24. As a result, when the distributing area 34c is larger than the shape of the first penetrating hole 24, a large amount of the ionized atoms can be guided toward the first penetrating hole 24. As shown in FIG. 6, the hole width W30 of the second penetrating holes 34 is greater than the hole width W20 of the first penetrating hole 24. A step 29 is formed between the first penetrating hole 24 and the second penetrating holes 34. When the hole width W30 of the second penetrating holes 34 is greater than the hole width W20 of the first penetrating hole 24, masking caused by the second semiconductor layer 30 does not occur (the beam members 33 are an exception: this will be described below). Many of the ionized atoms that have passed through the second penetrating holes 34 are guided toward the first penetrating hole 24. There is no particular restriction as to a thickness T30 of the second semiconductor layer 30. The thickness T30 of the second semiconductor layer 30 can be adjusted freely so as to obtain a desired mechanical strength, heat capacity, etc. As shown in FIG.4, the plurality of beam members 33 is formed in the distributing area 34c. The beam members 33 pass across the distributing area 34c that separates the outer second semiconductor layer 31 and the inner second semiconductor layer 32. The beam members 33 are formed at constant intervals along the distributing area 34c that forms a loop. Viewed along the traveling path of the ionized atoms, the beam members 33 bridges the inner first semiconductor layer 26 and outer first semiconductor layer 23 that are separated by the first penetrating hole 24. As will be described later, the stencil mask 10 utilizes the scattering phenomenon of the ionized atoms. Due to the scattering phenomenon, the ionized atoms can be led into the surface of the substrate 72 at areas below the beam members 33, even though these beam members 33 cover portions of the first penetrating hole 24. With the stencil mask 10, the ion introducing area can be formed by performing irradiation a single time rather than a plurality of times. The inner first semiconductor layer 26 and the inner second semiconductor layer 32 are fixed. The outer first semiconductor layer 23 and the outer second semiconductor layer 31 are fixed. The inner second semiconductor layer 32 and the outer second semiconductor layer 31 are connected by the beam members 33. As a result, the inner first semiconductor layer 26 is supported by the outer first semiconductor layer 23 via the outer second semiconductor layer 31, the beam members 33 and the inner second semiconductor layer 32. The inner first semiconductor layer 26 is thus prevented from becoming detached even though the first penetrating hole 24 forms a loop. The area near the side walls of the second semiconductor layer 30 where the second penetrating holes 34 are demarcated is strengthened by providing the beam members 33, and deformation of this part can therefore be controlled. Since the beam members 33 are formed at constant intervals, the entirety of the side walls of the second penetrating holes 34 can be prevented from deforming. Further, since the first semiconductor layer 20 and the second semiconductor layer 30 are stacked, the area near the side walls defining the first penetrating hole 24 is also strengthened by the beam members 33 and the second semiconductor layer 30. The deformation of the area near the side walls of the first penetrating hole 24 can therefore also be suppressed. In the stencil mask 10, deformation of the area near the side walls of both the first penetrating hole 24 and the second penetrating holes 34 is controlled by providing the beam members 33. It is thus possible to prevent problems wherein the range of the ion introducing area shifts, or wherein the dimensions of the ion introducing area change. By utilizing the technique of the stencil mask 10, deformation of the first semiconductor layer 20 can be controlled. It is possible to form a variety of patterns of the first penetrating hole 24 or a plurality of the first penetrating holes in the first semiconductor layer 20. By utilizing the technique of the stencil mask 10, a variety of very small first penetrating holes 24 can be formed, and a variety of very small irradiation areas can be formed. The stencil mask 10 is formed utilizing the semiconductor stack 40 in which the first semiconductor layer 20 and the second semiconductor layer 30 are stacked. The total thickness of the first semiconductor layer 20 and the second semiconductor layer 30 together can be increased by stacking the first semiconductor layer 20 and the second semiconductor layer 30. It is thus possible to increase the total thickness of the first semiconductor layer 20 and the second semiconductor layer 30 while the thickness T20 of the first semiconductor layer 20 remains thin. The total thickness of the first semiconductor layer 20 and the second semiconductor layer 30 can thus be increased while the thickness of the first second layer 20 is being restricted by the limit of the aspect ratio. That is, it is possible to increase the total thickness of the first semiconductor layer 20 and the second semiconductor layer 30 while making it possible to form very small irradiation areas due to the very small first penetrating holes 24. When the total thickness of the first semiconductor layer 20 and the second semiconductor layer 30 is increased, the heat capacity of the semiconductor stack 40 in which the first semiconductor layer 20 and the second semiconductor layer 30 are combined is greater than when the first semiconductor layer 20 is isolated. When the heat capacity is increased, the temperature of the semiconductor stack 40 can be prevented from rising excessively when the ionized atoms are introduced even though the ionized atoms collide with the semiconductor stack 40. Deformation of the semiconductor stack 40 can thus be suppressed. The characteristics of the stencil mask 10 can be pinpointed as follows. With the stencil mask 10, the mechanical rigidity and heat capacity of the first semiconductor layer 20 can be improved by utilizing the second semiconductor layer 30. A thin first semiconductor layer 20 can therefore be utilized. When the first semiconductor layer 20 is thinner, very small irradiation areas can be formed. By stacking the second semiconductor layer 30 on the first semiconductor layer 20, the stencil mask 10 is successful in forming very small irradiation areas. When the technique of the stencil mask 10 is utilized, a variety of very small irradiation areas can be formed on the surface of the semiconductor substrate 72, and deformation of the first semiconductor layer 20 and the second semiconductor layer 30 can be controlled extremely well. Next, the advantage will be described, with reference to figures, that the stencil mask 10 can be used with a short distance (see Dg of FIGS. 2, 5, 6, 7, and 8) between the stencil mask 10 and the semiconductor substrate 72. FIG. 9 shows a plan view of essential parts of a layer of a conventional stencil mask. The vicinity of a comer penetrating hole 135 has been enlarged in FIG. 9. In the conventional configuration in FIG. 9, penetrating holes 134 and beam members 133 are both formed in one semiconductor layer. FIG. 10 shows the range (the range shown by hatching) of an ion irradiation area 182 obtained when the stencil mask with conventional configuration was utilized. The penetrating holes 134 and 135 corresponding with the ion irradiation area 182 have been overlapped and are shown by broken lines. If the ion irradiation area 182 is formed using the scattering phenomenon of ionized atoms, the ionized atoms must pass below the beam members 133. It is therefore desirable that there is a greater distance between a semiconductor substrate and a stencil mask. When the two are separated by a greater distance, the ionized atoms can scatter in a horizontal direction by a distance corresponding to the width of the beam members 133, and the ion irradiation g area 182 can therefore also be formed below the beam members 133. However, when there is a great distance between the semiconductor substrate and the stencil mask, the scattering phenomenon of the ionized atoms causes the problem that the ion irradiation area 182 is formed across a wide range. As shown in FIG. 10, with the conventional stencil mask, the ion irradiation area 182 is formed widely across a range that extends towards the periphery by the distance L100 from the pattern of the penetrating holes 134 and 135. It is therefore difficult to make the ion irradiation area 182 very small when the conventional stencil mask is used. FIG. 11 shows a plan view of essential parts of the semiconductor stack 40 of the stencil mask 10 of the present embodiment. This configuration of the stencil mask 10 allows the scattering phenomenon of the ionized atoms to be utilized effectively. In the stencil mask 10, the beam members 33 are formed in the second layer 30, but not formed in the first penetrating hole 24. The ionized atoms that pass through the second penetrating holes 34 consequently scatter within the first penetrating hole 24 while they pass through the first penetrating hole 24. Consequently the ionized atoms enter spaces below the beam members 33 of the second layer 30 while they pass through the first penetrating hole 24. The ionized atoms that have passed through the first penetrating holes 24 can therefore be irradiated outwards from the first penetrating hole 24 according to the pattern of the first penetrating hole 24. Shadowing effect by the beam members 33 of the second layer 30 appear only to a small extent in the irradiation pattern of the ionized atoms that have passed through the first penetrating holes 24. In the stencil mask 10, the beam members 33 are formed in the second layer 30, and are not formed in the first layer 20. As a result, the masking effect caused by the beam members 33 can be eliminated by adjusting the thickness of the first semiconductor layer 20. The distance Dg between the first semiconductor layer 20 and the semiconductor substrate 72 can therefore be reduced. As shown in FIG. 12, since the distance Dg between the first semiconductor layer 20 and the semiconductor substrate 72 can be reduced, it is possible to control the scattering phenomenon of the ionized atoms that have passed through the first penetrating hole 24, and consequently an ion irradiation area 82 that is obtained has a narrow range. When the stencil mask 10 is utilized, the ion irradiation area 82 is formed that extends toward the periphery only by the distance L10 from the pattern of the first penetrating hole 24. It is clear from a comparison of L100 of FIG. 10 and L10 of FIG. 12 that the width of the ion irradiation area 82 extending towards the periphery can be kept small, since the distance Dg can be reduced when the stencil mask 10 is utilized. As a result, the ion irradiation area 82 can be made extremely small when the stencil mask 10 is utilized. Next, the density distribution of the ionized atoms that have been introduced into the ion irradiation area will be described with reference to FIGS. 13˜19. The longitudinal cross-sections of FIG. 13, FIG. 18 and FIG. 19 correspond to the longitudinal cross-section shown in FIG. 5. FIG. 13 is an example wherein side walls of each beam member 33 are parallel to the traveling path of the ionized atoms. That is, this is equivalent to the embodiment described above. The solid line 74a shown within the semiconductor substrate 72 shows the density distribution of the ionized atoms that have been introduced into the surface of the semiconductor substrate 72. The density distribution of the ionized atoms is strongly affected by the following. A desired density distribution can be obtained by adjusting the following factors appropriately. (1) A distance D33 between a side wall 33a of one beam member 33 and a side wall 33a of an adjacent beam member 33. (2) A width W33 of the beam member 33. (3) The distance Dg between the first semiconductor layer 20 and the substrate 72. (4) The thickness T20 of the first semiconductor layer 20. (5) A scattering angle a σ[deg] of the beam (the ionized atoms). FIG. 14 shows a relation between coefficient of variation and the distance D33. The coefficient of variation shows the maximum unevenness of the density of the ionized atoms that have been introduced into the substrate 72. D1 in FIG. 13 shows an average density of the ionized atoms that have been introduced into the substrate 72. D2 in FIG. 13 shows a minimum density of the ionized atoms that have been introduced into the substrate 72. D2 is smaller than D1 due to shadowing effect by the beam members 33. The coefficient of variation is calculated by the equation of (D1−D2)/D1×100%. As is clear from FIG. 14, increasing the distance D33 causes a decrease in the coefficient of variation. A large distance D33 is desirable. FIG. 15 shows the relation between the coefficient of variation and the width W33. As is clear from FIG. 15, decreasing the width W33 causes a decrease in the coefficient of variation. A small width W33 is desirable. FIG. 16 shows the relation between the coefficient of variation and the distance Dg. As is clear from FIG. 16, increasing the distance Dg causes a decrease in the coefficient of variation. However, as described above, when the distance Dg is increased, the ion introducing area is formed across a wider range. This should be avoided if a very small ion introducing area is desired. FIG. 17 shows a relation between the coefficient of variation and the scattering angle σ(deg) of the beam (the ionized atoms). As is clear from FIG. 17, increasing the scattering angle σ causes a decrease in the coefficient of variation. However, if the scattering angle σ is increased, the ion introducing area is formed across a wider range. This should be avoided if a very small ion introducing area is desired. A desired density distribution of the ion introducing area can be obtained by adjusting the shape of beam members 33 appropriately in accordance with the above factors (1)˜(5). The coefficient of variation of the density distribution of the ionized atoms when the factors (1)˜(5) are combined can be represented by a numerical formula (I) below. the ⁢ ⁢ coefficient ⁢ ⁢ of ⁢ ⁢ variation = exp ⁡ ( 5.1 - 0.084 × D ⁢ ⁢ 33 + 3.1 × W ⁢ ⁢ 33 - 0.079 × Dg - 1.2 × σ - 0.11 × D ⁢ ⁢ 33 × W ⁢ ⁢ 33 - 0.71 × ( w ⁢ ⁢ 33 ) 2 + 0.012 × D ⁢ ⁢ 33 × Dg ) ( I ) As shown in FIG. 13, when the side walls 33a of each beam member 33 are parallel, the ionized atoms have a lower density on the surface of the semiconductor substrate 72 at areas below the beam members 33 than in the other areas (see 76a or D2 in FIG. 13). However, the coefficient of variation can be kept to approximately 10% or less, as shown in FIGS. 14˜17. It is possible to utilize in a positive manner the phenomenon that the beam members 33 cause the uneven density distribution within ionized atoms irradiation area. In some types of semiconductor devices, the characteristics is improved by having the ionized atoms distributed with an uneven density. In this case, the shape of the beam members 33 can be adjusted appropriately utilizing the factors (1)˜(5) and the numerical formula (I) so as to obtain the desired density distribution. It may be desirable that the ionized atoms are distributed with a more even density. This requirement can be met by modifying the shape of the side walls of each the beam member 33. As shown in FIG. 18, side walls 36a of the beam member 36 are inclined so that the width of the beam member decreases along the traveling path of the ionized atoms. That is, the distance between adjacent second penetrating holes 34 is shorter at the side of the beam members 36 from which the ionized atoms proceed toward the semiconductor substrate 71, and is longer at the side of the beam members 36 to which the ionized atoms are irradiated. One could also say that the beam member 36 has a longer width at the side away from the semiconductor substrate 72, and has a shorter width at the side by the semiconductor substrate 72. As a result, a large amount of ionized atoms are able to penetrate into a space below the beam members 36. The density distribution 74b of the ionized atoms in the semiconductor substrate 72 is therefore more even (see 76b). Further, since the beam member 36 has a longer width at the side away from the semiconductor substrate 72, the outer second semiconductor layer 31 (see FIG. 2) and the inner second semiconductor layer 32 (see FIG. 2) can be joined firmly by the beam members 36. Forming the side walls 36a of the beam members 36 in an inclined manner ensures the mechanical rigidity of the stencil mask 10 while allowing the density distribution of the ionized atoms to be made even. As shown in FIG. 19, when side walls 37a of beam member 37 are more inclined, the density distribution of the ionized atoms introduced into the semiconductor substrate 72 can be made more even. As shown in FIG. 19, when end part of the beam member 37 at the semiconductor substrate 72 side are formed as acute angle, there is almost no variation of density distribution 74c in the semiconductor substrate 72. Next, other characteristics of the stencil mask 10 will be described. FIG. 45 schematically shows a stencil mask 910 of Japanese Patent Application Publication No. 2002-280290. The stencil mask 910 comprises penetrating holes 934 that form a rectangular loop. An outer semiconductor layer 931 and an inner semiconductor layer 932 are joined by beam members 933. The beam members 933 are formed at approximately central parts of four edges of the inner semiconductor layer 932. In the stencil mask 910, right angle projecting walls 935a are formed at the comers 935 of the penetrating holes 934, these right angle projecting walls 935a being formed at side walls of the inner semiconductor layer 932 that is demarcated by the penetrating holes 934. Stress readily accumulates at these right angle projecting walls 935a, and consequently deformation can readily occur. By contrast, in the stencil mask 10 of the present embodiment, as shown in FIG. 4, the comer part penetrating holes 35 are approximately square and the beam members 33 are formed so that right angle projecting walls 35a disappear. That is, the comer part penetrating holes 35 have a convex polygonal shape and do not have projecting angles formed therein. Consequently, with the stencil mask 10, positions where stress readily accumulates are not formed in the inner semiconductor upper layer 32 and the outer semiconductor upper layer 31. Deformation of the inner semiconductor upper layer 32 and the outer semiconductor upper layer 31 can be controlled extremely well with the stencil mask 10. FIG. 20 shows a variant of the stencil mask 10. FIG. 20 shows a plan view of essential parts of a second semiconductor layer 30 of the variant. In this variant, angled beam members 233 are formed in comer penetrating holes 235. The comer penetrating holes 35 usually have a greater area than the remaining penetrating holes 34. As a result, the following problems can readily occur: deformation near side walls of the comer penetrating holes 35 is larger than other portion, and; the amount of ionized atoms introduced below the comer penetrating holes 35 is larger than the amount of ionized atoms introduced below the penetrating holes 34. In order to solve these problems, the angled beam members 233 are formed within the comer part penetrating holes 235. Deformation of the second semiconductor layer 30 or bias in the amount of ionized atoms that are introduced is thus controlled at the comer penetrating holes 235. FIG. 21 shows another variant of the stencil mask 10. FIG. 21 shows a plan view of essential parts of a second semiconductor layer 30 of the variant. In this variant, a plurality of angled beam members 333 and 334 is formed in comer penetrating holes 335. In this case, deformation of the second semiconductor layer 30 or bias in the amount of ionized atoms is thus controlled at the comer penetrating holes 335 to a greater extent than with the variant shown in FIG. 20. FIG. 22 shows another variant of the stencil mask 10. FIG. 22 shows a plan view of essential parts of a second semiconductor layer 30 of the variant. In this variant, comer penetrating holes 435 are curved, and a plurality of comer beam members 433 is formed in each corner penetrating hole 435. The comer beam members 433 extend in a radiating shape from the inner semiconductor upper layer 32 toward the outer semiconductor upper layer 31. In this variant, deformation of the second semiconductor layer 30 or bias in the amount of ionize atoms is thus controlled at the comer penetrating holes 435 to a greater extent than with the above variant. FIG. 23 shows another variant of the stencil mask 10. FIG. 23 shows a plan view of essential parts of a second semiconductor layer 30 of the variant. In this variant, a plurality of square second penetrating holes 34 is formed, and lattice shaped beam members 533 are formed. The lattice shaped beam members 533 can increase the mechanical rigidity of the stencil mask even though they are narrow in width. Masking effects caused by the beam members 533 can consequently be kept small. The plurality of second penetrating holes 34 has a convex polygonal shape. FIG. 24 shows another variant of the stencil mask 10. FIG. 24 shows a plan view of essential parts of a second semiconductor layer 30 of the variant. In this variant, a plurality of triangular second penetrating holes 34 is formed. Beam members 633 extend in a plurality of directions. The beam members 633 that extend in a plurality of directions can increase the mechanical rigidity of the stencil mask even though they are narrow in width. Masking effects caused by the beam members 633 can consequently be kept small. The plurality of second penetrating holes 34 has a convex polygonal shape. FIG. 25 shows another variant of the stencil mask 10. FIG. 25 shows a plan view of essential parts of a second semiconductor layer 30 of the variant. In this variant, a plurality of hexagonal second penetrating holes 34 is formed. Beam members 733 can increase the mechanical rigidity of the stencil mask even though they are narrow in width. Masking effects caused by the beam members 733 can consequently be kept small. The plurality of second penetrating holes 34 has a convex polygonal shape. FIG. 26 shows a variant of a stencil mask that differs from the stencil mask 10. FIG. 26 shows a plan view of essential parts of a second semiconductor layer 30 of the variant. In this stencil mask, a plurality of penetrating holes 834 is aligned in an x direction. These penetrating holes 834 are repeated in a y direction. The penetrating holes 834 are provided in a striped pattern. This stencil mask is utilized in the case where a striped ion introducing area is to be formed. As shown in FIG. 26, beam members 833 are formed between the penetrating holes 834. If the beam members 833 were not formed, the penetrating holes 834 would form one long penetrating hole extending in the x direction. This type of penetrating hole has a configuration in which the vicinity of the side walls of the semiconductor layer that demarcate the penetrating hole readily becomes brittle. By providing the penetrating hole with the beam members 833 that are formed at a constant pitch, deformation near the side walls of the semiconductor layer can be controlled. Providing the beam members 833 may thus be beneficial even when the penetrating holes do not form a loop. In the above embodiment, all of the measures have been examples applied to the second semiconductor layer 20. However, the aforementioned technique can also be utilized effectively for a stencil mask in which penetrating holes are formed in one semiconductor layer, as shown in FIG. 45. (Method of Manufacturing the Stencil Mask 10) The method of manufacturing the stencil mask 10 will be described next with reference to FIGS. 27˜36. First, as shown in FIG. 27, a laminated SOI (Silicon On Insulator) substrate is prepared. The SOI substrate comprises a silicon support substrate 62 (a portion thereof will form a surrounding support substrate 62 shown in FIG. 1), an embedded silicon oxide layer 52 (a portion thereof will form a silicon oxide layer 52 shown in FIG. 1), and a silicon layer 30 (a portion thereof will form the second semiconductor layer 30 shown in FIG.1). As shown in FIG. 28, a first photo mask 92 is patterned onto a surface of the silicon layer 30. Penetrating holes in the first photo mask 92 correspond to the position of the second penetrating holes 34 of the stencil mask 10. Next, as shown in FIG. 29, the RIE (Reactive Ion Etching) method is utilized to etch the part of the silicon layer 30 that is exposed from the first photo mask 92, thus forming trenches 34. The configurations of the beam members 36, 37 shown in FIG. 18 and FIG. 19 can be obtained by processing side walls of the trenches 34 so that the side walls taper gradually. Processing the side walls of the trenches 34 into the tapered shape can be realized by adjusting etching conditions such as the flow ratio of the etching gas, RF power, pressure, etc. It is possible to form trenches 34 having a long width at a top side and short width at a bottom Next, as shown in FIG. 30, a silicon oxide film 39 (an example of a sacrifice material) is filled into the trenches 34 utilizing the CVD (Chemical Vapor Deposition) method. At this juncture, the embedding of the silicon oxide film 39 is satisfactory if the side walls of the trenches 34 have been processed into a gradually tapering configuration. Instead of the CVD method, SOG (Spin On Glass) material may be filled utilizing the spin application method. Next, as shown in FIG. 31, the RIE method is utilized to etch the first photo mask 92 formed on the surface of the silicon layer 30. The etching can also be realized using the CMP (Chemical Mechanical Polish) method instead of the RIE method. Next, after a thin oxide film on the surface of the structure that was formed by means of the steps up to this point has been removed using dilute hydrofluoric acid or the like (this step is not shown), as shown in FIG. 32, the CVD method is utilized to form a polysilicon layer 20 that covers the surface of the structure. The epitaxial growth method may be utilized instead of the CVD method. Furthermore, hydrochloric acid, hydrogen gas, etc. may be utilized to remove the thin oxide film. Next, as shown in FIG. 33, the polysilicon layer 20 is caused to remain only on the surface of the structure by utilizing the CDE (Chemical Dry Etching) method to remove the polysilicon layer 20 formed on an bottom surface of the structure, or by performing the removal thereof after protecting the entire upper surface of the polysilicon layer 20 with a photo mask. Subsequently, a second photo mask 94 is patterned onto the surface of the polysilicon layer 20 that has been caused to remain. Penetrating hole in the second photo mask 94 correspond to the position of the first penetrating holes 24 of the stencil mask 10. Next, as shown in FIG. 34, the RIE (Reactive Ion Etching) method is utilized to etch the part of the polysilicon layer 20 that is exposed from the second photo mask 94, thus forming the first penetrating holes 24. After the first penetrating holes 24 have been formed, the etching technique is utilized to remove the second photo mask 94. Next, as shown in FIG. 35, the surface of the polysilicon layer 20 is thermally oxidized to form a thermal oxidization layer 96. After the thermal oxidization layer 96 has been formed, a third photo mask 98 is formed by patterning the bottom surface. Next, as shown in FIG. 36, an alkali solution is utilized to etch the silicon support substrate 62 exposed from the third photo mask 98 until the embedded silicon oxide layer 52 is exposed. Potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH), etc. can be utilized in the alkali solution. Finally, after the exposed embedded silicon oxide layer 52 has been removed by etching, BHF (buffered hydrofluoric acid) or the like is utilized to etch the silicon oxide film 39 and the thermal oxidization layer 96 without etching the silicon layer 30 and the polysilicon layer 20. The silicon oxide film 39 and the thermal oxidization layer 96 are thus selectively removed. The stencil mask 10 shown in FIG. 1 can be obtained by performing the above steps. In the second embodiment, the method of utilizing a stencil mask to manufacture a semiconductor device having a switching function will be described. The semiconductor device of the present embodiment is a level shift circuit (an example of a compound device) in which a high potential circuit region and a low potential circuit region are formed in one semiconductor substrate. FIG. 37 schematically shows a plan view of a level shift circuit 1000. The level shift circuit 1000 comprises a high potential circuit region 1012, a low potential circuit region 1011, and a mediating circuit region 1010 that connects the two. A semiconductor switching element that performs switching of high voltage power is formed in the high potential circuit region 1012. A control circuit for switching the semiconductor switching element ON and OFF, and that operates at low potential is formed in the low potential circuit region 1011. The high potential circuit region 1012, the low potential circuit region 1011, and the mediating circuit region 1010 are formed in one semiconductor substrate. Separating ion distributing regions 1016 are formed along an insulating and separating outer trench 1015. The high potential circuit region 1012 and the mediating circuit region 1010 are formed within an island portion that is insulated from and separated from the surrounding low potential circuit region 1011 by the insulating and separating outer trench 1015 and the p type separating ion distributing regions 1016. An insulating and separating inner trench 1013 that forms a loop is formed within the island portion. The high potential circuit region 1012 is enclosed by the insulating and separating inner trench 1013. An intervening region 1014 is formed between the insulating and separating outer trench 1015 and the insulating and separating inner trench 1013. Circuits etc. are not formed in the intervening region 1014. Further, there may be cases where the insulating and separating inner trench 1013 is not formed, and in this case the intervening region 1014 becomes a peripheral region of the high potential circuit region 1012. In this case, a structure for maintaining withstand voltage may be formed in the peripheral region. It is possible to adjust the high potential circuit region 1012 to have point symmetrical configuration by forming the insulating and separating inner trench 1013. The mediating circuit region 1010 is formed within the island portion. The mediating circuit region 1010 is enclosed by the insulating and separating outer trench 1015, the insulating and separating inner trench 1013, and insulating and separating trenches 1017. An LDMOS (Lateral Diffused MOS) is formed in the mediating circuit region 1010. FIG. 38 schematically shows a longitudinal cross-sectional view of the LDMOS formed in the mediating circuit region 1010. FIG. 38 corresponds to a longitudinal cross-section along the line A-A of FIG. 37. The LDMOS is formed utilizing a SOI substrate 1028 comprising a p+ type semiconductor lower layer 1022, an embedded insulating layer 1024, and an n type semiconductor upper layer 1026. The LDMOS is formed in the island portion (the mediating circuit region 1010) enclosed by the insulating and separating trenches 1013, 1015, and 1017. The low potential circuit region 1011 that operates at low voltage is formed in a region outside the insulating and separating outer trench 1015, at the left side in the figure. The high potential circuit region 1012 that operates at high voltage is formed in a region outside the insulating and separating inner trench 1013, at the right side in the figure. Insulating material consisting of silicon oxide is filled into the insulating and separating trenches 1013, 1015, and 1017. Silicon or a different semiconductor material may be utilized as the semiconductor material of the SOI substrate 1028 of the present embodiment. A drift region 1052 of the LDMOS is formed utilizing the semiconductor upper layer 1026 of the SOI substrate 1028. A p type body region 1032 is formed at a surface side of the drift region 1052. A p+ type body contact region 1034 and an n+ type source region 1036 are formed in the body region 1032. The source region 1036 is separated from the drift region 1052 by the body region 1032. The body contact region 1034 and the source region 1036 are connected with a source electrode S. A gate electrode 1044 faces, via a gate insulating film 1042, the body region 1032 that separates the source region 1036 and the drift region 1052. An n+ type drain region 1072 is formed at the surface side of the drift region 1052. The body region 1032 and the drain region 1072 are separated by the drift region 1052. The drain region 1072 is connected with a drain electrode D. An LOCOS oxide film 1062 is formed on a surface of the drift region 1052, this relaxing an electrical field of the surface part. Furthermore, a part of the gate electrode 1044 extends over a surface of the LOCOS oxide film 1062, allowing field plate effects to be obtained. The source electrode S of the LDMOS is connected with the low potential circuit region 1011 via a conductor (not shown), and the drain electrode D of the LDMOS is connected with the high potential circuit region 1012 via a conductor (not shown). The p type separating ion distributing regions 1016 are formed at the side walls that demarcate the insulating and separating outer trench 1015, and pass from the substrate surface through the body region 1032 and the drift region 1052 to the embedded insulating layer 1024. The separating ion distributing regions 1016 are formed along the side walls that demarcate the insulating and separating outer trench 1015. As described above, the separating ion distributing regions 1016 effectively increase the insulation of the insulating and separating outer trench 1015. Furthermore, the separating ion distributing regions 1016 also have the effect of controlling the formation of a p type inversion layer at the border between the embedded insulating layer 1024 and the drift region 1052 when the LDMOS has been turned off. That is, the separating ion distributing regions 1016 promote the discharge of positive holes to the source electrode S that would otherwise accumulate in a p type inversion layer when the LDMOS has been turned off. The phenomenon wherein a depletion layer extends from the border into the drift region 1052 can thus be promoted. A wide range of the drift region 1052 can be depleted when the LDMOS has been turned off and, as a result, an LDMOS with a high withstand voltage can be obtained. Further, the separating ion distributing regions 1016 may cause a depletion layer to extend in a horizontal direction from the separating ion distributing regions 1016 into the drift region 1052. This depletion layer relieves the electrical field that can readily accumulate in a curved part 1032a of the body region 1032. The separating ion distributing regions 1016 are not formed at the insulating and separating inner trench 1013 side at the right side in the figures. Forming a region equivalent to the separating ion distributing regions 1016 as far as this part would cause negative effects such as a reduction in the withstand voltage of the LDMOS, etc. So as to maintain withstand voltage, a region equivalent to the separating ion distributing regions 1016 must not be present at the side wall that demarcates the insulating and separating inner trench 1013. In the present embodiment, an example was given in which the separating ion distributing regions 1016 make contact with the embedded insulating layer 1024. However, the two may equally well be separate. The separating ion distributing regions 1016 may be formed within a range in which the depletion layer extending from the separating ion distributing regions 1016 makes contact with the embedded insulating layer 1024. If the separating ion distributing regions 1016 are within this range, it is possible to promote the discharge of positive holes to the source electrode S that would otherwise accumulate in a p type inversion layer. The drift region 1052 is depleted over a wide range, and an LDMOS with high withstand voltage can be obtained. As described above, the level shift circuit 1000 requires a technique wherein the separating ion distributing regions 1016 that form a loop are formed in the semiconductor upper layer 1026. The technique for the stencil mask described in the first embodiment can be utilized effectively when the separating ion distributing regions 1016 that form a loop are to be formed. An enlarged plan view of essential parts of a stencil mask 110 utilized when the separating ion distributing regions 1016 are to be formed is shown at the lower side of the page of FIG. 39. FIG. 39 shows how the pattern of penetrating holes 134 of the stencil mask 110 corresponds with the level shift circuit 1000 shown at the upper side of the page of FIG. 39. In the present embodiment, as will be described below, ionized atoms are introduced into the semiconductor upper layer 1026 utilizing the oblique ion injection method. As a result, the penetrating holes 134 formed in the stencil mask 110 are formed along the insulating and separating outer trench 1015, and are formed in a location corresponding to the separating ion distributing regions 1016 located at side walls of the insulating and separating outer trench 1015. Next, the method of manufacturing the LDMOS will be described with reference to FIGS. 40˜44. First, the SOI substrate 1028 shown in FIG. 40 is prepared. The SOI substrate 1028 is formed by first forming the embedded insulating layer 1024 by thermally oxidizing a surface of the semiconductor lower layer 1022 (silicon wafer) that contains boron, then laminating the semiconductor upper layer 1026 (silicon wafer) that contains phosphorus. Next, as shown in FIG. 41, a mask film 1092 that consists of an HTO (High Temperature Oxide) film is formed on the semiconductor layer 1026. Next, the mask film 1092 is patterned utilizing the lithography method. At this juncture, the mask film 1092 is removed at positions that correspond to the parts where the insulating and separating trenches 1013 and 1015 are formed. Then, anisotropic etching is utilized to form trenches 1013T and 1015T that extend to the embedded insulating layer 1024 from penetrating holes used for etching trenches of the mask film 1092. Next, as shown in FIG. 42, the stencil mask 110 is disposed above the SOI substrate 1028, and oblique ion injection is performed toward a surface of the SOI substrate 1028. The solid arrows in the figure show the directions in which the ionize atoms are injected. The ionized atoms that have passed through the penetrating holes 134 of the stencil mask 110 are introduced selectively only at side walls of the trench 1015T. Since the stencil mask 110 covers the above of the trench 1013T, the ionized atoms are not introduced into the trench 1013T. Ion introducing areas 1016a can be formed only at the side walls that demarcate the trench 1015T. Next, as shown in FIG. 43, the mask film 1092 is removed by wet etching. After the mask film 1092 has been removed, the trenches 1013T and 1015T are filled with a TEOS (Tetra Ethyl Ortho Silicate) film utilizing, for example, the vacuum CVD method. Then, as shown in FIG. 44, thermal processing is performed, whereupon impurities introduced into the ion introducing areas 1016a are activated, and the separating ion distributing regions 1016 are formed. Furthermore, the thermal process for forming the ion introducing areas 1016a is not restricted to being formed at the aforementioned step, but can be performed at any appropriate point in the process. Next, a known manufacturing technique such as the ion introducing method, the thermal oxidizing method, or the like, is utilized to form a distributing area, an oxide film, electrode wiring, etc. on the surface side, thus allowing the LMDOS shown in FIG. 38 to be obtained. Specific examples of embodiments of the present invention have been described in detail above, but these merely illustrate some possibilities of the invention and do not restrict the claims thereof. The art set forth in the claims includes various transformations and modifications to the specific examples set forth above. In the above embodiments, examples were given in which a semiconductor stack was utilized wherein a first semiconductor layer and a second semiconductor layer were stacked in a stencil mask. Instead of this example, the stencil mask of the present invention may utilize a single semiconductor layer. In the case where this type of stencil mask is manufactured, first penetrating holes are first formed from one face, and the depth of the first penetrating holes is controlled using time or the like so as to prevent their passing through the semiconductor layer. Then a plurality of second penetrating holes are formed on the other face, these second penetrating holes passing through to the first penetrating holes. The second penetrating holes are formed in a distributed manner, and remaining parts thereof form beam members. If this type of manufacturing method is used, the stencil mask of the present invention can be obtained even with a single semiconductor layer. Furthermore, the technical elements disclosed in the present specification or figures may be utilized separately or in all types of conjunctions and are not limited to the conjunctions set forth in the claims at the time of submission of the application. Furthermore, the art disclosed in the present specification or figures may be utilized to simultaneously realize a plurality of aims or to realize one of these aims.

062326139

description

DESCRIPTION OF THE PREFERRED EMBODIMENT Before explaining the disclosed embodiment of the present invention in detail it is to be understood that the invention is not limited in its application to the details of the particular arrangement shown since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation. FIG. 1 is a side cross-sectional view 1 of an end-emitting differentially pumped capillary (DPC) discharge source. The DPC has metal electrode 10 having a port through-hole 15 for allowing gas G such as xenon 2 to enter through port 15 in the direction of arrow I from a high pressure region 5. On the opposite side of an electrically insulating or partially insulating capillary 20 is a second electrode 30. Electrodes 10 and 30 serve as electrical connections to the flowing gas G, that is located between those electrodes 10 and 30 within the capillary 20. When a voltage V, is applied between the electrodes 10, 30, an electric field is produced within the gas G between the electrodes 10, 30, and particularly within the capillary 20, that causes electrons to be accelerated and collide with the gaseous atoms to highly excited and ionized states that radiate the desired light for use in various applications that are describe above. An example of the differentially pumped capillary (DPC) discharge source of FIG. 1 along with operational ranges of current, pressure, repetition rate, and the like, is described and shown in U.S. Ser. No. 09/001,696 filed on Dec. 31, 1997, now U.S. Pat. No. 6,031,241, entitled: Capillary Discharge Extreme Ultraviolet Lamp Source for EUV Microlithography and other Related Applications now issued as U.S. Pat. No. 6,031,241, by the same assignee, which is incorporated by reference. Referring to FIG. 1, gas G is flowed into the electrode region 10 at a selected pressure between approximately 0.1 and approximately 50 Torr and is pumped out at the radiation emitting end as described above such that the pressure beyond the emitting end 35 of the capillary 20 is less than approximately 0.1 to approximately 0.01 Torr (depending upon the absorption path length to the collecting optic) to avoid absorption of the EUV light emitted from the capillary. Debris 40 is produced when the current pulse is initiated within the capillary 20 and is ejected from the emitting end 35 of the capillary 20 and can be propelled toward optic components 50 (such as a multilayer concave reflecting mirror with alternating layers of molybdenum and silicon) that are used to collect the radiation E emitted from the end 35 of the capillary 20, thereby damaging the optics 50 either by pitting it with particle chunks of debris or by coating it with a layer of absorbing material. Experimentally, a range of debris sizes was observed. A distribution was measured by microphotographing sample regions of silicon witness plates which have been exposed to many discharge pulses of the lamp at close proximity of approximately 5 cm. The observed debris sizes range from a maximum of 40 microns in diameter down to the diffraction limit of high power optical microscopes of approximately 0.5 microns. The relative distribution of the particle sizes was seen to depend strongly on the operating characteristics of the discharge such as but not limited to pressure, bore diameter, current, gas flow rate, and the like. Under low magnification, the particle deposition field on the witness plate was observed to be localized and centered on the projection of the capillary bore axis. The debris field observed was approximately 1 cm in extent (full width), which means that the overwhelming majority of the particulate debris was ejected from the capillary at angles from 0 to 6 degrees with respect to the capillary axis. These observations form the physical foundation for the usefulness of the APEC geometry in producing EUV radiation with greatly reduced debris reaching regions beyond the lamp. All debris exiting from the lamp region is potentially damaging to EUV collecting optics facing the output of the capillary discharge. Submicron-sized particles down to single atoms produce a coating on the surface of the optics which leads to partial absorption of the EUV light. Larger particles, especially those greater than approximately 10 microns in diameter, can crater and dig into the surface of the optics, thereby reducing the useful EUV flux. FIG. 2 is a side cross-sectional view 100 of a first embodiment of an angular pumped and emitting capillary (APEC) discharge source of the subject invention. The uniqueness of the APEC is the geometry of the capillary 120 and electrode 130 at the light emitting end 127 of the capillary 120. Referring to FIG. 2, the APEC 100 overcomes the debris problem of the FIG. 1 embodiment as well as to allow for more collection of light from the capillary. The APEC 100 differs from the DPC 1 of FIG. 1 in that the radiation E is emitted in an angular direction E1 (because the pressure is typically higher than the ordinary DPC 1 of FIG. 1), symmetrically around the capillary 120 at the low pressure end 127. The capillary end region 127 is tapered as is the end 133 of the electrode 130 with an adjustable space S (approximately 0.1 mm to approximately 5 mm for DPC 1 and approximately 0.1 mm and up if only the collecting trap is used), between them. The radiation E1 that is collected at optics 150 (shown in FIG. 1) comes primarily from the mouth 127, 133 of the cathode as well as from the area between electrodes 110, 130. This angular tapered region 127 allows the light E1 to be collected in a large solid angle which in FIG. 2 can range from approximately 15 degrees or greater with respect to the axis of capillary 120. This geometry also allows differential pumping to continue through the tapered region so that the pressure in the emitting region 127 at the end of the capillary bore 125 is still at sufficiently high pressure to generate high radiation flux and also to provide sufficient gas to allow conduction of the discharge current to the electrode 130. Referring to FIG. 2, the electrode 130 also provides a direct blocking path for any debris that might be generated within the bore region 125 as the discharge current passes through the capillary 120. Different angles can be used within the angular region as well as different gaps between the capillary bore mouth 127 and the electrode 130 to allow for optimization of the radiation flux output. The flux output can be measured with a calibrated EUV diode type meter, so that the separation space is adjusted between the end of the capillary and the blocking means, until a maximum radiation is achieved. At the high pressure end 122 of the capillary bore 125 where the gas G is flowed into the capillary 120, the electrode 110 can be of several configurations including the hollow cylinder shape as shown in FIG. 2 or a solid cylinder shape that is inserted within the capillary bore region with the gas flowed is around the cylinder or flowed through a hole in the cylinder electrode. Another version might be a heated filament as a cathode. FIG. 3 is a side cross-sectional view 200 of a second embodiment of an angular pumped and emitting capillary (APEC) discharge source of the subject invention incorporating a window 150 around the emitting region and having a constant pressure of the gas within that region, rather than operate with differential pumping. The APEC device of FIG. 3 is for obtaining intense visible, ultraviolet, or vacuum ultraviolet emission. This version incorporates a window 150 around the emitting region E2 and has a constant pressure of the gas within that region, rather than operate with differential pumping. Here the insulating capillary would be simple in shape, with the end face of the capillary normal to the bore axis. In this case the large electrode 130 would serve to block and collect debris and there would be a much larger angular admitting region because differential pumping would not be required to avoid absorption of the emission E2 by the emitting gas outside of the bore region. FIG. 4A is a side cross-sectional view 300 of a third embodiment of an angular pumped and emitting capillary(APEC) discharge source of the subject invention. This embodiment is a variation on the APEC design shown in FIG. 2. Here the principal functional difference is that the gas is admitted to the system from the same end at which the useful eight is emitted. Discharge conditions and parameters are identical to the APEC 100. Referring to FIG. 4A, the angular pumped and emitting capillary 320 of embodiment 300, has metal electrodes 310 and 330 at opposite ends of an insulating capillary 320 whose bore 325 is filled with gas (i.e., Xenon helium, neon, argon, and krypton, which were referred to in U.S. Pat. No. 6.031,241 to the same inventors and same assignee, which has been incorporated by reference) under electrical discharge conditions. Both the metal electrodes 310 and 330 are hollow with axial bores 315 and 335-337 respectively. Gas G is flowed into the discharge region through the axial bore hole 315 in the metal electrode 310 located at the end of the capillary from which the useful radiation is emitted. Gas is admitted to this electrode by a gas inlet 311 connected to plumbing (not shown in FIG. 4A) in a similar fashion to the APEC 100. Outflowing gas enters both the capillary bore 325 and the annular gap between the electrode face 317 and the capillary face 327, which bound the line-of-site of the emitted useful radiation. This results in a region 321 of high gas density in the region of the discharge seen directly along the line-of-sight, which increases radiated output relative to the simpler APEC 100. Gas is pumped away both in the low pressure region into which the radiation is emitted, and also through the vacuum exhaust bore hole 339 in the metal electrode 330 on the opposite side of the capillary. Additionally, the holes 315, 339 in both electrodes 310, 330 serve as "shock tubes", which guide the discharge-induced gas pressure pulse by allowing an unimpeded path for axial gas to flow. Much of the particulate debris shot out the radiating end 317, 327 of the capillary bore would simply travel down the gas inlet line and come to rest deep in the gas reservoir behind the electrode 310. Finally, the flowing gas may serve to cool and protect the components. A tube of flowing gas exhausting into vacuum forms a Mach 1 nozzle. The kinetic temperature in a Mach 1 expansion is for a monatomic ideal gas, three-fourths of the reservoir temperature. If the inlet gas is cooled nearly to its freezing point temperature (to less than 4/3 its freezing temperature in Kelvins) then the expansion should cause gas to freeze out on the tip of the electrode and inner wall of the capillary bore, to serve as an ablative buffer which may reduce bore erosion and debris formation in the first place. Gas that does not freeze out would flow more slowly and have a higher atom density for a given inlet pressure, which also would be salutory from the standpoint of maximizing the radiator density at the radiating end of the capillary. Finally, it cools the capillary material making it a better insulator. Another variation on the modified APEC design is shown in FIG. 4B. Here, the radiating gas G flowed into the capillary 320 through both metal electrodes 310 and 340. Electrode 340 has a C-cross-sectional shape with interior 341 and gas inlet 349. Gas exhaust and useful radiation E are removed by the vacuum region containing the optics as for the simpler APEC 100. This configuration maintains a more nearly uniform high density of gas throughout the length of the capillary than any other design. FIG. 5 is a side cross-sectional view 400 of a fourth embodiment 400 of a capillary discharge lamp with a debris collecting device attachment 405. The assembly consisting of electrodes 410 and 430, capillary 420, and gas flow G7 is functionally identical to the DPC 1, FIG. 1. The debris collection device 405, in its most simple form a metal cup, kinetically intercepts the debris particles (40, in FIG. 1) while allowing the useful radiation E7 at greater axial angles to escape and be collected by optics (50, in FIG. 1). The debris collector 405 would subtend a full angle of at least 12 degrees along the capillary axis; its size would therefore depend on its distance from the end of the capillary. The collector 405 can be at the same or different voltage as the electrode 410. Choice of material for the debris collector 405 would include but not be limited to stainless steel, aluminum, brass, copper and the like materials. The use of insulators as collector materials would be problematic, as electrical charging in the presence of plasma could affect debris trajectories in an uncontrolled way. Shape of the collector is probably unimportant. A U-shaped device 405 as illustrated in FIG. 5 would intercept most secondary debris coming off the collector surface itself. FIG. 6 represents another embodiment of the discharge device with a U-shaped debris blocker/collector 505 that does not use a capillary associated with generating the discharge. Referring to FIG. 6, high pressure gas G9 is flowed through one cylindrical electrode 510 and a debris collecting (or just blocking) device 505 also serves as the other electrode 505. The EUV emission E9 is produced in the region where the gas exits the between electrode ends 507 of the debris catching electrode 505 and the ends 511 of the cylindrical electrode 510. The shape of the collector 505 in this case is more important than for the collector 405 (FIG. 5) since collector 505 also serves as an electrode. Electrical impedance between electrode faces 507 and 511 will determine distance between electrodes, and angular intercept requirements will in turn constrain the collectors size. Surface figure on end faces 507 will also be important. Collector material will require tolerance to high current throughput and high temperatures, and like before, the concave/U shape 505 will help to decrease secondary debris. The discharge lamp operating at wavelengths longer than approximately 100 nm can be used for materials processing, medical treatment such as photodynamic therapy, and other applications where pulsed high flux vacuum ultraviolet, ultraviolet, visible and near infrared wavelengths of light are required. This source can have applications for an EUV microscope. Such a microscope could be used to observe features as small as 0.05 microns (50 nm) and have very large depth of focus. One application would be as an inspection tool on a microlithography fab line in which great depth of focus is required to observe the resist or chip feature side-walls for uniformity and wall slope. It might also be used in hospitals, for example in pathology labs, where a tissue sample (biopsy) needs to be inspected immediately after it is taken from a patient. The microscope can also be used for general high resolution analysis in chemical and pharmaceutical labs. While the invention has been described, disclosed, illustrated and shown in various terms of certain embodiments or modifications which it has presumed in practice, the scope of the invention is not intended to be, nor should it be deemed to be, limited thereby and such other modifications or embodiments as may be suggested by the teachings herein are particularly reserved especially as they fall within the breadth and scope of the claims here appended.

summary

abstract

An apparatus, system and method for handling and translating high level radioactive waste. The apparatus comprises a body for supporting the cask close to the ground so that the cask and the apparatus can pass underneath over head doors. The apparatus further comprises rollers for translating the cask. The apparatus additionally supports the storage cask during spent nuclear fuel transfer procedures.

abstract

In a spent fuel pool of a nuclear power plant, there is provided a system for aligning a nuclear fuel bundle and handling selected fuel rods within the fuel bundle. The bundle includes water rods, full-length and part-length fuel rods extending through a plurality of fuel spacers provided between top and bottom ends of the bundle, each spacer having a plurality of cells accommodating corresponding fuel and water rods. The system includes a bundle alignment system for aligning the fuel rods and water rods, a rod grapple tool to extract selected part-length rods from the bundle, and a fuel rod guide block slidable onto the top end of the bundle for protecting an uppermost fuel spacer of the bundle, and for aligning fuel rods within individual cells of all the fuel spacers in the fuel bundle.

description

The present patent application is a Continuation Application claiming the benefit of non-provisional application Ser. No. 11/521,671, filed Sep. 15, 2006, which issued on May 4, 2010 as U.S. Pat. No. 7,709,815, which application claims benefit of Provisional application No. 60/717,856, filed Sep. 16, 2005. The present invention relates to a lithography system for projecting an image pattern on to a target surface such as a wafer, wherein control data are coupled to a control unit for controlling exposure projections by means of light signals, thereby using a free space interconnect, in particular to a system wherein such control unit is included in close proximity to or within the projection space, more in particular to a multi-beam mask-less lithography system. The current invention in principle relates all the same to charged particle and to light projection based lithography systems Such a system is known, e.g. from the international patent publication WO2004038509 in the name of Applicant, i.e. from the particular embodiment provided by FIG. 14 thereof. The known system comprises a computer system for providing pattern data of an image to be projected by a so called beam column for projecting charged particles, in particular electrons on to a target surface such as a wafer and an inspection tool. The beam column comprises a vacuum chamber in which one or more charged particle sources are accommodated, which emit particles in a manner known per se, using amongst others an electric field for withdrawing particles from said source or sources. The beam column further comprises charged particle optic means for converging an emitted bundle of charged particles, for splitting up the same into a multiplicity of charged particle beams, further referred to as writing beams, and forming exposure projections. A control unit for controlling the exposure projections is included in the form of charged particle optical means for shaping or directing such writing beams, here showing a blanker optical part or modulator array comprising blanking deflectors, as well as a writing deflector array for deflecting writing beams for the purpose writing of a pattern using writing beams not blanked by said blanking deflectors. The blanker optic part, known per se, e.g. from international patent publication WO2004107050 in the name of Applicant, deflects, depending on a computer provided signal a writing beam away from a straight trajectory parallel with other writing beams, to such amount of inclination that no part of the writing beam effectively passes the opening provided for each writing beam in a stopping plate, thereby effecting an “off” state of the particular writing beam. All optic parts in the beam column are shaped with an array of openings, the openings of the separate parts being mutually aligned so as to enable the passage of a writing beam in said column towards said target surface in a controlled manner. The known mask-less multi-beam system is further typically provided with blanking deflectors having both the source and the target surface arranged in a conjugate plane thereof, i.e. it may easily be combined with the subject matter of WO2004/0819010. In this manner the lithography system favourably realizes an optimal brightness of the source on the target surface. Also, in this manner a minimum amount of space is required for the blanker array. The target surface for a writing beam is held on a stage included in the beam column. The stage, induced by an electronic control unit of the system, moves together with said surface perpendicularly relative to said emitted writing bundles, preferably solely in a direction transverse to a direction in which such writing bundles are finally deflected for writing purposes. Writing of a pattern by the known lithography system is thus effected by the combination of relative movement of the target surface and a timed “on” and “off” switching of a writing beam by said blanker optics upon signalling by said control unit, more in particular by a so-called pattern streamer thereof. Signalling for on/off switching, i.e. modulating of a writing beam is in the related known system performed by using light optics. The blanker optics thereto comprises light sensitive parts such as photodiodes, for receiving light signals, which are converted into electronic signals, e.g. applying the measures as provided by the international patent publication WO2005010618 in the name of Applicant. The light signals are produced by electronic to light conversion by said control unit for the system, and are transported to the beam column by means an optical carrier, in casu a bundle of glass fibres that finally projects from “e.g. a transparent part of the vacuum boundary”. Light signals are projected to said blanker optics using a lens system, which in the known system is disclosed to be comprised of a converging lens located in between a transmitter part and the light sensitive parts of deflectors included in the blanker optic part. The arrangement of deflector, light sensitive parts and light to electric conversion is produced using both so-called MEMS- and (Bi-) CMOS-technology. So as to prevent the use of mirroring parts, in the related known system the signalling light beams are projected from a far upper side relative to the blanking optic part, so as to achieve an angle of incidence of the pattern information carrying light signals on the light sensitive elements, as small as possible. The publication in which the related embodiment is comprised, teaches however, that other locations of projection may be realised when using mirrors for correcting the larger angles of incidence occurring at most of such alternative locations. Although general set up of the above described lithography system has proven to be satisfactorily, drawbacks are noticed at the oblique illumination system disclosed, in that it suffers from non-optimal transmission of light, at least less than expected and in that it suffers from relatively large aberrations. The present invention therefore seeks to improve the known mask-less multi-beam lithography system in general, however, in particular as to the light optics system (LOS) thereof. The present invention further has for an object to improve the lithography system by either by increasing the light transmission efficiency thereof and/or by reducing the chance of aberrations in the light optic part thereof. The present invention solves, at least to a significant extend eliminates the above said problems encountered in the lithography systems using a mirror for redirecting light beams, provided with one or more holes for letting through exposure, e.g. writing projections of said lithography system part. In particular a said free space optical interconnect of such systems according to the invention comprises a holey, i.e. holed mirror incorporated in the projection trajectory of said plurality of writing beams, wherein said mirror is arranged relative to said emitter part and said light sensitive elements to realize an on-axis, i.e. an at least virtually perpendicular incidence of said light beams on said light sensitive elements, said mirror being provided with at least one hole allowing passage of one or more of said writing beams. Alternatively provided, in accordance with further insight underlying the present invention, a lithography system is attained, in which an electronic image pattern is delivered to a exposure tool for projecting an image to a target surface, said exposure tool comprising a control unit for controlling exposure projections, said control unit at least partly being included in the projection space of the said exposure tool, and being provided with control data by means of light signals, said light signals being coupled in to said control unit by using a free space optical interconnect comprising modulated light beams that are emitted to a light sensitive part of said control unit, wherein the modulated light beams are coupled in to said light sensitive part using holed, alternatively denoted holey mirror for on axis incidence of said light beams on said light sensitive part, the one or more holes of said mirror being provided for passage of said exposure projections. Using a system according to the present invention minimizes the presence of aberrations by remaining on-axis at projection of light signals, without, at least noticeably interfering with, i.e. hampering the exposure projections of the exposure tool of the lithography system. With the presently claimed solution, the invention is realized in a new, in advance expectedly impossible, though at hindsight relatively simple to perform highly favorable manner. The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications. In the figures, corresponding structural features, i.e. at least functionally, are referred to by identical reference numbers. FIG. 1 represents an overall side view of the prior art lithography system that is improved by the current invention, in which at light emitter, or modulation means ends 2 of a light carrier Fb, in case embodied by optical fibers Fb, light beams 8 are projected on modulator array 24 using an optical system, represented by lenses 54. Modulated light beams 8 from each optical fiber end are projected on a light sensitive element, i.e. light sensitive part of a modulator of said modulator array 24. In particular, ends of the fibers Fb are projected on the modulator array. Each light beam 8 holds a part of the pattern data for controlling one or more modulators, the modulation thereof forming a signaling system for transferring pattern data based modulator array instructions for realizing a desired image on said target surface. FIG. 1 also shows a beam generator 50, which generates a diverging charged particle beam 51, in this example an electron beam. Using an optical system 52, in casu an electron optical system, this beam 51 is shaped into a parallel beam. The parallel beam 51 impinges on beam splitter 53, resulting in a plurality of substantially parallel writing beams 22, directed to modulation array 24, alternatively denoted blanker array. Using modulators in the modulation array 24, comprising electrostatic deflector elements, writing beams 27 are deflected away from the optical axis of the litho system, and writing beams 28 pass the modulators undeflected. Using a beam stop array 25, the deflected writing beams 27 are stopped. The writing beams 28 passing stop array 25 are deflected at deflector array 56 in a first writing direction, and the cross section of each beam let is reduced using projection lenses 55. During writing, the target surface 49 moves with respect to the rest of the system in a second writing direction. The lithography system furthermore comprises a control unit 60 comprising data storage 61, a read out unit and data converter 63, including a so-called pattern streamer. The control unit 60 is located remote from the rest of the system, for instance outside the inner part of a clean room. Using optical fibers Fb, modulated light beams 8 holding pattern data are transmitted to a projector which projects the ends of the fibers on to the modulation array 24. FIG. 2 figuratively represents the light optic system of the improved lithography system according to a first embodiment. It entails the use of a holey mirror 104, which is applied for realizing an in-axis incidence of light beams 8 on the light sensitive elements of modulator array 24. The holey mirror thereto comprises one relatively large hole through which all for blanking deflected writing beams 27 and all undeflected writing beams 28 may pass, or a plurality of relatively small holes 105, one for each deflected or undeflected writing beam. According to preference, the mirror 104 comprises a substantially flat reflecting surface which is included in the system under angle of 45 degrees, so that while maintaining perpendicular incidence of light beams 8 on modulator 24, an axially minimal amount of space is required for the light optic system. With such minimized axial space requirement, design freedom is attained for locating the LOS either to the upper, or to the bottom side of the modulator array 24, which in turn enhances manufacturing freedom of the array 24, which is a highly complex part, manufactured at using CMOS and MEMS technology. With the use of a holey mirror 104, a focusing lens 106, preferably embodied by a lens system performing a focusing function, is included close as possible to the latter, at least closer to the mirror than to the fiber ends 2. By locating said focusing lens 106 in close proximity of the holey mirror 104, it is favorably realized that the holey mirror can be applied without undue loss in light signal intensity, which might otherwise be due to the presence of holes 105. The array of fiber ends 2 are in accordance with the present invention completed with a micro lens array 101, forming a virtual fiber array 103, in fact an array of spots in the focal plane for the micro lenses 101. In line with a particular and independent aspect of the invention, a micro lens of the micro lens array 101 here according to preferred embodiment performs a magnifying, function on the light signals transmitted by a particular fiber of the fiber array Fb. The lens system according to the present invention thus sets forth a dual image system comprising a magnification of each signal by means of a micro-lens, and a subsequent focusing of the signal by means of said lens 106, common to all of the emitted light signals. In this manner favorably, independence is attained in setting, in casu increasing an effective spot size of each fibre, and setting, in casu decreasing a fiber pitch. As to the first effect hereabove, it is according to the present invention preferred to cover an area as large as possible of a light sensitive element, so as to obviate the need for strong focus of the light signal 8, thereby reducing the chance of aberration and thereby reducing the need for further optical elements, which enhances the transmission of light, i.e. reduces the loss thereof. The desired and created light spot is not much larger than the light sensitive area so as to minimize loss of light by projecting light on surrounding, inert parts. This arrangement implies however that the projection of light is relatively sensitive for positioning errors of a light beam 8, in that small displacement thereof implies a reduction in the amount of light than is received by the relevant light sensitive element, e.g. photodiode. Thus, by sizing the incidence spot 24i larger, but not much larger than the light sensitive area, it is according to the invention prevented that expensive or complex optical elements are required in the free space interconnect of the LOS, while on the other hand sensitivity as to misalignment of the incident light beam part is reasonably reduced. In this respect misalignment may be due to actual conditions of the litho system, to structural inaccuracy, or to a combination thereof. As to the second effect mentioned here above, the pitch of the ends of fibers Fb is incompatible with, in particular larger than the pitch of the light sensitive elements on the modulator array 24, unless undue, and consequently uneconomic manufacturing efforts are made. With the present dual lens and dual imaging system independence in setting both parameters is attained in a favorable manner. FIG. 3 represents the arrangement for preferred incorporation of the light optics system described along FIG. 2, in the lithography system, according to the invention. It shows a holder 24S for the above mentioned blanker or modulator array 24, by means of which holder the modulator array 24 is placed in a charged particle column. Such charged particle column is, together with the holder for holding a wafer or other kind of target surface, included in a housing Hv by means of which a vacuum condition for said column and target stage is realized. The array of fibers Fb is fed through an opening in a demountable part of said housing Hv, here by using a significant amount of vacuum compatible sealing material for realizing an air tight sealing of the fibres in said opening. An inner housing end part Fbv of said fibers is thereby also to a significant extend secured from outside mechanical impulses that might act thereon. The end part Fbv of the array of fibers is at its end 2 further secured mechanically to a housing Hl for the lens and mirror part of the light optics system. In turn the housing H1 is secured to said modulator array holder 24S. In this manner it is in a favorable, mechanical manner secured that the positions of the fiber ends 2 and the modulator array, in particular the light sensitive areas thereof are fixed relative to one another. In turn, the array holder 24S is connected to a not depicted frame for elements such as collimator 52, and splitter 53, and as further discussed under FIG. 1, constituting the charged particle column. As illustration in one dimension in FIG. 3, the holey mirror 104 covers the entire area of a modulator array, while in the same manner the lens 106 covers the entire area of the tilted mirror 104. The lens 106 is thereby incorporated axially in close proximity to the holder 24S. It may be clear from the above, that the principles of the dual lens system, mechanical fixation of a lens housing H1 to the blanker 24 and the specific application of a holey mirror 104 may all be applied independently from one another. Further to the latter, the principle of dual imaging can be applied while using an off-axis projection instead of the presently preferred perpendicular projection. FIG. 4 figuratively represents the light optic system of the improved lithography system according to a second embodiment. It entails the use of a holey mirror 107, which is applied for realizing an in-axis incidence of light beams 8 on the light sensitive elements of modulator array 24. The holey mirror thereto comprises one relatively large hole 108 through which all for blanking deflected writing beams 27 and all undeflected writing beams 28 may pass, or a plurality of relatively small holes, one for each deflected or undeflected writing beam. According to preference, the mirror 104 comprises a focusing reflecting surface, said reflecting surface in particular is placed at an angle for reflecting the incident light beams 8 towards the modulator 24 and said reflecting surface in particular being a concave surface for simultaneous focusing the incident light beams 8 onto the modulator 24. With the use of a holey mirror with a focusing reflecting surface 107, a focusing lens 106, may be omitted. It is favourably realized that any loss in light signal intensity, in particular due to reflections at the surfaces of the focusing lens 106, can be further reduced. Furthermore, it is realized that the focusing element in this second embodiment, in particular the concave reflecting surface of the holey mirror 107, can be much closer to the modulator array 24, than the lens 106 in the first embodiment. Due to this close distance, the light optical system of this second embodiment can be designed with a larger numerical aperture and thus with an increased resolving power of the light optical system. Also in the second embodiment of FIG. 4, the array of fiber ends 2 are completed with a micro lens array 101, forming a virtual fiber array 103, in fact an array of spots in the focal plane for the micro lenses 101. A micro lens of the micro lens array 101 performs a magnifying function on the light signals transmitted by a particular fiber of the fiber array Fb. The concave reflecting surface of the holey mirror 107 according to the second embodiment thus sets forth a dual image system comprising a magnification of each signal by means of a micro-lens, and a subsequent focusing of the signal by means of said concave reflecting surface of the holey mirror 107, common to all of the emitted light signals. Furthermore, it is realized that a holey mirror with a focusing reflecting surface 107 as shown in FIG. 4 may also be combined with a focusing lens 106 as shown in FIG. 3. In this case the focusing element 106, 107 comprises two optical parts and both optical parts may contribute to the focusing effect and/or can be used to further reduce optical aberrations. Apart from the concepts and all pertaining details as described in the preceding the invention also relates to all features as defined in the following set of claims as well as to all details as may be directly and unambiguously be derived by one skilled in the art from the above mentioned figures, related to the invention. In the following set of claims, rather than fixating the meaning of a preceding term, any reference numbers corresponding to structures in the figures are for reason of support at reading the claim, included solely as an exemplary meaning of said preceding term.

043549985

summary

The present invention is directed in general to means for improving the power gain factor in a tandem mirror fusion reactor, and more particularly, to a method and apparatus for passively clearing ions trapped in thermal barrier regions formed in a high temperature plasma. Two types of devices are generally favored for generating and confining plasmas. These are the toroidally shaped magnetic confinement devices and the linear cylindrically shaped tandem mirror magnetic confinement devices. The plasma comprises ionized gases including approximately equal numbers of positively charged ions and free electrons at high temperatures. The goal is to generate a fusion reaction in the plasma such that the energy obtained therefrom exceeds the input energy to the system, thereby providing useful output power. The easiest fusion reaction is generated from the bringing together of the two heavy isotopes of hydrogen, deuterium and tritium. When these two particles fuse together, a helium nucleus (alpha particle), a neutron and 17.6 million electron volts of energy are generated. The difficulty with such fusion reactions is that the plasma must exist at an extremely high temperature over a relatively long period of time to first obtain and then maintain the fusion reaction. Such temperatures are needed to overcome the electrostatic Coulomb repulsion between the deuterium and tritium ions. Magnetic and/or electrical field confinement configurations were found to be required to prevent loss of plasma temperature to adjacent walls of the plasma confinement chamber or cell. In addition, the fusion reaction generally produces highly energized protons, neutrons and other particles. A significant problem in the initial formation and sustained maintenance of a high temperature plasma involving such high energy particles is the problem of excluding impurity particles from the plasma. Such impurities are found to cause substantial and potentially disabling plasma energy losses. These energy losses arise because the contaminants generally have a higher atomic number than hydrogen, and the type of electronic excitation, ion recombination and bremsstrahlung radiation losses produced by their presence in the hydrogen plasma (i.e., hydrogen, deuterium, tritium and mixtures thereof) become increasingly deleterious with increasing atomic number of the contaminant. There are a few principal sources for the above-mentioned impurities. First, contaminants such as oxygen, nitrogen or carbon previously absorbed in the walls of the plasma chamber, enter the plasma due either to the vacuum required for operation of the plasma or as a result of other conditions employed to form the plasma initially. Another principal source of contaminants results from the bombardment of the chamber wall material itself by the above described energetic plasma particles and radiation, which tends to cause sputtering or even melting of the chamber wall. Suitable vacuum techniques and high temperature baking may be employed to minimize the adverse effects of absorbed contaminants, but the problem of contaminants produced by bombardment and erosion of the plasma chamber walls have provided substantial difficulties. Finally, helium "ash" impurities generated by the fusion reactions must also be periodically stripped off from the plasma. In the prior art, complicated magnetic divertor systems have been designed in an effort to remove these impurities, but such divertors have been expensive, complex, and otherwise disadvantageous. Conventional divertor devices function to skim off the most contaminated plasma near the wall of the plasma confinement chamber. Tandem mirror reactors confine the fusion plasma ions in an open ended magnetized cylindrical central cell. Axial confinement (end plugging) of the cell is generated by electrostatic potentials of more dense magnetic "mirror" confined plasmas. In operation, the mirror at each end of the fusion reactor acts as a magnetic bottle to narrow the magnetic field and thereby cause the plasma to turn back on itself. That is, the mirror coils at the end of the central cell constrict the magnetic field lines with new field lines, thereby increasing the magnetic field in this region. These extra magnetic field lines push the normal field lines together around the end, with the result that particles within the cell tend to follow the field lines until they are deflected back as if they had come in contact with a mirror. However, some ion leakage still occurs at the portion of the mirror corresponding to the axis of the cylindrical cell, so that a baseball magnet having a minimum-B field is also needed to turn particles around, thereby maintaining the plasma within the central cell of the fusion reactor with a minumum of end loss. A recent improvement in the design of tandem mirror fusion reactors proposed by Baldwin et al., [Baldwin et al., "An Improved Tandem Mirror Fusion Reactor", Lawrence Livermore Laboratory, UCID-18156, April 1979] provides means for enabling a larger electric potential to be generated in the end plug to thereby increase the efficiency of the mirror apparatus. The difficulty in older systems attempting to increase the end plug electrostatic potential was that either the density of the end plug plasma had to be increased, or the temperature thereof had to be increased. The problem with the former is that it led to unacceptable power losses and a large increase in density would produce only a small increase in field potential. Increasing the temperature was also difficult since the hotter electrons would not remain in the end plug, but would diffuse into the rest of the reactor. The Baldwin et al. improvement is accomplished by trapping hotter electrons in each end plug. Baldwin et al. disclosed means for thermally insulating the end plug electrons from contact with those in the solenoid central cell and means, in conjunction therewith, for heating the end plug electrons. Auxiliary heating of the electrons in the end plug may include the use of an electron cyclotron resonance heating unit [ECRH] or other microwave energy source. A key benefit provided by the generation of such an electron temperature differential is that it enables a plasma electrical potential barrier to be generated with a much lower end plug plasma density. In the original tandem mirror concept, the end plug plasma density n.sub.p had to be much greater than the plasma density of the central cell n.sub.c. This new concept enables n.sub.p to be approximately the same as or even less than the cell density n.sub.c. Thus, the large reduction in the required plug plasma density enabled by the higher electron temperature in each end plug both reduces the power consumed in the plugs and opens up the ability to use much simpler and less sophisticated technology in the end plugs. The end plug electron thermal insulation is created by generating a depression in the plasma potential at the entrance to each end plug, which thereby serves as an electron "thermal barrier" between each of the end plugs and the solenoid central cell. The thermal barrier is generated most simply by placing a simple mirror coil at the end of the central cell which serves to throttle down the flow of plasma ions from the central cell as said flow moves towards an adjacent end plug. The density is caused to drop as the plasma expands in cross section as it emerges from the high magnetic field at the throat of the mirror coil, thereby creating a potential depression .phi..sub.b. This depression in the positive potential appears to the negatively charged electrons as a potential barrier and therefore serves as an electron "thermal barrier" between the end plug and the reactor central cell. Thus, so long as the electrons are heated in the end plug at a rate faster than they can escape from the plug by collisions, the electron temperature in the end plug rises relative to the electron temperature in the central cell. Further details of the operation of this thermal barrier are described herein below. Although the thermal barrier concept provides significant potential advantages, a major difficulty is that "passing particles", i.e., ions and electrons crossing the thermal barrier, sometimes collide, causing some of these particles to be trapped in this thermal barrier region between the magnetic mirror and the end plug. In time, because of such collisions, the trapped particle density would grow until the total pressure thereof would equal or exceed the pressure in the central cell of the reactor. Thus, some means is required to pump out or otherwise eliminate these trapped particles from the thermal barrier. One solution for reducing the number of trapped ions would be to use magnetic pumping techniques, i.e., generating a new magnetic oscillating field. Such a field would cause the trapped ions to become more energetic, such that they could ultimately escape from the thermal barrier magnetic well back into the stream of plasma ions energetic enough to be able to freely pass across the thermal barrier. The difficulty with such a magnetic pumping system is that it requires the use of additional power in operation; it does not operative passively. A system for eliminating such trapped ions from the thermal barrier without the requirement that additional power be used therefor would thus have high utility. A further drawback of the above described magnetic pumping system is that it requires the use of copper coils close to the plasma for generation of the oscillating magnetic field. This is also undesirable due to the fact that such coils would tend to react with the plasma, becoming a generator of further impurities. Such coils also would be degraded over time due to the radiation incident thereon. Additionally, many of the ions trapped in the thermal barrier would also be impurity ions, and since control of impurities may become a problem, it would also be desirable to provide means for eliminating such impurities from the reactor, rather than reenergizing them and enabling them to reenter the plasma. Accordingly, it is an object of the present invention to provide a method and apparatus for passively removing ions trapped in a thermal barrier formed in a tandem mirror fusion reactor, to ensure that there is no buildup of such ions therein. It is a further object of the present invention to provide such a method and apparatus whereby trapped impurities are removed from the thermal barrier but not returned to the plasma. A still further object of the present invention is to provide such an apparatus which is simple in construction and which does not otherwise disrupt the flow of the plasma. Still another object of the present invention is to provide a method that is static, not involving pulsed or AC components, and a method that eliminates the need for copper coils or other degradable material in the high energy plasma environment.

040653528

abstract

A nuclear fuel element containing a hydrogen getter to prevent a cladding tube from being broken by hydrogen gas, wherein the hydrogen getter is formed of metal material capable of absorbing hydrogen and a metal member permeable to hydrogen and enclosing said hydrogen-absorbing metal.

047537728

abstract

A tension loaded energy dissipating support member includes multiple successively longer metal straps all connected at each end to an end connector with the longer straps, and preferably the shortest strap, bowing outward laterally such that as the tensile load increases, the straps, beginning with the shortest, successively plastically deform to dissipate shock energy. The initial bowing, type of material, and relative dimensions of the straps can be varied to obtain the desired load supporting and energy dissipating characteristics.

abstract

An alignment plate that is attached to a core barrel of a pressurized water reactor and fits within slots within a top plate of a lower core shroud and upper core plate to maintain lateral alignment of the reactor internals. The alignment plate is connected to the core barrel through two vertically-spaced dowel pins that extend from the outside surface of the core barrel through a reinforcement pad and into corresponding holes in the alignment plate. Additionally, threaded fasteners are inserted around the perimeter of the reinforcement pad and into the alignment plate to further secure the alignment plate to the core barrel. A fillet weld also is deposited around the perimeter of the reinforcement pad. To accommodate thermal growth between the alignment plate and the core barrel, a gap is left above, below and at both sides of one of the dowel pins in the alignment plate holes through which the dowel pins pass.

description

This invention claims the benefit of a provisional patent, Application No. 62/205,242, Filing Date Aug. 14, 2015, by this inventor. Nuclear Energy as motive power for propulsion provides superior performance in terms of bigger payload capacity and much higher speed over conventional chemical or solar-powered rockets. In fact, deep space missions are not economically feasible without nuclear energy. This invention focuses on replacing both chemical and solar-powered rockets with nuclear-powered rockets for deep space journeys. The propulsion section consists of two primary modules: (1) the reactor module, and (2) the propulsion propellant module, also known as the reactor coolant module. It is noted here that the spacecraft propellant is in fact the nuclear reactor coolant, which is a gas. The modules are cone-shaped, and designed in a concentric geometry (i.e., having a common center). They are assembled in sequence in low earth orbit, that is one on-the-top-of the other, as described below. Metaphorically speaking, in a non-scientific description, one might imagine that each module to look like an ice-cream cone. And, the entire propulsion-assembly to look like an ice-cream cone-dispenser, tubular pull-type, without the outer shell or casing. Each module will have locking mechanisms, as well as all the necessary interconnecting utilities, transfer-lines, etc. SMR-P is a very-high-temperature gas-cooled nuclear reactor. The provision for obtaining the nuclear fuel is not included in this effort. The customer is required to purchase the nuclear fuel, per specifications, from authorized sources, or establish own nuclear fuel production capability as permitted by law. The once-through reactor coolant is a gas as it enters the reactor. The reactor has a uranium-235 core, which provides heat from fission reactions. The gas (i.e., the reactor coolant, which is also the spacecraft propellant) passes through the reactor core and is heated to a very high temperature, which then expands through the spacecraft nozzle, and creates the thrust. It is however stored as liquid, during transportation from earth to low earth orbit and assembly at the Low Earth Orbit Propellant Depot—similar to that of conventional chemical rockets. The nuclear fuel consists of High Enriched Uranium, which weighs much less than similar amount of fuel for chemical rockets. The amount of nuclear fuel is mission dependent. The fuel however will be designed such that it will be sufficient for the journey plus reserve. The reactor power is mission specific, and depends on the customer's speed and payload requirements. The nuclear fuel specifications will be provided following the customer's description of the mission, and declaration of speed and payload requirements. A number of gases, such as helium, hydrogen, etc., are envisioned to be used for reactor coolant/the spacecraft propellant, depending on availability, economics, and/or the mission specifics. Additional or spare reactor coolant module(s) may be incorporated into the spacecraft design, for multi-generational journey as the mission evolves. This concept envisions that for a multi-generational journey, the spacecraft is so equipped with: (A) all the necessary provision to scoop and store reactor coolant gases from the atmospheres of en route planets, and/or (B) spare reactor coolant modules. In all cases, the reactor coolant modules are designed to follow the reactor module, in that order, to provide radiation shielding. Other modules, such as instrumentation, electric power, scientific equipment, supplies, and/or crew, will follow the reactor coolant modules, in a similar fashion. It is not the intent of this effort to describe the rest of the spacecraft design. It is sufficed to say that the instrumentation/supplies/equipment/electric power modules, as well as the crew module (if any) will also be carried into low earth orbit and dock with the propulsion section as described below. For spacecraft assembly, all modules, either individually or in combination, will be carried into low earth orbit by conventional chemical rockets, similar to what is being used to carry parts, and supplies to the International Space Station (ISS). Subsequently, the reactor coolant module docks with the reactor module, in a Low Earth Orbit Propellant Depot, in a similar manner as the ISS and supply rockets do. Other modules, such as instrumentation, supplies, electrical power, scientific equipment modules, as well as the crew module (if any), will be assembled in the similar fashion. The purpose of this effort is to delineate the propulsion section of a space-based, nuclear-powered spacecraft, for deep space journeys, which will be assembled and launched from low earth orbit. The spacecraft final assembly consists of modular components delivered to low earth orbit from earth by conventional chemical rockets.

abstract

[Technical Problem] To provide a differential evacuation system capable of easily maintaining, at a low cost, a large differential pressure between a light generation chamber and an illumination optical chamber in which optical processing, e.g. exposure, is performed by using extreme ultraviolet (EUV) light generated in the light generation chamber, and yet capable of sufficiently ensuring a desired optical path.

claims

1. A method for producing a radiation protection element, comprising the steps of:arranging at least one radiation protection material between at least two layers of at least one plastic-containing element,removing at least part of the gas present between the at least two layers or positioning the at least two layers with the radiation protection material arranged therebetween in an inert gas atmosphere, andconnecting the at least two layers with each other,wherein in a region between the at least two layers a gas pressure is reduced from an initial pressure to a processing gas pressure while the at least two layers are being connected with each other, andwherein the processing gas pressure is selected such that inside a sheath of the radiation protection material formed by connecting the at least two layers a gas pressure is less than 1 bar at 23° C. 2. The method according to claim 1, wherein at least one of the layers is pressed toward the radiation protection material in order to remove at least part of the gas present between the at least two layers. 3. The method according to claim 2, wherein at least one of the layers is pressed toward the radiation protection material by means of a movable element of a welding apparatus in order to connect the at least two layers. 4. The method according to claim 1, wherein the at least two layers and the radiation protection material are placed in a processing chamber with a gas pressure reduced relative to an ambient gas pressure or with an inert gas atmosphere. 5. The method according to claim 1, wherein the at least two layers are connected with each other along a connecting line completely or partially extending around the radiation protection material. 6. The method according to claim 5, wherein the at least two layers are connected with each other along an additional connecting line not extending around the radiation protection material. 7. The method according to claim 1, wherein a carrier material and/or a shaped part are additionally incorporated between the at least two layers. 8. The method according to claim 1, wherein the at least one plastic-containing element comprises at least one plastic-containing woven fabric or a polyurethane film. 9. The method according to claim 1, wherein the at least one plastic-containing element or at least one of the two layers is translucent. 10. The method according to claim 1, further comprising the step of attaching a fixing member to the at least two layers for mounting the radiation protection element to a patient table for protection below or above the patient table or to a radiation protection cart. 11. A radiation protection element, comprising:at least one radiation protection material, anda sheath with an internal volume in which the at least one radiation protection material is arranged, wherein the internal volume has a negative gas pressure or wherein the internal volume comprises an inert gas,wherein a gas pressure is less than 1 bar in the internal volume at a temperature of 23° C. 12. The radiation protection element according to claim 11, wherein the sheath comprises a connecting line of two layers of the sheath, said connecting line completely or partially extending around the radiation protection material. 13. The radiation protection element according to claim 12, wherein the sheath comprises an additional connecting line of two layers of the sheath, said additional connecting line not extending around the radiation protection material, wherein the additional connecting line runs around an opening within the sheath. 14. A radiation protection element, comprising:at least one radiation protection material, anda sheath with an internal volume in which the at least one radiation protection material is arranged, wherein the sheath planarly abuts the at least one radiation protection material wherein a gas pressure is less than 1 bar in the internal volume at a temperature of 23° C. 15. The radiation protection element according to claim 14, wherein the sheath comprises a connecting line of two layers of the sheath, said connecting line completely or partially extending around the radiation protection material. 16. The radiation protection element according to claim 15, wherein the sheath comprises an additional connecting line of two layers of the sheath, said additional connecting line not extending around the radiation protection material, wherein the additional connecting line runs around an opening within the sheath. 17. A radiation protection apparatus, comprising:a radiation protection element or a plurality of radiation protection elements, wherein said radiation protection elements comprise at least one radiation protection material, and a sheath with an internal volume in which the at least one radiation protection material is arranged, wherein the internal volume has a negative gas pressure or wherein the internal volume comprises an inert gas. 18. The radiation protection apparatus according to claim 17, wherein the radiation protection apparatus comprises a patient table with a fixing apparatus to which the radiation protection element is mounted for protection below or above the patient table or to which the plurality of radiation protection elements is mounted for protection below or above the patient table, or wherein the radiation protection apparatus comprises a radiation protection cart to which the radiation protection element is mounted or to which the plurality of radiation protection elements is mounted. 19. A radiation protection element, comprising:at least one radiation protection material, anda sheath with an internal volume in which the at least one radiation protection material is arranged, wherein the internal volume comprises an inert gas.

047055774

summary

BACKGROUND OF THE INVENTION The present invention relates to a plate-shaped, high power, nuclear fuel element containing low enrichment uranium (5 to 20 percent weight uranium.sup.235 in the uranium component) as the fissionable material. In order to prepare for the possibility that high enrichment uranium, which is used to produce nuclear fuel elements, will not be available in the future, atomic nuclear reactors must be re-equipped to operate with nuclear fuel elements containing low enrichment uranium. Such reactors, for example, are research reactors (including material testing reactors) whose particular significance is their use as a training system for power plant reactor personnel. To be able to perform such re-equipping sensibly and economically without too much expense, studies and tests have been made as to how to change from nuclear fuel elements with about 90 percent enrichment, i.e. 90% U.sup.235 in the uranium component and about 0.4 to 1.3 g U/cm.sup.3, to fuel elements containing low enrichment uranium, i.e. .ltoreq.20% U.sup.235 in the uranium component, without having to encounter too much of a reduction in power during operation of the reactor. Retaining the reactor power seems possible only if the reduction in enrichment from 90% to 20% U.sup.235 is accomplished by correspondingly increasing the uranium density in the fuel material. It has been calculated that for lower power reactors (e.g. between 1 watt and 10 KW.sub.th.), an uranium density in the fuel material up to 2.4 g U/cm.sup.3 would have to be obtained, for medium power reactors an uranium density up to 3.3 gU/cm.sup.3 would have to be obtained, and for high power reactors an uranium density up to 5.75 to 7.03 g U/cm.sup.3, would have to be obtained. Plate elements have been proposed for re-equipping atomic nuclear reactors with low enrichment uranium. Uranium-aluminum alloys for fuel elements in plate shape and a process for manufacturing them are disclosed in German Pat. No. 1,118,471. This patent generally relates to the suppression of the formation of UAl.sub.4 in uranium-aluminum alloys. For this purpose, up to 20 atom percent, with respect to the finished product, of an element from the group including Si, Ti, Ge, Zr, Sn, Pb, In, Tl, Fe, Nb and Ga are used as an additional component. The presence of more than 0.5 atom percent of any one of the above-mentioned ternary additional elements results in a UAl.sub.3 concentration of more than 20 percent by weight and a UAl.sub.4 concentration of less than 42 percent by weight. If the proportion of the additional elements is increased, the UAl.sub.4 content is reduced. With the presence of more than 1.2 atom percent of a preferred additional element, an alloy is obtained whose UAl.sub.3 concentration is more than 60 percent by weight and whose UAl.sub.4 content is less than 8 percent by weight. The presence of 5 atom percent and more of the preferred silicon as an additional element leads to the complete suppression of UAl.sub.4 and to an UAl.sub.3 concentration of 65 percent by weight. In the past, the most complete suppression as possible of UAl.sub.4 formation in an uranium aluminide nuclear fuel element has been desired because the properties of the UAl.sub.4 posed grave problems in the further processing of the nuclear fuel. For example, UAl.sub.4 is hard and brittle, exhibits an orthorhombic lattice/and cannot be rolled into plates. If, as is customary and also disclosed in German Pat. No. 1,118,471, the uranium aluminide fuel material is produced by melting the uranium and aluminum components and pouring the melt into a mold to produce a cast shape or block, without using any additional (suppressing) elements, so much UAl.sub.4 is formed during the subsequent hot rolling process that cracks appear in the fuel material. A uniform and homogeneous distribution of the uranium in the fuel materials, however, is one of the prerequisites for a properly operating nuclear fuel element. Thus, it is impossible to initially produce UAl.sub.4 by a melting or power technology and to then process it into nuclear fuel plates by means of the well-known picture frame technique (ref. Metals and Fuels, Vol. 1, 1956, pp. 535 to 543). UAl.sub.4 -preproduced either by melting or powder technology - can only be handled by picture frame technique in a mixture with Al powder up to an UAl.sub.4 content of 20.sup.v /o (due to rolling problems). But this concentration does not satisfy the nowadays demands (.gtoreq.2.4 g U/cm.sup.3 as discussed above see page 2, last line). SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a plate-shaped high power nuclear fuel element containing low enrichment uranium as the fissionable material to reestablish the availability of fissionable material for nuclear reactors and to provide a nuclear fuel element which, because of its characteristics, completely compensates for the drawbacks of the reduction from high enrichment fuel material (90% U.sup.235 in the uranium component) to low enrichment fuel material (20% U.sup.235 in the uranium component). It is a further object of the invention to provide a method for producing such a plate-shaped high power nuclear fuel element containing low enrichment uranium. Additional objects and advantages of the present invention will be set forth in part in the description which follows and in part will be obvious from the description or can be learned by practice of the invention. The objects and advantages are achieved by means of the processes, instrumentalities and combinations particularly pointed out in the appended claims. To achieve the foregoing objects, and in accordance with its purpose, the present invention provides a plate-shaped high power nuclear fuel element containing low enrichment uranium (5 to 20 percent by weight uranium.sup.235 in the uranium component) as the fissionable material, the fuel element essentially comprising a plate of UAl.sub.4 provided with a sheath (clad) of aluminum or an aluminum alloy and impurities inherent to the manufacturing process. In accordance with a further aspect of the present invention, a process is provided for producing the plateshaped high power nuclear fuel elements according to the present invention by maintaining certain conditions to provide a plate-shaped high power nuclear fuel element with low enrichment uranium, the fuel element essentially comprising a UAl.sub.4 plate provided with an aluminum sheath. Such a process according to the present invention for producing a plate of UAl.sub.4 comprises: (a) intimately mixing a powder of low enrichment uranium or uranium compound U.sub.6 Fe (5 to 20 weight percent U.sup.235) having a particle size in the range from 0.1/.mu. to 90/.mu. with aluminum powder having a particle size in the range from 0.1/.mu. to 100/.mu. in a weight ratio range of uranium to aluminum between 1.1 U:1 Al and 2.2 U:1 Al; (b) prepressing the mixture of step a) at a pressure in the range from 300 MPa to 500 MPa at room temperature to form a plate-shaped blank; (c) inserting the blank in an Al picture frame or a picture frame of an Al alloy and welding the blank to the frame in vacuo or inert gas argon; (d) rolling the picture frame in three roll passes, a reduction in thickness of about 1 mm occurring in each of the 1st and 2nd passes, and a reduction in thickness by about 15% occurring during the third roll pass, at a temperature of 800.degree. K..+-.25.degree. K.; (e) inserting the plate in the frame after the third roll pass between two Mo sheets, one Mo sheet being at the underside of the plate and the other Mo sheet being at the upper side of the plate, inserting the framed plate together with the Mo sheets in a clamping device, and subsequently heat treating the plate at 800.degree..+-.25.degree. K. for a duration of at least 75 hours to form UAl.sub.4 in the plate. It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive of the invention. DETAILED DESCRIPTION OF THE INVENTION In the practice of the present invention, a powder mixture of aluminum and uranium or U.sub.6 Fe compound is formed and prepressed into a plate-shaped blank. In the present invention additional elements other than uranium and aluminum (and iron alternatively) are not used to form the blank. The blank is then inserted into in an Al picture-frame or a picture-frame of an Al alloy in accordance with the well-known "picture-frame technique" to provide a jacket or cladding for the blank. The aluminum alloys can be those which are conventionally used as frame material in the picture frame technique. The blank is then welded to the frame in vacuo or inert gas argon and then rolled in three roll passes at a temperature of 800.degree. K..+-.25.degree. K. It is possible to roll a powder mixture of uranium (or U.sub.6 Fe) and aluminum powder, as well as their first and second reaction products, i.e. UAl.sub.2 or UAl.sub.3, respectively. When the process according to the invention is practiced, the nuclear fuel plate is manufactured essentially before so much UAl.sub.4 has been formed that rolling becomes impossible, but an Al or Al alloy sheathed plate is obtained after the subsequent heat treatment, which plate in the end has the high weight percentage of UAl.sub.4 or practically pure UAl.sub.4 as the so-called meat (that is, the nuclear fuel material within the frame and within the plate). In this way, the substitution of the Al matrix in the prior art UAl.sub.x -Al dispersions by UAl.sub.4 practically provides a way to completely compensate for the reduction in enrichment from 90 atom percent U.sup.235 down to 20 atom percent U.sup.235. In UAl.sub.4 -Al dispersions (according to ref. Powder Metallurgy Vol. 14, 1970/71, pp. 289 to 297) it is practiced to have a continuous Al matrix phase in which the little UAl.sub.4 particles have been embedded discontinuously. This prescription is made due to the rolling procedure, in which these Al matrix only guarantees the rollability. This is why any increase in UAl.sub.4 content to compensate lower U enrichment is excluded, because it would lead to not acceptable rolling difficulties with respect to guaranteed clad thicknesses. percent U.sup.235 down to 20 atom percent U.sup.235. Since UAl.sub.4 has a high rate of defects in the crystal lattice and there therefore exists a certain amount of room in the lattice for gaseous fission products, it is expected that a UAl.sub.4 fuel element will exhibit little tendency to swell due to the formation of fission products during the lifetime of the fuel element in the nuclear reactor. The stated minimum duration of 75 hours for the subsequent heat treatment assures conversion of the uranium and aluminum powder mixture into UAl.sub.4 to more than 50 percent by weight the rest being UAl.sub.3 mainly and a little UAl.sub.2. The UAl.sub.4 content before the heat treatment, formed during heat rolling is less than 30% by weight. This conversion is increased with increasing duration of this heat treatment and almost completed at about 150 h. However, since the UAl.sub.4 formation continues during use of the fuel element in the reactor, the expansion of the heat treatment until there is complete conversion to UAl.sub.4 is no longer absolutely necessary or significant for the process according to the present invention. The significant advantages of a UAl.sub.4 fuel plate can be seen in that the operating behavior under irradiation is relatively good, that the UAl.sub.4 cannot react any longer with the aluminum sheaths because UAl.sub.4 is stable with Al, and that during reprocessing of the spent fuel elements no problems are created by additional elements other than uranium and aluminum. Expansion of the volume of the fuel element plates or deformation of the plates during the lifetime of the fuel element in the reactor are substantially reduced by the UAl.sub.4 fuel element. The present invention will now be explained in detail with the aid of an example. However, the invention is not limited to this example.

abstract

By simultaneously administering a chemical using a nuclear species releasing a single photon (a first chemical) and another chemical using a nuclear species releasing a positron to a subject, the cumulative distributions of the respective chemicals are monitored. A plural number of γ-ray detectors, which are circularly located, and a collimator covering some of the γ-ray detectors and rotates along the front face of the γ-ray detectors are provided. Also, an energy discriminating means for discriminating signals having a single photon γ-ray energy (first signals) from signals having annihilation γ-ray energy (second signals) among all of the signals detected by the detectors is provided. Further, the cumulative position of the first chemical is specified based on the signals corresponding to the γ-ray detectors covered with the rotating collimator from the first signals. On the other hand, the cumulative position of the second chemical is specified by determining the signal almost simultaneously observed form the second signals and the positions thereof on the detectors.

abstract

A pressurized water reactor (PWR) includes a vertical cylindrical pressure vessel having a lower portion containing a nuclear reactor core and a vessel head defining an integral pressurizer. A reactor coolant pump (RCP) mounted on the vessel head includes an impeller inside the pressure vessel, a pump motor outside the pressure vessel, and a vertical drive shaft connecting the motor and impeller. The drive shaft does not pass through the integral pressurizer. The drive shaft passes through a vessel penetration of the pressure vessel that is at least large enough for the impeller to pass through.

050769944

description

MODE(S) FOR CARRYING OUT THE INVENTION Illustrated in FIG. 1 is an exemplary nuclear reactor vessel 10 having a plurality of fine motion control rod drives 12 (FMCRD), only one of which is shown. In one exemplary embodiment, there are 205 FMCRDs 12 extending into the vessel 10 through the bottom thereof. Referring also to FIG. 2, an enlarged, sectional view of one of the control rod drives 12 is illustrated. The rod drive 12 includes a tubular housing 14 extending outwardly from the vessel 10 and conventionally secured thereto. The housing 14 is conventionally connected to a flanqe or manifold 16 which is disposed in flow communication with a scram line or conduit 18 which is conventionally selectively provided with high-pressure water 20 from a conventional high-pressure water accumulator 22 conventionally joined to the scram line 18. Conventionally disposed inside the housing 14 is a conventional ball screw or spindle 24, which in this exemplary embodiment includes conventional right-handed threads 26. The control rod drive 12 includes a longitudinal centerline axis 28, with the housing 12 and spindle 24 being disposed coaxially therewith. A conventional ball nut 30 is positioned over the spindle 24 and is conventionally restrained from rotating therewith so that as the spindle is rotated in a clockwise direction, the ball nut is translated in a downward direction away from the vessel 10, and when the spindle is rotated in a counterclockwise direction, the ball nut 30 is translated in an upward direction toward the vessel 10. A conventional hollow, elongate piston 32 is disposed coaxially with the spindle 24 and includes a conical base end 34 which rests on the ball nut 30, and a tip end 36 extending through a central aperture 38 in the outer end of the housing 14 into the vessel 10. The tip end 36 is conventionally coupled to a respective control rod 40 by a bayonet coupling, for example. The spindle 24 extends downwardly from the manifold 16 through a conventional electrical motor 42 which selectively rotates the spindle 24 in either the clockwise direction or counterclockwise direction. The motor 42 is electrically connected to a conventional control 44 by a conventional electrical line 46 for selectively controlling operation of the motor 42. In accordance with the preferred embodiment of the present invention, the rod drive 12 further includes a lock assembly 48 joined between the manifold 16 and the motor 42, into which assembly 48 extends the spindle 24, also referred to as an input shaft 24. The lock assembly 48 is electrically joined to the control 44 by a conventional electrical line 50 for selectively locking and unlocking, or releasing, the input shaft 24. Illustrated in more particularity in FIGS. 3 and 4 is the lock assembly 48 which includes a stationary tubular housing 52 conventionally fixedly joined to the manifold 16, and to which housing 52 is also conventionally fixedly joined the motor 42 therebelow. The housing 52 surrounds a portion of the shaft 24 which extends from the manifold 16 and to the motor 42. A gear 54 is conventionally fixedly joined to the shaft 24 in the housing 52, by a shaft key 56 for example, for rotation therewith. The gear 54 includes a plurality of circumferentially spaced gear teeth 58. A key assembly 60 includes a key housing or support 62 conventionally fixedly joined to the housing 52, by bolts for example, and having an elongate guide hole 64 which extends toward the gear teeth 58 in a plane generally perpendicular to the centerline axis 28. Slidably disposed in the guide hole 64 is a translatable elongate key 66 which has a locking tooth 68 at the distal end thereof disposed adjacent to the gear 54. The key 66 may be conventionally lubricated in the guide hole 64 to allow relatively free translation therein. For example, a pair of conventional low-friction rings 70 may be suitably secured in the key support 62 and spaced longitudinally relative to a longitudinal axis 72 of the key 66 for suspending the key 66 within the guide hole 64. The rings 70 may be formed from conventional polytetraflouroethylene (PTFE). Alternatively, conventional roller bearings could be used instead of the rings 70 for slidably supporting the key 66. A conventional first compression spring 74 is suitably disposed in the guide hole 64 in abutting contact with a proximal end 76 of the key 66 for generating a force for translating, or returning, the key 66 in the guide hole 64 toward the gear 54. A cam finger 78 is fixedly joined to the key 66 and extends transversely outwardly therefrom and generally perpendicularly to the longitudinal axis 72. A cam roller 80 is disposed adjacent to the cam finger 78 and means 82 for selectively translating or moving the cam roller 80 against the cam finger 78 are fixedly attached to the lower portion of the housing 52 by bolts, for example. The moving means 82 is effective for translating the key 66 in the guide hole 64 for positioning the key 66, including the locking tooth 68, in an engaged position shown in solid line in FIGS. 3 and 4 in abutting contact with one of the gear teeth 58 for preventing rotation of the gear 54 and the shaft 24 in a first, clockwise, direction; and in a disengaged position, shown in solid line in FIGS. 6 and 7, spaced outwardly from the gear teeth 58 for allowing unrestricted rotation of the gear 54 and shaft 24 in the first, clockwise direction, and in a second, counterclockwise direction, opposite to the first direction. As illustrated in FIG. 5, the cam roller moving means 82 in accordance with one embodiment of the present invention includes an elongate plunger 84 having a distal end 84a, conventionally rotatably joined to the cam roller 80; an intermediate portion 84b; and a proximal end 84c. A stationary actuator housing 86 surrounds the plunger intermediate portion 84b and the proximal end 84c and is conventionally fixedly joined to the lock assembly housing 52 by bolts for example. A conventional electrical solenoid 88 is suitably fixedly disposed in the actuator housing 86 and surrounds the plunger intermediate portion 84b. The electrical line 50 joins the control 44 to the solenoid 88 for providing power thereto. A second compression spring 90 is disposed between the solenoid 88 and the plunger proximal end 84c, which is in the form of an enlarged disc, for generating a force for retracting the plunger 84 away from the cam finger 78. The solenoid 88 is selectively energizable by the control 44 for magnetically drawing the plunger 84 toward the cam finger 78 and further compressing or loading the second spring 90 (as shown in dashed line in FIG. 5), and in turn translating the key 66 away from the gear 54 and further compressing or loading the first spring 74 for moving the key 66 to the disengaged position (as shown in FIG. 6). The solenoid 88 may also be deenergized by the control 44 for allowing the second spring 90 to draw the plunger 84 away from the cam finger 78 and in turn allowing the first spring 74 to urge the key 66 toward the gear 54 for moving the key 66 to the engaged position. More specifically, FIGS. 6 and 7 illustrate, in solid line, the disengaged position of the key 66 with the locking tooth 68 retracted away from the gear teeth 58, and, in dashed line, the engaged position of the key 66 with the locking tooth 68 disposed in abutting contact with one of the gear teeth 58. The cam finger 78 preferably includes a base 92 fixedly or integrally joined to the key 66 and extending through an access hole 94 in the key support 62. The cam finger 78 also includes a flat cam surface 96 inclined relative to the key longitudinal axis 72 at a first acute angle A which may be about 45.degree. , for example, and disposed adjacent to the cam roller 80 for being moved by the roller 80 for positioning the locking tooth 68 in the disengaged position. As described above, in this embodiment of the present invention, when the solenoid 88 is energized, the plunger 84 and the cam roller 80 attached thereto is urged upwardly against the cam surface 96 which forces the cam surface 96 to move transversely relative to the direction of movement of the plunger 84 which in turn causes the key 66 to slide in the guide hole 64 toward the left as illustrated in FIG. 6 away from the gear 54 to disengage the locking tooth 68 from the gear tooth 58. When the solenoid 88 is deenergized, the second spring 90 causes the plunger 84 to be withdrawn, or move in a direction away from the cam surface 96, with the first spring 74 then causing the key 66 to be returned to the engaged position with the locking tooth 68 abutting against one of the gear teeth 58. Since the second spring 90 retracts the plunger 84, the cam surface 96 is free to translate toward the roller 80, or to the right as illustrated in FIG. 6 without restriction by the cam roller 80. In the preferred embodiment of the present invention as illustrated in FIG. 6, the cam finger base 92 has a first diameter D.sub.1 and the access hole 94 has a second diameter D.sub.2 which is greater than the first diameter D.sub.1 for predeterminedly limiting travel of the key 66 between the engaged and disengaged positions. For example, as illustrated in FIG. 6, the key 66 is shown in its disengaged position with the base 92 abutting the left side of the access hole 94 and being spaced away from the right side of the access hole 94. This limits the retraction travel of the key 66. When the key 66 is disposed in its engaged position as shown in dashed line in FIG. 6, the base 92 abuts against the right side of the access hole 94 for limiting the insertion travel of the key 66 for predeterminedly positioning the locking tooth 68 relative to the gear teeth 58. Accordingly, excess retraction or insertion of the locking tooth 68 may be prevented by the preferred arrangement of the cam finger base 92 within the access hole 94. Referring again to FIGS. 6 and 7, the locking tooth 68 preferably includes a straight locking surface 98 and an inclined cam surface 100 disposed at a second acute angle A.sub.2 relative to the key longitudinal axis 72. Each of the gear teeth 58 is preferably complementary in shape to the locking tooth 68 and includes a straight locking surface 102 and an inclined cam surface 104. In the engaged position as illustrated in dashed line in FIG. 7, the locking surfaces 98 and 102 are disposed generally parallel with the key longitudinal axis 72 for preventing rotation of the gear 54 in the first, clockwise direction. The cam surfaces 100 and 104 of the locking tooth 68 and the gear teeth 58 are preferably inclined at the same second angle A.sub.2 relative to the key longitudinal axis 72 in the engaged position as illustrated in more particularity in solid line in FIG. 8 so that rotation of the gear 54 in the second, counterclockwise direction causes the gear tooth cam surface 104 to generate a longitudinal component of force F and slide against and translate the locking tooth cam surface 100 outwardly away from the gear tooth 58 for intermittently freeing successive gear teeth 58 as the gear 54 rotates in the counterclockwise direction. The first spring 74 is therefore further compressed by the gear 58 pushing the key 66 further into the guide hole 64 which thus allows the gear 58 to rotate in the counterclockwise direction even though the key 66 is disposed in its engaged position. In this operation of the key 66 and the gear 54, the gear 54 will urge the key 66 partially into the guide hole 64 until the tip of one gear tooth 58 is allowed to pass over the tip of the locking tooth 68 as shown in dashed line in FIG. 8 and designated 58a and 68a, respectively. However, as soon as one of the gear teeth 58 passes by the tip of the partially compressed locking tooth 66, the first spring 74 returns the key and locking tooth 68 to the fully engaged position with the locking tooth 68 disposed between adjacent ones of the gear teeth 58. This allows the locking surfaces 98 and 102 to face each other and abut each other in the event of any clockwise rotation of the gear 54 for preventing rotation of the gear 54 in that direction. Accordingly, in the key engaged position, counterclockwise rotation of the gear 54 intermittently displaces the locking tooth 68 from the fully engaged position as the gear 54 rotates in the counterclockwise direction with the locking tooth 68 being repeatedly urged back to its fully engaged position by the first spring 74. In this way, the control rod 40 may be further inserted into the vessel 10 by powering the motor 42 in all situations whether or not the key 66 is positioned in the engaged position. In the preferred embodiment of the invention disclosed above, the solenoid 88 is first energized to disengage the teeth 58 and 68, then the motor 42 is energized, e.g. at a fraction of a second later, during normal operation to allow the motor 42 to rotate the shaft 24 for positioning the control rod 40 without obstruction by the lock assembly 48. Upon completion of the desired rotation of the motor 42 and positioning of the control rod 40, the motor 42 is deenergized and stopped, and then the solenoid 88 is deenergized so that the locking tooth 68 engages the gear 54. If the shaft 24 then begins to unintentionally rotate, such as for example by the backflow occurrence described above, the shaft 24 will be prevented from rotating in the clockwise direction by engagement of the locking tooth 68 and a respective one of the gear teeth 58. The key 66, therefore, provides a positive lock of the shaft 24 to prevent undesirable rotation thereof, including unintentional withdrawal of the control rod 40 from the reactor vessel 10. The lock assembly 48 as described above provides a positive lock of the shaft 24 to prevent ejection of the control rod 40 from the vessel 10 and allows for relatively simple testing of the lock assembly 48 itself. More specifically, the assembly 48 may be simply tested by deenergizing the solenoid 88 for engaging the locking tooth 68 with the gear 54 and then energizing the motor 42 for rotating the shaft 24 in a clockwise direction for forcing one of the gear teeth 58 against the locking tooth 68. Since the motor 42 will be unable to rotate the gear tooth 58 past the locking tooth 68 in the clockwise direction, the motor 42 will stall, which may be conventionally observed by the control 44 for indicating the effective operation of the lock assembly 48. If the lock assembly 48 is unable to prevent clockwise rotation of the shaft 24 during testing, the control 44 can provide a suitable indication thereof, which will then result in manual inspection of the lock assembly 48 for correcting any problem that might exist. In the preferred embodiment of the invention as described above, the lock assembly 48 is positioned between the manifold 16 and the motor 42. Accordingly, the motor 42 may be removed during maintenance, and the lock assembly 48 may be engaged (i.e. de-energized) to prevent clockwise rotation of the shaft 24 during this maintenance operation. Therefore, the lock assembly 48 can replace or duplicate the function of any existing anti-rotation mechanism which is located between the manifold 16 and the motor 42. Alternatively, the moving means 82, including the solenoid 88, could be mounted to the top of the housing of the motor 42 and extend into position next to the cam finger 78 inside the housing 52. In this way, the moving means 82 may be removed with the motor 42 during maintenance for inspection and any required refurbishment. The locking tooth 68, however, will remain during such maintenance, and be moved by the spring 74 to an engaged position with the gear 54 to prevent rotation of the shaft 24. While there has been described herein what is considered to be a preferred embodiment of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein, and it is, therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention. For example, various alternate configurations of the locking tooth 68 and the gear teeth 58 may be utilized for providing the two functions of preventing clockwise rotation of the shaft 24 in the engaged position while allowing intermittent counterclockwise rotation of the shaft 24. Furthermore, although the cam finger 78 and the cam roller moving means 82 are generally colinearly aligned with each other, parallel to the longitudinal centerline axis 28, and perpendicularly to the key 66 for providing a more compact assembly for reducing space requirements thereof, alternate configurations thereof may be utilized for extending and retracting the key 66 as space permits. Accordingly, what is desired to be secured by Letters Patent of the United States is the invention as defined and differentiated in the following claims:

062927515

claims

1. A method for correcting errors in position derived from an inertial measurement unit (IMU), comprising the steps of: performing a first zero velocity update at a time when the IMU is at rest; recording the time and position of the IMU at a subsequent start of a period of interest after the first zero velocity update; recording the time and position of the IMU at the end of the period of interest; performing a second zero velocity update at the end of the period of interest with the IMU at rest, and then recording a velocity indicated from the IMU; and deriving an accumulated error in position the deriving comprising a) approximating errors in velocity by a function of time with a parameter determined from the recorded indicated velocity, and b) integrating the function over the period of interest to determine the accumulated error in position during the period of interest. performing a first zero velocity update at a time when the vehicle is at rest; recording the time and position of the vehicle at a subsequent start of a period of interest after the first zero velocity update, wherein the start of the period of interest is triggered by the detection of a mine; recording the time and position of the vehicle at the end of the period of interest, wherein the end of the period of interest is triggered by the positioning of the vehicle such that the mine is behind the vehicle and in close proximity thereto; performing a zero velocity update at the end of the period of interest with the vehicle at rest, and then recording a velocity indicated from the IMU; and deriving an accumulated error in position the deriving comprising a) approximating errors in velocity by a function of time with a parameter determined from the recorded indicated velocity, and b) integrating the function over the period of interest to determine the accumulated error in position during the period of interest. performing a first zero velocity update at a time when the IMU is at rest; recording the time, t.sub.1, and position, P.sub.1, of the IMU at a subsequent start of a period of interest after the first zero velocity update; recording the time, t.sub.2 and position, P.sub.2, of the IMU at the end of the period of interest; performing a second zero velocity update at the end of the period of interest with the IMU at rest, and then recording a velocity, V.sub.2, indicated from the IMU; and deriving an accumulated error in position, .DELTA.P.sub.e, according to the following formula: an inertial navigation system (INS) comprising an inertial measurement unit (IMU) mounted upon said vehicle; a processor for determining errors in position derived from said IMU by processing recorded data obtained according to the following steps: (1) performing a first zero velocity update at a time when the IMU is at rest; (2) recording the time and position of the IMU at a subsequent start of a period of interest after the first zero velocity update; (3) recording the time and position of the IMU at the end of the period of interest; (4) performing a second zero velocity update at the end of the period of interest with the IMU at rest, and then recording a velocity indicated from the IMU, and (5) deriving an accumulated error in position the deriving comprising a) approximating errors in velocity by a function of time with a parameter determined from the recorded indicated velocity, and b) integrating the function over the period of interest to determine the accumulated error in position during the period of interest. 2. The method of claim 1, wherein the function is a straight line with a slope proportional to the magnitude of the recorded indicated velocity. 3. The method of claim 1, where the IMU is mounted upon a vehicle for detecting mines and where the period of interest begins when a mine is detected and ends when the vehicle is positioned such that the mine is behind the vehicle and in close proximity thereto. 4. The method of claim 1, wherein a parameter of the function is determined by setting the function equal to the recorded indicated velocity and setting the time equal to the end of the period of interest. 5. The method of claim 1, further comprising the step of providing a computer processor for performing the step of deriving the accumulated error in position. 6. A method for determining the position of a mine relative to a vehicle upon which is mounted an inertial measurement unit (IMU), comprising the steps of: 7. The method of claim 6, wherein the function is a straight line with a slope proportional to the magnitude of the recorded indicated velocity. 8. The method of claim 6, wherein a parameter of the function is determined by setting the function equal to the recorded indicated velocity and setting the time equal to the end of the period of interest. 9. The method of claim 6, further comprising the step of providing a computer processor for deriving the accumulated error in position. 10. A method for correcting errors in position derived from an inertial measurement unit (IMU), comprising the steps of: 11. The method of claim 10, further comprising the step of computing a change in position, .DELTA.P.sub.a, of the IMU according to the following formula: EQU .DELTA.P.sub.a =(P.sub.2 -P.sub.1)-.DELTA.P.sub.e. 12. A mine detection vehicle for determining the position of a mine, comprising:

050664530

summary

This invention relates to the control of coolant flow through a nuclear reactor fuel assembly, and is particularly but not exclusively concerned with controlling the rate of flow of liquid metal coolant through a fuel assembly of a fast neutron nuclear reactor, (hereinafter referred to as "a Fast Reactor"). In a nuclear reactor, comprising numerous individual fuel elements, regions of different coolant temperature may develop giving rise to thermal stresses in the core structure of the reactor. To avoid these stresses it is desirable that the nuclear fuel within the reactor operates as far as possible at a uniform temperature, and to achieve this the rate of flow of coolant through different fuel elements of the reactor is usually controlled. Variations in temperature within the reactor are a particular problem in Fast Reactors which contain both fissile fuel and fertile or breeder fuel, since the heat output from the breeder fuel starts at a low level but rises over a period of time to a substantially greater level. Consequently, the temperature of the liquid metal coolant emerging from a Fast Reactor fuel assembly containing breeder fuel rises during the operation of the Reactor towards the temperature of the fissile fuel. It is desirable to stabilise the temperature of the coolant, for example at about 550.degree. C. in a Fast Reactor, so as to maintain efficient heat transfer between the coolant and the fuel, and optimum fuel life. In general, the invention provides an apparatus for controlling the flow of coolant through a nuclear fuel assembly, the apparatus comprising a variable flow restrictor locatable in the fuel assembly, means responsive to neutron radiation at a location in the fuel assembly in a manner to cause neutron induced growth of the responsive means, and a connecting means for connecting the neutron radiation responsive means to the variable flow restrictor for controlling the flow of coolant through the assembly. Preferably, the variable flow restrictor comprises a plurality of longitudinally aligned ducts, and a plugging means having an array of plugging members locatable in some of the ducts, the plugging members being of different lengths so that longitudinal displacement of the plugging means by the connecting means progressively opens or closes some of the ducts. Conveniently, the neutron radiation responsive means comprises at least one elongate member supportable by the fuel assembly and arranged to support an elongate portion of the connecting means, the elongate member comprising at least one material having a greater neutron-induced growth property than that of the elongate portion so as to cause longitudinal displacement of the connecting means as the elongate member grows under neutron irradiation. The elongate member might comprise a rod member extendable within a said elongate portion of tubular form. The rod member might comprise a plurality of rod portions disposed one upon the other, at least some of the rod portions having different neutron-induced growth properties than other said rod portions so as to produce a required longitudinal growth of the rod member under the neutron radiation. Desirably, the rod member is arranged so that an initial longitudinal neutron-induced growth is necessary before the rod member supports the elongate portion. Alternatively, some of the rod portions might be mechanically treated, for example cold worked, so as to introduce a delay in the onset of growth in the rod portions under the neutron irradiation. The elongate member might be of tubular form and the elongate portion might comprise a rod element extending within said tubular elongate member.

abstract

A neutron generator has a pre-moderator block of moderating material, an acceleration chamber, a vacuum pump evacuating the acceleration chamber to a moderately high vacuum, a plasma ion chamber opening into the acceleration chamber through an ion extraction iris, a gas source providing deuterium gas to the plasma ion chamber, a microwave energy source ionizing the gas in the plasma ion chamber, a primary and a secondary isolation well extending into the pre-moderator block, a water-cooled titanium target disk positioned at a lower extremity of the primary isolation well, the target disk biased to a substantial negative DC voltage, and electrically grounded metal cladding covering surfaces of the pre-moderator block. Ions extracted through the ion extraction iris are accelerated to bombard the titanium target producing energetic neutrons that pass through and are moderated by the pre-moderator block.

summary

summary

summary

description

1. Field of the Invention The present invention relates generally to design and operation of nuclear reactors, and more particularly to a method of determining a margin to an operating limit of a nuclear reactor. 2. Description of the Related Art During the operation of a boiling water reactor (BWR) or pressurized water reactor (PWR), a continuous monitoring of all operating parameters and resulting thermal limits is performed. For example, percent rated power, percent rated flow, inlet moderator temperature, core pressure, and any positioning of control blades are monitored in order to identify the instantaneous status of the reactor. Also, instrumentation within the reactor core helps monitor reactivity, which maps to corresponding operating responses in parameters such as critical power ratio (CPR), Maximum Average Planar Linear Heat Generation Rate (MAPLHGR), and Maximum Fraction of Linear Power Density (MFLPD), each of which represents a core safety thermal limit on nuclear fuel and which may also be referred to as power-related limits on nuclear fuel. These measured thermal responses are compared to their corresponding operating limits to provide the current margin to the operating limits. The continuous monitoring of core parameters and corresponding margins to operating limits is done throughout the core energy cycle. A computer which performs this monitoring is called a “process computer”. At a minimum, snapshots of the reactor status and resulting margins to operating limits such as the thermal limits above and/or operating limits are processed once per day and stored, typically as an electronic ASCII file. In order to maintain models of the reactor for use in projection work, development of subsequent design cycles, and/or to provide support for current operating issues, designers or plant operators maintain an off-line (not on the process computer) three dimensional (3-D) simulation of the reactor that resembles the actual operation of the given cycle in the actual reactor core. There are typically differences between the thermal and reactivity margins determined by the process computer (measured margins to operating limits) and those predicted by the off-line model (predicted margins). These differences are caused by a variety of factors, including inadequacies in simulator models, imperfect modeling of the actual plant operation, uncertainties in operating parameters, uncertainties in tip measurements, etc., as well as other unknown uncertainties. Differences between the on-line and off-line margins (i.e., to thermal, reactivity and/or power-related operating limits) determinations force plant operators to require additional margin to these operating limits, so as to insure trouble free operation. Additional margin can be obtained by making changes to the operational parameters, and/or by selection and positioning of different rod patterns. However, the cost of such changes typically is a loss of power or fuel cycle efficiency. Moreover, a “larger than needed” margin requirement has an adverse economic impact on the plant. The determination of sufficient operating limit margins and predicted trends for expected operating limits and uncertainty exposure dependent biases is a complex problem for design and operation of a nuclear reactor. From the time of the first nuclear reactor it has been observed that the predicted results from computer models and the observed reality (actual operating limits as determined from on-line operation) can oft-times be significantly different for these important dependent variables (i.e., operating limits). To protect against these differences, engineers have developed standard design margins or historical design margins that are to be used to account for or “cover” these differences. However, these standard design margins are crude at best. Sometimes, the historical required design margin is inadequate, resulting in manipulation of control rods during operation in order to regain lost margin. If rod pattern changes do not alleviate or correct the problem, plants have been even known to have to de-rate (lower power production). Either solution is extremely costly to the fuel cycle efficiency and can cost millions of dollars in lost revenue. Additionally, the historical design margin is occasionally inappropriately conservative, thereby resulting in a reduction in possible fuel cycle efficiency. An exemplary embodiment of the present invention is directed to a method of determining an operating margin to a given operating limit in a nuclear reactor. Operational plant data is accessed during a current operating cycle from an on-line nuclear reactor plant to be evaluated, and reactor operation is simulated off-line using the operational plant data to generate simulation results including predicted dependent variable data representative of the given operating limit. The predicted dependent variable data from the simulation results is normalized for evaluation with normalized historical dependent variable data from each of a plurality of stored operating cycles of nuclear reactor plants having a similar plant configuration to the plant being evaluated. A time-dependent average bias and a time-dependent uncertainty value for the predicted dependent variable data is determined using the normalized historical dependent variable data, and a risk-tolerance level for the plant being evaluated is obtained. An operating margin to the given operating limit is determined based on the determined time-dependent average bias value and time-dependent uncertainty value, so as to satisfy the risk-tolerance level of the evaluated plant. FIG. 1 is a block diagram of an example arrangement for data gathering and calculations associated with the exemplary methodology described herein. In general, and as to be discussed in more detail below, a process computer 120 is used to access plant operational data, including margins to operating limits from an on-line and operating reactor plant 110. This data may be stored as an ASCII file as discussed above, but in an alternative embodiment may be directly stored in a database 130 (on-site or off-site) in operative communication with process computer 120. The process computer 120 is well-known in the art and may be embodied as any system, device, or computer that monitors plant operation and provides information related to the instantaneous performance of an operating nuclear reactor. Database 130 may be a relational database such as an Oracle 8i Alpha ES 40 relational database server. Database 130 may contain a number of subordinate databases that handle all the necessary data and results in order to implement the example method of the present invention. The operational data may be used to model the on-line reactor plant being evaluated, matching the operating parameters at the current exposure in cycle, so as to execute an off-line simulation at off-line simulator 140. The off-line simulator may be well-known executable 3D simulator program such as PANACEA, LOGOS, SIMULATE, POLCA, or any other known simulator software where the appropriate simulator drivers have been defined and coded, as is known. The simulation provides results including predicted margins to given operating limits, which hereafter may be referred to as “predicted dependent variable data”. The predicted dependent variable data may be stored in database 130, and is also provided to a calculation processor 150, which is to be used for determining a revised operating margin to a given operating limit. Processor 150 may be any processor capable of performing relatively complex calculations. Any PC or laptop driven by a Pentium-based microprocessor chip or an equivalent processing entity may suffice as a calculation processor 150. The calculations performed by processor 150 are to be described in further detail hereafter. Once the margin value has been calculated, this data may be used by processor 150 to determine revised operating parameters for the on-line plant being evaluated, and may be communicated to plant operators at plant 110 so as to change operating parameters (i.e., control rod sequence, core flow, power level, etc.) at the current exposure (time in operating or energy cycle) or at a future point in the current operating cycle of the plant 110. These margin calculations may be performed continuously at any desired frequency or periodicity, in an effort to maximize plant 110 efficiency, for example. As shown in FIG. 1, data flow between process computer 120, off-line simulator 140 and processor 150 may be two way with database 130 so that calculations or results may be continuously stored, and/or so that data may be accessed from database 130. FIG. 2 is a process flow diagram to explain an example method of determining an operating margin to a given operating limit. Occasional reference may be made to FIG. 1 for the following discussion. During the operation of plant 110, operating conditions and monitored parameters are accessed (210) during a current operating cycle from plant 110 by the process computer 120 and saved to database 130. The independent variables (i.e., rod pattern, operating conditions such as reactor power and core flow, plant configuration, mechanical conditions, core conditions, enrichment and gadolinium properties, cycle exposure, etc.) may also be saved to database 130 in order to correlate any potential trends between simulation biases and core configuration. Similarly, all monitored results or dependent variable data such as Maximum Fraction of Limiting CPR (MFLCPR), MFLPD, MAPLHGR, cold shutdown margin, reactivity-related parameters (such as Hot Eigenvalue, etc.), and predicted margins to these operating limits are also saved to database 130. MFLCPR is a power-related fuel limit. MFLCPR measures the allowable margin between operating conditions and a limit to ‘dryout’, where coolant in the core can no longer remove heat at a sufficient rate, such that fuel and clad temperatures start to increase rapidly. This boiling transition phenomenon, which can lead to a temperature excursion in BWR fuel, is referred to as dryout. Accordingly, plant operating conditions that are retrieved by the process computer 120 may be understood as independent variables, and monitored or measured operating limit data (thermal and power-related limits and margins thereto) retrieved by the process computer 120 is actual dependent variable data. These independent and dependent variables from one or more exposure points in the current operating cycle may thus be saved or stored in database 130. With the above information saved to the database 130, a reactor simulation input file can be created or prepared. The simulation input file uses identical independent variables as described above and may be stored in an electronic file format (i.e., ASCII) that is recognized by the identified core simulation software program (off-line simulator 140). Once the input file is prepared, the off-line simulator 140 executes its program to simulate reactor operation of plant 110 off-line and to generate a prediction of the dependent variables, referred to as predicted dependent variable data. The predicted dependent variable data may be understood as a nominal estimate of future results, and therefore may be used to calculate a nominal estimate of operating margins, but does not take into account any uncertainty for the predictions. FIG. 6 is a graph of predicted eigenvalue versus normalized time to illustrate differences in the predicted margin as a result of simulation and the margin as determined by the example methodology herein. Ideally, the off-line simulated dependent variables (predicted margins to limits such as MFLCPR, MFLPD, MAPLHGR, etc.) and the measured or actual dependent variable data (actual margins to MFLCPR, MFLPD, MAPLHGR, etc.) from plant operation would be identical. However, due to several (or more) of the factors identified above, these typically are not. At this time, the predicted dependent variable data is normalized (230) with respect to time (exposure) relative to anticipated EOC (End of Cycle). In other words, the data is normalized by processor 150 on a BOC (Beginning of Cycle) to EOC time range of 0.0 (BOC) to 1.0 (EOC). In doing so, the normalized predicted dependent variable data can be evaluated with results (such as normalized historical dependent variable data) from many reactor simulations of other plant cycles, with the normalized data being stored in database 130. Database 130 contains a substantial collection of reactor simulations, and hence, includes a substantial amount of historical dependent variable data from reactor simulations of operating cycles in other reactor plants. For example, because the assignee has provided fuel and engineering services for approximately 30 BWR's over approximately 20 years, almost 400 complete exposure depletion cycles are available (given an approximate 1 ½ year average cycle length). A collection of data for 400 operating cycles is a significant collection of information for evaluating operation of nuclear reactors. This information can be utilized by the example methodology of the present invention and for the resulting predictions therefrom. For example, as part of step 230, the processor 150 retrieves historical simulation data from plants having a similar plant configuration to plant 110. This historical dependent variable data is also normalized with respect to time on the 0.0 to 1.0 scale for evaluation, although any other normalized scale could be employed, as would be evident to one of skill in the art. While all of this data has been normalized with respect to time (exposure) so that all data ranges from 0 to 1 (0.0=BOC, 1.0=EOC), it is recognized that some of the operating strategies for the various stored operating cycles are dissimilar. Consequently, it may be desirable to filter the larger collection of cycle data in database 130 to collect a sub-set of data that is most similar in plant operation style to the specific plant 110 being evaluated. Filtering parameters may include, but are not limited to: cycle length, power density, average gadolinia concentration, flow strategies, loading strategies, etc. Thus, the filtered historical data incorporates data from similar plant operation styles. As a result of the above filtering process, predicted uncertainties may become smaller, and may be used to improve fuel cycle efficiency. Similarly, it may also be desirable to provide correlation to the above continuous variables by way of least squares, neural networks, or any other trend capturing mathematics. In doing so, a larger set of data can be incorporated and global trends may be included, possibly resulting in a further reduction in predicted uncertainties, and may be used to improve fuel cycle efficiency. FIG. 3 is a graph of calibrated time-dependent bias for a given operating limit versus normalized time to explain the calculation of a time-dependent average bias value in accordance with the example method. FIG. 4 is a graph of time-dependent uncertainty versus normalized time to explain the calculation of the time-dependent uncertainty value in accordance with the example method. In general, the normalized historical dependent variable data will be used by processor 150 in order to calculate a time-dependent average bias value that will provide a predicted expected bias at all future times in the cycle for the predicted dependent variable data (such as a given margin to a given operating limit) calculated as a result of the off-line simulation of plant 110. In FIG. 3, there are shown time-dependent bias curves for 30 identified operating cycles of plants having a similar plant configuration to plant 110. This information is retrieved from database 130 by processor 150. For each historical cycle being evaluated, a bias value for the historical dependent variable data is known and has been calculated in advance (and stored in database 130). The known bias value at a given exposure point, for a given stored historical operating cycle, represents a difference between the measured and the predicted operating limit at that exposure point for the given historical cycle. Once the selected data has been collected for all 30 cycles between 0.0 to 1.0 (the data here being the known bias values along all exposure points for each of the historical dependent variable data of each historical operating cycle), the data is calibrated relative to the current time in operation of the operating cycle of plant 110 being evaluated, e.g., the point in cycle time being evaluated. For example, and referring to FIG. 3, if cycle operation of plant 110 is approximately 10% complete (t=0.10), all data (all bias values) at all time intervals should be calibrated upwards or downwards until the value at t=0.10 is set to zero on the y-axis (ratio of measured minus predicted dependent variable). Calibrations to bias values after t=0.10 would be adjusted to correct for the calibration. FIG. 3 illustrates how the multiple curves (30 curves) are calibrated at t=0.10. Whereas the above example identifies calibration by way of addition-subtraction to set values to zero at t=0.10, calibration can also be performed using multiplication-division to set values to one at t=0.10. Calibration by way of addition-subtraction or multiplication-division may be selected by the mathematical processes which provide the smallest prediction of future uncertainty. As can be seen from FIG. 3, all lines go through zero at t=0.10. This is because at any given current time (t=0.10 in this example) there is a known exact bias between the off-line simulation results (predicted margin) and operating plant-measured result (actual margin to the given operating limit). From the calibrated curves, two time-dependent curves are determined. First, the time (exposure) dependent bias value is determined (240) by averaging all of the future data (t>0.10). In the above example, the data is somewhat random and the time dependent bias for all future times is approximately 0.0. In FIG. 3 this time dependent bias value is shown as curve 300, which is the average of the bias values of the 30 curves at each evaluated exposure point between t=0.1 (current time) and t=1.0 (future time). Accordingly, to calculate the time dependent bias value (curve 300), the normalized historical dependent variable data is calibrated to force the known bias values to the current exposure point in the operating cycle of plant 110. The time-dependent average bias value is this determined by averaging all the bias values of the normalized historical dependent variable data at each of the exposure points, as calibrated from the current exposure point in plant 110 being evaluated. Next, and as shown in FIG. 4, a time (exposure) dependent uncertainty is determined (250). This is determined by calculating the standard deviation at all times greater than the present time (in this example, all times greater than t=0.10). An example of a time dependent uncertainty curve is shown in FIG. 4. The curve in FIG. 4 represents the standard deviation at each exposure point of the time-dependent bias curve 300 in FIG. 3. In FIG. 4, it can be seen that the generally parabolic shape of the curve indicates that the uncertainty in the bias value goes up over time. Thus, if the designer knows where he is at any point in the cycle (past or present), such as at t=0.2, the curve can be used to predict the uncertainty in the bias value for the predicted dependent variable data at any other future time in the cycle. An observation can be made by studying the curves in FIGS. 3 and 4 in greater detail. There is an exact and simple correlation that relates all of the uncertainties, represented as “σ”, of a random system to time. If the uncertainty σ of the system is known at any point (example t=ref), the uncertainty a of any other point can be calculated by the following set of equations in (1):σtarget=σref[ttarget/tref]1/2 or rewritten as,σ2targettref=σ2refttarget or rewritten as,σ2target/σ2ref=ttarget/tref  (1) The last equation of (1) illustrates the relation used to determine required future dependent variable uncertainties for a modeled independent variable measured-to-predicted system, In (1), ttarget=desired time of desired uncertainty, tref=reference time where uncertainty of system is known, σref=reference uncertainty at reference time (tref) and σtarget=desired uncertainty at desired time (ttarget). As shown by the last equation of (1), relative time therefore equals relative uncertainty and relative uncertainty equals relative time. Therefore utilization of this relation can provide a determination of future uncertainties. Consequently, given the amount of future time that is required (i.e. the next control blade sequence interval) and data from a reference time, a good estimate of the required future uncertainty can be determined. The combination of this information can provide maximum fuel cycle efficiency while simultaneously providing event-free operation. Extensive computer experiments have been performed to confirm that expression (1) is exact as the number of uncertainty curves for nuclear reactors increase to infinity. FIG. 5 is a graph to assist explanation of how a margin for a given operating limit is calculated based on the time-dependent bias value and time-dependent uncertainty value so as to satisfy a risk-tolerance level set for the plant being evaluated. Now that a time dependent bias (240) and a time dependent uncertainty (250) has been determined, this information can be used to determine a required or revised margin to the given operating limit (270). This calculation is based on obtaining a risk-tolerance level 260 for the plant 110. The risk-tolerance level may be understood as a desired predictability of meeting the operating limits of a customer's reactor plant, or in other word, a probability of an event not occurring in plant 110 during a given period in the current operating cycle. For example if the number of historical data points is large (such as greater than 30) and the customer wanted a given probability (i.e. 90%, 95%, 99%, 99.9%, etc) of operating their nuclear reactor with fixed rod patterns for the first sequence of cycle operation, the following margin in FIG. 5 would be required. Where a smaller set of historical data points is used or specific confidence levels are required, multiplier constants known as probability K values should use appropriate confidence corrections. In FIG. 5 (t=0), curve A represents the actual operating limit of any required thermal or power-related result (MFLCPR, MFLPD, MAPLHGR, etc). This is a line that should not be exceeded during the operation of the plant 110. The curve B represents the needed design target to make sure the operating limit is not violated at any future time. If the customer wanted to make sure that a first sequence of operation (t=0 to t=0.1) would not require any rod pattern modification, they would utilize the required margin prediction at t=0.1. In FIG. 5, a design target operating limit of 0.971 would provide a sufficient margin to ensure, with 99.0% probability, that rod adjustments will not be needed (see curve C at t=0.1). Similarly, in FIG. 5 a design target of 0.953 would be required to ensure, with 99.9% probability, that rod adjustments will not be required. The 99.9% represents the risk tolerance level of the customer for this “non-event”. Accordingly, the probability value or risk-tolerance level is used to determine the multiplier constant K that is to be multiplied by the time-dependent uncertainty σ, or σtarget=Kσref, where σref is the known reference uncertainty at a given point in time, which provides a prediction of the uncertainty at any point in the cycle. In either case, a customer specific or plant specific solution may be easily determined. In most cases, determining an operating margin based on a desired predictability of meeting the operating limit may provide additional margin for greater operating flexibility and superior fuel cycle efficiency (higher than the historic design target limit of curve D). In any case, the example methodology may reflect a more knowledgeable plan for reactor operation. Based on the revised margin calculation at 270 by processor 150, the designer can then revise plant operating parameters (280) using processor 150, either by hand (manual calculations) or using an optimization routine to determine the desired rod pattern, core flow, power level, etc. Any suggested changes may be forwarded to operators of plant 110 to change the operating conditions during the current cycle, if necessary or desired. FIG. 6 is a graph of predicted eigenvalue versus normalized time to illustrate differences in the predicted margin as a result of simulation and the margin as determined by the example methodology herein. FIG. 6 illustrates an actual calculation of hot eigenvalue for power operation and cycle length considerations. The initial conditions where to evaluate future eigenvalue predictions at all exposure points greater than 20% into the cycle (T=0.2) with a customer provided risk-tolerance level of 75%. Therefore, the customer would want to be 75% certain of having the required reactivity (i.e., power and desired cycle length). The multiplier factor K based on this probability, taken from any statistics book, was 0.68. The known actual eigenvalue (normalized) at T=0.2 is 1.0050. In FIG. 6, curves were generated for the nominal predicted eigenvalue and for the 75% probability of non-event eigenvalue. Because there are only seven groupings of data or data sets in this example, the illustrated curves are somewhat non-continuous in the y-axis. Also shown is a 10 point average of the 75% eigenvalue prediction, which simply smoothes the calculated results. To generate the curves, raw dependent variable data (eigenvalue data with known bias values) at exposure points across each of seven (7) different operating cycles of plants having the closest configuration to the plant of interest were normalized. The normalized data from the seven cycles was calibrated to T=0.2, and the data then was aligned so that there was a data point for each of the seven eigenvalue data sets between 0.0 to 1.0 at 0.02 increments. The time-dependent bias and uncertainty values were calculated at each 0.02 increment from the seven eigenvalue data sets. In FIG. 6, the bias value at T=0.4 was calculated at −0.0015 and the uncertainty value at T=0.4 was calculated at 0.0012. Accordingly, the predicted eigenvalue at T=0.4 is 1.0050−0.0015=1.0035. The eigenvalue at the 75% probability is determined by first multiplying the uncertainty by K, thus 0.0012*0.68=0.0008, then adding this to the predicted eigenvalue of 1.0035 to provide a more conservative prediction of 1.0043 at T=0.4, as shown in FIG. 6. Therefore, the above example shows the desired off-line simulation hot eigenvalue for a customer that desires to be 75% certain of having the required exposure dependent reactivity (i.e. power and desired cycle length). The example embodiments of the present invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as departure from the spirit and scope of the example embodiments of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

description

The present invention relates to a radiation detecting attachment, a working machine, and a sorting method. Patent Literature 1 discloses a working machine including a radiation detector for detecting radiation. In this working machine, the radiation detector is attached to an arm body that supports a bucket (working attachment) movably, and radiation of an object of detection in the bucket can be detected. Patent Literature 1: Japanese Patent Application Laid-Open No. 2012-229945 In the configuration as shown in Patent Literature 1, however, an object of detection that can be detected by the radiation detector is limited to an object in the bucket. That is, since a size of the object of detection and a distance to the object of detection are limited in Patent Literature 1, it is difficult to use such a radiation detector in a versatile manner. In light of this, the present invention has been made to solve the aforementioned problem. An object of the present invention is to provide a radiation detecting attachment, a working machine, and a sorting method capable of using a radiation detector efficiently and in a versatile manner. The present invention has solved the aforementioned problem by providing a radiation detecting attachment including one or more radiation detectors configured to detect radiation from an object of detection, attached removably to a working machine, in which the radiation detecting attachment is supported by the working machine movably when the radiation detecting attachment is attached to the working machine, when a plurality of the radiation detectors are included, the radiation detecting attachment includes a frame body supporting the plurality of the radiation detectors, and a distance between at least one radiation detector and another radiation detector is changeable by moving of a moving element included the frame body. Or, the present invention has solved the aforementioned problem by providing a radiation detecting attachment including one or more radiation detectors configured to detect radiation from an object of detection, attached removably to a working machine, in which the radiation detecting attachment is supported by the working machine movably when the radiation detecting attachment is attached to the working machine, including a plurality of claw members capable of coming closer to each other and separating from each other. That is, in the present invention, the radiation detecting attachment including the one or more radiation detectors is removably attached to the working machine. Furthermore, the radiation detecting attachment is supported by the working machine movably. This imposes less limitation on the size of the object of detection and enables a distance to the object of detection and a positional relationship with the object of detection to be adjusted appropriately. The radiation detecting attachment may be supported by an arm body of the working machine swingably. In this case, the positional flexibility of the radiation detecting attachment can be further broadened. When a plurality of the radiation detectors are included, the radiation detecting attachment may include a frame body supporting the plurality of the radiation detectors, and a distance between at least one radiation detector and another radiation detector is changeable by moving of a moving element included the frame body. In this case, radiation can be detected efficiently by changing a clearance between the radiation detectors in accordance with a size of the object of detection. Or, a plurality of claw members capable of coming closer to each other and separating from each other may be included. In this case, a distance to the object of detection can be stabilized and the object of detection can be accurately identified for the detected amount of radiation by grasping the object of detection with the claw members, for example. At least one of the radiation detectors may be supported via an elastic member. In this case, the possibility of causing failure, breakage, or the like, of the radiation detector can be reduced even if a large external force is applied to the radiation detector. One or more discharge nozzles disposed to be capable of replacing pre-replacement air between the radiation detector and a detection area of the object of detection may be included, and post-replacement air having a reduced amount of a radioactive substance contained in the pre-replacement air may be discharged from the one or more discharge nozzles. In this case, an amount of radiation from the object itself of detection can be accurately detected by reducing the influence of an air dose. The present invention can be viewed as a working machine to which the above-described radiation detecting attachment is attached. In the working machine, a driver's cab may be equipped with a display device capable of displaying an amount of radiation based on an output of the radiation detector. In this case, an operator in the driver's cab can directly check the amount of radiation. In the working machine, the display device can display mapping associating the amount of radiation with the detection area of the object of detection. In this case, a level of the amount of radiation can be determined for each detection area. Therefore, in demolishing the object of detection, a required space to dispose waste resulting from the demolition, its demolition procedure, or the like can be predicted before starting the demolition. That is, there is no need to separately check the demolition procedure or the amounts of radiation after the demolition, thereby enabling an improvement in working efficiency. The present invention can be viewed as a sorting method for sorting, with a radiation detecting attachment including one or more radiation detectors configured to detect radiation from an object of detection, attached removably to a working machine, the object of detection on the basis of an amount of the radiation, the method including: a step of supporting the radiation detecting attachment by the working machine and bringing the radiation detecting attachment closer to each of detection areas of the object of detection; a step of obtaining an amount of radiation of the detection area on the basis of an output of the radiation detector; a step of detaching the radiation detecting attachment from the working machine and attaching a working attachment, capable of dividing the object of detection into each of the detection areas, to the working machine; and a step of dividing the object of detection with the working attachment in accordance with the obtained amount of radiation. The sorting method may include a step of replacing pre-replacement air between the radiation detector and the detection area with post-replacement air having a reduced amount of a radioactive substance contained in the pre-replacement air before obtaining the amount of radiation of the detection area. The sorting method may include a step of displaying mapping associating the obtained amount of radiation with the detection area. The sorting method includes: a step of detaching the radiation detecting attachment from the working machine and attaching a working attachment, capable of dividing the object of detection into each of the detection areas, to the working machine; and a step of dividing the object of detection with the working attachment in accordance with the obtained amount of radiation. Then, since a vehicle body itself of the working machine is shared, the object of detection can be easily sorted even in a narrow working site. Or, when the radiation detecting attachment includes a plurality of claw members capable of coming closer to each other and separating from each other, the sorting method includes a step of dividing the object of detection with the working attachment in accordance with the obtained amount of radiation. Then, no other working machine is required, and replacement work between the radiation detecting attachment and the working attachment can be eliminated. Thus, the object of detection can be quickly sorted even in a narrow working site. The present invention can be viewed as a sorting method for sorting, with a radiation detecting attachment including one or more radiation detectors configured to detect radiation from an object of detection, attached removably to a working machine, the object of detection on the basis of an amount of the radiation, the method including: a step of preparing a conveying unit capable of conveying a plurality of the objects of detection; a step of detaching the radiation detecting attachment from the working machine and disposing the radiation detecting attachment near the conveying unit so that radiation of the plurality of the objects of detection moving on the conveying unit can be detected sequentially; and a step of obtaining an amount of radiation for each of the plurality of the objects of detection moving on the conveying unit. The sorting method may include a step of replacing, when obtaining the amount of radiation for each of the objects of detection, pre-replacement air between the radiation detector and the object of detection with post-replacement air having a reduced amount of a radioactive substance contained in the pre-replacement air. The sorting method may include: a step of detaching the radiation detecting attachment from the working machine and attaching a working attachment, capable of supporting the object of detection, to the working machine; and a step of disposing the plurality of the objects of detection on the conveying unit with the working attachment in order to detect the radiation. In this case, since a vehicle body itself of the working machine is shared, the objects of detection can be easily disposed on the conveying unit even in a narrow working site. When the working machine simultaneously includes the radiation detecting attachment and a working attachment capable of supporting the object of detection, the sorting method may include a step of disposing the plurality of the objects of detection on the conveying unit with the equipped working attachment in order to detect the radiation. In this case, no other working machine is required, and replacement work between the radiation detecting attachment and the working attachment can be eliminated. Thus, the object of detection can be easily moved from the conveying unit and sorted even in a narrow working site. The sorting method may include a step of displaying the obtained amount of radiation for each of the objects of detection. In this case, the object of detection can be easily sorted in accordance with the amount of radiation. The sorting method may include a step of sorting the object of detection with the working attachment in accordance with the obtained amount of radiation. In this case, since a vehicle body itself of the working machine is shared, the object of detection can be easily moved from the conveying unit and sorted even in a narrow working site. According to the present invention, the radiation detector can be used efficiently and in a versatile manner. An example of a first embodiment of the present invention will be described below in detail with reference to the drawings. First, a configuration of a working machine 100 according to the present embodiment will be described with reference to FIG. 1. Note that the working machine 100 can be used in the demolition industry, the forest industry, the scrap industry, the waste treatment industry, decontamination work, or the like in an environment with a risk of the presence of radiation due to a radioactive substance or the like leaked from a nuclear power plant or the like. As shown in FIG. 1, the working machine 100 includes a vehicle body 120, an arm body 127, and a radiation detecting attachment 140. The vehicle body 120 includes a crawler-type traveling body 122, a turning mechanism 124, and a turning body 126. The turning body 126 is configured to be rotatable to the traveling body 122 by the turning mechanism 124. A driver's cab 126A is established in the turning body 126. The driver's cab 126A is sealably configured so that radiation can be shielded appropriately while blocking rain and wind. The driver's cab 126A can also be temperature-controlled by an air conditioner. That is, an operator of the working machine 100 can operate the working machine 100 in a stable manner without being greatly influenced by its working environment. Note that the driver's cab 126A has a processing device 170 configured to process outputs from radiation detectors 162 and 164, and a display device 180 configured to display the processing results produced by the processing device 170 (that is, the driver's cab 126A is equipped with the display device 180 capable of displaying an amount of radiation based on the outputs of the radiation detectors 162 and 164). The processing device 170 and the display device 180 will be described later. Note that the working machine 100 may be configured such that the working machine 100 is operated remotely from the outside of the vehicle by air and the operator checks the outputs of the radiation detectors from the outside of the vehicle (alternatively, the working machine 100 may be unmanned by means of programming, AI, or the like). The arm body 127 capable of swinging up and down is attached to the turning body 126. An air compressor (not shown) is installed in the turning body 126. An air inlet of the air compressor is provided with an air filter to be able to filter out a radioactive substance wafting through the air. Compressed air provided by the air compressor is supplied, via the arm body 127, to the radiation detecting attachment 140 supported by the arm body 127. While the supply timing of the compressed air is determined by the operator, such timing may automatically coincide with the start of the detection by the radiation detectors 162 and 164. As shown in FIG. 1, the arm body 127 includes a boom 128 attached to the turning body 126, and an arm 132 attached to a leading end of the boom 128. The arm 132 is configured to be swingable by a cylinder mechanism 130. The radiation detecting attachment 140 is attached removably to a leading end of the arm 132 (that is, the radiation detecting attachment 140 is attached removably to the working machine 100 and supported by the working machine 100 movably (in such a way as to be capable of moving) when the radiation detecting attachment is attached to the working machine). The radiation detecting attachment 140 is configured to be capable of swinging by a cylinder mechanism 134 via a link mechanism 136 (that is, the radiation detecting attachment 140 is supported by the arm body 127 of the working machine 100 swingably (in such a way as to be capable of swinging)). Note that the cylinder mechanisms 130 and 134 are driven by hydraulic pressure provided by the vehicle body 120 (the same applies also to a cylinder mechanism 160 to be described later). Next, the radiation detecting attachment 140 will be described mainly with reference to FIGS. 2A and 2B. The radiation detecting attachment 140 includes: a bracket 146; a frame body 154 supported by the bracket 146 via a plurality of coil springs (elastic members) 148; and four radiation detectors 162 and 164 supported by the frame body 154 for detecting radiation from an object W of detection. That is, the radiation detecting attachment 140 supports the four radiation detectors 162 and 164 via the coil springs 148. Note that the four radiation detectors 162 and 164 may each be provided with a collimator (not shown) for blocking external noise. The bracket 146 is provided with a pivot shaft 142 and a link shaft 144. The pivot shaft 142 engages with the aforementioned arm 132, and the link shaft 144 engages with the aforementioned link mechanism 136. Thus, the bracket 146 is driven to be swingable around the pivot shaft 142. The coil springs 148 are provided at a leading end of the bracket 146, and the frame body 154 is attached to the bracket 146 via the coil springs 148. The frame body 154 includes: a casing 156 fixed to and supported by the coil springs 148; and a moving element 158 supported by the casing 156 movably. The cylinder mechanism 160 is disposed in the casing 156. A cylinder element 160A of the cylinder mechanism 160 is fixed to the casing 156, and a piston element 160B of the cylinder mechanism 160 supports the moving element 158. This makes the moving element 158 movable in an x-direction in FIGS. 2A and 2B. Note that the casing 156 provide with a flow channel 156B communicated with an air pipe 150, and the flow channel 156B is communicated with four discharge nozzles 166. A hydraulic pipe 152 is communicated with the cylinder mechanism 160. The radiation detectors 162 and 164 are, for example, scintillation detectors utilizing a fluorescence action of NaI or the like, and are capable of outputting a detected amount of radiation. Detection surfaces 162A and 164A of the radiation detectors 162 and 164 face the negative side in a z-direction. The radiation detectors 162 are disposed at two corners of the casing 156, and the radiation detectors 164 are disposed at both ends of the moving element 158. Thus, a distance between the radiation detectors 162 and the radiation detectors 164 is changeable (can be modified) by the cylinder mechanism 160. A lower surface 156A of the casing is protruded more than the detection surfaces 162A and 164A by a distance H, thereby providing a level difference between the lower surface 156A of the casing and the detection surfaces 162A and 164A. As a result, even when the lower surface 156A of the casing is brought into contact with the object W of detection in a case where the object W of detection has a planar shape, a gap corresponding to the distance H can be provided between the detection surfaces 162A and 164A of the radiation detectors 162 and 164 and a surface of the object W of detection. That is, the provision of such a level difference can reduce the risk of direct collision with the object W of detection, thereby preventing the failure or breakage of the radiation detectors 162 and 164 due to the external force (the present invention is not limited thereto, and no such a level difference may be provided). In the regions of this level difference, the discharge nozzles 166 for discharging, to the detection surfaces 162A and 164A, the compressed air supplied from the vehicle body 120 are provided. More specifically, the radiation detecting attachment 140 is configured to include the four discharge nozzles 166 disposed to be capable of replacing pre-replacement air Ab between the radiation detectors 162 and 164 and a detection area MA of the object W of detection. And, the four discharge nozzles 166 are configured to discharge post-replacement air Af having a reduced amount of the radioactive substance contained in the pre-replacement air Ab. In the present embodiment, the radiation detectors 162 and 164 are connected to the processing device 170 and the display device 180 via a wireless communication unit (not shown) (this may be implemented via wire communication). The wireless communication unit enables the operator to start and end the detection of the radiation detectors 162 and 164. The operator can also check the outputs of the radiation detectors 162 and 164 in the driver's cab 126A. Since the outputs are provided via wireless communication in the present embodiment, the radiation detectors 162 and 164 can be disposed at positions suitable for the detection without being limited by wire routing. Note that a power supplied from the vehicle body 120 may be used, or a dedicated rechargeable battery may be used as a power source for the radiation detectors 162 and 164 and the wireless communication unit. While the radiation detectors 162 and 164 have exposed detection surfaces 162A and 164A in the present embodiment, the present invention is not limited thereto. The radiation detectors 162 and 164 may each include a shock absorbing member for protecting the detection surface thereof on the detection surface, or the radiation detectors 162 and 164 may be configured to expose the detection surfaces only at the start of the detection. Next, the radiation detectors 162 and 164, the processing device 170, and the display device 180 will be described mainly with reference to FIG. 3. Note that input unit (not shown) is provided in the processing device 170, thereby allowing the operator to instruct the radiation detectors 162 and 164 to start and end the detection. The processing device 170 receives data on the amounts of radiation detected by the radiation detectors 162 and 164 via the wireless communication unit (not shown) and performs various types of arithmetic processing thereon. Specifically, the processing device 170 includes a radiation amount computing unit 172, a mapping processing unit 174, and a sorting determination unit 176. The radiation amount computing unit 172 obtains a total amount of radiation Ct that can be detected by the entire radiation detecting attachment 140 on the basis of a positional relationship of the radiation detectors 162 and 164. For example, it is assumed that an area of each of the detection surfaces 162A and 164A of the radiation detectors 162 and 164 is S0, an area (referred to as a total detection area) surrounded by the radiation detectors 162 and 164 is S1, and amounts of radiation detected by the radiation detectors 162 and 164 are C1, C2, C3, and C4. In this case, the radiation amount computing unit 172 can obtain the total amount of radiation Ct that can be detected by the total detection area S1 according to Expression (1).Ct=(C1+C2+C3+C4)/4/S0*S1  (1) That is, in the radiation detecting attachment 140, the total detection area S1 can be changed (modified) by moving the moving element 158 so that the detection surface is modified to have a size suitable for the object W of detection. Note that the position of the moving element 158 can be obtained by monitoring a supplied oil amount for driving the cylinder mechanism 160 (or an encoder or the like). When the object W of detection is in an individually-separated form (such as a flexible container pack FP to be described later), the radiation amount computing unit 172 can obtain a specific amount of radiation Ci of the object W of detection by inputting a proportion of the total detection area S1 that covers the entire object W of detection (such as a solid angle). The mapping processing unit 174 connects the total amount of radiation Ct to the detection area MA of the object W of detection. For example, a positioning device (navigation system) for pinpointing the current location on a map on the basis of a GPS signal is incorporated into the working machine 100. The mapping processing unit 174 can develop the map data. The mapping processing unit 174 further connects, to the map, data on the shapes of individual structures (such as private houses, apartment houses, public facilities and utilities, and infrastructural facilities and utilities) obtained by a laser scanner or a camera (2D or 3D), or from design data (the data on the shapes of individual structures may be inputted in the form of electronic data via an external interface provided in the processing device 170). The mapping processing unit 174 performs mesh processing on the data on the shapes of the individual structures according to the detection area MA having a size corresponding to the total detection area S1 of the radiation detecting attachment 140. The mapping processing unit 174 then assigns the total amount of radiation Ct to the detection area MA corresponding to the detection position of the radiation detecting attachment 140. The detection position of the radiation detecting attachment 140 in this case can be obtained by monitoring a supplied oil amount for driving each cylinder mechanism (or an encoder or the like). Needless to say, the operator himself or herself may manually determine the detection area MA corresponding to the detection position of the radiation detecting attachment 140. Thus, the mapping processing unit 174 can obtain radiation amount distributions ranging from a radiation amount distribution in a specific individual structure to a radiation amount distribution over a wide range such as a district or a region. The sorting determination unit 176 determines whether the total amount of radiation Ct or the specific amount of radiation Ci exceeds a reference amount Cb of radiation. Based on the determination result, the sorting determination unit 176 changes the display information and gives a guidance for after treatment. When the specific amount of radiation Ci exceeds the reference radiation amount (e.g., 8000 becquerel per 1 Kg) in unit mass, for example, it is determined as radioactive waste by the sorting determination unit 176. Mass data may be estimated in each dividable weight of the object W of detection, or may use outputs of a weight sensor such as a load cell (the weight sensor may be incorporated into a part of a grapple GP or a conveyor BC). Note that the total amount of radiation Ct may be used for sorting determination by converting it in terms of unit area. The display device 180 is connected to the processing device 170 and capable of directly displaying the amounts of radiation detected by the individual radiation detectors 162 and 164 at a display unit 182 thereof. Simultaneously, the display unit 182 can also display the results obtained by the radiation amount computing unit 172, the mapping processing unit 174, and the sorting determination unit 176 (that is, mapping associating the amount of radiation with the detection area MA of the object W of detection can be displayed at the display device 180). These results may be displayed not only in numerical values but also by color coding. Note that the display device 180 may also serve as a display device for the positioning device. Next, a sorting procedure of sorting the object W of detection based on the amount of radiation with the radiation detecting attachment 140 will be described with reference to FIGS. 4 and 5. Note that the object W of detection in this case is a structure BB to be demolished, which is shown in FIG. 4. First, the radiation detecting attachment 140 is attached to the working machine 100 (Step S2 in FIG. 5). The radiation detecting attachment 140 is then brought closer to the detection area MA (Step S4 in FIG. 5). More specifically, the radiation detecting attachment 140 is supported by the working machine 100, and the radiation detecting attachment 140 is brought closer to the detection area MA of the structure BB to be demolished. At this time, the lower surface of the frame body 154 (the lower surface 156A of the casing) in the radiation detecting attachment 140 is brought into contact with the detection area MA. Next, the pre-replacement air Ab is replaced by causing the discharge nozzles 166 to discharge the compressed air (Step S6 in FIG. 5). More specifically, the pre-replacement air Ab (present) between the radiation detectors 162 and 164 and the detection area MA is replaced by the post-replacement air Af having a reduced amount of the radioactive substance contained in the pre-replacement air Ab before obtaining the amount of radiation of the detection area MA. Next, the total amount (amount) of radiation Ct of the detection area MA is obtained (FIG. 4A and Step S8 in FIG. 5). More specifically, the total amount of radiation Ct of the detection area MA corresponding to the total detection area S1 is obtained by the radiation amount computing unit 172 on the basis of the outputs of the radiation detectors 162 and 164. Thereafter, the total amount of radiation Ct is connected to the detection area MA by the mapping processing unit 174. Next, mapping associating the obtained total amount of radiation Ct with the detection area MA is displayed at the display device 180 (Step S10 in FIG. 5). Next, it is determined whether all detection areas MA have been subjected to the detection. If the detection on the all detection areas MA has not been finished yet (No in Step S12 in FIG. 5), the detection is started on another detection area MA (Steps S4 to S10 in FIG. 5). If the all detection areas MA have been subjected to the detection (Yes in Step S12 in FIG. 5), the radiation detecting attachment 140 is replaced by high-powered cross cutter (coarse crushing equipment: working attachment) CT (Step S14 in FIG. 5). More specifically, the radiation detecting attachment 140 is detached from the working machine 100, and the high-powered cross cutter CT, capable of dividing the structure BB to be demolished into each of the detection areas MA, is attached to the working machine 100 (this transforms the working machine 100 into a working machine 101). Next, the structure BB to be demolished is divided with the high-powered cross cutter CT (FIG. 4B and Step S16 in FIG. 5). More specifically, the structure BB to be demolished is divided with the high-powered cross cutter CT in accordance with the obtained total amounts of radiation Ct. Once divided, the segments of the structure BB to be demolished, having been divided in accordance with the level of the total amounts of radiation Ct, are placed at different locations in order to prevent a level of the total amount of radiation Ct mixing with one another. Also with regard to the dividing procedure, segments of the structure BB to be demolished, having equivalent total amounts of radiation Ct, are divided together as much as possible in accordance with the total amounts of radiation Ct. Note that a mechanism for discharging water jet capable of dividing the structure BB to be demolished into each of the detection areas MA may be attached to the working machine in place of the high-powered cross cutter CT. As just described, by using the radiation detecting attachment 140 in the demolition of the structure BB to be demolished, the distribution of the amounts of radiation for all of the structure BB to be demolished can be found out before the demolition work. This allows for efficient demolition work and quick sorting. The radiation detecting attachment 140 is detached from the working machine 100, high-powered cross cutter CT is attached to the working machine 100, and the structure BB to be demolished is divided with the high-powered cross cutter CT in accordance with the obtained total amounts of radiation Ct. Therefore, the vehicle body 120 itself of the working machine 100 is shared with the working machine 101. Thus, the structure BB to be demolished can be easily sorted even in a narrow working site. Next, a sorting procedure of sorting another object W of detection on the basis of an amount of radiation with the radiation detecting attachment 140 will be described with reference to FIGS. 6 and 7. Note that the object W of detection in this case is a flexible container pack FP shown in FIG. 6C. The flexible container pack FP contains, for example, contaminated soil, contaminated plants, or the like resulting from decontamination work, or contaminated waste produced by demolition work or the like. First, a conveyor (conveying unit) BC capable of conveying a plurality of flexible container packs FP is prepared (FIG. 6A and Step S20 in FIG. 7). At this time, a proportional rate of the radiation detecting attachment 140 that covers the flexible container pack FP is inputted to the processing device 170, for example. While the conveyor BC moves the flexible container pack FP simply in one direction without changing its physical orientation in the present embodiment, the present invention is not limited thereto. The conveyor BC may be configured to move the flexible container pack FP in one direction while rotating the flexible container pack FP and to cause the flexible container pack FP to be constantly in contact with one end of the conveyor BC (the side on which the radiation detecting attachment 140 is disposed). Next, the radiation detecting attachment 140 is detached from the working machine 100 (Step S22 in FIG. 7). Thereafter, the grapple GP capable of supporting the flexible container pack FP is attached to the working machine 100 (Step S24 in FIG. 7). This transforms the working machine 100 into a working machine 102. Note that the grapple GP is provided with a weight sensor and thus includes a configuration for measuring a weight of the supported flexible container pack FP and sending the measured result to the processing device 170 (the working attachment may be a hook, or the like, capable of hanging the flexible container pack FP instead of the grapple GP). At the same time, the radiation detecting attachment 140 is disposed near the conveyor BC so that radiation of the plurality of flexible container packs FP moving on the conveyor BC can be detected sequentially (FIG. 6B and Step S26 in FIG. 7). Thereafter, the place at which the radiation detecting attachment 140 is disposed is covered with a box-shaped cover CV (The box-shaped cover CV is provided with, for example, openable and closable doors through which the flexible container pack FP can pass. More specifically, once a single flexible container pack FP moves and enters into the box-shaped cover CV, the openable and closable doors are closed. After its amount of radiation is detected, the openable and closable doors are opened so that the flexible container pack FP moves and exits from the box-shaped cover CV. Needless to say, no box-shaped cover CV may be provided.) Note that the radiation detecting attachment 140 is controlled from the working machine 102. In the present embodiment, in disposing the radiation detecting attachment 140 near the conveyor BC with the working machine 100, the radiation detecting attachment 140 is detached and installed at the same place. The present invention, however, is not limited thereto. The radiation detecting attachment 140 detached at another place may be disposed and installed near the conveyor BC with the grapple GP of the working machine 102 or by hand. While only one radiation detecting attachment 140 is disposed on one side of the conveyor BC in the present embodiment, the present invention is not limited thereto. With the use of a plurality of radiation detecting attachments, the radiation detecting attachments may be disposed on the both sides of the conveyor belt BC or above the conveyor belt BC. Next, the conveyor BC is driven, and the plurality of flexible container packs FP are disposed on the conveyor BC with the grapple GP in order to detect radiation (Step S28 in FIG. 7). Note that the conveyor BC can be driven, for example, by remotely controlling its start, end, and conveying speed as appropriate. Next, to detect an amount of radiation for each of the flexible container packs FP, the openable and closable doors are closed when the flexible container pack FP enters into the box-shaped cover CV, and at least the pre-replacement air Ab between the radiation detectors 162 and 164 and the flexible container pack FP is replaced by the post-replacement air Af having a reduced amount of the radioactive substance contained in the pre-replacement air Ab (Step S30 in FIG. 7). It is more preferable that the pre-replacement air Ab be replaced for all the air inside of the box-shaped cover CV. Next, radiation is detected for each of the plurality of flexible container packs FP with the radiation detecting attachment 140. Data on the amounts of radiation is then transmitted to the processing device 170 from the radiation detecting attachment 140. The transmitted radiation amount data is processed by the radiation amount computing unit 172 of the processing device 170 to obtain a specific amount of radiation (amount) Ci for each of the flexible container packs FP (Step S32 in FIG. 7). Thereafter, the display device 180 displays the obtained specific amount of radiation Ci and its process procedure, for example, for each of the flexible container packs FP on the basis of outputs of the sorting determination unit 176 (Step S34 in FIG. 7). Next, the flexible container pack FP having exited from the box-shaped cover CV is sorted with the grapple GP on the basis of the obtained specific amount of radiation Ci (FIG. 6C and Step S36 in FIG. 7). For example, the working machine 102 can dispose the flexible container packs FP while varying placement locations between PL1 and PL2 depending on a level of the specific amount of radiation Ci as shown in FIG. 6C. As just described, in evaluating amounts of radiation of the flexible container packs FP, the use of the conveyor BC and the detached radiation detecting attachment 140 enables the flexible container packs FP to be handled in a conveyer system, without the flexible container packs FP being individually moved and processed with the working machine one by one. In other words, efficient detection and sorting can be achieved in the handling of a large number of flexible container packs FP. The radiation detecting attachment 140 is detached from the working machine 100, the grapple GP capable of supporting the flexible container pack FP is attached to the working machine 100 (this transforms the working machine 100 into the working machine 102), and the plurality of flexible container packs FP are disposed on the conveyor BC with the grapple GP in order to detect radiation. Therefore, the vehicle body 120 itself of the working machine 102 that disposes the flexible container packs FP on the conveyor BC is shared with the working machine 100 that detects and processes amounts of radiation. Thus, the flexible container packs FP can be disposed on the conveyor BC even in a narrow working site. Note that the present invention is not limited thereto. In order to achieve quick sorting for a large number of flexible container packs FP, a plurality of flexible container packs FP may be disposed on the conveyor BC with another working machine. Furthermore, the obtained specific amount of radiation Ci is displayed for each of the flexible container packs FP. This allows the flexible container pack FP to be sorted easily in accordance with the specific amount of radiation Ci. The object W of detection is sorted with the grapple GP in accordance with the obtained specific amount of radiation Ci. Therefore, the vehicle body 120 itself of the working machine 102 that disposes the flexible container packs FP on the conveyor BC and sorts the flexible container packs FP on the conveyor BC is shared with the working machine 102 that detects and processes amounts of radiation. Thus, the flexible container packs FP can be easily moved from the conveyor BC and sorted even in a narrow working site. Note that the present invention is not limited thereto. In order to achieve quick sorting for a large number of flexible container packs FP, a plurality of flexible container packs FP on the conveyor BC may be sorted with another working machine. In the present embodiment, the radiation detecting attachment 140 including the four radiation detectors 162 and 164 is attached removably to the working machine 100. Furthermore, the radiation detecting attachment 140 is supported by the working machine 100 movably. This imposes less limitation on the size of the object W of detection and enables a distance to the object W of detection and a positional relationship with the object W of detection to be adjusted appropriately. Moreover, since the need for personnel to detect radiation can be eliminated, cost reduction in work in an environment with a risk of the presence of radiation due to a radioactive substance or the like leaked from a nuclear power plant or the like can be promoted. In the present embodiment, the radiation detecting attachment 140 is supported by the arm body 127 of the working machine 100 swingably. This can further broaden the positional flexibility of the radiation detecting attachment 140. In the present embodiment, a distance between the two radiation detectors 164 and the other two radiation detectors 162 is changeable. Thus, radiation can be detected efficiently by changing a clearance between the radiation detectors 162 and 164 in accordance with the size of the object W of detection. Note that the present invention is not limited thereto. Even when the radiation detecting attachment includes a plurality of radiation detectors, all of the radiation detectors may be fixed in place. Alternatively, when the radiation detecting attachment includes three or more radiation detectors, the radiation detectors may be movable not only in a single axial direction but also in a plurality of axial directions. In the present embodiment, the four radiation detectors 162 and 164 are supported via the coil springs 148. This can reduce the possibility of failure, breakage, or the like, of the radiation detectors 162 and 164 even if a large external force is applied to the radiation detectors 162 and 164. Note that no coil springs may be provided. Alternatively, coil springs may be provided in the frame body so as to correspond to the radiation detectors, and the coil springs may be configured to support the radiation detectors individually. In this case, since the stiffness of the coil springs can be set lower, the breakage or failure of the radiation detectors due to collision or the like can be further prevented from occurring. Needless to say, a flat spring, a rubber material, other damper means, or the like may be used instead of the coil spring. In the present embodiment, there are provided the four discharge nozzles 166 disposed to be capable of replacing the pre-replacement air Ab between the radiation detectors 162 and 164 and the detection area MA of the object W of detection, and the post-replacement air Af having a reduced amount of the radioactive substance contained in the pre-replacement air Ab is discharged from the four discharge nozzles 166. Thus, even in an environment with a high air dose, for example, the low-amount of radiation from the object W of detection can be detected. That is, the amount from radiation of the object W itself of detection can be accurately detected by reducing the influence of the air dose. Note that the present invention is not limited thereto. No such discharge nozzles may be provided. Alternatively, not a single but two discharge nozzles may be provided for each of the radiation detectors. Alternatively, a single discharge nozzle may be disposed to be used for all of the radiation detectors. Alternatively, the discharge nozzle may be configured to be integral with not the frame body but the radiation detector. In the present embodiment, the driver's cab 126A is equipped with the display device 180 capable of displaying amounts of radiation based on outputs of the radiation detectors 162 and 164. Thus, an operator in the driver's cab 126A can directly check the amounts of radiation without successively moving to the position of the radiation detecting attachment 140 to check the outputs of the radiation detectors 162 and 164. Note that the present invention is not limited thereto. The display device may be provided not in the driver's cab but in an external device that gives instructions to the working machine. The amounts of radiation may be provided not in the form of display but in the form of voice. The radiation may be indicated by direct numerical values or only by colors at the display device. In the present embodiment, mapping associating the total amounts of radiation Ct with the detection areas MA of the object W of detection, such as the structure BB to be demolished, can be displayed at the display device 180. Thus, a level of such an amount of radiation can be determined for each of the detection areas MA. Therefore, in demolishing the object W of detection, a required space to dispose waste resulting from the demolition, its demolition procedure, or the like can be predicted before starting the demolition. That is, there is no need to separately check the demolition procedure or the amounts of radiation after the demolition, thereby enabling an improvement in working efficiency. Note that the present invention is not limited thereto. No mapping display for the total amounts of radiation Ct may be provided. That is, the use of the radiation detecting attachment 140 in the present embodiment makes it possible to use the radiation detectors 162 and 164 efficiently and in a versatile manner. While the present invention has been described with reference to the first embodiment, the present invention is not limited to the first embodiment. That is, it is needless to say that modifications and design changes are possible without departing from the scope of the present invention. For example, while the radiation detecting attachment 140 includes the four radiation detectors 162 and 164 and a clearance between the radiation detector 162 and the radiation detector 164 is changeable in the x-direction on the x-y plane in the above-described embodiment, the present invention is not limited thereto. For example, the radiation detecting attachment may be configured as in a second embodiment and a third embodiment shown in FIGS. 8A and 8B, respectively. In the second and third embodiments, radiation detecting attachments each include a plurality of claw members capable of coming closer to each other and separating from each other. Specifically, in the second embodiment shown in FIG. 8A, claw members 256 and 258 provided in a rotating mechanism 248 are grasping members for grasping a specified object, and a radiation detecting attachment 240 constitutes a grapple GP. In the third embodiment shown in FIG. 8B, claw members 356 and 358 are cutting members capable of cutting a specified object, and a radiation detecting attachment 340 constitutes a cutter (the radiation detecting attachment 340 may be high-powered cross cutter CT, normal cross cutter, a crusher, or the like). In such cases, a single radiation detector may be disposed at only any one of a plurality of positions 262A, 262B, 262C, 263, 264A, 264B, and 264C (362, 363, and 364) indicated by broken lines, or radiation detectors may be provided at all of those positions. When a plurality of radiation detectors are disposed in the different claw members 256 and 258 (356 and 358), a clearance between the radiation detectors may be modified by opening and closing the claw members 256 and 258 (356 and 358). With the use of the claw members 256 and 258 (356 and 358) shown in FIGS. 8A and 8B, the radiation detecting attachment 240 (340) can function also as a conventional working attachment such as the cutter or the grapple GP. By grasping the object W of detection with the claw members 256 and 258 (356 and 358), for example, a distance to the object W of detection can be stabilized, and the object W of detection can be accurately identified for the detected amount of radiation. Note that the present invention is not limited thereto. The opening and closing form of claw members may be configured in such a manner that the claw members come closer to one another from a plurality of axial directions as in what is called a tulip shape. Alternatively, the radiation detecting attachment may include a mechanism for discharging water jet capable of cutting a specified object. While the radiation detecting attachment 140 is supported by the arm body 127 of the working machine 100 swingably in the above-described embodiment, the present invention is not limited thereto. For example, the radiation detecting attachment may be configured as in a fourth embodiment shown in FIG. 9. In the fourth embodiment, a radiation detecting attachment 440 is supported by a linear-motion mechanism 425 so as to be capable of being translated with respect to a turning body 426, rather than being supported by an arm body 427 swingably. Also, in the fourth embodiment, a working machine 400 is configured to simultaneously include the radiation detecting attachment 440 and a grapple GP capable of supporting an object W of detection and the radiation detecting attachment 440. This enables objects W of detection to be disposed on a conveyor BC with the equipped grapple GP in order to detect radiation. That is, no other working machine is required, and replacement work between the radiation detecting attachment 440 and the grapple GP can be eliminated. Thus, the objects W of detection can be easily moved from the conveyor BC and sorted even in a narrow working site. Assume that the working machine 400 includes high-powered cross cutter CT (it may be a cutter) instead of the grapple GP in FIG. 9. In this case, the object W of detection can be divided with the high-powered cross cutter CT in accordance with the obtained amounts of radiation. That is, no other working machine is required, and replacement work between the radiation detecting attachment 440 and the CT can be eliminated. Thus, the objects W of detection can be quickly sorted even in a narrow working site. Note that the working machine may include a plurality of arm bodies, and the grapple GP (or the high-powered cross cutter CT or the cutter) and the radiation detecting attachment may be supported by the different arm bodies. While the radiation detectors are scintillation detectors in the above-described embodiment, the present invention is not limited thereto. For example, a fluoroglass dosimeter or a thermoluminescence dosimeter utilizing a fluorescence action, a photographic film, a semiconductor dosimeter, a chemical dosimeter, discharge ionization chamber dosimeter, a GM counter, or the like may be employed as a radiation detector. The present invention can be widely applied to the demolition industry, the forest industry, the scrap industry, the waste treatment industry, decontamination work, or the like, having a risk of radiation contamination. 100, 101, 102, 400 . . . working machine 120, 420 . . . vehicle body 122, 422 . . . traveling body 124, 424 . . . turning mechanism 126, 426 . . . turning body 126A . . . driver's cab 127, 427 . . . arm body 128 . . . boom 130, 134, 160 . . . cylinder mechanism 132 . . . arm 136 . . . link mechanism 140, 240, 340, 440 . . . radiation detecting attachment 142 . . . pivot shaft 144 . . . link shaft 146, 246, 346 . . . bracket 148 . . . coil spring 150 . . . air pipe 152 . . . hydraulic pipe 154, 254, 354 . . . frame body 156 . . . casing 156A . . . lower surface of casing 156B . . . flow channel 158 . . . moving element 160A . . . cylinder element 160B . . . piston element 162, 164 . . . radiation detector 162A, 164A . . . detection surface 166 . . . discharge nozzle 170 . . . processing device 172 . . . radiation amount computing unit 174 . . . mapping processing unit 176 . . . sorting determination unit 180 . . . display device 182 . . . display unit 248 . . . rotating mechanism 256, 258, 356, 358 . . . claw member 262A, 262B, 262C, 263, 264A, 264B, 264C, 362, 363, 364 . . . position (where a radiation detector may be disposed) 425 . . . linear-motion mechanism Ab . . . pre-replacement air Af . . . post-replacement air BB . . . structure to be demolished BC . . . conveyor CT . . . high-powered cross cutter CV . . . box-shaped cover FP . . . flexible container pack GP . . . grapple MA . . . detection area PL1, PL2 . . . placement location W . . . object of detection

summary

summary

abstract

A charged-particle beam writing apparatus used for writing a predetermined pattern on a sample placed on a stage with a charged-particle beam. The apparatus comprises a height measuring unit that measures a height of the sample by irradiating the sample with light and receiving light reflected from the sample, and a control unit that receives either of height data acquired from a height data map prepared based on values measured by the height measuring unit before writing and height data measured by the height measuring unit during writing, thereby adjust an irradiation position of the charged-particle beam on the sample.

description

FIG. 1 is a schematic, partial cross-sectional, illustration of a known prestressed concrete reactor vessel (PCRV) 10 for a natural circulation reactor (NCR). PCRV 10 has a concrete shell 12 which is closed at its top end 14 by a removable top head 16. Concrete shell 12 includes a substantially cylindrical inside surface 18 defining a PCRV chamber 20. A reactor core 22 and other reactor components 24 are located in PCRV chamber 20. In the past, an insulated steel liner 26 and a reactor wall cooling system (not shown in FIG. 1) are utilized in connection with PCRV 10. Particularly, inside surface 18 of PCRV 10 is lined with steel liner 26 to facilitate keeping PCRV 10 leak-tight, and an inside surface 28 of steel liner 26 is lined with a layer of insulation 30 to substantially insulate steel liner 26 from heat generated by core 22 during reactor operation. The reactor wall cooling system for cooling concrete shell 12 is configured to transport cooling fluid, e.g., water, throughout PCRV shell 12 and includes several cooling pipes embedded in concrete shell 12. The pipes extend through shell 12 adjacent steel liner 26 and are coupled to motors, pumps, valves and heat exchangers which cooperate to transport the cooling fluid through shell 12 and disperse heat within concrete shell 12. As explained above, installing the reactor wall cooling system in reactor concrete shell 12 is time consuming and tedious. In addition, and because the cooling system pipes are embedded in the concrete, inspecting and repairing the cooling system pipes is difficult. Moreover, inspecting and repairing steel liner 26 is difficult because of insulation layer 30. FIG. 2 is a schematic, partial cross-section, illustration of a prestressed concrete reactor vessel (PCRV) 40 for a natural circulation reactor in accordance with one embodiment of the present invention. PCRV 40 includes a concrete shell 42 having an outer surface 44 and an inner surface 46. A bottom head 48 and a substantially cylindrical side wall 50 define a PCRV chamber 52. A removable top head 54 is coupled to a top end 56 of concrete shell 42 and is configured to close, or seal, vessel chamber 52. An uninsulated steel liner 58 is positioned within vessel chamber 52 and is spaced from PCRV inner surface 46 to define an insulating chamber 60 between steel liner 58 and PCRV inner surface 46. Particularly, steel liner 58 includes a bottom wall 62 and a substantially cylindrical side wall 64 extending therefrom to define a core receiving chamber 66 sized to receive reactor components such as steam separators and the core. Steel liner 58 is positioned coaxially within PCRV chamber 52 so that steel liner bottom wall 62 is spaced from bottom head 48 and steel liner side wall 64 is spaced from PCRV inner surface side wall 50. A layer of insulating material 68 is positioned between steel liner 58 and PCRV inner surface 46 to substantially insulate concrete shell 42 from heat generated within the reactor core. Particularly, insulating chamber 60 is substantially filled with insulating material 68 so that insulating material 68 extends between PCRV side wall 50 and steel liner side wall 64, and between PCRV bottom head 48 and steel liner bottom wall 62. Insulating material 68 transfers loads from steel liner 58 to concrete shell 42. Particularly, insulating material 68 transfers internal loads, e.g., pressure, from steel liner 58 to concrete shell 42. In addition, insulating material 68 substantially insulates concrete shell 42 from heat generated by the reactor core. Insulating material 68 may, for example, be a High Aluminate Cement Concrete (HACC). Alternatively, insulating pressure material 68 may be fabricated from fire bricks or fire brick variations, or heat resistant concrete, or refractory castable concrete. The concrete shell of the above described reactor is substantially insulated from heat generated by the reactor core without the inner surface of the steel liner being insulated. Such shell also is maintained at a cool temperature without requiring a reactor wall cooling system. In addition, the uninsulated steel liner of the above described reactor is believed to be easier to inspect than steel liners in known large circulation nuclear reactors. From the preceding description of various embodiments of the present invention, it is evident that the objects of the invention are attained. Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is intended by way of illustration and example only and is not to be taken by way of limitation. Accordingly, the spirit and scope of the invention are to be limited only by the terms of the appended claims.

description

The following subject matter relates to improvements in the process for vitrifying waste materials, and more particularly, to improvements especially for the vitrification of radioactive waste materials by changing the chemical composition and physical characteristics of additives that are added to the waste material or included in the glass frit to obtain a suitable vitrified product, such that the reactions between the additives and the waste materials suppress the formation of undesirable molybdate secondary phases. Large quantities of radioactive nuclear waste materials that are produced as byproducts from activities such as weapons programs, nuclear fuel recycling, and medical isotope production, are stored in various countries around the world. Vitrification of these waste materials to produce a durable glass product is the preferred approach for treating and disposing of these waste materials because of the high durability of the glass waste form as compared to other waste forms such as grout. Vitrification of radioactive high level waste (HLW) to produce a borosilicate glass product is the internationally accepted waste treatment method. Vitrification of the waste materials is done in melters such as Joule Heated Ceramic Melters (JHCM), Hot Wall Induction Melters (HWIM), Cold Crucible Induction Melters (CCIM), and the like. In waste vitrification, the waste materials are mixed with appropriate amounts of raw materials, know as “additives”, and melted at a high temperature (typically 1150° C. for JHCMs, typically somewhat lower for HWIMs, and typically somewhat higher for CCIMs) in order to produce glass products that meet pre-specified product quality requirements. The product quality requirements mostly relate to the chemical durability of the glass product as measured by standard test procedures. Many waste materials are stored in tanks in slurry or solution form. The additives are typically used either in the form of pre-melted chemicals (glass frit) with a specified composition, or raw materials in the form of minerals or chemicals. The additive minerals or chemicals are commonly referred to as glass forming chemicals (GFCs). In either case, the waste materials with the additives are designed to melt and form a glass product with a predetermined oxide composition. The waste materials mixed with the appropriate amounts of frit or GFCs are referred to as melter feeds. These materials may be mixed either outside or inside the melter. In many situations, the melter feed is introduced from the top of the melter to the melt pool surface so that a layer of feed material covers the hot glass melt underneath. This layer is commonly referred to as the cold-cap. The cold-cap extends from partially melted melter feed in contact with the melt pool to unreacted melter feed at the top. In other situations such as batch-style induction melters, the melt zone progresses from the hot wall on the outside into the bulk. Consequently, in this case also there is a boundary zone between predominantly melted material and predominantly unmelted feed material. This zone is also referred to as a cold cap. Reactions in the cold-cap, and controlling these reactions, are a key approach to mitigating undesirable molybdate secondary phase formation. Due to the complexity of the waste materials, and the number of different constituents, persistent secondary phases are often formed during the melting process. The extent of formation of these secondary phases depends on various factors such as concentrations of troublesome constituents, the types of additives, waste processing rates, processing temperatures, etc. One of the common waste constituents that show a tendency to form secondary phases during nuclear waste vitrification is molybdenum. Formation of molybdate secondary phases is undesirable because they lead to both processing and product quality issues. Molybdate phases are easily leachable, leading to unacceptable product quality. In addition, these secondary phases tend to selectively incorporate high concentrations of other components such as cesium leading to additional product quality issues. Alkali molybdate phases can accumulate on the melt surface causing excessive corrosion of melter components that are in contact with this phase. Alkaline earth molybdates tend to sink to the bottom of the melter and accumulate. The accumulation of molybdate secondary phases at the melter bottom can cause problems with glass discharge, especially for melters that use a bottom discharge. The molybdate phase formation is a result of the high molybdenum concentration in the HLW feed to the vitrification facility. The molybdate secondary phase formation initially occurs near the interface between the molten glass pool and the cold-cap. Studies performed at the Vitreous State Laboratory of the Catholic University of America showed that kinetically controlled cold-cap conversion processes are responsible for the generation of molten molybdate salt, rather than solubility limits of molybdates in the underlying glass melt. When the melter feed is prepared by mixing glass frit or glass forming chemicals with the HLW material in slurry form, or when the HLW and glass frit or glass forming chemicals are fed separately, the molybdate secondary phase tends to form before the underlying glass melt reaches saturation with respect to molybdate. If the feed chemistry can be altered to suppress the molybdate secondary phase formation until its concentration reaches closer to the solubility limit, the amount of waste incorporated into unit amount of glass produced (waste loading) can be increased leading to substantial cost savings in HLW treatment and disposal. Sulfur is another component in waste streams that at high concentrations causes the formation of secondary sulfate layers during the melting process. In this case also, the secondary sulfate layer is formed well before the underlying glass melt reaches sulfate solubility limit. Again, improvements to the feed chemistry by judicious choice of additives to delay the formation of sulfate secondary phase until the sulfate concentration reaches closer to the solubility limit, has enormous economical advantage. The same principles should be effective for mitigating other troublesome salt-forming species such as chlorine, fluorine, chromium (chromate), and phosphorous. Furthermore, the chemical similarities between sulfate and molybdate lead to interactions that tend to promote the formation of secondary phases when both of these components are present. A number of methods are disclosed for the vitrification of waste materials such as radioactive wastes and particularly high level radioactive wastes. The methods improve the efficiency of the vitrification process. The methods may include modifying the glass composition and additives to reduce the tendency to form molybdate secondary phases during vitrification, thereby increasing the amount of waste incorporated into each unit amount of glass produced. In one embodiment, the method for vitrifying waste to reduce the formation of persistent molybdate secondary phases includes the steps of providing a waste for vitrification; providing a glass frit additive or glass forming chemicals or both for mixing with the waste; providing a source of vanadium; and, feeding the waste, the glass frit or glass forming chemicals or both, and any additives to a melter for vitrification of the waste so that formation of molybdate secondary phases is suppressed. In a further advantageous embodiment, the method includes selecting the glass frit from the group consisting of glass beads, cylindrical glass fiber cartridges, glass powder, and glass flakes. In a further advantageous embodiment, the method includes modifying the product glass composition to include vanadium oxide. In a further advantageous embodiment, the method includes modifying the product glass composition to include no more than 10 wt % vanadium oxide; or no more than 5 wt % vanadium oxide; or no more than 2 wt % vanadium oxide; or no more than 1 wt % vanadium oxide. The glass product may also include at least 0.5 wt % vanadium oxide. In a further advantageous embodiment, the vanadium oxide is introduced as an additive that is combined with the waste. In a further advantageous embodiment, the vanadium oxide is introduced by modifying the glass frit composition such that the vanadium oxide is part of the composition of the glass frit. In a further advantageous embodiment, the source of the vanadium oxide is any convenient vanadium compound that will react and decompose under the high temperature glass melting conditions to produce vanadium oxide that is then incorporated into the glass structure. In a further advantageous embodiment, the waste and glass frit or glass forming chemicals are fed separately to the melter. In a further advantageous embodiment, the waste and glass frit or glass forming chemicals are combined to produce a melter feed that is then fed to the melter. In one study, oxide compositions were formed by combining 15.81% of IHI High Level Waste (HLW) simulant and 84.19% of IHI glass frit. The HLW simulant contained about 8.64 wt % of MoO3 for conducting the process discussed herein. The glass composition used in the studies had a waste loading of 15.81 wt %. The resulting glass had MoO3 concentration of 1.37 wt %. Additives for mixing with the waste material were provided in the form of pre-melted glass frit beads. The 15.81% of IHI HLW simulant is provided in slurry form. Appropriate amounts of IHI glass frit beads, totaling approximately 84.19%, were added so that the resulting glass melt formed the desired oxide composition having the characteristics noted above. Heat treatment of the mixture in the range of 700 to 900° C. in gradient or isothermal furnaces resulted in the formation of the undesirable molybdate phases. Both alkali and alkaline earth molydates were identified. Even though the nominal operating temperature of a typical glass melter is 1150° C., formation of molydate phases at any temperature in the range of 100 to 1150° C. is of concern because the temperature in the cold-cap region ranges from about 100° C. at the top surface to about 1150° C. at the glass melt interface. To confirm this observation, a continuously-fed joule-heated ceramic melter test was conducted during which about 20 kg of glass was produced over a period of about 64 hours. Samples collected from the melt surface and from the melter floor showed the presence of molybdate yellow phase both on the melt surface and on the melter floor. The surface samples were higher in alkali molybdates whereas the floor samples were higher in alkaline earth molybdates. Next, a set of tests was designed to identify changes to the above formulation by modifying the glass composition to include vanadium oxide while maintaining all of the glass and melt properties within acceptable ranges for processing and product quality. Crucible-scale tests were conducted to identify the most promising glass composition modifications to eliminate molybdate phase formation. The waste simulant composition used for these tests was higher in molybdenum, contained sulfate, and was employed at a higher waste loading than was the case for the previous test that showed extensive molybdate secondary phase formation. All of these differences would be expected to significantly increase the tendency for molybdate secondary phase formation. The HLW simulant contained about 7.21 wt % of MoO3 and 1.25 wt % SO3. The glass composition used in the studies had a waste loading of 30.39 wt %. The resulting glass had a MoO3 concentration of 2.19 wt % and a SO3 concentration of 0.38 wt %. It was found that addition of 2.6 wt % V2O5 in combination with 7.7 wt % Al2O3 and 2.4 wt % B2O3 to the high level waste and modification of the frit composition suppressed molybdate phase formation. In a separate test using the same waste simulant, waste loading, and test conditions as those described above, instead of adding the V2O5 as a separate ingredient the V2O5 was first incorporated into the glass frit during the prior melting process used to produce the glass frit. Once again, the addition of vanadium effectively suppressed yellow phase formation. To confirm this observation, a continuously-fed joule-heated ceramic melter test was conducted during which about 25 kg of glass was produced over a period of about 100 hours. The test used the same waste simulant, additives, and waste loading as those described above. Samples collected from the melt surface and from the melter floor showed no sign of molybdate yellow phase. A further 100 hours of testing was performed and similar samples again showed no signs of molybdate yellow phase. A further 100 hours of testing was performed in which the waste loading was increased to 32 wt %. Again, similar sampling at the end of the test showed no signs of molybdate yellow phase; for this test, the target glass composition had a MoO3 concentration of 2.31 wt % and a SO3 concentration of 0.40 wt %. A further 100 hours of testing was performed in which the waste loading was increased to 34 wt %. Once again, similar sampling at the end of the test showed no signs of molybdate yellow phase; for this test, the target glass composition had a MoO3 concentration of 2.45 wt % and a SO3 concentration of 0.43 wt %. The above tests conclusively demonstrated that modification of the glass composition to include vanadium oxide is an effective method to suppress the formation and accumulation of separate molybdate phases during HLW simulant feed processing during vitrification. Different variations of the method that will also improve the suppression of secondary phase formation include: 1) incorporation of a higher or lower amount of vanadium oxide; 2) complete replacement of glass fit with raw chemicals that are added directly to the HLW slurry; 3) incorporation of the vanadium oxide into the glass frit; 4) addition of a vanadium salt that reacts and decomposes to form vanadium oxide under the high temperature glass melting conditions; 5) modification of the glass composition in any of the ways described above to suppress secondary phase formation so that waste loading in the glass can be increased; 7) modification of the glass composition in any of the ways described above where the frit is in the form of glass beads (nominally 2 to 3 mm in diameter); 8) modification of the glass composition in any of the ways described above where the frit is in the form cylindrical glass fiber cartridges (nominally 70 mm diameter and 70 mm length); 9) modification of the glass composition in any of the ways described above where the frit is in the form of a powder (nominally less than 80 mesh); 10) modification of the glass composition in any of the ways described above where the frit is in the form of glass flakes. The above innovations can be implemented in any and all of the following glass making processes: 1) JHCM in which the glass frit or glass forming chemicals and HLW slurry with the vanadium oxide sources are fed separately to the melter; 2) JHCM in which the glass frit or glass forming chemicals and HLW slurry with the vanadium oxide sources are mixed and fed together to the melter; 3) JHCM in which the glass frit or glass forming chemicals, vanadium oxide sources and calcined HLW are fed to the melter as solid powders; 4) Cold Crucible Induction Melters (CCIM) in which the glass frit or glass forming chemicals and HLW slurry with the vanadium oxide sources are fed separately to the melter; 5) CCIM in which the glass frit or glass forming chemicals and HLW slurry with the vanadium oxide sources are mixed and fed together to the melter; 6) CCIM in which the glass frit or glass forming chemicals, vanadium oxide sources, and calcined HLW are fed to the melter as solid powders; 7) Hot Wall Induction Melters (HWIM) in which the glass frit or glass forming chemicals and HLW slurry with the vanadium oxide sources are fed separately to the melter; 8) HWIM in which the glass frit or glass forming chemicals and HLW slurry with the vanadium oxide sources are mixed and fed together to the melter; 9) HWIM in which the glass frit or glass forming chemicals, vanadium oxide sources, and calcined HLW are fed to the melter as solid powders. The method has application in the suppression of secondary phases formed by molybdenum and sulfur and the same principles should be effective for mitigating other troublesome salt-forming species such as chlorine, fluorine, chromium (chromate), and phosphorous. Reference is made in the following to a number of illustrative embodiments of the disclosed subject matter. The following embodiments illustrate only a few selected embodiments that may include one or more of the various features, characteristics, and advantages of the disclosed subject matter. Accordingly, the following embodiments should not be considered as being comprehensive of all of the possible embodiments. In one embodiment, a method for vitrifying waste to reduce the formation of molybdate secondary phases comprises: providing a waste for vitrification; providing a glass fit additive, a mix of glass forming chemicals, or both for melting with the waste; providing a source of vanadium, either as an additive to the waste or as part of the glass frit composition; and feeding the waste, the glass frit or the glass forming chemicals or both, and the additive to a melter for vitrification of the waste so that formation of molybdate secondary phases is suppressed. The source of the vanadium is any convenient vanadium compound that will react and decompose under the high temperature glass melting conditions to produce vanadium oxide that is then incorporated into the glass structure. The vanadium source can be introduced as an additive that is combined with the waste or as a separate ingredient. In one embodiment, the vanadium source is introduced by modifying the glass frit composition such that the vanadium is part of the composition of the glass frit. The product glass composition can include up to 10 wt % vanadium oxide; or up to 5 wt % vanadium oxide; or up to 2 wt % vanadium oxide; or up to 1 wt % vanadium oxide. The waste and glass frit and glass forming chemicals and vanadium source can each be fed separately to the melter or one or more or all of these can be combined together before they are fed to the melter. In one embodiment, one or more of the components (e.g., glass frit, glass forming chemicals and vanadium source) are combined with the waste before they are fed to the melter and the remaining components are fed separately to the melter. The glass frit can be selected from the group consisting of glass beads, cylindrical glass fiber cartridges, glass powder, and glass flakes. The method can reduce the formation of molybdate yellow phases and/or the formation of sulfate salt phases. The method can also reduce the formation of salt phases that incorporate molybdate, sulfate, and pertechnetate. The method can reduce the formation of salt with one or more of chlorine, fluorine, chromium (chromate), and phosphorous (phosphate). The glass can be melted in a Joule Heated Ceramic Melter or a Cold Crucible Induction Melter or a Hot Wall Induction Melter. The waste can be calcined in a separate process step prior to vitrification. The method can increase the waste loading in the glass product. While a preferred embodiment has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

abstract

A mobile heat pipe cooled fast nuclear reactor may be configured for transportation to remote locations and may be able to provide 0.5 to 2 megawatts of power. The mobile heat pipe cooled fast reactor may contain a plurality of heat pipes that are proximate to a plurality of fuel pins inside the reactor. The plurality of heat pipes may extend out of the reactor. The reactor may be configured to be placed in a standard shipping container, and may further be configured to be contained within a cask and attached to a skid for easier transportation.

claims

1. An apparatus for manipulating or modifying an electromagnetic wave or a beam of particles, the apparatus comprising:a first layer of elongated electrical micro or nano conductors;a second layer of elongated electrical micro or nano conductors spaced apart from the first layer and such that in a projection of the second layer into a plane of the first layer the apparatus has a network of projected cross-over junctions between the elongated conductors of the first and second layers;the first and second layers are substantially parallel to a propagation direction of the electromagnetic wave or the beam of particles;means for receiving respective electrical potentials in a tunable way to the micro or nano conductors of the first and second layers for inducing electrical mechanisms in areas between the first and second layers corresponding to the network of projected cross-over points such that scattering of the electromagnetic wave or the beam of particles occurs in said areas;means for varying a relative disposition of the first and second layers of micro or nano conductors; andwherein the means for varying the relative disposition of the first and second layers is tunable for varying a scattering pattern of the apparatus, a form factor of the scattering, or both. 2. An apparatus according to claim 1, wherein the micro or nano conductors have a width in the range of about 1 nanometer to 300 microns. 3. An apparatus according to claim 1, wherein the first and second layers of micro or nano conductors each comprise a subset of multiple substantially parallel conductors. 4. An apparatus according to claim 3, wherein a spacings or pitch between the conductors within each layer is in the range of about 1 nanometer to 500 microns centre-to-centre, while a spacing between the first and second layers is in the range of about 0.5 nanometers to 200 microns between opposed conductor faces. 5. An apparatus according to claim 1, wherein the respective subsets of conductors are supported in or on respective insulating or semiconducting substrate. 6. An apparatus according to claim 1, wherein the conductors are carbon nanotubes of arbitrary helicity or radius, either single or multi-walled. 7. An apparatus according to claim 1, further comprising a connector species in some or all of said areas between the first and second layers corresponding to the network of projected cross-over junctions. 8. An apparatus according to claim 7, wherein the separation of adjacent layers is chosen dependent on the presence and nature of the connector species. 9. An apparatus according to claim 7, wherein a gap between substrates supporting the respective first and second layers is in at least a partial vacuum. 10. An apparatus according to claim 1, further comprising buckyball structures for controlling a gap between the first and second layers. 11. An apparatus according to claim 1, further comprising a separation film of an organic medium or a soft matter spacer interpositioned between the first and second layers for maintaining a gap between the first and second layers. 12. An apparatus according to claim 1, wherein the means for varying the disposition of the first and second layers tunes an angle between alignments of the micro or nano conductors in the respective layers by relatively rotating the first and second layers. 13. An apparatus according to claim 1, wherein the means for receiving the respective electrical potentials receives a tunable potential difference at said areas corresponding to the network of projected cross-over points by varying potentials applied to the individual conductors. 14. An apparatus according to claim 1, wherein the means for varying the disposition of the first and second layers tunes a spacing between the first and second layers. 15. An apparatus according to claim 1, wherein the means for varying the disposition of the first and second layers comprises a nano or micro electromechanical system (NEMS or MEMS). 16. An apparatus according to claim 1, wherein the apparatus functions as a diffraction grating with respect to the electromagnetic wave or the beam of particles for splitting the incident electromagnetic wave or beam of particles. 17. An apparatus according to claim 1, wherein the means for receiving the respective electrical potentials receives oscillating potentials to the micro or nano conductors of the first and second layers, oscillating from positive to negative charge. 18. An apparatus according to claim 17, wherein a frequency of the oscillating potentials is chosen based on characteristics of a beam of charged particles to be manipulated or modified and based on geometrical characteristics of the scattering pattern. 19. A method for manipulating or modifying an electromagnetic wave or a beam of particles, the method comprising the steps of:providing a first layer of elongated electrical micro or nano conductors;providing a second layer of elongated electrical micro or nano conductors spaced apart from the first layer and such that in a projection of the second layer into a plane of the first layer the apparatus has a network of projected cross-over junctions between the elongated conductors of the first and second layers;wherein the first and second layers are substantially parallel to a propagation direction of the electromagnetic wave or the beam of particles; andapplying respective electrical potentials to the micro or nano conductors of the first and second layers for inducing electrical mechanisms in areas between the first and second layers corresponding to the network of projected cross-over points such that scattering of the electromagnetic wave or the beam of particles occurs in said areas;varying a relative disposition of the first and second layers of micro or nano conductors; andtuning the applying of the respective electrical potentials and the varying of the relative disposition of the first and second layers for varying a scattering pattern of the apparatus, a form factor of the scattering, or both. 20. An apparatus according to claim 19, wherein the micro or nano conductors have a width in the range of about 1 nanometer to 4400 microns. 21. An apparatus according to claim 19, wherein the first and second layers of micro or nano conductors each comprise a subset of multiple substantially parallel conductors. 22. An apparatus according to claim 21, wherein a spacings spacing or pitch between the conductors within each layer is in the range of about 1 nanometer to 500 microns centre-to-centre, while a spacing between the first and second layers is in the range of about 0.5 nanometer to 200 microns between opposed conductor faces. 23. An apparatus according to claim 19, wherein the respective subsets of conductors are supported in or on respective insulating or semiconducting substrate. 24. An apparatus according to claim 19, wherein the conductors are carbon nanotubes of arbitrary helicity or radius, either single or multi-walled. 25. An apparatus according to claim 19, further comprising providing a connector species in some or all of said areas between the first and second layers corresponding to the network of projected cross-over junctions. 26. An apparatus according to claim 25, wherein the separation of adjacent layers is chosen dependent on the presence and nature of the connector species. 27. An apparatus according to claim 25, wherein a gap between substrates supporting the respective first and second layers is in at least a partial vacuum. 28. An apparatus according to claim 19, further comprising providing buckyball structures for controlling a gap between the first and second layers. 29. An apparatus according to claim 19, further comprising providing a separation film of an organic medium or a soft matter spacer interpositioned between the first and second layers for maintaining a gap between the first and second layers. 30. An apparatus according to claim 19, wherein the varying of the disposition of the first and second layers comprises tuning an angle between alignments of the micro or nano conductors in the respective layers by relatively rotating the first and second layers. 31. An apparatus according to claim 19, wherein the applying of the respective electrical potentials comprises tuning a potential difference at said areas corresponding to the network of projected cross-over points by varying potentials applied to the individual conductors. 32. An apparatus according to claim 19, wherein the varying of the disposition of the first and second layers comprises tuning a spacing between the first and second layers. 33. An apparatus according to claim 19, wherein the varying of the disposition of the first and second layers comprises utilizing a nano or micro electromechanical system (NEMS or MEMS). 34. An apparatus according to claim 19, wherein the scattering pattern functions as a diffraction grating with respect to the electromagnetic wave or the beam of particles for splitting the incident electromagnetic wave or beam of particles. 35. An apparatus according to claim 19, wherein the applying of the respective electrical potentials comprises applying oscillating potentials to the micro or nano conductors of the first and second layers, oscillating from positive to negative charge. 36. An apparatus according to claim 35, wherein a frequency of the oscillating potentials is chosen based on characteristics of a beam of charged particles to be manipulated or modified and based on geometrical characteristics of the scattering pattern.

052727386

claims

1. A device for monitoring an atmosphere within a containment shell of a nuclear reactor plant, comprising: sample removal means provided in the containment shell; a measuring line connected to the sample removal means for leading a gas sample from the containment shell; a measuring zone located in the measuring line and disposed outside of the containment shell through which the sample is led for measuring the activity of the gas sample; a dilution plant located in the measuring line and disposed int he containment shell for reducing the activity concentration of the gas sample upstream of the measuring zone; the dilution plant being adapted to be connected to a clean, pressure-controlled dilution gas source located outside the containment shell. sampling means for drawing a sample of gas within the atmosphere in the containment; a dilution plant connected to the sampling means for diluting the gas sample with clean dilution gas, the dilution plant being adapted for connection with a source of clean, pressurized dilution gas; a measuring line connected to the dilution plant for removing the diluted gas sample from the containment; and, a measuring zone connected to the measuring line outside of the containment for measuring the activity of the diluted gas sample. sampling gases in a containment shell; diluting the gas sample in a dilution plant with clean, pressurized dilution gas; removing the diluted gas sample from the containment shell; directing the diluted gas sample through a measuring zone; and, measuring selected activity of the diluted gas sample. 2. The device as claimed in claim 1, wherein the dilution gas is heated by means of a heater before introduction into the dilution plant. 3. The device as claimed in claim 1, wherein the dilution plant is provided with a plurality of stages for dilution of the gas sample. 4. An apparatus for monitoring gases within a containment of a nuclear reactor plant, comprising: 5. The apparatus as claimed in claim 4, further comprising a heater to heat the dilution gas before introduction to the dilution plant. 6. The apparatus as claimed in claim 4 wherein the dilution plant comprises a plurality of dilution stages connected in series for diluting the sample gas in steps. 7. A method for monitoring gases within a containment shell of a nuclear reactor plant, comprising the steps of: 8. The method as claimed in claim 7, further comprising the step of heating the dilution gas before diluting the gas sample. 9. The method as claimed in claim 7, wherein the step of diluting the gas sample is performed is several stages.

claims

1. A method of fabricating a fuel rod, comprising the step of providing an effective amount of a metal oxide in the fuel rod to cause generation of steam and mitigate secondary hydriding. 2. A method according to claim 1 , wherein the composition of the metal oxide is such that if hydrogen fraction is above the equilibrium condition for the a metal/metal oxide couple, a back reaction occurs between the hydrogen and the metal oxide to generate steam. claim 1 3. A method according to claim 1 , wherein the metal oxide is selected from oxides of iron, nickel, tin, bismuth, copper, colbalt, chromium, manganese and combinations of such oxides. claim 1 4. A method according to claim 3 , wherein the metal oxide is bismuth oxide. claim 3 5. A method according to claim 1 , wherein the metal oxide is present in an amount ranging from 2 up to 10 grams per fuel rod. claim 1 6. A method according to claim 1 , wherein the metal oxide is present as a coating on an interior surface of cladding of the fuel rod. claim 1 7. A method according to claim 1 , wherein the metal oxide is present as a coating on fuel pellet surfaces. claim 1 8. A method according to claim 1 , wherein the metal oxide is present as individual pellets of a fuel pellet stack, or as wafers. claim 1 9. A method according to claim 8 , wherein the individual pellets or wafers are between fuel pellets. claim 8 10. A method according to claim 8 , wherein the individual pellets or wafers are at the top of the fuel pellet stack. claim 8 11. A method according to claim 8 , wherein the individual pellets or wafers are at the bottom of the fuel pellet stack. claim 8 12. A method according to claim 8 , wherein the individual pellets or wafers are at the top and bottom of the fuel pellet stack. claim 8 13. A method according to claim 1 , wherein the metal oxide is within a container. claim 1 14. A method according to claim 13 , wherein the metal oxide is present as a powder or pellet within said container. claim 13 15. A method according to claim 13 , wherein said container is at the bottom of a fuel pellet stack. claim 13 16. A method according to claim 13 , wherein said container is at the top of a fuel pellet stack. claim 13 17. A method according to claim 13 , wherein said container is at the top and bottom of a fuel pellet stack. claim 13 18. A method according to claim 1 , wherein the metal oxide is distributed intermittently along the fuel rod. claim 1 19. A fuel rod fabricated according to the method of claim 1 . claim 1

description

This application claims priority to Chinese patent application No. 201710428533.3 filed on Jun. 8, 2017, the contents of which are hereby incorporated by reference in their entirety. The present invention relates to nuclear apparatus technology, and more particularly to a device for removing foreign matters in nuclear reactor vessel. Nuclear reactor is an apparatus used for starting, controlling and maintaining the nuclear fission or fusion chain reaction. The reaction rate of the nuclear reactor can be controlled precisely so that the energy of the nuclear reactor is released slowly for the use of people. There are various uses of the nuclear reactor, the most important use is to replace other fuel for producing heat as the steam electric power or the power for running the apparatuses such as aircraft carrier. Reactor pressure vessel is one of the most important apparatuses in the nuclear reactor, due to equipment aging, vibration, impact, accidental falling of connecting bolts, nuts and tools during maintenance and other reasons, foreign matters are inevitably present at the bottom of the reactor pressure vessel. In the existing art, the foreign matters are taken out of the reactor pressure vessel by manpower, specifically, a diver wearing radiation-proof diving suit was sent into the reactor pressure vessel to take the foreign matters out of the reactor pressure vessel, which is costly and risky. Therefore, the present invention provides a device for removing foreign matters in nuclear reactor vessel to solve the problem that foreign matters cannot be safely and easily taken out of the nuclear reactor vessel. According to an embodiment of the present invention, the device for removing foreign objects from nuclear reactor vessel comprises: a suction pipe capable of extending into the nuclear reactor vessel; a suction opening structure disposed at a lower end of the suction pipe, wherein the suction opening structure has a suction opening thereon, and an upper end of the suction opening structure is connected to the suction pipe; an electric valve disposed at a connection of the suction pipe and the suction opening structure; a filter mesh located in the suction pipe and above the electric valve; a suction pump located in the suction pipe and above the filter mesh; a touch switch disposed on the filter mesh; and a drainage pipe; wherein a water inlet of the suction pump is communicated with the suction opening of the suction opening structure, a water outlet of the suction pump is communicated with the outside space of the suction pipe though the drainage pipe, and the electric valve is controlled by the touch switch, specifically, the touch switch controls the electric valve to be opened and closed. In another embodiment according to the previous embodiment, the electric valve comprises a spool with mesh structure. In another embodiment according to the previous embodiment, the device for removing foreign matters in nuclear reactor vessel further comprises a controlling switch disposed on a top portion of the suction pipe. In another embodiment according to the previous embodiment, the device for removing foreign matters in nuclear reactor vessel further comprises an operating handle disposed on the top portion of the suction pipe. In another embodiment according to the previous embodiment, the drainage pipe comprises an upward outlet, preventing the foreign matters flowing with water. In another embodiment according to the previous embodiment, the device for removing foreign matters in nuclear reactor vessel further comprises an alarm disposed on the top portion of the suction pipe, wherein the alarm is connected to and controlled by the touch switch, when the touch switch is triggered and closed, the alarm will inform the operator to check whether there are foreign matters sucked. Compared to the existing art, the present invention has advantages and beneficial effects as follows: 1. The filter mesh and the suction pump are sequentially disposed in the suction pipe above the suction opening structure, so that the foreign matters in the nuclear reactor vessel can be adsorbed onto the filter mesh by the suction pump, an impact force to the filter mesh is generated when the foreign matters fall onto the filter mesh, and the touch switch disposed on the filter mesh is triggered and closed under the impact force, closing the electric valve. The device for removing foreign matters in nuclear reactor vessel in the present invention has a simple structure and is easy for operation, through which foreign matters can be taken out of the reactor vessel even though their specific location is not known. 2. The device for removing foreign matters in nuclear reactor vessel further comprises an alarm disposed on the top portion of the suction pipe, wherein the alarm is connected to and controlled by the touch switch, when the touch switch is triggered and closed, the alarm will inform the operator to check whether there are foreign matters sucked. 3. According to another aspect of the invention, the spool of the electric valve is of a mesh structure. Thus, when the electric valve is closed, it does not carry water flow and can prevent foreign matters falling off the filter mesh. Furthermore, a mesh-structure spool will not be basically subject to flow resistance when it is closed, and can be instantly closed when foreign matters touch the filter mesh, thus preventing foreign matters leaking outside of the mesh-structure spool. While normal electric valves are always used to completely shut down or control flow rate of fluid, the present invention only takes advantage of their rotation and control structure. Compared with the existing mechanical grasping structure, the present invention takes a mesh-structure spool to prevent foreign matters from being leaked, thereby facilitating the operation and holding of foreign matters. For making the above and other purposes, features and benefits become more readily apparent to those ordinarily skilled in the art, the preferred embodiments and the detailed descriptions with accompanying drawings will be put forward in the following descriptions. The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. As shown in the FIGURE, a device for removing foreign matters in nuclear reactor vessel comprises a suction pipe 1 capable of extending into the nuclear reactor vessel; a suction opening structure 2 disposed at a lower end of the suction pipe 1, wherein the suction opening structure 2 has a suction opening at its lower end, an upper end of the suction opening structure 2 is connected to the suction pipe 1; an electric valve 3 disposed at a connection of the suction pipe 1 and the suction opening structure 2; a filter mesh 4 located in the suction pipe 1 and above the electric valve 3; a suction pump 5 located in the suction pipe 1 and above the filter mesh 4; a touch switch 6 disposed on the filter mesh 4; and a drainage pipe 9; wherein a water inlet of the suction pump 1 is communicated with the suction opening of the suction opening structure 2, a water outlet of the suction pump 2 is communicated with the outside space of the suction pipe 1 though the drainage pipe 9, the electric valve 3 is controlled by the touch switch 6, the electric valve 3 comprises a spool with mesh structure, the suction opening structure 2 is trumpet-shaped to form a flow channel for foreign matters suction, specifically, the diameter of the suction opening structure 2 increases from the upper end to the lower end thereof. Further, a controlling switch 11 disposes on a top portion of the suction pipe 1 to control the suction pump 5 to be open or closed. Further, an operating handle 12 disposes on the top portion of the suction pipe 1, operator is able to send the device into the nuclear reactor vessel and move it by operating the operating handle 12 so as to take out of the foreign matters. Further, the drainage pipe 9 comprises an upward outlet, preventing the foreign matters flowing with water. Further, an alarm disposed on the top portion of the suction pipe 1, wherein the alarm is connected to and controlled by the touch switch 6, when the touch switch 6 is triggered and closed, the alarm will inform the operator to check whether there are foreign matters sucked. The filter mesh 4 and the suction pump 5 are sequentially disposed in the suction pipe 1 above the suction opening structure 2, so that the foreign matters in the nuclear reactor vessel can be adsorbed onto the filter mesh 4 by the suction pump 5, an impact force to the filter mesh 4 is generated when the foreign matters fall onto the filter mesh 4, and the touch switch 6 disposed on the filter mesh 4 is triggered and closed under the impact force, then the electric valve 3 is closed by the touch switch 6. The device for removing foreign matters in nuclear reactor vessel in the present invention has a simple structure and is easy for operation, through which foreign matters can be taken out of the reactor vessel even though their specific location is not known. According to another aspect of the invention, the spool of the electric valve 3 is of a mesh structure. Thus, when the electric valve 3 is closed, it does not carry water flow and can prevent foreign matters falling off the filter mesh 4. Furthermore, a mesh-structure spool will not be basically subject to flow resistance when it is closed, and can be instantly closed when foreign matters touch the filter mesh 4, thus preventing foreign matters leaking outside of the mesh-structure spool. While normal electric valves are always used to completely shut down or control flow rate of fluid, the present invention only takes advantage of their rotation and control structure. Compared with the existing mechanical grasping structure, the present invention takes a mesh-structure spool to prevent foreign matters from being leaked, thereby facilitating the operation and holding of foreign matters. For making the above and other purposes, features and benefits become more readily apparent to those ordinarily skilled in the art, the preferred embodiments and the detailed descriptions with accompanying drawings will be put forward in the following descriptions. While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.

description

This application is a Continuation of co-pending U.S. patent application Ser. No. 13/561,824, filed Jul. 30, 2012, which claims foreign priority benefit of Japanese Patent Application No. 2011-170288 filed Aug. 3, 2011 and Japanese Patent Application No. 2012-137921 filed Jun. 19, 2012, all of which are hereby incorporated by reference herein in their entirety. 1. Field of the Invention Disclosed aspects of the embodiments relate to a wavefront measuring apparatus, a wavefront measuring method, and a computer-readable medium storing a program for use in them. More particularly, the disclosed aspects relate to a wavefront measuring apparatus, a wavefront measuring method, and a program, which are adapted for deriving wavefront information from a periodic pattern (periodic pattern of light) that has been modulated by a specimen (i.e., an object to be analyzed). 2. Description of the Related Art In the optical metrology, information of a specimen is often derived by analyzing modulation of a periodic pattern. As analytical techniques for the periodic pattern, there are known a phase shifting method and a windowed Fourier transform method. The phase shifting method and the windowed Fourier transform method are described in brief by taking, as an example, a periodic pattern I(x, y) expressed by the following formula (1). For simplicity, a one-dimensional periodic pattern is discussed below, but the following discussion is similarly applied to a two-dimensional periodic pattern as well:I(x,y)=a(x,y)+b(x,y)cos [ωxx+φ(x,y)]  (1)where a(x, y) is a background irradiance, b(x, y) is an amplitude distribution of the periodic pattern, ωx is a spatial carrier frequency, and φ(x, y) is a phase distribution or a differential phase distribution induced by the specimen. The phase shifting method is a technique of measuring the wavefront of light having transmitted through a specimen by using a plurality of periodic patterns that have phases shifted from one another, and obtaining information of the specimen. The phase shifting method is featured in that the information of the specimen is independently obtained from the intensity of the light detected for each of pixels. Let consider, as an example, the case of extracting the information of the specimen from three periodic patterns having phases shifted from one another, which are expressed by the following formulae (2): I 1 ⁡ ( x , y ) = a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos ⁡ [ ω x ⁢ x + φ ⁡ ( x , y ) ] ⁢ ⁢ I 2 ⁡ ( x , y ) = a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos [ ω x ⁢ x + φ ⁡ ( x , y ) + 2 ⁢ π ⁢ 1 3 ] ⁢ ⁢ I 3 ⁡ ( x , y ) = a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos ⁡ [ ω x ⁢ x + φ ⁡ ( x , y ) + 2 ⁢ π ⁢ 2 3 ] ( 2 ) According to The Japan Society of Applied Physics, Atsushi Momose, Wataru Yashiro, Yoshihiro Takeda, Yoshio Suzuki and Tadashi Hattori, “Phase Tomography by X-ray Talbot Interferometry for Biological Imaging”, Japanese Journal of Applied Physics, Vol. 45, No. 6A, pp. 5254-5256 (2006), Japan, the phase distribution or the differential phase distribution induced by a specimen is obtained from the following formula (3). In the formula (3), arg[•] denotes a phase component of the expression within [ ]. φ ⁡ ( x , y ) = arg [ ∑ k = 1 3 ⁢ I k ⁡ ( x , y ) ⁢ exp [ - 2 ⁢ πⅈ ⁢ k - 1 3 ] ] ( 3 ) Because the obtained phase distribution or differential phase distribution is given as a value wrapped between −π and π, it is to be unwrapped. Thus, when the periodic pattern capable of being expressed by the formula (1) is used, the wavefront information of the light having transmitted through the specimen is derived by the phase shifting method if there are three or more periodic patterns, and the phase distribution or the differential phase distribution of the specimen is obtained. On the other hand, the windowed Fourier transform method is featured in that the wavefront information of the light having transmitted through the specimen may be derived from even one periodic pattern. Details of the windowed Fourier transform method is discussed in Elsevier, Qian Kemao, “Two-dimensional windowed Fourier transform for fringe pattern analysis: Principles, applications and implementations”, Volume 45, Issue 2, pages 304-317, Optics and Lasers in Engineering, 2007, The Netherlands. The windowed Fourier transform method is described in brief below. The formula (1) is rewritten into the following formulae (4). I ⁡ ( x , y ) = a ⁡ ( x , y ) + c ⁡ ( x , y ) ⁢ exp ( ⅈω x ⁢ x ] + c * ⁡ ( x , y ) ⁢ exp ⁡ [ - ⅈω x ⁢ x ] ⁢ ⁢ c ⁡ ( x , y ) = b ⁡ ( x , y ) 2 ⁢ exp ⁡ [ ⅈφ ⁡ ( x , y ) ] , ⁢ c * ⁡ ( x , y ) = b ⁡ ( x , y ) 2 ⁢ exp ⁡ [ - ⅈφ ⁡ ( x , y ) ] ( 4 ) According to the windowed Fourier transform method, the wavefront information of the light having transmitted through the specimen is derived by locally cutting out the periodic pattern with a window function, and determining Fourier coefficients of a zeroth-order spectrum and a spatial carrier frequency. In other words, a(x, y), c(x, y) and c*(x, y) are obtained by the following formulae (5):a(x,y)=∫∫I(η,ν)g(μ−x,ν−y)dμdνc(x,y)=∫∫I(η,ν)g(μ−x,ν−y)exp[−iωxμ]dμdνc*(x,y)=∫∫I(η,ν)g(μ−x,ν−y)exp[iωxμ]dμdν  (5)where the window function is g(x, y), and μ and ν are each a variable of integration. Further, as in the phase shifting method, because the obtained wavefront information is given as a value wrapped between −π and π, it is to be unwrapped. In the phase shifting method, when the periodic pattern is expressed by the formula (1), at least three periodic patterns having phases shifted from one another are employed for the reason that there are three unknowns. More periodic patterns are to be employed in order to obtain phase distributions or differential phase distributions in two directions from two-dimensional periodic patterns. Meanwhile, with the windowed Fourier transform method, the information of the specimen is obtained from one periodic pattern. However, the wavefront information of the light is not independently derived from the detection result for each pixel, but by using the detection results of surrounding pixels as well. Accordingly, accuracy of the wavefront information obtained with the windowed Fourier transform method is lower than that obtained with the phase shifting method. In view of the problems described above, the present disclosure provides a wavefront measuring method, a wavefront measuring apparatus, and a computer-readable medium storing a program, which may accurately derive wavefront information by using the windowed Fourier transform method even from fewer periodic patterns than used in the phase shifting method. According to an embodiment, there is provided a wavefront measuring apparatus including an optical element arranged to form a periodic pattern by light emitted from a light source, a detector having a plurality of pixels to detect the light that enters the detector from the optical element, and a computer configured to compute, based on detection results of the detector, wavefront information at a plurality of positions in a wavefront of the light having transmitted through or having been reflected by a specimen, wherein the detector detects a first periodic pattern formed by the light from the optical element, and a second periodic pattern formed by the light from the optical element and having a phase shifted with respect to a phase of the first periodic pattern, and wherein the computer computes the wavefront information at one of the plural positions by using a detection result detected in a first pixel of the plural pixels at time of detecting the first periodic pattern, a detection result detected in a second pixel of the plural pixels at the time of detecting the first periodic pattern, the second pixel being positioned within three pixels from the first pixel, and a detection result detected in the first pixel at time of detecting the second periodic pattern. Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. First and second embodiments will be described below with reference to the accompanying drawings. It is to be noted that, in the drawings, the same components are denoted by the same reference numerals and duplicate descriptions are omitted. The first and second embodiments are in common in that a periodic pattern of light (i.e., a periodic pattern) is detected plural times, a virtual periodic pattern is obtained from the plural periodic patterns, and information regarding the wavefront of the light is derived by using the virtual periodic pattern. The first embodiment is described in connection with a wavefront measuring apparatus in which the wavefront of light having transmitted through a specimen is measured in accordance with the phase shifting method. The wavefront measuring apparatus according to this embodiment is an X-ray imaging apparatus (hereinafter referred to also as an “X-ray phase imaging apparatus”), which performs X-ray phase imaging by employing the Talbot-Lau interference method. However, embodiments are limited to neither the Talbot-Lau interference method nor the wavefront measuring apparatus that performs the X-ray phase imaging. The embodiments may also be applied to general techniques for measuring modulation of a periodic pattern, the modulation being caused by a specimen. Because the X-ray phase imaging apparatus employing the Talbot-Lau interference method is discussed in detail in SPIE, Timm Weitkamp, Christian David, Christian Kottler, Oliver Bunk, and Franz Pfeiffer, “Tomography with grating interferometers at low-brilliance sources”, Proceedings of SPIE Vol. 6318, 63180S-1 (2006), USA an outline is described here. FIG. 1 is a schematic view of the wavefront measuring apparatus (X-ray phase imaging apparatus) according to the first embodiment, the apparatus employing the Talbot-Lau interference method. The wavefront measuring apparatus 1 according to the first embodiment includes an X-ray source 110 as a light source, a source grating 120 for dividing X-ray radiation from the X-ray source 110 into a plurality of beams, a phase-type diffraction grating (hereinafter referred to as a “phase grating”) 140, and a shield grating 150. The phase grating 140 and the shield grating 150 are optical elements for forming a periodic pattern with the X-ray beams from the source grating 120. The wavefront measuring apparatus 1 further includes a detector 160 for detecting an X-ray pattern from the shield grating 150, and a computer 170 serving as an arithmetic unit (processing unit) that executes calculations on the basis of detection results of the detector 160. In addition, the wavefront measuring apparatus 1 includes an actuator 180 as a moving unit that moves at least one of the source grating 120, the diffraction (phase) grating 140, the shield grating 150, and the detector 160. The operation of the wavefront measuring apparatus including those components is described below. The X-ray radiation from the light source (X-ray source) 110 is delivered to the source grating 120. The source grating 120 has an X-ray transmitting portion and an X-ray shielding portion, and it divides the X-ray radiation from the X-ray source 110 into plural X-ray beams. The X-ray beam divided by the source grating 120 is delivered to impinge upon a specimen 130, and the X-ray having transmitted through the specimen 130 is diffracted by the diffraction (phase) grating 140. The phase grating 140 is a phase-type diffraction grating for periodically changing the phase of the X-ray. The phase grating 140 has a phase reference portion and a phase shift portion, which are periodically arrayed. When the phase grating 140 diffracts the X-ray having transmitted through the specimen 130, an interference pattern of the light (X-ray) is formed at a predetermined distance that is called the Talbot distance. That interference pattern is a periodic pattern (X-ray periodic pattern). The term “periodic pattern” in the present specification includes a pattern that does not have a fixed (predetermined) period even when the specimen is not arranged between the light source and the periodic pattern. For example, a pattern in which the period is gradually changed as a distance from a pattern center increases is also called the periodic pattern. Accordingly, as used herein the term “period pattern” may include patterns of a fixed (predetermined) period or patterns of a variable period. The shield grating 150 is arranged at a position spaced from the phase grating 140 by the Talbot distance such that the interference pattern is formed on the shield grating 150. The shield grating 150 has a light (X-ray) shielding portion (hereinafter referred to as a “shielding portion”) and a light (X-ray) transmitting portion (hereinafter referred to as a “transmitting portion”), which are periodically arrayed. A period at which the shielding portion and the transmitting portion are arrayed slightly differs from a period of the interference pattern formed on the shield grating 150. Therefore, the X-ray having transmitted through the shield grating 150 forms a moiré that is an X-ray periodic pattern. In this embodiment, the moiré formed through the phase grating 140 and the shield grating 150 is detected, and information of the specimen is obtained from the moiré. It should be understood that in general a moiré is created, for example, when two gratings have slightly different mesh sizes (grating periods), as described above, but the moiré may also be created when two gratings are spatially overlaid at an angle. The detector 160 has a plurality of pixels for detecting the intensity of light (X-ray) and detects the moiré formed by the light having transmitted through the shield grating 150. Based on detection results of the detector 160, the computer 170 computes wavefront information at plural positions of a wavefront of the light forming the moiré. The wavefront information computed here represents at least one of phase, amplitude, and scattering parameters included in the wavefront. Because the light forming the moiré is modulated by the specimen 130, the wavefront information computed by the computer 170 contains information of the specimen 130. An analytical method executed by the computer 170 to obtain the wavefront information will be described later. The actuator 180 moves or rotates the interference pattern and the shield grating 150 relatively by displacing at least one of the source grating 120, the phase grating 140, and the shield grating 150. The actuator 180 may perform both the movement (translation) and the rotation. As a result, the phase of the moiré is shifted. The displacement may be a movement changing a position or a rotational movement changing a tilt. While the interference pattern and the shield grating are relatively moved and/or rotated in this embodiment, a moving unit is just to be capable of shifting the phase of the moiré (interference pattern). For example, the phase of the moiré may be shifted by moving the detector 160. The analytical method of computing the wavefront information with the computer 170 in this embodiment will be described below. As mentioned above, the analytical method based on the phase shifting method is described in this embodiment. The computer 170 in this embodiment computes the wavefront information by using a first periodic pattern (first X-ray periodic pattern) detected by the detector 160, and a second periodic pattern (second X-ray periodic pattern) having a phase different from that of the first periodic pattern, thereby obtaining the information of the specimen. The first periodic pattern and the second periodic pattern are each the moiré formed by the light having transmitted through the shield grating 150. In this embodiment, the second periodic pattern is detected by, after detecting the first periodic pattern, moving the interference pattern and the shield grating relatively by the actuator 180 to shift the phase of the moiré, and detecting the moiré again by the detector 160. However, if the relative movement distance between the interference pattern and the shield grating is equal to an integer multiple of the period of the interference pattern or the shield grating, the phase of the formed moiré is not shifted (namely, a shift amount is an integer multiple of 2π). Therefore, the second periodic pattern is not detected (namely, the first periodic pattern is detected again). For that reason, when the phase of the moiré is shifted by relatively moving the interference pattern and the shield grating to change a positional relationship therebetween, the relative movement is performed such that the relative movement distance between the interference pattern and the shield grating is not equal to an integer multiple of the period of the interference pattern or the shield grating. Here, the moiré intensity of the first periodic pattern is denoted by I1 and the moiré intensity of the second periodic pattern is denoted by I2. In this embodiment, the information of the specimen is obtained from I1 and I2 expressed by the following formulae (6):I1(x,y)=a(x,y)+b(x,y)cos [ωxx+φ(x,y)]I2(x,y)=a(x,y)+b(x,y)cos [ωx(x+α)+φ(x,y)]  (6)where a(x, y) is a background periodic pattern, b(x, y) is an amplitude distribution of the moiré, ωx is a spatial carrier frequency, ωxα is a phase shift amount (phase difference) between I4 and I2, and φ(x, y) is a differential phase distribution of the specimen. Further, a unit of each of x and y is a pixel. Virtual moirés I3 and I4 expressed by the following formulae (7) are obtained from I1 and I2:I3(x,y)=I1(x−m,y)I4(x,y)=I2(x−n,y)  (7) In the formulae (7), m and n are each an integer other than 0, and they may be the same number or different numbers. When changes of a(x, y), b(x, y) and φ(x, y) are sufficiently moderate with respect to ωx, the formulae (7) may be rewritten into the following formulae (8): I 3 ⁡ ( x , y ) = ⁢ a ⁡ ( x - m , y ) + b ⁡ ( x - m , y ) ⁢ cos ⁡ [ ω x ⁡ ( x - m ) + φ ⁡ ( x , y ) ] ≈ ⁢ a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos ⁡ [ ω x ⁡ ( x - m ) + φ ⁡ ( x , y ) ] ⁢ ⁢ I 4 ⁡ ( x , y ) = ⁢ a ⁡ ( x - m , y ) + b ⁡ ( x - m , y ) ⁢ cos ⁡ [ ω x ⁡ ( x - m + α ) + φ ⁡ ( x - m , y ) ] ≈ ⁢ a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos ⁡ [ ω x ⁡ ( x - m + α ) + φ ⁡ ( x , y ) ] ( 8 ) The formulae (6), (7) and (8) are rewritten into the following formulae (9): I 1 ⁡ ( x , y ) = a ⁡ ( x , y ) + b ⁡ ( x , y ) 2 ⁢ ( exp ⁡ [ ⅈω x ⁢ x ] ⁢ exp ⁡ [ ⅈφ ⁡ ( x , y ) ] + exp ⁡ [ - ⅈω x ⁢ x ] ⁢ exp ⁡ [ - ⅈφ ⁡ ( x , y ) ] ) ⁢ ⁢ I 2 ⁡ ( x , y ) = a ⁡ ( x , y ) + b ⁡ ( x , y ) 2 ⁢ ( exp ⁡ [ ⅈ ⁡ ( ω x ⁡ ( x + α ) ) ] ⁢ exp ⁡ [ ⅈφ ⁡ ( x , y ) ] + exp ⁡ [ - ⅈ ⁡ ( ω x ⁡ ( x + α ) ) ] ⁢ exp ⁡ [ - ⅈφ ⁡ ( x , y ) ] ) ⁢ ⁢ I 3 ⁡ ( x , y ) ≈ a ⁡ ( x , y ) + b ⁡ ( x , y ) 2 ⁢ ( exp ⁡ [ ⅈ ⁡ ( ω x ⁡ ( x - m ) ) ] ⁢ exp ⁡ [ ⅈφ ⁡ ( x , y ) ] + exp ⁡ [ - ⅈ ⁡ ( ω x ⁡ ( x - m ) ) ] ⁢ exp ⁡ [ - ⅈφ ⁡ ( x , y ) ] ) ⁢ ⁢ I 4 ⁡ ( x , y ) ≈ a ⁡ ( x , y ) + b ⁡ ( x , y ) 2 ⁢ ( exp ⁡ [ ⅈ ⁡ ( ω x ⁡ ( x - m + α ) ) ] ⁢ exp ⁡ [ ⅈφ ⁡ ( x , y ) ] + exp ⁡ [ - ⅈ ⁡ ( ω x ⁡ ( x - m + α ) ) ] ⁢ exp ⁡ [ - ⅈφ ⁡ ( x , y ) ] ) ( 9 ) Further, the formulae (9) is expressed by the following formula (10) in the form of a matrix: ( I 1 ⁡ ( x , y ) I 2 ⁡ ( x , y ) I 3 ⁡ ( x , y ) I 4 ⁡ ( x , y ) ) ≈ ( 1 exp ⁡ [ ⅈω x ⁢ x ] exp ⁡ [ - ⅈω x ⁢ x ] 1 exp ⁡ [ ⅈ ⁡ ( ω x ⁡ ( x + α ) ) ] exp ⁡ [ - ⅈ ⁡ ( ω x ⁡ ( x + α ) ) ] 1 exp ⁡ [ ⅈω x ⁡ ( x - m ) ] exp ⁡ [ - ⅈω x ⁡ ( x - m ) ] 1 exp ⁡ [ ⅈ ⁡ ( ω x ⁡ ( x - m + α ) ) ] exp ⁡ [ - ⅈ ⁡ ( ω x ⁡ ( x - m + α ) ) ] ) ⁢ ( a ⁡ ( x , y ) c ⁡ ( x , y ) c * ( x , y ) ) ⁢ ⁢ ⁢ c ⁡ ( x , y ) = b ⁡ ( x , y ) 2 ⁢ exp ⁡ [ ⅈφ ⁡ ( x , y ) ] , ⁢ ⁢ c * ⁡ ( x , y ) = b ⁡ ( x , y ) 2 ⁢ exp ⁡ [ - ⅈφ ⁡ ( x , y ) ] ( 10 ) Accordingly, given that a pseudo inverse matrix of a matrix A is A−1, a(x, y), c(x, y) and c*(x, y) are obtained from the following formula (11), while b(x, y) and φ(x, y) are obtained from c(x, y) and c*(x, y): ( a ⁡ ( x , y ) c ⁡ ( x , y ) c * ⁡ ( x , y ) ) ≈ ( 1 exp ⁡ [ ⅈω x ⁢ x ] exp ⁡ [ - ⅈω x ⁢ x ] 1 exp ⁡ [ ⅈ ⁡ ( ω x ⁡ ( x + α ) ) ] exp ⁡ [ - ⅈ ⁡ ( ω x ⁡ ( x + α ) ) ] 1 exp ⁡ [ ⅈω x ⁡ ( x - m ) ] exp ⁡ [ - ⅈω x ⁡ ( x - m ) ] 1 exp ⁡ [ ⅈ ⁡ ( ω x ⁡ ( x - m + α ) ) ] exp ⁡ [ - ⅈ ⁡ ( ω x ⁡ ( x - m + α ) ) ] ) - 1 ⁢ ( I 1 ⁡ ( x , y ) I 2 ⁡ ( x , y ) I 3 ⁡ ( x , y ) I 4 ⁡ ( x , y ) ) ( 11 ) Thus, the wavefront information at one position (x, y) is obtained from the first periodic pattern (I1) and the second periodic pattern (I2). Because the Talbot-Lau interferometer is a shearing interferometer, differentiated data of the wavefront information (i.e., differential wavefront information) is obtained. Therefore, a differential phase image of the specimen is obtained by mapping the φ(x, y). Moreover, a phase image is obtained from the differential phase image, and an absorption image and a scattering image of the specimen are obtained respectively from a(x, y) and b(x, y). While φ(x, y) obtained in this embodiment represents a differential phase distribution of the specimen because the Talbot-Lau interferometer is a shearing interferometer, φ(x, y) represents a phase distribution of the specimen when an interferometer other than the shearing interferometer, such as a Michelson interferometer or a Fizeau interferometer, is used. Therefore, a phase image is obtained by mapping φ(x, y) that has been obtained with the interferometer other than shearing interferometer. FIGS. 2A and 2B are each a conceptual view illustrating the analytical method executed by the computer 170 in this embodiment. FIG. 2A illustrates the concept of deriving the information of the specimen by, as described above, obtaining I3 from I1 and I4 from I2, respectively, and by carrying out the phase shifting method based on the actually detected moiré (I1, I2) and the virtual moiré (I3, I4). I3 is obtained from I4 by a method using the formula (7), and the intensity of X-ray (light) at particular coordinates (x, y) within I3 is provided as the intensity of X-ray at particular coordinates (x−m, y) within I1, which differ from the particular coordinates (x, y). I4 is similarly obtained from I2. FIG. 2B illustrates an analytical method executed by the computer 170 in accordance with the above-described concept. Thus, FIG. 2B is a conceptual view illustrating the analytical method executed by the computer 170 in this embodiment on condition that m and n are each +1. As illustrated in FIG. 2B, the information of the specimen at (x, y) is obtained by carrying out the phase shifting method based on the detection results of the X-ray intensity at (x, y) in I1, (x, y) in I2, (x+1, y) in I1, which is given as (x, y) in I3, and (x+1, y) in I2, which is given as (x, y) in I4. To explain the analytical method used in this embodiment in another way, a pixel where the X-ray intensity at (x, y) is detected is defined as a first pixel, and a pixel where the X-ray intensity at (x−m, y) is detected is defined as a second pixel. Further, m and n are defined as the same value. In this embodiment, the wavefront information is derived by restoring phases on condition that a detection result (I1(x, y)) of the first pixel at the time of detecting the first periodic pattern (I1), a detection result (I1(x+m, y)) of the second pixel at the time of detecting I1, a detection result (I2(x, y)) of the first pixel at the time of detecting the second periodic pattern (I2), and a detection result (I2(x+n, y)) of the second pixel at the time of detecting I2 are regarded respectively as detection results of the first pixel ((x, y)) at the times of detecting I1, I3, I2 and I4. Here, the expression “restoring phases on condition that those detection results are regarded respectively as detection results of the first pixel ((x, y)) at the times of detecting I1, I3, I2 and I4” implies that phases are restored by using a calculation method used in the phase shifting method by regarding the above-mentioned four detection results respectively as detection results of the first pixel ((x, y)) at the times of detecting I1, I3, I2 and I4. The calculation method used in the phase shifting method may be executed by using the above-mentioned formula (11) or another calculation formula. In such a manner, the wavefront information of the X-ray (light) having entered the first pixel is derived. Furthermore, the phase shifting method may be carried out by regarding I1(x, y), I1(x+m, y), I2(x, y), and I2(x+n, y) respectively as detection results of the second pixel at the times of detecting I1, I3, I2 and I4. In that case, the wavefront information of the X-ray (light) having entered the second pixel is derived. However, the derived wavefront information is the same regardless of whether I1(x, y), I1(x+m, y), I2(x, y), and I2(x+n, y) are regarded as detection results of the first pixel or the second pixel. Alternatively, m and n may take different values from each other. For example, a similar analysis to that in this embodiment may be executed by using the detection result of the first pixel at the time of detecting I1, the detection result of the second pixel at the time of detecting I1, the detection result of the first pixel at the time of detecting I2, and the detection result of a pixel, which is neither the first pixel nor the second pixel, at the time of detecting I2. In that case, the phase shifting method may be carried out by regarding the above-mentioned detection results respectively as the detection results of the first pixel at the times of detecting I1, I3, I2 and I4. Moreover, even when the phase difference (ωxα) between I1 and I2 is equal to a phase difference between the light detected in the first pixel and the light detected in the second pixel, the phase shifting method may be carried out by using I1(x, y), I1(x+m, y), I2(x, y), and I2(x+n, y). In that case, I1(x+m, y) and I2(x, y) are the same (precisely speaking, they slightly differ from each other because the X-rays having transmitted through different portions of the specimen are detected). In view of that point, the phase shifting method may be carried out by regarding one of three (i.e., I1(x+m, y), I2(x, y), and a mean of I1(x+m, y) and I2(x, y)) as I2(x, y), I1(x, y) as I1(x, y), and I2(x+n, y) as I3(x, y), respectively. When a formula representing the moiré has three unknowns as in the formula (1), the computer 170 in this embodiment may execute the analytical method if there are three or more moirés including a virtual moiré. Furthermore, if there are three or more moirés including a virtual moiré, the phase shifting method may be carried out on condition that m and n are each an integer other than 0, as described above, without being limited to +1. However, a smaller absolute value of each of m and n is more beneficial because changes of a(x, y), b(x, y) and φ(x, y) become more moderate. A beneficial range of the absolute value of each of m and n is 1 to 3, and a more beneficial range is just 1. Even more beneficially, m=n is satisfied. When the absolute value of each of m and n is 3, the second pixel is located at a three-pixel position counting from the first pixel. When the absolute value of each of m and n is 1, the second pixel is located adjacent to the first pixel. In other words, when the first pixel and the second pixel are adjacent to each other, the second pixel is located at a one-pixel position counting from the first pixel. Phase shift amounts of periodic patterns used in a general phase shifting method are beneficially the same. For example, when an analysis is executed by using four moirés, phases of the four moirés are beneficially shifted by the same amount, i.e., (½)π. Similarly, it is beneficial in this embodiment that the phase shifting amounts of I1, I2, I3 and I4 are the same. Thus, given that m=n=±1 is held and a period of the moiré (periodic pattern) in units of pixel size is P (P=4 when the period of the moiré is 80 μm and the pixel size is 20 μm), the analysis is executed by using I2 and I2, which satisfy α=P/2. In short, according to this embodiment, the information of the specimen is obtained by computing the first virtual periodic pattern (I3) and the second virtual periodic pattern (I4) from the first periodic pattern (I4) and the second periodic pattern (I2), respectively, and by applying the phase shifting method to those four periodic patterns. The analytical method for the first periodic pattern and the second periodic pattern by the computer 170 has been described above. The above-described calculations may be executed on the computer 170 by installing, in the computer 170, a program that instructs the computer 170 to execute the above-described calculations. While, in this embodiment, a moiré is formed by using the shield grating and the moiré is detected and analyzed, an interference pattern, not a moiré, may be directly detected and analyzed in which case shield grating is not needed. By using the shield grating as in this embodiment, a detector having a resolution distance larger than the pitch of the interference pattern may be used. A method of deriving the wavefront information by using a wavefront measuring method based on the windowed Fourier transform method is described in a second embodiment. The configuration of the second embodiment is the same as that of the first embodiment except for a calculation method executed by a computer. As in the first embodiment, a computer in the second embodiment derives the wavefront information by computing virtual periodic patterns from both the first periodic pattern detected by the detector 160 and the second periodic pattern having a phase difference with respect to the first periodic pattern, and by analyzing the virtual periodic patterns. However, the second embodiment differs from the first embodiment in a method of computing the virtual periodic patterns and in an analytical method of computing the wavefront information from the virtual periodic patterns. Furthermore, as in the first embodiment, the first periodic pattern and the second periodic pattern are each a periodic pattern of a moiré that is formed by light having transmitted through the shield grating 150. In the second embodiment, the moiré of the first periodic pattern is denoted by I5, and the moiré of the second periodic pattern is denoted by I6. In this embodiment, the wavefront information is derived from I5 and I6 expressed by the following formulae (12):I5(x,y)=a(x,y)+b(x,y)cos [ωxx+φ(x,y)]I6(x,y)=a(x,y)+b(x,y)cos [ωx(x+α)+φ(x,y)]  (12)where ωxα is a phase difference between I5 and I6, and α is an integer other than 0. A virtual moiré I(x, y) is computed by combining the moirés I5(x, y) and I6(x, y) with each other. The virtual moiré computed by combining the moirés is also referred to as a “composite moiré (composite periodic moiré”) hereinafter. When the information of the specimen at a pixel (x0, y0) is to be obtained, I(x, y) is expressed, for example, by the following formula (13): I ⁡ ( x , y ) = { I 5 ⁡ ( x , y ) , for ⁢ ⁢ x ≤ x 0 + [ P - α 2 ] I 6 ⁡ ( x - α , y ) , for ⁢ ⁢ x ≥ x 0 + [ P - α 2 ] + 1 ( 13 ) where [A] is a floor function and it indicates a maximum integer equal to or less than A (e.g., [2.5]=2, and [2]=2). Further, P represents a moiré period in units of pixel size. When P−α is an even number, the following formula (14) may be used: I ⁡ ( x , y ) = { I 5 ⁡ ( x , y ) , for ⁢ ⁢ x ≤ x 0 + [ P - α 2 ] - 1 I 6 ⁡ ( x - α , y ) , for ⁢ ⁢ x ≥ x 0 + [ P - α 2 ] ( 14 ) A differential phase image is obtained from the computed I(x, y) in accordance with the formulae (5). While various window functions may be optionally used as the window function, a Gauss function is used in this embodiment. In this embodiment, the information of the specimen is derived from the Fourier coefficients after locally cutting out the moiré with the window function. However, the information of the specimen may be obtained by taking the Fourier transform of the moiré, cutting out peaks of a Fourier spectrum, and taking the inverse Fourier transform to cancel a tilt attributable to the moiré. Such a process is expressed by the following formula (15):a(x,y)=−1[IS(ξ,η)×G(ξ,η)]c(x,y)=exp[−iωxx]×−1[IS(ξ,η)×G(ξ−ωx,η)]c*(x,y)=exp[iωxx]×−1[IS(ξ,η)×G(ξ+ωx,η)]  (15)where G(ζ, η) is a window function, IS(ζ, η) is a Fourier spectrum of the moiré I(x, y), ζ and η are each a spatial frequency. F−1 represents the inverse Fourier transform. FIG. 3 is a conceptual view illustrating the analytical method executed by the computer in this embodiment. FIG. 3 illustrates the concept of computing I(x, y) by using I5(x, y) and I6(x, y), as described above. While α=2 and P=4 are held and P−α is an even number, the formula (13) is used in FIG. 3. To explain the analytical method used in this embodiment in another way, a pixel where the X-ray intensity at (x0, y) is detected is defined as a first pixel, and a pixel where the X-ray intensity at (x0−1, y) is detected is defined as a second pixel. In this embodiment, a detection result (I5(x0, y)) of the first pixel at the time of detecting I5 is given as a detection result (I(x0, y)) of the first pixel at the time of detecting I, and a detection result (I5(x0−1, y)) of the second pixel at the time of detecting I5 is given as a detection result (I(x0−1, y)) of the second pixel at the time of detecting I. Further, a detection result (I6(x0, y)) of the first pixel at the time of detecting I6 is given as a detection result (I(x0+P−α, y)) of a pixel, which is neither the first pixel nor the second pixel, at the time of detecting I. In such a manner, the composite moiré I is computed by using I5 and I6. Moreover, the wavefront information of the X-ray at one position (x0, y) is computed by using the composite moiré I and the Fourier transform. Thus, the information of the specimen is obtained. Stated another way, in this embodiment, the detection result of the first pixel at the time of detecting the first periodic pattern, the detection result of the second pixel at the time of detecting the first periodic pattern, and the detection result of the first pixel at the time of detecting the second periodic pattern are regarded as being originated from one periodic pattern (i.e., a composite periodic pattern). The information of the specimen is then derived by taking the Fourier transform of the composite periodic pattern. The X-ray entering the first pixel at the time of detecting I5 and the X-ray entering the first pixel at the time of detecting I6 are the X-rays that have transmitted through the specimen at (substantially) the same position. Therefore, the information of the specimen given by the X-ray entering the first pixel at the time of detecting I5 and the information of the specimen given by the X-ray entering the first pixel at the time of detecting I6 are (substantially) the same. On the other hand, a generally employed window function has larger amplitude at a position closer to a center. Accordingly, in trying to derive the wavefront information of the X-ray (light) entering (x0, y), a more accurate value is calculated when the detection result of the first pixel at the time of detecting I5 and the detection result of the first pixel at the time of detecting I6 are positioned closer to a center of the window function of the composite array I. From that point of view, the detection result of the first pixel at the time of detecting I5 and the detection result of the first pixel at the time of detecting I6 are to be positioned close to each other. Because the distance between the detection result of the first pixel at the time of detecting I5 and the detection result of the first pixel at the time of detecting I6 within the composite moiré (i.e., the composite period pattern) is P−α, it is beneficial that P−α is smaller. More specifically, P−α is to be 3 or less. When P−α is 3 or less, the detection result of the first pixel at the time of detecting I5 and the detection result of the first pixel at the time of detecting I6 are positioned within three pixels in the composite moiré I. When P−α is 1, the detection results of the first pixel are adjacent to each other in the composite moiré I. In this specification, the information of the specimen implies information obtained from the wavefront information of the X-ray (light) having transmitted through the specimen, e.g., information regarding absorption, scattering, and phase of the specimen. The wavefront information of the X-ray (light) at each of plural positions is derived by computing the wavefront information of the X-ray per the X-ray entering each pixel. Further, an absorption image, a scattering image, a differential phase image, and a phase image of the specimen are obtained by deriving plural pieces of information of the specimen from the wavefront information for each of plural positions, and mapping the derived information. Example 1 will be described below in connection with a practical example in which a differential phase image in one direction is obtained with a simulation from a moiré having a period in one direction (i.e., a one-dimensional moiré) by using the wavefront measuring apparatus described in the first embodiment. As in the first embodiment, the wavefront measuring apparatus used in EXAMPLE 1 is the wavefront measuring apparatus illustrated in FIG. 1. Details of the wavefront measuring apparatus are described below. In EXAMPLE 1, a focal point of the X-ray source 110 is set to a size of 100 μm, and energy of the X-ray emitted from the X-ray source 110 is set to 17.5 keV. FIG. 4 is a schematic view of the source grating 120 used in EXAMPLE 1. The source grating 120 used in EXAMPLE 1 is a two-dimensional grating in which a transmitting portion 121 and a shielding portion 122 are two-dimensionally arrayed. A grating period is set to 40 μm, and a width of each transmitting portion 121 is set to 5 μm. FIG. 5A is a schematic view of a diffraction grating used in EXAMPLE 1. The diffraction grating used in EXAMPLE 1 is a one-dimensional phase grating 140a having a phase reference portion 141a and a phase shift portion 142a, which are arrayed at a period of 8 μm. The phase grating 140a is constructed such that a phase difference between an X-ray having transmitted through the phase reference portion 141a and an X-ray having transmitted through the phase shift portion 142a is π. That type of grating is called a π-grating. FIG. 6A is a schematic view of a shield grating 150a used in EXAMPLE 1. The shield grating 150a used in EXAMPLE 1 has a shielding portion 151a and a transmitting portion 152a, which are arrayed at a period of 4.58 μm. The shield grating 150a is arranged such that a distance between the phase grating 140a and the shield grating 150a is 1/10 of a distance between the source grating 120 and the phase grating 140a. In the detector 160, pixels each having a size of 8×8 μm2 and detecting the intensity of the X-ray are two-dimensionally arrayed to detect the X-ray from the shield grating 150a. A moiré formed by the phase grating 140a and the shield grating 150a has a period of 32 μm on the detector 160, and four pixels of the detector 160 correspond to one period of the moiré. A specimen is prepared as four fibers each having a diameter of 250 μm and a complex refractive index of 6.70×10−8−i×9.07×10−11. An analytical method executed in EXAMPLE 1 by the computer is described below. For convenience of explanation, a differential phase image of the specimen is obtained from two moirés I1 and I2 that are expressed by the following formulae (16): I 1 ⁡ ( x , y ) = a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos [ 2 ⁢ π ⁢ 1 4 ⁢ x + φ ⁡ ( x , y ) ] ⁢ ⁢ I 2 ⁡ ( x , y ) = a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos [ 2 ⁢ π ⁢ 1 4 ⁢ x + φ ⁡ ( x , y ) + 2 ⁢ π ⁢ 2 4 ] ( 16 ) Given that m and n in the formula (7) are each +1, virtual moirés I3 and I4 are expressed by the following formulae (17) on the basis of the formula (16): I 3 ⁡ ( x , y ) = ⁢ I 1 ⁡ ( x + 1 , y ) = ⁢ a ⁡ ( x + 1 , y ) + b ⁡ ( x + 1 , y ) ⁢ cos ⁡ [ 2 ⁢ π ⁢ 1 4 ⁢ ( x + 1 ) + φ ⁡ ( x + 1 , y ) ] ≈ ⁢ a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos ⁡ [ 2 ⁢ π ⁢ 1 4 ⁢ ( x + 1 ) + φ ⁡ ( x , y ) ] ⁢ ⁢ I 4 ⁡ ( x , y ) = ⁢ I 2 ⁡ ( x + 1 , y ) = ⁢ a ⁡ ( x + 1 , y ) + b ⁡ ( x + 1 , y ) ⁢ cos ⁡ [ 2 ⁢ π ⁢ 1 4 ⁢ ( x + 1 ) + φ ⁡ ( x + 1 , y ) + 2 ⁢ π ⁢ 2 4 ] ≈ ⁢ a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos ⁡ [ 2 ⁢ π ⁢ 1 4 ⁢ ( x + 1 ) + φ ⁡ ( x , y ) + 2 ⁢ π ⁢ 2 4 ] ( 17 ) The differential phase image of the specimen is obtained by substituting the formulae (16) and (17) in the formula (11). FIG. 7A illustrates the differential phase image of the specimen obtained in EXAMPLE 1, and FIG. 7B illustrates a line profile of the differential phase image illustrated in FIG. 7A. COMPARATIVE EXAMPLE 1 will be described below in connection with an example in which a differential phase image of a specimen is obtained by using the phase shifting method. A simulation is performed by using the same specimen as in EXAMPLE 1 on condition that a wavefront measuring apparatus used in COMPARATIVE EXAMPLE 1 is the same as in EXAMPLE 1 except for a computer. An analytical method executed by the computer in COMPARATIVE EXAMPLE 1 is described below. In COMPARATIVE EXAMPLE 1, the differential phase image is obtained from four moirés, which are expressed by the following formulae (18), and the formula (3): I 7 ⁡ ( x , y ) = a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos ⁡ [ 2 ⁢ π ⁢ 1 4 ⁢ x + φ ⁡ ( x , y ) ] ⁢ ⁢ I 8 ⁡ ( x , y ) = a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos ⁡ [ 2 ⁢ π ⁢ 1 4 ⁢ x + φ ⁡ ( x , y ) + 2 ⁢ π ⁢ 1 4 ] ⁢ ⁢ I 9 ⁡ ( x , y ) = a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos ⁡ [ 2 ⁢ π ⁢ 1 4 ⁢ x + φ ⁡ ( x , y ) + 2 ⁢ π ⁢ 2 4 ] ⁢ ⁢ I 10 ⁡ ( x , y ) = a ⁡ ( x , y ) + b ⁡ ( x , y ) ⁢ cos ⁡ [ 2 ⁢ π ⁢ 1 4 ⁢ x + φ ⁡ ( x , y ) + 2 ⁢ π ⁢ 3 4 ] ( 18 ) FIG. 20A illustrates the differential phase image of the specimen obtained in COMPARATIVE EXAMPLE 1, and FIG. 20B illustrates a line profile of the differential phase image illustrated in FIG. 20A. While the information of the specimen is obtained in COMPARATIVE EXAMPLE 1 from four moirés independently for each pixel, the information of the specimen is obtained in EXAMPLE 1 from two moirés by using the detection result of each pixel and another pixel adjacent to the relevant pixel. Thus, while the phase shifting method employs at least three moirés, the information of the specimen is obtained from two moirés in EXAMPLE 1. COMPARATIVE EXAMPLE 2 will be described below in connection with an example in which a differential phase image of a specimen is obtained by using the windowed Fourier transform method. A simulation is performed by using the same specimen as in EXAMPLE 1 on condition that a wavefront measuring apparatus used in COMPARATIVE EXAMPLE 2 is also the same as in EXAMPLE 1 except for a computer. An analytical method executed by the computer in COMPARATIVE EXAMPLE 2 is described below. In COMPARATIVE EXAMPLE 2, I7, which is expressed as one of the formulae (18), and the formulae (5) are used. Further, a Gauss function is used as the window function. Because spectra of a(x, y), c(x, y) and c*(x, y) expressed by the formulae (5) are overlapped with each other in a wavenumber space, those spectra are processed to be separated from one another. FIG. 21A illustrates the differential phase image obtained in COMPARATIVE EXAMPLE 2, and FIG. 21B illustrates a line profile of the differential phase image illustrated in FIG. 21A. Comparing FIGS. 7A and 7B (EXAMPLE 1) and FIGS. 21A and 21B (COMPARATIVE EXAMPLE 2) with FIGS. 20A and 20B (COMPARATIVE EXAMPLE 1), the differential phase image closer to that in COMPARATIVE EXAMPLE 1 is obtained in EXAMPLE 1 than in COMPARATIVE EXAMPLE 2. It is hence considered that the differential phase image of the specimen obtained in EXAMPLE 1 is closer to the exact one than that obtained in COMPARATIVE EXAMPLE 2. EXAMPLE 2 will be described below in connection with a practical example in which a differential phase image in an x-direction and a differential phase image in a y-direction are obtained with a simulation from a moiré (two-dimensional moiré) having periods in two directions, i.e., the x-direction and the y-direction, by using the wavefront measuring apparatus described in the first embodiment. When the differential phase image in the x-direction and the differential phase image in the y-direction are computed from the two-dimensional moiré, computations may also be executed for the two directions in a similar manner to the case of the one-dimensional moiré. Hence duplication descriptions of similar points to those in EXAMPLE 1 are omitted. An X-ray source 110, a source grating 120, and a detector 160, used in EXAMPLE 2, are the same as those used in EXAMPLE 1. FIG. 5B is a schematic view of a diffraction grating used in EXAMPLE 2. The diffraction grating used in EXAMPLE 2 is a two-dimensional phase grating 140b having a phase reference portion 141b and a phase shift portion 142b, which are two-dimensionally arrayed at a period of 8 μm. As in EXAMPLE 1, the phase grating 140b is a π-grating. FIG. 6B is a schematic view of a shield grating 150b used in EXAMPLE 2. The shield grating 150b used in EXAMPLE 2 has a shielding portion 151b and a transmitting portion 152b, which are two-dimensionally arrayed at a period of 4.58 μm. Further, as in EXAMPLE 1, the shield grating 150b is arranged such that a distance between the phase grating 140b and the shield grating 150b is 1/10 of a distance between the source grating 120 and the phase grating 140b. A specimen is a sphere having a diameter of 800 μm and a complex refractive index of 7.77×10−8−i×9.42×10−11. In EXAMPLE 2, the differential phase image in the x-direction is obtained by employing a reference moiré (first photoperiod pattern) and a moiré (second photoperiod pattern) having a phase shifted by π in the x-direction from the reference moiré. Further, the differential phase image in the y-direction is obtained by employing the reference moiré (first photoperiod pattern) and a moiré (third photoperiod pattern) having a phase shifted by π in the y-direction from the reference moiré. In other words, the differential phase images in the x-direction and the y-direction are obtained from three moirés in total. Here, as a matter of course, a phase shift direction (x-direction) of the second photoperiod pattern with respect to the first photoperiod pattern is perpendicular to a phase shift direction (y-direction) of the third photoperiod pattern with respect to the first photoperiod pattern. A manner of computing the differential phase image in each of the x-direction and the y-direction is described in brief below although it is similar to that in EXAMPLE 1. To explain an analytical method used in EXAMPLE 2, a pixel where the X-ray intensity at (x, y) is detected is defined as a first pixel, a pixel where the X-ray intensity at (x−m, y) is detected is defined as a second pixel, and a pixel where the X-ray intensity at (x, y−q) is detected is defined as a third pixel. In EXAMPLE 2, the differential phase image in the x-direction is computed by using detection results of the first pixel and the second pixel at the time of detecting the first photoperiod pattern and detection results of the first pixel and the second pixel at the time of detecting the second photoperiod pattern. Further, the differential phase image in the y-direction is computed by using detection results of the first pixel and the third pixel at the time of detecting the first photoperiod pattern and detection results of the first pixel and the third pixel at the time of detecting the third photoperiod pattern. FIG. 8A illustrates the differential phase image in the x-direction, which is obtained by using the first photoperiod pattern and the second photoperiod pattern. FIG. 8B illustrates the differential phase image in the y-direction, which is obtained by using the first photoperiod pattern and the third photoperiod pattern. Thus, in EXAMPLE 3, the two-dimensional differential phase image is obtained from three moirés. COMPARATIVE EXAMPLE 3 will be described below in connection with an example in which a two-dimensional differential phase image of a specimen is obtained by using the phase shifting method. A simulation is performed by using the same specimen as in EXAMPLE 2 on condition that a wavefront measuring apparatus used in COMPARATIVE EXAMPLE 3 is the same as in EXAMPLE 2 except for a computer. An analytical method executed by the computer in COMPARATIVE EXAMPLE 3 is described below. In COMPARATIVE EXAMPLE 3, the differential phase image in the x-direction is obtained from four moirés, of which phases are shifted in units of 0.5π in the x-direction, by using the formula (3). Similarly, the differential phase image in the y-direction is obtained from four moirés, of which phases are shifted in units of 0.5π in the y-direction, by using the formula (3). Thus, the two-dimensional differential phase image is obtained from seven moirés in total. FIGS. 22A and 22B illustrate the differential phase images in the x-direction and the y-direction, respectively, which are obtained in COMPARATIVE EXAMPLE 3. It is to be noted that five or more moirés are used when the two-dimensional differential phase image is obtained by using the phase shifting method. COMPARATIVE EXAMPLE 4 will be described below in connection with an example in which a two-dimensional differential phase image of a specimen is obtained by using the windowed Fourier transform method. A simulation is also performed by using the same specimen as in EXAMPLE 2 on condition that a wavefront measuring apparatus used in COMPARATIVE EXAMPLE 4 is the same as in EXAMPLE 2 except for a computer. An analytical method executed by the computer in COMPARATIVE EXAMPLE 4 is described below. In COMPARATIVE EXAMPLE 4, the differential phase images in the x-direction and the y-direction are obtained from one moiré by using the formulae (5). Further, a Gauss function is used as the window function. Because spectra of a(x, y), c(x, y) and c*(x, y) are overlapped with each other in a wavenumber space, those spectra are processed to be separated from one another. FIGS. 23A and 23B illustrate the differential phase images in the x-direction and the y-direction, respectively, which are obtained in COMPARATIVE EXAMPLE 4. FIGS. 9A and 9B illustrate line profiles formed by using the differential phase images of the specimen in the x-direction, which are obtained in EXAMPLE 2 and COMPARATIVE EXAMPLES 3 and 4. FIG. 9A illustrates line profiles of a left end of the specimen, and FIG. 9B illustrates line profiles of a right end of the specimen. Among three lines in each of FIGS. 9A and 9B, a solid line represents the line profile of the differential phase image obtained in EXAMPLE 2, a dotted line represents the line profile of the differential phase image obtained in COMPARATIVE EXAMPLE 3, and a one-dot-chain line represents the line profile of the differential phase image obtained in COMPARATIVE EXAMPLE 4. As seen from FIGS. 9A and 9B, the result obtained in EXAMPLE 2 is closer to the result obtained in COMPARATIVE EXAMPLE 3 than in COMPARATIVE EXAMPLE 4. It is hence considered that a more accurate differential phase image is obtained in EXAMPLE 2 than in COMPARATIVE EXAMPLE 4. EXAMPLE 3 will be described below in connection with a practical example in which a one-dimensional differential phase image (i.e., an image resulting from differentiating a phase image in one direction) is obtained with a simulation from a moiré having a period in one direction (i.e., a one-dimensional moiré) by using a wavefront measuring apparatus that executes the analytical method described in the second embodiment. The wavefront measuring apparatus used in EXAMPLE 3 is the same as in EXAMPLE 1 except for a computer, and a specimen used in EXAMPLE 3 is also the same as in EXAMPLE 1. A method of analyzing a moiré by the computer in EXAMPLE 3 is described below. In EXAMPLE 3, a differential phase image of a specimen is obtained from a reference moiré I5 and a moiré I6 having a phase shifted by 0.5π with respect to the reference moiré I5. The following formulae (19) are obtained by substituting a moiré period P=4, which is in units of pixel size of the detector, and α=1 in the formulae (13). I ⁡ ( x , y ) = { I 5 ⁡ ( x , y ) , for ⁢ ⁢ x ≤ x 0 + 1 I 6 ⁡ ( x - 1 , y ) , for ⁢ ⁢ x ≥ x 0 + 2 ( 19 ) The differential phase image is obtained by analyzing the moiré, expressed by the formulae (19), in accordance with the formula (5). FIGS. 10A and 10B illustrate respectively the differential phase image and a line profile of the specimen, which are obtained in EXAMPLE 3. Comparing FIGS. 10A and 10B (EXAMPLE 3) and FIGS. 21A and 21B (COMPARATIVE EXAMPLE 2) with FIGS. 20A and 20B (COMPARATIVE EXAMPLE 1), the result closer to that in COMPARATIVE EXAMPLE 1 is obtained in EXAMPLE 3 than in COMPARATIVE EXAMPLE 2. It is hence considered that the differential phase image obtained in EXAMPLE 3 is closer to the exact one than that obtained in COMPARATIVE EXAMPLE 2. EXAMPLE 4 will be described below in connection with a practical example in which a differential phase image in the x-direction and a differential phase image in the y-direction are obtained with a simulation from a two-dimensional moiré by using a wavefront measuring apparatus that executes the analytical method described in the second embodiment. The wavefront measuring apparatus used in EXAMPLE 4 is the same as in EXAMPLE 2 except for a computer, and a specimen used in EXAMPLE 4 is also the same as in EXAMPLE 2. A method of analyzing a moiré by the computer in EXAMPLE 4 is described below. In EXAMPLE 4, the differential phase image in the x-direction is obtained from a reference moiré and a moiré having a phase shifted by 0.25π in the x-direction with respect to the reference moiré by using the formulae (13) and (5). Similarly, the differential phase image in the y-direction is obtained from a reference moiré and a moiré having a phase shifted by 0.25π in the y-direction with respect to the reference moiré by using the formulae (13) and (5). Additionally, P=4 and α=1 are set. Thus, in EXAMPLE 4, the differential phase images of the specimen in the x-direction and the y-direction are obtained from three moirés in total. FIG. 11A illustrates the differential phase image in the x-direction obtained in EXAMPLE 4, and FIG. 11B illustrates the differential phase image in the y-direction obtained in EXAMPLE 4. Further, line profiles are formed by using the differential phase images of the specimen in the x-direction, which are obtained in EXAMPLE 4 and COMPARATIVE EXAMPLES 3 and 4. FIG. 12A illustrates line profiles of a left end of the specimen, and FIG. 12B illustrates line profiles of a right end of the specimen. Among three lines in each of FIGS. 12A and 12B, a solid line represents the line profile of the differential phase image obtained in EXAMPLE 4, a dotted line represents the line profile of the differential phase image obtained in COMPARATIVE EXAMPLE 3, and a one-dot-chain line represents the line profile of the differential phase image obtained in COMPARATIVE EXAMPLE 4. As seen from FIGS. 12A and 12B, the result obtained in EXAMPLE 4 is closer to the result obtained in COMPARATIVE EXAMPLE 3 than in COMPARATIVE EXAMPLE 4. It is hence considered that a more accurate differential phase image is obtained in EXAMPLE 4 than in COMPARATIVE EXAMPLE 4. While the foregoing description has been made in connection with the case where the present disclosure is applied to an interferometer carrying out a differential interference method, application fields of the present disclosure are not limited to the interferometer carrying out the differential interference method. The present disclosure may also be applied to not only an interferometer carrying out an interference method (other than the differential one), but also to a wavefront measuring apparatus not utilizing interference. EXAMPLE 5 will be briefly described below by referring to FIG. 13 in connection with the case where the present disclosure is applied to a wavefront measuring apparatus, which is described in PCT Japanese Translation Patent Publication No. 2010-502977, as an example of the wavefront measuring apparatus not utilizing interference. In a wavefront measuring apparatus 1000 of FIG. 13, information regarding a phase of a specimen is obtained by delivering an X-ray to a specimen, detecting and analyzing an amount by which the X-ray is refracted by the specimen, and deriving wavefront information. The wavefront measuring apparatus 1000 illustrated in FIG. 13 includes an X-ray source 1101, a division element 1103 for dividing a divergent X-ray 1102 emitted from the X-ray source 1101 to form plural X-ray beams 1105, and a detector 1106 for detecting the X-ray beams 1105. The wavefront measuring apparatus 1000 further includes a computer 1107 as an arithmetic unit for executing calculations based on a detection result of a periodic pattern by the detector 1106, and an actuator 1108 that serves as a moving unit to move the division element 1103. A specimen 1104 may be positioned between the division element 1103 and the detector 1106, as illustrated in FIG. 13. Alternatively, the specimen 1104 may be positioned between the X-ray source 1101 and the division element 1103. In the wavefront measuring apparatus 1000 illustrated in FIG. 13, a periodic pattern corresponding to a difference of the X-ray intensity is formed on the detector 1106 because the emitted X-ray 1102 is divided by the division element 1103. Further, a phase of the periodic pattern is shifted because the division element 1103 is moved by the actuator 1108. It is, therefore, possible to detect a first periodic pattern by the detector 1106, and then to obtain a second periodic pattern by performing the detection again after moving the division element 1103 with the actuator 1108. A method of deriving wavefront information by using the first periodic pattern and the second periodic pattern is similar to the above-described method of deriving the wavefront information by using the first periodic pattern and the second periodic pattern, which are obtained with the shearing interferometer. Hence description of the method of deriving the wavefront information is omitted. EXAMPLE 6 will be described below in connection with an example of an X-ray computed tomography apparatus (X-ray CT apparatus) in which a tomographic image is obtained from projection images taken of a specimen from all-around directions. The X-ray CT apparatus of EXAMPLE 6 is also one type of wavefront measuring apparatus. In EXAMPLE 6, a tomographic phase image is obtained by using, as a projection phase image, the differential phase image obtained with the wavefront measuring method that is executed in the wavefront measuring apparatus of the first embodiment. FIG. 15 illustrates a wavefront measuring apparatus 101 of EXAMPLE 6. The wavefront measuring apparatus 101 includes, as a light source, an X-ray source 1110 emitting a parallel X-ray (parallel light), but it does not include a source grating. The wavefront measuring apparatus 101 further includes a table 1210 on which a specimen 1130 is placed, and an actuator 1220 for moving the table 1210. Moreover, the wavefront measuring apparatus 101 differs from the wavefront measuring apparatus 1, illustrated in FIG. 1, in that information of a tomographic image is derived by a computer 1170, which executes calculations based on detection results by a detector 160. On the other hand, the wavefront measuring apparatus 101 is similar to the wavefront measuring apparatus 1, illustrated in FIG. 1, in that an interference pattern is formed by a phase grating 140, that a shield grating 150 is arranged at a position where the interference pattern is formed, thereby forming a moiré, and that the moiré is detected by the detector 160. While the wavefront measuring apparatus 101 is constructed such that the specimen is rotated by a combination of the table 1210 and the actuator 1220 for rotating the table 1210, the wavefront measuring apparatus 101 may be rotated instead of rotating the specimen. Plural projection images are obtained by taking images of a wavefront, which has been modulated in phase by the specimen, at plural projection angles, and a tomographic image of the specimen is obtained from the plural projection images. FIGS. 16A to 16D illustrate the specimen 1130 used in EXAMPLE 6. FIG. 16A is a sectional view of the specimen cut along a yz-plane, and FIG. 16B is a sectional view of the specimen cut along an xz-plane. FIG. 16C is a sectional view of the specimen cut along an xy-plane, and FIG. 16D is a perspective view of the specimen. In EXAMPLE 6, the specimen is rotated through 180 degrees in units of 1.40625 degrees, and images of the specimen are taken from 128 directions. At each projection angle, a reference moiré and a moiré, which has a phase shifted by π in an X-direction (defined as a direction perpendicular to both the rotation axis of the specimen and the projection direction) with respect to the reference moiré, are detected. FIG. 17A illustrates the concept of detecting the moirés at each projection angle. In FIG. 17A, the horizontal axis represents a projection angle, and the vertical axis represents a phase difference in the X-direction with respect to the reference moiré. The moiré is detected at each of positions of the projection angle and the phase difference, which are indicated by black circles (●) in FIG. 17A, while the moiré is not detected at each of positions of the projection angle and the phase difference, which are indicated by white circles (◯) in FIG. 17A. However, the positions of the projection angle and the phase difference at each of which the moiré is to be detected are not limited to those ones illustrated in FIG. 17A. As another example, the moiré may be detected at positions indicated by black circles in FIG. 17C. In other words, when the tomographic phase image is obtained from the differential phase image as in EXAMPLE 6, the phase differences of the detected moirés with respect to the reference moiré may be not the same at all the projection angles because it is just enough that the differential phase image of the specimen is obtained at each projection angle. A projection differential phase image in the X-direction at each projection angle is obtained from the detected moirés in a similar method to that used in obtaining the differential phase image in EXAMPLE 1. More specifically, projection differential phase images in 128 directions are obtained from 256 moirés. Further, the tomographic phase image of the specimen is obtained from the projection differential phase images in those 128 directions. A method of obtaining the tomographic phase image from the projection differential phase images is described below. In EXAMPLE 6, a Filtered Back Projection (FBP) method is used as an image reconstruction method for obtaining the tomographic phase image from the differential phase images. Because the FBP method is widely known as one of image reconstruction methods, outline of the FBP method is described below. It is, however, to be noted that the method of obtaining the tomographic phase image from the differential phase images is not limited to the FBP method and various image reconstruction methods may be optionally used. Generally speaking, the image reconstruction method is a technique of obtaining a distribution of a two- or three-dimensional physical value of an object from projection images taken of the object from all-around directions. In other words, the ordinary image reconstruction method is a technique of obtaining a three-dimensional distribution f(x, y, z) of a physical value of a specimen from a projection ∫f(x, y, z)ds (ds is a line element along the projection direction) of the specimen. While only the image reconstruction method for obtaining a distribution of a physical value in each cross-section (i.e., a plane defined by each projection direction) of an object is discussed in EXAMPLE 6, the present disclosure is not limited to such an application field. The FBP method of obtaining a distribution (also called a tomographic image) f(x, y) of a physical value of an object in each cross-section from projection images is described in more detail. Definition of an x-axis and a y-axis is described with reference to FIG. 14A. As illustrated in FIG. 14A, the x-axis and the y-axis are defined in a plane containing the projection direction that is denoted by an arrow. Although a z-axis is defined perpendicularly to both the x-axis and the y-axis, the z-axis is not illustrated for simplicity. It is to be noted that the definition of the axes in EXAMPLE 6 differs from that in the above-described EXAMPLE 5 and others. As illustrated in FIG. 14A, a coordinate system obtained by rotating an x-y coordinate system by θ is defined as an X-Y coordinate system. FIG. 14B illustrates a frequency space resulting from transforming a space (real space) illustrated in FIG. 14A. A coordinate system of the (spatial) frequency space corresponding to the x-y coordinate system is defined as a μ-ν coordinate system. First, a projection image p(X, θ) is defined by the following formula (20):p(X,θ)=∫−∞∞f(X,Y)dY  (20) Next, a two-dimensional Fourier spectrum F(μ, ν) of f(x, y) is considered. The spectrum F(μ, ν) is expressed by the following formula (21):F(μ,ν)=∫−∞∞∫−∞∞f(x,y)exp[−i(μx+νy)]dxdy  (21) Based on polar coordinate representation (ρ, θ), the formula (21) is rewritten into: F ⁡ ( μ , v ) = ⁢ ∫ - ∞ ∞ ⁢ ∫ - ∞ ∞ ⁢ f ⁡ ( X , Y ) ⁢ exp ⁡ [ - ⅈρ ⁢ ⁢ X ] ⁢ ⅆ X ⁢ ⅆ Y = ⁢ ∫ - ∞ ∞ ⁢ p ⁡ ( X , θ ) ⁢ exp ⁡ [ - ⅈρ ⁢ ⁢ X ] ⁢ ⅆ X ≡ ⁢ ℱ ( X ) ⁡ [ p ⁡ ( X , θ ) ] ( 22 ) where F(x)[a] denotes Fourier transform of a in the X-direction. Furthermore, the following relationship is employed: ( μ v ) = ρ ⁡ ( cos ⁢ ⁢ θ sin ⁢ ⁢ θ ) ⁢ ⁢ ( X Y ) = ( cos ⁢ ⁢ θ sin ⁢ ⁢ θ - sin ⁢ ⁢ θ cos ⁢ ⁢ θ ) ⁢ ( x y ) ( 23 ) The formula (22) implies that a spectrum obtained with one-dimensional Fourier transform of p(X, θ) in the X-direction is equal to a spectrum of spectrum F(μ, ν) in the O-direction. The formula (22) is known as the projection slice theorem. Accordingly, f(x, y) is obtained by taking two-dimensional inverse Fourier transform of F(μ, ν), as expressed by the following formula (24):f(x,y)=∫−∞∞∫−∞∞F(μ,ν)exp[i(μx+νy)]dμdν  (24) The formula (24) is rewritten to the following formula (25) by using the formula (22):f(x,y)=∫−∞∞∫0π(X)[p(X,θ)]|ρ|exp[iρx]dρdθ  (25) Thus, it is understood from the formula (25) that the tomographic image is obtained from the projection image through the following operations: (i) Take Fourier transform of each projection image p(X, θ). (ii) Multiply a frequency filter |ρ| by the obtained spectrum F(x)[p(X, θ)]. (iii) Execute back projection by taking inverse Fourier transform of the filtered spectrum. Further, the following formula (26) is obtained from the formula (25). f ⁡ ( x , y ) = ∫ - ∞ ∞ ⁢ ∫ 0 π ⁢ ℱ ( X ) [ ∂ p ⁡ ( X , θ ) ∂ X ] ⁢ ( - ⅈ ⁢  ρ  ρ ) ⁢ exp ⁡ [ ⅈρ ⁢ ⁢ X ] ⁢ ⅆ ρ ⁢ ⅆ θ ( 26 ) Given that a result obtained by differentiating p(X, θ) with respect to X is called a projection differential image, it is understood from the formula (26) that the tomographic image is obtained from the projection differential image through the following operations. (i) Take Fourier transform of each projection differential image ∂p(X, θ)/∂x. (ii) Multiply a frequency filter −i|ρ|/ρ by the obtained spectrum F(x)[∂p(X, θ)/∂X]. (iii) Execute back projection by taking inverse Fourier transform of the filtered spectrum. In addition to the image reconstruction methods expressed by the formulae (25) and (26), other methods using frequency filters in different forms are also called the FBP methods and are commonly known. Those FBP methods using frequency filters different from the frequency filters in the formulae (25) and (26) may be further optionally employed in this EXAMPLE. The method of obtaining the tomographic image with the FBP method has been described above. The relationship between a projection differential phase image ∂p(X, θ, z)/∂X, which is obtained from the moiré detectable by the Talbot interferometer, and a tomographic phase image Φ(x, y, z) of the specimen is expressed by the following formula (27) on the basis of the formula (20): ∂ p ⁡ ( X , θ , z ) ∂ X = ∫ - ∞ ∞ ⁢ ∂ Φ ⁡ ( X , Y , z ) ∂ X ⁢ ⅆ Y ( 27 ) Thus, the tomographic phase image Φ(x, y, z) is obtained from the projection differential phase image by using the formula (26). Alternatively, the tomographic phase image Φ(x, y, z) may be obtained from the formula (25) after integrating individual projection differential phase images and obtaining the projection differential phase images. FIG. 17B illustrates the tomographic phase image of the specimen obtained in EXAMPLE 6. As is apparent from the above description, the process of obtaining the projection image with the periodic pattern and the process of obtaining the tomographic image from the projection image are independently of each other. Accordingly, the image reconstruction method of obtaining the tomographic image from the projection image is not limited to the FBP method, and various image reconstruction methods may be optionally used in combination with the present disclosure. Moreover, as described above, an absorption image and a scattering image of the specimen are further obtained with the Talbot interferometer (or the Talbot-Lau interferometer) in addition to the differential phase image. Here, the absorption image and the scattering image thus obtained are called respectively a projection absorption image and a projection scattering image, and tomographic images corresponding to absorption and scattering are called respectively a tomographic absorption image and a tomographic scattering image. The tomographic absorption image and the tomographic scattering image are obtained respectively from the projection absorption image and the projection scattering image by using the formula (25) in a similar manner to that used for obtaining the tomographic phase image from the projection differential phase image. COMPARATIVE EXAMPLE 5 will be described below in connection with an example in which a tomographic phase image is obtained from projection differential phase images of a specimen, which are obtained with the phase shifting method. Also in COMPARATIVE EXAMPLE 5, the specimen is rotated through 180 degrees in units of 1.40625 degrees, and images of the specimen are taken from 128 directions. COMPARATIVE EXAMPLE 5 differs from EXAMPLE 6 in detecting four moirés in total, i.e., a reference moiré and moirés having phases shifted respectively by π/2, π and 3π/2 in the X-direction with respect to the reference moiré, at each projection angle. FIG. 24A illustrates the concept of setting the position where the moiré is detected at each projection angle. The projection differential phase image in the X-direction at each projection angle is obtained from the detected moirés in a similar manner to that used for obtaining the projection differential phase image in COMPARATIVE EXAMPLE 1. More specifically, projection differential phase images in 128 directions are obtained from 512 moirés. The tomographic phase image of the specimen is obtained from the projection differential phase images in 128 directions in accordance with the formula (26). FIG. 24B illustrates the tomographic phase image of the specimen obtained in COMPARATIVE EXAMPLE 5. COMPARATIVE EXAMPLE 6 will be described below in connection with an example in which a tomographic phase image is obtained from projection differential phase images of a specimen, which are obtained with the windowed Fourier method. Also in COMPARATIVE EXAMPLE 6, the specimen is rotated through 180 degrees in units of 1.40625 degrees, and images of the specimen are taken from 128 directions. However, one moiré is detected at each projection angle. FIG. 24C illustrates the concept of setting the position where the moiré is detected. The projection differential phase image in the X-direction at each projection image is obtained from the detected moiré in a similar manner to that used for obtaining the projection differential phase image in COMPARATIVE EXAMPLE 2. More specifically, projection differential phase images in 128 directions are obtained from 128 moirés. The tomographic phase image of the specimen is obtained from the projection differential phase images in 128 directions in accordance with the formula (26). FIG. 24D illustrates the tomographic phase image of the specimen obtained in COMPARATIVE EXAMPLE 6. FIG. 18 illustrate line profiles in respective portions, which are denoted by dots in FIGS. 17B, 24B and 24D, for comparison of spatial resolution among the tomographic phase images obtained in EXAMPLE 6, COMPARATIVE EXAMPLE 5, and COMPARATIVE EXAMPLE 6. In FIG. 18, a dotted line represents the line profile of the tomographic phase image obtained in EXAMPLE 6, and a broken line represents the line profile of the tomographic phase image obtained in COMPARATIVE EXAMPLE 5. A one-dot-chain line represents the line profile of the tomographic phase image obtained in COMPARATIVE EXAMPLE 5, and a solid line represents the line profile of a true tomographic phase image of the specimen. As seen from those line profiles, the tomographic phase image more closely approaching to the true tomographic phase image is obtained in successive order of COMPARATIVE EXAMPLE 6, EXAMPLE 6, and COMPARATIVE EXAMPLE 5. Thus, the spatial resolution is improved in that order. EXAMPLE 7 will be described below in connection with an example in which moirés are detected by a method different from that used in EXAMPLE 6, projection differential phase images are obtained from the those moirés by using the analytical method described in the first embodiment, and a tomographic phase image is obtained from the projection differential phase images. However, the method of obtaining the tomographic phase image from the projection differential phase images is similar to that in EXAMPLE 6. The method of detecting the moirés in EXAMPLE 7 has solved a problem with the above-described method of detecting the moirés in EXAMPLE 6. The method in EXAMPLE 6 has the problem that, because plural moirés are detected at each projection angle, the rotation of the specimen is to be stopped at each of the projection angles. In EXAMPLE 7, one moiré is detected at each projection angle so that the rotation of the specimen is not stopped during a series of operations of taking images of the specimen. Stated another way, the method of detecting the moirés, described in this EXAMPLE, enables images of the specimen to be taken to obtain the tomographic image while the specimen is continuously rotated. FIG. 19A illustrates the position where the moiré is detected at each projection angle in this EXAMPLE. Two types of methods of obtaining the projection differential phase image are described here. The first method of obtaining the projection differential phase image is as follows. FIG. 19A is a conceptual illustration similar to FIG. 17A. The moiré is detected at each of positions of the projection angle and the phase difference, which are indicated by black circles (●) in FIG. 19A, while the moiré is not detected at each of positions of the projection angle and the phase difference, which are indicated by white circles (◯) in FIG. 19A. As illustrated in FIG. 19A, a first moiré serving as a reference is first obtained at a first projection angle θi. Next, a second moiré is obtained at a second projection angle θi+1. A phase of the second moiré is shifted by π in a direction, which is perpendicular to both the rotation axis of the specimen and the projection direction, with respect to the reference moiré. A projection differential phase image at the projection angle θi is obtained from those two moirés by using the analytical method used in the first embodiment. In more detail, a third moiré, which is a virtual moiré, is obtained from the first moiré, and a fourth moiré, which is a virtual moiré, is obtained from the second moiré. A projection differential phase image is obtained at the first projection angle θi from those four moirés in total. Similarly, a projection differential phase image at a third projection angle θi+2 is obtained from moirés that are detected at the third projection angle θi+2 and a fourth projection angle θi+3. Projection differential phase images are not obtained at the second and fourth projection angles θi+1 and θi+3. Thus, the number of the obtained projection differential phase images is a half that of the detected moirés. Alternatively, a projection differential phase image at the second projection angle θi+1 may be obtained from the moirés detected at the first and second projection angles θi and θi+1, and a projection differential phase image at the fourth projection angle θi+3 may be obtained from the moirés detected at the third and fourth projection angles θi+2 and θi+3. While FIG. 19A illustrates the case where the moirés detected at the first projection angle θi and the third projection angle θi+2 have the phase difference of 0, the phase difference is not always to be 0. As another example, the moirés may be detected at the projection angles and the phase differences illustrated in FIG. 19C. The second method of obtaining the projection differential phase image is as follows. In the second method, the projection differential phase images at the second projection angle θi+1 and the fourth projection angle θi+3 are also obtained. The projection angles and the phase differences at which the moirés are detected are the same as those illustrated in FIG. 19A. Further, a manner of obtaining the projection differential phase image at each of the first projection angle θi and the third projection angle θi+2 is also the same as that in the first method. According to the second method, however, a projection differential phase image at the second projection angle θi+1 is obtained from the moirés that are detected at the second projection angle θi+1 and the third projection angle θi+2. Similarly, a projection differential phase image at the fourth projection angle θi+3 is obtained from the moirés that are detected at the fourth projection angle θi+3 and a fifth projection angle θi+4. A manner of obtaining the projection differential phase image at the fifth projection angle θi+4 is the same as that of obtaining the projection differential phase image at each of the first projection angle θi and the third projection angle θi+2 in the first method. In the second method, because the projection differential phase image at the second projection angle θi+1 is obtained, the moiré detected at the second projection angle θi+1 is to be shifted in phase by π with respect to the moiré detected at the third projection angle θi+2. In the second method, the number of the obtained projection differential phase images is equal to that of the detected moirés. The above-described two methods of obtaining the projection differential phase image are each a method of handling moirés detected at different projection angles as if those moirés are detected at the same projection angle. Comparing with the method described in EXAMPLE 6, therefore, distortion or blur of an image may occur, but EXAMPLE 7 is beneficial in that, as described above, the rotation of the apparatus is not stopped during a series of the image taking operations. A simulation is executed to obtain a tomographic phase image from the projection differential phase images each of which has been obtained with the above-described first method. The wavefront measuring apparatus and the specimen both used in this simulation are the same as those used EXAMPLE 6. Further, as in EXAMPLE 6, the specimen is rotated through 180 degrees in units of 1.40625 degrees, and images of the specimen are taken from 128 directions. However, one moiré is detected at each projection angle, and the moiré detected at each projection angle has the phase difference as per described above in this EXAMPLE with reference to FIG. 19A. FIG. 19B illustrates the tomographic phase image obtained from the projection differential phase images in 64 directions, which have been obtained from the moirés taken in the 128 directions, in accordance with the formula (26). COMPARATIVE EXAMPLE 7 will be described below in connection with an example in which projection differential phase images are each obtained from moirés, which are obtained by a method different from that used in COMPARATIVE EXAMPLE 5, by employing the phase shifting method, and a tomographic image is obtained from the projection differential phase images. Two types of methods of obtaining the projection differential phase image are described here. A first method of obtaining the projection differential phase image is as follows. This first method is described in I. Zanette, et al., Applied Physics Letters 98, 094101 (2011). FIG. 25A illustrates a position where a moiré is detected at each projection angle. As in FIG. 17A, FIG. 25A represents that the moiré is detected at each of positions of the projection angle and the phase difference, which are indicated by black circles (●) in FIG. 25A, while the moiré is not detected at each of positions of the projection angle and the phase difference, which are indicated by white circles (◯) in FIG. 25A. In more detail, a first moiré serving as a reference is first obtained at a first projection angle θ1. Next, a second moiré is obtained at a second projection angle θi+1. A phase of the second moiré is shifted by π/2 in a direction, which is perpendicular to the rotation axis of the specimen, with respect to the reference moiré. Next, a third moiré is obtained at a third projection angle θi+2. A phase of the third moiré is shifted by π in the direction, which is perpendicular to the rotation axis of the specimen, with respect to the reference moiré. Moreover, a fourth moiré is obtained at a fourth projection angle θi+3. A phase of the fourth moiré is shifted by 3π/2 in the direction, which is perpendicular to the rotation axis of the specimen, with respect to the reference moiré. A projection differential phase image at the projection angle θi is obtained from those four detected moirés by using the analytical method used in COMPARATIVE EXAMPLE 1. Similarly, a projection differential phase image at a fifth projection angle θi+4 is obtained. While FIG. 25A illustrates the case where the phase difference between the moirés detected at the first projection angle θi and the fifth projection angle θi+4 is 0, the phase difference therebetween is not always to be 0. In this first method, projection differential phase images are not obtained at the second, third and fourth projection angles θi+1, θi+2 and θi+3. Thus, the number of the obtained projection differential phase images is ¼ of the number of the detected moirés. The second method of obtaining the projection differential phase image is as follows. In the second method, the projection differential phase images at the second, third and fourth projection angles θi+1, θi+2 and θi+3 are also obtained. The projection angles and the phase differences at which the moirés are detected are the same as those illustrated in FIG. 25A. Further, a manner of obtaining the projection differential phase image at the first projection angle θi is also the same as that in the first method. In the second method, however, the projection differential phase image at the second projection angle θi+1 is obtained from the moirés that are detected at the projection angles θi+1, θi+2, θi+3 and θi+4. Similarly, projection differential phase images at the projection angles θi+2 and θi+3 are further obtained. For that reason, a phase of the moiré detected at the fifth projection angle θi+4 is beneficially shifted by π/2 from that of the moiré detected at the fourth projection angle θi+3. In the second method, the number of the obtained projection differential phase images is equal to that of the detected moirés. A simulation is executed to obtain a tomographic phase image from the projection differential phase images each of which has been obtained with the above-described first method. The wavefront measuring apparatus and the specimen both used in this simulation are the same as those used EXAMPLE 6. Further, as in EXAMPLE 6, the specimen is rotated through 180 degrees in units of 1.40625 degrees, and images of the specimen are taken from 128 directions. However, one moiré is detected at each projection angle, and the moiré detected at each projection angle has the phase difference as per described above in this COMPARATIVE EXAMPLE. FIG. 25B illustrates the tomographic phase image obtained from the projection differential phase images in 32 directions, which have been obtained from the moirés taken in the 128 directions, in accordance with the formula (26). EXAMPLE 7 and COMPARATIVE EXAMPLE 7 differ from EXAMPLE 6, COMPARATIVE EXAMPLE 5 and COMPARATIVE EXAMPLE 6 in that the projection differential phase image is obtained by handling the moirés, which are obtained at different projection angles, as the moirés obtained at the same projection angle. Therefore, particularly when the interval between the projection angles is relatively wide, there is a possibility that distortion or blur of the image may occur at a point away from the rotation center of the specimen. Comparing EXAMPLE 7 and COMPARATIVE EXAMPLE 7, EXAMPLE 7 is more effective in reducing such a possibility. In COMPARATIVE EXAMPLE 7, the projection differential phase image at one projection angle is obtained from the moirés detected at four projection angles. On the other hand, in EXAMPLE 7, the projection differential phase image at one projection angle is obtained from the moirés detected at two projection angles. Accordingly, even when distortion or blur of the image occurs, an influence of the distortion or the blur is reduced. As described above, the wavefront measuring method according to the first embodiment is also applied to the case of obtaining a tomographic image. While, in EXAMPLES 6 and 7, the projection differential phase image is obtained with the method, which has been described in the first embodiment, based on the phase shifting method, the projection differential phase image may be obtained with the method, which has been described in the second embodiment, based on the windowed Fourier method, and the tomographic phase image may be obtained from that projection differential phase image. Aspects of the present disclosure can also be realized by a computer of a system or apparatus (or devices such as a CPU or MPU) that reads out and executes a program recorded on a memory device to perform the functions of the above-described embodiment(s), and by a method, the steps of which are performed by a computer of a system or apparatus by, for example, reading out and executing a program recorded on a memory device to perform the functions of the above-described embodiment(s). For this purpose, the program is provided to the computer for example via a network or from a recording medium of various types serving as the memory device (e.g., non-transitory computer-readable medium). While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

043893554

claims

1. A method for preparing nuclear fuel pellets comprising the steps of: (a) blending a predetermined quantity of uranium dioxide and organic binder powders; (b) shaping and pressing the blended mixture into pressed pellet compacts; (c) heating and sintering the compacts in a microwave induction furnace in a reducing atmosphere; (d) holding the compacts at the sintering temperature in the reducing atmosphere for a predetermined time; (e) cooling the compacts to approximately room temperature while maintaining the reducing atmosphere; and (f) grinding the compacts to the desired finished pellet product. forcing the compacts through screens to form a granulate; and pressing the granulate into pressed pellet compacts. conveying sintered uranium dioxide pellets, scrap uranium dioxide powder or the combination thereof to a microwave induction furnace; heating the conveyed material in the microwave induction furnace in an oxidizing atmosphere to oxidize the uranium dioxide to U.sub.3 O.sub.8 powder; and transferring the U.sub.3 O.sub.8 powder for blending with uranium dioxide and organic binder powders in a nuclear fuel pellet preparation process. 2. The method according to claim 1 wherein the pressing is sufficient to achieve a theoretical compact density of approximately 50%. 3. The method according to claim 1 wherein the pressing is sufficient to achieve a theoretical compact density of approximately 44%. 4. The method according to claim 1 further including between steps (b) and (c) the steps of: 5. The method according to claim 4 wherein the pressing is sufficient to achieve a theoretical compact density of approximately 50%. 6. The method according to claim 1 wherein the compacts are sintered in said microwave induction furnace at a temperature in the range of about 1600.degree. C. to about 1800.degree. C. 7. The method according to claim 1 wherein said reducing atmosphere comprises a N.sub.2 and H.sub.2 gas mixture. 8. The method according to claim 7 wherein said gas mixture is about 75% H.sub.2 and 25% N.sub.2. 9. The method according to claim 1 wherein said quantity of uranium dioxide and organic binder powders of step (a) is approximately 99.7 to 99.9% and 0.1 to 0.3% by weight respectively. 10. The method according to claim 1 wherein the holding time of step (d) is from approximately 2 to 6 hours. 11. The method according to claim 1 further including the step of adding a predetermined quantity of U.sub.3 O.sub.8 powder for blending with said uranium dioxide and organic binder powders of step (a). 12. The method according to claim 11 wherein the quantity of U.sub.3 O.sub.8 powder is approximately 5% by weight of the blended powder mixture. 13. A method of recycling rejected sintered uranium dioxide pellets and scrap uranium dioxide powder generated during the preparation of nuclear fuel pellets comprising the steps of: 14. The method according to claim 13 wherein heating in the microwave induction furnace is continuous. 15. The method according to claim 13 wherein heating in the microwave induction furnace is intermittent.

042253896

abstract

The core tank of a liquid metal cooled fast breeder reactor of the pool kind has thermal insulation cladding its inner wall surface. The thermal insulation comprises a plurality of spaced layers of stainless steel sheet material each layer comprising rectilinear panels in spaced array in vertical and horizontal rows. Closure members of cruciform shape close the spaces between adjacent panels.

description

This application is a divisional of U.S. Patent Application No. 11/614,753, filed Dec. 21, 2006, which claims the benefit of U.S. Provisional Patent Application No. 60/755,331, filed Dec. 30, 2005, all of which are hereby incorporated by reference herein in their entirety. The inventive subject matter disclosed herein relate generally to systems and processes using two or more channels of light each having different light attributes. In certain aspects, the inventive subject matter relates to the use of a continuous channel of light output and a superimposed pulsed channel in curing a target material. In such curing operations, a laminar flow system and process may be employed to deliver an inerting fluid or a reactive reagent across the surface of the target material to cause desired effects. There are many applications in which light (i.e., any form of electromagnetic radiation) is used for industrial processing. For example, light is used in curing of adhesives, curing and drying of printing ink, curing of coatings, producing sterile reagents, and direct cleavage of biochemical bonds. In such processes, the target object being processed often has regions with distinctive physical and chemical properties. The target object may also be subject to environmental conditions that vary from one region to another, on or within the target object material. Accordingly, some of the material regions being processed may respond independently to different or variable light effects, such as different intensities, wavelength(s), total optical power emitted by the source, source coherence, radiance of the source (power/area×steradian), degree of collimation, and power stability. Unfortunately, known lighting systems have not been adequate at providing variable multi-attribute light effects that are tuned to specific material regions of a substrate. For example, FIG. 1A is a graph showing a light output profile having a continuous power output signal (which corresponds to a radiance, which in turn correlates to an irradiance at the target substrate). Conventional light sources, including all commercial LED sources used for curing, are generally run in a continuous mode, at the light source's highest output. A continuous profile has been used to provide a good depth cure in a substrate. Unfortunately, this continuous profile, if at a power for a good depth cure, does not allow sufficient curing of curable material that may be in contact with an inhibitor. For example, looking at FIG. 3, an irradiated target object 1 is shown. Although the target object 1 may be any irradiated object or substance, the following discussion, unless otherwise indicated, will use a UV curable ink on a printing substrate, such as a film or paper, as the example target object. The UV curable ink is a layer that is disposed over at least a portion of a substrate. The layer may be divided into two zones, Zone A and Zone B. Zone A has a surface on which the inhibitor, e.g., oxygen in air, can act. The inhibitor may also diffuse some depth into the layer to a boundary defining a first side of Zone B, where there is little or no diffusion of inhibitor. A second side of Zone B interfaces with substrate S. Therefore higher power levels are required to overcome the inhibition at the surface of Zone A and within it relative to a Zone B, which is not enriched with inhibitor. The curing operation must provide good curing at the Zone A, and operating in a continuous mode at the higher power to achieve a good cure in Zone A usually results in over-curing in Zone B, damage to the substrate or diminished lifetime of the light source. The problems with existing lighting systems can be illustrated by looking, for example, at the case of curing or drying of acrylate inks in digital graphics. The result of such curing should be a dry and high gloss product. This has been achieved by dissipating a large amount of energy into the polymer ink formulations. Conventional mercury doped lamps and heaters are used as the light source. The print media typically consists of a variety of materials, some of which can be addressed by a higher energy method, while others of which (e.g., plastics like polyvinylchloride, polyethylene, and polypropylene, as well as various heat sensitive substrates) cannot be so addressed. In another example case—DVD bonding—thermal loading of the polycarbonate disks is a particularly vexatious problem that may occur at different levels in the disc where materials, such as adhesive, interface with other materials. In conventional processes, thermal loading may cause deviations in the finished disc, e.g., in the axial, lateral and thickness dimensions. These kinds of deviations may detrimentally affect the read and write characteristics of the disc, reducing overall yield of the production line. The problems will only grow worse as the industry migrates towards lower initiator concentrations, and lower wavelengths (higher energy radiation) used to read and write on the DVDs. Another challenge in DVD manufacturing is uniform curing across zones: one where there is an aerobic environment and the other where there is an anaerobic or less aerobic environment. The edge of a DVD is a particularly aerobic zone and therefore has required special processing parameters relative to the other zones of the disc. FIG. 1B shows an implementation of a set of continuous power output signals where various LED array sources can be combined operating at different power levels or wavelengths shown in FIG. 1B. This continuous approach is restrictive and leads to inefficient energy use, heat loading and undesirable properties in the polymerized zones. In addition the lifetime of the source is decreased. Further, operation of the LEDs at the higher power outputs required for a good cure of some zones in a target object, such as aerobically inhibited surface zones, seriously shortens the life of the LEDs, making them impractical for use. In summary, the continuous modes of operations shown in FIGS. 1A-1B are problematic at processing different zones in a single target object and wasteful of energy, considering that they must operate at outputs dictated by the more demanding zone of a given substrate, or have other drawbacks. LEDs have also been used in a pulsed mode instead of a continuous mode. In a pulsed mode, the light output cycles between zero power output to a peak power output. Pulsing alone is not sufficient to achieve good overall curing of a substrate that has curable regions that independently react to light. For example, FIG. 2 shows a pulsing profile where the peak power may be sufficient to cure at the surface of, and within, Zone A, but does not yield a good cure at depth, with “depth” represented by Zone B in FIG. 3. Adhesion of materials at depth may be an objective of a curing process. Adhesion generally depends on the polymeric properties at the interface of the Zone B curable material and substrate (S) material, and pulsing that may afford curing in for Zone A cannot be controlled or optimized for good adhesion at the interface. Accordingly there has been a need for light systems that afford good curing at a surface zone and a depth zone. Other approaches for overcoming the problem of edge curing include use of shutters and filters to vary the light exposure on a target object. But these systems are complicated, expensive, high-maintenance, and may require complex cooling systems. In this regard, the prior art has attempted to differentially overcome aerobic inhibition by displacing air. For example, in DVD bonding this has been done by flooding the edge region of a disc with an inert gas, namely nitrogen. Unfortunately, flood inerting is inefficient and wasteful. (See UV-Sheetfed Drying Under Oxygen Reduced Conditions, by Joachim Jung, Peter Holl, Radtech 2004 Paper, IST Metz.) In addition to this, dynamic production processes, such as DVD production lines and printing-substrate belt-feed systems, are not amenable to isolation of the target object in a static reservoir of inerting gas. Therefore, these dynamic processes require a system where the gas that is used must be applied and purged from the point of treatment. Consequently, there are associated costs and potential hazards. In view of the foregoing problems, there is a substantial need for improved lighting systems and methods that provide light to different zones of materials in a target object depending on the properties and requirements for each zone. There is also a need for improved systems and methods for introducing fluid flow to a zone of material for inerting the zone or for introducing a reactive reagent and thereby facilitate a desired photoreactive effect at the zone. There is also a need for such systems and methods to be efficient in terms of cost and effectiveness and relatively simple to implement and operate. The present invention overcomes the problems in the current technology by providing lighting systems and methods with multi-attribute light effects. These multi-attribute light effects optionally may be combined with the use of laminar flow fluids to further reduce the energy necessary to achieve the same amount of polymerization products. The flow reagents can be any fluidic compound used to modify the aerobic or exposed volumes of reagents. The light attributes may be provided in distinct channels representing a set of attributes. The channels are provided in one or more light sources using solid state emitters. A preferred lighting source is an array of solid state emitters formed on a substrate. While the following description may focus on specific curing applications, the inventive concepts and other matters described herein may be applicable to any number of applications in the ink, graphic arts, industrial coating, paints, bonding, adhesives application, and various other fields, as persons in the art will appreciate from the teachings herein. Advantageously, the invention can control the reactions in the different zones differently, which is not feasible using conventional sources. By independently controlling light attributes in different regions in the layer of cured material, the properties associated with the various polymers employed in the industrial processes can be adjusted to fit a specific performance. Examples of these are if the adhesion is to be promoted the reactivity at the interface to the substrate would be adjusted to promote bonding to the material of the substrate or if a hard non-flexible surface is desired the increased pulsing can promote cross linking in the top boundary layer while maintaining the adhesion with less cross linking at the substrate. The inventive subject matter also contemplates one or more light sources configured to emit multiple wavelengths on the continuous or pulsed channels. The adjustment of the wavelength intensities allows the light source to attain maximum coupling efficiency into the atomic and molecular absorption bands of the respective zones. This avoids thermal loading, undesired reaction in zones and/or extends the lifetime of emitters, while achieving the desired polymerization for each zone. In one possible embodiment, the inventive subject matter contemplates a method for performing a photo reaction on a target object, comprising: emitting from a light source a continuous output of irradiance onto the target object having a first photo-reactive zone A, and a second photoreactive zone B; superimposing over the continuous light output a pulsed light output of irradiance onto the target object, with the pulsed output having a peak irradiance level greater than that of the continuous light output; and wherein the target object has a first zone A that has a photo-reactive character that is different from a zone B, and the pulsed light output enhances a photo-reaction in zone A relative to the continuous light output. In the method, the light source may include an array of solid state light emitters having a power output/cm2 from about 500 mW/cm2 to about 4 W/cm2. In the method, the wavelength of light from the first and second channels may be within the range of from about 1800 nm to about 150 nm. In the method, the wavelength of light from the first and second channels is within the range of from about 420 nm to about 150 nm. In the method, the continuous emission may have an irradiance within the range of from about 100 mW/cm2 to about 10,000 mW/cm2. In the method, the continuous emission may have an irradiance within the range of from about 100 mW/cm2 to about 1.5 W/cm2. In the method the pulsed emission may have a peak irradiance within a range of from about 5 W/cm2 to about 5000 W/cm2. In the method, the pulsed emission may have a peak irradiance within a range of from about 1 W/cm2 to about 30 W/cm2 and the ratio for the peak of the pulse to the base of the pulse is at least about 0.02 to about 100. In the method, the duty cycle for the pulsed emission may be from about 1%-50% at about 0.02 Hz to about 40,000 Hz. In the method, the duty cycle for the pulsed emission may be from about 1%-25% at 0.02 Hz to about 40,000 Hz. In the method, the duty cycle for the pulsed emission may be from about 1%-10% at about 0.02 Hz to about 40,000 Hz. In the method, during light output a laminar flow may be introduced across a surface area of the material exposed to the light. In the method, an inerting agent may be introduced via the laminar flow. In another possible embodiment, the inventive subject matter contemplates a system for performing curing of target object, comprising: a light source comprising an array of solid state light devices configured for providing onto the target object a (i) first channel of light output comprising a substantially continuous pulse of light emission, and (ii) a second channel of light output comprising a pulsed light emission, both channels being within a wavelength range sufficient to caused desired curing in the target object, and wherein the second channel pulsed emission of light at a peak irradiance is in the range of about 2 to about 100 times greater than that of the irradiance of the continuous emission. The system may be enabled to perform any of the methods contemplated above and below. In another possible embodiment, the inventive subject matter contemplates a method comprising: providing a flow of a fluid over at least one surface zone of a target object; exposing the target object to a light that fosters a reaction in association with the at least one surface zone of the target object; and wherein the light comprises light from a solid state light source, the light source outputting to the target object a light profile comprising a continuous mode of output and a super-imposed pulsed mode. In another possible embodiment, the inventive subject matter contemplates a product comprising a photo-reacted target object, the target object being formed by a method comprising: emitting from a light source a continuous level of irradiance onto the target object having a first photo-reactive zone A, and a second photoreactive zone B; superimposing over the continuous light output a pulsed light output having a peak irradiance level greater than that of the irradiance level of the continuous light output; wherein the target object has a first zone A that has a photo-reactive character that is different from a zone B, and the pulsed light output enhances a photo-reaction in zone A relative to the continuous light output. In another possible embodiment, the inventive subject matter contemplates A product comprising a photo-reacted target object, the target object being formed by a method comprising: providing a laminar flow of a fluid over at least one surface zone of a target object; exposing the target object to a light that fosters a reaction in association with at least one surface zone of the target object; and wherein the light comprises light from a solid state light source, the light source outputting to the target object a light profile comprising a continuous mode of output and a super-imposed pulsed mode. In the foregoing methods, systems and products, the target object may be a CD or DVD.23; the light output may be provided by groups of emitters comprising a first group of one or more emitters dedicated to the continuous output and a second group of emitters dedicated to providing the pulsed output; the output may be provided by a group of emitters dedicated to providing both the continuous and pulsed outputs; the output may be provided by groups of emitters comprising a first group of one or more emitters dedicated to the continuous output and a second group of emitters dedicated to providing the pulsed output; the light output may be provided by a group of emitters dedicated to providing both the continuous and pulsed outputs; the continuous and pulsed output profiles, respectively, may be selected so as to couple into respective absorption bands for predetermined Zone A and Zone B photo-reactants; the polymerization reagents in the target object may comprise a photo-initiator compound and a monomer or oligomer reactive with the compound; and/or the polymers may be selected from the group consisting of epoxies, acrylates, polyimides, and polyamides. The methods may be applications for curing inks; automotive coatings; industrial coatings; cement or concrete coatings; adhesives; tape release polymers in semiconductor processes; paints; and/or lithography. The methods may be applications for cleaning or sterilizing the target object. These and other embodiments are described in more detail in the following detailed descriptions and the figures. The foregoing is not intended to be an exhaustive list of embodiments and features of the present inventive concept. Persons skilled in the art are capable of appreciating other embodiments and features from the following detailed description in conjunction with the drawings “Target object” means any material(s) or substance(s), in any singular, composite, or structural form, that is intended to be exposed to a light (any form of electromagnetic radiation) from a light source to effect a photoreaction. A target object may be an area on another object. For example, the target object may be an area consisting of application of a curable printing ink on a moving sheet of printing substrate. As used herein “zone” means any surface, region, section or portion of a target object. A target object may be defined in terms of a plurality of zones, each representing independent chemical or physical properties, environmental conditions (e.g., surrounding media, reactants, reagents, temperatures, flow conditions, etc.), and/or photo-processing requirements. Accordingly, each zone may have a corresponding channel of light, emitted by one or more light sources, having one or more specific attributes, such as wavelength, pulse time, intensity, etc. One exemplary embodiment of the inventive subject matter provides one or more light sources capable of emitting one or more channels of continuous radiation and one or more channels of pulsed radiation. The light sources may be the same emitter, or separate emitters that can be combined with multiple wavelengths which can be addressed individually or in arrays. The sources can then be coupled into the respective absorption bands of the materials for maximum efficiency. Each channel may be a single frequency having a selected intensity. Alternatively, either channel may have a plurality of selected frequencies and/or have one or more frequencies that vary with time. As well, a channel's intensity may vary with time (and, if the channel has plural frequencies, the intensity may vary among such frequencies and/or one or more of such frequencies may vary over time). Each channel may also have different wave forms. Each channel may also have other different or varying attributes (e.g., source coherence, radiance of the source (power/area×steradian), degree of collimation, power stability, etc.). It is understood that how a particular light source will be configured or controlled will vary from application to application, and persons skilled in the art will appreciate how to adapt a light source for a particular application based on the teachings herein. Solid lighting arrays suitable for use in various embodiments described herein are commercially available products from Phoseon Technology, Inc. of Hillsboro, Oreg. (www.phoseon.com). Models include the RX line of products, such as the RX Starfire™, RX20™, RX 10™, and the RX Firefly™. For example, The RX Starfire™ system is designed as a high intensity UV light “bar” with configurable emitting lengths of 75 mm, 150 mm, 225 mm and 300 mm with an emitting width of 20 mm. FIG. 11 generally shows the RX Starfire light source. The RX Starfire can be either air cooled or water cooled. The RX Starfire is particularly suitable for applications in the inkjet market and can be easily integrated into production systems. The foregoing products use solid state lighting arrays, as taught in PCT Patent Application PCT/US03/14625, filed May 8, 2003, entitled “High Efficiency Solid-State Light Source and Methods of Use and Manufacture,” which is hereby incorporated by reference in its entirety for all its teachings. Suitable light sources are discussed in more detail below. In certain embodiments, the one or more channels of continuous radiation serve as a base power output for the one or more channels of pulsed radiation. In other words, a pulsed channel is superimposed over a continuous channel. (The superimposition may also be referred to as “super-pulsing”.) The superimposition may be achieved by using one or more light emitters that are dedicated to providing the continuous light output and one or more light emitters that are dedicated to providing a pulsed light at an output above a base of the continuous light output. An example output profile for this arrangement is shown in FIG. 4 (discussed in more detail below). Another possibility is to use the same emitters that provide the base power output and pulse them at an output level above a base power level in the continuous mode. In other words, a set of emitters is dedicated to providing both the continuous and pulsed modes of output in a power profile. An example of this is shown in FIG. 5. As can be seen, the net effect of either approach is the same, and the term “superimpose” and variations of this term are meant to cover either approach. It is also noted that the continuous and pulsed power profiles discussed herein are in the context of application to a particular target object, and not necessarily what a light source outputs in between treatments of a target object. It is noted, that while the power output profiles for FIG. 6-7 are shown as separate lines, P and C they could also be represented as a modulated line from a single set of emitters dedicated to continuous and pulsing modes, similar to FIG. 5, or there can be a combination of the approaches of FIGS. 4 and 5 to generate a single overall profile (not shown). As used herein “continuous” means a base power output over which a pulse of relatively higher power is superimposed. Typically, the continuous mode will be a uniform power output over time and the duty cycle of the pulsing will be a fraction of the continuous power mode. However, it is also within the scope of the inventive subject matter for the continuous mode to be a non-uniform base relative to the pulsing. For example, the base pulse could vary over time and still serve as a base relative to the superimposed pulses. The base pulse might have a slope over time (FIG. 6) or be modulated (FIG. 7), or some combination thereof. It will be appreciated that such profiles can serve as a base for superimposing relatively higher output pulsing. Accordingly, the term “continuous” is intended to cover any form of base pulse over which a relatively high power pulse with a relatively short duty cycle is superimposed. The duty cycles may be run at from about at 0.02 Hz to about 40,000 Hz. In certain embodiments, each channel is provided by addressing selected solid state emitters in an array of emitters, or by having separate arrays or single light emitters dedicated to a particular channel. Light sources that emit in a wavelength range of between about 250 nm and 450 nm are specifically contemplated for use in certain curing processes. FIGS. 4-7 show various possible examples of a light output profile according to the inventive subject matter. The profiles show a continuous mode of power output with a superimposed pulse mode of power output. Each pulse is part of a “duty cycle”. A duty cycle is the percent of a period emission that the high intensity pulse is on relative to the base of the continuous power output (Pulse width/period (t/T)). FIG. 5 shows t/T for a single duty cycle. FIG. 5 also illustrates that the pulsing profile may take many forms. For example, as indicated by the first two duty cycles (starting at left), it could have uniformity in terms of spacing of duty cycles and wave form. The third duty cycle shows one possible variation where a pulse in a profile has a different peak power and/or a different pulse width. The fifth duty cycle shows a pulse that has a rounded peak and greater width. It also comes sooner at a higher frequency than earlier pulses. The sixth pulse shows another variation. The seventh pulse shows a stacked-pulse where a pulsing profile of three pulses is superimposed over the top of a flat pulse. The eighth pulse represents a pulse formed from a group of tightly clustered of sub-pulses. Looking at the example target object 1 of FIG. 3, to achieve a full cure in both Zone A and Zone B, using the profiles shown in FIGS. 1A and 1B and/or FIG. 2, the irradiance must be high enough to overcome any inhibition in Zone A. In certain curing operations such as ink curing, the irradiance required to achieve a good cure in Zone A leads to a total energy requirement that is 50 to 60 times the energy required to cure the respective volume or mass of the curable material on the substrate. In contrast, the modes (continuous/pulse channels) shown in FIGS. 4-7 are used to reduce the energy required to achieve the desired cure level (degree of polymerization, chain length distribution) in Zone A and Zone B by addressing them separately. In addition to curing and other photo-reactions, the inventive subject matter may also be used to inspect, clean, or sterilize a target object. For example, IR bands of light are used in inspection of semiconductor materials. UV bands are used to clean and sterilize surfaces in a of a wide variety of applications, including semi-conductor manufacturing, food processing, and hospital settings, etc. The continuous or base line C may be used to provide good curing of a bulk layer in a target object, such as Zone B in FIG. 3, and the pulsed wave form P may be used provide a higher peak irradiance (power/area) relative to line C for good curing for boundary Zone A. In addition, the line C power mode provides excellent adhesion to the substrate S. Although the wave form P is shown as a square wave, it may be provided in any combination of irradiance levels, duty cycles, and/or periods. The desired peak irradiance level (duty cycle/period) is adjusted to overcome inhibition without effecting bulk cure. This may be done because there is a finite amount of inhibitor in the boundary layer Zone A, which needs to be reacted before the desired curing of the material can take place. It is understood that various parameters of the cured polymers can be continuously adjusted by the peak irradiance, duty cycle, and period superimposed on the continuous irradiance. The duty cycles for a curing application can be as high as 95%. The best results are typically obtained when the duty cycle is between about 1% to about 10% for all curable materials, for example. polymerization reagents in polymer, copolymer and alternating copolymer formulations. These include but are not limited epoxies, acrylates, polyimides, polyamides. Both cationic and free radical polymerization reactions benefit from the methods. The curable materials are used in various applications, including include inks (e.g., ink jet, offset, flexographic, screenprint, ceramic, transferable media), automotive and industrial coatings, cement and concrete coatings, and adhesives, tape release polymers in semiconductor processes, paints (e.g., automotive, house, concrete, and marine), lithographic applications (e.g., resists, dielectrics, micro imprint, and nano imprint) In FIG. 4, the pulsed and continuous modes, irradiance may be generated by a single emitter or a single array, with the drive power being distributed uniformly across the emitters in the array, for example. Alternatively, FIG. 5 illustrates, from the third duty cycle on, how the pulsed irradiance output may be varied in any combination of irradiance levels, duty cycles, and/or periods. Accordingly, from the foregoing teachings, it can be seen that the properties of both Zone A and Zone B can be adjusted independently by using separate channels, each with distinct light attributes, for example, different intensities for C or P and modulating the duty cycle, on-time/off-time within a period of the pulsed source or array (P). The proper combination of the pulsed and continuous sources allows the reduction in the energy required to achieve a desired effect. In addition to facilitating uniform polymerization in different zones, the adjustment of the pulsed and continuous components of the irradiance may also facilitates control over a differential polymerization in different zones. This allows the user to effectively achieve different performance of the final polymer related to cross linking, chain length and chain length distribution. By exposing the bulk of a curable material to a low-power continuous dose of electromagnetic radiation while simultaneously curing the layer in contact with the inhibitor (or otherwise benefiting from a higher dose of light energy) with a high-intensity, low duty-cycle pulse from the light source, the inventive subject matter also overcomes the problem of wasted energy that is intrinsic to the prior art. The inventive concepts are particularly suitable for use in bonding functional and decorative layers of optical storage media such as CDs and DVDs. The key aspect of the construction of these optical media is they are bonded together with adhesives. This will likely remain the same although the actual components used to form layers will change as the industry moves to other standards like Blue Ray and HD-DVD (High Density Digital Versatile/Video Discs). In an exemplary embodiment for UV curing of an optical storage media, the inventive concept is directed to an array of LEDs (see description of solid state light emitters below) that are run at a constant nominal current of 0.54 Amps with an irradiance of 0.5 W/cm2 with a secondary signal attached to this constant DC signal, with a Pulse Rate of 200 Hz and pulse width of 62.5 μs achieving a Peak irradiance of 10.5 W/cm2. FIGS. 8-10 show a light system 10 for exposing a target object 1 positioned below the system. The system includes a light source 12. The light source may use a set of one or more arrays 14a-14f of solid state light emitters 16, such as LEDs, formed on a substrate material. The light source emits light rays 17 onto target object 1. The system includes a power source 18 for powering the emitters. The power source may include an optional feedback mechanism for sensing irradiance at the target object and/or temperature, and regulating power according to set parameters. The system would also include controls 20. Typically controls would include a processor for controlling lights and a user interface, which could be hardware, such as switches, buttons, or screen displays, with associated input means, such as keyboards, mousse, and touch screens. There may also be associated software or firmware for configuring the system to provide light output profiles according to the teachings herein, and appropriate storage for storing executable code and related data from an input device. An optional fixture 22 for creating a predetermined fluid flow 23 is shown associated with light source 12. This fixture is described in more detail below under the discussion of laminar flow, which is a representative form of fluid flow. In accordance with other inventive concepts, the replacement of the existing flood curing systems can be achieved in a DVD bonding application. To address the problems identified in the Background section for DVD bonding, the present inventive concepts contemplate a first channel that is used to cure the anaerobic zone of a disc and a second channel to cure the aerobic zone, on the edge of the disc. In an alternative embodiment, an LED array is used for emitting the light for the first channel to achieve the anaerobic cure, and a laser light source is used for emitting light for the second channel to achieve the higher energy density used for the aerobic portion of the DVD (edge). Laminar Flow System In exemplary embodiments, the inventive subject matter provides systems and methods for a reaction at or below a selected portion of a surface of a target object such that a fluid flow is created to foster the reaction. Suitable systems and methods for such fluid flow are taught in PCT/US2005/047605 (WO 2006/072071), entitled METHODS AND SYSTEMS RELATING TO LIGHT SOURCES FOR USE IN INDUSTRIAL PROCESSES, with an international filing date of Dec. 30, 2005, and is and was under common ownership as the inventive subject matter disclosed herein at the time it was made. The application is hereby incorporated by reference in its entirety for all it teaches. The reaction fostered by the fluid flow may be a photoreaction (e.g., a reaction associated with application of light energy). As used in this application, (a) “fluid flow” means flow of one or more selected fluids, at one or more selected times, over or otherwise in association with at least one selected surface of a target object or substrate, so as to foster a particular reaction; and (b) “foster” means to promote, enable or otherwise contribute to a reaction so that such reaction is properly effected (e.g., the reaction initiates, proceeds and/or is completed without or substantially without inhibition, interference or other detrimental effects, such as those caused by the presence of oxygen or other inhibitor and/or, as the case may be, other impurity, contaminant or material which, if present or present at or above a particular metric, may be at odds with the reaction). In exemplary embodiments, a reaction is fostered by creating fluid flow in association with at least one selected portion of a work object. The fluid flow may be associated with the selected portion by a selected fluid flowing over the selected portion. In exemplary embodiments, the fluid may comprise an inerting fluid. Examples of such inerting fluid include nitrogen or other inert gas or liquid, alone or in combinations. Examples of such inerting fluid also include gases or liquids selected to react with oxygen or other inhibitor or material(s), so as to produce an inert product (e.g., a product that will not inhibit the reaction or otherwise be at odds with fostering the reaction). In exemplary embodiments, the fluid may comprise a reactive species. In such embodiments, the fluid reacts (e.g., photoreacts) with another species in a predetermined manner. Such another species typically is a component of, or is used in making, the work object. Such another species may also be an inhibitor, an impurity, a contaminant or other undesirable material. In exemplary embodiments, the fluid may comprise a catalytic species that catalyzes the reaction (e.g., a photoreaction) in a predetermined manner. In exemplary embodiments, the fluid may comprise combinations of one or more inerting, reactive, catalytic or other species. Any such combination may be provided at once (e.g., in mixtures or other chemical combinations), in sequences (e.g., separately or in mixtures or other combinations), or both. Any such combination may be provided variously over different portions of the target object whether at once, in sequence or both. In exemplary embodiments, the reaction comprises a photoreaction employing a selected light source. The selected light source may be any known light source, for providing light appropriate to the photoreaction. Such light source, generally, addresses various parameters, e.g., particular wavelength(s) and power for a particular photoreaction. In exemplary embodiments, the light source is a solid state light source. Without limiting the generality of the foregoing, the solid state light source may comprise a dense array of light emitting diodes (LEDs). In an exemplary embodiment, fluid flow provides a desired inerting agent or reactive species to at least one selected portion of a surface of a target object to displace, remove or otherwise substantially mitigate or overcome the action of a predetermined agent that inhibits, interferes with, has a detrimental effect on or otherwise is at odds with a photochemical reaction or other predetermined reaction or processing at or in the surface of the target object or substrate. In another exemplary embodiment, the fluid combines with another species to form one of an inerting, reacting or catalytic species. In another exemplary embodiment, the fluid flow can be a unidirectional fluid flow. In still another exemplary embodiment, fluid flow can be a multi-direction fluid flow (e.g., flowing in two directions at the same time, typically at two different locations and/or flowing in one direction at one time and in another direction at another time). In yet another exemplary embodiment can a radial fluid flow. In a further exemplary embodiment, the fluid flow can be without or without substantial turbulence (in such case, the fluid flow may be referred to herein as “laminar flow”). Alternatively, the fluid flow can be with a selected degree of turbulence. In other exemplary embodiments, the fluid its flow direction and nature, and other of its parameters may be selected, so as to provide one or more characteristics. Such selections typically are in the context of application of the fluid flow. As examples of this contextual selection, such selections typically respond to the reaction, the work product's components, the environment (including inhibitors and other materials), and the light source. Such selections are contemplated to include any one or more of the above-described types of fluids, flow directions, flow natures and other parameters, together or separately from other fluid types, flow directions, flow natures and other parameters. Advantages of the inventive subject matter disclosed herein are provided by a device and a method for enabling a reaction (e.g., a photoreaction) at or below a surface of a target object or substrate, in which a fluid flow is provided over or otherwise in association with such surface of the target object, the target object being exposed to a multi-channel light source, as described above, so as to foster the reaction at or below the surface of the target object or substrate. In one exemplary embodiment, the fluid comprises an inerting species, and the reaction is a photoreaction that would be in an aerobic environment, but for the fluid flow. The inerting species could be, for example, nitrogen, carbon dioxide, argon and/or helium. In another exemplary embodiment, the reaction is for a polymerization reaction. In still another exemplary embodiment, the fluid comprises a reactive species. In yet a further exemplary embodiment, the fluid comprises a catalytic species. In one exemplary embodiment, the fluid flow is substantially parallel to a portion of the target object. The reaction (e.g., a photoreaction) could be for curing an ink formation on a substrate. Alternatively, the reaction could be for curing a coating on a target object. As yet another alternative, the reaction could be for setting an ink. In one exemplary embodiment, the target object includes first and second layers of material and a third layer of material between the first and second layers, and the reaction (e.g., photoreaction) enables the third layer of material to bond the first and second layers of material together. For example, the target object could comprise a precursor for optical storage media, such as a CD-type device, a DVD-type device, a Blue Ray DVD-type device or an HD-DVD-type device. In another exemplary embodiment, the light comprises one or more wavelengths of between about 250 nm and 450 nm. In one instance of such embodiment, the light is generated by one or more light sources comprising one or more solid-state light emitters source, the one or more light sources being enabled to provide multiple channels of light. In certain embodiments, one channel is a continuous channel and another channel is a pulsed channel. The inventive subject matter disclosed herein also provides various methods directed to fluid flow. In an example embodiment, a method is provided for applying inert fluid, such as nitrogen, carbon dioxide, or the like, to the edge of a rapidly moving substrate involving UV-cured materials, such as inks, coatings, or adhesives, so that a chemical reaction can be fostered (e.g., without being exposed to, or otherwise mitigating, the detrimental effects caused by the presence of oxygen). In such example method, the inert fluid may provide a layer in association with the edge. Looking now at some particular applications, laminar flow may be used, for example, to generate a small layer at the interface of the fluid flow and a curable material as an economical and effective method to achieve the suppression of oxygen inhibition. This technique is particularly effective when combined with free radical polymerization reactions used in ink jet printing, DVD printing, screen printing, adhesive layer polymerization, coatings for automotive, coatings for structural use, industrial coatings, LCD (Liquid Crystal Display) materials, photoresists in lithography and OLED manufacturing processes. Typically the light sources used in the prior art polymerization reactions are mercury, fluorescent bulbs, halide bulbs, Xenon, lamps, excimer lamps. These lamps all emit UV in bands and therefore are much less efficient in terms of coupling to the material. The use of the SLM (solid state matrix) UV sources allows for the absorption of up to 90-95% of the total energy, whereas the conventional sources only couple as efficiently as 25% to contribute to the polymerization. This is a benefit that is associated with using a smaller bandwidth source like LEDs or SLMs. The combination of the inerting layer allows for the curing of materials at ½ to 1/25 the total energy necessary. This is believed generally possible for by all free radical polymerization reactions. A particular application of light that has significant economic implications in today's industrial application is the polymerization of adhesives and light sensitive polymers, particularly those which are irradiated through low transmittance layers. The absorption of light in a specific wavelength by the material that is to be bonded, sealed, or chemically altered by a polymerization reaction (e.g., a reaction that is catalyzed by the specific wavelength) presents a significant hurdle in a number of industrial applications today. In some chemical reactions, the presence of oxygen tends to have a detrimental effect on the chemical reaction. In this case the use of a laminar flow with low concentrations of oxygen will decrease the amount of energy necessary to overcome the inhibiting effect. The laminar flow can consist of any number of low oxygen concentration flows, such as CO2, nitrogen, argon, helium, and others. It can also be beneficial to use pure reagents in a laminar flow to promote a desired reaction. In one exemplary embodiment, the inventive subject matter provides a directed laminar-flow jet of nitrogen (though carbon dioxide or other inert gases could be use) encased in the mechanical assembly that holds and transports a CD/DVD through its stages of manufacture. A fixture for CD/DVD laminar flow inerting is illustrated and taught in PCT/US2005/047605 (WO 2006/072071), which was incorporated by reference above. It should be understood, though, that the inventive subject matter disclosed herein is not limited to use with nitrogen and that carbon dioxide and other inerting gases and/or fluids could be used. There are many problems that must be overcome when applying an inert atmosphere to the edge of a CD/DVD. First, in order to achieve uniform light exposure over the entire CD for the photoreactive process, the CD/DVD is kept spinning during exposure. The mechanism is a spindle or circular platform that is spun by an electrical motor. A spinning motion, however, results in mixing of the inerting fluid with oxygen. Consequently, a simplistic approach of merely aiming nitrogen jets at the edge of a spinning CD results in sufficient turbulence that excess oxygen is mixed in with the nitrogen and the resulting oxygen concentration is sufficiently large so as to impair curing. Immersing the entire assembly in nitrogen is not practical because the manufacturing volume is too large, and because humans must be able to access the processing area. The target object is located below the multi-attribute light source and the station rotates to position the target object below the light where the radiant energy polymerizes the reagent materials. An example of a system that functions in this manner is a DVD screen print machine. The laminar flow is created between the space of the target object station and the light source while the station is traversing into position under the multi attribute light source. The laminar flow fixture can be mounted on the light source to accommodate either direction of workflow. In a specific application of DVD bonding using an inerting fixture illustrated and taught in PCT/US2005/047605 (WO 2006/072071), the laminar flow of about 0.5 to about 6 l/min is produced by the judicious choice of the nozzle spacing, flow distance and volume in the fixture. A Reynolds Number below 1000 is targeted for the aforementioned flow conditions for gases with a range of temperatures from 25-125 degrees Celsius lower. The density for nitrogen is taken as 0.89 g/l. The physical depth of the fixture limited the length of the flow to 10 mm, which is considered the characteristic distance for calculation of the Reynolds number. The Reynolds number is given by the formula:R=ρVD/μ Where ρ is the density in g/l, V the flow velocity, D is the characteristic distance in m and μ is the viscosity in Poise (Pa s). The flow velocity through the fixture is obtained by computing the volume of the flow area between the inner and outer cylinder of the fixture (subtracting the volume of the inner cylinder from the outer cylinder), computing the residence time in the volume for the aforementioned flows, and dividing the length of the flow distance by the residence time. For a 1 mm flow channel between the inner and outer channel the volume is 0.00102 l, resulting in a residence time of 0.0102 s (0.1 l/s flow) and a flow velocity of 0.98 m/s.R=0.89 g/l(0.98 m/s)0.010 m/0.000018=484 For a 2 mm flow channel between the inner and outer channel the volume is 0.0038 l, resulting in a residence time of 0.038 s (0.1 l/s flow) and a flow velocity of 0.26 m/s.R=0.89 g/l(0.26 m/s)0.010 m/0.000018=128 The choice of a 2 mm distance was taken to allow for a lower Reynolds numbers even at higher flows. The nozzle spacing in the fixture was calculated through a series of flow simulations using finite element analysis to optimize nozzle spacing in relation to fixture dimensions. The fixture configuration was verified by conducting a series of experimental tests using smoke to visualize the flow pattern and then obtaining the same results on the edge of the DVD adhesive as with a purged system. Another exemplary approach of the subject matter herein pertains to the laminar flow curing of inks and related polymeric formulations used in the graphics industry. In a number of offset, flexo, screenprint and stamping applications the reaction rate can be enhanced by creating a laminar flow of reagents at the surface of the ink. FIGS. 3, and 8-10 illustrate a system 10 and systems assemblies and components suitable for use in ink curing with an optional laminar flow of inerting agent 23. An inerting fixture 22 is assembled below light source 12. The fixture has a first side 24 that runs generally adjacent and parallel to an upstream edge of the exposure window or windows of light source 12. The upstream edge is where the target material 1 is first moved into the exposure zone of the light source. In this example, the target material is fed from an upstream roller 50a to another roller 50b on the downstream side of system 10. The material is fed through the system after an ink jet unit (not shown) applies a UV curable ink to material on roller 50a. A second side 26 is on an opposite side of the exposure window(s). A space or opening 32 separates the sides 24 and 26 and provides a channel for light from light source 12 to pass through to target object 1. The separation also defined the area of laminar flow over the target object. The fixture has inlets 34a-b, 36a-b that are fluidically coupled to a source for the inerting agent, such as a reservoir of nitrogen or a nitrogen generation system and respectively to apertures 28 and 30. Controlling the flow from the inlets determines direction, volume, and speed of flow. Optionally, one set of apertures could be coupled to a low pressure source to help pull fluid from opposite apertures at higher pressure. Each side 24 and 26 includes a plurality spaced flow apertures 28 or 30, such as openings in a surface of side 24 or 26 or projecting nozzles from such a surface. The flow apertures 28 on side 24 introduce the inerting agent (or other fluid agent) to the target object positioned below. As illustrated in FIG. 8B, the apertures 28 (or 30) may be configured with an angle to direct the flow of inerting agent non-perpendicularly onto the surface of the target object 1 and towards apertures 30 (or 28), and thereby promote laminar flow. The opposing plurality of apertures 30 in side 26, are at a negative pressure relative to those in side 24, and therefore draw the inerting agent across the target object surface and uptake it. The direction of laminar flow may be alternated by introducing the high pressure fluid from aperture 30 instead of aperture 28. The spacing of the sides, the flow apertures on a given side, inlet and outlet pressures, and other conditions (described herein and in PCT/US2005/047605 (WO 2006/072071), are regulated to create a desired laminar flow across the target object surface. In the case of curing, this allows displacement from the surface of the oxygen in the ambient air, and therefore eliminates or reduces oxygen inhibition. In the typical curing operations, the polymerization of ink is performed on a web passing underneath the fixture in one direction or in a bidirectional mode. In the bidirectional mode the light source is moving across the target object in passes from one side to the other. The flow is redirected to accommodate the direction of the movement of the light source, this creating the laminar flow under the emission area of the source. In one case, the flow apertures 28 on the upstream side of the fixture are used to create the laminar flow between the target object and the light source for one direction, and flow apertures 30 are used for the other direction. The distance between the laminar flow fixture and the target object will define the amount of gas consumption and the flow conditions necessary to preserve laminar flow at the boundary layer (Zone A). In one possible embodiment, the laminar flow fixture is enabled to provide an adjustable length flow. This can be achieved, for example, by creating a plurality of groups of flow apertures wherein one group is individually controllable from another group. By creating lengthwise groups, the width of the flow is adjustable to match the width of the printing material or any other substrate or material under photo-reaction. In the application for the table mounted polymerization the laminar flow conditions resulting in full cure of UV inks on a poster board (target object) are defined by the distance between the light source and the poster board, the length of the light source and the velocity of the light source in respect to the poster board. At a distance of 2 mm, a length of 300 mm and a velocity of 0.25 m/s, the flow rate to fill the scanned volume between the source and the poster board is 9 l/min. In order to achieve the purest reagent layer at the boundary layer Zone A, a Reynolds number below 1000 must be maintained. In the case of nitrogen inerting under standard atmospheric pressure and temperatures from 25 to 125 degrees Celsius the density for nitrogen is taken as 0.89 g/l. The physical distance that is curing the material is 10 mm, this is taken to be the characteristic distance for calculation of the Reynolds number. The flow velocity as calculated above is 0.25 m/s or faster,R=0.89 g/l(0.25 m/s)0.010 m/0.0000166=134 For a 2 mm distance between the light source and the posterboard, the flow need for a velocity of 0.5 m/s is 18 l/min. At 20 l/min flow the resulting flow velocity through the area between the source and posterboard is 0.55 m/s.R=0.89 g/l(0.55 m/s)0.010 m/0.0000166=294 It is clear that the optimum conditions for the laminar flow reagent are dependent on the velocities of the gantry. The optimum concentrations of reagent for the specific control of the reactions in the boundary layer Zone A are more efficiently attained through laminar flow conditions.R=0.89 g/l(2.22 m/s)0.010 m/0.0000166=1190 The fixture configuration was verified by conducting a series of experimental tests using inks to verify the curing speed obtained with the laminar flow. This allows the system to be applied to gantry inkjet systems as well as flexographic/lithographic roll-to-roll processes or presses. The fixture used in the test was similar to that shown in FIGS. 8-10 and described above. It was about 26″ long on each side, about ½″, wide and about 0.43″ thick. Flow apertures are generally spaced along the outer ½″ portion of the width of each side. A manifold for distributing pressure is spaced along the adjacent inner side. The flow apertures have a diameter of about 2 mm and are spaced at about 4 mm center-to-center. There are two staggered two of apertures on each side rows of apertures on each. The row spacing is about 4 mm. In both cases, relative to flood inerting, the laminar flow fixtures allow for lower consumption of reagent gas (nitrogen) by producing the desired laminar flow across the surface of the Zone A. Looking now at FIG. 12, a study was undertaken to assess the minimum amount of energy (dose) required to achieve a “full cure” where a 13 μm thick layer of UV curable ink has good adhesion to a 10 mil styrene (substrate material), and the zone in contact with the inhibitor has achieved good polymerization, which can be observed by inspecting the surface for material transfer. The study compared continuous power output profile with several super-pulsing profiles. Groups of black, yellow, cyan and magenta UV curable inks were separately tested. And the dose for the curing of each group of each is shown in the graph of FIG. 12. All tests were performed at ambient conditions (no inerting). Ambient with “DC only” represents the Starfire RX lighting source run at a continuous (DC) output level of 1 W/cm2. The super-pulsing was based on the indicated duty cycles (square wave form) at the indicated multiple of the rated power for the emitters in the Starfire RX array. The emitted wavelength was from between 380 and 420 nm for all tests. The super-pulsing was superimposed over a base power of 1 W/cm2 (2× nominal) As can be seen, all cases of super-pulsing resulted in lower doses for full cure compared with the performed better than the continuous output for all colors. FIG. 13 shows that a 5% duty cycle at a frequency of 200 Hz with a peak irradiance of 4 W/cm2 reduced the total energy required to achieve a full cure by 30% for the black ink. Looking now at FIG. 13, a study was undertaken to assess the minimum amount of energy (dose) required to achieve a “full cure” where a 13 μm thick layer of UV curable ink has good adhesion to a 10 mil styrene (substrate material), and the zone in contact with the inhibitor has achieved good polymerization, which can be observed by inspecting the surface for material transfer. The study compared (1) continuous power output profile under ambient conditions, (1) super-pulsing profiles under ambient, and (3) super-pulsing under inert conditions. Groups of black, yellow, cyan and magenta UV curable inks were separately tested. And the dose for the curing of each group of each is shown in the graph of FIG. 12. Ambient with “DC only” represents the Starfire RX lighting source run at a continuous (DC) output level of 1 W/cm2. The super-pulsing was based on the indicated duty cycles (square wave form) at the indicated multiple of the rated power for the emitters in the Starfire RX array. The super-pulsing under nitrogen, shown on the far right, was based on hypothetical data. Subsequent actual tests for black ink showed a full cure at even lower power levels (12 mJ/cm2) than indicated in the hypothetical. The emitted wavelength was from between 380 and 420 nm for all tests. The super-pulsing was based on a 5% duty cycle (square wave form) at 13× rated power. The super-pulsing was superimposed over a base power of 1 W/cm2. The inerting was by laminar flow of nitrogen gas over the surface of the inks and substrate. The 5% super-pulsing at 13× rated power, with inerting, performed best of all, and a full cure took only a fraction of the energy used when super-pulsing in ambient conditions, which in FIG. 12 was already shown to be less than that of the continuous profile under ambient conditions. One significant advantage of the inventive subject matter is the ability to run the solid-state emitters higher than their rated output without negatively affecting the manufacturer's rated lifetime or output power. For example, if the emitters were run in a DC operation mode at levels required to achieve a good cure in Zone A and in Zone B, the expected lifetime would be less than about 50 hours. While operating these same emitters at the aforementioned pulsing there have been less than a 10% drop in power output over 1000 hours of operation. If a cooled array of emitters, such as are available from Cree, Inc. of Durham, N.C., and disclosed in PCT Patent Application PCT/US03/14625, incorporated by reference above, or disclosed in U.S. Pat. No. 7,071,493, which is under common ownership with this patent document, are operated at their nominal current rating, an irradiance of 0.3 W/cm2 has been seen. This power level is insufficient to achieve a good cure in Zone A (in contact with the inhibitor) of a typical target object of a curable UV ink on a printing substrate. To achieve a good cure in Zone A, the inventive subject matter contemplates pulsing the emitters to at least 10× their nominal rating achieving a peak irradiance level of 4 W/cm2, and emitter service life remains comparable to the lifetime of the nominal power rating, namely 1000 hrs of service. Exemplary Light Sources Exemplary solid-state light sources which may be used in the foregoing concepts include those set forth in PCT Patent Application PCT/US03/14625, incorporated by reference above. PCT Patent Application PCT/US03/14625 discloses, among other things, high-intensity light sources that are formed by a micro array of semiconductor light sources, such as LEDs, laser diodes, or VCSEL placed densely on a substrate to achieve power density output of at least 50 mW/cm2. The disclosed semiconductor devices are typically attached by a joining process to electrically conductive patterns on the substrate, and driven by a microprocessor-controlled power supply. An optic element may be placed over the micro array to achieve improved directionality, intensity, and/or spectral purity of the output beam. The light module may be used for such processes as, for example, fluorescence, inspection and measurement, photo-polymerization, ionization, sterilization, debris removal, and other photochemical processes. Accordingly, the inventive concepts described herein contemplate a light source that provides channels for a set of attributes for any one or more of these processes. For example, a sterilization of a material could be conducted simultaneously with the curing of the material, which might provide new efficiencies or safety in manufacturing and medical applications. Additionally, light sources that could be used could optionally include features disclosed by PCT Patent Application PCT/US2004/036370, filed Nov. 1, 2004, entitled “Use of Potting Gels for Fabricating Microoptic Arrays,” invented by Duwayne R. Anderson et al., which is hereby incorporated by reference. PCT/US2004/036370 discloses, among other things, a lens array for collecting light from a light source such that the lens array is made of a curable gel that remains pliant after curing. The disclosed lens array may be used alone and without a hard epoxy matrix overcoat. The lens array may be used in a solid-state light emitting device array that includes a glass window that covers the solid-state light emitting device and the lens array so that the lens array cannot be physically interfered with or touched directly. An array of collecting microoptical lenses and/or prisms may be molded into the gel, and the gel lens used as an inexpensive array of lighting devices for the purpose of collecting and condensing the light from the solid-state light emitting device array so that it is less dispersive. Further, light sources that could be used could optionally include features disclosed by PCT Patent Application PCT/US2004/036260, filed Oct. 28, 2004, entitled “Collection Optics For LED Array With Offset Hemispherical or Faceted Surfaces,” invented by Duwayne R. Anderson et al. which is hereby incorporated by reference. PCT Patent Application PCT/US2004/036260 discloses, among other things, an array of LEDs having a lens array for collecting divergent light from each LED. Each lens in the array is associated with a respective LED and has a compound shape including a curved surface that may be spherical or may have an offset aspherical shape. The curved surfaces are centered about each side of its associated LED. The lens may alternatively include faceted surfaces that approximate the curved lens surface. Further still, light sources that could be used could optionally include features disclosed by U.S. Non-provisional patent application Ser. No. 11/083,525, filed Mar. 18, 2005, entitled “Direct Cooling of LEDs,” invented by Mark D. Owen et al. which is hereby incorporated by reference. U.S. Non-provisional patent application Ser. No. 11/083,525 discloses, among other things, a thermal management system for semiconductor devices, such as an LED array, that applies a coolant directly to the LED array. In one exemplary embodiment, the coolant is an optically transparent cooling fluid that flows across the LED array and circulates through a system to remove heat generated by the LED array. Even further, light sources that could be used could optionally include features disclosed by U.S. Non-provisional patent application Ser. No. 11/084,466, filed Mar. 18, 2005, entitled “Micro-reflectors on a Substrate for High-Density LED Array,” invented by Mark D. Owen et al. which is hereby incorporated by reference. U.S. Non-provisional patent application Ser. No. 11/084,466 discloses, among other things, an optical array module that includes a plurality of semiconductor devices mounted on a thermal substrate formed with a plurality of openings that function as micro-reflectors, such that each micro-reflector includes a layer of reflective and conductive material to reflect light and to electrically power its associated semiconductor device. Additionally, light sources that could be used could optionally include features disclosed by U.S. Non-provisional patent application Ser. No. 11/104,954, filed Apr. 12, 2005, entitled “High Density LED Array,” invented by Duwayne R. Anderson et al. which is hereby incorporated by reference. U.S. Non-provisional patent application Ser. No. 11/104,954 discloses, among other things, a dense array of semiconductor devices having an array of micro-reflectors, such that the micro-reflectors have characteristics that enhance dense packing of the array in balance with collection and collimation of the array's radiant output. Also of potential relevance to the inventive concepts hereof is the subject matter of U.S. Provisional Patent Application Ser. No. 60/638,577, filed Dec. 22, 2004, entitled “Light Catalyzed Polymerization for Low Transmittance Materials and Different Chemical Environments,” which is hereby incorporated by reference. All patent and non-patent literature cited above is hereby incorporated by reference as if listed in its entirety for all purposes.

claims

1. A radiographic imaging apparatus comprising:an x-ray source;an x-ray detector;a table for positioning a patient to be imaged;a segmented filtering assembly having a generally annular frame comprising a first pair of opposing openings in a wall of the frame and two opposing x-ray attenuation segments in the wall of the frame; anda controller configured to:position the segmented filtering assembly between the x-ray source and the x-ray detector at a first angular orientation such that x-rays pass through the first pair of opposing openings;monitor detector saturation feedback information from the x-ray detector while the x-ray source irradiates the x-ray detector; andif saturation is imminent and has not yet occurred, rotate the segmented filtering assembly to a second angular orientation such that the two opposing x-ray attenuation segments are positioned to attenuate the x-rays. 2. The apparatus of claim 1 wherein the segmented filtering assembly further comprises a second pair of opposing openings to pass x-rays emitted from the x-ray source through the second pair of opposing openings. 3. The apparatus of claim 2 wherein the controller is configured to position the segmented filtering assembly between the x-ray source and the x-ray detector at a third angular orientation such that x-rays emitted from the x-ray source toward the detector pass through the second pair of opposing openings. 4. The apparatus of claim 1 wherein the controller is configured to translate the segmented filtering assembly in a direction parallel with a rotational axis of the segmented filter assembly. 5. The apparatus of claim 1 wherein the controller is configured to translate the filtering assembly in an x-direction to accommodate one of an asymmetrical subject and a variation in a subject contour. 6. The apparatus of claim 1 wherein the controller is configured to incrementally rotate the segmented filtering assembly in synchronization with data acquisition and in synchronization with a rotational speed of the x-ray source and x-ray detector about the table. 7. A method of manufacturing a CT imaging system comprising:positioning an x-ray source;positioning a detector to receive x-rays emitted from the x-ray source along an x-ray beam path;providing an x-ray filter having a first window and a second window formed in opposite sides of a wall of the x-ray filter, and having a third window and a fourth window formed in opposite sides of the wall of the x-ray filter, the third and fourth windows comprising an x-ray attenuation material;positioning the x-ray filter between the x-ray source and the detector at a first angular orientation such that x-rays emitted along the x-ray beam path pass unimpeded through the first and second windows; andconfiguring an x-ray filter controller to monitor detector saturation feedback from the detector during irradiation of the detector, and if the feedback indicates detector saturation has not occurred but is about to occur, then to rotate the x-ray filter to a second angular orientation, in synchronization with a rotational speed of the detector, to position the third and fourth windows in the x-ray beam path. 8. The method of claim 7 wherein the step of providing further comprises providing the x-ray filter having a pair of oppositely positioned x-ray attenuation materials configured to attenuate x-rays emitted from the x-ray source toward the detector. 9. The method of claim 8 further comprising positioning the x-ray filter between the x-ray source and the detector at a third angular orientation such that x-rays emitted from the x-ray source toward the detector pass through the pair of oppositely positioned x-ray attenuation materials. 10. The method of claim 7 further comprising translating the x-ray filter in an x-direction. 11. The method of claim 7 further comprising translating the x-ray filter to accommodate one of an asymmetrical subject and a variation in a subject contour. 12. A controller configured to:position a rotatable filter between an x-ray source and an x-ray detector such that an x-ray beam passes through two opposing openings thereof;monitor an x-ray detector during irradiation of the x-ray detector and determine whether the x-ray detector is near saturation;if the detector is near saturation but saturation has not yet occurred, incrementally rotate the rotatable filter in synchronization with a rotational speed of the x-ray source and the x-ray detector about a patient to place two opposing attenuation segments of the rotatable filter in a path of the x-ray beam; andtranslate the rotatable filter based on a subject contour. 13. The controller of claim 12 wherein the controller is configured to rotate the rotatable filter in synchronization with data acquisition. 14. The controller of claim 12 wherein the controller is configured to translate the rotatable filter in a direction parallel with a rotational axis of the rotatable filter. 15. The apparatus of claim 1 wherein the controller is configured to rotate the segmented filtering assembly about an axis that is orthogonal to x-rays passing therethrough. 16. The method of claim 7 wherein configuring the x-ray filter controller to rotate the x-ray filter to the second angular position further comprises configuring the controller to rotate the x-ray filter about an axis that is orthogonal to x-rays passing from the x-ray source to the detector. 17. The controller of claim 12 wherein the controller is configured to rotate the rotatable filter about a rotational axis that is coincident with a rotational direction of the x-ray source about the patient. 18. The controller of claim 12 wherein the controller is configured to rotate the rotatable filter about a rotational axis that is orthogonal to the x-ray beam. 19. The apparatus of claim 6 wherein the controller is configured to incrementally rotate the segmented filter assembly in synchronization with a non-zero rotational speed of the x-ray source and x-ray detector about the table. 20. The method of claim 7 wherein positioning the x-ray filter further comprises positioning the x-ray filter between the x-ray source and the detector at the first angular orientation such that a first beam of the x-rays emitted along the x-ray beam path that pass unimpeded through the first window also pass unimpeded through the second window when the x-ray filter is positioned at the first angular orientation. 21. The controller of claim 12 wherein when the controller incrementally rotates the rotatable filter, the controller is configured to rotate the rotatable filter in synchronization with a non-zero rotational speed of the x-ray source and the x-ray detector about the patient.

063295636

summary

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to vitrification of organic ion exchange resins into borosilicate glass, in particular into iron-enriched borosilicate glass, by adding borosilicate glass formers and a ferric oxide producer directly to the resins, forming a homogeneous and durable waste form. The invention results in significant volume reductions of the ion exchange resins. 2. Description of the Related Art The commercial nuclear industry utilizes ion exchange resins to clarify their process and storage waters. The resins, which typically contain one or more backbone polymers and one or more functional groups, are used to remove unwanted impurities, such as radioactive materials or other contaminants, that could potentially harm the equipment or corrode reactor fuel rods. The resins can clarify water which is to be reused at or discharged from the plant, or that is to be stored on site. Often, significant quantities of liquids are treated in this way, creating large volumes of waste solutions. Ion exchange resins are used in several processes to remove both hazardous and radioactive constituents from these solutions or sludges, making disposal of the solutions or sludges easier. In reactor facilities, ion exchange resins are typically used for purification of water in reactor basins and fuel storage basins. Over time, these resins have to be re-generated or replaced because there is an upper limit on the amount of material the resins can remove before they become fully loaded and ineffective. When this happens, the spent resins themselves become hazardous and/or radioactive waste requiring disposal. In many cases, the spent resins present disposal problems both because of the organic matrix itself and the radioactive and sometimes hazardous contaminants adsorbed thereon. Some of the radioactive contaminants that can be present include Cs.sup.37, Sr.sup.90, Co.sup.60, C.sup.14, Mn.sup.54 and Tc.sup.99. In the United States, resin wastes from Boiling Water Reactors (BWR) are enriched in constituents such as Fe.sub.3 O.sub.4, while wastes from Pressurized Water Reactors (PWR) are enriched in borate from moderators and in Li, from pH control compounds. Approximately 100,000 lbs. of BWR and 30,000 lbs. of PWR spent resins are generated per year per commercial reactor in the United States. Resins for removing Cs from Department of Energy (DOE) high level waste (HLW) are being investigated by several DOE sites. A resorcinol resin was originally proposed for use in removing the Cs from HLW supernate. If the use of these resins is implemented, a disposal method suitable for several thousand pounds of spent resin will be needed. Divinylbenzene/styrene copolymer resins are used by reactor facilities, including those at the Savannah River Site (SRS), to purify fuel rod storage basin water. The widespread use of ion exchange resins in the nuclear industry, which shows every sign of continuing into the future, has resulted in a need for a cost-effective method for disposing of spent resins. Disposal methods can be analyzed into two subparts: volume reduction and immobilization. Various methods exist in the art for reducing the volume of these resins and for immobilizing them. U.S. Pat. No. 4,671,898 discloses converting a spent, radioactive ion exchange resin into a stable cement product having reduced volume. U.S. Pat. No. 4,632,778 discloses a procedure for transforming radioactive waste bound to an inorganic ion exchanger, yielding a ceramized product. U.S. Pat. Nos. 4,793,947 and 5,288,435 disclose vitrifications of radioactive waste products requiring pretreatment prior to vitrification. Vitrification has been shown to be a feasible treatment method for ion exchange resins. The organic compounds which make-up the matrix of the resins can be destroyed either by pyrolysis or combustion at typical vitrification temperatures. Some of the heavier organic compounds are pyrolyzed within the melt. The majority of the combustion usually occurs above the melt in the plenum or in a secondary combustion chamber. The goal is to reduce the volume of the total waste, while at the same time providing a durable, immobilizing medium for the radioactive and/or hazardous species. An independent study performed by the Electric Power Research Institute (EPRI) determined that a significant return on investment capabilities was possible by applying vitrification technology to the treatment of spent ion exchange resin. Another important determination was that implementation of the technology would give insurance to reactor operators that operations could continue even if regional compacts for low level waste disposal were delayed. However, vitrification of organic ion exchange resins presents a challenge because of the high organic content of the resins and the volatile Cs.sup.137 that is usually present. High organics tend to induce reducing environments in melters, which can result in the reduction of metals in the waste, and separation of the metals from the bulk glass matrix, defeating at least one of the goals of vitrification. Alloying of the reduced metals with the melter electrodes or corrosion of other melter components can also be a problem, reducing the useful life of the treatment equipment. Organics can also result in reduced glasses, which have been shown to have poorer durability compared to glasses of the same composition that are oxidized or less reduced. X. Feng, I.L. Pegg, E. Saad, S. Cucinell, and A. A. Barkatt, "Redox Effects on the Durability and Viscosity of Nuclear Waste Glasses", Nuclear Waste Management IV, 23. Cs.sup.137 has been shown to be extremely volatile at high temperatures. Stabilization of this contaminant in the glass matrix without excessive volatilization presents a challenge which must be met if the waste is to be successfully stabilized. Past attempts to vitrify ion exchange materials have been only moderately successful from the standpoints of waste loading and volume reduction, and have required additional pretreatment steps. Without pre-treatment, waste loadings and volume reductions have been very limited. A general maximum guideline for waste loading in the glass industry is approximately 20 weight percent. At this waste loading, final wasteform volume usually increases. Using pre-treatment methods (such as wet acid oxidation disclosed in U.S. Ser. No. 08/861,483, filed May 22, 1997 the entire contents of which are hereby incorporated by reference), these processes can result in volume reductions when the resin structure is broken down. The disadvantage of pre-treatment is that extra processing steps and equipment are required. Thus, there are more up-front capital costs and everyday supply costs. These costs are multiplied by the need to use equipment and procedures suitable for handling radioactive material. In addition, the requirement for pre-treatment would extend the treatment time required. Most pre-treatment steps involve some form of chemical oxidation or treatment, which will require control of the radioactive and hazardous materials associated with the resin (e.g. creating a Cs volatility concern). As a result, there exists a need for a method of directly vitrifying organic ion exchange resins in order to reduce the volume of the resin waste and produce a durable and stable waste form. It is one object of the present invention to provide such a process. More specifically, it is an object of the present invention to provide a process for vitrifying an organic ion exchange resin without pretreatment of the resin. It is another object of the invention to provide a process for converting organic ion exchange resins into homogeneous and durable waste forms of iron-enriched borosilicate glass. More specifically, it is an object of the present invention to vitrify these resins directly by adding borosilicate glass formers and a ferric oxide producer to aid in oxidation reactions that remove organic materials during melting. It is another object of the invention to provide a process for converting organic ion exchange resins into homogeneous and durable waste forms of iron-enriched borosilicate glass by adding ferric nitrate as a ferric oxide producer, where the ferric nitrate provides nitrates to help oxidize the organic materials. SUMMARY OF THE INVENTION These and other objectives are achieved by the presently claimed invention, which is directed to a process of vitrifying an organic ion exchange resin by adding borosilicate glass formers and an oxidizer to form a glass forming mixture in order to produce a homogeneous and stable waste form. The glass forming mixture is heated to a temperature and for a time sufficient to form a melt, then cooled to form a vitreous solid. The oxidizer that is added may either be a ferric oxide producer, such as ferric nitrate, or ferric oxide itself, or mixtures thereof and it is added in an amount sufficient to oxidize the resin. The present invention is also directed to a glass composition containing the immobilized waste material, and comprising about 8 wt % to 16 wt % B.sub.2 O.sub.3, about 10 wt % to 15 wt % CaO, about 16 wt % to 22 wt % Fe.sub.2 O.sub.3, about 8 wt % to 14 wt % Na.sub.2 O, about 41 wt % to 49 wt % SiO.sub.2. In another embodiment, the present invention is also directed to a glass composition where Ca(OH).sub.2 is used as the starting material for the CaO glass former, instead of the more common CaCO.sub.3. In this embodiment, a combination of ferric oxide and ferric nitrate is typically used as the ferric oxide producer. The present invention can be more clearly understood by reference to the following Detailed Description of Specific Embodiments, which is not intended to limit the scope of the appended claims.

abstract

A method for preparing to reload a fast nuclear reactor with heavy liquid metal coolant includes extracting a reactor plug and extracting a removable reactor block. The method includes installing handling equipment to form an unloading path under radiation safety conditions. The reactor plug is extracted from the reactor monoblock housing and transported to a plug shaft. The removable reactor block is extracted from the reactor monoblock housing and transported to a block shaft for later disassembly.

052723496

claims

1. An apparatus for insertion and removal of at least one radioactive source into a well or other enclosure comprising: a housing, said housing shielded at least in part; at least one source having a frame supported by said housing during transport and having its radioactive component shielded inside said housing; delivery means on said housing for selectively raising and lowering said source after said source is selectively attached to said delivery means; and said housing formed to allow a shielded path for manipulation of said source by said frame from its position supported by said housing during transport to a second position attached to said delivery means. a belt, said delivery means moving said belt up and down to change the position of said source selectively mounted on said belt. a first segment; a second segment; said frame of said source further comprises: a headed pin insertable freely through said first segment opening and selectively trapped by said second segment opening. a locking member insertable selectively into said large segment opening after said headed pin has been put in said position where it is trapped by said smaller segment opening, thereby selectively preventing disengagement. blocking means on said housing to selectively prevent said source from dropping into the well while it is selectively in a closed position. said blocking means, in said closed position, does not obstruct said path in said housing for transfer of said source between said position during transport and said second position attached to said delivery means. interlock means operable on said delivery means and said blocking means, said interlock means preventing operation of said delivery means which would otherwise result in lowering of said source, said interlock means, when defeated, allowing said delivery means to lower said source while moving said blocking means into an open position away from the downward path of said frame of said source to allow it to be lowered into the well. said belt is formed to accommodate more than one said source with the spacing between sources variable per the needs of the particular application. temporary support means selectively mountable to said belt to support said belt from the well in lieu of from said delivery means to allow removal of said housing from the well; and said temporary support means so mounted to said belt so as to allow a change of its position while continuing to support said belt, thereby allowing selective change of position of said source within the well without use of said delivery means. said temporary support means comprises: a body; a plurality of fasteners selectively aligned with said perforations each said fastener selectively disengageable from said belt allowing said body to pivot on another fastener to selectively raise or lower said belt while said body continues to support said belt in the well. securing means on said housing to selectively hold said source in its transport position, blocking said path, during transport of the housing. blocking means on said housing to selectively prevent said source from dropping into the well until it is selectively activated from a closed to an open position. interlock means operable on said delivery means and said blocking means, said interlock means preventing operation of said delivery means which would otherwise result in lowering of said source, said interlock means, when defeated, allowing said delivery means to lower said source while moving said blocking means into an open position away from the downward path of said source to allow it to be lowered into the well. said belt is formed to accommodate more than one said source with the spacing between sources variable per the needs of the particular application. temporary support means selectively mountable to said belt to support said belt from the well in lieu of from said delivery means to allow removal of said housing from the well; and said temporary support means so mounted to said belt so as to allow a change of its position while continuing to support said belt, thereby allowing selective change of position of said source within the well without use of said delivery means. a housing, said housing shielded at least in part; at least one source supported for transport by said housing, said source having a radioactive component and a frame extending therefrom; a belt, said belt adapted to accept one and more than one of said source for mounting at selectively different points thereon; means connected to said housing for takeup and payout of said belt, and to house said belt without said source connected thereto for transport of said source. said housing is formed to include a shielded path, allowing shielded manipulation of said source from said frame which extends at least in part outside said housing to move said source from its transport position to attachment to said belt. means for selectively preventing dropping said frame of said source completely into said housing until it is secured to said belt. interlock means on said housing acting on said takeup and payout means and said prevention means to prevent payout and to enable said prevention means, in a first position of said interlock means; and to disable said prevention means and allow payout in a second position of said interlock means. temporary support means adapted to engage said belt to support it independently of said takeup and payout means to facilitate disconnection of said belt from said takeup and payout means. said belt is formed having a plurality of perforations; said temporary support means further comprises: a first block engageable with said perforations and capable of shifting positions with respect to said belt while connected to said belt through at least one opening, said first block when attached to said belt supporting said belt to the well to facilitate removal of said housing from the well. a second block mountable to said belt; a pair of guide rollers selectively positioned to guide said belt and to hold said belt when said second block engages said guide rollers, whereupon said housing can be lifted to allow attachment of said first block prior to complete removal of said housing from the well, said rollers retractable into a second position where they do not engage said second block to allow removal of said belt from said takeup and payout means. a weight mounted to said belt to assist said takeup and payout means in paying out said belt until at least one source is attached. 2. The apparatus of claim 1, wherein said delivery means comprises: 3. The apparatus of claim 2, wherein said belt is configured to accept selective placement of at least one of said source at a plurality of locations thereon. 4. The apparatus of claim 3, wherein said belt is perforated with a plurality of openings. 5. The apparatus of claim 4, wherein said openings further comprise: 6. The apparatus of claim 5, wherein said frame of said source further comprises: 7. The apparatus of claim 1, further comprising: 8. The apparatus of claim 7, wherein: 9. The apparatus of claim 8, further comprising: 10. The apparatus of claim 2, wherein: 11. The apparatus of claim 2, further comprising: 12. The apparatus of claim 11, wherein said belt has a plurality of perforations; 13. The apparatus of claim 1, further comprising: 14. The apparatus of claim 4, further comprising: 15. The apparatus of claim 14, further comprising: 16. The apparatus of claim 15, wherein: 17. The apparatus of claim 16, further comprising: 18. An apparatus for insertion of at least one radioactive source into a well, comprising: 19. The apparatus of claim 18, wherein: 20. The apparatus of claim 19, further comprising: 21. The apparatus of claim 20, further comprising: 22. The apparatus of claim 21, further comprising: 23. The apparatus of claim 22, wherein: 24. The apparatus of claim 23, wherein said temporary support means further comprises: 25. The apparatus of claim 24, further comprising:

abstract

Among other things, one or more systems and/or techniques are described for shaping a profile of radiation attenuation in a fan-angle direction via a pre-object filter (e.g., a bowtie filter) based upon a profile of an object. For example, a pre-object filter may be at least partially rotated about a filter axis and/or may be translated in a direction parallel to a direction of conveyance of the object under examination to adjust a profile of radiation attenuation in the fan-angle direction. Further, in one embodiment, the profile of radiation attenuation may be reshaped during rotation of the radiation source about the object to adjust an amount of radiation attenuation in the fan-angle direction (e.g., to adjust a profile of radiation attenuation as a shape of the object changes from a perspective of a radiation source as the radiation source is rotated about the object).

summary

claims

1. Apparatus for use in dentistry for producing real time fluoroscopic images, said apparatus comprising: a housing for emitting x-rays or gamma rays for passage through a dental region of a patient; an image receptor assembly comprising a fluoroscopic image receptor positioned to receive the x-rays or gamma rays after passage thereof through the dental region of the patient to produce a visible light image of said dental region, a fiber optic system connected to said image receptor to transmit the light image, a charge coupled device connected to said fiber optic system to produce a high resolution video signal from said light image; a rotatable C-arm assembly for holding said housing and said image receptor assembly; a control panel for controlling and observing operation of the apparatus; three mechanical arms connecting said housing and said control panel; an intraoral image receptor that can be positioned to receive the x-rays or gamma rays after passage thereof through the dental region of the patient; a plastic holder device for positioning said intraoral image receptor; and a monitor for receiving said video signal to display in real time the dental region of the patient. 2. The apparatus as claimed in claim 1 , wherein said C-arm assembly comprises said housing at one end and said fluoroscopic image receptor at an opposed end; said C-arm assembly comprising a telescopic straight section to vary a distance of said one end of the C-arm assembly relative to said other end; said straight section including a lock for locking said telescopic section once a distance is selected; said one end of said C-arm assembly including a hinge and a hinge lock. claim 1 3. The apparatus as claimed in claim 2 , wherein said housing comprises a window at one end, an emitter positioned next to said window, said emitter including a beam limiter, an x-ray tube including an anode and a cathode, a high voltage power source feeding said x-ray tube through a high voltage connector assembly, an electronic power amplifying system positioned next to said high voltage power source, electronic power amplifying system connected by a low voltage cable to said control panel, and a protective lead plastic cover surrounding said housing. claim 2 4. The apparatus as claimed in claim 3 , wherein said image receptor assembly further comprises a window at one end, said window positioned to allow passage of said x-rays to said fluoroscopic image receptor, an image amplifier assembly which receives the transmitted light image from said fiber optic system, optical lenses interposed between said fiber optic system and said image amplifier assembly, a cable which transmits said video signal from said charge coupled device to a computer monitor and/or television and VCR, and a fiber optic connector which receives an image from said intraoral image receptor. claim 3 5. The apparatus as claimed in claim 4 , wherein said control panel comprises a housing including a microprocessor, said microprocessor connected to an on/off switch, digital controls, a kilovoltage level control, an amperage level control, exposure timing circuits, exposure time alarm control including visual and auditory signals, and a LCD panel, said housing including a pedal cable, a hand control cable, and a power supply emerging therefrom, said pedal cable including an activator pedal for use in fluoroscopic mode, said hand control cable including a hand activator control for use in conventional radiographic mode, said housing including a plastic holder for holding said hand control cable when not in use. claim 4 6. The apparatus as claimed in claim 5 , wherein said control panel housing is connected to a wall by four screws. claim 5 7. The apparatus as claimed in claim 5 , wherein said control panel housing comprises an attachment tube connected to an attachment device, said attachment device connects to a portable table which includes a lead weight for balance and four legs having four wheels for portability of said control panel. claim 5 8. The apparatus as claimed in claim 6 , wherein said activator pedel has two pedal controls, one for activation of said apparatus in fluoroscopic mode, another for activation of recording of a procedure. claim 6 9. The apparatus as claimed in claim 8 , wherein one arm of said three mechanical arms is connected to said control panel, another arm of said three mechanical arms is connected to said housing, wherein said three mechanical arms are connected to each other; said mechanical arms being able to extend, fold and move in various directions. claim 8 10. The apparatus as claimed in claim 9 , wherein said intraoral image receptor comprises a fluorescent screen at one end which receives said x-rays after passage through the dental region of the patient, a fiber optic plate coupling which receives an image from said fluorescent screen, a fiber optic cable which transmits said image to said fiber optic connector of said image receptor assembly, and a lead foil backing positioned at an opposed end, in relation to said fluorescent screen, to reduce radiation exposure to the patient. claim 9 11. The apparatus as claimed in claim 10 , wherein said plastic holder device comprises an intraoral image receptor holder and a clip. claim 10 12. Apparatus for use in dentistry for producing real time fluoroscopic images, said apparatus comprising: a housing for emitting x-rays for passage through a dental region of patient, said housing comprises a window at one end, an emitter positioned next to said window, said emitter including a beam limiter, an x-ray tube including an anode and a cathode, a high voltage power source feeding said x-ray tube through a high voltage connector assembly, an electronic power amplifying system positioned next to said high voltage power source, said electronic power amplifying system connected by a low voltage cable to said control panel, and a protective lead plastic cover surrounding said housing; an image receptor assembly comprising a fluoroscopic image receptor positioned to receive the x-rays or gamma rays after passage thereof through the dental region of the patient to produce a visible light image of said dental region, a window at one end, said window positioned to allow passage of said x-rays to said fluoroscopic image receptor, a fiber optic system connected to said image receptor to transmit the light image to an image amplifier assembly, optical lenses interposed between said fiber optic system and said image amplifier assembly, a charge coupled device connected to said fiber optic system to produce a high resolution video signal from said light image; a cable which transmits said video signal from said charge coupled device to a computer monitor and/or television and VCR, and a fiber optic connector which receives an image from an intraoral image receptor; a rotatable C-arm assembly comprising said housing at one end and said image receptor assembly at an opposed end; said C-arm assembly comprising a telescopic straight section to vary a distance of said one end of the C-arm assembly relative to said other end; said straight section including a lock for locking said telescopic section once a distance is selected; said one end of said C-arm assembly including a hinge and a hinge lock; a control panel comprising a housing including a microprocessor, said microprocessor connected to an on/off switch, digital controls, a kilovoltage level control, an amperage level control, exposure timing circuits, exposure time alarm control including visual and auditory signals, and a LCD panel, said housing including a pedal cable, a hand control cable, and a power supply emerging therefrom, said pedal cable including an activator pedal for use in fluoroscopic mode, said hand control cable including a hand activator control for use in conventional radiographic mode, said housing including a plastic holder for holding said hand control cable when not in use; three mechanical arms connected to each other, one arm of said three mechanical arms is connected to said control panel, another arm of said three mechanical arms is connected to said housing; said mechanical arms being able to extend, fold and move in various directions; said intraoral image receptor comprising a fluorescent screen at one end which receives said x-rays after passage through the dental region of the patient, a fiber optic plate coupling which receives an image from said fluorescent screen, a fiber optic cable which transmits said image to said fiber optic connector of said image receptor assembly, and a lead foil backing positioned at an opposed end of said fluorescent screen to reduce radiation exposure to the patient; and a plastic holder device comprising an intraoral image receptor holder and a clip. 13. A method of producing real time images of a dental region of a patient, said method comprising: (a) selecting a fluoroscopic operating mode on a control panel, (b) emitting x-rays from an emitter for passage through a dental region of a patient; (c) placing an image receptor opposite said emitter to receive the x-rays after passage thereof through the dental region of the patient to produce a visible light image of said dental region, (d) transmitting said visible light image through a fiber optic system from said image receptor to a charge coupled device to produce a high resolution video signal from said image; (e) supporting said emitter and said image receptor on a C-arm assembly which is rotatably connected to a housing; (f) controlling operation from the control panel which is connected to said housing by three mechanical arms which enable the C-arm assembly to be rotatable and also movable in opposite directions along two perpendicular axes so that the emitter and image receptor can be precisely placed at said dental region; (g) positioning said image receptor and said emitter by a plastic holder on said C-arm assembly; and (h) receiving said video signal to display on a monitor, in real time, the dental region of the patient. 14. The method as claimed in claim 13 , comprising operating said emitter at a voltage within a range of 40 to 75 kilovolts and a microamperage between 50 to 300 microamperes. claim 13 15. The method as claimed in claim 13 , comprising: claim 13 placing said emitter and said receptor at the dental region of the patient by moving said C-arm assembly and said housing under the control of said three mechanical arms. 16. The method as claimed in claim 13 , wherein: claim 13 said positioning of the image receptor with respect to the emitter comprises the steps of unlocking a straight telescoping section of the C-arm assembly, adjusting telescoping of said straight section to adjust spacing of said emitter and said receptor and relocking the straight section. 17. The method as claimed in claim 13 , wherein: claim 13 said positioning of the image receptor with respect to the emitter comprises the steps of unlocking a hinge lock on one side of the C-arm assembly, pivoting one end of the C-arm assembly by said plastic holder to adjust the position of the image receptor and relocking said hinge lock. 18. The method as claimed in claim 13 , comprising: claim 13 selecting said fluoroscopic mode by operating a foot control pedal and selectively recording the display on the monitor of the dental region of the patient by operating a second foot control pedal. 19. The method as claimed in claim 13 , comprising forming said C-arm assembly as a plurality of connected straight sections. claim 13 20. The method as claimed in claim 13 , wherein said receptor is formed as a fluoroscopic image receptor to produce said visible image of said dental region or as an intraoral image receptor to produce an X-ray image which is connected by a small fluorescent screen to produce said visible image. claim 13

description

Priority of U.S. Provisional Patent Application, Ser. No. 61/777,286, filed on Mar. 12, 2013 and incorporated herein by reference, is hereby claimed. Not applicable Not applicable 1. Field of the Invention The present invention relates to Radiation Therapy. More particularly, the present invention relates to Intraoperative Radiation Therapy. 2. General Background of the Invention Intraoperative Radiation Therapy (IORT) is the use of radiation to treat cancers during surgery. Two types of treatment exist: X-ray and Electron Beam. While there are numerous effective uses of both treatments, there are few that are considered either economically competitive or medically superior to alternative treatments. With the use of electron beam linear accelerators, teams around the world have proven that Intraoperative Electron Radiation Therapy (IOERT) is equivalent to External Beam Radiation Therapy or Intensity Modulated Radiation Therapy for early breast cancer. Moreover, it is believed to be six times more cost efficient, reducing the cost of treating certain cancers from $30,000 to $5,000 (anticipated Medicare reimbursement rate in 2014). There are two reasons IOERT technology has not been adopted in the United States. First, the US Government does not reimburse the treatment through Medicare, preventing market participants from profiting from ownership. Second, the inability to share machines between hospitals limits the number of market participants to those that have the critical mass of breast cancer cases to provide IOERT services profitably. Even when Medicare does begin reimbursement for IOERT, the number of cases required to provide IOERT services profitably, limits the market to extremely large hospitals since machines cannot easily be shared. Transportation allows hospitals to share the capital cost, allowing for even small hospitals to provide IOERT services profitably. Medicare has not reimbursed the IOERT market for many reasons, but from a practical point of view reimbursement would cause a misallocation of capital since the current class of IOERT machines are unable to be transported between hospitals efficiently. Although they claim to be transportable between hospitals, the machines must be calibrated for at least three energies of the machine to ensure proper function according to some studies. In the end, this amounts to three energies and multiple collimators to create different treatment fields. Prior to use of the machine on a patient one must test at least the energy being delivered for surgery and the ability to change the beam to one energy above and below the prescribed dose. This type of testing is called calibration. Calibration must be done every time the machine is moved between hospitals to ensure it is working in the way intended. One can find boluses for use in radiation therapy at the following website: http://www.dotdecimal.com/products/ect. The following patent references are incorporated herein by reference: U.S. Pat. No. 8,094,779, U.S. Pat. No. 8,073,105, U.S. Pat. No. 5,037,374, U.S. Pat. No. 6,381,304, U.S. Pat. No. 7,834,336, U.S. Pat. No. 8,106,371. It is believed that Precision Accelerators's machines will be three times as fast as the prior art machines in terms of calibration. Every time a prior art machine that varies its energy powers up after transport, it must be tested at three different energies to show that the machine is working. Precision Accelerators's machine can only produce one energy and thus need only be calibrated to this single energy. All else being equal, removing energy variation in the head of the machine and moving it to the end of the collimator tube produces effectively the same treatment beam without having to calibrate the machine ad nauseum. Inter-hospital transportation necessitates extremely quick calibration and quality assurance. The easiest beam to calibrate is a monoenergetic beam that is modified after the beam window because beam modification does not have to be included in linear accelerator quality assurance except as an attachment, which is tested at the same time the machine energy is. This saves a great deal of time because, instead of having to perform 5 tests for three different energies for a total of fifteen (15) tests, there are only five tests for one energy: 200 MU Test, 1000 MU/min test, and three tests of the 10 MeV beam with bolus output to verify beam. The present invention includes two previous ideas put together in a unique way. The invention, although inspired by public ideas, is not obvious. Otherwise, the other manufacturers of machines on the market would simply have redesigned their machines with only one energy and modified the beam using a bolus to allow for transport. They never viewed their energy modification as a problem. Rather, they tout their technical prowess as a feature. The fact that one such competitor attempted to transport IOERT machines between hospitals, but after many attempts conceded that IOERT linear accelerators are not able to be effectively transported, demonstrates that they were unable to figure out a solution to both problems: beam stability and transportability. If the present invention were obvious, this competitor would have implemented it before now. A third-generation of machines, see for example http://www.newrt.com/en/products/novac-11.html, uses collimators in order to create a homogeneous electron beam. These machines have a small, concentrated electron beam unsuitable for medical purposes coming out of the linear accelerator head that is transformed into a homogeneous, distributed beam as it runs through the length of the tube. This happens because of a repelling interaction between electrons within the tube, forcing the electrons to become evenly spread out while they travel through the tube. The Lucite brand poly(methyl methacrylate) tubing the collimator is made of absorbs aberrant electrons with minimal x-ray generation. After passing through a small amount of plastic film around the end of the tube before the breast that is meant to flatten the tissue, the electrons penetrate the potentially cancerous tissue on the surface of the breast, irradiating any remaining cancerous tissue. A separate, but equally useful, invention is the tissue compensator aka a bolus to replace tissue (see, for example, the following website: http://vetmed.illinois.edu/4dvms/documents/imaging/RadTherapy/Overview.pdf). These are employed in radiation therapy to create a more homogeneous energy distribution in uneven tissue by compensating for any missing tissue. This is accomplished by inserting material that is of the same density as human tissue to compensate for the missing tissue. This technology can be employed for any type of radiation as the physics behind it are very simple: every 1 MeV of energy is an extra ½ cm to ⅓ cm of tissue penetration, depending on the exact density of the material chosen. The material chosen will be determined by empirical testing to decide which material gives the best results. The material is typically and preferably tissue isodense poly(methyl methacrylate). However, any hypo- or hyperdense material could be used in the same way, but one would need to take into account the difference in density between the human tissue and the material used. While these two ideas have existed separately on the marketplace for many years, there has been no reason to put the ideas together because there was no application for isodense material before, after, or within a collimator tube for breast IOERT except as a means to increase the dosage to the skin. Even after three generations of machines, companies producing the prior art machines choose to use an electronic system of attenuating beam energy because they apparently believe this is the best way to vary energies in IOERT devices despite its higher cost and increased complexity. They did not choose modification of the electron beam through a compensator though it would produce results. Other manufacturers apparently simply do not see the advantage of this method over electronic variation. An alternative method (an embodiment of the present invention) of attenuating the energy of an electron beam is to place isodense material (an isodense filter) in the path of the beam before it hits the tissue. By placing material in the way of the beam, there is the same effect of reducing the electron beam energy. Every 1 cm of isodense material reduces the depth the beam penetrates the tissue by about 1 cm. This is the same as reducing beam energy by about 3 MeV since the beam is penetrating the same amount of material of the same density. The actual radiation dose is determined by the output of the machine head as measured by dosimeters; however the depth of penetration is determined by the energy of the electron beam or, in the present invention, by the use of bolus not the energy (and thus speed) of the electrons in the beam. The only difference between an electrically-modulated beam with a bolus to remove the skin-sparing dose and a pure bolus system is calibration time. The treatment is otherwise identical. The compensator/bolus thickness for materials of densities other than that of human tissue will vary and are not standardized. By combining these interchangeable compensators/boluses of varying thicknesses with industrial electron linear accelerators, one can create a medical-grade, transportable linear accelerator. The bolus collimator is, in effect, creating transportable, stable, industrial-strength, robust linear accelerators for medical use out of industrial linear accelerators since what really makes an electron beam therapy device a medical device is the ability to vary the dose from patient-to-patient. A very clear advantage of using a bolus as opposed to electronic variation is that the air/tissue interface is effectively moved away from the tissue being treated and is instead present at the air/isodense material interface. In this manner the skin-sparing dose is moved away from the tissue being treated. This allows all of the tissue being treated to receive 100% of the prescribed radiation dose. In the case of external beam compensation, the skin-sparing dose is desirable because there is skin which is highly sensitive to radiation between the beam and the cancerous tissue. Since the skin is treated in external electron beam, it is desirable to minimize the dose the skin receives. However, since IOERT is performed when the skin is not in the way of the beam, there is no need for this skin-sparing dose. Accordingly, there is no negative effect, and arguably a positive effect, associated with having a large compensator in front of an electron beam used in breast IOERT treatment. An advantage of the present compensator based mechanism for changing the depth of penetration of the operative electron beam method is the calibration efficiencies. Originally, calibration efficiencies were not a concern because the stationary machines were in a dedicated, shielded room and did not need to be calibrated daily. Upon invention of intra-hospital mobile devices, the patient-treatment volume did not require the current manufacturers to solve the problem of radiation safety limits from frequent, radiation-intensive calibration, which lowers the maximum number of patients. The best solution to the problem of the inversely correlated nature between patient number and radiation exposure is to minimize unnecessary radiation exposure. In other words, the only way to increase patients is to reduce calibration time, thereby reducing the radiation used in the process. Since patient treatment and machine calibration are both components of the allowable total machine usage in a given day, one can increase the patient volume by decreasing the time required for calibration of the machine Suitable materials for this isodense filter include isodense materials made up primarily or entirely of carbon, oxygen, and hydrogen, such as: poly(methyl methacrylate) (PMMA—a transparent thermoplastic sold under the trademarks Lucite, Plexiglas, and Perspex, for example), Delrin brand acetal resin, UHMW (ultra-high molecular weight polyethylene), polyethylene, polypropylene, ABS, acrylic, Bakelite, CPVC, fiberglass, Kynar brand plastic, Lexan brand plastic, Micarta brand plastic, PVC, Ryton brand plastic, and Teflon brand polytetrafuoroethylene, when the tissue is human breast tissue. Tissue compensators used for electron beam preferably require low atomic number materials so as to minimize the amount of Brehmstrahlung x-rays that are created. While preferably the density of the isodense filter is the same as the tissue which is being radiated, the density could vary, though preferably not more than 2% so as to not dramatically change the tissues treated. While virtually any material can be used as a collimator filter in the present invention, it is preferable that the density is the same as human tissue or roughly that. This makes it easier in two ways. First, if a patient has a breast that needs to be treated to a depth less than the 3.3 centimeters (the 10 Mev electron beam by definition has a 90% isodose line of penetration located at 3.3 cm), a corresponding filter could be used to reduce the amount of penetration by the level that would be required to move the tissue penetration less deeply in the tissue. For example if an oncologist wishes the 90% isodose line to be at 2.3 centimeters in the breast rather than 3.3 cm he can prescribe a 1 cm tissue isodense bolus to bring the 90% isodose line to 2.3 centimeters. There is minimal math needed. Second, there are many isodense materials available for manufacturing, such as poly(methyl methacrylate), which is desirable because it is inexpensive plastic. One can make many boluses cheaply from this material. The bolus is preferably a solid shape which may be attached to a collimator of preferably isodense material. The bolus is preferably a solid cylinder of isodense material, such as plastic, and preferably Lucite. It is preferably attached to a hollow cylinder of Lucite (the collimator tube). Preferably, the bolus and hollow cylinder are integral. Calibration for the 10 meV beam would preferably be done at 100 cm source surface distance. The additional bolus would in the preferred embodiment be added to create a dosimetrically equivalent beam when less penetration is desired. This makes variation of depth penetrance simple and intuitive for the radiation oncologist. To move the 90% isodose line 1 cm less in tissue, one can advantageously use a 1 cm tissue isodense material duplicating the dosimetric characteristics of a 7 MeV electron beam. To duplicate a 6 MeV electron beam one could use a 1.3 cm attenuator. This actually allows for more precise dosimetry than is currently available since the depth of the 90% isodose curve may be moved in smaller increments. Other machines have a computer and electronics which are subject to malfunction, varying the energy of the beam. Precision Accelerators is the only company to only change the characteristics of the beam after it has come out of the head of the IOERT machine. This makes the Precision Accelerators machine extremely stable. In order to provide for a multiple energy linear accelerator using a single energy machine, multiple collimators can be created with boluses 21-27 of many different thicknesses to provide doctors with the most treatment flexibility. Ideally, there will be a series of seven removable collimator tubes 15 with boluses 21-27 (preferably integral with tube 15, but boluses 21-27 could instead be suitably attached in some fashion which would not allow leaking of the beam around the boluses 21-27), along with a tube 15 without a bolus in the event that the full energy of the monoenergy beam is desired for treatment. With seven boluses of 0.333 cm increasing increments, the beam energy (and thus speed of electrons) can be changed from 10 MeV (no bolus) to 9 MeV (0.333 cm material) all the way to 3 MeV (2.333 cm material). Below a beam energy of 3 MeV, the beam does not penetrate even 1 cm of breast tissue, too low energy to be therapeutic in most cases. The bolus 21-27 is preferably a solid cylinder of isodense material, such as plastic, and preferably Lucite. It is preferably attached to a hollow cylinder of Lucite (the collimator tube 15). Preferably, the bolus 21-27 and hollow cylinder 15 are integral. While perhaps the bolus could be placed at any area in the length of the tube, it is preferred to place the bolus 21-27 at the end of the tube 15 closest to the breast, which will provide the patient with the most homogeneous electron beam for treatment as the beam has run the entire length of the typically 100 cm hollow tube 15 before reaching bolus 21-27. In addition the flattening and the symmetry of the beam is at the end of the collimator since there would be some Brehmstrahlung x-rays generated by interaction with the bolus and the calibration would be greatly complicated. FIG. 1 is a perspective view showing a preferred embodiment of the present invention, IOERT apparatus 10. Apparatus 10 includes an IOERT machine 11, which could be a simple, relatively non-expensive mono-energy industrial linear accelerator which produces 10 MeV of radiation. Machine 11 is preferably an industrial, durable, accelerator with technology stable enough for transport from hospital to hospital. A collimator tube 15, preferably made of PMMA (sold as Lucite, for example), is attached to the head 50 of machine 11 using a plastic tube 16 and a connector 19. A plurality of boluses 21, 22, 23, 24, 25, 26, 27, increasing in size from ⅓ cm to 2⅓ cm in ⅓ cm increments, is preferably included (though other sizes could be used to make the increments greater or smaller). These filters 21-27 are preferably made of isodense materials made up primarily or entirely of carbon, oxygen, and hydrogen, such as poly(methyl methacrylate) (PMMA), Deirin brand acetal resin, UHMW (ultra-high molecular weight polyethylene), polyethylene, polypropylene, ABS (Acrylonitrile butadiene styrene), acrylic, Bakelite, CPVC (Chlorinated polyvinyl chloride), fiberglass, Kynar brand plastic, Lexan brand plastic, Micarta brand plastic, PVC (polyvinyl chloride), Ryton brand plastic, and Teflon brand polytetrafluoroethylene, when breast tissue is being treated. Preferably, the boluses 21-27 are integral with tube 15, and the distance from the top 14 of tube 15 to the top of the boluses 21-27 (as shown in FIG. 1) is the same for each tube 15 and bolus (100 cm, for example). Thus, for example, the total length of tube 15 and bolus 21 would be 100⅓ cm, and the total length of tube 15 and bolus 27 would be 102⅓ cm. FIG. 2 shows a detail of the present invention in use when treating the breast 31 of a human patient, with optional cling wrap 17 over the distal end of collimator tube 15 and a bolus 24 which is preferably integral with tube 15 and is present at the distal end of collimator tube 15 to reduce the radiation entering the breast 31 from 10 MeV to 6 MeV. In FIG. 3, apparatus 10 is shown in use to treat a breast 31 of a patient. A bolus 25 is shown integrally attached to tube 15. Optional cling wrap 17 is shown over the distal end of bolus 25. Bolus 25 will reduce the radiation reaching breast 31 from 10 MeV to 5 MeV (as 5 MeV of energy will be dissipated as the electrons flow through bolus 25). Treatment area 42 extends 1⅔ cm into breast 31 in this example, as bolus 25 is 1⅔ cm thick (as shown in FIG. 5, 10 MeV would normally extend 3⅓ cm into the breast 31—the 1⅔ cm thick bolus 25 pulls 1⅔ cm of that energy region upward into bolus 25, leaving just 1⅔ of breast 31 to be treated). FIG. 7 shows a detail showing disposable plastic cling wrap 17 (which could be for example Glad brand cling wrap or plastic wrap by Saran) stretched over the end of tube 15 proximal the breast 31 (not shown) to flatten breast and/or minimize the chance of direct bolus contact with body fluids 31 and allow even penetration of the radiation from an IOERT machine. Cling wrap 17 could be used as well with the present invention, though when boluses 21-27 are integral with tube 15, the boluses would flatten breast 31 and allow even penetration of the radiation from an IOERT machine, even without cling wrap 17. FIGS. 5 and 6 show prior art IOERT systems in which the amount of radiation reaching the breast 31 is controlled electronically, rather than with the use of boluses 21-27 of the present invention. As can be seen in FIG. 5, a 10 MeV beam will typically penetrate and treat 3⅓ cm of breast 31 tissue, while a 6 MeV beam (see FIG. 6) will typically penetrate and treat 2 cm of breast 31 tissue. While theoretically one can use just about any type of material for boluses 21-27, it is best to use an isodense material (a material which has roughly the same density as human breast tissue) because it avoid some problems of other densities. With an isodense material such as poly(methyl methacrylate), little math is needed to determine how much to use; one simply determines the amount of attenuation desired and selects the collimator tube 15 with the bolus 21-27 that corresponds to that attenuation (bolus 21 for 1 MeV, bolus 22 for 2 MeV, etc.). If one uses a material with a high atomic number like lead, more of the radiation will be transformed into Bremsstrahlung, through the interaction of the treatment beam electrons with the nucleus of the molecules they pass by in the bolus. Brehmstrahlung is produced when the electron beam hits the tissue, but this happens regardless of the method of energy attenuation. Bremsstrahlung is just a statement of the conservation of energy in an indirect manner. When the electrons have their energy and/or direction changed, some of this energy is released in the form of other radiation, like heat or x-rays. This is Bremsstrahlung. One wants to minimize this during radiation treatment since Bremsstrahlung is a more penetrating form of radiation and has much greater shielding requirements If one uses too dense a material, there are two problems: 1) the precision of the width of the bolus increases dramatically (if one used an extremely dense material, the difference between boluses would be measured in mm, not cm) and 2) more Bremsstrahlung radiation is created. Imagine electrons going into a tight net. The larger the atomic number and thus atoms, the smaller the holes. With smaller holes, more electrons hit the net, causing the string to vibrate. In this example, the vibrations would be Bremsstrahlung. Using a material that is less dense than tissue theoretically could be advantageous as there is less decelerating radiation because there are lower atomic number atoms involved and thus smaller nuclei. Ideally, if Bremsstrahlung were the only concern, one would want to use hydrogen gas compressed to a density near that of tissue as this would produce the least Bremsstrahlung since hydrogen is the smallest nucleus in the universe known to man. Unfortunately, hydrogen gas is highly explosive and not suitable for this purpose. While using other gases would work as well, this method is cost prohibitive because the manufacturing process would be much more complicated than injecting Lucite into a mold. In addition to higher manufacturing costs, the compressed-gas bolus would be extremely prone to breaking if dropped as it is hollow with a highly compressed gas inside, unlike Lucite which is a solid block of plastic. Moreover, most doctors use isodense material and it is the standard, therefore no real research has been done into a hypodense bolus. The collimator filters or boluses 21-27 can be held in place on the distal end of tube 15 with a simple t-bone clamp (such as that shown in http://www.hclfasteners.com/shoppdfs/t-bolt.pdf). This method helps to ensure that there a tight fit that is perfectly aligned with the end of the collimator tube 15. It is preferable for the collimator filters 21-27 to have a diameter substantially equal to the outer diameter of tube 15 so that all or substantially all radiation traveling through tube 15 likewise travels through a filter 21-27 (otherwise, there could be areas where the radiation would go deeper into the patient's tissue than desired). The present inventor believes that the best way to achieve this is to simply make the collimator filters 21-27 integral with collimator tube 15. Other possible, but not preferred, means of attachment of boluses 21-27 to tubes 15 include a screw-on bolus, tape to hold the bolus on, a t-bolt clamp, or even the right size thick rubber band. The problem with all of these methods is that they introduce human error, which can be just as dangerous as computer error. Therefore, the preferred means of attachment that maintains the safety of removing a computer, while not introducing any other errors, is making the bolus part of the collimator. The diameter of collimator tube 15 and collimator filters 21-27 can be, for example, about 1-30 cm, preferably about 2-25 cm, more preferably about 3-15 cm, and for example about 5 cm or 10 cm. The length of collimator tube 15 can be, for example, about 95.5-104.5 cm, preferably about 98-102 cm, more preferably about 99-101 cm, and for example about 100 cm. Precision Accelerators will have a machine that is more stable and more precise because it uses a physical method of modulation. As long as its PMMA boluses 21-27 are accurate enough, the apparatus 10 will modulate the beam better, without need for extensive electronics, than the current methods do allowing for transportation. The present inventor believes that all competitors of Precision Accelerators use a method of varying their energy that is directly proportional to beam error bands. This is because electronically varying the current cannot go below a certain unit of accurate variation. This is what every system uses. Precision Accelerators's physical method is a more precise method of varying the exact electron energy and direction because it is physically verified and therefore has no error. The beam variation is reduced to insignificant levels for virtually no additional cost, while increasing the features of the machine to daily inter-hospital transport. While the difference is subtle, the means of variation has a large impact on the way Precision Accelerators's machine is used, increasing efficiency. The present inventor believes that the best way to join a bolus 21-27 to the tube 15, which must be confirmed by testing, is to make the bolus 21-27 integral with the collimator tube 15 when molding the tube 15. This allows the system to use existing interlocks and not have to engineer anything else. Moreover, it is very difficult to lose or break a 100+ cm tube of thick plastic. Therefore, it is highly unlikely that this will be lost. As long as this is not inefficient in setting up, this is most likely the best because there will be no parts lost. The following is a list of parts and materials suitable for use in the present invention: Parts Number Description 10 IOERT apparatus of the preferred embodiment of the present invention 11 IOERT machine (such as an industrial linear accelerator, such as a 10 MeV Portac model produced by L&W Research Inc. of Connecticut—http://www.lwresearch.com/products/portae/portac.html) 14 connector between tube 15 and tube 16 15 plastic collimator tube (such as PMMA) 16 plastic tube connecting collimator tube 15 to IOERT machine 11 17 plastic cling wrap placed over proximal (to patient) end of tube 15 to flatten breast 31 18 connection when boluses 21-27 are not integral with tube 15—otherwise, boundary between open tube 15 and boluses 21-27 when tube 15 and boluses are integral 19 connector between tube 16 and IOERT machine 11 21 ⅓ cm thick bolus (such as PMMA) 22 ⅔ cm thick bolus (such as PMMA) 23 1 cm thick bolus (such as PMMA) 24 1⅓ cm thick bolus (such as PMMA) 25 1⅔ cm thick bolus (such as PMMA) 26 2 cm thick bolus (such as PMMA) 27 2⅓ cm thick bolus (such as PMMA) 31 human breast being treated for cancer 41 region of skin-sparing dose 42 region of 100% energy at 10 MeV 43 region of 100% energy at 6 MeV 50 energy producing head of IOERT machine 11 All measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise. All materials used or intended to be used in a human being are biocompatible, unless indicated otherwise. The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.

summary

summary

abstract

A method and a device for high spatial resolution imaging of a plurality of sources of x-ray and gamma-ray radiation are provided. The device comprises a plurality of arrays, with each array comprising a plurality of elements comprising a first collimator, a diffracting crystal, a second collimator, and a detector.

043115608

claims

1. A stabilizing device for a nuclear reactor control rod, the rod being adapted for telescoping movement within a guide tube having an upward flow of liquid coolant therethrough comprising: a base section for rigidly connecting the upper end of the device to the lower end of the poison-bearing portion of the rod; cantilevered spring means spaced about and extending longitudinally downward from the outer circumference of the base means to form an open-ended hollow inner region; said cantilevered spring means having shoulders thereon for contacting the guide tube wall and providing an interference fit therebetween having substantially uniform radial forces distributed around the inner walls of the guide tube whereby the rod is centered within the guide tube and may longitudinally move in the tube; and whereby at least some of the liquid coolant may bypass the shoulders through said hollow inner region. an open-ended, hollow elongated member rigidly connected to and extending longitudinally downward from the lower end of the poison-bearing portion of the rod, the member having a transverse outer cross section smaller than that of the inside of the guide tube; interference means projecting outwardly from the elongated member and cooperating with the member and the inside wall of the guide tube, for centering the rod within the guide tube; and flow means formed on the elongated member for defining a flow path whereby liquid entering the hollow region within the elongated section may exit the elongated section above the interference means. 2. The device recited in claim 1 wherein the shoulders are on the lower end of each spring. 3. The device recited in claim 1 wherein each shoulder is intermediate the end of a spring, and wherein the lower ends of the springs are joined by a common ring which defines the entrance to the hollow inner region. 4. The device recited in claims 2 or 3 wherein the total shoulder area for contacting the tube is at least 1/2 the cross-sectional area of the tube. 5. The device recited in claim 4 wherein the spring constant at the shoulder of each spring is between 0.01 and 0.05 inches per pound. 6. The device recited in claim 5 wherein the spaces between the springs provide a flow path for coolant to bypass the shoulders. 7. In a nuclear reactor control rod of the type having neutron poison within a sealed container adapted for telescoping movement within a guide tube having an upward flow of liquid coolant therethrough, the improvement comprising: 8. The improved control rod of claim 7 wherein the elongated member comprises a plurality of adjacent cantilever springs and the interference means comprises a shoulder on each of the cantilever springs.

050826174

description

DESCRIPTION OF PREFERRED EMBODIMENTS The preferred embodiment of the invention, shown schematically in FIG. 1, comprises an isotopic heat source 10. For purposes of illustration, one fuel stack 12 is shown adjacent to one heat pipe 14 which extends from the heat source 10 to a heat exchanger 16. The heat pipe 14 contains a working fluid 18 that transfers heat from the heat source 10 to the heat exchanger 16. The working fluid 18 flows along an inner surface 20 of the heat Pipe 14 which comprises means for capillary action. The heat pipe working fluid 18 can be restricted by the pressure of a single phase gas 22, the source of which is a gas reservoir 24. FIG. 2 is a vertical cross-section of a preferred embodiment of the heat source 10. FIG. 3 is another view of the embodiment shown in FIG. 2 along line 3--3. FIG. 2 illustrates a plurality of fuel stacks 12. The fuel stacks 12 comprise a refractory fuel 26 and diluent 28. The fuel 26 is neutron activated to form a relatively short-lived isotope that produces heat. The preferred embodiment for the fuel 26 is thulium-169 in the form of thulium oxide (Tm.sub.2 O.sub.3). The diluent 28 is a refractory, heat conductive, and low atomic weight material. The preferred embodiment for the diluent 28 is graphite. In the preferred embodiment, the fuel stacks 12 are formed of a plurality of thin individual layers of thulium fuel 26 and graphite 28. The thulium layers 26 and graphite layers 28 are stacked in an alternating pattern. The fuel stacks 12 are irradiated in a conventional manner with thermal neutrons, converting thulium-169 to thulium-170 (and thulium-171, etc.). After irradiation, one or more of the fuel stacks 12 are mounted in one or more holes 32 in a heat block 34, preferably made of graphite. In the preferred embodiment, the fuel stacks 12 are cylindrical and fit snugly into the heat block 34. A plurality of heat pipes 14 for heat removal are arranged in a plurality of holes 36 in the heat block 34. In the preferred embodiment, the heat pipes 14 are enclosed at both ends and may be oversized in length, extending beyond the heat exchanger 16 to provide additional heat rejection area. The heat block 34 is surrounded by a sealed structural container 38, which is surrounded by an insulation layer 40. The heat block 34 is also encased in at least one layer of radiation shielding 42,44, made from a suitable structural material such as iron or tantalum. In the preferred embodiment, an inner layer of the shielding 42 surrounds the insulation layer 40 and an outer layer of the shielding 44 surrounds the inner layer of the shielding 42. Free convection space fills the cavity 46 defined by the two layers of the shielding 42,44. Holes 48 defined by the outer layer of the shielding 44 are located along the inside perimeter of the outer layer of the shielding 44. The holes 48 are present at both the top 50 and bottom 52 ends of the heat source apparatus 10. In the preferred embodiment, the neutron activated fuel 26 is thulium in the form of thulium oxide. However, thulium in the form of thulium hydride or thulium carbide, as well as an altogether different radionuclide, might be used. In the preferred embodiment, the diluent 28 is graphite. Alternative embodiments for the low atomic weight diluent 28 are possible, including: zirconium hydride (hydrogen), beryllium oxide (beryllium), boron, lithium, and beryllium. Graphite is advantageous as a diluent 28 for several reasons. Graphite is highly refractory, which allows the heat source 10 to operate at high temperatures. Graphite and thulium oxide do not react appreciably at high temperatures. Also, graphite is readily available and inexpensive. Diluting thulium layers 26 with intervening graphite layers 28 may enhance the production of thulium-170 in the irradiation reactor and reduce the shielding needed around the fuel stack 12. The production of thulium-170 is increased because graphite acts as a moderator during irradiation. Shielding of the fuel stack 12 is reduced because graphite, being a low atomic weight material, produces less bremsstrahlung radiation than high atomic weight materials. Graphite also stops the beta particles and secondary electrons produced in radioactive decay. In the preferred embodiment, the fuel stack 12 comprises alternating layers of fuel 26 and diluent 28. The layers of thulium fuel 26 and graphite diluent 28 may be thin, flat, circular individual disks or wafers. The layers of thulium fuel 26 do not exceed one centimeter thickness in order to reduce flux depression. The thulium fuel layers 26 are placed with alternating layers of diluent 28 to form the fuel stack 12. In an alternate embodiment, the thulium fuel 26 can be flame sprayed or plated on graphite disks 28. Thulium oxide powder and graphite powder could also be mixed and heated to form a sintered body. After the fuel stacks 12 are irradiated, the stacks 12 may be placed directly into the heat block 34, eliminating post-activation handling. Alternatively, graphite layers 28, possibly of another thickness, may be substituted or inserted in the fuel stacks 12 to further minimize bremsstrahlung radiation. Excess graphite layers 28, of course, could be removed. The fuel stacks 12 are designed to maximize the opportunity for salvaging and recycling thulium fuel 26 and graphite diluent 28 from expended fuel stacks 12. The heat source 10 is designed to permit refueling for long term use. The heat pipes 14 provide means for heat removal. The heat pipes 14 contain a heat pipe working fluid 18, such as sodium, which is chosen according to the desired heat block 34 temperature. The working fluid 18 transfers heat from the heat source 10 to the heat exchanger 16. The heat pipes 14 are oversized in length to carry the working fluid 18 to the heat exchanger 16 and to permit passive cooling. In the preferred embodiment, the working fluid 18 transfers heat by repeated cycles of vaporization and condensation. The working fluid 18 vaporizes in the region of the fuel stack 12. The vapor expands and travels through the heat pipe 14 to the heat exchanger 16. The vapor cools, releases heat and condenses onto an inner surface 20 of the walls of the heat pipe 14 in the region of the heat exchanger 16. The inner surface 20 has means to allow capillary action. The condensed working fluid 18 flows back to the heat source 10 region by the capillary action means on the inner surface 20 to begin another cycle of vaporization and condensation. This heat transfer system can operate in a zero gravity environment or in a modest gravity field in any orientation. During the operation of the heat source 10 with the heat exchanger 16, the flow of the heat pipe working fluid 18 is restricted at an easily controlled interface by a single phase gas 22. The single phase gas 22, such as argon, is supplied from a sealed reservoir 24 attached to a heat pipe 14. The pressure of the single phase gas 22 restricts the flow of the working fluid 18 to direct heat to the heat exchanger 16 for maximum efficiency. Therefore, if the heat block 34 overheats, the vapor pressure of the working fluid 18 increases, causing displacement of the single phase gas 22, thereby expanding the heat rejection surface of the heat pipes 14 and permitting passive cooling. Conversely, if the pressure of the single phase gas 22 is increased, the working fluid 18 is displaced and the surface area of the heat pipes 14 for heat rejection is reduced (shortened). In an alternative embodiment, the heat pipes 14 need not extend linearly, but may be designed to fold back around toward the heat source 10 to reduce space requirements. Additionally, the number and arrangement of the heat pipes 14 and fuel stacks 12 are variable, depending on the power density and efficiency of heat removal required. The structural container 38, the insulation layer 40 and the radiation shielding 42,44 may be made of a variety of materials, depending on the particular use requirements. One embodiment for the structural container 38 is an x-ray absorbing material such as tantalum. The preferred embodiment for the insulation layer 40 is a material designed to fail at a high temperature that is below the failure temperature of the structural container 38. In the case of heat block 34 overheating, the insulation layer 40 would melt away, allowing thermal radiation to occur from the structural container 38 to the layer of inner shielding 42, thus providing containment and heat dissipation. Aerogel is one example of such an insulation material. The free convection space 46 between the layers of the shielding 42,44 provides yet another opportunity for passive cooling of the heat source 10 in the event of heat block 34 overheating. The description of the invention presented above is not intended to encompass all variations of the system but has attempted to present illustrative alternatives. The scope of the invention is intended to be limited only by the appended claims.

summary

summary

description

This application claims priority to the German application No. 10 2004 027 163.1, filed Jun. 3, 2004 which is incorporated by reference herein in its entirety. The invention relates to a method of compensating for image faults in a digital x-ray image recording which has been created by a radiographic source, an anti-scatter grid and a digital x-ray detector such as an image amplifier or solid-state image detector, said image faults having been caused by decentering, defocusing or defects of the anti-scatter grid or by the Heel effect and causing a reduction in the intensity of the primary radiation falling on the x-ray detector. Anti-scatter grids are used in x-ray systems so that when an object under examination is illuminated with x-rays only direct information-bearing primary radiation reaches the detector from the x-ray tube. The scattered radiation which makes the image noisy is blocked by the anti-scatter grid in order to improve the quality of the x-ray image. Anti-scatter grids consist of very thin strips of lead which are embedded into paper, with up to 80 strips per centimeter being used. These lead strips of the anti-scatter grid are not arranged in parallel but are turned at a slight angle to each other and aligned to a specific optimum focal distance between the x-ray tube and the detector, for example 1500 mm. In practice however x-ray systems are operated at different tube-detector distances so that they are defocused, producing shadowing in the edge area of the x-ray image recording. Shadowing can also arise because the tube is not centered, that is it is not located precisely over the center point of the anti-scatter grid. Heel effect refers to the reduction in the intensity of rays on the anode side through the x-ray tube itself. Shadowing can also occur because of an incorrectly positioned or defective grid. This shadowing normally increases towards the edge at right angles to the direction of the lead laminations, while remaining constant in the direction of the lead laminations. The problem here is that the reduction in intensity at the edge of the x-ray image may not amount to more than 40%, defined by the ICE (Convention 606271978). This means that the allowable distance range between the tubes and the detector in which the system may be operated is limited. Furthermore the shadows themselves then disturb the image when the system is operated in the valid range. In addition the shadowing can make diagnosis of the illness images more difficult. It has already been proposed that these intensity reductions be corrected by a theoretical model. The Boldingh formula describes the intensity reduction as a function of specific characteristic grid values, for example the aspect ratio r, as well as the distance between the x-ray tube and the detector and the decentering. It has been shown however that this model can only reproduce the intensity reduction behavior of anti-scatter grids imprecisely. The deviations arising when the formula is applied are attributed to the fact that unknown variables such as incorrect grid positioning, grid defects or the Heel effect cannot be taken into account by Boldingh's formula. An object of the invention is to specify a method which has a greater degree of accuracy when compensating for the image faults described above in an x-ray image recording. This object is achieved by the claims. Unlike the known method which is based on the Boldingh formula, the correction of the x-ray image recording is not undertaken solely on the basis of a theoretical model but the actual individual intensity reduction profile of the anti-scatter grid in the illumination system operated is determined in order to correct the x-ray image recording correspondingly. The advantage exhibited by the method in accordance with the invention is that all influencing factors which influence the x-ray image recording can be taken into account. The method can also be executed if the individual influencing factors and their effect on the x-ray image recording are not known in detail. With the method in accordance with the invention there is provision for the actual intensity reduction to be measured into which all influencing factors are entered. In this way unknown parameters, for example an incorrect positioning of the anti-scatter grid or asymmetrical effects such as the Heel effect of decentering can be recorded and corrected. The “data driven” model in accordance with the invention thus reflects the actual circumstances significantly more accurately than a theoretical model. In a further embodiment of the invention provision can be made for blank images, in which there is no object between the radiographic source and the anti-scatter screen, to be recorded to measure the intensity reduction. These blank images are used to record the intensity reduction behavior of the entire x-ray system, consisting of radiographic source, anti-scatter screen and solid-sate image detector. The individual intensity reduction behavior can be determined on the basis of the blank images, furthermore the required correction parameters can be determined with which the x-ray image recording can subsequently be corrected. The production of the blank image is thus a type of calibration measurement. With the method it is especially preferred for the x-ray image to be recorded as a digital image matrix with columns and rows and for a profile line describing the intensity reduction to be calculated. The x-ray image recording delivers as a result a matrix with individual values for each x-ray sensitive pixel of the x-ray detector, for example of a solid-state image detector. In this case for example low pixel values of the digital image can represent high x-ray incidence and vice versa. The blank images recorded of anti-scatter grids show that the intensity reduction of the primary radiation increases from the middle of the anti-scatter grid over which the x-ray source is located towards the sides. In the direction at right angles to this of the plane of the anti-scatter grid in parallel to the direction of the lead laminations, represented by the columns of the image, the intensity reduction can be assumed to be constant in a initial approximation. Accordingly a profile line describing the intensity reduction which is representative for the anti-scatter grid and for the entire x-ray system can be calculated from the image matrix which represents a surface profile of the intensity reduction. The summed values of the individual columns which form a one-dimensional vector can be smoothed by multiple lowpass filtering. In this way individual extreme values can be filtered out. With the method it is further preferred that the profile line embodied as a vector is scaled to values between 0 and 1. For scaling the vector is divided by its maximum value. In a further embodiment of the invention there can be provision for the minimum of the profile line to be determined. This minimum which lies in the vicinity of the center of the anti-scatter grid is the location with maximum transmission. However it does not necessarily have to lie exactly in the center but can for example be shifted by a decentering of the tubes or by the Heel effect. With the method accordance with the invention there can be provision that for the sections of the profile line to the left and the right of the minimum the equations of a straight line of the best fitting lines of the corresponding parts of the profile line are determined. To obtain a uniform description of the profile the average values of the gradients and the axis sections of the two individual straight lines are determined. Thus the two areas to the right and the left of the center can be approximated by a single best fitting line. With the method in accordance with the invention there can further be provision for the x-ray image recording to be corrected with reference to the minimum of the profile line and the gradient of the equations of a straight line. The minimum and the gradients determined serve as correction parameters for the intensities of the x-ray image recording. The decentering, meaning the shifting of the x-ray emitter center point is already known. Likewise the gradient of the straight lines is known. The individual columns of the image matrix are multiplied by these correction parameters so that corrected recorded images are produced which no longer show any intensity decrease effects. The image brightness can be corrected on the basis of the correction parameters. In accordance with the invention there can also be provision for a number of blank images to be recorded at different focal distances between the radiographic source and the solid-state image detector and/or various decenterings to be recorded in order to determine the relationship between the distance between radiographic source and solid state image detector as well as the decentering and the straight line parameters including the profile minimum if this relationship is known, the best fitting lines can subsequently be determined for any given distance between the radiographic source and the detector. The invention also relates to an x-ray system for recording x-ray images, comprising a radiographic source, an anti-scatter grid and an x-ray detector. In accordance with the invention the x-ray system is embodied to compensate for image faults by means of the method described. The x-ray system 1 shown in FIG. 1 consists of a schematic diagram of an x-ray tube 2, an anti-scatter grid 3 and an image detector 4 arranged below the anti-scatter grid. On illumination of an object 5, which is located between the x-ray tube 2 and the anti-scatter grid 3, direct information-bearing primary radiation 6 passes through the object 5 to reach the detector 4. A part of the radiation however is deflected by inhomogeneities, for example bones, in the object and thus becomes scattered radiation which disturbs the image. This is subsequently blocked off by the lead laminations of the anti-scatter grid 3. In this way scattered radiation 7 which disturbs the image is prevented from reaching the detector 4. With the x-ray system 1 the x-ray tube 2 is adjustable vertically so that different distances between the x-ray tube 2 and the detector 4 can be set. Since the individual lead strips from which the anti-scatter grid is constructed are inclined at a slight angle, the anti-scatter grid 3 is only optimally aligned to the x-ray tube 2 at a specific focal length, which is 1500 mm in the exemplary embodiment shown. If the x-ray system is operated with a different distance between the x-ray tube 2 and the detector 4 so that it is defocused, shadowing occurs in the edge area with conventional image recording methods. FIG. 2 shows a flowchart of the method in accordance with the invention. The method for correction of image faults is based on calculating the intensity reduction profile of the anti-scatter grid 3. To this end different blank images are included in step 8. To record a blank image there is no object between the x-ray tube 2 and the anti-scatter grid 3. The blank images thus reflect the intensity reduction of the radiation by the anti-scatter grid 3. For a specific distance between the x-ray tube 2 and the anti-scatter grid 3 or the detector 4 it is sufficient to record one blank image. The method however provides for a number of blank images to be produced at different focal lengths f and/or for different sideways deflections of the tube (defocusing) so that it is possible to correct all x-ray images, regardless of the relevant focal distance. The computation of the intensity reduction profile for the fixed focal distance f will be explained below. The digital image is available as a matrix with x columns and y rows of intensity values m(ij). The equation below sums the columns of the image matrix vertically and a one-dimensional vector is obtained which is smoothed by multiple lowpass filtering (steps 9, 10): I ⁡ ( x ) = ∑ i = 1 Y p ⁢ m ix ( 1 ) In procedural step 11 the vector is scaled, so that all values lie between 0 and 1. These values correspond to the percentage intensity reduction. It is assumed here that the intensity reduction is 0% in the center and 100% at the shielded edges. The intensity reduction profile is as follows: p ⁡ ( x ) = 1 - I ⁡ ( x ) max ⁡ ( I ⁡ ( x ) ) ( 2 ) The scaling of the vector is shown in the flowchart of FIG. 2 as procedural step 11. The resulting intensity reduction profile is at its minimum in the vicinity of the center of the anti-scatter grid 3, which can be determined in procedural step 13 by the following equation:xm:=ARGMIN(p(x))  (3) In procedural step 14 the intensity reduction profile is divided up into a left-hand part and a right-hand part and a linear regression of both parts is computed, then the corresponding parameters of the two individual equations are averaged. In this way the intensity reduction profile can be expressed by a straight line equation. The equation of the profile line is:V(x)=M·|x−xm|+Bd  (4)In this equation M is the gradient of the linear intensity reduction profile. With the Boldingh formula the expected intensity reduction of the radiation can be calculated as a function of the distance f between the X-ray tube and the detector for a known decentering (shift) z for each point c: V ⁡ ( c ) = { r ⁡ ( c + z f - c f 0 ) r ⁡ ( c f 0 - c + z f ) ⁢ ⁢ if ⁢ ⁢ { f ≤ f 0 f > f 0 ( 5 ) By transformation the following equation is obtained: V ⁡ ( x ) = F ·  r f - r f 0  ·  x - x m  ( 6 ) In FIG. 1 the intensity reduction profile V(x) is shown below the detector 4 in qualitative terms. With r being a characteristic value of the anti-scatter grid, known as the shaft ratio which describes height to width of the paper strip. The factor F := mm Pixel ( 7 ) is a variable which allows the formula to be used on pixels instead of on “millimeters”. This value is the opposite value of the pixel density. With equation (6) and equation (3) the decentering in millimeters can be defined (procedural step 15):z(xm)=F·(xm−Xc)·|1−f/fo|  (8) The main factor here is that it is of no significance how the shift is triggered. Since the computation method starts from the actual intensity reduction method, both the influences of the Heel effect and also the decentering of the x-ray tube 2 or other influences can be taken into account. After the variables xm and M have been determined the image can be corrected in procedural step 16 by multiplying each column by the correction factor: C ⁡ ( x ) = 1 1 - M ·  x - x m  ( 9 ) This formula can be used to correct the image brightness. A description is given below of how the intensity reduction profile can be computed for any given distances between the X-ray tube and the detector. So that different focal distances f can be taken into account for image correction, a series of calibration images are recorded for different states f, then the required correction parameters are calculated. To calculate the decentering xm for any given focal distances f, a number of blank images are recorded with an anti-scatter grid and xm and z are determined. The images can be recorded with different radiation doses. It has been discovered that a linear relationship exists between the decentering and the distance f between the x-ray tube and the image detector. On the basis of the blank images for the calibration the decentering z(f) is determined for each blank image as well as subsequently the linear adaptation of the decentering defined over the distance f. With this linear adaptation the decentering xm can now be determined for any given distance f, i.e. between the calibration points. To enable the image to be corrected the gradient of the intensity reduction profile for given distances f must also be calculated. There are two possible options for calculating the profile gradient. The first variant is based on the Boldingh formula and calibration is with reference to the measurement data. Calibration consists of calculating the linear relationshipMB≈K·MD  (10)with MD being the gradient of the measurement data. K is a calibration factor and specifies the relationship between the profile calculated from the measured data and the Boldingh formula. In this case the peripheral condition that MD=0 for f=f0 should apply is to be taken into account. For any given distances f the intensity reduction profile is calculated by first determining the decentering. Subsequently the intensity reduction is calculated using the Boldingh formula and multiplied by K. This produces the intensity reduction profile for the relevant focal distance f. The radiological image is then corrected with equation (9). With the second variant the Boldingh formula is not used, but the model is based entirely on the measured data. From the different calibration images the gradients for the right and left half MR and ML are calculated by a linear approximation separately for f<f0 and f>f0. If the x-ray tube is at its optimum focus the peripheral condition MR(f0)=ML(f0)=0 applies, meaning that no correction is necessary. For a given distance f the intensity reduction profile is determined by calculating the decentering. Subsequently the gradient of the intensity reduction profile is calculated from the linear approximation of the calibration images. This produces the intensity reduction profile for this focal distance f. The radiological image can again be corrected with equation (9). FIGS. 3a to 3c show the measured and calculated intensity reduction profile for different distances between the x-ray tube and the detector. The horizontal axis corresponds to the x-axis shown in FIG. 1. The intensity reduction is entered on the vertical axis, and this can be between 0 and 1. Three curves are also shown in each of FIGS. 3a to 3c. Curve a represents the smoothed profile (Ix). Curve b represents the intensity reduction according to the Boldingh formula. Curve c shows the intensity reduction calculated in accordance with the inventive method. In FIG. 3a the focal distance is f=1500 mm. It can be seen that the differences are comparatively small between profile of curve a based on the measured values and the curves b and c. FIG. 3b represents the case in which the focal distance amounts to f=1150 mm. It can be seen that curve c delivers a significantly better approximation of the intensity reduction than does the Boldingh formula (curve b). The same applies to the focal distance f=1000 mm shown in FIG. 3c. The differences between curves a and c only amount to a few percent. Since the anti-scatter grids are currently constructed from lead strips and the intensity reduction is thus constant in one direction, the direction of the lead laminations, the one-dimensional correction in the direction of the columns is sufficient. The method can however usefully be expanded to two dimensions if another scanning method, for example a grid, requires this.

048083372

abstract

A compressible bellows type metal canister is used in a hot pressing process for immobilizing high level radioactive nuclear waste material in the form of synthetic rock, the canister comprises a base wall and a corrugated bellows side wall of generally circular cross-section, concentrically arranged within the corrugated side wall is a cylindrical liner. In the center of the base wall a conically-tapered aperture is provided with a filter plug. Diametrically opposed apertures are provided in the base wall and are connected by an outlet pipe for removal of waste gases.

048881520

claims

1. A grid for assembling a plurality of nuclear fuel rods, comprising a plurality of cylinder portions and means for joining said cylinder portions in a parallel array, wherein each of said cylinder portions has a substantially polygonal cross section comprising a plurality of sides connected by a corresponding plurality of flat portions, each one of said fuel rods being encompassed by a corresponding one of said cylinder portions, each cylinder portion having a plurality of cut-outs, each cut-out extending over a corresponding part of the height of said cylinder portion and having a flat portion of a different cylinder portion inserted therein, whereby each of said nuclear fuel rods not arranged on the periphery of said grid bears against a flat portion of each of a predetermined number of said cylinder portions, but does not bear against any portion of the cylinder portion encompassing the respective fuel rod. 2. The grid as defined in claim 1, wherein said predetermined number is four, said substantially polygonal cross section is a square and said flat portions are truncated corners. 3. The grid as defined in claim 1, wherein said predetermined number is three, said substantially polygonal cross section is a triangle and said flat portions are truncated vertices. 4. The grid as defined in claim 2, wherein each of said cut-outs comprises a recess extending from a top edge of said cylinder portion. 5. The grid as defined in claim 3, wherein each of said cut-outs comprises a window formed in said cylinder portion. 6. The grid as defined in claim 1, further comprising an edging arranged to peripherally surround said plurality of cylinder portions, said edging comprising a plurality of projecting portions, each of said projecting portions being inserted in a cut-out of a corresponding one of said cylinder portions, the nuclear fuel rod encompassed by said corresponding one of said cylinder portions bearing on said corresponding projecting portion. 7. The grid as defined in claim 1, further comprising fin means extending from the top edge of at least one of said cylinder portions for disturbing the fluid flowing through said grid. 8. The grid as defined in claim 1, wherein each of said cut-outs is formed in a portion of said cylinder portion comprising one of said flat portions.

claims

1. An apparatus comprising:a nuclear reactor comprising a pressure vessel containing primary coolant water and further containing:a nuclear reactor core comprising fissile material,a mounting/electrical distribution plate secured entirely within the pressure vessel and configured to be submerged in the primary coolant,a set of control rod drive mechanism (CRDM) units mounted directly on the mounting/electrical distribution plate, anda plurality of cable modules mounted in receptacles of the mounting/electrical distribution plate wherein each cable module includes mineral insulated (MI) cables connected with one or more of the CRDM units, the cable module including its MI cables being removable as a unit from the receptacle of the mounting/electrical distribution plate. 2. The apparatus of claim 1 wherein each CRDM unit includes a plurality of electrical power connectors mating with corresponding electrical power connectors of one or more of the cable modules. 3. The apparatus of claim 1 wherein each CRDM unit includes a plurality of electrical power connectors mating with corresponding electrical power connectors of exactly one of the cable modules. 4. The apparatus of claim 1 wherein:the mounting/electrical distribution plate has a plurality of openings through which connecting elements pass that connect the CRDM units with control rods comprising neutron absorbing material, the CRDM units being configured to move the control rods into and out of the nuclear reactor core via the connecting elements. 5. The apparatus of claim 1 wherein:the mounting/electrical distribution plate has a plurality of openings through which the connecting elements pass. 6. The apparatus of claim 1 wherein:the mounting/electrical distribution plate includes a set of hydraulic lines disposed on or therein that are connected with the electric devices. 7. The apparatus of claim 6 wherein the cable modules mounted in the receptacles of the distribution plate overlay the set of hydraulic lines. 8. The apparatus of claim 7 wherein the cable modules define conduits or raceways through which the set of hydraulic lines run. 9. The apparatus of claim 1 wherein each cable module cooperates with the receptacle of the mounting/electrical distribution plate in which the cable module mounts to define a conduit or raceway through which the MI cables of the cable module run. 10. The apparatus of claim 9 wherein each cable module includes standoffs at the periphery of the cable module to define the conduit or raceway through which the MI cables of the cable module run. 11. A mounting/electrical distribution plate assembly for use in a nuclear reactor including a pressure vessel containing primary coolant water and a set of control rod drive mechanism (CRDM) units, comprising:a mounting/electrical distribution plate secured entirely within the pressure vessel and submerged in the primary coolant,a plurality of cable modules mounted in receptacles of the mounting/electrical distribution plate wherein each cable module includes mineral insulated (MI) cables connected with one or more of the CRDM units, the cable module including its MI cables being removable as a unit from the receptacle of the mounting/electrical distribution plate,wherein the set of control rod drive mechanism (CRDM) units is mounted directly on the mounting/electrical distribution plate. 12. The mounting/electrical distribution plate assembly of claim 11 wherein each CRDM unit includes a plurality of electrical power connectors mating with corresponding electrical power connectors of one or more of the cable modules. 13. The mounting/electrical distribution plate assembly of claim 11 wherein each CRDM unit includes a plurality of electrical power connectors mating with corresponding electrical power connectors of exactly one of the cable modules. 14. The mounting/electrical distribution plate assembly of claim 11 wherein:the mounting/electrical distribution plate includes a set of hydraulic lines disposed on or therein that are connected with the electric devices. 15. The mounting/electrical distribution plate assembly of claim 14 wherein the cable modules mounted in the receptacles of the distribution plate overlay the set of hydraulic lines.

summary

052182096

description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The ion implanter shown in FIG. 1 has a wafer holding disk 1 of the centrifugal holding type, and is characterized in that each wafer rest lb of the disk 1 has a wafer holding surface 1c curved nearly in the same manner as the conically-curved inner surface of the disk 1. Since wafer rest 1b of the wafer holding disk 1 of the ion implanter provided in accordance with the present invention has the wafer holding surface 1c curved nearly in the same manner as the conically-curved inner surface of the disk 1, the wafer 2 is pushed onto the wafer holding surface 1c by a centrifugal force due to the rotation of the disk so that the top surface of the wafer is conically curved. For that reason, an ion beam 3 is irradiated upon the entire top surface of the wafer 2 always perpendicular to the surface, namely, the angle of the implantation of the ions into the surface does not deviate. A preferred embodiment of the present invention is hereafter described with reference to FIGS. 1 and 2. FIG. 1 corresponds to FIG. 6, and shows a section of the wafer holding disk 1 of the ion implanter in the circumferential direction of the disk along the line B--B shown in FIG. 5. The disk 1 has wafer rests 1b, in turn, having wafer holding bottoms 1c on which wafers 2 are held. Each wafer holding bottom 1c is a curved surface defined by a cone having the same axis and slope as the conically-curved inner surface of the peripheral portion 1a of the wafer holding disk 1. When the disk 1 is rotated, each wafer 2 is pushed onto the wafer holding bottom 1c of the wafer rest 1b by centrifugal force so that the surface of the wafer is curved to conform with the wafer holding bottom. For that reason, an ion beam 3 is irradiated upon the surface of the wafer 2 perpendicularly to the surface at any point thereon with regard to the circumferential direction of the disk 1, as shown in FIG. 2. In other words, the angle of implantation of ions to the wafer 2 by the implanter does not deviate from the perpendicular. If such a wafer 2 is held on a spherically curved rest (not shown) by an annular clamper at the time of the implantation of ions into the wafer, the wafer 2 is spherically curved so that the maximum deformation of the peripheral edge of the wafer relative to the center thereof is nearly as large as 1 mm. As for the ion implanter of the present embodiment, the wafer 2 is not spherically curved but conically curved so that the influence of the curving on the quality of the ion-implanted wafer 2 is much smaller than that of the spherical curving of the former wafer, as understood through the examination of the case that when pieces of paper are wound on a conically or cylindrically curved surface and a spherically curved surface, respectively, the piece of paper wound on the former surface does not wrinkle while the other piece of paper wound on the latter surface wrinkles. For example, even if the wafer 2 is 200 mm in diameter and is deformed by about several millimeters at its peripheral edge relative to its center at the time of the curving and holding of the wafer on the wafer holding bottom 1c of the wafer rest 1b, the quality of the ion-implanted wafer is not affected by the deformation. The wafer holding surface 1c of each wafer rest 1b of the wafer holding disk 1 of an ion implanter provided in accordance with the present invention is a conically curved surface on which a wafer 2 is pushed by centrifugal force due to the rotation of the disk so that the beam-irradiated surface of the wafer 2 is conically curved to correspond to the wafer holding surface 1c of the wafer rest 1b and the inner surface of the peripheral portion of the disk. For that reason, an ion beam 3 is irradiated upon the surface of the wafer 2 perpendicularly to the entire surface, namely, the angle of the implantation of ions into the surface does not deviate. This results in enhancing the accuracy of the implantation of the ions into the wafer to heighten the uniformity of the quality of the wafer. The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiment was chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.

041621913

claims

1. In a steam generator for use in a pressurized water nuclear power plant in which a turbine generator is driven by the steam output of said steam generator to provide electrical power therefrom, wherein said steam generator comprises a vertically extending hollow outer housing having an upper housing portion and a lower housing portion, with said upper housing portion having a steam outlet therein communicable with the turbine generator for providing steam generated within said steam generator to said turbine generator and a moisture separator means within the interior thereof in communication with said steam outlet for drying the generated steam provided to said steam outlet, and with said lower housing portion having heat exchange fluid and feedwater inlets and a vertically extending tube bundle within the interior thereof in flow through communication with said heat exchange fluid inlet for enabling heat exchange fluid provided through said inlet therefor to flow through said tube bundle for providing said generated steam from feedwater provided through said inlet therefor, said tube bundle having a tube sheet at one end thereof for supporting said tube bundle with the tubes comprising said tube bundle extending through said tube sheet in said flow through communication with said heat exchange fluid inlet; the improvement comprising a base module, a tube bundle module removably mountable on said base module in sealing relationship therewith, and an uppermost dryer module removably mountable on said tube bundle module in sealing relationship therewith for providing a vertically assemblable modular structure for said steam generator, said vertically assembled base module and tube bundle module comprising said lower housing portion, and said dryer module comprising said upper housing portion, said dryer module having said steam outlet at one end thereof and a closure flange at the other end thereof and having said moisture separator means within the interior thereof, said tube bundle module having a closure means at the upper end thereof and a closure flange at the lower end thereof and containing said tube bundle within the interior thereof with said tube sheet comprising said lower end closure flange, said dryer module closure flange and said tube bundle module upper closure means effectuating said sealing relationship between said tube bundle module and said dryer module, said base module uppermost portion comprising an outer shell having an arcuately tapered interior wall forming an arcuate lip portion with said base module having said heat exchange fluid inlet therein, said tube bundle in said vertically assembled tube bundle module being in said flow through communication with said heat exchange fluid inlet, the exterior surface of said tube sheet closure flange being arcuately tapered complementary to said base module outer shell interior wall arcuately tapered portion and removably insertable therein in self-supporting bearing relationship against said lip portion for effectuating said sealing relationship between said tube bundle module and said base module essentially as a result of the associated weight of said vertically assembled dryer module and said tube bundle module bearing on said tube sheet closure flange and being supported on said base module while simultaneously facilitating closure by said tube sheet closure flange, whereby ready access to and removal of said tube bundle module in situ from said nuclear power plant steam generator is facilitated. 2. A modular nuclear power plant steam generator in accordance with claim 1 wherein said entire associated weight of said vertically assembled dryer and tube bundle modules is supported on said base module. 3. A modular nuclear power plant steam generator in accordance with claim 1 wherein said tube bundle module contains said feedwater inlet therein. 4. A modular nuclear power plant steam generator in accordance with claim 1 wherein said dryer module closure flange comprises a flange having an arcuately tapered exterior surface and said tube bundle module comprises an outer shell with said upper end closure means comprising an arcuately tapered interior wall in said outer shell, said dryer module flange tapered exterior surface being arcuately tapered complementary to said tube bundle module outer shell arcuately tapered interior wall and removably insertable therein in self-supporting bearing relationship against said arcuately tapered interior wall for effectuating said sealing relationship between said dryer module and said tube bundle module essentially as a result of the associated weight of said vertically assembled dryer module bearing on said dryer module closure flange and being supported on said tube bundle module while simultaneously facilitating closure by said dryer module closure flange. 5. A modular nuclear power plant steam generator in accordance with claim 4 further comprising locking means for removably locking said vertically assembled dryer module to said vertically assembled tube bundle module and said vertically assembled tube bundle module to said base module for removably maintaining said modules in vertically assembled relation. 6. A modular nuclear power plant steam generator in accordance with claim 5 wherein said removable locking means comprises vertically removable bolting means. 7. A modular nuclear power plant steam generator in accordance with claim 1 further comprising locking means for removably locking said vertically assembled dryer module to said vertically assembled tube bundle module and said vertically assembled tube bundle module to said base module for removably maintaining said modules in vertically assembled relation. 8. A modular nuclear power plant steam generator in accordance with claim 7 wherein said removable locking means comprises vertically removable bolting means.

summary

039492311

abstract

A cylindrically shaped coil of resistance wire constitutes a source of infrared radiation which is located within a reflector comprised of a curved reflector section having a reflecting surface shaped to resemble an axially bisected rotationally symmetrical paraboloid, and a cylindrical reflector section which extends from an open side of the curved reflector section. The focal points of the reflecting surface are located on a circle which coincides with the outer circumference of the cylindrically shaped coil.

050892134

description

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention was made based on the study of the techniques disclosed in JP-A-57-53688 and JP-A-60-207095. In the eddy current sensor disclosed in JP-A-57-53688, a detection accuracy of the sensor is lowered when a groove narrower than a diameter of the eddy current sensor or a hole having a narrower diameter than the diameter of the eddy current sensor is to be detected. Characters of 8 mm square size are engraved in a handle of a fuel assembly. A width of those curved characters is as narrow as approximately 1.6 mm. Accordingly, the detection accuracy of the nuclear fuel identification number by the eddy current sensor is low. Since the diameter of the eddy current sensor is usually approximately 5-10 mm, the reduction of the detection accuracy is inevitable. In the ultrasonic wave sensor disclosed in JP-A-60-207095, a signal processing time for detecting the nuclear fuel identification number is long and it is difficult to apply the sensor to a number of fuel assemblies in a fuel storage pool, which require a short response time. This is also true in a case where an eddy current sensor having a long signal processing time is used. JP-A-57-110994 is similar to JP-A-60-207095. The present invention is intended to solve those problems. One embodiment of the nuclear fuel identification code reader of the present invention is now explained with reference to FIGS. 1, 2 and 3. The nuclear fuel identification code reader of the present embodiment comprises a sensor handling unit 1, an ITV camera 5, an ultrasonic wave probe 9, an ultrasonic wave probe scanner 10, a nuclear fuel handling control unit 22, a nuclear fuel identification code monitor 28 and a nuclear fuel identification code processing unit 43. The sensor handling unit 1 utilizes a portion of a nuclear fuel handling unit 51. The nuclear fuel handling unit 51 is used to move a used fuel assembly 66 in a fuel storage pool 63. The used fuel assembly 66 is taken out of a core of a nuclear reactor and loaded and stored in a fuel rack 65 arranged in the fuel storage pool 63. The fuel storage pool 63 is filled with water 64. The fuel rack 65 is arranged under a water level of the water 64. The nuclear fuel handling unit 51 is constructed to cross the fuel storage pool 63. The nuclear fuel handling unit 51 includes a movable truck 52, a laterally movable truck 53, a grapple 54, a clamp 55 and a hoist 56. The movable truck 52 is driven by a drive motor 58 on a pair of rails 57 arranged on both sides of the fuel storage pool 63. The laterally movable truck 53 has the grapple 54, the clamp 55 and the hoist 56 and is driven by a drive motor 60 on a pair of rails 59 arranged on the movable truck 52. The grapple 54 is raised and fallen by the hoist 56 and a drive motor 62. The grapple 54 is rotated by a drive motor 61 to allow adjustment of an angle of the clamp 55 in a horizontal plane. The drive motor 61 is mounted on the laterally movable truck 53. The grapple 54 is constructed by several linked expandable pipes. The lamp 55 is mounted at the bottom end of the grapple 54. A direction of movement of the movable truck 52 is represented by X, a direction of movement of the laterally movable truck 53 is Y, the elevation of the grapple 54 is represented by Z.sub.1 and the rotation is represented by .theta..sub.1. Position signals representing the displacements X, Y, Z.sub.1 and .theta..sub.1 are detected by synchronous signal generators (not shown) mounted on the respective drive shafts of the fuel handling unit 51. The sensor handling unit 1 has a hoist 2, a drive motor 3 and a grapple 4. The hoist 2, the drive motor 3 and the grapple 4 are mounted on the movable truck 53. A drive motor (not shown) which corresponds to the drive motor 61 and serves to rotate the grapple is mounted on the laterally movable truck 53. The grapple 4 is also constructed by several linked expandable pipes. The grapple 4 is moved up and down by the hoist and the drive motor 3. The elevation of the grapple 4 is represented by Z.sub.2 and the rotation is represented by .theta..sub.2. Position signals representing the displacements Z.sub.2 and .theta..sub.2 are detected by synchronous signal generators (not shown) mounted on the respective drive shafts of the sensor handling unit 1. A mount table 6 is arranged at the bottom end of the grapple 4. The ITV camera 5 is mounted on the mount table 6. Four downwardly extending frames 7 are fixed to the mount table 6 by screws. An illumination device 8 is arranged at the bottom ends of the frames 7. The ultrasonic wave probe scanner 10 is mounted on the mounted table 6 by an arm 11. A detailed structure of the ultrasonic wave probe scanner 10 is explained below. A drive motor 13 is mounted at a top of a bottom-opened box 12. An upwardly extending rotary screw 14 linked to a rotation shaft of the drive motor 13 meshes with a nut (not shown) mounted on a support member 16 which is mounted on the arm 11. A pair of guide members 15A and 15B which hold the rotary screw 14 therebetween are mounted on the drive motor 13. The guide members 15A and 15B extend through the support member 16 so that they are vertically movable. Another drive motor 17 is mounted on a side of the box 12 which faces the ITV camera 5. A rotary screw 18 horizontally arranged in the box 12 has one end thereof linked to a rotation shaft of the drive motor 17 and the other end thereof supported by a bearing (not shown) mounted on the side of the box 12. A probe holding table 19 engages with the rotary screw 18. Two ultrasonic wave probes 9 are mounted on the probe holding table 19. They are arranged to traverse the rotary screw 18. A pair of fixing guides 21 is arranged in the box 12. An encoder 20 measures the displacement of the ultrasonic wave probe 9 along the axis of the rotating screw 18. The ITV camera 5 and the ultrasonic wave probe 9 constitute a nuclear fuel identification code detection means. The nuclear fuel handling control unit 22 comprises input/output means 23A and 23B, a nuclear fuel handling unit control means 24, a nuclear fuel monitor unit control means 25, a memory 26 and a console panel 27. The input/output means 23A supplies control signals to the drive motors 58, 60, 61 and 62 and receives the position signals representing the displacements X, Y, Z.sub.1 and .theta..sub.1 from the corresponding synchronous signal generators (not shown). The input/output means 23B supplies control signals to the drive motors 3, 58 and 60 and the drive motor (not shown) which drives the grapple 4, and receives the position signals representing the displacements X, Y, Z.sub.2 and .theta..sub.2 from the corresponding synchronous signal generators (not shown). The input/output means 23A inputs and outputs the signals related to the nuclear fuel handling unit control means 24, and the input/output means 23B inputs and outputs the signals related to the nuclear fuel monitor unit control means 25. The nuclear fuel handling unit control means 24 and the nuclear fuel monitor control means 25 are included in a computer 48. The nuclear fuel identification code monitor 28 has a video signal digitizer 29 and a signal processing microprocessor 30. The microprocessor 30 has a memory 33, an image processing means 31 and a nuclear fuel number identification/discrimination means 32. The video signal digitizer 29 is a kind of A/D converter which converts a video signal (analog signal) sent from the ITV camera 5 to a digital signal. The video signal digitizer 29. The image signal processing means 31 and the fuel number identification/discrimination means 32 are coupled to the input/output means 23B. The nuclear fuel identification code monitor 28 thus constructed identifies the nuclear fuel identification code based on the video signal derived from the ITV camera 5. The nuclear fuel identification code monitor 34 comprises a pulse generation means 35, a signal receive means 36, a probe scanner control means 38 which is constructed by a microprocessor, and a signal processing microprocessor 39. The microprocessor 39 has an ultrasonic wave signal processing means 40, a nuclear fuel number identification means 41, and a memory 42. The pulse generation means 35 is connected to the ultrasonic wave probe 9 and the probe scanner control means 38. The signal receive means 36 is connected to the ultrasonic wave probe 9 and the ultrasonic wave signal processing means 40. The ultrasonic wave signal processing means 40 is coupled to the encoder 20. The probe scanner control means 38 is connected to the drive motors 13 and 17, the encoder 20 and a limit switch 37, and further to the input/output means 23B. The nuclear fuel identification code monitor 34 thus constructed identifies the nuclear fuel identification code based on the reflected wave of the ultrasonic wave derived from the ultrasonic wave probe 9. The nuclear fuel identification code processing unit 43 comprises a fuel number processing means 44 and a memory 45. A numeral 46 denotes a display and a numeral 47 denotes a printer. The display 46 may be mounted on the console panel 27. A structure of the fuel assembly 66 loaded in the fuel rack 65 is explained with reference to FIG. 4. The fuel assembly 66 loaded in the fuel rack 65 is an assembly of used fuel which is taken out of a center of a boiled-water type nuclear reactor. The fuel assembly 66 comprises an upper tie plate 67, a lower tie plate 69, a plurality of fuel rods 70 and a plurality of fuel spacers 71. The top and bottom ends of the fuel rods 70 are held by the upper tie plate 67 and the lower tie plate 69. The fuel spacers 71 are arranged axially of the fuel assembly 66 to keep a predetermined spacing between the fuel rods 70. A channel box 72 mounted on the upper tie plate 67 surrounds a bundle of fuel rods 70 supported by the fuel spacers 71. The upper tie plate 67 has a handle 72 arranged at the top thereof. A nuclear fuel identification number 74 is marked on the top 73 of the handle 72. As shown in FIGS. 5 and 6, the nuclear fuel identification number 74 includes a nuclear fuel identification number 74A coded by recesses 75 having circular cross-sections, and a nuclear fuel identification number 74B which is a combination of alphanumeric characters. Those two types of nuclear fuel identification numbers are marked in parallel on the top 73 of the handle 72. The nuclear fuel identification number 74B can be recognized by a human when he/she looks it but the nuclear fuel identification number 74A cannot be recognized by the human by just looking it. Both of the nuclear fuel identification numbers 74A and 74B are marked by engraving on the top 73 of the handle 72. The nuclear fuel identification number 74A is a combination of the recesses 75 which corresponds to the nuclear fuel identification number 74B. The cross-section of the recess 75 need not necessary be circular but it may be triangular, square or rectangular, or even oval. In the nuclear fuel identification number 74A, each area sectioned by broken lines 76 corresponds to one character. In FIG. 5, the nuclear fuel identification number 74A represents "2FABC". Each coded symbol of the nuclear fuel identification number 74A is represented by the combination of up to six recesses 75 (two lines of three recesses). Each symbol of the nuclear fuel identification number 74A is a digital signal represented by the presence or absence of the recess 75. FIG. 7 shows a correspondence between the digitized symbols representing the nuclear fuel identification number 74A and the alphanumeric characters (0-9, A-Z). In FIG. 7, the black dot represents the presence of the recess 75 and a white dot represents the absence of the recess 75. It is possible to digitize 36 alphanumeric characters by arranging six recesses 75 (two lines of three recesses) as shown in FIG. 7. A plurality of digital symbols shown in FIG. 7 may be arranged on the top 73 in combination with the characters of the nuclear fuel identification number 74B. Assuming that a diameter of the recess 75 is approximately 1 mm and a spacing W.sub.1 between the recesses 75 in one digital symbol is at least approximately 1 mm, the presence or absence of the recess 75 can be detected by the ultrasonic wave. Since a spacing W.sub.2 between lines of recesses 75 is approximately 3 mm, the nuclear fuel identification number 74A and the nuclear fuel identification number 74B can be marked in parallel on the top 73 having a width of approximately 12 mm. A recess 76 which is used as a reference to read the nuclear fuel identification number 74A is formed on the top 73 of the handle 72. The recess 76 is orthogonal to the side of the handle 72 and it is positioned on the left of the first digital symbol of the nuclear fuel identification number 74A. Without the recess 76, the nuclear fuel identification code monitor 34 cannot specify the nuclear fuel identification number 74A detected by the ultrasonic wave. In the example shown in FIG. 5, the nuclear fuel identification number 74A may be read as either "2FABC" or "CBAF2". If it is determined that the nuclear fuel identification number 74A is to be read from the end adjacent to the recess 76, the number 74 is read as "2FABC". A width W.sub.3 of the recess 76 is either wider or narrower than a width W.sub.4 (diameter) of the recess 75 so that the nuclear fuel identification code monitor 34 can easily discriminate the recess 75 of the digital symbol and the recess 76 of the read reference. The recess 76 need not be linear but it may be circular, triangular or square in cross-section so long as it is positioned on the left of the lines of recesses 75. The fuel assembly 66 having the nuclear fuel identification numbers 74A and 74B marked in parallel on the top 73 of the handle 72 is loaded into the center of the boiled-water type nuclear reactor after the used fuel assembly 66 has been removed from the center of the reactor. The operation of the nuclear fuel identification code reader of the present invention is non explained. An operator specifies, through the console panel 27, the operation of the nuclear fuel handling or the operation of the detector for the nuclear fuel identification code. The specified operation signal is supplied to the computer 48. If the former operation is specified, the nuclear fuel handling unit control means 24 is activated, and if the latter operation is specified, the nuclear fuel monitor control means 25 is activated. It is now assumed that the specified operation is the operation of nuclear fuel handling. Before the function of the nuclear fuel handling unit control means 24 is explained, the operation of the nuclear fuel handling unit 51 in the nuclear fuel handling operation is briefly explained. A plurality of used free assemblies 66 are carried to a predetermined position in the fuel storage pool 63 from the top thereof while they are loaded in a container. Then, the movable truck 52 and the laterally movable truck 53 are driven to move the clamp 55 above the container. As the grapple 54 descends, the clamp 55 is lowered to the position of the handle 72 of the fuel assembly 66 in the container. After the clamp 55 has held the handle 72, the grapple 54 is raised. When the bottom end of the fuel assembly 66 reaches a level which is a predetermined distance above the top end of the fuel rack 65, the elevation of the grapple 54 is stopped. The movable truck 52 and the laterally movable truck 53 are again driven to move the fuel assembly 16 to a level which is a predetermined distance (specified by the operator through the console panel 27) above the fuel rack 65. When it reaches that level, the grapple 54 is lowered to load the fuel assembly 66 to a predetermined position in the fuel rack 65. The above movement is referred as a movement 1. When the fuel assembly is taken out of the fuel storage pool 63 for fuel processing, the opposite movement (movement 2) is carried out. Namely, the fuel assembly 66 taken out of the fuel rack 65 is loaded into the container. The clamp 55 may be moved, while it does not clamp the fuel assembly 66, from the position of the fuel rack 65 to other position (movement 3), from the position of the fuel rack 65 to the position of the container (movement 4), or from the position of the container to the position of the fuel rack 65 (movement 5). The memory 26 stores data relating to the loading status of the fuel assembly 66 at the respective positions (X-Y ID coordinate) of the fuel rack 65. The memory 26 stores "0" for the position at which the fuel assembly 66 is not loaded, and "1" for the position at which the fuel assembly 66 is loaded. The ID coordinate is not represented by absolute distances on X and Y axises but it is represented by the code applied to the fuel assembly load position. The position signals representing the displacements X, Y, Z.sub.1 and .theta..sub.1 measured by the synchronous signal generators are converted to the digital signals by the input/output means 23A and they are supplied to the nuclear fuel handling unit control means 24 of the computer 48. A limit switch (not shown) mounted on the nuclear fuel handling unit 51 detects when the grapple 55 reaches a grapple upper limit level A and a mount level B of the fuel assembly (in the fuel rack 65 and the container). The detection signal is supplied to the computer 48. The nuclear fuel handling unit control means 24 uses those signals to control and monitor the position of the nuclear fuel handling unit 51. When the used fuel assembly 66 is to be moved in the fuel storage pool 63, the operator specifies N target positions (X-Y ID coordinate) necessary for the fuel handling unit 51 to move the fuel assembly 66, through the console panel 27. The P.sub.l or P which is shown in JP-B-58-21238, column 6, lines 8-10 is also specified through the console panel 27. The nuclear fuel handling unit control means 24 discriminates in the manner described and shown in JP-B-58-21238, column 7, line 26 to column 8, line 11 and FIGS. 3 and 4. That is, the load status of the fuel assembly 66 at the target position, the correctness of the data (P.sub.l or P) specified by the operator and the open/close status of the clamp 55 are checked, and if the check result is normal, the control signal for the corresponding movement (one of the movements 1-5) is supplied to the nuclear fuel handling unit 51 to control the corresponding movement. If the check result is not normal, the nuclear fuel handling unit control means 24 inhibits the start of the nuclear fuel handling unit 51. When the fuel assembly 66 is moved by the nuclear fuel handling unit 51, the data on the load status of the fuel assembly 66 at the respective positions of the fuel rack 65, which is stored in the memory 26, is updated as the movement proceeds. When the operator specifies the operation of the detector for the nuclear fuel identification code, the nuclear fuel monitor unit control means 25 moves the sensor handling unit 1 in accordance with the process (steps 77A-77M) of FIG. 8. This is explained in detail below. When a monitor operation signal is supplied from the console panel 27 (step 77A), a step 77B is carried out. The position signals representing the displacements X, Y, Z.sub.2 and .theta..sub.1 measured by the respective synchronous signal generators are converted to the digital signals by the input/output means 23B and they are supplied to the nuclear fuel monitor control means 25 of the computer 48. Levels L.sub.1 and L.sub.2 are detected by the limit switch (not shown) mounted on the sensor handling unit 1. Those detection signals are supplied to the nuclear fuel monitor control means 25, which uses those signals to control and monitor the position of the sensor handling unit 1. The level L.sub.1 (FIG. 2) is set at the bottom end of the ITV camera 5 when the nuclear fuel identification number is monitored so that the illumination device 8 does not contact to the top 73 of the handle 72 of the fuel assembly 66 in the fuel rack 65. The level L.sub.2 is set substantially above the level L.sub.1, at a position where the ITV camera 5 is positioned when the nuclear fuel identification number is not detected. The sequence of the fuel assemblies 66 for which the nuclear fuel identification numbers are detected is predetermined and stored in the memory 26. The sequence is shown in FIG. 1 by a chain line 49 starting at a point K.sub.1. It is in the order of the positions K.sub.i (i=1, 2, . . . n.sub.1) shown in the X-Y ID coordinate for the fuel rack 65. In a step 77B, the grapple 4 is lowered, and when the bottom end of the ITV camera 5 reaches the level L.sub.1, the descend of the grapple 4 is stopped. Then, i is set to "1" (step 77C). Whether i=n.sub.1 or not is checked (step 77D). If it is, a step 77E is carried out, and if it is not, a step 77M is carried out. In a step 77F following to the step 77E, the movable truck 52 and the laterally movable truck 53 are driven so that the ITV camera 5 reaches on the fuel assembly 66 which is at the position K.sub.i for which the nuclear fuel identification number is to be detected. When i=1, the ITV camera 5 is set to the start position K.sub.1. When the ITV camera 5 reaches the position K.sub.i, a start of detection signal S.sub.1 for the nuclear fuel identification number 74B by the ITV camera 5 is produced (step 77G). The start of detection signal S.sub.1 is supplied to the nuclear fuel identification code monitor 28, the ITV camera 5 and the illumination device 8. When the nuclear fuel identification code monitor 28 receives the start of detection signal S.sub.1, it starts to receive and process the video signal produced by the ITV camera 5. Upon receipt of the signal S.sub.1, the ITV camera 5 starts to pick up the image and the illumination device 8 is turned on. The image pick-up operation of the ITV camera 5 and the turn-on of the illumination device 8 may be started by the input of the signal S.sub.1 at the position K.sub.1 and continued until the image pick-up at the position K.sub.n is completed, instead of repetitively turning on and off at each position. In a step 77H, a discrimination signal J is received. The discrimination signal J is produced by the nuclear number identification/discrimination means 32 when the processing of the video signal relating to one fuel assembly 66 is completed in the nuclear fuel identification code monitor 28. The fuel member identification/discrimination means 32 produces a "0" discrimination signal J when all characters of the fuel identification number 74B detected by the ITV camera 5 are recognized by the image processing, and produces a "1" discrimination signal J when all characters are not recognized. After the step 77H, whether the discrimination signal J is "1" or "0" is checked (step 77I). If the discrimination signal J is "0", a step 77D is carried out, and if the signal J is "1", a step 77J is carried out. In the step 77J, the laterally movable truck 53 (or the movable truck 52) is driven to move the ultrasonic wave probe 9 on the position K.sub.i. When the ultrasonic wave probe 9 reaches the position K.sub.i, a start of detection signal S.sub.2 for the nuclear fuel identification number 74A by the ultrasonic wave probe 9 is produced (step 77K). The start of detection signal S.sub.2 is supplied to the probe scanner control means 38 of the nuclear fuel identification code monitor 34 to effect the detection of the nuclear fuel identification number 74A by the ultrasonic wave probe 9 and the recognition of the nuclear fuel identification number 74A by the nuclear fuel identification code monitor 34. The probe scanner control means 38 produces an end of ultrasonic wave scan signal E.sub.1 when the scan of the ultrasonic wave probe 9 to detect the fuel identification number 74A is over. When the nuclear fuel monitor control unit 25 receives the end signal E.sub.1 (step 77L), it carries out the decision of the step 77D. If the decision in the step 77D is YES, the grapple 4 is elevated to elevate the ITV camera 5 to the level L.sub.2 (step 77M). In this manner, the nuclear fuel identification numbers of all fuel assemblies 66 in the fuel storage pool 63 are monitored. The nuclear fuel monitor control means 25 drives the ITV camera 5 which is the optical sensor for the nuclear fuel identification number onto the fuel assembly 66 under consideration, and when the fuel identification number 74B detected by the ITV camera 5 is hard to be recognized, the ultrasonic wave probe 9 which is the ultrasonic wave sensor is driven onto the fuel assembly 66 to detect the fuel identification member 74A. The operation of the nuclear fuel identification code monitor 28 when it receives the start of detection signal S.sub.1 produced by the nuclear fuel monitor unit control means 25 is explained. When the start of detection signal S.sub.1 is received, the video signal digitizer 29 starts the A/D conversion of the video signal for the top 73 of the handle 72 picked up by the ITV camera 5. The image signal converted to the digital signal by the video signal digitizer 29 is supplied to the memory 33 in 1/30 second and stored therein. The image processing means 31 carries out the process shown in FIG. 9. Upon receipt of the start of detection signal S.sub.1, the image processing means 31 receives the video signal stored in the memory 33 (step 78A). It extracts the image signal of the nuclear fuel identification number 74B marked on the fuel assembly 66 under consideration, from the input image signal (step 78B). The extracted image signal is processed for noise elimination (step 78C) and contrast enhancement (step 78D). Then, the image signal is binarized to generate character patterns for all characters (n.sub.2, n.sub.2 =5 in the present embodiment) of the detected nuclear fuel identification number 74B (step 78E). Those character patterns are generated as two-dimension character patterns P.sub.jk (l) (j=1- M, k=1- N, l=1- n.sub.2) having M.times.N picture elements. The n.sub.2 generated character patterns are supplied to the fuel number identification/discrimination means 32 in the sequence of the characters of the nuclear fuel identification number 74B (step 78F). When the nuclear fuel number identification/discrimination means 32 receives the character patterns of the characters of the nuclear fuel identification number 74B, it carries out a process comprising steps 79A-79K shown in FIG. 10. The nuclear fuel number identification/discrimination means 32 receives the n.sub.2 character patterns P.sub.jk (l) (step 79A) and carries out the steps 79B and 79C to read n.sub.3 standard character patterns Q.sub.jk (m) from the memory 33. In the present embodiment, 36 standard character patterns Q.sub.jk (m) (m=1-n.sub.3) including 0-9 and A-Z shown in FIG. 11 are stored in the memory 33, and n.sub.3 =36. Those standard character patterns correspond to the engraved characters of the nuclear fuel identification number 74B. In a step 79E, a similarity I(m) between the character patterns P.sub.jk (l) and the n.sub.3 standard character patterns Q.sub.jk (m) are calculated in accordance with a formula (1). ##EQU1## The similarity I(m) calculated in accordance with the formula (1) is 1.0 when the character patterns P.sub.jk (l) and the standard character patterns Q.sub.jk (m) fully match. It does not exceed 1.0. In a step 79F, whether a maximum one (max I(m)) of the I(m) calculated for the character patterns P.sub.jk (l) is larger than a predetermined threshold S or not. When max I(m) is close to 1.0, it indicates that the ITV camera 5 has detected the characters of the nuclear fuel identification number 74 to a sufficient extent to permit the recognition. When max I(m) is around 0.6, it means that the characters of the nuclear fuel identification number 74B cannot be sufficiently detected because of the deposition of soft clad. The threshold S is to be determined by taking the above into account. When max I(m) is smaller than the threshold S (the decision in the step 79F is NO), the "1" discrimination signal J is supplied to the input/output means 23B of the nuclear fuel handling unit control means 22 in order to detect the nuclear fuel identification number 74A by the ultrasonic probe 9 (step 79K). In the step 79F, the necessity of the detection of the nuclear fuel identification number 74A by the ultrasonic wave sensor, that is, the necessity of the movement of the ultrasonic wave probe 9 onto the fuel assembly 66 under consideration is checked. If the decision in the step 79F is YES, the characters of the character patterns P.sub.jk (l) are recognized as the characters corresponding to the standard character patterns Q.sub.jk (m) having the similarity max I(m) (step 79G). If the decision in the step 79H is NO, the steps 79C et seq are repeated. If the decision is YES, a step 79I (output of the "0" discrimination signal J) is carried out. The "0" discrimination signal J is also supplied to the input/output means 23B. Finally, the n characters (2FABC) recognized in the step 79J are supplied to the nuclear fuel number processing means 44 of the nuclear fuel identification code processing unit 43. The character recognition technique carried out by the nuclear fuel number identification/discrimination means 32 is a two-dimension template matching method. The operation and process of the nuclear fuel identification code monitor 34 when the nuclear fuel number identification/discrimination means 32 produces the "1" discrimination signal J in the step 79K and the nuclear fuel monitor control means 25 produces the start of detection signal S.sub.2 are now explained. The process of the probe scan control means 38 is shown in FIG. 12. When it receives the start of detection signal S.sub.2 (step 80A), it sends a drive signal to the drive motor 13 (step 80B). As the drive motor 13 rotates, the rotary screw 14 is rotated and the box 12 which accommodates the ultrasonic wave probe 9 is moved down. When the start of detection signal S.sub.2 is generated, the ultrasonic wave probe scanner 10 has already been located above the fuel assembly 66 under consideration. As a result, the handle 72 of the fuel assembly 66 is inserted between the pair of fixing guides 21 in the descending box 12. When the limit switch 37 contacts to the top 73 of the handle 72, it produces an activation signal. When the probe scanner control means 38 receives the activation signal, it stops the rotation of the drive motor 13. In a step 80D, a start of ultrasonic wave scan signal S.sub.3 is generated. The start signal S.sub.3 is supplied to the pulse generation means 35 and the ultrasonic signal processing means 40. When the pulse generation means 35 receives the start signal S.sub.3, it produces an electrical pulse to cause the ultrasonic wave probe 9 to generate an ultrasonic wave. The ultrasonic wave generated by the ultrasonic wave probe 9 is irradiated to the top 73 of the handle 72. After the step 80D, a drive signal is supplied to the drive motor 17 (step 80E). As the drive motor 17 rotates, the rotary screw 18 is rotated and the probe support table 19 which accommodates the ultrasonic probe 9 is moved from the right to the left in FIG. 2. Since the fixing guides 21 contact to the top 73 of the handle 72, the ultrasonic wave probe 9 is moved laterally while the distance to the top 73 is kept constant. One of the pair of ultrasonic wave probe 9 mounted on the probe support table 19 moves on an extended line of an arrow R.sub.1 (FIG. 5) and the other moves on an extended line of an arrow R.sub.2 which is parallel to the arrow R.sub.1. In the present embodiment, the pair of ultrasonic wave probes 9 can substantially simultaneously detect the two lines of recesses 75 of the nuclear fuel identification number 74A. When the ultrasonic wave probe 9 reaches the end point of scan, it is detected by the encoder 20. The detection signal (position signal of the ultrasonic wave probe 9) of the encoder 20 is supplied to the probe scanner control means 38. When the ultrasonic wave probe 9 reaches the end point of scan, the probe scanner control means 38 stops the drive motor 17 and produces an end of ultrasonic wave scan signal E.sub.1 (step 80E). After the step 80F, it drives the drive motor 13 to elevate the ultrasonic wave probe 9 to a predetermined position (step 80G). Then, the detection of the nuclear fuel identification number 74A by the ultrasonic wave probe 9 is terminated. As described above, the ultrasonic wave probe 9 irradiates the ultrasonic wave to the top 73 of the handle 72 and receives the reflected ultrasonic wave from the top 73. A relationship between a horizontal position of the ultrasonic wave probe 9 driven by the drive motor 17 and the reflected ultrasonic wave is shown in FIG. 13. The reflected wave in FIG. 13 is detected by the ultrasonic probe 9 which is moved on the extended line of the arrow R.sub.1. The ultrasonic wave generated by the ultrasonic wave probe 9 is mostly reflected by the area of the top 73 which has no recess 75, and the reflected ultrasonic wave is received by the ultrasonic wave probe. However, since the bottom of the recess 75 is arcuate as shown in FIG. 6, the ultrasonic wave is scattered in the area of recess 75 and little reflected wave reaches the ultrasonic wave probe 9. Accordingly, the amplitude of the reflected wave is zero in the area of recess 75. Clad may deposit on the top 73 of the handle 72 of the fuel assembly 66 which the fuel assembly 66 is loaded in the center of the nuclear reactor and a portion of the recesses 75 may be covered by the clad. Even if the recesses 75 on the top 73 of the handle 72 of the fuel assembly 66 loaded in the fuel rack 65 is covered by the clad, it is possible to detect the recesses 75 by the ultrasonic wave. This is due to the fact that there is no substantial difference between acoustic impedances of water and water-containing clad (primary constituent is ferric oxide). The reflected wave signal detected by the ultrasonic wave probe 9 is supplied to the signal receive means 36. In the reflected wave signal of FIG. 13, a zero reflected wave output area having a width W.sub.3 corresponds to the recess 76 which is the read reference recess. Other zero reflected wave output areas correspond to the recesses 75. As a method for detecting the digitized recesses 65 of the nuclear fuel identification number 74A, one of the following methods may be adopted: 1) two-dimensionally scanning one ultrasonic wave probe, 2) linearly scanning a plurality of parallelly arranged ultrasonic wave probes, and 3) two-dimensionally scanning the ultrasonic wave beam by electronically switching ultrasonic wave probes by using an array sensor having a plurality of ultrasonic wave probes arranged two-dimensionally to cover the entire area of the nuclear fuel identification number 74A. The present embodiment adopts the method 2). The signal receive means 36 converts the input reflected wave signal to "1" and "0" pulse signals. The zero reflected wave output is converted to "1" and non-zero reflected wave output is converted to "0". The output signal (pulse signal) of the signal receive means 36 and the position signal of the ultrasonic wave probe 9 detected by the encoder 20 are supplied to the ultrasonic wave signal processing means 40, which carries out a process comprising steps 81A-81E shown in FIG. 14. The pulse signal corresponding to the read reference recess 76 detected, and the position of the ultrasonic wave probe 9 where the pulse signal was generated are determined based on the input signals supplied in the step 81A (step 81B). The pulse signal corresponding to the recess 76 can be readily detected because it is narrower (in the area of "1") than the pulse signals corresponding to the recesses 75. The presence or absence of the recesses 75 is detected and the positions of the recesses 75 are determined relative to the recess 76 (step 81C). The pulse signal corresponding to the recess 75, that is, the pulse signal having the pulse width W.sub.4 is detected and the position of the ultrasonic wave probe 9 corresponding to the pulse signal of the pulse width W.sub.4 is determined. Based on the data of the position of the recess 75 determined in the step 81C, the presence or absence of the recess 75 at six predetermined positions is determined in five areas sectioned by the broken lines 76 of the nuclear fuel identification number 74A of FIG. 5, and signals "0" or "1" are assigned to the six predetermined positions, with each predetermined position being a unit (step 81D). Thus, the digital pattern signals for the units, which are "1" if the recesses 75 are present and "0" if the recesses 75 are not present, are produced. A unit number of digital pattern signals corresponding to the number of characters (n.sub.2) of the nuclear fuel identification number 74B are supplied to the fuel number recognition means 41 in sequence starting from the recess 76 (step 81E). The fuel number recognition means 41 carries out a process comprising steps 82A-82C shown in FIG. 15. The memory 42 stores the correspondence between the standard digital patterns which represent the presence or absence of the recesses 75 shown in FIG. 7 and the characters (alphanumeric). The fuel number recognition means 41 reads the standard digital patterns corresponding to the digital patterns for the respective units received in the step 82A, from the memory 42, and recognizes the characters corresponding to the standard digital patterns as the characters for the digital pattern signals (step 82B). The fuel number recognition means 41 supplies the n.sub.2 characters (2FABC) recognized for the fuel identification number 74A to the fuel number processing means 44 (step 82C). Thus, the detection of the nuclear fuel identification number marked on the handle 72 of the fuel assembly 66 by the nuclear fuel identification code monitor 28 or 34, and the recognition of the detected nuclear fuel identification number as characters are terminated. The fuel number processing means 44 receives the characters of the nuclear fuel identification number recognized by the nuclear fuel identification code monitor 28 or 34, and the X-Y ID coordinates of the positions K.sub.i based on the values X and Y inputted to the nuclear fuel monitor control means 25. The fuel number processing means 44 stores the recognized characters of the nuclear fuel identification number and the X-Y ID coordinates of the positions K.sub.i in an associated manner, and displays them on the display 46 and prints them out by the printer 47. Since the recognized characters of the nuclear fuel identification number and the X-Y ID coordinates are associated, the nuclear fuel identification number of the fuel assembly 66 loaded at the position K.sub.i of the fuel rack 65 in the fuel storage pool 63 can be readily determined. In accordance with the nuclear fuel identification code reader of the present embodiment, the following advantages are offered. Since the nuclear fuel identification number 74B marked by the letters is recognized by the optical sensor and the nuclear fuel identification code monitor 28, the fuel assembly 66 in the fuel storage pool can be identified in a short time. Even if it is difficult to recognize the letters of the nuclear fuel identification number 74B based on the video signal from the optical sensor (due to the deposition of the clad to the handle 72 of the fuel assembly 66 under consideration), it is possible to readily recognize the letters of the nuclear fuel identification number by the ultrasonic wave sensor and the nuclear fuel identification monitor 34. By the combined use of the detection of the primary nuclear fuel identification number by the optical sensor and the detection of the supplementary nuclear fuel identification number by the ultrasonic wave sensor, the nuclear fuel identification numbers marked on all fuel assemblies in the fuel storage pool 63 can be detected in a very short time with an accuracy of essentially 100% (99.99%). By preferentially using the detection by the optical sensor to the fuel assembly 66 and supplementarily using the detection by the ultrasonic wave sensor in case the letters of the nuclear fuel identification number 74B cannot be recognized based on the information derived from the optical sensor, the above advantages, particularly the reduction of the detection time, are remarkable. In the present embodiment, for those of the fuel assemblies 66 stored in the fuel storage pool 63 whose nuclear fuel identification number 74B cannot be recognized by the optical sensor, the detection of the nuclear fuel identification number 74A by the ultrasonic wave sensor is effected. The automatic reading of the nuclear fuel identification number may also be effected. In the present embodiment, since the ultrasonic wave sensor detects the digitized recesses 75 formed on the top 73 of the handle 72 of the fuel assembly 66, the processing time for recognizing the letters can be significantly reduced compared to that required in detecting the letters themselves by the ultrasonic sensor. In the present embodiment, the structure of the ultrasonic wave probe scanner and the structure of the associated nuclear fuel identification code monitor (especially a processing program) can be simplified compared to a case where the letters themselves are detected by the ultrasonic wave sensor. The provision of the read reference recess 76 on the top 73 of the handle 72 facilitates the recognition of the letters of the nuclear fuel identification number 74A based on the reflected ultrasonic wave. Since both the digitized (coded) nuclear fuel identification number 74A and the nuclear fuel identification number 74B in letters are marked on the top 73 of the handle of the fuel assembly 66, the detection by the optical sensor and the detection by the ultrasonic wave sensor are facilitated. The provision of the nuclear fuel identification number 74B also permits visual recognition by a human. Since the sensor handling unit 1 is provided in the nuclear fuel handling unit 51, a portion of the nuclear fuel handling unit 51 can be utilized as the nuclear fuel identification code reader and the entire construction can be very compact. In other words, the fuel assembly may be moved by the nuclear fuel identification code reader. In FIG. 1, separate movable truck and laterally movable truck such as grapple 54 for handling the fuel may be provided, although the construction may be complex. The nuclear fuel handling unit control means 24 may also be assembled in a separate computer. The mounting of the ITV camera 5 and the ultrasonic wave probe scanner 10 on one grapple 4 significantly contributes to the simplification of the structure. Since the drive mechanism (the drive motor 13 and the rotary screw 14) for moving up and down the ultrasonic wave probe 9 is provided separately from the grapple 4, the positioning of the ultrasonic probe 9 above the fuel assembly is facilitated. Since the nuclear fuel identification number 74A including the recesses 65 is marked on the top 73 of the fuel assembly 66, the processing time required for the character recognition based on the reflected ultrasonic wave is essentially same as the processing time required for the character recognition based on the detection of the nuclear fuel identification number 74B by the ITV camera 5. However, the detection of the nuclear fuel identification number 74B by the ITV camera 5 can be continuously effected while the movable truck 52 and the laterally movable truck 53 are driven, but the detection of the nuclear fuel identification number 74A by the ultrasonic sensor should repeat the start and stop of the movement of the movable truck 52 and the laterally movable truck 5 and the start and stop of the scan of the ultrasonic wave probe 9 for each fuel assembly 66. Accordingly, the time required to recognize the nuclear fuel identification numbers of all fuel assemblies is shorter when both the character recognition for the fuel identification number 74B based on the video signal from the optical sensor and the character recognition based on the reflected wave by the ultrasonic wave sensor are used than when the characters of the nuclear fuel identification number 74A are recognized by the ultrasonic wave sensor. Another embodiment of the nuclear fuel identification code reader of the present invention is explained with reference to FIGS. 16 and 17. The like elements to those shown in the embodiment of FIG. 1 are designated by the like numeral. Most elements of the present embodiment are identical to those of the embodiment of FIG. 1. In the present embodiment, the nuclear fuel identification code processing unit 43 in the embodiment of FIG. 1 is replaced by a nuclear fuel identification code compare unit 83. Configuration and operation of the nuclear fuel identification code compare unit 83 are explained below. The nuclear fuel identification code compare unit 83 has a memory 45 and fuel number compare means 84. The fuel number compare means 84 receives the letters of the nuclear fuel identification number recognized by the nuclear fuel identification code monitor 28 or 34, and also receives an X-Y ID coordinate of a position K.sub.i based on the values X and Y inputted to the nuclear fuel monitor control means 25 (step 85A). The memory 45 stores the nuclear fuel identification number (in letters) of the fuel assemblies 66 at each position K.sub.i of the fuel rack in the fuel storage pool 63. Those are previously detected data. The memory 45 also stores data representing the load status of the fuel assembly 66 fetched from the memory 26 by the fuel number compare means 84. This data indicates the presence or absence of the fuel assembly 66 at each position K.sub.i of the fuel rack 65. The fuel number compare means 84 compares the X-Y ID coordinate of the position K.sub.i inputted currently and the letters of the nuclear fuel identification number for the position K.sub.i with the corresponding past data read from the memory 45 (step 85B), and determines the matching (step 85C). The comparison result is stored in the memory 45, displayed on the display 46 and printed out by the printer 47. If the result in the result in the step 85C is non-match, a buzzer is sound to alarm to the operator. In this manner, the present embodiment can attain the same advantages as those of the embodiment of FIG. 1, and it is particularly effective in the recognition of the fuel assembly 66 where the fuel assembly 66 is to be stored in the fuel storage pool 6 for an extended period. By the comparison of the letters of the current nuclear fuel identification number and the past data previously detected, the storage of the fuel assembly 66 having the identical nuclear identification number in the fuel storage pool 63 can be readily checked. Other embodiment of the nuclear fuel identification code reader of the present invention is explained below. As shown in FIG. 18, the present embodiment uses a nuclear fuel identification code monitor 28A in place of the nuclear fuel identification code monitor 28 of FIG. 1. The nuclear fuel identification code monitor 28A comprises, in addition to the elements of the nuclear fuel identification code monitor 28, ITV camera control means 86 which receives a start of detection signal S.sub.1 from the nuclear fuel monitor control means 25. The ITV camera control means 86 generates a start of image pickup trigger signal to the ITV camera 5, a turn-on signal to the illumination unit 8, a start of input signal for the video signal to the video signal digitizer 29, and a start of image processing signal to the image processing means 31, in response to the input start of detection signal S.sub.1. When the ITV camera 5, the illumination unit 8, the image signal digitizer 29 and the image processing means 31 receives those signals, they carry out the functions assigned thereto as they do in the embodiment of FIG. 1. The present embodiment also attains the same advantages as those of the embodiment of FIG. 1. A software implemented embodiment of the image processing means 31 and the fuel number identification/discrimination means 32 of the microprocessor 30 used in the nuclear fuel identification code monitor 28 shown in FIG. 1 is explained with reference to FIG. 19. A microprocessor 30A which corresponds to the microprocessor 30 has input means 87A, output means 87B, a CPU 87C, a RAM 87D and a ROM 87E. The input means 87A is connected to the video signal digitizer 29 and the input output means 23B. The output means 87B is connected to the input/output means 23B and the fuel number processing means 44. An internal bus 87F connects the input means 87A, the output means 87B, the CPU 87C, the RAM 87D and the ROM 87E in the microprocessor 30A. The function of the memory 33 of the microprocessor 30 is effected by the RAM 87D. The output of the video signal digitizer 29 is stored in the RAM 87D. The ROM 87E stores the processing steps shown in FIGS. 9 and 10 with the steps 78F and 79A being removed and the step 79B being executed after the step 78E. In the present embodiment, the memory 33 of FIGS. 9 and 10 is replaced by the RAM 87D. The CPU 87C recognizes the letters of the nuclear fuel identification number 74B based on the video signal from the ITV camera 5 in accordance with the process stored in the ROM 87E. A software implemented embodiment of the ultrasonic signal processing means 40 and the fuel number identification means 41 of the microprocessor 39 used in the nuclear fuel identification code monitor 34 of FIG. 1 is explained with reference to FIG. 20. A microprocessor 39A corresponding to the microprocessor 39 has input means 89A, output means 89B, a CPU 89C, a RAM 87D and a ROM 89E which are interconnected through an internal bus 89F. The input means 89A is connected to the encoder 20 and the probe scanner control means 38. The output means 89B is connected to the fuel number processing means 44. The function of the memory 42 of the microprocessor 39 is effected by the RAM 87D. The processing steps shown in FIGS. 14 and 15 with the steps 81E and 82A being removed and the step 82B being executed after the step 81D are stored in ROM 87E. The CPU 87C recognizes the letters of the nuclear fuel identification number 74A based on the reflected ultrasonic wave in accordance with the process stored in the ROM 89E. In the embodiment of FIG. 1, the same advantages are attained when the microprocessor 30 is replaced by the microprocessor 30A and the microprocessor 39 is replaced by the microprocessor 39A. The recesses 75 of the nuclear fuel identification number 74A marked on the top 73 of the handle 72 of the fuel assembly 66 shown in FIG. 5 may be of an upside-down conical shape at the bottom as shown in FIG. 21. Preferably, the bottom of the recess 75 does not have a flat area which is parallel to the top 73. With such a shape, the scatter of the ultrasonic wave radiated to the recess 75 is violent and the reflected wave from the recess 75 back to the ultrasonic wave probe 9 is very little. As a result, the detection of the recess by the ultrasonic wave is facilitated. The technical concept of the above embodiments may be utilized in recognizing the nuclear fuel identification number marked on a fuel assembly of a pressured water type nuclear reactor. Other embodiment of the nuclear fuel identification code reader of the present invention is explained with reference to FIG. 22. Unlike the above embodiments, the nuclear fuel identification code reader of the present embodiment can be applied to a fuel assembly having no nuclear fuel identification code 74A marked on the top 73 of the handle 72. It can also recognize the nuclear fuel identification code 74B marked on the top 73 of the handle 72 by any one of the output signals of the optical sensor and the ultrasonic wave sensor. The constructions of the nuclear fuel handling unit 51 and the sensor handling unit 1 of the present embodiment are identical to those of the embodiment of FIG. 1. In the present embodiment, the nuclear fuel handling control unit 22, the nuclear fuel identification code monitors 28 and 34, and the nuclear fuel identification code processing unit 43 in FIG. 1 are replaced by a nuclear fuel handling control unit 100, nuclear fuel identification code monitors 250 and 260 and a data processing unit 240, respectively. The nuclear fuel handling control unit 100 has input/output means 23A and 23B, a nuclear fuel handling unit control means 24 and nuclear fuel detection unit control means 101. The input/output means 23A and 23B input and output signals similar to those for the nuclear fuel handling control unit 22 between the nuclear fuel handling unit 51 and the sensor handling unit 1. The nuclear fuel handling unit control means 24 and the nuclear fuel detection unit control means 101 are included in a computer 48A. The nuclear fuel identification code monitor 250 comprises image processing means 140, a video signal digitizer 150, a video frame memory 160, fuel number identification/discrimination means 170 and illumination control means 180. The functions of the image processing means 140, the image frame memory 160 and the fuel number identification/discrimination means 170 are effected by a microprocessor 30A. The illumination control means 180 may also be constructed by the microprocessor. The video signal digitizer 150 has the same function as the video signal digitizer 29. The fuel number identification/discrimination means 170 is coupled to the input/output means. The nuclear fuel identification code monitor 250 reads the nuclear fuel identification code by the video signal produced by the ITV camera 5. The nuclear fuel identification code monitor 260 comprises a signal processing microprocessor 39A, ultrasonic wave scanner control means 190 and ultrasonic wave transmit/receive means 200. The microprocessor 39A has the functions of the ultrasonic wave signal processing means 210 and the fuel number identification means 200A. The ultrasonic wave scanner control means 190 may also be constructed by the microprocessor. The ultrasonic wave transmit/receive means 200 comprises pulse generation means 35 and signal receive means 36. The pulse generation means 35 is connected to the ultrasonic wave probe 9 and the ultrasonic wave scanner control means 190. The signal receive means 36 is connected to the ultrasonic wave probe 9 and the ultrasonic wave signal processing means 210. The ultrasonic wave signal processing means 210 is coupled to the encoder 20 and the fuel number identification means 200. The ultrasonic wave scanner control means 190 is connected to the drive motors 13 and 17, the encoder 20 and the limit switch 37, and also to the input/output means 23B and the fuel number identification means 200A. The fuel number identification means 200 is coupled to the input/output means 23B and the fuel number identification means 170. The nuclear fuel identification code monitor 260 thus constructed recognizes the nuclear fuel identification code based on the reflected ultrasonic wave from the ultrasonic wave probe 9. The data processing unit 100 comprises fuel number processing means 44, a memory 45 and overall control means 241. The fuel number control means 44 is connected to the display 46, the printer 47, the fuel number identification/discrimination means 170 and the fuel number identification means 200A. The overall control means 241 is connected to the input/output means 23A and 23B, the fuel number identification/discrimination means 170 and the fuel number identification means 200. The memory 45 is connected to the fuel number processing means 44 and the overall control means 241. The console panel 270 is connected to the overall control means 241. The display 46 and the printer 47 may be arranged on the console panel 270. The fuel assemblies 66A (BWR fuel assemblies) whose nuclear fuel identification numbers are to be read by the present embodiment are loaded in the fuel rack 65. The fuel assembly 66A is of the same structure as the fuel assembly 66. However, unlike the fuel assembly 60, the fuel assembly 66A has no nuclear fuel identification number 74A marked on the top 73 of the handle 72. The recess 76 and engraved nuclear fuel identification number 74B are marked on the top 73 of the fuel assembly 66A. The recess 76 has the same function as that in the embodiment of FIG. 1. The operation of the nuclear fuel identification code reader of the present embodiment is now explained. The operator designates the activation of one of the nuclear fuel handling operation and the nuclear fuel identification code detection unit through the console panel 270. The designated activation signal is supplied to the computer 48A. If the former activation signal is designated, the nuclear fuel handling unit control means 24 is activated, and if the latter activation signal is designated, the nuclear fuel detection unit control means 101 is activated. It is assumed that the designated operation is the nuclear fuel handling operation. The nuclear fuel handling activation signal designated by the operator through the console panel 270 is supplied to the nuclear fuel handling unit control means 24 through the overall control means 241 and the input/output means 23A. Then, the nuclear fuel handling unit 51 is controlled by the nuclear fuel handling unit control means 24 as it is done in the embodiment of FIG. 1. Like the memory 26, the memory 45 stores the data relating to the load status of the fuel assembly 66A at each position in the fuel rack 65. The data in the memory 45 is updated when the load status of the fuel assembly 66A in the fuel rack 65 is changed by the movement of the used fuel assembly 66A by the nuclear fuel handling unit 51. The data is updated by the overall control means 241, which receives the related information from the nuclear fuel handling unit control means 24. When the activation of the detection unit is designated by the operator through the console panel 270, the overall control means 241 produces the detection unit activation signal. This signal is supplied to the nuclear fuel detection unit control means 101 through the input/output means 23B. The overall control means 241 reads the positions of the fuel assemblies 66A (positions K.sub.i on the chain line 49 starting at point K.sub.1) whose nuclear fuel identification numbers are to be detected, from the memory 45 and sequentially supplies them to the input/output means 23B at a predetermined time interval. The nuclear fuel detection unit control means 101 receives those signals and controls the movement of the sensor handling unit 1 in accordance with a process shown in FIG. 24. The process shown in FIG. 24 is essentially identical to the process shown in FIG. 8. The process shown in FIG. 24 is different from the process shown in FIG. 8 in that a step 77N is executed after the step 77F, and a step 77P is executed after the step 77J. The step 77N outputs the position V.sub.i of the ITV camera 5 determined based on the position signal representing the displacements X and Y measured by the synchronous signal generators. The step 77P outputs a position W.sub.i of the ultrasonic wave probe 9 determined based on the position signal representing the measured displacements X and Y. The position signal W.sub.i is produced when the fuel number identification means 170 produces a "1" output signal J (which is produced when all letters of the fuel identification number 74B are not recognized). Signals representing the positions V.sub.i and W.sub.i are produced by the input/output means 23B and supplied to the fuel number identification means 170 and the fuel number identification means 200A. Like the nuclear fuel monitor control means 25, the nuclear fuel detection unit control means 101 drives the ITV camera 5 which is the optical sensor for the nuclear fuel identification number onto the fuel assembly 66A under consideration, and drives the ultrasonic wave probe 9 which is the ultrasonic wave sensor onto the fuel assembly 66A for the detection of the fuel identification number 74B when it is difficult to recognize the fuel identification number 74B detected by the ITV camera 5. Through the step 77F, the movable truck 52 and the laterally movable truck 53 are driven and the ITV camera 5 is first moved toward the position K.sub.1. The fuel number identification means 170 receives the positions V.sub.i (X-Y ID coordinate) of the ITV camera 5 which are supplied from time to time by the input/output means 23B through the step 77M. A portion of the process of the fuel number identification/discrimination means 170 is explained with reference to FIG. 27. The fuel number identification/discrimination means 170 inputs, in a step 79L, the predetermined position K.sub.i (initially K.sub.1) supplied by the overall control means 241. In a step 79M, the position V.sub.i is inputted. The position V.sub.i is compared with the position K.sub.i (step 79N). If the decision in the step 79N is YES, it means that the ITV camera 5 is on the fuel 5 assembly 66A which is at the predetermined position K.sub.i At this point, the fuel number identification/discrimination means 170 supplies the illumination unit turn-on signal to the illumination control means 180 although it is not shown in FIG. 27. The illumination control means 180 turns on the illumination unit 8 in response to this signal. The illumination unit turn-on signal is produced only when the initial position V.sub.1 matches to the initial predetermined position K.sub.1. Then, the illumination unit 8 is kept turned on until the reading of the nuclear fuel identification codes for a predetermined number of fuel assemblies 66A is completed. The fuel number identification/discrimination means 170 produces a start of A/D conversion signal through the step 79P substantially simultaneously with the output of the illumination unit turn-on signal. The video signal digitizer 150 starts the A/D conversion of the video signal for the top 73 of the handle 72 imaged by the ITV camera 5. The image signal converted to the digital signal by the video signal digitizer 29 is supplied to the image frame memory 160 in 1/30 second and stored in the image frame 160. The image processing means 140 executes the process in accordance with the steps shown in FIG. 25. The process shown in FIG. 25 includes steps 78G-78I in addition to the steps shown in FIG. 9. After the steps 78A-78C, the step 78D is carried out. In the step 78D, one of intensity levels 0-255 is assigned to each of a number of pixels corresponding to one character (MXN pixels) in accordance with an image signal level of the corresponding portion. The rank 0 is darkest and the rank 255 is brightest. In the step 78G, a frequency distribution of the rank (FIG. 26) is determined in accordance with the intensity rank of each pixel. The frequency distribution is a distribution of number of pixels having the same intensity rank. A difference between a minimum frequency distribution and a maximum frequency distribution is compared with a predetermined value (step 78H). If the difference is not greater than the predetermined value, it means that the status in the binarization is not good, and a change of intensity signal is produced (step 78I). The illumination control means 180 receives the change of intensity signal to increase the intensity of the illumination unit 8. The time required for processing the above can be reduced to approximately 0.1 second by using a high speed illumination method such as a stroboscope illumination. After the intensity has been changed, the nuclear fuel identification number 74B is picked up by the ITV camera 5. If the decision in the step 78H is YES, the image signal is binarized in the step 78E to prepare the character pattern of the character. The binarization of the image signal is effected by selecting "1" for the signal which is larger than a predetermined reference between the minimum intensity rank and the maximum intensity rank of FIG. 26, and selecting "0" for the signal which is smaller than the predetermined reference. Then, the step 78F is carried out. After the step 78F, the fuel number identification/discrimination means 170 sequentially carries out the steps 79A-79K shown in FIG. 10 as shown in FIG. 27. If the decision in the step 79F is NO, a "1" output signal J is produced in the step 79K as it is in the previous embodiment. The "1" output signal J means that the discrimination of the nuclear fuel identification number 74B by the ITV camera 5 is impossible due to the deposition of the soft clad. The "1" output signal J is also a signal to request redetection of the nuclear fuel identification number 74B by the ultrasonic wave probe 9. When the fuel number identification/discrimination means 170 produces the "1" output signal J, the nuclear fuel detection unit control means 101 carries out the step 77J. The fuel number identification means 200 of the nuclear fuel identification code monitor 260 carries out the steps 76L-79P shown in FIG. 27. The predetermined position K.sub.i is inputted (step 79L). Then, the position W.sub.i of the ultrasonic wave probe 9 which varies from time to time and is produced by the nuclear fuel detection unit control means 101 in the step 77N is inputted. If the position W.sub.i matches to the predetermined position K.sub.i, the start of detection signal S.sub.2 is produced. The ultrasonic wave scan unit control means 190 carries out the steps 80B-80G shown in FIG. 12 when it receives the start of detection signal S.sub.2. The ultrasonic wave probe scan unit 10 is controlled by the signal which is derived through the steps 80B, 80C and 80E-80G. The signal receive means 36 receives the reflected wave signal detected by the ultrasonic wave probe 9. The reflected wave is supplied to the ultrasonic wave signal processing means 210. The ultrasonic wave signal processing means 210 carries out the process shown in FIG. 28. In a step 81A, the reflected ultrasonic wave signal and the position signal of the ultrasonic wave probe 9 detected by the encoder 20 are inputted. The binarization of the reflected wave signal in a step 81F is effected based on a time difference between the reflected wave signals of the focused ultrasonic wave beam radiated from the ultrasonic wave probe 9. The focused ultrasonic wave beam from the ultrasonic wave probe 9 is radiated normally to the top 73 of the handle 72 and the bottom 91 of the nuclear fuel identification number 74B (FIG. 29). The time at which the reflected wave signal for the top 73 is represented by t.sub.1 (FIG. 30A), and the time at which the reflected wave signal for the bottom 91 is received is represented by t.sub.2 (FIG. 30B). A time to represent the time at which the focused ultrasonic wave beam is radiated. A time t.sub.s (=(t.sub.2 -t.sub.1)/2) is set as a threshold level. If the reflected ultrasonic wave signal is detected at a time t where ts&gt;t, "0" is assigned to the position of the ultrasonic wave probe 9 at which the signal is detected If the reflected ultrasonic wave signal is detected at a time t where ts.ltoreq.t, "1" is assigned to the position of the ultrasonic wave probe 9 at which the signal is detected In this manner the reflected wave signal is binarized. In the present embodiment, the method 2) is used as it is in the previous embodiment. In the present embodiment, three or more ultrasonic wave probes 9 are arranged in parallel. In a step 81G, character patterns of the characters of the nuclear fuel identification number 74B are prepared in accordance with the position signal of the ultrasonic wave probe 9 and the binary signal produced in the step 81F. The prepared character patterns are supplied to the fuel number identification means 200 (step 81H). The fuel number identification means 200 carries out the steps shown in FIG. 31 which are essentially same as the steps shown in FIG. 10. If the decision in the step 79F is NO, the process is terminated. The fuel number processing means 44 stores the characters of the nuclear fuel identification code 74B identified by the nuclear fuel identification monitor 250 or 260 and the corresponding X-Y ID coordinates of the positions K.sub.i in the memory 45. It also displays them on the display 46 and prints them out by the printer 47 as may be required. The present embodiment also attains the same advantages as those of the embodiment of FIG. 1. However, since the nuclear fuel identification number 74B is detected by the ultrasonic wave probe 9 in the present embodiment, a longer recognition time is required than a case where the nuclear fuel identification number 74A is detected. Other embodiment of the nuclear fuel identification code reader of the present invention is explained with reference to FIGS. 32 and 33. In the present embodiment, a Chelencoff light camera 93 and a nuclear fuel monitor 280 are added to the embodiment shown in FIG. 22. The Chelencoff light camera 93 is mounted on the mount table 6 (FIG. 2) of the sensor handling unit 1. The nuclear fuel monitor 280 has a video signal digitizer 110 and a signal processing microprocessor 94 as shown in FIG. 33. The microprocessor 94 has an image frame memory 120, nuclear fuel data processing means 130 and image processing means 140A. The video signal digitizer 110 is coupled to the Chelencoff light camera 93. The nuclear fuel data processing means 130 is coupled to the input/output means 23B, the fuel number processing means and the overall control means 241. The present embodiment has means for determining if the used fuel assembly 66A stored in the fuel storage pool 63 is a real fuel assembly which contains the nuclear fuel. This means comprises the Chelencoff light camera 93 and the nuclear fuel monitor 280. The Chelencoff light camera 93 detects only a light in an ultraviolet range (Chelencoff light) emitted in water by a gamma ray emitted from a nuclear fission seed, amplifies it by a photo-multiplier and directs the amplified electrons to a phosphor plane to visualize them. The image picked up by the Chelencoff light camera 93 has a high intensity at an area corresponding to the water region surrounded by the fuel rods which contain the nuclear fuel. The nuclear fuel detection unit control means 101A of the nuclear fuel handling control unit 100 controls the movement of the sensor handling unit 1 in accordance with a process shown in FIG. 34. In the process shown in FIG. 34, steps 77Q and 77R are added between the steps 77N and 77H of the process shown in FIG. 24. After the movement of the ITV camera 5 in the step 77F, the Chelencoff light camera 93 is moved to the position K.sub.i in the step 77Q. The position U.sub.i of the Chelencoff light camera 93 thus changes from time to time, and the position U.sub.i is outputted (step 77R). The position U.sub.i outputted by the input/output means 23B is supplied to the nuclear fuel data processing means 130. The nuclear fuel data processing means 130 carries out the steps 79L-79P shown in FIG. 27 and supplies the start of A/D conversion signal to the video signal digitizer 110. The video signal digitizer 110 starts the A/D conversion of the video signal supplied from the Chelencoff light camera 93, in response to the start signal. The video signal converted to the digital signal is stored in the image frame memory 120 as the image signal. The image picked up by the Chelencoff light camera 93 does not always have a high S/N ratio. When it is to be determined whether the nuclear fuel is contained in the fuel assembly 66A, no special image processing is required for the video signal picked up by the Chelencoff light camera 93. However, in order to determine whether the nuclear fuel is contained or not in the fuel assembly to prepare a Chelencoff light pattern, the following processing is required. This image processing is done by the image processing means 140A. FIG. 35 shows the image processing means. An image signal is supplied from the image frame memory 120 (step 78A). A plurality of frame images taken time-serially are combined for each pixel (step 78G). A noise component of the image signal is reduced by the combination and the S/N ratio of the image signal is enhanced The image signal produced in the step 78G is vignetted (step 78H). Through this step, an RF noise component is eliminated from the image signal. The image signal having the RF noise component eliminated is binarized with a proper binarization level (step 78I). The binary data is supplied to the nuclear fuel data processing means 130. The Chelencoff light pattern is created based on the binary data (step 79Q). FIG. 37 shows the Chelencoff light pattern created in the step 78J. In FIG. 37, numeral 70A denotes a fuel rod and numeral 72A denote a handle. The fuel rods which contain the nuclear fuel are distinguished from other elements such as water rods which do not contain the nuclear fuel, and they are patterned. Based on the Chelencoff light pattern thus created, whether the fuel assembly 66A under consideration is the true fuel assembly which contains the nuclear fuel or not is determined (step 79R). The decision and the Chelencoff light pattern are supplied to the fuel number processing means (step 79S). The fuel number processing means 44 carries out the same steps as those of the fuel number processing means 44 of the embodiment shown in FIG. 22, as well as the following steps. If the decision in the step 79R is "true fuel assembly", a reference Chelencoff light pattern corresponding to the nuclear fuel identification number 74B recognized by the nuclear fuel identification code monitor 260 or 280, and the Chelencoff light pattern created in the step 79Q are compared. Through the comparison, it is determined whether the recognized nuclear fuel identification number 74B is correct or not. The result of this determination and the decision in the step 79R are displayed on the display 46. The present embodiment can attain the same advantages as those of the embodiment of FIG. 22. In the present embodiment, it is determined whether the fuel assembly 66A whose nuclear fuel identification number 74B is to be detected is true fuel assembly which contains the nuclear fuel or not. In the present embodiment, the correctness of the nuclear fuel identification number 74B recognized based on the Chelencoff light pattern can be checked and the accuracy of recognition of the nuclear fuel identification number is improved. In the embodiment shown in FIG. 32, since the Chelencoff light camera 93 is driven directly above the handle 72 of the fuel assembly 66A under consideration, the image of the handle 72 is patterned as shown in FIG. 37. As a result, the pattern of the fuel rods located directly below the handle 72 is not created. This problem may be solved by inclining the Chelencoff light camera 93 around the handle 72 by an angle .theta. on each side and picking up the top of the fuel assembly 66A from two directions G.sub.1 and G.sub.2, as shown in FIG. 38. The Chelencoff light camera 93 may be rotated in a direction 95 by a motor (not shown) mounted on the mount table 6. The video signals picked up by the Chelencoff light camera 93 from the directions G.sub.1 and G.sub.2 are supplied to the nuclear fuel monitor 280. Those video signals are converted to digital signals by the video signal digitizer 110 and they are stored in the image frame memory 120. The image processing means 140A processes those image signals for the directions G1 and G2 to produce binary data. In a step 79Q of the nuclear fuel data processing means 130, the Chelencoff light patterns created based on the video signals picked up from the directions G.sub.1 and G.sub.2 are combined to create a new Chelencoff light pattern (FIG. 39A). The Chelencoff light pattern created based on the data of the direction G.sub.1 is shown in FIG. 9B, and the Chelencoff light pattern created based on the data of the direction G.sub.2 is shown in FIG. 39C. The Chelencoff light pattern of FIG. 39A is created by image combination of a triangular pattern at right bottom of FIG. 39B and a triangular pattern at left top of FIG. 39C. In the Chelencoff light pattern of FIG. 39A, the handle shown in FIG. 39B and 39C (in broken lines) disappears. Accordingly, the Chelencoff light pattern located directly below the handle is created. The above embodiments are designed to read the nuclear fuel identification number marked on the BWR fuel assembly 66. The PWR fuel assembly 66B has the nuclear fuel identification number marked on the side of the top tie plate. A structure of an optical sensor which can read the nuclear fuel identification numbers marked on both types of fuel assemblies is shown in FIGS. 40A and 40B. FIG. 40A shows a read status for nuclear fuel identification number 74B marked on the fuel assembly 66. FIG. 40B shows a read status for the fuel assembly 66B. When this optical sensor is applied to the fuel assembly 66, a reflection mirror 96 supported by the ITV camera 5 is placed in parallel to the axis of the ITV camera 5. When it is applied to the fuel assembly 66B, the frame 7 and the illumination unit 8 are removed and a reflection mirror tube 97 is mounted on the mount table 6 instead, as shown in FIG. 40B. The reflection mirror tube 97 has a pair of reflection mirrors 99 at the top and the bottom thereof, and has an illumination unit 98 mounted at the lower end. The reflection mirror 96 is rotated to be obliquely to the axis of the ITV camera 5. The lower end of the reflection mirror tube 97 is inserted between the stored fuel assemblies 66B. The image of the nuclear fuel identification number 74B marked on the side at the upper end of the fuel assembly 66B is directed to the ITV camera 5 through the pair of reflection mirrors 99 and the reflection mirror 96. The optical sensor shown in FIGS. 40A and 40B is applicable to the nuclear fuel identification code readers of the above embodiments.

047642815

description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the principles of the present invention, residual radioisotope contents in the low parts-per-million range (and in fact often parts-per-billion) may be obtained by contacting the contaminated liquid with an insoluble form of a carboxylated cellulose, such as a carboxymethylcellulose, by flowing the liquid through a column containing the insoluble carboxylated cellulose. Sodium carboxymethylcellulose is available commercially, however, due to its water solubility, it is unsuitable for use in the present invention. The aluminum salt was used in the initial testing due to the ease of synthesis of the aluminum salt of carboxymethylcellulose. By way of example, an insoluble form of carboxymethylcellulose is obtained by mixing a solution of sodium carboxymethylcellulose with a solution of aluminum sulfate to produce an insoluble aluminum carboxymethylcellulose. Similarly, insoluble forms of carboxylated cellulose may be obtained by mixing the soluble form with ions other than aluminum ions, such as chromium ion (Cr.sup.+3), e.g., in the form of chromium nitrate or chromium chloride, to produce chromium carboxymethylcellulose. In accordance with an important feature of the present invention, nuclear or radioactive metals are removed from solution using an insoluble carboxylated cellulose by flowing the contaminated liquid solution through a bed of an insoluble form of carboxylated cellulose. The insoluble carboxylated cellulose is capable of removing unexpected quantities of nuclear or radioactive metals from liquids, for example radium, radon, molybdenum, praseodymium, polonium, lead, astatine, bismuth, thallium, mercury, zirconium, barium, promethium, uranium, cesium, strontium, ruthenium, neptunium, technetium, iodine, thorium, niobium, cerium, rubidium, palladium, curium, plutonium, tellurium, samarium, americium, protactinium, lanthanum, indium, neodymium, lutetium, rhodium or mixtures thereof and is particularly effective for removal of U, Ce, Sr, Ru, Ra, Np, Tc and other radioactive ions, such as I. In some cases a pre-treatment of the contaminated liquid is desirable to assist in removing a non-radioactive ions, molecules or complexes from the solution. For example, pre-treatment with hypochlorite, chlorine gas, ozone or other oxidizing agent is used for the destruction of ions such as cyanide. Additionally, other reagents may be used with the water-insoluble carboxylated cellulose to aid directly or indirectly in radioactive metal removal. It has been found that ammonium-complexed metal solutions are more amenable to treatment if the solution is first treated with sodium diethyldithiocarbamate. The carbamate itself does not remove the metal, but, through a catalytic effect or the formation of a new metal complex, diethyldithiocarbamate addition leads to much faster metal removal as the solution passes through the column. Treatment of a radioactive metal-bearing liquid may also involve the adjustment of the pH of the solution to facilitate the reaction or to comply with minicipal sewer requirements. In accordance with an important feature of the present invention, contact of the liquid to be treated with the insoluble carboxylated cellulose, particularly carboxymethylcellulose, creates an insoluble, radioisotope-laden carboxylated cellulose material which can be disposed of as a small volume of material, either by direct burial because of its biodegradability or calcination at 400.degree. to 500.degree. C. to fuse the material into small microscopic ceramic fibrils rather than the usual entrainable fine powder, which thereafter can be buried in an approved EPA landfill. Initial evaluation of water-insoluble carboxylated cellulose for possible use in removing radioactive metals from nuclear waste streams initially centered on a slurry treatment technique. However, it was realized that a vertical column loaded with water-insoluble aluminum carboxymethylcellulose produced more efficient radioactive metals removal, thus tests were conducted using this technique. A disposable, plastic cartridge, preloaded with an insoluble carboxylated cellulose could easily retrofit into the existing equipment of the user, and is ideally suitable for the above-mentioned calcination and burial after loading to capacity with a radioactive metal. Five separate tests were conducted and quantified by beta and alpha counting of dried aliquots of the feed and effluent solutions. Four of these tests were performed using actual samples taken from a low-level waste stream. The fifth was performed on a laboratory prepared .sup.235 U solution. These results are shown in Table 1 and are expressed in Becquerels per liter. (One Becquerel=one disintegration per second.) TABLE I ______________________________________ ACTIVE TESTS Diversion Box Samples Sample Number Alpha BQ/L pH ______________________________________ Beta-Gamma BQ/L 1 Feed 800 .+-. 30 24 .+-. 9 6 Effluent 24 .+-. 6 4.5 .+-. 4.5 6 2 Feed 650 .+-. 30 20 .+-. 8 6 Effluent 28 .+-. 7 4 .+-. 4 6 3 Feed 1400 .+-. 100 53 .+-. 13 8 Effluent 410 .+-. 20 20 .+-. 8 8 4 Feed 1100 .+-. 100 50 .+-. 3 6 Effluent 16 .+-. 3 10 .+-. 2 6 .sup.235 UO.sub.2 (NO.sub.3).sub.2 pH 3 Alpha 5 Feed 1.78 .times. 10.sup.9 BQ/L Effluent 3 .times. 10.sup.3 BQ/L ______________________________________ In addition, seven other qualitative tests of the affinity of the insoluble aluminum carboxymethylcellulose for different elements, which occur in nuclear wastes, were conducted. Each test was conducted through 200 ml bed volume contained in a 1 inch diameter glass container having a bed height of 15.5 inches. The flow conditions and influent stream contaminants are shown in Table II: TABLE II ______________________________________ Test Conditions: Flow Rate: 200 ml/min Total Thru-put: 1000 ml (5 bed volumes) Sampled: last 100 ml Bed washed with 1000 ml distilled water, before loading Qualitative 1. Iodine pH 6 1 mg/ml 2. Uranium pH 6 0.5 mg/ml 3. Ruthenium pH 8 2 mg/ml 4. Rhenium (for Tc) pH 6 1 mg/ml 5. Cesium pH 6 1 mg/ml 6. Strontium pH 6 1 mg/ml 7. Rare-Earth Mixture pH 5 1 mg/ml ______________________________________ The feed solutions prepared for these determinations consisted only of distilled water and the element of interest in a water-soluble form. The solution pH was adjusted with sodium hydroxide to the value shown. In each test a sample of the feed and effluent was treated by adding a particular reagent, which is known to precipitate the subject element present. The two samples were then compared visually to ascertain degree removal and thru-flow. In all tests except those for strontium, rare earths, and rhenium (which was substituted for technetium), there was definite evidence of removal being denoted by complete absence of precipitation in the effluents. The ability of an insoluble form of carboxymethylcellulose to remove low levels of radioactive isotopes from naturally occurring waters also is quite unexpected. Many of the water systems in the West Central Illinois region draw water from deep wells which contain radioactive radium 226 and 228 in combined concentrations upwards of 30 pico-curies per liter. To remove these low level radioactive isotopes, a test column with a diameter to height ratio of 1:6, and containing a settled volume of 100 cubic centimeters of aluminum carboxymethylcellulose was prepared. Through this column bed, a one liter volume of tap water (10 bed volumes) containing a 226 radium concentration of 1.56.times.10.sup.5 disintegrations per second per liter (d/s/L) (Bequerels per liter) or 4.22.times.10.sup.6 pico-curies per liter was passed. The pH of the column feed was 7.0 and the flow rate was 100 cc/min or one bed volume per minute. The total one liter effluent was collected, mixed, and sampled. Immediate radio-assay of this sample indicated a level of 2.26.times.10.sup.4 d/s/L of gross activity or 6.11.times.10.sup.5 pico-curies per liter (85.5% activity removal). After six hours the count rate of the effluent sample had dropped by 10%; after 24 hours the count rate was reduced by 22%. The sequence of decay of 226 radium causes the radio-assay of this element to become very complex by ordinary counting techniques. 226 Radium undergoes nine (9) sequential elemental changes before decaying to stable 204 lead. Each of these transitions produces radioactivity. 222 Radon, the first daughter of 226 radium, is an inert gas and very soluble in water. Being chemically inert, radon passes through the aluminum carboxymethylcellulose bed with the effluent, and continues through the normal decay mode. In consideration of the relatively rapid decline in the count rate of the effluent sample, it is believed that the bulk of the activity in the effluent is due to the decay daughters of carried-thru radon, which can be substantiated by long term counting. It is obvious that no appreciable amount of 226 radium can be present in a solution that decays 22% in 24 hours since the half-life of 226 radium is 1622 years. While longer term counting is required to accurately quantify this experiment, the initial results justify the conclusion of substantial reduction of naturally occurring radioactivity from a water source. In accordance with an important feature of the present invention it has been found that aluminum carboxymethylcellulose may be coupled with other radioactive metal removal techniques to produce a synergistic removal of the radioactive contaminants from water. For example, manganese dioxide, known as an adsorber of metal ions, can be combined with aluminum carboxymethylcellulose to provide an adduct unexpectedly capable of removing substantially all the radioactivity from a water solution containing radium in equilibrium with its decay daughters. EXAMPLE 1 Aluminum carboxymethylcellulose was prepared by dissolving 100 grams of hydrated aluminum nitrate in two liters of water, heating the solution to 90.degree. C., then, with good agitation, slowly adding 25 grams of sodium carboxymethylcellulose. After the addition of sodium carboxymethylcellulose, agitation was continued until the mixture cooled, then the precipitated aluminum carboxymethylcellulose was filtered off and washed. The aluminum carboxymethylcellulose was allowed to air dry, and was stored. EXAMPLE 2 550 milliliters of a solution containing 250 millgrans of Uranium as U 235, 20 milligrams of Neptunium as Np 237 and 5 milligrams of Technetium as Tc 99 was passed through a one inch column containing 150 milliliter volume of the previously prepared aluminum carboxymethylcellulose. The separation of these metals from the solution were measured as removal of alpha and beta particles, with 100% of all alpha particles being removed and 99.6% of all beta particles being removed. EXAMPLE 3 Aluminum carboxymethylcellulose was saturated with manganese dioxide. The adduct was placed in a column, and was used to remove radioactive radium and its decay daughters according to the following procedure: Column diameter--1 in. PA1 Bed volume--60 cc PA1 Flow rate--30 cc/min. (avg.) PA1 Total feed--600 cc (10 bed volumes) PA1 pH--7.3 PA1 Feed activity (gross alpha - Radium and daughters in equilibrium). 6.723.times.10.sup.4 disintegrations per second per liter (Becquerels per liter) PA1 1st 200 cc through O-d/s/l PA1 2nd 200 cc through 1.90.times.10.sup.2 d/s/l=0.28% PA1 3rd 200 cc through O d/s/l Test samples from 3-200 cc successive collections of effluent: The count in the second sample represents 3.8 counts per minute, per cc, above background count rate of the instrument (3 per minute) - for minimal accuracy, the sample count rate should be at least 50 times the background, thus the reading in this test is insignificant. It should be understood that the present disclosure has been made only by way of preferred embodiment and that numerous changes in details of construction, combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinunder claimed.

summary

claims

1. An X-ray lens assembly, comprising:a tube member including an inlet opening for X-rays and an outlet opening for X-rays;a capillary X-ray lens;axially spaced mounting structures mounting the X-ray lens inside the tube member; anda chamber defined between the tube member, the X-ray lens, and the mounting structures filled with a stabilizing agent that holds the X-ray lens in the tube member. 2. The X-ray lens assembly of claim 1, wherein the stabilizing agent includes a glue. 3. The X-ray lens assembly of claim 1, wherein the tube member further includes at least one further opening arranged between the inlet opening and the outlet opening, wherein the at least one further opening is in communication with the chamber. 4. The X-ray lens assembly of claim 3, wherein the stabilizing agent has been filled into the chamber through the at least one further opening. 5. The X-ray lens of claim 1, wherein the one or more mounting structures comprise at least one elastic member. 6. The X-ray lens assembly of claim 5, wherein the at least one elastic member comprises an elastic ring. 7. The X-ray lens assembly of claim 1, wherein the mounting structures allow for an axial displacement of the X-ray lens inside the tube member. 8. An X-ray device, comprisingan X-ray source; andan X-ray lens assembly including a tube member having an inlet opening for X-rays and an outlet opening for X-rays, a capillary X-ray lens, axially spaced mounting structures mounting the X-ray lens inside the tube member, and a chamber defined between the tube member, the X-ray lens, and the mounting structures filled with a stabilizing agent that holds the X-ray lens in the tube member. 9. A method of manufacturing an X-ray lens assembly, comprising:providing a tube member having an inlet opening for X-rays and an outlet opening for X-rays;providing a capillary X-ray lens; andmounting the X-ray lens inside the tube member using axially spaced mounting structures; andfilling a chamber defined between the tube member, the X-ray lens, and the mounting structures with a stabilizing agent that holds the X-ray lens in the tube member.

046506349

summary

TECHNICAL FIELD The present invention relates generally to nuclear reactor facilities, and more particularly to a mounting system for a television camera which enables the latter to be mounted internally within the refueling machine gripper tube or inner movable mast so as to be movable therewith, thereby facilitating the guidance of the refueling machine gripper assembly relative to the fuel assemblies of the reactor core for achieving accurate alignment of the gripper assembly with respect to a particular fuel assembly in preparation for, and achievement of, latching of the gripper assembly with the particularly selected fuel assembly nozzle, whereby the particular fuel assembly may be lifted out of the reactor core and replaced with a new or fresh fuel assembly by means of the refueling machine. BACKGROUND ART As is well known in the nuclear reactor art, the reactor core fuel assemblies need to be periodically replaced in view of the fact that the nuclear fuel within the fuel assemblies becomes depleted as a result of the normal operation of the reactor facility. In accordance with conventional techniques or modes of operation, spent fuel assemblies are removed from the reactor core and replaced with new or fresh fuel assemblies by means of a refueling machine. The refueling machine conventionally comprises a trolley movable within a horizontal plane along a suitable track system disposed above the reactor core at an elevational height of, for example, thirty-five feet, and a vertically disposed outer or stationary mast is fixedly mounted upon the refueling machine trolley so as to be movable therewith. A vertically movable inner mast or gripper tube is co-axially disposed interiorly of the outer stationary mast, and a gripper assembly is fixedly secured to the lower end of the refueling machine gripper tube or inner mast. Guide pins are, in turn, fixedly secured to the lower end of the gripper assembly and are adapted to mate with suitable, correspondingly located apertures provided within the upper surface of each fuel assembly. Suitable gripper mechanisms or fingers are provided within the refueling machine gripper assembly for latchably mating with corresponding or cooperating structure of the fuel assembly nozzles, the gripper assembly guide pins serving to accurately align the gripper assembly with respect to the fuel assembly such that the gripper fingers may in fact latchably engage the fuel assembly nozzle structures. The latchable gripper mechanisms or fingers of the gripper assembly are movable between their latched and unlatched positions by means of an actuator mechanism disposed upon the lower end of a vertically movable, actuator tube co-axially disposed within the refueling machine gripper tube or inner mast. In order to achieve the aforenoted alignment of the gripper assembly relative to the particular fuel assembly to be replaced so as to in fact achieve the aforenoted latching of the gripper mechanisms or fingers with the fuel assembly nozzle structure, it is imperative that the operator have a clear and unobstructed view of the fuel assembly nozzle. This, however, has proven to be a considerably difficult task to achieve when operating conventional refueling machines in view of the fact that the operator observes the fuel assembly nozzle structure through a suitable viewing aperture or window defined within the refueling machine trolley deck. Consequently it is readily appreciated that not only is the operator located a considerable distance away from the fuel assembly nozzle structure, but in addition, the reactor core cavity is entirely immersed within water. Therefore, light refraction causes distortion and an apparent erroneous location of the fuel assembly nozzles. Still further, in order to view the fuel assembly nozzles, the operator must attempt the viewing operation from a position other than that which would be co-axial with the fuel assembly nozzles. Consequently, such an angularly offset location of the operator's viewpoint increases the aforenoted distortion, and therefore compounds the difficulty in accurately viewing the fuel assembly nozzle structures and obtaining the desired alignment of the gripper mechanism fingers therewith. In an attempt to resolve this problem, it has been proposed to employ television cameras mounted upon the outer stationary mast of the refueling machine. This technique, however, has likewise proven to be unsatisfactory in view of the fact that the fuel assemblies are nevertheless being viewed from a vantage point which is inclined or angularly oriented relative to a vertical axial plane of the fuel assemblies. Accordingly, it is an object of the present invention to provide a new and improved nuclear reactor refueling machine. Another object of the present invention is to provide a new and improved nuclear reactor refueling machine which will overcome all of the aforenoted disadvantages of the conventional nuclear reactor refueling machines and the refueling operations characteristic thereof. Still another object of the present invention is to provide a new and improved nuclear reactor refueling machine which will greatly facilitate the alignment of the gripper assembly with the particular fuel assembly to be removed from the reactor core and replaced with a fresh or new fuel assembly so as to enhance the ease and efficiency of the nuclear reactor facility refueling process. Yet another object of the present invention is to provide a new and improved nuclear reactor refueling machine which will provide the refueling machine operator or personnel with a clear and unobstructed view of the fuel assemblies of the reactor core so that the gripper assembly of the refueling machine, and its gripper mechanisms or fingers, can be rapidly, easily, and accurately aligned with or positioned relative to the particular fuel assemblies which are to be removed from the reactor core and replaced with fresh or new fuel assemblies. Still yet another object of the present invention is to provide a new and improved nuclear reactor refueling machine which will permit the refueling machine operator or personnel, who is positioned at a location within the reactor facility which is remote from the reactor core and its fuel assemblies, to view the particular fuel assemblies which are to be removed from the reactor core and replaced with fresh or new fuel assemblies from a vantage point which is effectively within the immediate vicinity of the reactor core and the associated fuel assemblies. Yet still another object of the present invention is to provide a new and improved nuclear reactor refueling machine which will permit the refueling machine operator or personnel, who is positioned at a location within the reactor facility which is remote from the reactor core and its fuel assemblies, to view the particular fuel assemblies which are to be removed from the reactor core and replaced with fresh or new fuel assemblies from a vantage point which is directly above the particular fuel assembly which is to be removed from the reactor core and replaced with a fresh, new, or different fuel assembly such that the refueling machine operator's view of the particular fuel assembly is not angularly offset or oriented relative to the particular fuel assembly, or distorted by means of the light refraction properties of the water disposed within the reactor core cavity. DISCLOSURE OF THE INVENTION The foregoing and other objectives of the present invention are achieved through the provision of a nuclear reactor refueling machine wherein a television camera is mounted within the refueling machine gripper tube or inner mast which is telescopically movable in a co-axial mode relative to the outer or stationary mast of the refueling machine. In particular, the television camera is mounted within the refueling machine actuator tube which is, in turn, telescopically movable in a co-axial mode relative to the gripper tube or inner mast of the refueling machine. Video signals from the television camera are of course able to be transmitted by means of suitable cables, housed or accommodated within the actuator tube, as well as within the gripper tube or inner mast, of the refueling machine, to a remote television monitor located upon the refueling machine trolley for viewing or monitoring by means of the refueling machine operator or personnel. In this manner, and particularly in view of the fact that the refueling machine outer or stationary mast, the refueling machine inner mast or gripper tube, the refueling machine actuator tube, the refueling machine gripper assembly, and the television camera are all co-axially aligned with respect to each other, the refueling machine operator or personnel is able to view the particular fuel assembly, which is to be removed from the reactor core and replaced with a new or different fuel assembly, from a vantage point which is co-axially aligned with the particular fuel assembly to be so removed and replaced. In view of the additional fact that the lower end of the actuator tube, the lower end of the gripper tube or inner mast, and the television camera will be immersed within the water disposed within the reactor core cavity, all possible sources of visual distortion, misalignment, and location error of the particular fuel assembly relative to the refueling machine gripper assembly, will have been eliminated or at least substantially reduced. The alignment process to be defined between the refueling machine gripper assembly and the particular fuel assembly to be removed from the core and replaced with a new or different fuel assembly is thus appreciated to be capable of being performed with an enhanced degree of efficiency in view of the foregoing as well as the fact that the refueling machine operator or personnel has been effectively provided with a viewing or vantage point immediately within the vicinity of the particular fuel assembly to be removed and replaced. The television camera is secured within the refueling machine actuator tube by means of a bayonet type mounting system, and in this manner, the camera may be removed from, and inserted into, the actuator tube in a simplified manner should maintenance, repair, or replacement of the same prove necessary. Suitable decoupling means are of course preferably provided in conjunction with the electrical connector hardware which serves to connect the camera with its power and signal cables so as to permit disconnection of the same when, for example, the camera is being serviced or replaced. The mounting system for the television camera within the actuator tube assembly is further provided with suitable shock absorbing means whereby the camera will be isolated from any shock loads which may be encountered during a fuel assembly refueling operation.

051026163

summary

The present invention relates to integral water cooled nuclear reactors with pressurisers, and is particularly applicable to water cooled nuclear reactors of the integral pressurised water reactor (PWR) type and the integral indirect cycle boiling water reactor (BWR) type with integral pressurisers. However the invention is also applicable to integral water cooled nuclear reactors with separate pressurisers and to dispersed or loop type pressurised water reactors (PWR's) with separate pressurisers. A problem with water cooled nuclear reactors is that under some severe accident conditions effective cooling of the nuclear reactor core can be lost very quickly. Emergency core cooling systems are provided in the prior art, but under some severe circumstances these are not sufficiently fast acting to restore cooling before some damage to the nuclear reactor core occurs. The design philosophy of these emergency core cooling systems is to restore cooling to the nuclear reactor core before the core damage results in an uncoolable nuclear reactor core geometry rather than to prevent damage to the nuclear reactor core under all circumstances. A further problem with water cooled nuclear reactors is the long term removal of residual heat from the nuclear reactor core in the event that heat removal by the normal means is lost. Residual heat removal systems are provided in the prior art for such emergencies. Emergency core cooling and residual heat removal systems of the prior art are controlled and operated by active components which may fail to function when required. Residual heat removal systems of the prior art also have active pumping components. Such active components require external electrical or other energy sources which may fail to operate during emergency conditions. To mitigate such possibilities the emergency core cooling and residual heat removal systems of the prior art and their support systems are replicated leading to complication and high cost. Such prior art emergency core cooling and residual heat removal systems of the prior art make it difficult to produce cost effective water cooled nuclear reactor power plants of low and moderate power rating. The present invention seeks to provide an emergency core cooling and residual heat removal system which maintains nuclear reactor core cooling at all times during severe accident conditions by passive safety systems, which are continuously available when the nuclear reactor is operating normally, to prevent nuclear reactor core damage. The present invention also seeks to provide a low cost water cooled nuclear reactor power plant in low and moderate power ratings by simplification of safety systems and by obviating the need for replication. According to the present invention a water cooled nuclear reactor comprises a pressure vessel, a reactor core, a primary water coolant circuit arranged to cool the reactor core, the reactor core and at least a portion of the primary water coolant circuit being located in the pressure vessel, a pressuriser having a water space and a steam space, at least one full pressure reactor core cooler means, a first pipe means to interconnect an upper portion of the primary water coolant circuit with each full pressure reactor core cooler means, a second pipe means to interconnect a lower portion of the primary water coolant circuit with each full pressure reactor core cooler means, each first pipe means having a first inverted U-bend, each first inverted U-bend of the first pipe means passes through the water space and steam space of the pressuriser to form a vapour lock within each first inverted U-bend, whereby each vapour lock in normal operation substantially prevents a natural circulation of primary water coolant from the primary water coolant circuit through the first pipe means, the full pressure reactor core cooler means and the second pipe means to the primary water coolant circuit, each vapour lock sensing abnormal operation of any of the reactor core, the primary water coolant circuit, the pressuriser or loss of primary water coolant and thereby being displaced from the first inverted U-bend to allow a natural circulation of primary water coolant from the primary water coolant circuit through the first pipe means, the full pressure reactor core cooler means and the second pipe means to allow relatively cool primary water coolant from the full pressure reactor core cooler means flow into or through the primary water coolant circuit. Preferably at least one of the full pressure reactor core cooler means may comprise a full pressure emergency core coolant tank having a reserve supply of primary water coolant, the first pipe means interconnects an upper portion of the primary water coolant circuit with an upper portion of the full pressure emergency core coolant tank, the second pipe means interconnects a lower portion of the primary water coolant circuit with a lower portion of the full pressure emergency core coolant tank, at least a portion of the full pressure emergency core coolant tank being positioned above the reactor core, the first pipe means having a first inverted U bend, the first inverted U-bend of the first pipe means passes through the water space and steam space of the pressuriser to form a vapour lock within the first inverted U-bend, whereby the vapour lock in normal operation substantially prevents a natural circulation of primary water coolant from the primary water coolant circuit through the first pipe means, the full pressure emergency core coolant tank and the second pipe means to the primary water coolant circuit, the vapour lock sensing abnormal operation of the reactor core, the primary water coolant circuit, the pressuriser or loss of primary water coolant and thereby being displaced from the first inverted U-bend to allow a natural circulation of primary water coolant from the primary water coolant circuit through the first pipe means, the full pressure emergency core coolant tank and the second pipe means to the primary water coolant circuit to allow relatively cool primary water coolant in the full pressure emergency core coolant tank to flow through the reactor core, or to allow primary water coolant vapour to be vented from the primary water coolant circuit through the first pipe means into the full pressure emergency core coolant tank to facilitate a gravity feed of primary water coolant from the full pressure emergency core coolant tank into the primary water coolant circuit. At least one of the full pressure reactor core cooler means may comprise a full pressure residual heat removal heat exchanger, the first pipe means interconnects an upper portion of the primary water coolant circuit with an upper portion of the full pressure residual heat removal heat exchanger, the second pipe means interconnects a lower portion of the primary water coolant circuit with a lower portion of the full pressure residual heat removal heat exchanger, at least a portion of the full pressure residual heat removal heat exchanger being positioned above the primary water coolant circuit, the first pipe means having a first inverted U-bend, the first inverted U-bend of the first pipe means passes through the water space and steam space of the pressuriser to form a vapour lock within the first inverted U-bend whereby the vapour lock in normal operation substantially prevents a natural circulation of primary water coolant from the primary water coolant circuit through the first pipe means, the full pressure residual heat removal heat exchanger and the second pipe means to the primary water coolant circuit, the vapour lock upon abnormal operation of the reactor core, the primary water coolant circuit, the pressuriser or loss of primary water coolant is thereby displaced from the first inverted U-bend to allow a natural circulation of primary water coolant from the primary water coolant circuit through the first pipe means, the full pressure residual heat removal heat exchanger and the second pipe means to the primary water coolant circuit to allow relatively cool primary water coolant to flow through the reactor core. The full pressure residual heat removal heat exchanger and the full pressure emergency core coolant tank may be integrated and fludily connected in flow series such that they share a common first pipe means, first inverted U-bend and second pipe means. The full pressure residual heat removal heat exchanger and the full pressure emergency core coolant tank may be separate and have their own respective first pipe means, first inverted U-bend and second pipe means. At least a portion of the full pressure emergency core coolant tank may be positioned above the primary water coolant circuit. The inverted U-bend in the first pipe means may have an electrical immersion heater to assist in the formation and maintenance of the vapour lock and to facilitate the removal of incondensible gases. Each first pipe means may have hydrostatic thermal seals which facilitate the circulation of warm water eddy currents within the first pipe means during normal operation of the reactor plant, but which prevent the warm water eddy currents from entering the full pressure reactor core cooler means in normal operation of the nuclear reactor and which allow the natural circulation of primary water coolant from the primary water coolant circuit through the first pipe means, the full pressure reactor core cooler means and the second pipe means if the vapour lock is displaced from the first inverted U-bend by abnormal operation of the reactor core, the primary water coolant circuit or the pressuriser. A second inverted U-bend in each first pipe means may form one hydrostatic thermal seal. A U-bend in the first pipe means may also form a hydrostatic thermal seal. Each second pipe means may have a hydrostatic thermal seal preventing thermal convection of warm water from the primary water coolant circuit to the full pressure reactor core cooler means during normal operation of the reactor. A U-bend in the second pipe means may form the hydrostatic thermal seal. At least one pair of inverted U-bend and normal U-bend connected in series in each second pipe means may form the hydrostatic thermal seal, the inverted U-bend is positioned in a relatively hot region and the normal U-bend is positioned in a relatively cool region to produce alternating stratified zones of lower and higher water density in the hydrostatic thermal seal. The pressuriser may have an auxiliary vessel, the auxiliary vessel having a water space and a steam space, at least the water space of the auxiliary vessel being interconnected with the water space of the pressuriser, the first inverted U-bend of the first pipe means passes through the water space and steam space of the auxiliary vessel. The pressuriser may have an auxiliary vessel, the auxiliary vessel having a water space and a steam space, at least the water space of the auxiliary vessel being interconnected with an upper portion of the primary water coolant circuit, the first inverted U-bend of the pipe means passes through the water space and steam space of the auxiliary vessel. The steam space of the auxiliary vessel may be interconnected with the steam space of the pressuriser. The auxiliary vessel may have an electrical immersion heater to maintain saturation conditions in the water space and steam space of the auxiliary vessel. The auxiliary vessel may define a portion of the first inverted U-bend and the steam space of the auxiliary vessel may form the vapour lock. A relatively small vent may interconnect the vapour lock and the steam space of the pressuriser to allow the flow of in-condensible gases from the vapour lock to the steam space of the pressuriser, to assist in the formation and maintenance of the vapour lock in normal operation and to provide the vapour lock with the required transient response. The full pressure emergency core cooling and residual heat removal system may have at least one residual heat removal means to remove heat from the primary water coolant in the full pressure emergency core cooling and residual heat removal system. Each full pressure emergency core coolant tank may be integrated with the full pressure residual heat removal heat exchanger having at least one residual heat removal circuit to remove heat from the primary water coolant in a combined full pressure emergency core cooling and residual heat removal system. The at least one combined full pressure emergency core cooling and residual heat removal tank may have an enclosed region, the first pipe means interconnects the primary water coolant circuit and the enclosed region, the enclosed region having one of the residual heat removal circuits to increase the heat transfer rate from the primary water coolant to the residual heat removal circuit. The residual heat removal circuit may comprise a first heat exchanger positioned in the full pressure emergency core coolant and residual heat removal tank, a second heat exchanger positioned outside of the full pressure emergency core coolant and residual heat removal tank, ducting interconnecting the first and second heat exchangers to convey working fluid therebetween. The reactor pressure vessel may be positioned in the full pressure emergency core coolant tank. The reactor pressure vessel and pressuriser may be positioned within the combined full pressure emergency core coolant and residual heat removal tank as an integral unit, the full pressure emergency coolant tank becoming the integrated pressure vessel and the reactor vessel becoming a thermal and flow control boundary between the primary circuit and the reserve volume of full pressure emergency coolant. A second low pressure emergency core cooling and residual heat removal system may comprise a tank having a further reserve supply of primary water coolant at low pressure, at least a portion of the low pressure emergency core cooling and residual heat removal tank being positioned above the full pressure emergency core cooling and residual heat removal system, a third pipe means to interconnect a lower portion of the second low pressure emergency core cooling and residual heat removal tank with the full pressure emergency core coolant and residual heat removal system or with the primary circuit, a fourth pipe means to interconnect the steam space of the pressuriser with the low pressure emergency core coolant tank, the third pipe means having a non return valve and a control valve, the fourth pipe means having a control valve. At least one second residual heat removal means may be arranged to remove heat from the water in the second low pressure emergency core cooling and residual heat removal tank. The water in low pressure emergency core cooling and residual heat removal tank may form a heat sink for the full pressure emergency core cooling and residual heat removal system. The full pressure residual heat removal cooler may be located in the low pressure emergency core cooling and residual heat removal tank. The full pressure emergency core cooling and residual heat removal system may be located in the low pressure emergency core cooling and residual heat removal tank. The pressure vessel may be located within a dry chamber defined by a cylindrical walled member, the cylindrical walled member being positioned in the low pressure emergency core cooling and residual heat removal tank, a vent interconnects an upper region of the dry chamber with a lower region of the emergency core cooling and residual heat removal tank. A containment building may contain, the reactor pressure vessel, the reactor core, the primary water coolant circuit, the pressuriser, the full pressure emergency core cooling and residual heat removal system and the second low pressure emergency core cooling and residual heat removal tank, a fifth pipe means may interconnect a pump means with the low pressure emergency core cooling and residual heat removal tank, the pump means being arranged to pump any split water coolant above a predetermined level in the containment building to the low pressure emergency core cooling and residual heat removal tank, the fifth pipe means may have a non return valve. The at least one second residual heat removal circuit may comprise a third heat exchanger positioned in the second, low pressure, emergency core cooling and residual heat removal tank, a fourth heat exchanger positioned outside of the containment building, ducting means interconnecting the third and fourth heat exchangers to convey working fluid therebetween. A fifth heat exchanger may be positioned substantially at the uppermost region of the containment building, ducting means interconnecting the fifth heat exchanger and the fourth heat exchanger to convey working fluid therebetween, a collecting vessel positioned below the fifth heat exchanger and above the second, low pressure emergency core cooling and residual heat removal tank for collecting vapour condensed by the fifth heat exchanger, pipe means to supply condensed vapour from the collecting vessel to the second, low pressure emergency core cooling and residual heat removal tank. Ducting means may interconnect an intermediate heat exchanger and the fourth heat exchanger to convey working fluid therebetween, the second heat exchanger exchanging heat to the intermediate heat exchanger, the intermediate heat exchanger and second heat exchanger being positioned inside the containment building. The emergency core cooling and residual heat removal tanks may contain a neutron absorbing agent, dissolved in the water. The neutron absorbing agent may be boron, in the form of boric acid. At least a portion of the water space of the pressuriser may be positioned above an upper portion of the primary water coolant circuit, at least one vent means which communicates between the pressuriser and the primary water coolant circuit to connect the steam space of the pressuriser with the upper portion of the primary water coolant circuit, at least one surge port means which communicates between the pressuriser and the primary water coolant circuit to connect the water space of the pressuriser with a lower portion of the primary water coolant circuit, the at least one surge port means being arranged to have relatively low flow resistance for water from the water space of the pressuriser to the primary water coolant circuit and relatively high flow resistance for water from the primary water coolant circuit to the water space of the pressuriser, the at least one vent means which communicates between the steam space of the pressuriser and the upper portion of the primary water coolant circuit allows excess vapour formed in the primary water coolant circuit to flow to the steam space of the pressuriser. The reactor core, the primary water coolant circuit and the pressuriser may be arranged as an integral unit enclosed by the pressure vessel, at least one casing being arranged in the pressure vessel to substantially divide the pressure vessel into a first chamber and a second chamber, the reactor core and the primary water coolant circuit being arranged in the second chamber, the pressuriser being arranged in the first chamber, the casing preventing mixing interaction between the water in the primary water coolant circuit and the water in the water space of the pressuriser. The first pipe means may interconnect the water space of the pressuriser with the full pressure reactor core cooler means. The reactor core may be arranged in the lower region of the pressure vessel, the primary water coolant circuit comprising a riser passage to convey relatively hot water and steam to at least one heat exchanger, and a downcomer passage to convey relatively cool water from the at least one heat exchanger to the reactor core. The at least one heat exchanger may be a steam generator. The heat exchanger may be positioned in the pressure vessel. The primary water coolant circuit may comprise at least one pump to assist the circulation of primary water coolant. The pressuriser may be a separate pressuriser. The water cooled nuclear reactor may be an integral pressurised water reactor. The water cooled nuclear reactor may be an integral indirect cycle boiling water reactor.

claims

1. A method for optical proximity correction, comprising:generating a simulated geometry representing one or more printed features from a reticle using an optical proximity correction (OPC) model that takes into account a reticle design and one or more parameters from a process window of a lithographic process;forming an error function E that measures a deviation between the simulated geometry and a desired design of the one or more printed features, wherein the error function takes into account parameters (p0 . . . pJ) from across the process window in addition to, or in lieu of, a best focus and a best exposure for a stepper used in the lithographic process; andadjusting the reticle design in a way that reduces the deviation as measured by the error function, thereby producing an adjusted reticle design. 2. The method of claim 1 wherein the error function E has the form: E = ∑ p 1 ⁢ ⋯ ⁢ p J ⁢ ⁢ w ⁡ ( p 1 ⁢ ⋯ ⁢ p J ) ⁢ ∑ i ⁢ ⁢ w ⁡ ( x i ) · [ D ⁡ ( x i ) - S ⁡ ( x i , p 1 ⁢ ⋯ ⁢ p J ) ] 2 , ⁢ where w(p1 . . . pJ) are weights dependent on values of the parameters p1 . . . pJ,D(xi) is a desired edge location for a point xi in the simulated geometry,S(xi, p1 . . . pJ) is a simulated edge location for the point xi under conditions determined by the values of the parameters p1 . . . pJ, andw(xi) are weights as functions of position for the point xi. 3. The method of claim 2, wherein each weight w(p1 . . . pJ) has the same value W. 4. The method of claim 3 wherein W=1/N, where N is a total number of values of the parameters p1 . . . pJ. 5. The method of claim 2 wherein each weight w(p1 . . . pJ) is determined by [ ∑ j = 1 J ⁢ ⁢ ( p j - p j ⁢ ⁢ 0 Δ ⁢ ⁢ p j ) 2 ] - 1 ,where each pj is a value of a parameter, pj0 is an optimal value of the parameter pj and Δpj is a value range for the parameter pj. 6. The method of claim 2 wherein the parameters p1 . . . pJ include a focus value and an exposure value. 7. The method of claim 2 wherein the parameters p1 . . . pJ include Film Stack Parameters and/or Resist Parameters, and/or Coat and Prebake Parameters, and/or Imaging Tool Parameters and/or Exposure and Focus Parameters, and/or Post Exposure Bake Parameters, and/or Development Parameters and/or Etch Parameters. 8. The method of claim 7 wherein the Film Stack Parameters include a thickness, one or more Absorption Parameters, a Rate Constant, an Unexposed Refractive Index, and Exposed Refractive Index, a Refractive Index Change on Expose, a Refractive Index Substrate, a Refractive Index Substrate. 9. The method of claim 7 wherein the Resist Parameters include one or more parameters from the group of a Resist Type, a Resist Material, Developer, Resist Thickness, one or more Absorption Parameters, a Rate Constant, Unexposed Refractive Index, Exposed Refractive Index, a Refractive Index Change on Expose, a Thermal Decomposition Activation Energy, a Thermal Decomposition Ln(Ar) (1/sec), a PEB Acid Diffusivity Activation Energy, a PEB Acid Diffusivity Ln(Ar), a PEB Base Diffusivity Activation Energy (kcal/mol), a PEB Base Diffusivity Ln(Ar), an Amplification Reaction Order, an Amplification Reaction Activation Energy, an Amplification Reaction Ln(Ar), a Diffusion-Controlled Reaction Activation Energy, a Diffusion-Controlled Reaction Ln(Ar), an Acid Evaporation Activation Energy, an Acid Evaporation Ln(Ar), a Bulk Acid Loss Activation Energy, a Bulk Acid Loss Ln(Ar), a Relative Quencher Concentration, a Room Temperature Diffusion Length, an Acid Diffusivity Variation, a Reacted/Unreacted Acid Diffusivity Ratio an Exponential Acid Diffusivity Factor, a Base Diffusivity Variation, a Development Rmax, a Development Rmin, a Development Rresin, a Development n, a Development I, a Relative Surface Rate, and an Inhibition Depth. 10. The method of claim 7 wherein the Coat and Prebake Parameters include a Prebake time and/or a prebake Temperature (° C.). 11. The method of claim 7 wherein the Imaging Tool Parameters include one or more of the parameters from the group of a Source Shape, an Illumination Spectrum, a Pupil Filter, Aberrations, Illumination Polarization, Immersion Enabled, Wavelength, Wavelength Range, Numerical Aperture, Reduction Ratio, Flare, Annular Inner Sigma and Annular Outer Sigma. 12. The method of claim 7 wherein the Post Exposure Bake (PEB) Parameters include one or more parameters from the group of PEB Time, PEB Temperature, Contaminant Surface Concentration and Contaminant Diffusion Length. 13. The method of claim 7 wherein the Development Parameters include a Develop Time. 14. The method of claim 7 wherein the Etch Parameters include one or more parameters selected from the group of Number of Etch Stages, Etch Time, Ion Spread, Horizontal Rate, Vertical Rate, Horizontal Rate and Faceting. 15. The method of claim 1 wherein the simulated geometry simulates every edge pixel in the one or more printed features. 16. The method of claim 15 wherein the error function E has the form: E = ∑ p 1 ⁢ ⋯ ⁢ p J ⁢ ⁢ w ⁡ ( p 1 ⁢ ⋯ ⁢ p J ) ⁢ ∫ ⅆ s ⁢ [ D ⁡ ( s ) - S ⁡ ( s , p 1 ⁢ ⋯ ⁢ p J ) ] 2 , ⁢ where p1 . . . pJ are parameters from across the process window, w(p1 . . . pJ) are weights dependent on values of the parameters p1 . . . pJ, D(s) is a desired edge location for a point s in the simulated geometry and S(s, p1 . . . pJ) is a simulated edge location for the point s under conditions determined by the values of the parameters p1 . . . pJ and the integral is taken over all edge pixels in the one or more printed features. 17. The method of claim 15 wherein the error function E has the form: E = ∑ p 1 ⁢ ⋯ ⁢ p J ⁢ ⁢ w ⁡ ( p 1 ⁢ ⋯ ⁢ p J ) ⁢ ∫ ⅆ s · w ⁡ ( s ) ⁢ [ D ⁡ ( s ) - S ⁡ ( s , p 1 ⁢ ⋯ ⁢ p J ) ] 2 ,where p1 . . . pJ are parameters from across the process window, w(p1 . . . pJ) are weights dependent on values of the parameters p1 . . . pJ, w(s) are position-dependent weights, D(s) is a desired edge location for a point s in the simulated geometry andS(s, p1 . . . pJ) is a simulated edge location for the point s under conditions determined by the values of the parameters p1 . . . pJ and the integral is taken over all edge pixels in the one or more printed features. 18. The method of claim 1 wherein forming an error function E includes applying one or more different control layers to the error function wherein each control layer corresponds to a different portion of the reticle design and wherein the error function associated with a particular control layer is adapted to one or more requirements of a corresponding portion of a design to be printed with the reticle. 19. The method of claim 18 wherein the one or more requirements of the corresponding portion of the design include a robustness of printing of the design with respect to variations in process conditions. 20. The method of claim 1 wherein the reticle design includes one or more sub-resolution assist features. 21. The method of claim 1 wherein generating a simulated geometry includes applying one or more mask rules to the OPC model. 22. The method of claim 1 wherein adjusting the reticle design includes fragmenting and moving one or more line segments within a geometry of the reticle design. 23. The method of claim 1 wherein adjusting the reticle design includes performing individual optimizations at a variety of distinct process points and forming a combined correction based on a weighted average of different optimized corrections found to be needed for each of the process points. 24. The method of claim 23, further comprising verifying that the combined correction results in a desired printing of the one or more printed features. 25. An optical proximity correction apparatus, comprising:a processor having logic adapted to implement a method for optical proximity correction, the logic including:an optical proximity correction (OPC) model configured to generate a simulated geometry representing one or more printed features from a reticle using an optical proximity correction (OPC) model that takes into account a reticle design and one or more parameters from a process window of a lithographic process;an error function generator configured to form an error function E that measures a deviation between the simulated geometry and a desired design of the one or more printed features, wherein the error function takes into account parameters (p0 . . . pJ) from across the process window in addition to, or in lieu of, a best focus and a best exposure for a stepper used in the lithographic process; anda design adjustment module configured to adjust the reticle design in a way that reduces the deviation as measured by the error function, thereby producing an adjusted reticle design. 26. The apparatus of claim 25 wherein the error function E has the form: E = ∑ p 1 ⁢ ⋯ ⁢ p J ⁢ ⁢ w ⁡ ( p 1 ⁢ ⋯ ⁢ p J ) ⁢ ∑ i ⁢ ⁢ w ⁡ ( x i ) ⁡ [ D ⁡ ( x i ) - S ⁡ ( x i , p 1 ⁢ ⋯ ⁢ p J ) ] 2 , ⁢ where p1 . . . pJ are parameters from across the process window, w(p1 . . . pJ) are weights dependent on values of the parameters p1 . . . pJ, D(xi) is a desired edge location for a point xi in the simulated geometry w(xi) are weights as functions of position for the point xi,S(xi, p1 . . . pJ) is a simulated edge location for the point xi under conditions determined by the values of the parameters p1 . . . pJ, andw(xi) are weights as functions of position for the point xi. 27. The apparatus of claim 26 wherein the parameters p1 . . . pJ include a focus value and an exposure value. 28. The apparatus of claim 26, wherein each weight w(p1 . . . pJ) has the same value W. 29. The apparatus of claim 28 wherein W=1/N, where N is a total number of values of the parameters p1 . . . pJ. 30. The apparatus of claim 26 wherein each weight w(p1 . . . pJ) is determined by [ ∑ j = 1 J ⁢ ⁢ ( p j - p j ⁢ ⁢ 0 Δ ⁢ ⁢ p j ) 2 ] - 1 ,where each pj is a value of a parameter, pj0 is an optimal value of the parameter pj and Δpj is a value range for the parameter pj. 31. The apparatus of claim 25 wherein the simulated geometry simulates every edge pixel in the one or more printed features. 32. The apparatus of claim 31 wherein the error function E has the form: E = ∑ p 1 ⁢ ⋯ ⁢ p J ⁢ ⁢ w ⁡ ( p 1 ⁢ ⋯ ⁢ p J ) ⁢ ∫ ⅆ s ⁢ [ D ⁡ ( s ) - S ⁡ ( s , p 1 ⁢ ⋯ ⁢ p J ) ] 2 ,where p1 . . . pJ are parameters from across the process window, w(p1 . . . pJ) are weights dependent on values of the parameters p1 . . . pJ, D(s) is a desired edge location for a point s in the simulated geometry andS(s, p1 . . . pJ) is a simulated edge location for the point s under conditions determined by the values of the parameters p1 . . . pJ and the integral is taken over all edge pixels in the one or more printed features. 33. The apparatus of claim 31 wherein the error function E has the form: E = ∑ p 1 ⁢ ⋯ ⁢ p J ⁢ ⁢ w ⁡ ( p 1 ⁢ ⋯ ⁢ p J ) ⁢ ∫ ⅆ s · w ⁡ ( s ) ⁢ [ D ⁡ ( s ) - S ⁡ ( s , p 1 ⁢ ⋯ ⁢ p J ) ] 2 ,where p1 . . . pJ are parameters from across the process window, w(p1 . . . pJ) are weights dependent on values of the parameters p1 . . . pJ, w(s) are position-dependent weights, D(s) is a desired edge location for a point s in the simulated geometry andS(s, p1 . . . pJ) is a simulated edge location for the point s under conditions determined by the values of the parameters p1 . . . pJ and the integral is taken over all edge pixels in the one or more printed features. 34. The apparatus of claim 25 wherein error function generator is configured to apply one or more different control layers to the error function wherein each control layer corresponds to a different portion of the reticle design and wherein the error function associated with a particular control layer is adapted to one or more requirements of a corresponding portion of a design to be printed with the reticle. 35. The apparatus of claim 34 wherein the one or more requirements of the corresponding portion of the design include a robustness requirement for the corresponding portion. 36. The apparatus of claim 25 wherein the reticle design includes one or more sub-resolution assist features. 37. A processor readable medium having embodied therein processor readable instructions including instructions implementing a method for optical proximity correction, the method comprising:generating a simulated geometry representing one or more printed features from a reticle using an optical proximity correction (OPC) model that takes into account a reticle design and one or more parameters from a process window of a lithographic process;forming an error function E that measures a deviation between the simulated geometry and a desired design of the one or more printed features, wherein the error function takes into account parameters (p0 . . . pJ) from across the process window in addition to, or in lieu of, a best focus and a best exposure for a stepper used in the lithographic process;adjusting the reticle design in a way that reduces the deviation as measured by the error function, thereby producing an adjusted reticle design.

054835640

claims

1. In a boiling water reactor fuel bundle, a debris catching grid construction for placement within the flow volume defined by the lower tie plate assembly between the inlet nozzle and upper fuel rod supporting grid comprising: first and second overlying and underlying three dimensional, non-planar perforated plate constructions having side-by-side holes, arranged so that a substantial portion of coolant flowing through said flow volume is caused to change direction between the inlet nozzle and the upper fuel rod supporting grid; each said perforated plate forming a three dimensional construction having a total cross sectional area exceeding the planar cross sectional area of the flow volume of said lower tie plate between said inlet nozzle and said rod supporting grid; said underlying plate having larger holes than said overlying plate; means for mounting each said three dimensional perforated plate construction interiorly of the flow volume of said lower tie plate such that debris passing through the larger holes of the underlying plate will be trapped between the first overlying plate and the second underlying plate. said sidewalls of said overlying and underlying three dimensional grid construction are corrugated. a lower tie plate assembly including a fuel rod supporting grid, an inlet nozzle, and sidewall extending between said nozzle to the edges of said grid to define therebetween a flow volume interior of said tie plate; a plurality of upstanding fuel rods, said fuel rods supported on said rod supporting grid and extending in upstanding vertical side-by-side relation; an upper tie plate for supporting at least some of fuel rods and providing connection to said lower tie plate through at least some of said fuel rods; first and second overlying and underlying three dimensional, non-planar perforated plate constructions having side-by-side holes, arranged so that a substantial portion of coolant flowing through said flow volume is caused to change direction between the inlet nozzle and the upper fuel rod supporting grid; each said perforated plate forming a three dimensional construction having a total cross sectional area exceeding the planar cross sectional area of the flow volume of said lower tie plate between said inlet nozzle and said rod supporting grid, said underlying plate having larger holes than said overlying plate; means mounting each said three dimensional perforated plate construction interiorly of the flow volume of said lower tie plate, such that debris passing through the larger holes of the underlying plate will be trapped between the first overlying plate and the second underlying plate. said sidewalls of said overlying and underlying three dimensional grid construction are corrugated. 2. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 1 and wherein 3. In a boiling water reactor fuel bundle, comprising in combination: 4. In a boiling water reactor fuel bundle according to claim 3 and wherein:

claims

1. A method of manufacturing a collimator comprising: providing a plate-like body; coating a predetermined portion of a surface of the body with an x-ray attenuating material; and machining at least one collimating slit through the coating and the plate-like body. 2. A method according to claim 1 , further comprising machining mounting apertures in the plate-like body between an outer periphery of the coating and an outer periphery of the body. claim 1 3. A method according to claim 1 , wherein the coating is provided using a thermal spray process. claim 1 4. A method according to claim 3 , wherein the coating is provided using a plasma thermal spray process. claim 3 5. A method according to claim 1 , wherein the collimating slit is provided using a wire EDM process. claim 1 6. A collimater manufactured by a method according to claim 1 . claim 1 7. A method of manufacturing a collimator comprising: providing a plate-like body; coating a predetermined portion of a surface of the body with an x-ray absorbing material; and machining at least one collimating slit through the coating and the plate-like body. 8. A method according to claim 7 , further comprising machining mounting apertures in the plate-like body between an outer periphery of the coating and an outer periphery of the body. claim 7 9. A method according to claim 7 , wherein the coating is provided using a thermal spray process. claim 7 10. A method according to claim 9 , wherein the coating is provided using a plasma thermal spray process. claim 9 11. A method according to claim 7 , wherein the collimating slit is provided using a wire EDM process. claim 7 12. A collimater manufactured by a method according to claim 7 . claim 7

summary

claims

1. An apparatus, comprising:a first energy transfer system configured to divert a first selected portion of energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir;an additional energy transfer system configured to divert at least one additional selected portion of energy from a portion of at least one additional nuclear reactor system of the plurality of nuclear reactor systems to the at least one auxiliary thermal reservoir; andat least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 2. The apparatus of claim 1, wherein the first energy transfer system configured to divert a first selected portion of energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir. 3. The apparatus of claim 2, wherein the at least one energy transfer system configured to divert a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one heat transfer system. 4. The apparatus of claim 3, wherein the at least one heat transfer system configured to divert a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one heat transfer system configured to divert a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir, the portion of the first nuclear reactor in thermal communication with at least one heat source of the first nuclear reactor system. 5. The apparatus of claim 4, wherein the at least one heat transfer system configured to divert a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir, the portion of the first nuclear reactor in thermal communication with at least one heat source of the first nuclear reactor system, comprises:at least one heat transfer system configured to divert a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir, the portion of the first nuclear reactor system in thermal communication with at least one nuclear reactor core of the first nuclear reactor system. 6. The apparatus of claim 5, wherein the at least one heat transfer system configured to divert a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir, the portion of the first nuclear reactor system in thermal communication with at least one nuclear reactor core of the first nuclear reactor system, comprises:at least one heat transfer system configured to divert a first selected portion of thermal energy from a portion of at least one primary coolant system of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir. 7. The apparatus of claim 3, wherein the at least one heat transfer system comprises:at least one direct fluid exchange heat transfer system. 8. The apparatus of claim 7, wherein the at least one direct fluid exchange heat transfer system comprises:at least one direct fluid exchange heat transfer system configured to intermix at least one reservoir fluid of at least one auxiliary thermal reservoir with at least one coolant of a first nuclear reactor system of a plurality of nuclear reactor systems. 9. The apparatus of claim 3, wherein the at least one heat transfer system includes at least one heat exchanger. 10. The apparatus of claim 1, wherein the first energy transfer system configured to divert a first selected portion of energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert a first selected portion of electrical energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir. 11. The apparatus of claim 10, wherein the at least one energy transfer system configured to divert a first selected portion of electrical energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one electrical-to-thermal conversion system configured to divert a first selected portion of electrical energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir. 12. The apparatus of claim 11, wherein the at least one electrical-to-thermal conversion system configured to divert a first selected portion of electrical energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one resistive heating device. 13. The apparatus of claim 1, wherein the at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply at least a portion of thermal energy from a first auxiliary thermal reservoir and a portion of thermal energy from at least a second thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 14. The apparatus of claim 1, wherein the at least one heat supply system includes at least one heat exchange loop. 15. The apparatus of claim 1, wherein the at least one heat supply system includes at least one heat exchange pipe. 16. The apparatus of claim 1, wherein the at least one heat supply system includes at least one heat exchanger. 17. The apparatus of claim 1, wherein the at least one heat supply system includes at least one thermoelectric device. 18. The apparatus of claim 1, wherein the at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one boiling loop of at least one nuclear reactor system of the plurality of nuclear reactor systems. 19. The apparatus of claim 1, wherein the at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one turbine of at least one nuclear reactor system of the plurality of nuclear reactor systems. 20. The apparatus of claim 19, wherein the at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one turbine of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one working fluid of at least one turbine of at least one nuclear reactor system of the plurality of nuclear reactor systems. 21. The apparatus of claim 1, wherein the at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one low grade heat dump. 22. The apparatus of claim 1, wherein the at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one topping cycle. 23. The apparatus of claim 1, wherein the at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one bottoming cycle. 24. The apparatus of claim 1, further comprising:at least one supplementary energy transfer system configured to supplement the at least one auxiliary thermal reservoir with an additional portion of thermal energy from at least one additional energy source. 25. The apparatus of claim 1, wherein the first energy transfer system configured to divert a first selected portion of energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert, responsive to at least one condition, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir. 26. The apparatus of claim 25, wherein the at least one energy transfer system configured to divert, responsive to at least one condition, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert, responsive to at least one condition of a first nuclear reactor system of a plurality of nuclear reactor systems, a first selected portion of thermal energy from a portion of the first nuclear reactor system of the plurality of nuclear reactor systems to at least one auxiliary thermal reservoir. 27. The apparatus of claim 25, wherein the at least one energy transfer system configured to divert, responsive to at least one condition, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert, responsive to at least one condition of at least one additional nuclear reactor system of a plurality of nuclear reactor systems, a first selected portion of thermal energy from a portion of the first nuclear reactor system of the plurality of nuclear reactor systems to at least one auxiliary thermal reservoir. 28. The apparatus of claim 25, wherein the at least one energy transfer system configured to divert, responsive to at least one condition, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert, responsive to determination of excess capacity of at least one nuclear reactor system of a plurality of nuclear reactor systems, a first selected portion of thermal energy from a portion of a first nuclear reactor system of the plurality of nuclear reactor systems to at least one auxiliary thermal reservoir. 29. The apparatus of claim 25, wherein the at least one energy transfer system configured to divert, responsive to at least one condition, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert, responsive to at least one operation system of at least one nuclear reactor system of a plurality of nuclear reactor systems, a first selected portion of thermal energy from a portion of a first nuclear reactor system of the plurality of nuclear reactor systems to at least one auxiliary thermal reservoir. 30. The apparatus of claim 25, wherein the at least one energy transfer system configured to divert, responsive to at least one condition, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert, responsive to at least one reservoir operation system of at least one auxiliary thermal reservoir, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to the at least one auxiliary thermal reservoir. 31. The apparatus of claim 25, wherein the at least one energy transfer system configured to divert, responsive to at least one condition, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert, responsive to at least one signal from at least one operator of at least one nuclear reactor system of a plurality of nuclear reactor systems, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir. 32. The apparatus of claim 25, wherein the at least one energy transfer system configured to divert, responsive to at least one condition, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert, upon a pre-selected diversion start time, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir. 33. The apparatus of claim 25, wherein the at least one energy transfer system configured to divert, responsive to at least one condition, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert, responsive to a shutdown event of at least one nuclear reactor system of a plurality of nuclear reactor systems, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir. 34. The apparatus of claim 25, wherein the at least one energy transfer system configured to divert, responsive to at least one condition, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert, responsive to determination of the amount of energy stored in at least one auxiliary thermal reservoir, a first selected portion of thermal energy from a portion of the first nuclear reactor system of the plurality of nuclear reactor systems to the at least one auxiliary thermal reservoir. 35. The apparatus of claim 25, wherein the at least one energy transfer system configured to divert, responsive to at least one condition, a first selected portion of thermal energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert, responsive to determination of the amount of available energy storage capacity of at least one auxiliary thermal reservoir, a first selected portion of thermal energy from a portion of the first nuclear reactor system of the plurality of nuclear reactor systems to the at least one auxiliary thermal reservoir. 36. The apparatus of claim 1, wherein the at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of the first nuclear reactor system of the plurality of nuclear reactor systems. 37. The apparatus of claim 1, wherein the at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of the at least one additional nuclear reactor system of the plurality of nuclear reactor systems. 38. The apparatus of claim 1, wherein the at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply, responsive to at least one condition, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 39. The apparatus of claim 38, wherein the at least one heat supply system configured to supply, responsive to at least one condition, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply, responsive to at least one condition of at least one nuclear reactor system of the plurality of nuclear reactor systems, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 40. The apparatus of claim 39, wherein the at least one heat supply system configured to supply, responsive to at least one condition of at least one nuclear reactor system of the plurality of nuclear reactor systems, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply, responsive to heightened power demand on at least one nuclear reactor system of the plurality of nuclear reactor systems, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 41. The apparatus of claim 38, wherein the at least one heat supply system configured to supply, responsive to at least one condition, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply, responsive to at least one one operation system of at least one nuclear reactor system of the plurality of nuclear reactor systems, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 42. The apparatus of claim 38, wherein the at least one heat supply system configured to supply, responsive to at least one condition, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply, responsive to at least one reservoir operation system of the at least one auxiliary thermal reservoir, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 43. The apparatus of claim 38, wherein the at least one heat supply system configured to supply, responsive to at least one condition, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply, responsive to at least one operator of at least one nuclear reactor system of the plurality of nuclear reactor systems, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 44. The apparatus of claim 38, wherein the at least one heat supply system configured to supply, responsive to at least one condition, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply, responsive to a shutdown event of at least one nuclear reactor system of the plurality of nuclear reactor systems, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 45. The apparatus of claim 38, wherein the at least one heat supply system configured to supply, responsive to at least one condition, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply, upon a pre-selected supply start time, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 46. The apparatus of claim 38, wherein the at least one heat supply system configured to supply, responsive to at least one condition, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply, responsive to determination of the amount of energy stored in at least one auxiliary thermal reservoir, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 47. The apparatus of claim 38, wherein the at least one heat supply system configured to supply, responsive to at least one condition, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply, responsive to determination of the amount of available energy storage capacity of at least one auxiliary thermal reservoir, at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 48. The apparatus of claim 1, wherein the at least one heat supply system configured to supply at least a portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems comprises:at least one heat supply system configured to supply a specified portion of thermal energy from the at least one auxiliary thermal reservoir to at least one energy conversion system of at least one nuclear reactor system of the plurality of nuclear reactor systems. 49. The apparatus of claim 1, further comprising:at least one reservoir monitoring system configured to monitor at least one condition of the at least one auxiliary thermal reservoir. 50. The apparatus of claim 49, wherein the at least one reservoir monitoring system comprises:at least one reservoir temperature monitoring system. 51. The apparatus of claim 49, wherein the at least one reservoir monitoring system comprises:at least one reservoir pressure monitoring system. 52. The apparatus of claim 49, wherein the at least one reservoir monitoring system configured to monitor at least one condition of the at least one auxiliary thermal reservoir comprises:at least one reservoir monitoring system configured to determine the amount of energy stored in the at least one auxiliary thermal reservoir. 53. The apparatus of claim 49, wherein the at least one reservoir monitoring system configured to monitor at least one condition of the at least one auxiliary thermal reservoir comprises:at least one reservoir monitoring system configured to determine the amount of available energy storage capacity in the at least one auxiliary thermal reservoir. 54. The apparatus of claim 1, wherein the first energy transfer system configured to divert a first selected portion of energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to at least one auxiliary thermal reservoir comprises:at least one energy transfer system configured to divert a first selected portion of energy from a portion of a first nuclear reactor system of a plurality of nuclear reactor systems to a mass of at least one heat storage material of at least one auxiliary thermal reservoir. 55. The apparatus of claim 54, wherein the at least one heat storage comprises:at least one solid heat storage material. 56. The apparatus of claim 54, wherein the at least one heat storage comprises:at least one liquid heat storage material. 57. The apparatus of claim 54, wherein the at least one heat storage comprises:at least one pressurized gaseous heat storage material. 58. The apparatus of claim 54, wherein the at least one heat storage comprises:at least one mixed phase heat storage material. 59. The apparatus of claim 54, wherein the mass of at least one heat storage comprises:at least one material having a phase transition within the operating temperature of the at least one auxiliary thermal reservoir. 60. The apparatus of claim 54, wherein the mass of at least one heat storage comprises:at least one heat storage material contained in a reservoir containment system. 61. The apparatus of claim 60, wherein the reservoir containment system comprises:at least one external vessel. 62. The apparatus of claim 60, wherein the reservoir containment system comprises:at least one external liquid pool. 63. The apparatus of claim 1, wherein the at least one auxiliary thermal reservoir comprises:at least one auxiliary thermal reservoir configured to store the selected portion of energy in the form of a temperature change in at least one heat storage material of the auxiliary thermal reservoir. 64. The apparatus of claim 1, wherein the at least one auxiliary thermal reservoir comprises:at least one auxiliary thermal reservoir configured to store the selected portion of energy in the form of a phase change in at least one heat storage material of the auxiliary thermal reservoir. 65. The apparatus of claim 1, further comprising:at least one reservoir temperature control system configured to maintain the temperature of at least one heat storage material of at least one auxiliary thermal reservoir above a selected temperature. 66. The apparatus of claim 1, wherein the first nuclear reactor system of a plurality of nuclear reactor systems comprises:a nuclear reactor system having at least one liquid coolant. 67. The apparatus of claim 1, wherein the first nuclear reactor system of a plurality of nuclear reactor systems comprises:a nuclear reactor system having at least one pressurized gas coolant. 68. The apparatus of claim 1, wherein the first nuclear reactor system of a plurality of nuclear reactor systems comprises:a nuclear reactor system having at least one mixed phase coolant. 69. The apparatus of claim 1, wherein the first nuclear reactor system of a plurality of nuclear reactor systems comprises:a nuclear reactor system having a thermal spectrum nuclear reactor. 70. The apparatus of claim 1, wherein the first nuclear reactor system of a plurality of nuclear reactor systems comprises:a nuclear reactor system having a fast spectrum nuclear reactor. 71. The apparatus of claim 1, wherein the first nuclear reactor system of a plurality of nuclear reactor systems comprises:a nuclear reactor system having a multi-spectrum nuclear reactor. 72. The apparatus of claim 1, wherein the first nuclear reactor system of a plurality of nuclear reactor systems comprises:a nuclear reactor system having a breeder nuclear reactor. 73. The apparatus of claim 1, wherein the first nuclear reactor system of a plurality of nuclear reactor systems comprises:a nuclear reactor system having a traveling wave nuclear reactor.

050230484

summary

FIELD OF THE INVENTION The invention relates to a rod for a fuel assembly of a nuclear reactor having improved resistance to corrosion and wear. BACKGROUND OF THE INVENTION Fuel assemblies of water-cooled nuclear reactors and in particular pressurized water nuclear reactors comprise a framework in which are introduced fuel rods constituted by a sheath enclosing a nuclear fuel material, such as uranium or plutonium oxide in the form of sintered pellets. The sheath constructed from a tube of zirconium alloy must have good resistance to corrosion under the effect of the primary fluid circulating in contact with the outer surface of the sheath. For forming the sheath of fuel rods of assemblies of water-cooled reactors there is usually employed alloy including principally 1.2 to 1.7% tin, 0.18 to 0.24% iron and 0.07 to 0.13% chromium or a zirconium alloy including 1.2 to 1.7% tin, 0.07 to 0.2% iron, 0.05 to 0.15% chromium and 0.03 to 0.08% nickel. In order to improve the performances as concerns corrosion under irradiation of the sheaths of fuel rods in the environment of the nuclear reactor in operation and thereby prolong the life of the fuel assemblies in the core, there have been proposed modifications or adjustments in the composition of the aforementioned zirconium alloys or replacements by alloys including elements such as vanadium, niobium or copper. However, these alloys do not present decisive advantages over currently employed alloys whose composition is mentioned hereinbefore, in that their mechanical characteristics and in particular their hardness and their resistance to wear are usually lower than those of the currently employed compositions. In addition to the corrosion of their outer surface exposed to the cooling fluid of the nuclear reactor, the sheaths undergo internal corrosion due in particular to the interaction between the fuel pellets and the inner surface of the sheath. In order to reduce this internal corrosion, it has been proposed to deposit a layer of insulation between the pellets and the sheath. It has also been proposed in patent application EP-A-0,212,351 to construct the sheath in the form of a duplex tube comprising a tubular inner layer of zirconium alloy of the conventional type such as described hereinbefore and a surface layer improving the resistance to corrosion of the sheath composed of zirconium alloy different from the alloy constituting the inner layer and including iron and at least one of the elements vanadium, platinum and copper. This surface layer, whose thickness represents 1 to 20% of the total thickness of the wall of the sheath, may be produced by extrusion of a blank constituted by an inner tube of zirconium alloy of conventional composition on which is mounted an outer tube having the composition of the surface layer. The sheath is then rolled in a step-by-step rolling mill down to its definitive diameter. The fuel rods, whose sheath is constituted by a duplex tube, present a generalized outer corrosion resistance in the environment of the nuclear reactor which is distinctly improved. However, the hardness and the resistance to wear of the surface layer are lower than those of sheaths of alloy of conventional type. Consequently, when loading a fuel assembly with new rods or when replacing rods in a worn fuel assembly, the sheaths of the rods undergo, on their outer surface, increased wear which may result in defects and increased local corrosion. SUMMARY OF THE INVENTION An object of the invention is therefore to provide a rod for a fuel assembly of a nuclear reactor containing a nuclear fuel material, inside a sheath comprising an inner tubular layer and a surface or outer layer of zirconium alloys which are different from each other, said rod having a resistance to external corrosion and to wear which is distinctly improved both with respect to rods whose sheath is constituted by a homogeneous tube of zirconium alloy of conventional type and with respect to rods having a sheath constituted by a duplex tube. For this purpose, the surface or outer layer having a thickness of between 10 and 25% of the total thickness of the wall of the sheath is constituted by a zirconium-base alloy containing 0.35 to 0.65% by weight tin, 0.20 to 0.65% iron, 0.09 to 0.16% oxygen and niobium in a proportion of 0.35 to 0.65% or vanadium in a proportion of 0.25 to 0.35%. The invention also relates to a fuel rod whose sheath comprises an inner tubular layer constituted by a zirconium alloy including 0.8 to 1.2% niobium and a surface or outer layer according to the principal characteristic of the invention.

claims

1. A nuclear fuel assembly for a boiling water reactor comprising:a bundle of fuel rods comprising a set of fuel rods, the fuel rods of the set of fuel rods being arranged at the nodes of a first lattice having a non-uniform distribution of nodes at a lowermost end of the fuel assembly, the fuel rods of the set of fuel rods being arranged at the nodes of a second lattice having a uniform distribution of nodes at an uppermost end of the fuel assembly, the second lattice having the uniform distribution of nodes including the fuel rods of the set arranged at nodes of the second lattice with a same spacing between each pair of adjacent nodes, the first lattice having the non-uniform distribution of nodes including the fuel rods of the set arranged at nodes of the first lattice with at least two different spacings between pairs of adjacent nodes. 2. The nuclear fuel assembly as in claim 1, wherein the spacings between the fuel rods of the set vary monotonously along the length of the fuel assembly. 3. The nuclear fuel assembly as in claim 1, wherein, in the lowermost section, the fuel rods of the set of fuel rods are arranged in groups separated by coolant/moderator gaps. 4. The nuclear fuel assembly as in claim 3, wherein the fuel rods of each group are with a uniform pitch between the fuel rods of said group. 5. The nuclear fuel assembly as in claim 3, wherein the coolant/moderator gaps are wider than passages between the fuel rods or rows of fuel rods of each group. 6. The nuclear fuel assembly as in claim 3, wherein the coolant/moderator gaps include at least one coolant/moderator gap extending substantially radially from a central region of the bundle of fuel rods towards the periphery thereof. 7. The nuclear fuel assembly as in claim 3, wherein the groups including a central group and a peripheral group surrounding the central group, the coolant/moderator gaps including a coolant/moderator gap between the central group and the peripheral group. 8. The nuclear fuel assembly as in claim 3, wherein the coolant/moderator gaps include at least two coolant/moderator gaps extending parallel to each other. 9. The nuclear fuel assembly as in claim 1 further comprising at least one tubular water channel. 10. The nuclear fuel assembly as in claim 9 further comprising at least one coolant/moderator gap, the at least one tubular water channel being surrounded by the at least one coolant/moderator gap. 11. The nuclear fuel assembly as in claim 9, wherein the at least one tubular water channel is of constant cross section along the length of the fuel assembly. 12. The nuclear fuel assembly as in claim 1, wherein the bundle of fuel rods includes at least one individual fuel rod which is offset at least one of from the first lattice in the lowermost section and from the second lattice in the uppermost section of the fuel assembly. 13. The nuclear fuel assembly as in claim 1, wherein a transition zone between the lowermost section with a non-uniform pitch towards the uppermost section with a uniform pitch is positioned at a height comprised between 30% and 70% of the height of an active zone of the fuel assembly. 14. The nuclear fuel assembly as in claim 1, wherein all the fuel rods are full-length fuel rods. 15. The nuclear fuel assembly as in claim 3, wherein the fuel rods of each group are in a square or rectangular lattice arrangement. 16. A nuclear fuel assembly for a boiling water reactor comprising:a bundle of fuel rods comprising a set of fuel rods arranged in a first lattice having a non-uniform pitch in a lowermost section of the fuel assembly and arranged in a second lattice with a uniform pitch in an uppermost section of the fuel assembly,a transition zone between the lowermost section with a non-uniform pitch towards the uppermost section with a uniform pitch is positioned at a height comprised between 30% and 70% of the height of an active zone of the fuel assembly.

062947893

claims

1. A radiation intensifying screen comprising: a first radiation absorbing, luminescent layer formed from a first luminescing material capable of producing a spectral emissions maximum at first predetermined wavelength in response to incident radiation; a second radiation absorbing, luminescent layer formed from a second luminescing material capable of producing a spectral emissions maximum at a second predetermined wavelength which is different from the first predetermined wavelength range in response to incident radiation; and means, disposed between the first and second luminescent layers, for reflecting incident spectral emissions emanating from the first luminescent layer at the first predetermined wavelength and for allowing spectral emissions emanating from the second luminescent layer at the second predetermined wavelength to pass therethrough. a first radiation absorbing, luminescent layer formed from a first luminescing material capable of producing spectral emissions of varying wavelengths in a first wavelength range in response to incident radiation; a second radiation absorbing, luminescent layer formed from a second luminescing material capable of producing spectral emissions of varying wavelengths in a second wavelength range which is greater than the first wavelength range in response to incident radiation; and a reflective-transmissive layer disposed between the first and second luminescent layers, wherein the reflective-transmissive layer is adapted to reflect incident spectral emissions of varying wavelengths emanating from the first luminescent layer which are less than a cutoff wavelength of the reflective-transmissive layer, wherein the reflective-transmissive layer is also adapted to allow spectral emissions of varying wavelengths emanating from the second luminescent layer which are greater than the cutoff wavelength of the reflective-transmissive layer to pass therethrough. a first radiation absorbing, luminescent layer formed from a first luminescing material capable of producing spectral emissions of varying wavelengths in a first wavelength range in response to incident radiation; a second radiation absorbing, luminescent layer formed from a second luminescing material capable of producing spectral emissions of varying wavelengths in a second wavelength range, which is less than the first wavelength range, in response to incident radiation; and a reflective-transmissive layer disposed between the first and second luminescent layers, wherein the reflective-transmissive layer is adapted to reflect incident spectral emissions of varying wavelengths emanating from the first luminescent layer which are greater than a cutoff wavelength of the reflective-transmissive layer, wherein the reflective-transmissive layer is also adapted to allow spectral emissions of varying wavelengths emanating from the second luminescent layer which are lower than the cutoff wavelength of the reflective-transmissive layer to pass therethrough. 2. The intensifying screen of claim 1, further comprising a backing layer disposed adjacent to the second luminescent layer. 3. The intensifying screen of claim 2, further comprising means, disposed between the second luminescent layer and the backing layer, for reflecting incident spectral emissions emanating from the second luminescent layer at the second predetermined wavelength. 4. The intensifying screen of claim 1, wherein the first predetermined wavelength is less than the second predetermined wavelength, and wherein the means disposed between the first and second luminescent layers is a long pass filter. 5. The intensifying screen of claim 1, wherein the first predetermined wavelength is greater than the second predetermined wavelength, and wherein the means disposed between the first and second luminescent layers is a short pass filter. 6. The intensifying screen of claim 1, further comprising a protective layer disposed over the first luminescent layer. 7. The intensifying screen of claim 1, further comprising a charge coupled device and means for optically coupling spectral emissions emanating from the first and second luminescent layers to the charge coupled device, wherein the coupling means is disposed between the charge coupled device and the first luminescent layer. 8. The intensifying screen of claim 7, wherein the means for optically coupling spectral emissions is a plurality of optical fibers. 9. A radiation intensifying screen comprising: 10. The intensifying screen of claim 9, further comprising a backing layer disposed adjacent to the second luminescent layer. 11. The intensifying screen of claim 10, further comprising a secondary reflective layer disposed between the second luminescent layer and the backing layer, wherein the secondary reflective layer is adapted to reflect spectral emissions of varying wavelengths emanating from the second luminescent layer. 12. The intensifying screen of claim 9, further comprising a protective layer disposed over the first luminescent layer. 13. The intensifying screen of claim 9, further comprising a charge coupled device imager and means for optically coupling spectral emissions emanating from the first and second luminescent layers to the charge coupled device, wherein the coupling means is disposed between the charge coupled device and the first luminescent layer. 14. The intensifying screen of claim 13, wherein the means for optically coupling spectral emissions is a plurality of optical fibers. 15. A radiation intensifying screen comprising: 16. The intensifying screen of claim 15, further comprising a backing layer disposed adjacent to the second luminescent layer. 17. The intensifying screen of claim 16, further comprising a secondary reflective layer disposed between the second luminescent layer and the backing layer, wherein the secondary reflective layer is adapted to reflect spectral emissions of varying wavelengths emanating from the second luminescent layer. 18. The intensifying screen of claim 15, further comprising a protective layer disposed over the first luminescent layer. 19. The intensifying screen of claim 15, further comprising a charge coupled device and means for optically coupling spectral emissions emanating from the first and second luminescent layers to the charge coupled device, wherein the coupling means is disposed between the charge coupled device and the first luminescent layer. 20. The intensifying screen of claim 19, wherein the means for optically coupling spectral emissions is a plurality of optical fibers.

055127592

abstract

The present invention relates generally to the field of condensers for collecting light from a synchrotron radiation source and directing the light into a ringfield of a lithography camera. The present invention discloses a condenser comprising collecting, processing, and imaging optics. The collecting optics are comprised of concave and convex spherical mirrors that collect the light beams. The processing optics, which receive the light beams, are comprised of flat mirrors that converge and direct the light beams into a real entrance pupil of the camera in a symmetrical pattern. In the real entrance pupil are located flat mirrors, common to the beams emitted from the preceding mirrors, for generating substantially parallel light beams and for directing the beams toward the ringfield of a camera. Finally, the imaging optics are comprised of a spherical mirror, also common to the beams emitted from the preceding mirrors, images the real entrance pupil through the resistive mask and into the virtual entrance pupil of the camera. Thus, the condenser is comprised of a plurality of beams with four mirrors corresponding to a single beam plus two common mirrors.

abstract

An X-ray analyzing system for x-ray scattering analysis having an x-ray source for generating a beam of x-rays propagating along a transmission axis (3), at least one hybrid slit (5b) with an aperture which defines the shape of the cross section of the beam, a sample on which the beam shaped by the hybrid slit (5b) is directed and an X-ray detector for detecting x-rays originating from the sample. The hybrid slit (5b) has at least three hybrid slit elements (7), each hybrid slit element (7) having a single crystal substrate (8) bonded to a base (9) with a taper angle α≠0. The single crystal substrates (8) of the hybrid slit elements (7) limit the aperture and the hybrid slit elements (7) are staggered with an offset along the transmission axis (3). The X-ray analyzing system has improved resolution and signal to noise ratio.

abstract

Methods and systems for non-intrusively detecting the existence of fissile materials in a container via the measurement of energetic prompt neutrons are disclosed. The methods and systems use the unique nature of the prompt neutron energy spectrum from neutron-induced fission arising from the emission of neutrons from almost fully accelerated fragments to unambiguously identify fissile material. These signals from neutron-induced fission are unique and allow the detection of any material in the actinide region of the nuclear periodic table.

051606941

claims

1. Fusion reactor comprising a reaction zone, a magnetic field with magnetic flux lines surrounding the reaction zone, the magnetic flux lines being curved convexly seen from the reaction zone in the nearer surrounding of the reaction zone, an electric potential pot formed by an electric field surrounding the reaction zone for conversion of kinetic energy of ionized reactants escaping from the reaction zone into potential energy thereof and for subsequent return of the ionized reactants into the reaction zone with reconversion of their potential energy into kinetic energy, an ion source in an upper area of the electric potential pot distributed over a ringlike-shaped area surrounding the reaction zone, wherein the reaction zone is positioned in a center region of the electric potential pot surrounding the reaction zone, the portions of the magnetic flux lines extending within the electric potential pot in the region between the upper area of the electric potential pot and the reaction zone run substantially perpendicularly to equipotential lines of the electric field forming the electric potential pot, and the electric potential pot comprises at least an electrode in its upper area and at least an electrode in its bottom area in the nearer surrounding of the reaction zone being heated to a temperature within an upper part of the temperature range of liquidity of lithium. 2. Fusion reactor according to claim 1 wherein to the upper area of the potential pot ionized reactants are supplied and accelerated by the potential difference between the electrodes in the upper and the bottom area of the potential pot up to a kinetic energy sufficient for fusion and upon not meeting another reactant in the reaction zone pass the center at a high speed corresponding to their kinetic energy and at the opposite side of the potential pot to their supply side again run against the potential difference at a decreasing speed towards the upper area of the potential pot until their kinetic energy, shortly before reaching the electrode in the upper area of the potential pot, is again converted into potential energy, so that the process of accelerated movement towards the bottom area of the potential pot and the subsequent decelerated movement towards the upper area of the potential pot may be repeated any number of times up to a fusion reaction in the reaction zone and consequently a large portion of the reactants supplied to the upper area of the potential pot may be brought into fusion reaction. 3. Fusion reactor according to claim 1 comprising means for supplying the reactor with a reaction gas consisting at least partially of deuterium and for ionizing and supplying said gas to the reactor in the upper area of the potential pot. 4. Fusion reactor according to claim 3 wherein the means for ionizing and supplying the reaction gas to the reactor comprise a glow discharge chamber in the upper area of the potential pot being provided for supplying ionized reactants to the potential pot in form of canal rays, with a cathode designed in the manner of a Lenard tube and comprising a metal film being permeable to the canal rays. 5. Fusion reactor according to claim 4 comprising means for generating a so-called Berghaus current-intensive glow discharge in the glow discharge chamber. 6. Fusion reactor according to claim 1 wherein the electric potential pot has substantially the form of a rotationally symmetrical cavity having a cross-section substantially in the form of two opposing sectors of a circle, with the cusps of the two sectors which form the cross-section coinciding with the axis of symmetry of the rotationally symmetrical cavity and a median dividing said two sectors each into two identical parts standing vertically on said axis of symmetry and said upper area of the electric potential pot lying in the region of the arc of the sectors. 7. Fusion reactor according to claim 6 wherein the apex angle of the sectors is between 10.degree. and 80.degree.. 8. Fusion reactor according to claim 6 comprising at the substantially cone-shaped side surfaces of the rotationally symmetrical cavity spatially defining the electric potential pot, means for lateral electric screening of the potential pot as well as for achieving a potential profile along the screening which is higher than or approximately the same as the potential profile along said median depending upon the distance from the potential pot center. 9. Fusion reactor according to claim 8 wherein the means for screening and for achieving said potential profile comprise stacked rings consisting of an electrically conducting material, each of which being substantially in the shape of a short truncated cone and fits on top of the preceding ring in the stack in such a way that the ring edges of all the stacked rings together define at one side one of said substantially cone-shaped side surfaces of the rotationally symmetrical cavity. 10. Fusion reactor according to claim 9 wherein the rings are electrically insulated from one another, by means of electrically non-conducting coatings and are individually connected to direct voltage sources each supplying the intended potential of the ring. 11. Fusion reactor according to claim 9 wherein the rings are electrically connected to one another by high-resistance resistors formed by electrically poorly conducting coatings and means are provided for generating a current flowing through the stack and producing at the high-resistance resistors the voltage drops required for said potential profile. 12. Fusion reactor according to claim 1 comprising, for generating the magnetic field surrounding the reaction zone, two coils with a substantially triangular winding cross-section disposed coaxially to the reaction zone and to the potential pot on either side of the reaction zone and the potential pot, with coil currents of at least approximately the same magnitude flowing in opposite directions through said coils. 13. Fusion reactor according to claim 12, comprising, for increasing the magnetic field strength in the reaction zone and in particular between the reaction zone and the material walls surrounding it, a substantially hollow sphere-shaped reactor shell enclosing the coils and the potential pot and consisting of a ferromagnetic material one side of the substantially triangular winding cross-section of the coils being adjacent to the reactor shell inner wall and extending approximately parallel thereto, and a linear extension of the median between the other two sides of the triangular winding cross-section extending through the center of the reaction zone. 14. Fusion reactor according to claim 12 wherein the coils are superconducting coils comprising tubular windings with a cooling medium formed by a liquefied gas flowing through the windings and keeping the current-conduction walls of said tubular windings at a temperature within the superconductivity range of the material of said walls, comprising means for supplying the cooling medium to the coils and heat insulating means for each of the two coils. 15. Fusion reactor according to claim 12 wherein the substantially triangular winding cross-section of the coils has substantially the form of an equilateral triangle and the windings of the coils are formed by tubular conductors whose line cross-section likewise has the external shape of an equilateral triangle, and wherein the median between the two triangle sides, pointing approximately toward the reaction zone, of the substantially triangular winding cross-section of the coils makes an angle in the region of 30.degree. to 55.degree., with the axis of the coaxially arranged coils. 16. Fusion reactor according to claim 1 comprising, for capture and chemonuclear conversion of neutrons liberated in nuclear fusion reactions, a blanket surrounding the reaction zone and the potential pot in which liquid blanket lithium flows from a storage tank, disposed in the region of the upper area of the potential pot and covering the potential pot in this region, along the side surfaces of the potential pot into the region surrounding the reaction zone and from there approximately in the direction of the axis of reaction zone and potential pot into a collecting tank, and wherein the collecting tank is connected to the storage tank over a tritium stripper and a first heat exchanger and a lithium pump for circulating the liquid lithium through the blanket. 17. Fusion reactor according to claim 16 wherein the flow cross-section for the liquid lithium is at least approximately constant in the portions of the blanket extending along the side surfaces of the potential pot and approximately in the direction of the axis of reaction zone and potential pot in order to achieve a substantially constant flow rate of the lithium in said portions of the blanket and wherein the width of the, in said portions of the blanket, annular flow cross-section is for this purpose at least approximately inversely proportional to the mean diameter of the annular flow cross-section or to the mean distance of the flow cross-section from the axis of reaction zone and potential pot. 18. Fusion reactor according to claim 16 wherein the first heat exchanger gives up its heat to a potassium circuit passing through a second heat exchanger and a potassium turbine and the potassium turbine drives a first generator for generating electric energy. 19. Fusion reactor according to claim 18 wherein the second heat exchanger gives up its heat to a water/steam circuit passing through a steam turbine and a condenser and a pump and the steam turbine drives a second generator for generating electric energy. 20. Fusion reactor according to claim 1 comprising means for supplying reactants to the reaction zone and for discharging reaction products and excess reaction gas from the reaction zone, said means comprising at least one gas reservoir for gas to be supplied to the reaction zone, supply means with a supply channel coaxial to the axis of the reactor, for supplying reaction gas from at least one gas reservoir to the reaction zone, discharge means with a discharge channel coaxial to the axis of the reactor for carrying reaction products and excess reaction gas away from the reaction zone, a gas separating system for the gas coming from the reaction zone and a gas pump for conveying gas out of the reaction zone.

abstract

A polarized neutron guide for separating neutrons into polarized neutrons while minimizing loss of the neutrons is provided. The polarized neutron guide includes a body, the first space and the second space, and a neutron separation space. The body includes super mirrors coated with a neutron-reflective thin film and the first and second spaces are formed by the first plate inside the body. The neutron separation space is formed by the second plate disposed at the entry of the first space and the third plate disposed at the entry of the second space. Spin-up polarized neutrons and spin-down polarized neutrons are simultaneously separated and transferred in the first and second spaces, respectively. Therefore, with minimum loss of the neutrons, the spin-up polarized neutrons and the spin-down polarized neutrons are effectively separated and collected.

042382912

claims

1. For coupling pipelines in a nuclear reactor pressure vessel with a core flood line formed of a first line section extending sealingly through a housing wall of the reactor pressure vessel and secured thereto, and a second line section disposed in the interior of the pressure vessel and couplable sealingly to the first line section, the second line section extending through a cover of a core container and terminating in the core container, a device comprising means for forming the second line section and the core container cover into a structural unit so that the second line section together with the core container cover is liftable out of and insertable into the pressure vessel upon opening the latter for selectively inspecting, servicing and both inspecting and servicing the same, the first and second line sections having a mutual coupling location, means defining coaxial sealing surfaces disposed at said mutual coupling location for holding the first and second line sections in mutual engagement, said coaxial sealing surfaces having a contact pressure therebetween deriving from weight per se and bracing forces of the core container cover oriented in axial direction of the pressure vessel, the first and the second line sections being in mutual spring-biased engagement at said mutual coupling location thereof, the second line section having a guidance collar integral therewith at said mutual coupling location, and including a one-piece counter-support member formed as a pipe bushing carried by said guidance collar, said counter-support member being mounted with spring bias and displaceable longitudinally on said guidance collar, said spring bias being afforded by compression spring means carried by said pipe bushing and disposed intermediate said pipe bushing and said guidance collar. 2. Device according to claim 1 wherein said coaxial sealing surfaces are engageable at a ball-and-socket seat. 3. Device according to claim 2 wherein the first line section has an upwardly directed ball seat-mouthpiece forming the ball of said ball-and-socket seat, and said counter-support member comprising a downwardly directed cone seat forming the socket of said ball-and-socket seat. 4. Device according to claim 3 including axially normal, inwardly directed pins mounted on said counter-support member and guided, in axial direction of said counter-support member, in longitudinal grooves formed in said guidance collar, said longitudinal grooves having end flanks for limiting displacement of said counter-support member in opposite axial directions. 5. Device according to claim 3 including opposing end flanges formed, respectively, on said guidance collar and on said counter-support member and disposed in mutual alignment, said compression spring means comprising at least one helical compression spring mounted between said end flanges. 6. Device according to claim 3 including a pipe apron disposed at said mutual coupling location radially inwardly of said compression spring means for shielding said compression spring means from the interior of the first and second line sections. 7. Device according to claim 1 including means for introducing an initial flow of flood water to the core flood line forming the first and second line sections, the second line section at said mutual coupling location having surfaces subjectible to application of interior pressure from the pressure vessel and pressure of the flood water, the area of said surfaces having a mutual ratio effecting an increase in contact pressure applied between said coaxial sealing surfaces upon introduction of the initial flow of flood water. 8. Device according to claim 1 wherein steam separators in the reactor pressure vessel overlie and are connected to the interior of the core container through the cover thereof, and including means for incorporating the steam separators into said structural unit formed of the second line section and the core container cover.

summary

048030430

claims

1. In a nuclear fuel rod grid including a plurality of inner and outer straps being interleaved with one another to form a matrix of hollow cells, each cell for receiving one fuel rod and being defined by pairs of opposing wall sections of said straps which wall sections are shared with adjacent cells, each cell having a central longitudinal axis, a fuel rod engaging spring structure of resiliently yieldable material being integrally formed on each wall section of said inner straps comprising: (a) a pair of laterally spaced elongated leg members each having a pair of opposite ends only at which is anchored to said wall section; and (b) an elongated cross member having a pair of opposite ends, said cross member extending diagonally between and integrally attached at its opposite ends to said leg members such that said spring structure formed by said leg and cross members has an effective length greater than the actual length it occupies on said wall section. said section is generally planar in configuration; and said leg members project from the plane of said wall section when said cell is unoccupied by a fuel rod but are capable of resiliently deflecting back within the plane of said wall section due to resilient deflection of said cross member by engagement with a fuel rod received within said cell. (a) a pair of laterally spaced elongated spring leg members each having a pair of opposite ends at which it is anchored to said wall section and being arcuate-shaped in its configuration along a longitudinal section therethrough so as to project from said wall section into one of said cells toward said central longitudinal axis thereof, each leg member also extending generally parallel to one another and in a direction generally parallel to said longitudinal axis of said cell; and (b) an elongated cross spring member having a pair of opposite ends, said cross member extending diagonally between and attached at its opposite ends to said .leg members and being arcuate-shaped in configuration along a longitudinal section therethrough so as to project from said wall section farther into said one cell toward said central longitudinal axis thereof than said leg membrs project into said one cell for engaging a fuel rod when received through said one cell, said cross member being disposed approximately forty-five degrees with respect to the direction of said longitudinal axis of said one cell. said wall section is generally planar in configuration; and said leg members project from the plane of said wall section when said cell is unoccupied by a fuel rod but are capable of resiliently deflecting back within the plane of said wall section due to resilient deflection of said cross member upon engagement with a fuel rod received within said cell. (a) at least one arcuate-shaped-dimple connected at its opposite ends to said wall section and projecting from said wall section into one of said cells toward said central longitudinal axis thereof; (b) said dimple being oriented diagonally with respect to said central longitudinal axis of said cell. (c) a spring having a fuel rod engaging elongated cross member oriented diagonally with respect to said central longitudinal axis of said cell and projecting from said wall section into said cell toward said central longitudinal axis thereof. (c) a fuel rod engaging spring projecting from said wall section into said cell toward said central longitudinal axis thereof. 2. The spring structure as recited in claim 1, wherein said cross member at one of its opposite ends is rigidly attached to one of said leg members adjacent to one end thereof and at the other of its opposite ends is rigidly attached to the other of said leg members adjacent to the opposite other end thereof. 3. The spring structure as recited in claim 1, wherein the effective length of said spring structure formed by said leg and cross members is approximately two times greater than the actual length it occupies on said wall section. 4. The spring structure as recited in claim 1, wherein each said leg member is arcuate-shaped in its configuration along a longitudinal section therethrough so as to project from said wall section into one of said cells toward said central longitudinal axis thereof. 5. The spring structure as recited in claim 4, wherein said cross member is arcuate-shaped in configuration along a longitudinal section therethrough so as to project from said wall section farther into said one cell toward said central longitudinal axis thereof than said leg members project into said one cell for engaging a fuel rod when received through said one cell. 6. The spring structure as recited in claim 4, wherein said cross member is capable of resiliently deflecting in a direction generally orthogonal to and away from said longitudinal axis of said cell and toward said wall section upon engagement by a fuel rod when received in said cell. 7. The spring structure as recited in claim 6, wherein: 8. The spring structure as recited in claim 6, wherein said cross member is projecting from said wall section defines a space therebetween which permits unimpeded flow of coolant fluid therethrough and along a fuel rod received in said cell. 9. The spring structure as recited in claim 1, wherein said each leg member extends generally parallel to one another. 10. The spring structure as recited in claim 9, wherein each leg member extends in a direction generally parallel to said longitudinal axis of said cell. 11. The spring structure as recited in claim 10, wherein said cross member is disposed approximately forty-five degrees with respect to the direction of said longitudinal axis of said one cell. 12. The spring structure as recited in claim 9, wherein said cross member is disposed approximately forty-five degrees with respect to said each leg member. 13. In a nuclear fuel rod grid including a plurality of inner and outer straps being interleaved with one another to form a matrix of hollow cells, each cell for receiving one fuel rod and being defined by pairs of opposing wall sections of said straps which wall sections are shared with adjacent cells, each cell having a central longitudinal axis, a fuel rod engaging spring structure of resiliently yieldable material being integrally on each wall section of said inner straps comprising: 14. The spring structure as recited in claim 13, wherein said cross member at one of its opposite ends is rigidly attached to one of said leg members adjacent to one end thereof and at the other of its opposite ends is rigidly attached to the other of said leg members adjacent to the opposite other end thereof such that said spring structure formed by said leg and cross members has an effective length approximately two times greater than the actual length it occupies on said wall section. 15. The spring structure as recited in claim 13, wherein said cross member is capable of resiliently deflecting in a direction generally orthogonal to and away from said longitudinal axis of said cell upon engagement by a fuel rod when received in said cell. 16. The spring structure as recited in claim 15, wherein: 17. The spring structure as recited in claim 13, wherein said cross member in projecting from said wall section defines a space therebetween which permits unimpeded flow of coolant fluid therethrough and along a fuel rod received in said cell. 18. In a nuclear fuel rod grid including a plurality of inner and outer straps being interleaved with one another to form a matrix of hollow cells, each cell for receiving one fuel rod and being defined by pairs of opposing wall sections of said straps, each cell having a central longitudinal axis, fuel rod engaging structure of resiliently yieldable material being integrally formed on each wall section of said inner straps comprising: 19. The engaging structure as recited in claim 18, wherein said dimple is oriented approximately forty-five degrees with respect to said cell longitudinal axis. 20. The engaging structure as recited in claim 18, further comprising: 21. The engaging structure as recited in claim 20, wherein said spring structure cross member is oriented approximately forty-five degrees with respect to said cell longitudinal axis. 22. The engaging structure as recited in claim 20, further comprising a pair of said dimples, one being located spaced above said spring and the other being located spaced below said spring on said wall section. 23. The engaging structure as recited in claim 22, wherein said dimples are oriented diagonally to said cell longitudinal axis and generally parallel to one another. 24. The engaging structure as recited in claim 22, wherein said dimples are oriented diagonally to said cell longitudinal axis and generally perpendicular to one another. 25. The engaging structure as recited in claim 22, wherein one of said dimples is oriented generally parallel to said spring cross member. 26. The engaging structure as recited in claim 22, wherein one of said dimples is oriented generally perpendicular to said spring cross member. 27. The engaging structure as recited in claim 18, further comprising: 28. The engaging structure as recited in claim 27, further comprising a pair of said dimples, one being located spaced above said spring and the other being located spaced below said spring on said wall section. 29. The engaging structure as recited in claim 28, wherein said dimples are oriented diagonally to said cell longitudinal axis and generally parallel to one another. 30. The engaging structure as recited in claim 28, wherein said dimples are oriented diagonally to said cell longitudinal axis and generally perpendicular to one another.

description

The present application is related to and/or claims the benefit of the earliest available effective filing date(s) from the following listed application(s) (the “Priority Applications”), if any, listed below (e.g., claims earliest available priority dates for other than provisional patent applications or claims benefits under 35 USC §119(e) for provisional patent applications, for any and all parent, grandparent, great-grandparent, etc. applications of the Priority Application(s)). In addition, the present application is related to the “Related Applications,” if any, listed below. The present application constitutes a continuation of U.S. patent application Ser. No. 14/201,386, entitled SYSTEMS, DEVICES, AND METHODS FOR LOWERING DENTAL X-RAY DOSAGE INCLUDING FEEDBACK SENSORS, naming Roderick A. Hyde, Edward K.Y. Jung, Jordin T. Kare, Tony S. Pan, Charles Whitmer, Lowell L. Wood, Jr. as inventors, 7 Mar. 2014, which is currently co-pending or is an application of which a currently co-pending application is entitled to the benefit of the filing date. If an Application Data Sheet (ADS) has been filed on the filing date of this application, it is incorporated by reference herein. Any applications claimed on the ADS for priority under 35 U.S.C. §§119, 120, 121, or 365(c), and any and all parent, grandparent, great-grandparent, etc. applications of such applications, are also incorporated by reference, including any priority claims made in those applications and any material incorporated by reference, to the extent such subject matter is not inconsistent herewith. If the listings of applications provided above are inconsistent with the listings provided via an ADS, it is the intent of the Applicant to claim priority to each application that appears in the Priority Applications section of the ADS and to each application that appears in the Priority Applications section of this application. All subject matter of the Priority Applications and the Related Applications and of any and all parent, grandparent, great-grandparent, etc. applications of the Priority Applications and the Related Applications, including any priority claims, is incorporated herein by reference to the extent such subject matter is not inconsistent herewith. In an aspect, the present disclosure is directed to, among other things, an intra-oral x-ray imaging system. In an embodiment, the intra-oral x-ray imaging system includes an intra-oral x-ray sensor configured to acquire intra-oral x-ray image information associated with a patient. In an embodiment, the intra-oral x-ray imaging system includes an x-ray beam limiter assembly including a controllable x-ray collimator module. In an embodiment, the controllable x-ray collimator module includes an x-ray beam collimation adjustment mechanism that is responsive to one or more inputs including information associated with a border position of the intra-oral sensor. In an embodiment, the intra-oral x-ray imaging system includes an x-ray beam limiter assembly configured to adjust an x-ray beam field of view. In an embodiment, the intra-oral x-ray imaging system includes an x-ray collimator module operably coupled to the intra-oral x-ray sensor and the x-ray beam limiter assembly. In an embodiment, the x-ray collimator module is configured to adjust an x-ray beam field of view responsive to one or more inputs including information associated with a border position of the intra-oral sensor. In an embodiment, the intra-oral x-ray imaging system includes an x-ray beam limiter assembly having one or more shutters (e.g., spring-loaded shutters, solenoid activated shutters, relay device activated shutters, electro-mechanical shutters, etc.). In an embodiment, during operation, the x-ray collimator module is configured to vary a shutter aperture associated with at least one of the one or more shutters responsive to the one or more inputs. In an embodiment, the intra-oral x-ray imaging system includes an x-ray beam limiter assembly having one or more aperture diaphragms. In an embodiment, during operation, the x-ray collimator module is configured to vary a diaphragm aperture of the one or more aperture diaphragms responsive to one or more inputs including information associated with a border position of the intra-oral sensor. In an aspect, the present disclosure is directed to, among other things, an intra-oral x-ray imaging device. In an embodiment, the intra-oral x-ray imaging device includes circuitry configured to determine a position (e.g., location, spatial placement, locality, spatial location, physical location, physical position, etc.) or an orientation (e.g., angular position, physical orientation, attitude, etc.) of an intra-oral x-ray sensor. In an embodiment, the intra-oral x-ray imaging device includes circuitry configured to adjust an x-ray beam field of view responsive to one or more inputs from the circuitry configured to determine the position or orientation of the intra-oral x-ray sensor. In an embodiment, the intra-oral x-ray imaging device includes circuitry configured to acquire intra-oral x-ray image information associated with a patient. In an embodiment, the intra-oral x-ray imaging device includes circuitry configured to generate one or more parameters associated with a field of view setting. In an aspect, the present disclosure is directed to, among other things, an intra-oral x-ray imaging method. In an embodiment, the intra-oral x-ray imaging method includes automatically determining an intra-oral x-ray sensor border position and an intra-oral x-ray sensor orientation. In an embodiment, the intra-oral x-ray imaging method includes varying an x-ray beam field of view parameter (e.g., a field of view size, a diameter dimension, a field of view position parameter, an x-ray field collimation parameter, etc.) responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation. In an embodiment, the intra-oral x-ray imaging method includes acquiring intra-oral x-ray image information associated with a patient. In an embodiment, the intra-oral x-ray imaging method includes generating at least one parameter associated with an x-ray imaging mode (e.g., adult panoramic mode, child panoramic mode, high-dose-rate mode, low-dose-rate mode, moderate-dose-rate mode, mandible mode, occlusion mode, maxillary mode, panoramic mode, pulsed fluoroscopy mode, temporomandibular joint mode, etc.) responsive to automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation. In an embodiment, the intra-oral x-ray imaging method includes varying an x-ray beam aim parameter responsive to automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation. In an aspect, the present disclosure is directed to, among other things, an intra-oral x-ray sensor. In an embodiment, the intra-oral x-ray sensor includes an x-ray image component configured to acquire intra-oral x-ray image information associated with a patient. In an embodiment, the intra-oral x-ray sensor includes an intra-oral radiation shield structure configured to reduce at least one of x-ray scattering, transmission, or re-radiation by at least 50%. For example, in an embodiment, oral x-ray sensor includes an intra-oral radiation shield structure having one or more high-atomic number (high-Z) materials in an amount sufficient to reduce at least one of x-ray scattering, transmission, or re-radiation by at least 50%. In an aspect, the present disclosure is directed to, among other things, an intra-oral x-ray sensor. In an embodiment, the intra-oral x-ray sensor includes circuitry configured to communicate intra-oral x-ray sensor position information to a remote x-ray source. In an embodiment, the circuitry configured to communicate intra-oral x-ray sensor position information to the remote x-ray source includes one or more wired or wireless connections to the remote x-ray source. In an embodiment, the intra-oral x-ray sensor includes circuitry configured to communicate intra-oral x-ray sensor orientation information to the remote x-ray source. In an embodiment, the intra-oral x-ray sensor includes circuitry configured to verify an x-ray beam characteristic associated with the remote x-ray source. In an embodiment, the intra-oral x-ray sensor includes circuitry configured to communicate an x-ray beam field of view parameter to the remote x-ray source responsive to verifying an x-ray beam characteristic. In an embodiment, the intra-oral x-ray sensor includes circuitry configured to determine remote x-ray source and intra-oral x-ray sensor alignment before communicating an activation instruction to the remote x-ray source for imaging. In an embodiment, the intra-oral x-ray sensor includes circuitry configured to acquire a low intensity x-ray pulse to determine remote x-ray source and intra-oral x-ray sensor alignment before communicating an activation instruction to the remote x-ray source for imaging. In an aspect, the present disclosure is directed to, among other things, an intra-oral x-ray sensor operation method. In an embodiment, the intra-oral x-ray sensor operation method includes communicating intra-oral x-ray sensor position information to a remote x-ray source. In an embodiment, the intra-oral x-ray sensor operation method includes communicating intra-oral x-ray sensor orientation information to a remote x-ray source. In an embodiment, the intra-oral x-ray sensor operation method includes verifying an x-ray beam characteristic associated with the remote x-ray source. In an embodiment, the intra-oral x-ray sensor operation method includes communicating an x-ray beam field of view parameter to the remote x-ray source responsive to verifying an x-ray beam characteristic. In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. Radiographs (e.g., intra-oral radiographs, panoramic radiographs, cephalo radiographs, etc.) are essential and valuable diagnostic tools in dentistry. An objective of dental radiography is to obtain the highest quality images possible, while keeping patients' exposure risk to a minimum. Exposure to radiation may cause cancer, birth defects in the children of exposed parents, and cataracts. A major concern is the delayed health effects arising from chronic cumulative exposure to radiation. One way to reduce a patient's radiation burden is to employ low-dose practices. FIGS. 1A and 1B show an intra-oral x-ray imaging system 100 in which one or more methodologies or technologies can be implemented such as, for example, reducing patient exposure to x-rays, reducing amount of scatter, transmission, or re-radiation during imaging, or improving x-ray image quality. In an embodiment, the intra-oral x-ray imaging system 100 includes one or more intra-oral x-ray sensors 102. In an embodiment, at least one of the one or more intra-oral x-ray sensors 102 is configured to acquire intra-oral x-ray image information 104 associated with a patient. In an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray source 105 operably coupled to one or more intra-oral x-ray sensors 102. In an embodiment, the intra-oral x-ray imaging system 100 includes one or more power sources. In an embodiment, during operation, x rays from the x-ray source 105 pass through the body of the patient striking hard and soft tissue. In an embodiment, a portion of the x-ray beam is deflected, a portion of the x-ray beam is scattered, a portion of the x-ray beam is absorbed, a portion triggers release of characteristic radiation, etc. Intra-oral x-ray image information (e.g., diagnostic dental x rays) is acquired by positioning a part of the body to be examined between a focused x-ray beam and the intra-oral x-ray sensors 102. In an embodiment, the intra-oral x-ray imaging system 100 includes one or more modules. For example, in an embodiment, the intra-oral x-ray imaging system 100 includes x-ray collimator module 106. In an embodiment, the collimator module 106 is operably coupled to an intra-oral x-ray sensor 102 and an x-ray beam limiter assembly 108. For example, in an embodiment, the collimator module 106 is operably coupled to an intra-oral x-ray sensor 102 via a wired or wireless connection 103. In an embodiment, the x-ray beam limiter assembly 108 includes a controllable x-ray collimator module 106. In an embodiment, the controllable x-ray collimator module 106 includes an x-ray beam collimation adjustment mechanism that is responsive to one or more inputs including information associated with a border position of the intra-oral sensor 102. For example, in an embodiment, the x-ray collimator module 106 is configured to vary a shutter aperture 114 associated with at least one of the one or more shutters responsive one or more inputs including information associated with a position of the intra-oral sensor 102, a border position of the intra-oral sensor 102, a position of an intra-oral x-ray sensor centroid, or the like. In an embodiment, a module includes, among other things, one or more computing devices such as a processor (e.g., a microprocessor), a central processing unit (CPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like, or any combinations thereof, and can include discrete digital or analog circuit elements or electronics, or combinations thereof. In an embodiment, a module includes one or more ASICs having a plurality of predefined logic components. In an embodiment, a module includes one or more FPGAs, each having a plurality of programmable logic components. In an embodiment, the x-ray collimator module 106 includes a module having one or more components operably coupled (e.g., communicatively, electromagnetically, magnetically, ultrasonically, optically, inductively, electrically, capacitively coupled, or the like) to each other. In an embodiment, a module includes one or more remotely located components. In an embodiment, remotely located components are operably coupled, for example, via wireless communication. In an embodiment, remotely located components are operably coupled, for example, via one or more receivers, transmitters, transceivers, antennas, or the like. In an embodiment, the x-ray collimator module 106 includes a module having one or more routines, components, data structures, interfaces, and the like. In an embodiment, a module includes memory that, for example, stores instructions or information. For example, in an embodiment, the x-ray collimator module 106 includes memory that stores, for example, one or more of intra-oral x-ray sensor border position information, intra-oral x-ray sensor centroid information, intra-oral x-ray sensor dimension information, intra-oral x-ray sensor orientation information, intra-oral x-ray sensor position information, intra-oral x-ray sensor specific collimation information, or the like. For example, in an embodiment, the x-ray collimator module 106 includes memory that, for example, stores reference collimation information (e.g., reference collimation shape information, reference collimation size information, reference collimation separation information, etc.), intra-oral x-ray sensor position or orientation information, x-ray image information associated with a patient, or the like. Non-limiting examples of memory include volatile memory (e.g., Random Access Memory (RAM), Dynamic Random Access Memory (DRAM), or the like), non-volatile memory (e.g., Read-Only Memory (ROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Compact Disc Read-Only Memory (CD-ROM), or the like), persistent memory, or the like. Further non-limiting examples of memory include Erasable Programmable Read-Only Memory (EPROM), flash memory, or the like. In an embodiment, the memory is coupled to, for example, one or more computing devices by one or more instructions, information, or power buses. For example, in an embodiment, the x-ray collimator module 106 includes memory that, for example, stores reference collimation information (e.g., reference collimation shape information, reference collimation size information, reference collimation separation information, etc.), intra-oral x-ray sensor position or orientation information, x-ray image information associated with a patient, or the like. In an embodiment, a module includes one or more computer-readable media drives, interface sockets, Universal Serial Bus (USB) ports, memory card slots, or the like, and one or more input/output components such as, for example, a graphical user interface, a display, a keyboard, a keypad, a trackball, a joystick, a touch-screen, a mouse, a switch, a dial, or the like, and any other peripheral device. In an embodiment, a module includes one or more user input/output components, user interfaces, or the like, that are operably coupled to at least one computing device configured to control (electrical, electromechanical, software-implemented, firmware-implemented, or other control, or combinations thereof) at least one parameter associated with, for example, controlling activating, operating, or the like, an x-ray beam limiter assembly 108. In an embodiment, a module includes a computer-readable media drive or memory slot that is configured to accept signal-bearing medium (e.g., computer-readable memory media, computer-readable recording media, or the like). In an embodiment, a program for causing a system to execute any of the disclosed methods can be stored on, for example, a computer-readable recording medium (CRMM), a signal-bearing medium, or the like. Non-limiting examples of signal-bearing media include a recordable type medium such as a magnetic tape, floppy disk, a hard disk drive, a Compact Disc (CD), a Digital Video Disk (DVD), Blu-Ray Disc, a digital tape, a computer memory, or the like, as well as transmission type medium such as a digital or an analog communication medium (e.g., a fiber optic cable, a waveguide, a wired communications link, a wireless communication link (e.g., receiver, transmitter, transceiver, transmission logic, reception logic, etc.). Further non-limiting examples of signal-bearing media include, but are not limited to, DVD-ROM, DVD-RAM, DVD+RW, DVD-RW, DVD-R, DVD+R, CD-ROM, Super Audio CD, CD-R, CD+R, CD+RW, CD−RW, Video Compact Discs, Super Video Discs, flash memory, magnetic tape, magneto-optic disk, MINIDISC, non-volatile memory card, EEPROM, optical disk, optical storage, RAM, ROM, system memory, web server, or the like. In an embodiment, the x-ray collimator module 106 is configured to adjust an x-ray beam field of view responsive to one or more inputs including information associated with a border position of the intra-oral sensor 102. For example, in an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray beam limiter assembly 108 having at least one collimator 110. In an embodiment, the collimator 110 includes a barrier 112 with a variable aperture 114 configured to vary the size and shape of an x-ray beam so as to substantially match the size of an intra-oral x-ray sensor detection region 126a (shown in FIG. 2B). In an embodiment, the collimator 110 implements filtration and collimation techniques and methodologies that reduce a patient's radiation burden. For example, in an embodiment, during operation, activation of the collimator 110 results in a reduction of the size and shape of the x-ray beam, resulting in a reduction of the volume of irradiated tissue in the patient. In an embodiment, activation of the collimator 110 also results in the elimination of one or more divergent portion of an x-ray beam. In an embodiment, the x-ray collimator module 106 is operably coupled to the intra-oral x-ray sensor 102 and the x-ray beam limiter assembly 108, and is configured to adjust an x-ray beam field of view responsive to one or more inputs from the intra-oral x-ray sensor 102 indicative of a border position of the intra-oral sensor 102. The variation of the x-ray beam field of view can comprise a change in the beam size, the beam shape, the beam orientation, or the like. In an embodiment, the x-ray beam expands as it propagates from the x-ray beam limiter assembly 108 towards the patient and the intra-oral x-ray sensor 102. For example, the x-ray propagation can be calculated by assuming straight line x-ray trajectories, allowing the propagation and expansion of the beam to be calculated by knowledge of the relative positions of the x-ray source 105 (e.g., internal components such as an x-ray beam emitter and elements of the x-ray beam limiter assembly 108) and the intra-oral x-ray sensor 102. In an embodiment, the x-ray collimator module 106 is configured to adjust the x-ray beam field of view such that a border position of the expanding x-ray substantially corresponds (e.g., matches, minimizes overfilling, minimizes underfilling, substantially fills the sensor area, etc.) to a border position of the intra-oral x-ray sensor 102 as the propagating beam arrives at it. In an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray beam limiter assembly 108 having an automatic aperture control mechanism including one or more mechanical diaphragms, (e.g., spring-loaded diaphragm, solenoid activated diaphragm, relay device activated diaphragm, electro-mechanical diaphragm, electromagnetic diaphragm, etc.) The mechanical diaphragm can include a plurality of aperture blades that interact with each other to create the aperture through which the x-rays are projected. In an embodiment, the x-ray collimator module 106 is configured to vary an aperture 114 associated with at least one of the one or more aperture blades included in a mechanical diaphragm responsive one or more inputs indicative of a position of the intra-oral sensor 102, a border position of the intra-oral sensor 102, a position of an intra-oral x-ray sensor centroid, or the like. In an embodiment, the x-ray collimator module 106 is configured to vary an aperture 114 associated with at least one of the one or more mechanical aperture diaphragms responsive one or more inputs indicative of an orientation of the intra-oral sensor 102. In an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray beam limiter assembly 108 having one or more aperture diaphragms. In an embodiment, the x-ray collimator module 106 is configured to vary a diaphragm aperture of the one or more aperture diaphragms responsive to one or more inputs indicative of an orientation or a border position of the intra-oral sensor 102. The diaphragm adjusts the aperture blades to provide the appropriately sized and shaped aperture. In an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray beam limiter assembly 108 having a collimator 110 including a collimator aperture. In an embodiment, the collimator aperture shape can be a geometrical shape including and regular geometric shapes, such as circular, rectangular, triangular, or the like, as well as irregular geometric shapes. In an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray beam limiter assembly 108 including one or more blades, radiation source shutters, wedges, and the like. In an embodiment, the x-ray collimator module 106 is configured to adjust the x-ray beam field size by actuating a change in a separation distance between a collimator aperture and an x-ray source 105 responsive to one or more inputs including information associated with an orientation or a border position of the intra-oral sensor 102. For example, in an embodiment, the x-ray collimator module 106 is operably coupled to a separation distance adjustment mechanism responsive to one or more inputs including information associated with an orientation or a border position of the intra-oral sensor 102. In an embodiment, the x-ray collimator module 106 is operably coupled to a collimator-and-x-ray source assembly configured to adjust the x-ray beam field size by actuating a change in a separation distance between a collimator aperture and an x-ray source 105 responsive to one or more inputs including information associated with an orientation or a border position of the intra-oral sensor 102. In an embodiment, the x-ray beam limiter assembly 108 includes a primary collimator and a secondary collimator. In an embodiment, the x-ray beam limiter assembly 108 includes a variable aperture collimator. In an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray beam limiter assembly 108 having a plurality of selectively actuatable absorber blades configured to form a focal plane shutter. In an embodiment, the focal plane shutter is positioned immediately or right in front of the intra-oral sensor 102. In an embodiment, the focal plane shutter is positioned immediately or right in front of a film-based analog x-ray sensor, a dental digital x-ray sensor, a charge-coupled device (CCD) sensor, complementary metal-oxide-semiconductor (CMOS) sensor, and the like. In an embodiment, the x-ray collimator module 106 is configured to adjust the x-ray beam field size by actuating one or more of the plurality of selectively actuatable absorber blades responsive one or more inputs including information associated with an orientation or a border position of the intra-oral sensor 102. In an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray beam limiter assembly 108 configured to adjust an x-ray beam field size. In an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray beam limiter assembly 108 configured to reduce the size of the x-ray beam at the point of contact with the intra-oral sensor to the size of the intra-oral sensor 102 detection area so as to reduce a patient exposure to x-rays. In an embodiment, the x-ray beam limiter assembly 108 includes one or more aperture diaphragms. In an embodiment, the x-ray beam limiter assembly 108 includes one or more circular aperture diaphragms having mechanical extensions (e.g., aperture blades, radiation source shutters, wedges, etc.) configured to form part of a focal plane shutter. In an embodiment, the x-ray beam limiter assembly 108 includes a shutter assembly having one or more opposing pair shutters. In an embodiment, the x-ray beam limiter assembly 108 includes at least a first-stage shutter and a second-stage shutter. In an embodiment, the intra-oral sensor 102 is configured to work together with the x-ray source 105 to reduce unnecessary patient exposure to x-rays. For example, in an embodiment, the x-ray beam limiter assembly 108 includes an aperture shaped and sized to direct an x-ray beam that provides a beam area that coincides with the detector area of the intra-oral sensor 102. During operation, the x-ray emitter and the intra-oral sensor 102 placed in the patient's mouth may not align exactly, resulting in an x-ray beam projection that is too big, too small, misoriented, etc. In an embodiment, this is fixed by translating or rotating an aperture or by translating or rotating the x-ray emitter. In an embodiment, the x-ray beam limiter assembly 108 includes at least one x-ray beam-limiting aperture configured to translate (laterally and/or longitudinally) relative to an x-ray emitter. In an embodiment, the x-ray beam limiter assembly 108 includes at least one x-ray beam-limiting aperture configured to rotate relative to an x-ray emitter. In an embodiment, the x-ray beam limiter assembly 108 includes at least one x-ray emitter configured to translate (laterally and/or longitudinally) relative to an x-ray beam-limiting aperture. In an embodiment, the x-ray beam limiter assembly 108 includes one or more diaphragms formed from high atomic number (high-Z) materials. For example, in an embodiment, the x-ray beam limiter assembly 108 includes one or more shutters formed from materials including elements have an atomic number greater than or equal to 37 (Rubidium or higher). In an embodiment, the x-ray beam limiter assembly 108 includes one or more shutters formed from materials including elements have an atomic number greater than or equal to 72 (Hafnium or higher). In an embodiment, the x-ray beam limiter assembly 108 includes one or more x-ray filters. For example, in an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray beam limiter assembly 108 including one or more x-ray compensating filters 117 such as a wedge 117a formed from aluminum, ceramic, high-density plastic, etc., that is placed over an oral cavity region during radiography to compensate for differences in radiopacity. In an embodiment, the x-ray compensating filter is configured to limit the x-rays passing through based upon the varying thickness of the filter. In an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray beam limiter assembly 108 including one or more positive beam limitation devices configured to automatically collimate the x-ray beam to the size of the intra-oral x-ray sensor detection region at the point of contact with the intra-oral x-ray sensor 102. In an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray beam limiter assembly 108 including one or more positive beam limitation devices configured to automatically collimate the x-ray beam so as to substantially match the size of an intra-oral x-ray sensor detection region 126a (shown in FIG. 2B). In an embodiment, the x-ray beam limiter assembly 108 includes an extension cone or an extension cylinder. In an embodiment, the x-ray collimator module 106 is configured to interface with one or more components via one or more wired or wireless connections. For example, in an embodiment, the x-ray collimator module 106 is in wireless communication with the x-ray beam limiter assembly 108. In an embodiment, the x-ray collimator module 106 is operably coupled to the x-ray beam limiter assembly 108 via one or more wired connections. In an embodiment, the x-ray collimator module 106 is in wireless communication with the intra-oral x-ray sensor 102. In an embodiment, the x-ray collimator module 106 is in wireless communication with an x-ray source 105. In an embodiment, the intra-oral x-ray sensor 102 is in wireless communication with an x-ray source 105. In an embodiment, the x-ray collimator module 106 is configured to adjust the x-ray beam field size responsive to the one or more inputs, such as one or more inputs including information associated with a location of a corner position of the intra-oral x-ray sensor 102. In an embodiment, the x-ray collimator module 106 is configured to adjust the x-ray beam field size responsive to the one or more inputs including information associated with a location of an edge position of the intra-oral x-ray sensor 102. In an embodiment, the x-ray collimator module 106 is configured to adjust the x-ray beam field size responsive to the one or more inputs including information associated with a location of a reference position on the intra-oral x-ray sensor 102 having a specified offset from a corner of the intra-oral x-ray sensor 102. In an embodiment, the x-ray collimator module 106 is configured to adjust the x-ray beam field size responsive to the one or more inputs including information associated with a location of a reference position on the intra-oral x-ray sensor having a specified offset from an edge of the intra-oral x-ray sensor 102. In an embodiment, the x-ray collimator module 106 is configured to adjust the x-ray beam field size responsive to the one or more inputs including information associated with an edge orientation of the intra-oral x-ray sensor 102. In an embodiment, the x-ray collimator module 106 is configured to adjust the x-ray beam field size responsive to one or more inputs from the x-ray collimator module 106 indicative of an intra-oral x-ray sensor position or orientation. In an embodiment, the position and/or orientation of the intra-oral x-ray sensor is determined relative to the position and/or orientation of at least one of the x-ray source 105, the collimator module 106, the x-ray beam limiter assembly 108, an x-ray beam emitter, and an external reference point. For example, in an embodiment, during operation, the x-ray collimator module 106 is configured to adjust the x-ray beam field size responsive to one or more inputs from the x-ray collimator module 106 indicative of an intra-oral x-ray sensor border position. In an embodiment, during operation, the x-ray collimator module 106 is configured to adjust the x-ray beam field size responsive to one or more inputs from the x-ray collimator module 106 indicative of an intra-oral x-ray sensor centroid 126 position. In an embodiment, during operation, the x-ray collimator module 106 is configured to adjust the x-ray beam field size responsive to one or more inputs from the x-ray collimator module 106 indicative of an intra-oral x-ray sensor angular orientation. In an embodiment, the x-ray collimator module 106 is configured to adjust the x-ray beam field size responsive to one or more inputs from the x-ray collimator module 106 indicative of an intra-oral x-ray sensor dimension. In an embodiment, the x-ray collimator module 106 is configured to generate one or more parameters associated with an x-ray beam limiter assembly 108 configuration responsive to one or more inputs from an intra-oral x-ray sensor 102. In an embodiment, the x-ray collimator module 106 is configured to generate at least one parameter associated with an x-ray imaging mode (e.g., adult panoramic mode, child panoramic mode, high-dose-rate mode, low-dose-rate mode, moderate-dose-rate mode mandible mode, occlusion mode, maxillary mode, panoramic mode, pulsed fluoroscopy mode, temporomandibular joint mode, etc.) responsive to one or more inputs from an intra-oral x-ray sensor 102. In an embodiment, the intra-oral x-ray imaging system 100 includes a field of view module 107 operable to generate one or more parameters associated with a field of view setting (e.g., field of view size, field of view shape, wide field of view, narrow field of view, field of view extension, horizontal field of view, vertical field of view, diagonal field of view, magnification, increase, decrease, etc.) responsive to one or more inputs from the x-ray collimator module 106 indicative of an intra-oral x-ray sensor position, orientation, or the like. In an embodiment, the intra-oral x-ray imaging system 100 includes one or more intra-oral x-ray sensors 102 configured to acquire intra-oral x-ray image information 104 associated with a patient. In an embodiment, the intra-oral x-ray imaging system 100 includes an x-ray image component 116 operably coupled to one or more intra-oral x-ray sensors 102. Non-limiting examples of intra-oral x-ray sensors 102 include film-based analog x-ray sensors, dental digital x-ray sensors, charge-coupled device (CCD) sensors, complementary metal-oxide-semiconductor (CMOS) sensors, and the like. In an embodiment, the intra-oral x-ray imaging system 100 includes one or more intra-oral x-ray sensors 102 having at least one scintillator plate. In an embodiment, the intra-oral x-ray imaging system 100 includes one or more intra-oral x-ray sensors 102 having at least one scintillator layer. In an embodiment, a scintillator layer is vapor-deposited onto an optical fiber coupled to a photo-sensor integrated into a CCD or CMOS chip. Further non-limiting examples of intra-oral x-ray sensors 102 includes scintillators (e.g., inorganic scintillators, thallium doped cesium iodide scintillators, scintillator-photodiode pairs, scintillation detection devices, etc.), dosimeters (e.g., x-ray dosimeters, thermoluminescent dosimeters, etc.), optically stimulated luminescence detectors, photodiode arrays, charge-coupled devices (CCDs), complementary metal-oxide-semiconductor (CMOS) devices, or the like. In an embodiment, the intra-oral x-ray sensor 102 includes one or more transducers that detect and convert x-rays into electronic signals. For example, in an embodiment, the intra-oral x-ray sensor 102 includes one or more x-ray radiation scintillation crystals. In an embodiment, the intra-oral x-ray sensor 102 includes one or more thallium doped cesium iodide crystals (e.g., cesium iodide crystals doped with thallium CsI(Tl)). In an embodiment, during operation the intra-oral x-ray sensor 102 includes a computing device that processes the electronic signals generated by the one or more transducers to determine one or more of intensity, energy, time of exposure, date of exposure, exposure duration, rate of energy deposition, depth of energy deposition, and the like associated with each x-ray detected. In an embodiment, during operation, incident x-ray radiation interacts with one or more detector crystalline materials (e.g., cadmium zinc telluride, etc.) within the intra-oral x-ray sensor 102, which results in the generation of a current indicative of, for example, the energy of the incident x-ray radiation. In an embodiment, the intra-oral x-ray sensor 102 includes an amorphous-carbon substrate coupled to a Cesium Iodide (CsI) scintillator. In an embodiment, the intra-oral x-ray sensor 102 includes a fiber optic plate (FOP) coupled to a CsI scintillator. In an embodiment, the intra-oral x-ray sensor 102 includes an aluminum substrate coupled to a CsI scintillator. In an embodiment, the intra-oral x-ray sensor 102 includes a scintillator configured to reduce scattering. For example, in an embodiment, the intra-oral x-ray sensors 102 includes thallium-doped-Cesium Iodide (CsI:TI) having columnar structure deposited on a substrate operably coupled to a CMOS/CCD sensor. See e.g., Zhao et al. X-ray imaging performance of structured cesium iodide scintillators. Med. Phys. 31, 2594-2605 (2004) which is incorporated herein by reference. The columnar structure of CsI helps to selectively pass a portion of the x-ray bean onto a CMOS/CCD sensor forming part of the intra-oral x-ray sensor 102. In an embodiment, the intra-oral x-ray sensor 102 includes a substrate that acquires at least a portion of penetrating x-ray radiation stimulus and transduces the penetrating x-ray radiation stimulus acquired by the intra-oral x-ray sensor 102 into an image or at least one measurand indicative of an x-ray flux throughput during an integration period of the intra-oral x-ray sensor 102. In an embodiment, an x-ray image component 116 component is operably coupled to an intra-oral x-ray sensor 102 having one or more x-ray radiation fluoroscopic elements. In an embodiment, the intra-oral x-ray sensor 102 includes one or more phosphorus doped elements (e.g., ZnCdS:Ag phosphorus doped elements). In an embodiment, the intra-oral x-ray sensor 102 includes one or more amorphous silicon thin-film transistor arrays. In an embodiment, the intra-oral x-ray sensor 102 includes one or more phosphors. In an embodiment, the x-ray image component 116 is operably coupled to one or more active pixel image sensors. In an embodiment, the x-ray image component 116 is operably coupled to one or more complementary metal-oxide-semiconductor sensors. In an embodiment, the x-ray image component 116 is operably coupled to one or more complementary metal-oxide-semiconductor active pixel sensors. In an embodiment, the intra-oral x-ray imaging system 100 includes at least one intra-oral x-ray sensor 102 wirelessly coupled to the x-ray collimator module 106. In an embodiment, the intra-oral x-ray imaging system 100 includes at least one intra-oral x-ray sensor 102 wired or wirelessly coupled to an x-ray source 105. In an embodiment, the intra-oral x-ray imaging system 100 includes an intra-oral x-ray sensor module 109 operably coupled to the intra-oral x-ray sensor 102 and the x-ray collimator module. In an embodiment, the intra-oral x-ray sensor module 109 is configured to generate one or more of intra-oral x-ray sensor dimension information, intra-oral x-ray sensor orientation information, or intra-oral x-ray sensor position information responsive to one or more inputs from the x-ray image sensor 102 or the x-ray collimator module 106. In an embodiment, the x-ray collimator module 106 is in wireless communication with the intra-oral x-ray sensor module. In an embodiment, during operation, the intra-oral x-ray imaging system 100 is configured to determine the position and orientation of the intra-oral x-ray sensor 102, and to adjust an x-ray beam field of view responsive to determining the position and orientation of the intra-oral x-ray sensor 102. For example, in an embodiment, the intra-oral x-ray imaging system 100 includes a camera, a sensor, a component, etc., configured to acquire image information associated with a position or an orientation of the intra-oral x-ray sensor 102. In an embodiment, the camera acquires an image involving one or more beacons 118, phosphors 120, retroreflectors 122, or the like that are configured to indicate the position or orientation of the intra-oral x-ray sensor 102. In an embodiment, the x-ray collimator module 106 is operably coupled to one or more sensors, components, etc., configured to determine, indicate, communicate, broadcast, etc., a border position of the intra-oral sensor 102. In an embodiment, the x-ray collimator module 106 is operably coupled to one or more beacons 118, phosphors 120, retroreflectors 122, or the like configured to determine, indicate, communicate, broadcast, etc., a border position of the intra-oral sensor 102. For example, during operation, the x-ray collimator module 106 is configured to acquire one or more inputs from one or more beacons 118 indicative of the position or orientation of the intra-oral x-ray sensor 102. In an embodiment, during operation, the x-ray collimator module 106 is configured to acquire one or more electrical, acoustic, or electromagnetic inputs from one or more beacons 118 indicative of the position or orientation of the intra-oral x-ray sensor 102. In an embodiment, during operation, the x-ray collimator module 106 is configured to acquire one or more inputs from a sensor configure to detect a florescence associated with one or more phosphors 120, and to generate information indicative of the position or orientation of the intra-oral x-ray sensor 102 based on the one or more inputs from the sensor. In an embodiment, the x-ray collimator module 106 is operably coupled to one or more sensors configured to generate one or more outputs indicative of the position or orientation of the intra-oral x-ray sensor 102. In an embodiment, the x-ray collimator module 106 is operably coupled to one or retroreflectors configured to indicate the position or orientation of the intra-oral x-ray sensor 102. In an embodiment, the x-ray collimator module 106 is operably coupled to one or more beacons 118 configured to indicate, communicate, convey, etc., position information or orientation information associated with an intra-oral x-ray sensor 102. Non-limiting examples of beacons 118 include infrared emitters, ultraviolet emitters, visible emitters, electromagnetic energy emitters, ultrasound emitters, and the like. Further non-limiting examples of beacons 118 include magnetic field generators, inductors, capacitors, or the like. In an embodiment, during operation, the x-ray collimator module 106 adjusts an x-ray beam field of view responsive to detecting one or more emitted signals from a beacon 118. In an embodiment, the x-ray collimator module 106 is operably coupled to one or more beacons 118 configured to emit an ultrasonic output. In an embodiment, the x-ray collimator module 106 is operably coupled to one or more beacons 118 configured to emit an ultrasonic output that is detectable through tissue. In an embodiment, the x-ray collimator module 106 is operably coupled to one or more phosphors 120 configured to indicate the position or orientation of the intra-oral x-ray sensor 102. Non-limiting examples of phosphors 120 include infrared phosphors, ultraviolet phosphors, visible phosphors, x-ray phosphors, and the like. Further non-limiting examples of phosphors 120 include phosphors having a peak emission wavelength associated with an optical window in biological tissue. See e.g. J. Phys. D: Appl. Phys. 46 (2013) 375401 (5pp) which is incorporated herein by reference. In an embodiment, the x-ray collimator module 106 is operably coupled to one or more phosphors 120 configured to provide a signal through the patient's skin (i.e. cheek, gum, or teeth). In an embodiment, the x-ray collimator module 106 is operably coupled to one or more phosphors 120 having a peak emission wavelength ranging from about 650 nanometers to about 900 nanometers. In an embodiment, during operation, the border position of the intra-oral sensor 102 is signaled by one or more phosphors 120. In an embodiment, during operation, the x-ray collimator module 106 adjusts an x-ray beam field of view responsive to detecting one or more phosphors 120 and determining a border position of the intra-oral sensor 102 based on determining the location of the one or more phosphors 120. In an embodiment, the intra-oral x-ray sensor comprises a position sensor 124 configured to determine border position data, and a transmitter configured to transmit a signal indicative of the border position data. In an embodiment, the border position data includes X, Y, and Z coordinates. In an embodiment, the border position data includes one or more parameters that define a specific location in a two-dimensional object or three-dimensional object. In an embodiment, the border position data includes one or more position parameters associated with an intra-oral x-ray sensor border. In an embodiment, the border position data includes one or more position parameters associated with an intra-oral x-ray sensor centroid 126. Non-limiting examples of position sensors 124 include local positioning system (e.g., analogous to GPS-type sensors) sensors configured to interact with room-based reference signals. In an embodiment, the position sensor 124 includes a magnetic sensor responding to room-based magnetic fields. In an embodiment, the position sensor 124 includes one or more accelerometer 128. In an embodiment, the position sensor 124 includes a multi-accelerometer or accelerometer-gyro package that keeps track of the motion involved in putting intra-oral x-ray sensor 102 into the patient's mouth. In an embodiment, the x-ray collimator module 106 is configured to adjust the x-ray beam to minimize the portion of the x-ray beam that misses (e.g., overfills) the intra-oral x-ray sensor 102. In an embodiment, the x-ray collimator module 106 is further configured to adjust the x-ray beam to maximize an amount of the x-ray beam that impacts the intra-oral x-ray sensor 102, e.g., to minimize underfilling it. FIG. 2A shows an intra-oral x-ray imaging device 200 in which one or more methodologies or technologies can be implemented such as, for example, reducing patient exposure to x-rays, reducing amount of scatter, transmission, or re-radiation during imaging, or improving x-ray image quality. In an embodiment, the intra-oral x-ray imaging device 200 includes circuitry 202 configured to determine a position and an orientation of an intra-oral x-ray sensor 102. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 includes circuitry configured to determine border position information of the intra-oral x-ray sensor 102. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 includes circuitry configured to determine an intra-oral x-ray sensor centroid position. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 includes an image sensor 203 configured to detect one or more optic devices 204 (e.g., retroreflectors, beacons, emitters, etc.) indicative of an intra-oral x-ray sensor border position, an intra-oral x-ray sensor position, or an intra-oral x-ray sensor orientation. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to an embedded orientation detection component 206. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 and the one or more acoustic transducers 232 form part of an integrated component. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more magnetic compass based sensors 208. For example, in an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more embedded magnetic compass sensors 210. In an embodiment, the circuitry 202 configured to determine position and the orientation of the intra-oral x-ray sensor 102 and the one or more embedded magnetic compass sensors 210 form part of an integrated component. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 forms part of an integrated image sensor configured to detect one or more optic devices 204 (e.g., retroreflectors, beacons, emitters, etc.) In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more local positioning system based sensors 124. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more acceleration sensors 214. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to at least two acceleration sensors 214 in a substantially perpendicularly arrangement. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more multi-axis accelerometers 216. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more orientation-aware sensors 218. For example, in an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor is operably coupled to one or more gyroscopes 220. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more electrolytic fluid based sensors 222. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to a two-axis tilt sensor 224 configured to detect an intra-oral x-ray sensor roll or yaw angle. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to a two-axis tilt sensor 224 configured to detect an intra-oral x-ray sensor pitch angle. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more inductors 226. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more active optic devices 228. For example, in an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more optical emitter that emit an electromagnetic energy signal that provides information associated with the position and the orientation of the intra-oral x-ray sensor 102. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more active acoustic emitters. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more passive optics devices 230 (e.g., retroreflectors, phosphors, etc.). In an embodiment, during operation, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 by emitting an interrogation signal that is reflected back by the one or more retroreflectors. The reflected signal is use to generate information associated with the position and the orientation of the intra-oral x-ray sensor 102. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 is operably coupled to one or more acoustic transducers 232 configured to generate an output indicative of an intra-oral x-ray sensor border position and an intra-oral x-ray sensor orientation. In an embodiment, the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102 and the one or more acoustic transducers 232 form part of an integrated component. In an embodiment, the intra-oral x-ray sensor 102 includes an integrated component including one or more optic devices 204, orientation detection component 206, magnetic compass based sensors 208, embedded magnetic compass sensors 210, local positioning system based sensors 124, more acceleration sensors 214, multi-axis accelerometers 216, orientation-aware sensors 218, gyroscopes 220, electrolytic fluid based sensors 222, two-axis tilt sensors 224, inductors 226, optic devices 228, passive optics devices 230, acoustic transducers 232, or the like. In an embodiment, the intra-oral x-ray imaging device 200 includes circuitry 234 configured to adjust an x-ray beam field of view (FOV) responsive to one or more inputs from the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102. For example, in an embodiment, the circuitry 234 configured to adjust the x-ray beam field of view is operably coupled to at least one of the x-ray collimator module 106 or the x-ray beam limiter assembly 108, and is configured to generate one or more control signal that actuates the x-ray collimator module 106 or the x-ray beam limiter assembly 108 to adjust an x-ray beam FOV responsive to one or more inputs from the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102. In an embodiment, the intra-oral x-ray imaging device 200 includes circuitry 236 configured to acquire intra-oral x-ray image information associated with a patient. In an embodiment, the intra-oral x-ray imaging device 200 includes circuitry 238 configured to generate one or more parameters associated with a field of view setting. In an embodiment, the circuitry 238 configured to generate one or more parameters associated with a field of view setting includes circuitry configured to generate the one or more parameters associated with the field of view setting responsive to one or more inputs from the circuitry 202 configured to determine the position and the orientation of the intra-oral x-ray sensor 102. FIG. 3A shows an intra-oral x-ray sensor 102 in which one or more methodologies or technologies can be implemented such as, for example, reducing patient exposure to x-rays, reducing amount of scatter, transmission, or re-radiation during imaging, or improving x-ray image quality. In an embodiment, the intra-oral x-ray sensor 102 includes an x-ray image component 116 configured to acquire intra-oral x-ray image information 104 associated with a patient. In an embodiment, the x-ray image component 116 includes circuitry 236 configured to acquire intra-oral x-ray image information associated with a patient. In an embodiment, the intra-oral x-ray sensor 102 includes an intra-oral radiation shield structure 302 configured to reduce at least one of x-ray scattering, transmission, or re-radiation by at least 50%. In an embodiment, the intra-oral radiation shield structure 302 includes one or more high atomic number (high-Z) materials in an amount sufficient to reduce at least one of x-ray scattering, transmission, or re-radiation by at least 50%. For example, in an embodiment, at least a portion of the intra-oral radiation shield structure 302 is formed from materials including elements have an atomic number greater than or equal to 37 (Rubidium or higher). In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is formed from materials including elements have an atomic number greater than or equal to 72 (Hafnium or higher). In an embodiment, the intra-oral radiation shield structure 302 includes one or more materials having a K-edge greater than 15 kiloelectron volts in an amount sufficient to reduce at least one of x-ray scattering, transmission, or re-radiation by at least 50%. Non-limiting examples of materials having a K-edge greater than 15 kiloelectron volts include elements have an atomic number greater than or equal to 37 (Rubidium or higher). In an embodiment, the intra-oral radiation shield structure 302 includes one or more materials having an L-edge greater than 10 kiloelectron volts in an amount sufficient to reduce at least one of x-ray scattering, transmission, or re-radiation by at least 50%. Non-limiting examples of materials having an L-edge greater than 10 kiloelectron volts include elements have an atomic number greater than or equal to 69 (Thulium or higher). In an embodiment, the intra-oral radiation shield structure 302 includes a mixture of materials having a K-edge greater than 15 kiloelectron volts, materials having an L-edge greater than 10 kiloelectron volts, or high atomic number (high-Z) materials in an amount sufficient to reduce at least one of x-ray scattering, transmission, or re-radiation by at least 50%. Referring to FIG. 3B, in an embodiment, the intra-oral x-ray sensor 102 includes a laminate structure having multiple layers. For example, in an embodiment, the intra-oral x-ray sensor 102 includes one or more of radiation shield layers 304, 306, electronic circuit layers 308, sensor layers 310, scintillator layers 312, protection layers 314, etc. In an embodiment, the intra-oral radiation shield structure 302 includes a laminate structure having at least a first layer 304. In an embodiment, the intra-oral radiation shield structure 302 includes a laminate structure having at least a first layer 304 and a second layer 306, the second layer having an x-ray attenuation profile different from the first layer. In an embodiment, the intra-oral radiation shield structure 302 includes a laminate structure having at least a first layer 304 and a second layer 306, the second layer 306 having an attenuation coefficient different from the first layer 304. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of one or more x-ray shielding materials. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of one or more x-ray radio-opaque materials (e.g., barium sulfate, silicon carbide, silicon nitride, alumina, zirconia, etc.). In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of one or more x-ray attenuating materials. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of one or more x-ray attenuating ceramic materials. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of multiple layers, each layer having an xx-ray attenuation coefficient different from another. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of one or more ferromagnetic materials. Ferromagnetic materials include those materials having a Curie temperature, above which thermal agitation destroys the magnetic coupling giving rise to the alignment of the elementary magnets (electron spins) of adjacent atoms in a lattice (e.g., a crystal lattice). In an embodiment, one or more of the plurality of x-ray shielding particles include one or more ferromagnets. Non-limiting examples ferromagnetic materials include crystalline ferromagnetic materials, ferromagnetic oxides, materials having a net magnetic moment, materials having a positive susceptibility to an external magnetic field, non-conductive ferromagnetic materials, non-conductive ferromagnetic oxides, ferromagnetic elements (e.g., cobalt, gadolinium, iron, or the like), rare earth elements, ferromagnetic metals, ferromagnetic transition metals, materials that exhibit magnetic hysteresis, and the like, and alloys or mixtures thereof. Further non-limiting examples of ferromagnetic materials include chromium (Cr), cobalt (Co), copper (Cu), dysprosium (Dy), europium (Eu), gadolinium (Gd), iron (Fe), magnesium (Mg), neodymium (Nd), nickel (Ni), yttrium (Y), and the like. Further non-limiting examples of ferromagnetic materials include chromium dioxide (CrO2), copper ferrite (CuOFe2O3), europium oxide (EuO), iron(II, III) oxide (FeOFe2O3), iron(III) oxide (Fe2O3), magnesium ferrite (MgOFe2O3), manganese ferrite (MnOFe2O3), nickel ferrite (NiOFe2O3), yttrium-iron-garnet (Y3Fe5O12), and the like. Further non-limiting examples of ferromagnetic materials include manganese arsenide (MnAs), manganese bismuth (MnBi), manganese (III) antimonide (MnSb), Mn—Zn ferrite, neodymium alloys, neodymium, Ni—Zn ferrite, and samarium-cobalt. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of iron oxides. Non-limiting examples of iron oxides include copper ferrite (CuOFe2O3), iron(II, III) oxide (FeOFe2O3), iron(III) oxide (Fe2O3), magnesium ferrite (MgOFe2O3), manganese ferrite (MnOFe2O3), nickel ferrite (NiOFe2O3), yttrium-iron-garnet (Y3Fe5O12), ferric oxides, ferrous oxides, and the like. In an embodiment, one or more of the plurality of x-ray shielding particles include at least one iron oxide. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of one or ferrimagnetic materials. In an embodiment, one or more of the plurality of x-ray shielding particles include one or more ferrimagnets (e.g., soft ferrites, hard ferrites, or the like). Non-limiting examples of ferrimagnetic materials include ferrimagnetic oxides (e.g., ferrites, garnets, or the like). Further non-limiting examples of ferrimagnetic materials include ferrites with a general chemical formula of AB2O4 (e.g., CoFe2O4, MgFe2O4, ZnFe2O4) where A and B represent various metal cations. In an embodiment, A is Mg, Zn, Mn, Ni, Co, or Fe(II); B is Al, Cr(III), Mn(III) or Fe(III), and O is oxygen. In an embodiment, A is a divalent atom of radius ranging from about 80 pm to about 110 pm (e.g., Cu, Fe, Mg, Mn, Zn, or the like), B is a trivalent atom of radius ranging from about 75 pm to about 90 pm, (e.g., Al, Fe, Co, Ti, or the like), and O is oxygen. Non-limiting examples of ferrimagnetic materials include iron ferrites with a general chemical formula MOFe2O3 (e.g., CoFe2O4, Fe3O4, MgFe2O4, or the like) where M is a divalent ion such as Fe, Co, Cu, Li, Mg, Ni, or Zn. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of at least a first ferrimagnetic material and a second ferromagnetic material, the second ferrimagnetic material having one or more absorption edges different from the first ferrimagnetic material. In an embodiment, the intra-oral radiation shield structure 302 includes a laminate structure having at least a first layer 304 and a second layer 306, the second layer having a different ferrimagnetic material composition from the first layer. Non-limiting examples of ferrimagnetic materials include materials having a magnetization compensation point, materials that are associated with a partial cancellation of antiferromagnetically aligned magnetic sublattices with different values of magnetic moments, or material having different temperature dependencies of magnetization. See e.g., Kageyama et al., Weak Ferrimagnetism, Compensation Point, and Magnetization Reversal in Ni(HCOO)2.2H2O, Physical Rev. B, 224422 (2003). In an embodiment, at least a portion of the intra-oral radiation shield structure 302 comprises one or more paramagnetic materials. In an embodiment, the intra-oral radiation shield structure 302 is removably attachable to the intra-oral x-ray sensor 102. For example, in an embodiment, at least a portion of the intra-oral radiation shield structure 302 is removably attachable to the intra-oral x-ray sensor 102, behind a sensor layer 310. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 includes two or more layers secured to each other to form structure 302. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of one or more x-ray radio-opaque materials. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of one or more x-ray attenuating materials. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of one or more x-ray attenuating ceramic materials. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of at least a first x-ray radio-opaque material and a second x-ray radio-opaque material, the second x-ray radio-opaque material having a different x-ray opacity profile from the first x-ray radio-opaque material. In an embodiment, the intra-oral radiation shield structure 302 includes a laminate structure having at least a first layer 304 and a second layer 306, the second layer 306 having a different opacity profile from the first layer 304. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is formed from at least one x-ray attenuating material, x-ray radio-opaque material, or x-ray attenuating ceramic material. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is formed from at least one ferromagnetic material, ferrimagnetic material, or paramagnetic material. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of one or more high-Z, high-density, materials. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of at least a first x-ray attenuating ceramic material and a second x-ray attenuating ceramic material, the second x-ray attenuating ceramic material having a different x-ray attenuation profile from the first x-ray attenuating ceramic material. In an embodiment, the intra-oral radiation shield structure 302 includes a laminate structure having at least a first layer 304 and a second layer 306, the second layer 306 having a different x-ray attenuation profile from the first layer 304. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of at least a first x-ray shielding material and a second x-ray shielding material, the second x-ray shielding material having one or more absorption edges different from the first x-ray shielding material. In an embodiment, at least one of the first x-ray shielding material or the second x-ray shielding material includes at least one material that absorbs x-rays at one or more frequencies and fluoresce x-rays at one or more lower frequencies. In an embodiment, at least one absorption edge of the second x-ray shielding material is selected to maximize absorption of x-rays fluoresced by the first x-ray shielding material. In an embodiment, at least a portion of the second x-ray shielding material is mounted between an x-ray image detector and a portion of the first x-ray shielding material on the intra-oral x-ray sensor 102. In an embodiment, at least a portion of the second x-ray shielding material is intermixed with at least a portion of the first x-ray shielding material. In an embodiment, at least a portion of the second x-ray shielding material is interlayered with at least a portion of the first x-ray shielding material. In an embodiment, at least a portion of the intra-oral radiation shield structure 302 is composed of at least a first x-ray shielding material and a second x-ray shielding material, the second x-ray shielding material having a different absorption edge profile from the first x-ray shielding material. In an embodiment, the intra-oral radiation shield structure 302 includes a laminate structure having at least a first layer 304 and a second layer 306, the second layer 306 having a different x-ray absorption edge profile from the first layer 304. In an embodiment, the second x-ray shielding material includes one or more K-edges, or one or more L-edges, different from the first x-ray shielding material. In an embodiment, the second x-ray shielding material includes at least one K-edge having an energy level lower than at least one K-edge of the first x-ray shielding material. In an embodiment, at least one of the first x-ray shielding material or the second x-ray shielding material includes at least one of lead (Pb), tantalum (Ta), or tungsten (W). In an embodiment, the second x-ray shielding material comprises an x-ray mass attenuation coefficient different from the first x-ray shielding material. In an embodiment, the intra-oral radiation shield structure 302 includes one or more x-ray shielding agents. For example, in an embodiment, the intra-oral radiation shield structure 302 includes a composition having a carrier fluid and a plurality of x-ray shielding particles each having at least a first x-ray shielding agent and a second x-ray shielding agent, the second x-ray shielding agent having one or more absorption edges different from the first x-ray shielding agent. In an embodiment, the intra-oral radiation shield structure 302 includes at least a first x-ray shielding agent and a second x-ray shielding agent, the second x-ray shielding agent having one or more absorption edges different from the first x-ray shielding agent. In an embodiment, the intra-oral radiation shield structure 302 includes at least a first x-ray shielding agent and a second x-ray shielding agent. In an embodiment, at least one of the first x-ray shielding agent or the second x-ray shielding agent includes at least one of mercury (Hg), lead (Pb), tantalum (Ta), or tungsten (W). In an embodiment, at least one of the first x-ray shielding agent or the second x-ray shielding agent includes at least one of teflon (C2F4), lead (II) oxide (PbO), or silicon nitride (Si3N4). In an embodiment, at least one of the first x-ray shielding agent or the second x-ray shielding agent includes at least one of boron, molybdenum, neodymium, niobium, strontium, tungsten yttrium, or zirconium, or combinations thereof. In an embodiment, at least one of the first x-ray shielding agent or the second x-ray shielding agent includes at least one of barium sulfate (BaSO4), boron nitride (BN), boron carbide (B4C), boron oxide (B2O3), or barium oxide (BaO). In an embodiment, at least one of the first x-ray shielding agent or the second x-ray shielding agent includes at least one of strontium oxide (SrO), zinc oxide (ZnO), or zirconium dioxide (ZrO2). In an embodiment, at least one of the first x-ray shielding agent or the second x-ray shielding agent includes at least one of SiO2—PbO-alkali metal oxide glass, CaO—SrO—B2O3 glass, or boron-lithium glass. In an embodiment, at least one of the first x-ray shielding agent or the second x-ray shielding agent includes borated high density polyethylene. In an embodiment, at least one of the first x-ray shielding agent or the second x-ray shielding agent includes at least one of mylar (C10H8O4), parylene-C (C8H7Cl), parylene-N(C8H8), poly(methyl methacrylate) (PMMA), polycarbonate (C16H14O3), polyethylene, or ultra-high molecular weight polyethylene. In an embodiment, a portion of the intra-oral radiation shield structure 302 is configured to have an x-ray shielding lead equivalence of about 0.25 millimeters to about 0.5 millimeters. For example, in an embodiment, a portion of the intra-oral radiation shield structure 302 includes a sufficient amount of x-ray shielding materials to have an x-ray shielding lead equivalence of about 0.25 millimeters to about 0.5 millimeters. In an embodiment, x-ray shielding lead equivalence is configured based on an anticipated x-ray spectrum. In an embodiment, a portion of the intra-oral radiation shield structure 302 has an x-ray shielding lead equivalence of greater than about 0.25 millimeters. In an embodiment, a portion of the intra-oral radiation shield structure 302 includes a plurality of x-ray shielding particles. In an embodiment, a portion of the intra-oral radiation shield structure 302 extends outwardly beyond a terminal border of an x-ray image detector forming part of the intra-oral x-ray sensor 102. In an embodiment, the intra-oral radiation shield is structured and dimensioned to conform to a portion of an oral cavity. In an embodiment, a portion of the intra-oral radiation shield structure 302 is flexible or jointed so as to conform to a portion of an oral cavity. Referencing FIG. 3A, in an embodiment, the intra-oral x-ray sensor 102 includes an embedded orientation detection component 316 configured to generate information associated with at least one of an intra-oral x-ray sensor orientation, an intra-oral x-ray sensor position, an intra-oral x-ray sensor dimension, or an intra-oral x-ray sensor centroid position. In an embodiment, the embedded orientation detection component 316 is operably coupled to one or more orientation sensors 318. For example, in an embodiment, the embedded orientation detection component 316 is operably coupled to one or more magnetic compass based sensors. In an embodiment, the embedded orientation detection component 316 is operably coupled to one or more embedded magnetic compass sensors. In an embodiment, the embedded orientation detection component 316 is operably coupled to one or more local positioning system based sensors 320. In an embodiment, the embedded orientation detection component 316 is operably coupled to at least two acceleration sensors 322 in a substantially perpendicularly arrangement. In an embodiment, the embedded orientation detection component 316 is operably coupled to at least one gyroscope 324. In an embodiment, the embedded orientation detection component 316 is operably coupled to at least one electrolytic fluid based sensor 326. In an embodiment, the embedded orientation detection component 316 is operably coupled to at least one transmitter (wired or wireless) configured to report position or orientation information to the remote x-ray source 105. In an embodiment, the embedded orientation detection component 316 is operably coupled to a two-axis tilt sensor 328 configured to detect an intra-oral x-ray sensor pitch angle and an intra-oral x-ray sensor roll angle. In an embodiment, the embedded orientation detection component 316 is operably coupled to at least one multi-axis accelerometer 330. In an embodiment, the embedded orientation detection component 316 is operably coupled to one or more orientation-aware sensors 332. In an embodiment, the embedded orientation detection component 316 is operably coupled to one or more inductors 334. In an embodiment, the embedded orientation detection component 316 is operably coupled to one or more acoustic transducers 336. In an embodiment, the x-ray image component 116 is operably coupled to one or more dental digital x-ray sensors. In an embodiment, the x-ray image component 116 is operably coupled to one or more dental digital x-ray sensors. In an embodiment, the x-ray image component 116 is operably coupled to one or more charge-coupled devices 338. In an embodiment, the x-ray image component 116 is operably coupled to one or more active pixel image sensors 340. In an embodiment, the x-ray image component 116 is operably coupled to one or more complementary metal-oxide-semiconductor sensors 342. In an embodiment, the x-ray image component 116 is operably coupled to one or more complementary metal-oxide-semiconductor active pixel sensors 344. In an embodiment, the intra-oral x-ray sensor 102 includes one or more passive optics devices 204 configured to indicate an intra-oral x-ray sensor border position. In an embodiment, the intra-oral x-ray sensor 102 includes one or more active optic devices 228 (e.g., beacons, acoustic emitters, optical emitters, etc.) configured to generate an output indicative of an intra-oral x-ray sensor border position. In an embodiment, the intra-oral x-ray sensor 102 includes a beacon component 346 configured to convey information associated with at least one of a sensor position or a sensor orientation. In an embodiment, the beacon component 346 is operably coupled to a transducer configured to generate an output indicative of an intra-oral x-ray sensor border position. In an embodiment, the beacon component 346 is operably coupled to one or more transducers configured to generate an output indicative of an intra-oral x-ray sensor border position. In an embodiment, the beacon component 346 is operably coupled to one or more active optic devices configured to generate an output indicative of an intra-oral x-ray sensor border position. In an embodiment, the beacon component 346 is operably coupled to one or more inductors configured to generate an output indicative of an intra-oral x-ray sensor border position. In an embodiment, the beacon component 346 is operably coupled to one or more accelerometers configured to generate an output indicative of an intra-oral x-ray sensor orientation. In an embodiment, the beacon component 346 is operably coupled to one or more gyroscopes configured to generate an output indicative of an intra-oral x-ray sensor orientation. In an embodiment, the beacon component 346 is operably coupled to one or more electrolytic fluid based sensors 326 configured to generate an output indicative of an intra-oral x-ray sensor orientation. In an embodiment, the intra-oral x-ray sensor 102 includes an x-ray backscatter component 348 operably coupled to the x-ray image component 116. In an embodiment, the x-ray backscatter component 348 is configured to modify the intra-oral x-ray image information responsive to one or more inputs from the x-ray image component 116 indicative of backscatter, i.e., to computationally remove image noise resulting from backscattered x-rays. In an embodiment, the intra-oral x-ray sensor 102 includes circuitry 352 configured to communicate intra-oral x-ray sensor position information to a remote x-ray source 105. In an embodiment, communication with the remote x-ray source 105 can be wired or wirelessly connected to the intra-oral x-ray sensor 102. In an embodiment, the circuitry 352 configured to communicate the intra-oral sensor 102 position to the remote x-ray source 105 comprises one or more of a receiver, transmitter, or transceiver. In an embodiment, the circuitry 352 configured to communicate the intra-oral sensor 102 position to the remote x-ray source 105 comprises a wireless transmitter. In an embodiment, the circuitry 352 configured to communicate the intra-oral sensor 102 position is operably coupled to one or more radiation reflecting elements (e.g., prisms retro-reflectors, etc.). In an embodiment, the circuitry 352 configured to communicate the intra-oral sensor 102 position is operably coupled to a modulatable reflector. In an embodiment, the intra-oral x-ray sensor 102 includes circuitry 354 configured to verify an x-ray beam characteristic associated with the remote x-ray source 105. In an embodiment, the circuitry 354 configured to verify the x-ray beam characteristic associated with the remote x-ray source 105 includes circuitry configured to determine x-ray beam centroid information associated with the remote x-ray source 105. In an embodiment, the circuitry 354 configured to verify the x-ray beam characteristic associated with the remote x-ray source 105 includes circuitry configured to determine a spatial pattern associated with an x-ray beam received from the remote x-ray source 105. In an embodiment, the circuitry 354 configured to verify the x-ray beam characteristic associated with the remote x-ray source 105 includes circuitry configured to determine a spatial alignment associated with an x-ray beam received from the remote x-ray source 105. In an embodiment, the circuitry 354 configured to verify the x-ray beam characteristic associated with the remote x-ray source 105 includes circuitry configured to determine lateral overlap information associated with an x-ray beam received from the remote x-ray source 105 and an intra-oral x-ray sensor 102. In an embodiment, the intra-oral x-ray sensor 102 includes circuitry 356 configured to communicate an x-ray beam field of view parameter to the remote x-ray source 105 responsive to verifying an x-ray beam characteristic. In an embodiment, the circuitry 356 configured to communicate the x-ray beam field of view parameter to the remote x-ray source 105 comprises one or more of a receiver, transmitter, or transceiver. In an embodiment, the circuitry 356 configured to communicate the x-ray beam field of view parameter to the remote x-ray source 105 comprises a wireless transmitter. In an embodiment, the intra-oral x-ray sensor 102 includes circuitry 358 configured to generate intra-oral x-ray sensor orientation information. In an embodiment, the circuitry 358 configured to generate intra-oral x-ray sensor orientation information is operably coupled to one or more embedded magnetic compasses. In an embodiment, the circuitry 358 configured to generate the intra-oral x-ray sensor orientation information is operably coupled to one or more electrolytic fluid based sensors 222. In an embodiment, the circuitry 358 configured to generate the intra-oral x-ray sensor orientation information is operably coupled to one or more acceleration sensors. In an embodiment, the circuitry 358 configured to generate the intra-oral x-ray sensor orientation information is operably coupled to one or more multi-axis accelerometers 330. In an embodiment, the circuitry 358 configured to generate the intra-oral x-ray sensor orientation information is operably coupled to at least two acceleration sensors in a substantially perpendicularly arrangement. In an embodiment, the circuitry 358 configured to generate the intra-oral x-ray sensor orientation information is operably coupled to one or more orientation-aware sensors 332. In an embodiment, the intra-oral x-ray sensor 102 includes circuitry 360 configured to generate intra-oral x-ray sensor position information. In an embodiment, the circuitry 360 configured to generate the intra-oral x-ray sensor position information is operably coupled to one or more local positioning system based sensors. In an embodiment, the circuitry 360 configured to generate the intra-oral x-ray sensor position information is operably coupled to one or more inductors 334. In an embodiment, the circuitry 360 configured to generate the intra-oral x-ray sensor position information is operably coupled to one or more active optic devices (e.g., photodetectors, imagers, CCD detectors, CMOS detectors, etc.). In an embodiment, the circuitry 360 configured to generate the intra-oral x-ray sensor position information is operably coupled to one or more acoustic transducers 336 configured to generate an output indicative of an intra-oral x-ray sensor border position and an intra-oral x-ray sensor orientation. In an embodiment, the circuitry 360 configured to generate the intra-oral x-ray sensor position information is operably coupled to one or more border indicating beacon devices 118. In an embodiment, the intra-oral x-ray sensor 102 includes circuitry 362 configured to determine remote x-ray source 105 and intra-oral x-ray sensor alignment before communicating an activation instruction to the remote x-ray source 105 for imaging. In an embodiment, the intra-oral x-ray sensor 102 includes circuitry 364 configured to acquire a low intensity x-ray pulse to determine remote x-ray source 105 and intra-oral x-ray sensor alignment before communicating an activation instruction to the remote x-ray source 105 for imaging. In an embodiment, the intra-oral x-ray sensor 102 includes an integrated component including one or more of the circuitry 352 configured to communicate the intra-oral sensor 102 position is operably coupled to a modulatable reflector; the circuitry 354 configured to verify an x-ray beam characteristic associated with the remote x-ray source 105; the circuitry 356 configured to communicate an x-ray beam field of view parameter to the remote x-ray source 105 responsive to verifying an x-ray beam characteristic; the circuitry 358 configured to generate intra-oral x-ray sensor orientation information; the circuitry 360 configured to generate intra-oral x-ray sensor position information; the circuitry 362 configured to determine remote x-ray source 105; the circuitry 364 configured to acquire a low intensity x-ray pulse to determine remote x-ray source 105 and intra-oral x-ray sensor alignment before communicating an activation instruction to the remote x-ray source 105 for imaging; or the like. FIGS. 4A-4C show an intra-oral x-ray imaging method 400. At 410, the intra-oral x-ray imaging method 400 includes automatically determining an intra-oral x-ray sensor border position and an intra-oral x-ray sensor orientation. At 412, automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes wirelessly detecting an intra-oral x-ray sensor beacon output indicative of the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation. At 414, automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes detecting at least one passive reflector associated with an intra-oral x-ray sensor and generating intra-oral x-ray sensor border position information and intra-oral x-ray sensor orientation information. At 416, automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes detecting a transducer response associated with an intra-oral x-ray sensor 102 and generating intra-oral x-ray sensor border position information and intra-oral x-ray sensor orientation information. At 418, automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes detecting a reference component associated with an intra-oral x-ray sensor 102 and generating intra-oral x-ray sensor border position information responsive to detecting the reference component. At 420, automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes detecting a reference component associated with an intra-oral x-ray sensor 102 and generating intra-oral x-ray sensor orientation information responsive to detecting the reference component. At 422, automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes acquiring at least one parameter from an accelerometer associated with an intra-oral x-ray sensor 102 and generating the intra-oral x-ray sensor orientation responsive to acquiring the at least one parameter from the accelerometer. At 430, the intra-oral x-ray imaging method 400 includes varying an x-ray beam field of view parameter responsive to one or more inputs including information associated with a location of the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation. At 432, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with an intra-oral x-ray sensor border position and an intra-oral x-ray sensor orientation includes varying the collimation size or the collimation shape of an external x-ray source 105 operably coupled to the intra-oral x-ray sensor 102. At 434, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes varying the x-ray beam field of view parameter sufficient to minimize overfilling of the intra-oral x-ray sensor 102. At 436, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes varying the x-ray beam field of view parameter sufficient to minimize underfilling of the intra-oral x-ray sensor 102. At 438, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes varying one or more parameters associated with a field of view setting responsive to automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation. At 440, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes varying a shutter aperture setting. At 442, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes varying a diaphragm aperture setting. At 444, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes varying a separation between a collimator aperture and an x-ray beam emitter within x-ray source 105. At 446, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes varying an orientation between a collimator aperture and an x-ray beam emitter within x-ray source 105. At 448, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes actuating one or more selectively actuatable absorber blades forming part of a focal plane shutter. At 450, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes actuating an x-ray beam limiter assembly 108 configured to adjust an x-ray beam field size. At 452, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes generating one or more parameters associated with an x-ray beam field size adjustment responsive to automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation. At 454, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes generating one or more x-ray beam limiter assembly 108 setting parameters responsive to automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation. At 456, varying the x-ray beam field of view parameter responsive to one or more inputs including information associated with the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation includes actuating at least one liquid absorber. At 460, the intra-oral x-ray imaging method 400 includes acquiring intra-oral x-ray image information associated with a patient. At 462, acquiring the intra-oral x-ray image information associated with the patient includes acquiring one or more intra-oral radiographic images. At 464, acquiring the intra-oral x-ray image information associated with the patient includes acquiring intra-oral radiographic view information. At 466, acquiring the intra-oral x-ray image information associated with the patient includes acquiring a periapical view image of at least one anterior or posterior tooth. At 468, acquiring the intra-oral x-ray image information associated with the patient includes acquiring a bitewing view image of at least one tooth crown. At 470, acquiring the intra-oral x-ray image information associated with the patient includes acquiring an occlusal view image of a palate. At 472, acquiring the intra-oral x-ray image information associated with the patient includes acquiring a posterior periapical image. At 474, acquiring the intra-oral x-ray image information associated with the patient includes acquiring an anterior periapical image. At 478, the intra-oral x-ray imaging method 400 includes generating at least one parameter associated with an x-ray imaging mode (e.g., adult panoramic mode, child panoramic mode, high-dose-rate mode, low-dose-rate mode, moderate-dose-rate mode mandible mode, occlusion mode, maxillary mode, panoramic mode, pulsed fluoroscopy mode, temporomandibular joint mode, etc.) responsive to automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation. At 480, the intra-oral x-ray imaging method 400 includes varying an x-ray beam aim parameter responsive to automatically determining the intra-oral x-ray sensor border position and the intra-oral x-ray sensor orientation. At 490, the intra-oral x-ray imaging method 400 includes communicating intra-oral x-ray sensor position information to a remote x-ray source 105. At 492, communicating the intra-oral x-ray sensor position information to the remote x-ray source 105 includes communicating intra-oral x-ray sensor dimension information to the remote x-ray source 105. At 494, communicating the intra-oral x-ray sensor position information to the remote x-ray source 105 includes communicating intra-oral x-ray sensor orientation information to the remote x-ray source 105. At 496, communicating the intra-oral x-ray sensor position information to the remote x-ray source 105 includes communicating one or more outputs indicative of an intra-oral x-ray sensor border position. At 498, the intra-oral x-ray imaging method 400 includes communicating intra-oral x-ray sensor orientation information to a remote x-ray source 105. FIG. 5 shows an intra-oral x-ray sensor operation method 500. At 510, the intra-oral x-ray sensor operation method 500 includes verifying an x-ray beam characteristic associated with the remote x-ray source 105. At 520, the intra-oral x-ray sensor operation method 500 includes communicating an x-ray beam field of view parameter to the remote x-ray source 105 responsive to verifying an x-ray beam characteristic. At 522, communicating the x-ray beam field of view parameter to the remote x-ray source 105 includes communicating a parameter associated with a change in separation between a collimator aperture 114 and the remote x-ray source 105. At 524, communicating the x-ray beam field of view parameter to the remote x-ray source 105 includes communicating a parameter associated with actuating one or more electro-mechanical collimation edges. At 526, communicating the x-ray beam field of view parameter to the remote x-ray source 105 includes communicating a parameter associated with displacing, moving, or rotating one or more collimation edges. At 528 communicating the x-ray beam field of view parameter to the remote x-ray source 105 includes communicating a parameter associated with adjusting a relative position of an x-ray beam emitter within the remote x-ray source 105 and a collimator 110 to improve alignment of the x-ray beam to the sensor. At 530, the intra-oral x-ray sensor operation method 500 includes activating a discovery protocol that allows an intra-oral x-ray sensor 102 and the remote x-ray source 105 to identify each other and to negotiate information. At 540, the intra-oral x-ray sensor operation method 500 includes determining a remote x-ray source 105 and intra-oral x-ray sensor alignment. At 550, the intra-oral x-ray sensor operation method 500 includes communicating an activation instruction to the remote x-ray source 105 for imaging responsive to determining the remote x-ray source 105 and intra-oral x-ray sensor 102 alignment. At 560, the intra-oral x-ray sensor operation method 500 includes detecting a low intensity x-ray pulse to determine remote x-ray source 105 and intra-oral x-ray sensor alignment. At 570, the intra-oral x-ray sensor operation method 500 includes communicating an activation instruction to the remote x-ray source 105 for imaging responsive to detecting the low intensity x-ray pre-pulse to determine remote the x-ray source 105 and intra-oral x-ray sensor 102 alignment. It is noted that FIGS. 4A-4C and 5 denotes “start” and “end” positions. However, nothing herein should be construed to indicate that these are limiting and it is contemplated that other or additional steps or functions can occur before or after those described in FIGS. 4A-4C and 5. The claims, description, and drawings of this application may describe one or more of the instant technologies in operational/functional language, for example as a set of operations to be performed by a computer. Such operational/functional description in most instances can be specifically-configured hardware (e.g., because a general purpose computer in effect becomes a special purpose computer once it is programmed to perform particular functions pursuant to instructions from program software). Importantly, although the operational/functional descriptions described herein are understandable by the human mind, they are not abstract ideas of the operations/functions divorced from computational implementation of those operations/functions. Rather, the operations/functions represent a specification for the massively complex computational machines or other means. As discussed in detail below, the operational/functional language must be read in its proper technological context, i.e., as concrete specifications for physical implementations. The logical operations/functions described herein are a distillation of machine specifications or other physical mechanisms specified by the operations/functions such that the otherwise inscrutable machine specifications may be comprehensible to the human mind. The distillation also allows one of skill in the art to adapt the operational/functional description of the technology across many different specific vendors' hardware configurations or platforms, without being limited to specific vendors' hardware configurations or platforms. Some of the present technical description (e.g., detailed description, drawings, claims, etc.) may be set forth in terms of logical operations/functions. As described in more detail in the following paragraphs, these logical operations/functions are not representations of abstract ideas, but rather representative of static or sequenced specifications of various hardware elements. Differently stated, unless context dictates otherwise, the logical operations/functions are representative of static or sequenced specifications of various hardware elements. This is true because tools available to implement technical disclosures set forth in operational/functional formats—tools in the form of a high-level programming language (e.g., C, java, visual basic), etc.), or tools in the form of Very high speed Hardware Description Language (“VIDAL,” which is a language that uses text to describe logic circuits—)—are generators of static or sequenced specifications of various hardware configurations. This fact is sometimes obscured by the broad term “software,” but, as shown by the following explanation, what is termed “software” is a shorthand for a massively complex interchanging/specification of ordered-matter elements. The term “ordered-matter elements” may refer to physical components of computation, such as assemblies of electronic logic gates, molecular computing logic constituents, quantum computing mechanisms, etc. For example, a high-level programming language is a programming language with strong abstraction, e.g., multiple levels of abstraction, from the details of the sequential organizations, states, inputs, outputs, etc., of the machines that a high-level programming language actually specifies. See, e.g., High-level Programming Language., Wikipedia. Wikimedia Foundation, 18 Jan. 2014. Web. 4 Feb. 2014. In order to facilitate human comprehension, in many instances, high-level programming languages resemble or even share symbols with natural languages. See, e.g., Natural Language., Wikipedia. Wikimedia Foundation, 14 Jan. 2014. Web. 4 Feb. 2014. It has been argued that because high-level programming languages use strong abstraction (e.g., that they may resemble or share symbols with natural languages), they are therefore a “purely mental construct” (e.g., that “software”—a computer program or computer-programming—is somehow an ineffable mental construct, because at a high level of abstraction, it can be conceived and understood in the human mind). This argument has been used to characterize technical description in the form of functions/operations as somehow “abstract ideas.” In fact, in technological arts (e.g., the information and communication technologies) this is not true. The fact that high-level programming languages use strong abstraction to facilitate human understanding should not be taken as an indication that what is expressed is an abstract idea. In an embodiment, if a high-level programming language is the tool used to implement a technical disclosure in the form of functions/operations, it can be understood that, far from being abstract, imprecise, “fuzzy,” or “mental” in any significant semantic sense, such a tool is instead a near incomprehensibly precise sequential specification of specific computational-machines—the parts of which are built up by activating/selecting such parts from typically more general computational machines over time (e.g., clocked time). This fact is sometimes obscured by the superficial similarities between high-level programming languages and natural languages. These superficial similarities also may cause a glossing over of the fact that high-level programming language implementations ultimately perform valuable work by creating/controlling many different computational machines. The many different computational machines that a high-level programming language specifies are almost unimaginably complex. At base, the hardware used in the computational machines typically consists of some type of ordered matter (e.g., traditional electronic devices (e.g., transistors), deoxyribonucleic acid (DNA), quantum devices, mechanical switches, optics, fluidics, pneumatics, optical devices (e.g., optical interference devices), molecules, etc.) that are arranged to form logic gates. Logic gates are typically physical devices that may be electrically, mechanically, chemically, or otherwise driven to change physical state in order to create a physical reality of Boolean logic. Logic gates may be arranged to form logic circuits, which are typically physical devices that may be electrically, mechanically, chemically, or otherwise driven to create a physical reality of certain logical functions. Types of logic circuits include such devices as multiplexers, registers, arithmetic logic units (ALUs), computer memory devices, etc., each type of which may be combined to form yet other types of physical devices, such as a central processing unit (CPU)—the best known of which is the microprocessor. A modern microprocessor will often contain more than one hundred million logic gates in its many logic circuits (and often more than a billion transistors). See, e.g., Logic Gates., Wikipedia. Wikimedia Foundation, 2 Apr. 2014. Web. 4 Feb. 2014. The logic circuits forming the microprocessor are arranged to provide a microarchitecture that will carry out the instructions defined by that microprocessor's defined Instruction Set Architecture. The Instruction Set Architecture is the part of the microprocessor architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external Input/Output. See, e.g., Computer Architecture., Wikipedia. Wikimedia Foundation, 2 Feb. 2014. Web. 4 Feb. 2014. The Instruction Set Architecture includes a specification of the machine language that can be used by programmers to use/control the microprocessor. Since the machine language instructions are such that they may be executed directly by the microprocessor, typically they consist of strings of binary digits, or bits. For example, a typical machine language instruction might be many bits long (e.g., 32, 64, or 128 bit strings are currently common). A typical machine language instruction might take the form “11110000101011110000111100111111” (a 32 bit instruction). It is significant here that, although the machine language instructions are written as sequences of binary digits, in actuality those binary digits specify physical reality. For example, if certain semiconductors are used to make the operations of Boolean logic a physical reality, the apparently mathematical bits “1” and “0” in a machine language instruction actually constitute a shorthand that specifies the application of specific voltages to specific wires. For example, in some semiconductor technologies, the binary number “1” (e.g., logical “1”) in a machine language instruction specifies around +5 volts applied to a specific “wire” (e.g., metallic traces on a printed circuit board) and the binary number “0” (e.g., logical “0”) in a machine language instruction specifies around −5 volts applied to a specific “wire.” In addition to specifying voltages of the machines' configuration, such machine language instructions also select out and activate specific groupings of logic gates from the millions of logic gates of the more general machine. Thus, far from abstract mathematical expressions, machine language instruction programs, even though written as a string of zeros and ones, specify many, many constructed physical machines or physical machine states. Machine language is typically incomprehensible by most humans (e.g., the above example was just ONE instruction, and some personal computers execute more than two billion instructions every second). See, e.g., Instructions per Second., Wikipedia. Wikimedia Foundation, 13 Jan. 2014. Web. 4 Feb. 2014. Thus, programs written in machine language—which may be tens of millions of machine language instructions long—are incomprehensible. In view of this, early assembly languages were developed that used mnemonic codes to refer to machine language instructions, rather than using the machine language instructions' numeric values directly (e.g., for performing a multiplication operation, programmers coded the abbreviation “mult,” which represents the binary number “011000” in MIPS machine code). While assembly languages were initially a great aid to humans controlling the microprocessors to perform work, in time the complexity of the work that needed to be done by the humans outstripped the ability of humans to control the microprocessors using merely assembly languages. At this point, it was noted that the same tasks needed to be done over and over, and the machine language necessary to do those repetitive tasks was the same. In view of this, compilers were created. A compiler is a device that takes a statement that is more comprehensible to a human than either machine or assembly language, such as “add 2+2 and output the result,” and translates that human understandable statement into a complicated, tedious, and immense machine language code (e.g., millions of 32, 64, or 128 bit length strings). Compilers thus translate high-level programming language into machine language. This compiled machine language, as described above, is then used as the technical specification which sequentially constructs and causes the interoperation of many different computational machines such that humanly useful, tangible, and concrete work is done. For example, as indicated above, such machine language—the compiled version of the higher-level language—functions as a technical specification which selects out hardware logic gates, specifies voltage levels, voltage transition timings, etc., such that the humanly useful work is accomplished by the hardware. Thus, a functional/operational technical description, when viewed by one of skill in the art, is far from an abstract idea. Rather, such a functional/operational technical description, when understood through the tools available in the art such as those just described, is instead understood to be a humanly understandable representation of a hardware specification, the complexity and specificity of which far exceeds the comprehension of most any one human. Accordingly, any such operational/functional technical descriptions may be understood as operations made into physical reality by (a) one or more interchained physical machines, (b) interchained logic gates configured to create one or more physical machine(s) representative of sequential/combinatorial logic(s), (c) interchained ordered matter making up logic gates (e.g., interchained electronic devices (e.g., transistors), DNA, quantum devices, mechanical switches, optics, fluidics, pneumatics, molecules, etc.) that create physical reality representative of logic(s), or (d) virtually any combination of the foregoing. Indeed, any physical object which has a stable, measurable, and changeable state may be used to construct a machine based on the above technical description. Charles Babbage, for example, constructed the first computer out of wood and powered by cranking a handle. Thus, far from being understood as an abstract idea, it can be recognizes that a functional/operational technical description as a humanly-understandable representation of one or more almost unimaginably complex and time sequenced hardware instantiations. The fact that functional/operational technical descriptions might lend themselves readily to high-level computing languages (or high-level block diagrams for that matter) that share some words, structures, phrases, etc. with natural language simply cannot be taken as an indication that such functional/operational technical descriptions are abstract ideas, or mere expressions of abstract ideas. In fact, as outlined herein, in the technological arts this is simply not true. When viewed through the tools available to those of skill in the art, such functional/operational technical descriptions are seen as specifying hardware configurations of almost unimaginable complexity. As outlined above, the reason for the use of functional/operational technical descriptions is at least twofold. First, the use of functional/operational technical descriptions allows near-infinitely complex machines and machine operations arising from interchained hardware elements to be described in a manner that the human mind can process (e.g., by mimicking natural language and logical narrative flow). Second, the use of functional/operational technical descriptions assists the person of skill in the art in understanding the described subject matter by providing a description that is more or less independent of any specific vendor's piece(s) of hardware. The use of functional/operational technical descriptions assists the person of skill in the art in understanding the described subject matter since, as is evident from the above discussion, one could easily, although not quickly, transcribe the technical descriptions set forth in this document as trillions of ones and zeroes, billions of single lines of assembly-level machine code, millions of logic gates, thousands of gate arrays, or any number of intermediate levels of abstractions. However, if any such low-level technical descriptions were to replace the present technical description, a person of skill in the art could encounter undue difficulty in implementing the disclosure, because such a low-level technical description would likely add complexity without a corresponding benefit (e.g., by describing the subject matter utilizing the conventions of one or more vendor-specific pieces of hardware). Thus, the use of functional/operational technical descriptions assists those of skill in the art by separating the technical descriptions from the conventions of any vendor-specific piece of hardware. In view of the foregoing, the logical operations/functions set forth in the present technical description are representative of static or sequenced specifications of various ordered-matter elements, in order that such specifications may be comprehensible to the human mind and adaptable to create many various hardware configurations. The logical operations/functions disclosed herein should be treated as such, and should not be disparagingly characterized as abstract ideas merely because the specifications they represent are presented in a manner that one of skill in the art can readily understand and apply in a manner independent of a specific vendor's hardware implementation. At least a portion of the devices or processes described herein can be integrated into an information processing system. An information processing system generally includes one or more of a system unit housing, a video display device, memory, such as volatile or non-volatile memory, processors such as microprocessors or digital signal processors, computational entities such as operating systems, drivers, graphical user interfaces, and applications programs, one or more interaction devices (e.g., a touch pad, a touch screen, an antenna, etc.), or control systems including feedback loops and control motors (e.g., feedback for detecting position or velocity, control motors for moving or adjusting components or quantities). An information processing system can be implemented utilizing suitable commercially available components, such as those typically found in data computing/communication or network computing/communication systems. The state of the art has progressed to the point where there is little distinction left between hardware and software implementations of aspects of systems; the use of hardware or software is generally (but not always, in that in certain contexts the choice between hardware and software can become significant) a design choice representing cost vs. efficiency tradeoffs. Various vehicles by which processes or systems or other technologies described herein can be effected (e.g., hardware, software, firmware, etc., in one or more machines or articles of manufacture), and that the preferred vehicle will vary with the context in which the processes, systems, other technologies, etc., are deployed. For example, if an implementer determines that speed and accuracy are paramount, the implementer may opt for a mainly hardware or firmware vehicle; alternatively, if flexibility is paramount, the implementer may opt for a mainly software implementation that is implemented in one or more machines or articles of manufacture; or, yet again alternatively, the implementer may opt for some combination of hardware, software, firmware, etc. in one or more machines or articles of manufacture. Hence, there are several possible vehicles by which the processes, devices, other technologies, etc., described herein may be effected, none of which is inherently superior to the other in that any vehicle to be utilized is a choice dependent upon the context in which the vehicle will be deployed and the specific concerns (e.g., speed, flexibility, or predictability) of the implementer, any of which may vary. In an embodiment, optical aspects of implementations will typically employ optically-oriented hardware, software, firmware, etc., in one or more machines or articles of manufacture. The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely examples, and that in fact, many other architectures can be implemented that achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled,” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably coupleable,” to each other to achieve the desired functionality. Specific examples of operably coupleable include, but are not limited to, physically mateable, physically interacting components, wirelessly interactable, wirelessly interacting components, logically interacting, logically interactable components, etc. In an embodiment, one or more components may be referred to herein as “configured to,” “configurable to,” “operable/operative to,” “adapted/adaptable,” “able to,” “conformable/conformed to,” etc. Such terms (e.g., “configured to”) can generally encompass active-state components, or inactive-state components, or standby-state components, unless context requires otherwise. The foregoing detailed description has set forth various embodiments of the devices or processes via the use of block diagrams, flowcharts, or examples. Insofar as such block diagrams, flowcharts, or examples contain one or more functions or operations, it will be understood by the reader that each function or operation within such block diagrams, flowcharts, or examples can be implemented, individually or collectively, by a wide range of hardware, software, firmware in one or more machines or articles of manufacture, or virtually any combination thereof. Further, the use of “Start,” “End,” or “Stop” blocks in the block diagrams is not intended to indicate a limitation on the beginning or end of any functions in the diagram. Such flowcharts or diagrams may be incorporated into other flowcharts or diagrams where additional functions are performed before or after the functions shown in the diagrams of this application. In an embodiment, several portions of the subject matter described herein is implemented via Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), digital signal processors (DSPs), or other integrated formats. However, some aspects of the embodiments disclosed herein, in whole or in part, can be equivalently implemented in integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g., as one or more programs running on one or more microprocessors), as firmware, or as virtually any combination thereof, and that designing the circuitry or writing the code for the software and or firmware would be well within the skill of one of skill in the art in light of this disclosure. In addition, the mechanisms of the subject matter described herein are capable of being distributed as a program product in a variety of forms, and that an illustrative embodiment of the subject matter described herein applies regardless of the particular type of signal-bearing medium used to actually carry out the distribution. Non-limiting examples of a signal-bearing medium include the following: a recordable type medium such as a floppy disk, a hard disk drive, a Compact Disc (CD), a Digital Video Disk (DVD), a digital tape, a computer memory, etc.; and a transmission type medium such as a digital or an analog communication medium (e.g., a fiber optic cable, a waveguide, a wired communications link, a wireless communication link (e.g., transmitter, receiver, transmission logic, reception logic, etc.), etc.). While particular aspects of the present subject matter described herein have been shown and described, it will be apparent to the reader that, based upon the teachings herein, changes and modifications can be made without departing from the subject matter described herein and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of the subject matter described herein. In general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). Further, if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to claims containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense of the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense of the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). Typically a disjunctive word or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms unless context dictates otherwise. For example, the phrase “A or B” will be typically understood to include the possibilities of “A” or, “B” or “A and B.” With respect to the appended claims, the operations recited therein generally may be performed in any order. Also, although various operational flows are presented in a sequence(s), it should be understood that the various operations may be performed in orders other than those that are illustrated, or may be performed concurrently. Examples of such alternate orderings includes overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, simultaneous, reverse, or other variant orderings, unless context dictates otherwise. Furthermore, terms like “responsive to,” “related to,” or other past-tense adjectives are generally not intended to exclude such variants, unless context dictates otherwise. While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

055984533

summary

BACKGROUND OF THE INVENTION The present invention relates to a method for X-ray fluoroscopy or radiography as well as an X-ray apparatus and more particularly, to a technique which is suitable for three-dimensionally measuring a large view field such as human chest in an X-ray computerized tomography (CT) scan method and an X-ray CT apparatus. As a prior art method for measuring an X-ray fluoroscopic or radiographic image from a plurality of directions to observe or record a stereoscopic dynamic image, a rotational digital angiography (DA) or a rotational digital subtraction angiography (DSA) is described in a journal entitled "Toshiba Medical Review", No. 45, pages 2 to 11, 1992. In the journal, a C arm is provided at its one end with an X-ray image intensifier which is positioned opposed to an X-ray tube so that continuous images appear on a monitor while the C arm is rotated, whereby an operator can observe the stereoscopic dynamic images or acquire DSA images taken from a plurality of directions. As one of general methods for obtaining a completer X-ray three-dimensional image, there is known a method in which tomographic images obtained by an X-ray CT apparatus are connected to each other through image processing. This method however has had a problem that the X-ray CT requires a lot of imaging time. For the purpose of reducing the imaging time, there is advantageously used a cone-beam CT apparatus in which a 2-dimensional X-ray detector is used as an X-ray detector and 2-dimensional transmission images of a subject obtained through X-ray beams emitted from an X-ray source in a cone shape are use to reconstruct a 3-dimensional X-ray image of the subject. Disclosed in a journal entitled "Medical Imaging Technology", Vol. 10, pp. 113-118, 1992 is a cone-beam CT apparatus wherein a 2-dimensional X-ray detector is made up of an X-ray image intensifier and a television camera. Also disclosed in a paper entitled "Development of 3D CT with a large area detection system" of a journal "Radiology", Vol. 185(P), p. 271, 1992 is a large-view-field cone-beam CT apparatus wherein a 2-dimensional X-ray detector is made up of a large-area phosphor screen and a television camera. Known a typical algorithm of reconstructing a 3-dimensional image of a subject in a cone-beam CT apparatus is the Feldkamp's method (refer to a paper "practical cone-beam algorithm" of a journal "Optical Society of America," written by L. A. Feldkamp, et al., A/Vol. 1(6), pp. 612-619, 1984). There are also described in IEEE Transactions on Medical Imaging, Vol. 12, No. 3, pp.486-496, 1993 a method in which an imaging unit including an X-ray source and an X-ray detector is rotated around a subject and at the same time the subject is moved in a direction perpendicular to a rotation plane to enlarge a view field with respect to the rotation-axis direction of the subject, as well as a reconstruction algorithm thereof. SUMMARY OF THE INVENTION In a prior art rotational DA or rotational DSA apparatus, a measuring view field is limited by the size of view field of an X-ray image intensifier. Further, in the apparatus described in the above journal "Medical Imaging Technology," it is difficult from the technical viewpoint to obtain an X-ray image intensifier having a large view field as well as high resolution, and thus also difficult to obtain a large-view-field, high-quality three-dimensional image. For this reason, when it is desired to obtain a high quality image of such a subject under inspection requiring a large view field as human chest, imaging is restricted to only a part of the chest. In addition, with the apparatus described in the above radiology journal, since it is technically difficult to obtain a phosphor screen with a high sensitivity as well as a high resolution, and thus also difficult to acquire a high quality of stereoscopic image with a large view field. Even in an X-ray CT apparatus using an ordinary X-ray detector having detection elements one-dimensionally arranged or in a cone-beam CT apparatus using a 2-dimensional X-ray detector, the view field of a transaxial sectional plane has been so far circular. That is, there has not been suggested so far a technology for overcoming such view field limitation by the size of the detector and for enlarging the view field of the transaxial sectional plane. Accordingly, when such an apparatus is applied to medical examinations, there occurs such a problem that a part of a patient to be examined becomes out of the view field. It is accordingly an object of the present invention to provide a technology for enabling the view field of X-ray fluoroscopic, radiographic or CT images to be enlarged. Another object of the present invention is to provide a technology for enabling the view field of a transaxial sectional plane of a high quality three-dimensional image to be enlarged. A further object of the present invention is to provide a technology by which a high quality of three-dimensional image can be obtained at a high speed. Yet another object of the present invention is to provide an X-ray CT apparatus which can improve a diagnostic ability of lung cancer and so on. These and other objects and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. Typical ones of features of the present invention are summarized as follows. (Feature 1): A fluoroscopic or radiographic method or CT scan method in which a pair of an X-ray source and an X-ray detection unit (including an X-ray detector, an optical lens unit and a television camera) opposed to the X-ray source for detecting an X-ray image is rotated on a circular orbit having an identical rotation center and at the same time a subject is moved in a direction parallel to the rotation plane to perform X-ray fluoroscopic or radiographic operation or CT scan. According to such a CT scan method, there can be obtained a 2-dimensional or 3-dimensional tomographic image on the basis of projection data made of X-rays passed through the subject from a plurality of directions. (Feature 2): In the fluoroscopic or radiographic method or CT scan method having the feature 1, the movement of the subject is a periodical reciprocating movement on a straight line parallel to the rotation plane of the pair of X-ray source and X-ray detection unit, and a period of the reciprocating movement coincides with a period of rotation of the pair of X-ray source and X-ray detection unit. (Feature 3): The movement of the subject is a composite movement corresponding to a combination of a periodical reciprocating movement on a straight line parallel to the rotation plane of the pair of X-ray source and X-ray detection unit and a vertical movement with respect to the rotation plane of the pair of X-ray source and X-ray detection unit. (Feature 4): An X-ray apparatus in which an imaging unit including an X-ray source and an X-ray detection unit opposed to the X-ray source is rotated on a circular orbit having an identical rotation center and at the same time, a subject is moved in a direction parallel to the rotation plane to perform fluoroscopic or radiographic operation or CT scan. (Feature 5): An X-ray apparatus in which an imaging unit including an X-ray source and an X-ray detection unit opposed to the X-ray source is rotated on a circular orbit having an identical rotation center and at the same time, a subject is moved in directions parallel and vertical to the rotation plane to perform fluoroscopic or radiographic operation. (Feature 6): An X-ray apparatus having the feature 4, which further comprises a bed board for limiting a part of the subject to be subjected to the X-ray fluoroscopic or radiographic operation or CT scan, means for performing a reciprocating movement of the bed board on a straight line parallel to the rotation plane, and means for causing a period of the reciprocating movement to coincide a rotation period of the imaging unit. (Feature 7): An X-ray apparatus having the feature 6, which further comprises control means, when the X-ray source is located at a point-symmetric position with respect to the rotation center, for controlling a position of the bed board determining the X-ray fluoroscopic or radiographic or CT scan part of the subject to be located at a point-symmetric position with respect to a middle point of the reciprocating movement of the bed board, and when the X-ray source is located at a line-symmetric position with respect to a straight line passing through the rotation center, parallel to the rotation plane and vertical to the reciprocating movement direction of the bed board, for controlling the bed position to be located at a point-symmetric position with respect to the middle point of the reciprocating movement of the bed board. (Feature 8): An X-ray apparatus having the feature 6 or 7, which further comprises control means, at the same time the pair of the X-ray source and X-ray detection unit is rotated by one turn along a circular orbit from a horizontal position as its start point, for controlling the bed board to be horizontally reciprocated with a center position as a reciprocation start point to perform the X-ray fluoroscopic or radiographic operation or CT scan during the rotation and reciprocating movement, and at the same time the pair of the X-ray source and X-ray detection unit is reversely rotated by one turn along the circular orbit after completion of the X-ray fluoroscopic or radiographic operation or CT scan, for controlling the bed board to again perform the same movement as the reciprocating movement to perform the fluoroscopic or radiographic operation or CT scan during the reverse rotation and reciprocating movement. (Feature 9): An X-ray apparatus having any of the features 1 to 8, wherein the X-ray detection unit including a 2-dimensional detector and an X-ray beam emitted from the X-ray source is a conical beam. (Feature 10): An X-ray apparatus having the feature 9, wherein the X-ray fluoroscopic or radiographic image of a subject is displayed with a single imaginary rotational axis parallel to a rotation axis of the imaging unit and fixed to the subject being always fixed on a display screen, thus realizing an image display method which facilitates inspector's easy observation of the image. (Feature 11): An X-ray apparatus having any of the features 1 to 10, wherein transmission data of a subject detected on the rotation plane of the imaging unit is subjected to a filtering operation in a coordinate system fixed to the imaging unit and the data subjected to the filtering operation is subjected to a back projection with respect to any reconstruction points of and X-ray CT image to thereby perform reconstruction of the X-ray CT image of the subject. In the above imaging system, a coordinate system unique to the present imaging system is realized to perform simple reconstruction. (Feature 12): An X-ray apparatus having any of the features 1 to 11, wherein the transmission data of the subject detected at X-ray input plane position other than the rotation plane of the imaging unit are subjected to a filtering operation on a plane which includes both a straight line present on the X-ray input plane of the X-ray detection means and parallel to the rotation plane and an X-ray generation point in a coordinate system fixed to the imaging unit, and the data after subjected to the filtering operation is subjected to a back projection with respect to a given reconstruction point of an X-ray CT image for reconstruction of the X-ray CT image of the subject, whereby the coordinate system realized in the X-ray CT apparatus set forth in the above feature 11 can be expanded to the entire 3-dimensional space. (Feature 13): An X-ray apparatus having the feature 11 or 12, wherein all the transmission X-ray data of the subject collected through a plurality of rotations of the imaging unit around the subject are subjected to a filtering operation, and the data after subjected to the filtering operation are subjected to the back projection with respect to a given reconstruction point, when data to be back-projected in the back projection is missing in a rotational angle in one of the plurality of rotations, back projection is performed using data obtained in another rotation. As a result, there can be realized such a reconstruction method unique to the present imaging system that the X-ray transmission data of the subject which cannot be collected in one rotation of the imaging unit are compensated for by a plurality of rotations, and the need for rearranging all the transmission data thus collected is eliminated. (Feature 14): An X-ray apparatus having the feature 13, wherein, when a plurality of data to be back-projected is present in a rotational angle in the plurality of turn rotations, the overlapped data are averaged and then back-projected. As a result, there can be realized a reconstruction method for obtaining an X-ray 3-dimensional image having a high S/N ratio with effective use of all the projection data collected by the above imaging unit. (Feature 15): An X-ray apparatus having the feature 13 or 14, wherein, in the course of reconstruction of the X-ray image of a subject, intermediate results of the reconstruction are sequentially displayed in the form of an image, whereby, even in the course of the reconstruction, the user can obtain schematic information on the X-ray CT image. In the X-ray fluoroscopic or radiographic methods an X-ray apparatuses in accordance with the features 1 to 8 for obtaining an X-ray fluoroscopic or radiographic image or CX-ray CT image; since the pair of the X-ray source and X-ray detection unit is moved on the circular orbits having an identical rotation center and at the same time, the subject is moved parallelly to the rotation plane to perform X-ray fluoroscopic or radiographic operation or X-ray CT scan, there can be obtained an X-ray image having an area wider than the view field of the X-ray detector. Thus, the view field of transaxial sectional plane of the X-ray fluoroscopic or radiographic image or X-ray CT image can be enlarged to improve a diagnostic ability such as lung cancer. Further, since the pair of the X-ray source and X-ray detection unit is moved on the circular orbits having an identical rotation center and at the same time, the subject is moved parallelly to the circular orbit plane to perform X-ray fluoroscopic or radiographic operation or X-ray CT scan; there can be obtained a transaxial sectional plane of a high quality of stereoscopic image at high speed. In the X-ray CT scan, in particular, the imaging unit including the X-ray source and X-ray detection unit for obtaining the X-ray transmission image is rotated by a plurality of rotation turns around the subject and at the same time, a relative positional relationship between the rotation center of the imaging unit and the subject is changed in a direction parallel to the rotation plane and this changing method is made different for the respective rotations, so that, of all the data necessary for the reconstruction, the data not able to be collected in one rotation in which the view field of the X-ray detector is smaller than the size of the subject can be all collected in the plurality of turns. When the reconstruction area is limited only to within the rotation plane of the imaging unit to obtain the X-ray 2-dimensional tomographic image of the subject, the reconstruction in the cone-beam CT apparatus is equivalent to the reconstruction in an ordinary X-ray CT apparatus. In the ordinary X-ray CT apparatus, the rotation center of the imaging unit is always fixed to the subject, and a coordinate system having the rotation center as its origin and fixed to the imaging unit is used in the calculation of the reconstruction. In the specification, this coordinate system is referred to as the fixed center coordinate system. The reconstruction using the fixed center coordinate system includes a filtering operation procedure of projection data and a back projection procedure of the projection data after subjected to the filtering operation. This is advantageous in that, since the coordinate system for the imaging unit is the same as that for the reconstruction, the calculation can be simplified. Further, in the case of the ordinary cone-beam CT apparatus, of all reconstruction points of an X-ray 3-dimensional image of a subject, reconstruction points contained within the rotation plane are directly subjected to the fixed center coordinate system, whereas reconstruction points not contained within the rotation plane are also subjected the fixed center coordinate system by regarding a plane, which contains the X-ray generation point and the each reconstruction point, and a intersection line between the plane and detection plane of X-ray detector is parallel to the rotation plane, as approximately the rotation plane, whereby the fixed center coordinate system is expanded to an entire 3-dimensional space for the reconstruction. In the imaging system of the present invention, on the other hand, the rotation center of the imaging unit is always moved with respect to the subject. In the present specification, the then coordinate system of the imaging unit will be referred to as the moving center coordinate system. In order to apply the reconstruction method defined in the above fixed center coordinate system to the projection data collected in the moving center coordinate system for the reconstruction, it is necessary prior to the reconstruction to perform the following operations 1 and 2. (Operation 1): Converts all projection data to projection data defined in the fixed center coordinate system. (Operation 2): Rearranges the projection data for enlargement of view field of the X-ray detector. That is, in the operation 1, the projection data obtained in the moving center coordinate system are converted to the projection data in the fixed center coordinate system. In the operation 2, according to the above X-ray CT imaging system, all the projection data necessary for the reconstruction are obtained through a plurality of rotations of the imaging unit. Accordingly, since the then projection data are collected in the fixed center coordinate system separately for the respective rotations, the operation 2 for rearranging such data is required. However, this method involves problems 1 to 4 which follow. (Problem 1): The operation 1 requires much labor. (Problem 2): The operation 2 requires much labor. (Problem 3): It is impossible to perform the rearrangement of the operation 2 in the entire 3-dimensional space. (Problem 4): The operation 2 cannot be carried out until all the projection data are collected. With regard to the problems 1 and 2, the operations 1 and 2 can be executed at the same time, but the simultaneous execution of the operations 1 and 2 requires much labor and much calculation time. Further, the processor must be complicated. With regard to the problem 3, in the cone-beam CT apparatus for reconstructing the X-ray 3-dimensional image of a subject with use of a 2-dimensional X-ray detector, the projection data of the subject based on X rays irradiated from the X-ray source in a conical shape are used for the reconstruction, which results in that it is impossible to rearrange the projection data in a spatially identical plane. This means that this problem is inherent in the cone-beam CT apparatus, the prior art reconstruction method based on the fixed center coordinate system cannot be applied to the present imaging system, and thus the execution of the above reconstruction is impossible in the prior art reconstruction method. With regard to the problem 4, the operation 2 cannot be executed until all the projection data are collected. Accordingly, the same holds true even for the reconstruction. For this reason, in the course of the data collection, the reconstruction calculation cannot be executed at the same time, with the result that a series of works from the imaging to the display of a reconstructed image takes a lot of time. In accordance with the present invention, all the above problems can be solved by employing a new coordinate system unique to the imaging system of the invention and by employing a new calculation method. The feature 11 has a function of performing the reconstruction with use of the moving center coordinate system fixed to the imaging unit in the above imaging system, whereby the coordinate system unique to the present imaging system can be realized for the reconstruction without the need for the execution of the above operation 1. Accordingly, the above problem 1 can be solved. In this case, the reconstruction procedure, as in the case of the use of the fixed center coordinate system, includes a filtering operation of projection data and a back projection of the projection data after subjected to the filtering operation. The feature 12 has a function of expanding the moving center coordinate system set forth in the feature 11 to an entire 3-dimensional space, whereby the projection data collected in the above imaging system can be used to realize a coordinate system for acquisition of an X-ray 3-dimensional CT image for the subject. The feature 13 has a function of rotating the imaging unit by a plurality of turns and also a function of making up for data lacking in each rotation with use of data obtained in another rotation in the apparatus set forth in the features 11 and 12, whereby there can be realized a calculation method unique to the present imaging system for reconstructing the projection data without rearranging them over the view field of the X-ray detector expanded by the above imaging system. This is a calculation method for performing the reconstruction without the above operation 2, and thus the above problems 2 and 3 can be solved. Other features of the present invention will be explained in the following. (Feature 16): This has a function of discarding some of the projection data after subjected to the filtering operation which are present in the peripheral area of view field of the X-ray detector, thereby realizing a reconstruction method for removing the influence of the projection data correcting filter caused by the view field interrupted in the peripheral area of the view field to obtain an accurater X-ray CT image. This method is advantageous in that the operation can be easily executed, though the view field becomes slightly narrow. (Feature 17): This has a function of making projection data outside the view field of the X-ray detector by an extrapolation method using the projection data obtained within the view field of the X-ray detector before subjected to the filtering operation, whereby the influence of the projection data correcting filter caused by the view field interrupted in the peripheral area of the view field can be suppressed, and there can be obtained a X-ray CT image of a subject in a wider range without discarding the data in the peripheral area of the view field, i.e., without decreasing the view field of the X-ray detector, as in the above feature 16. The feature 14 has a function of performing averaging operation over overlapped some of the projection data of a plurality of rotations at the time of the back projection, thus realizing a reconstruction method for obtaining an X-ray CT image having a high S/N ratio by making the most of the projection data of the subject. (Feature 18): This has a function of performing selecting operation over overlapped some of the projection data of a plurality of rotations at the time of the back projection, thus realizing a reconstruction method for using only some of the projection data of the subject suitable for the reconstruction. (Feature 19): This has a function of, in the selection of the projection data in the feature 18, selecting the projection data of an X ray issued from a farmost position from the reconstruction points of the X-ray CT image, so that, when the reconstruction area is expanded approximately to an entire 3-dimensional space, the expansion can be realized with use of the accuratest approximation. (Feature 20): This has a function of performing sequential reconstructing operation over projection data concurrently with the collection of the projection data of the subject in the X-ray apparatus of the present invention, whereby a series of works from the imaging of the subject to the display of the X-ray CT image can be concurrently executed at high speed. Feature 15 has a function of, even in the course of reconstruction of an X-ray image, sequentially displaying intermediate results of the reconstruction in the X-ray apparatus, whereby, even when urgent evaluation of the reconstruction image is required, the evaluation can be realized with use of the image of the intermediate results of the reconstruction without waiting for the full completion of the reconstruction. In accordance with the present invention, in short, there is provided an X-ray fluoroscopic or radiographic method or an X-ray apparatus wherein the pair of the X-ray tube and X-ray detection unit for obtaining an X-ray image is moved on the circular orbits having an identical rotation center and at the same time, the subject is moved in a direction parallel to the rotation plane to obtain an X-ray fluoroscopic or radiographic image or an X-ray CT image. As a result, the view field of the X-ray fluoroscopic or radiographic image or X-ray CT image can be enlarged. The view field of a high quality of stereoscopic image can be enlarged, for example, with respect to such a target requiring a large view field as human chest. In particular, this is effective for enlargement of the view field of a transaxial sectional plane in the X-ray CT, improving the diagnostic ability of lung cancer or the like. Further, a transaxial sectional plane of a high quality of stereoscopic image can be obtained at high speed.

description

This application claims priority to Japanese JP2009-018668, filed Jan. 29, 2009, and JP 2010-004105, filed Jan. 12, 2010. The entire contents of the above identified applications are incorporated herein by reference. The present invention relates to an extreme ultraviolet light source device. A semiconductor chip may be created, for example, by a reduction projection of a mask on which a circuit pattern has been drawn onto a wafer having a resist applied thereon and by repeatedly performing processing such as an etching and a thin film formation. The progressive reduction of the scale of semiconductor processing demands the use of radiation of a further short wavelength. Thus, a research is being made on a semiconductor exposure technique which uses a radiation of an extremely short wavelength of 13.5 nm or so and a reduction optics system. This type of technique is termed an EUVL (Extreme Ultra Violet Lithography: an exposure using an extreme ultra violet light). Hereafter, an extreme ultraviolet light will be abbreviated as “EUV light”. Three types of EUV light sources are known for example: an LPP (Laser Produced Plasma: plasma produced by a laser) type light source, a DPP (Discharge Produced Plasma) type light source, and an SR (Synchrotron Radiation) type light source. The LPP type light source is a light source which generates a plasma by irradiating a target material with a laser beam, and employs an EUV light that is emitted from this plasma. The DPP type light source is a light source which employs a plasma that is generated by an electrical discharge. The SR (synchrotron radiation) is a light source which uses an orbital radiation. Of those three types of light sources, the LPP type light source is more likely to obtain an EUV light of a higher output power as compared to the other two types because the LPP type light source can provide an increased plasma density and can ensure a larger solid angle over which the light is collected (see Patent Citation 1). For the EUV light source device of the LPP type, a metal such as tin (Sn) is used as a target material in large part. The EUV light source device of the LPP type is provided with a target supply device. The target supply device heats and melts tin, and makes tin blow out as a droplet from a nozzle having a minor diameter. It is known that an oxide film is formed on the surface of a stainless steel in a field of a solder bath in which a so-called lead-free solder is used although it is irrelevant to the technical field of an extreme ultraviolet light source device (see Patent Citation 2 and Patent Citation 3). Moreover, a technique in which a target material is collected for a recycle is also known (see Patent Citation 4). Patent Literature [Patent Citation 1] Japanese Patent Application Laid-Open Publication No. 2006-80255[Patent Citation 2] Japanese Patent Application Laid-Open Publication No. 2004-188449[Patent Citation 3] Japanese Patent Application Laid-Open Publication No. 2004-52075[Patent Citation 4] Japanese Patent Application Laid-Open Publication No. 2008-226462 The target supply device is formed by a stainless steel that is excellent in a pressure resistance property and a thermal conductivity. However, since tin has a high reactivity, an inner wall that comes into contact with tin is eroded by tin in the case in which the target supply device is used continuously. Consequently, component materials of a stainless steel (Fe, Cr, and Ni for instance) or impurities of a stainless steel and a target material (sulfur (S) and oxygen (O) for instance) are reacted with tin to be a solid body. Particles of the reacted solid body cause a nozzle to be choked or clogged. In the case in which a nozzle is choked or clogged, it is impossible to make a droplet in a stable shape blow out to an accurate position at an accurate speed. As a result, a target (droplet) cannot be irradiated with a driver laser beam, and a light focusing point of a laser beam cannot be easily corresponded to the center of a droplet disadvantageously. Consequently, the following two problems arise. At first, more debris occurs, whereby an EUV light collector mirror is damaged and a lifetime of the mirror is shortened. Second, the conversion efficiency of an EUV light is reduced and varied, and an energy of a generated EUV light is reduced and a stability of an energy is degraded. Moreover, in the Patent Citation 3 (JP-A-2004-52075), a surface roughness (Ra) on an oxidation layer side is specified to be in the range of 2 to 50 μm. In the case of a solder bath, there is less necessity to being conscious of a size of a particle. However, for an extreme ultraviolet light source device, since a target is ejected from a nozzle having an extremely minor diameter, a size of a particle leads to a problem. The present invention was made in consideration of the above problems, and an object of the present invention is to provide an extreme ultraviolet light source device in which a stable extreme ultraviolet light of a high output power can be generated by stabilizing a supply (a generation) of a target material. Another object of the present invention is to provide an extreme ultraviolet light source device wherein in an inner surface of a device related to a target supply, a region that comes into contact with a target material is coated, a substrate that includes a surface that comes into contact with a target material is formed by using a prescribed material for the substrate or a configuration is made by a combination thereof to prevent a particle that is reacted with a surface coming into contact with a target material and that clogs a nozzle from being generated and to stable a generation of a target whereby a stable EUV light of a high output power can be generated. Other objects of the present invention will be clarified by the explanation of the modes described later. In order to solve the above problems of the conventional art, an extreme ultraviolet light source device in accordance with a first aspect of the present invention is an extreme ultraviolet light source device that generates an extreme ultraviolet light by irradiating a target with a laser beam, comprising a chamber; a target generating unit that generates the target from a target material and supplies the generated target into the chamber; and a laser light source that generates an extreme ultraviolet light by irradiating the target in the chamber with a laser beam, wherein a specific region that comes into contact with the target material in the target generating unit is provided with an erosion resistance property and a corrosion resistance property to the target material. Here, the erosion means being physically cut. For instance, in the case in which a target material is flown in a region that comes into contact with the target material, the surface of the region that comes into contact with the target material is physically abraded. As a result, a particle that has been cut from the surface is generated, and a nozzle that outputs a target is clogged with the particle disadvantageously. The erosion resistance property means that the surface of the region that comes into contact with the target material is less physically abraded. On the other hand, the corrosion means being cut by a chemical reaction. For instance, the surface of the region that comes into contact with a target material is reacted with the target material to form an alloy or a compound. The alloy or the compound is entrained into the target material. As a result, a material (an alloy or a compound) that has been chemically reacted with the surface of the region is entrained into the target material as a particle, and a nozzle is clogged with the particle disadvantageously. The corrosion resistance property means that the surface of the region that comes into contact with the target material is less chemically reacted with the target material. To achieve an erosion resistance property, it is necessary that the surface of the region that comes into contact with the target material is hard and a surface roughness is small to be a prescribed surface roughness. For instance, it is preferable that the prescribed surface roughness is specified in such a manner that a diameter of a particle generated in the specific region is 1 micron meter or less. This is because a particle having a diameter of 1 micron meter or less does not cause the clogging of a nozzle (having a diameter of 6 micron meter for instance) of a target generating unit. The specific region is polished by any one of a chemical polishing, an electrolytic polishing, a barrel polishing, a magnetic polishing, and a physical polishing, or a combination thereof to obtain the prescribed surface roughness. When a specific region is produced, the specific region is polished to have a prescribed surface roughness. In the case in which the specific region is worn by using the target generating unit, the specific region is polished again to have a prescribed surface roughness. Moreover, the specific region can also be polished on a periodic basis according to an operating time of the target generating unit in such a manner that the specific region has a prescribed surface roughness. For instance, the target material consists chiefly of tin, and the specific region is a region that may potentially come into contact with tin in a molten state. The specific region can also be provided with a plurality of regions having different configurations associated with the erosion resistance property. The specific region can also be provided with a first region in which a surface part that comes into contact with the target material is formed by a prescribed material for a surface and a second region in which the entire of a substrate part including the surface part is formed by a prescribed material for a substrate. The specific region can also be provided with a region that is formed on a flat surface part and a region that is formed on a surface part having concavity and convexity. The specific region can also be coated by a prescribed material for a surface. The substrate part including the specific region can also be formed by a prescribed material for a substrate. The prescribed region can also be coated by a prescribed material for a surface in the case in which a surface treatment can be relatively easily carried out for the prescribed region, and the substrate part including the prescribed region can also be formed by a prescribed material for a substrate in the case in which a surface treatment cannot be relatively easily carried out for the prescribed region. The prescribed material for a surface can also contain at least one of a metal nitride, a metal oxide, metal carbide, molybdenum, tungsten, ceramics, titanium, a diamond, a carbon graphite, and quartz. In this case, a substrate material can also be made of a stainless steel or a carbon steel. The prescribed material for a substrate can also contain at least one of a crystal that consists chiefly of molybdenum, a crystal that consists chiefly of titanium, a crystal that consists chiefly of tantalum, a crystal that consists chiefly of a diamond, a crystal that consists chiefly of a carbon steel, and a crystal that consists chiefly of alumina. By the present invention, a prescribed region that comes into contact with a target material is provided with an erosion resistance property and a corrosion resistance property to the target material. Consequently, the target generating unit can be suppressed from being physically eroded and being chemically corroded by the target material. As a result, a performance of the target generating unit can be prevented from being degraded. Moreover, the target generating unit can be prevented from being clogged by specifying the prescribed region to have a prescribed surface roughness for achieving the erosion resistance property. By the present invention, only a surface that comes into contact with the target material can be coated with a prescribed material for a surface and/or the entire of a substrate part including the surface that comes into contact with the target material can be formed by a prescribed material for a substrate. Consequently, a prescribed region that comes into contact with a target material can be provided with an erosion resistance property and a corrosion resistance property to the target material by a suitable method based on a processability of a surface treatment for instance. A mode for the present invention will be described below in detail with reference to the drawings. In the mode for the present invention, a prescribed region that comes into contact with the target material is provided with an erosion resistance property and a corrosion resistance property to the target material as described below. For instance, in a target generating unit, a target material collecting device, and a target material supply device, a region that comes into contact with the target material in a molten state is provided with an erosion resistance property and a corrosion resistance property. A first embodiment of the present invention will be described in the following with reference to FIGS. 1 to 3. FIG. 1 is an explanatory diagram showing a general configuration of an EUV light source device 1. The EUV light source device 1 can be configured to be provided with, for example, a vacuum chamber 100, a driver laser light source device 110, a target generating unit 120, magnetic field generating coils 140 and 141, an EUV light collector mirror 150, bulkhead apertures 160 and 161, a gate valve 170, and a vacuum pump 190. The vacuum chamber 100 can be configured by connecting a first chamber 101 having a large volumetric capacity and a second chamber 102 having a small volumetric capacity. The first chamber 101 is a main chamber that carries out a generation of plasma and so on. The second chamber 102 is a connecting chamber that supplies an EUV light that is emitted from plasma to an exposure device not shown. A vacuum pump 190 is connected to the first chamber 101. By this configuration, the vacuum chamber 100 can be maintained to be in a vacuum state. Moreover, the second chamber 102 can also be configured to be provided with another vacuum pump. In that case, debris can be suppressed from flowing to the exposure device side by setting a pressure in the first chamber 101 to be less than a pressure in the second chamber 102. The target generating unit 120 heats and melts a material such as tin (Sn), and supplies a target 201 as a droplet in a state of solid or liquid. The target generating unit 120 can be configured to be provided with a nozzle part 121 and a tank part 122. Tin as a target material is supplied from an external part to the tank part 122. The tank part 122 can be configured to be provided with a heating device 124 such as a heater (see FIG. 2) and can heat tin to be in a molten state. An argon gas tank 301 is connected to the tank part 122 via a valve 302 for instance. An argon gas is used as a blowout gas that makes a target blow out from the nozzle part 121. In the case in which the valve 302 is opened, an argon gas is supplied into the tank part 122. Tin in a molten state in the tank part 122 is made blow out from the nozzle part 121 into the chamber 100 due to a pressure of the argon gas. As described later, a vibration is applied in a continuous manner to tin that is made blow out as a jet stream from the nozzle part 121 whereby a droplet 201 made of tin can be generated. As a blowout gas, not only an argon gas but also another inert gas that absorbs less EUV lights L2 can be used. An exhaust pump 303 is connected to the tank part 122 via a valve 304. In the case in which an air release is carried out for the purpose of supplying tin to the tank part 122, a valve 304 is opened and the exhaust pump 303 is operated. By this step, an air in the tank part 122 is exhausted, thereby preventing tin from being oxidized in heating tin. A driver laser light source 110 outputs a driver laser beam L1 that excites the target 201 that is supplied from the target generating unit 120. The driver laser light source 110 can be configured as a CO2 (carbon dioxide gas) pulse laser light source for instance. The driver laser light source 110 emits a driver laser beam L1 having the specifications of a wavelength of 10.6 μm, an output power of 20 kW, a pulse repetition rate of 100 kHz, and a pulse width of 20 nsec. In the present embodiment, a CO2 pulse laser is described for example as a laser light source. However, a laser light source of the present invention is not limited to the CO2 pulse laser. The driver laser beam L1 that is output from the driver laser light source 110 for an excitation is incident to the first chamber 101 via a light focusing lens 111 and an incident window 112. The driver laser beam L1 that has been incident to the first chamber 101 passes through an incident hole 152 formed in an EUV light collector mirror 150, and a target 201 is irradiated with the driver laser beam L1. In the case in which a target 201 is irradiated with the driver laser beam L1, the tin target 201 is changed to a target plasma 202. Hereafter, a target plasma 202 is simply referred to as a plasma 202 as a matter of practical convenience. The plasma 202 emits an EUV light L2 having a center wavelength of 13.5 nm. The EUV light L2 that has been emitted from the plasma 202 is incident to the EUV light collector mirror 150 and reflected by the EUV light collector mirror 150. The EUV light L2 that has been reflected by the EUV light collector mirror 150 is focused at a position of an intermediate light focusing point (IF: Intermediate Focus) in the second chamber 102. The EUV light L2 that has been focused to the IF is guided to an exposure device via a gate valve 170 in an open state. A pair of magnetic field generating coils 140 and 141 is disposed in such a manner that a light path of the EUV light L2 traveling from the plasma 202 to the IF via the EUV light collector mirror 150 is sandwiched between the magnetic field generating coils 140 and 141. The shaft centers of the magnetic field generating coils 140 and 141 are corresponded to each other. The magnetic field generating coils 140 and 141 can be configured to be an electromagnet provided with a superconducting coil for instance. In the case in which an electric current is flown in the same direction to each of the magnetic field generating coils 140 and 141, a magnetic field is generated. The magnetic field is generated in the vertical direction of FIG. 1. A magnetic flux density is higher around the magnetic field generating coils 140 and 141, and a magnetic flux density is lower at an intermediate point of the magnetic field generating coils 140 and 141. In the case in which the target 201 is irradiated with the driver laser beam L1, debris is generated. The electrically charged debris (an ion such as plasma) is trapped by a magnetic field that is generated by each of the magnetic field generating coils 140 and 141. The electrically charged debris is moved in a spiral pattern due to Lorentz force toward the lower side of FIG. 1, and is collected by a target collecting device 180. The installation location of the magnetic field generating coils 140 and 141 can be a location in which ionic debris is prevented from reaching the surface of the EUV light collector mirror 150 and is output due to a magnetic line of force that is generated by the magnetic field generating coils 140 and 141. Among a large number of targets 201 that have been generated by the target generating unit 120, a target that has not been irradiated with the driver laser beam L1 is also collected by a target collecting device 180. In FIG. 1, an unused target is numbered as 203. A reason of a generation of the unused target 203 will be described below. A target that is not irradiated with the driver laser beam L1 (the unused target 203) is intentionally input in some cases in order to prevent debris from affecting the next target 203. As another reason, a repetition rate of the driver laser beam L1 and a rate for stably generating a target 201 having a desired diameter are not corresponded to each other in some cases. In this case, a generating rate of a target 201 is specified to be the integral multiple of a repetition rate of the driver laser beam L1. By this step, a generation of the target 201 and an irradiation of the driver laser beam L1 are synchronized with each other. In the description of the present embodiment, a generating cycle of the target (a droplet) 201 is synchronized with a double of a repetition cycle of the driver laser beam L1. For instance, in the case in which the target 201 of φ tens of μm is irradiated with the driver laser beam L1 of 100 kHz, a target generating rate is 200 kHz, and targets 201 of at least 90% of a large number of targets 201 blown out from the target generating unit 120 are not irradiated with the driver laser beam L1 and become unused targets 203. In the description of the present embodiment, the target collecting device 180 is disposed at the bottom of the first chamber 101 to collect an unused target 203. The collected unused target 203 is then supplied to the target generating unit 120 to be recycled. Two bulkhead apertures 160 and 161 and an IF aperture 162 are disposed in the vicinity of the IF. The IF aperture 162 is disposed at the position of the IF, and is formed to be larger than an IF image to a certain degree. A first bulkhead aperture 160 is disposed on the front side of the IF, and a second bulkhead aperture 161 is disposed on the rear side of the IF in a traveling direction of the EUV light L2 that has been reflected by the EUV light collector mirror 150. The IF aperture 162 is disposed between the bulkhead apertures 160 and 161. The bulkhead apertures 160 and 161 are provided with an opening part in the range of several mm to 10 mm for instance. Moreover, a diameter of the IF aperture 162 is approximately several mm. The first bulkhead aperture 160 is disposed close to the location in which the first chamber 101 and the second chamber 102 are connected to each other. The second bulkhead aperture 161 is disposed close to the location in which the second chamber 102 and an exposure device are connected to each other. In other words, the IF is configured to be located in the second chamber 102 other than the first chamber 101, and the bulkhead apertures 160 and 161 are disposed in such a manner that a partition is formed in the vicinity of the IF. An SPF (Spectrum Purity Filter) can also be formed on any one or both of the front side and the rear side of the IF to block a light having a wavelength other than 13.5 nm. FIG. 2 is an enlarged cross-sectional view showing the target generating unit 120. A gas inflow port 123 is formed on the upper section of the tank part 122 that is configured as a high-pressure tank. The gas inflow port 123 is connected to the argon gas tank 301 via the valve 302. An argon gas flows from the gas inflow port 123 into the tank part 122, and pressurizes tin in a molten state that is a target material 200. By this step, tin in a molten state is forced out of the nozzle part 121. A heating device 124 is disposed on the periphery of the tank part 122 and the nozzle part 121. The heating device 124 is provided with a heating source such as a heater and a temperature controller that adjusts an amount of heat generation of the heating source corresponding to a detection signal from a temperature sensor. The heating device 124 heats tin in the target generating unit 120 to be a temperature in the range of 230° C. to 400° C. to make tin in a molten state. A vibration generating unit 125 is formed around an injection port of the nozzle part 121. The vibration generating unit 125 can be configured to be provided with a vibration generating element such as a piezo element. The nozzle part 121 vibrates by an operation of the vibration generating unit 125. In the case in which a tin jet in the form of a liquid (not shown) is injected while the nozzle part 121 vibrates, a target 201 in the form of a droplet is generated. FIG. 3 is an enlarged cross-sectional view showing a part of FIG. 2 (for instance, a region shown by III in FIG. 2). The target generating unit 120 can be configured to be provided with a substrate part 400 and a plurality of layers 401 and 402 that are formed on the inner surface side of the substrate part 400. The substrate part 400 is made of, for example, a stainless steel, molybdenum (Mo), titanium (Ti), or tantalum (Ta). In the case in which the target generating unit 120 is not in a high magnetic field, a carbon steel can also be used as a material of the substrate part 400. The substrate part 400 can also be called a base material part. Moreover, the entire of the substrate part 400 can also be made of molybdenum. The inner surface of the substrate part 400 comes into contact with tin. A first protective layer 401 is formed on the inner surface of the substrate part 400. A second protective layer 402 is formed in such a manner that the second protective layer 402 covers the first protective layer 401. For instance, the first protective layer 401 is a metal nitride layer such as a chromium nitride layer, which has a hard characteristic. The second protective layer 402 is a metal oxide layer, which has a function for suppressing a corrosion caused by tin. The second protective layer 402 can be formed by oxidizing the surface of the first protective layer 401. The first protective layer 401 can be formed to have a thickness t1 in the range of more than a dozen μm to a hundred and several tens of μm. A thickness t2 of the second protective layer 402 is specified to be smaller than a thickness t1 of the first protective layer 401. In the illustration of FIG. 3, a thickness of the first protective layer 401 is almost equivalent to that of the second protective layer 402 as a matter of practical convenience. As a material of the first protective layer 401, a metal nitride, molybdenum, tungsten (W), carbide, alumina ceramics (Al2O3), a diamond, titanium, a carbon graphite, and quartz can be used for instance. In the case of a material that is easily oxidized among the above materials, the second protective layer 402 can be formed in the course of nature. In the case of a material that is hard to be oxidized, the material is provided with both of a mechanical strength and an erosion resistance property to tin. The first protective layer 401 (or the second protective layer 402) is specified to have a prescribed surface roughness in such a manner that a diameter of a particle that can be generated in the first protective layer 401 is 1 micron meter or less. The surface of the first protective layer 401 is polished by any one of a chemical polishing, an electrolytic polishing, a barrel polishing, a magnetic polishing, and a physical polishing, or a combination thereof to achieve the prescribed surface roughness. In the case in which the surface of the first protective layer 401 is polished to have a prescribed surface roughness, the second protective layer 402 that is an oxide film can have a prescribed surface roughness. Each of the above polishing methods will be described in the following. A chemical polishing is a method for chemically polishing a surface in acid or an alkaline solution. An electrolytic polishing is a method for removing a burr on a surface of an object to be polished by making an electrolytic solution flow between an electrode of the object to be polished on a plus side and an electrode on a minus side opposite to the object to be polished for a current conduction. A barrel polishing is a method in which an object to be polished, a polishing stone, and a compound solution are mixed at a prescribed ratio and filled into a polishing bath called a barrel bath, and the object is polished by using a difference in relative movements in the polishing bath. A magnetic polishing is a method in which the magnetic media and an object to be polished are input to a polishing bath and the magnetic media is moved by a magnetic field to polish the object to be polished. In the present embodiment that is configured as described above, since a metal oxide layer 402 is formed on the inner wall of the target generating unit 120, even in the case in which a target is made blow out for a long period of time, the inner wall can be suppressed from being eroded and corroded by tin in a molten state. As a result, the nozzle part 121 can be prevented from being clogged by impurities. Consequently, the target 201 in a stable shape can be made blow out in an accurate direction at a stable speed, and a droplet can be supplied at a desired position of an EUV luminous point and at a desired timing. Therefore, in the present embodiment, a performance of the extreme ultraviolet light source device can be prevented from being degraded, and a reliability of the extreme ultraviolet light source device can be improved. Moreover, in the present embodiment, the first protective layer 401 (or the second protective layer 402) is specified to have a prescribed surface roughness in such a manner that a diameter of a particle that can be generated in the first protective layer 401 is 1 micron meter or less, whereby a size of a particle can be controlled. Consequently, even in the case in which a particle is generated, the nozzle part 121 can be prevented from being clogged by the particle before happens, whereby a stability of a droplet supply and a reliability of the extreme ultraviolet light source device can be improved. In each of embodiments described later, it is preferable that a degree of roughness of a surface that comes into contact with a target material is controlled to be a prescribed value. More specifically, a surface roughness (a surface roughness degree) of a region that comes into contact with a target material is specified to be a value of 1/10 or less of a diameter of a nozzle that emits a target material. By this configuration, the nozzle can be prevented from being clogged, and a stability of a target material that is output from the nozzle can be improved. For instance, in the case in which a diameter of a nozzle is 10 μm, a surface roughness Ra is specified to be 1 μm or less. Moreover, by specifying a surface roughness to be 1/100 or less of a diameter of a nozzle (for instance, Ra=0.10 μm), a target stability can be obtained with a higher degree of accuracy. A second embodiment of the present invention will be described in the following with reference to FIG. 4. Each embodiment that will be described in the following corresponds to a modified example of the first embodiment. Consequently, some points that are different from the first embodiment will be described mainly. In the present embodiment, only one protective layer 403 is formed on the inner surface of the substrate part 400. The protective layer 403 made of a material such as a diamond, molybdenum, titanium, tungsten, a metal nitride, carbide, alumina ceramics, a carbon graphite, and quartz, which are provided with an erosion resistance property to tin. The present embodiment that is configured as described above has an operation effect equivalent to that of the first embodiment. A third embodiment of the present invention will be described in the following with reference to FIG. 5. In the present embodiment, after the inner surface of the substrate part 400 is roughened by a processing such as a shot blasting, a first protective layer 401A and a second protective layer 402A are formed. Since the first protective layer 401A and the second protective layer 402A are formed on the inner surface that has been roughened, the layers 401A and 402A also have a roughened surface having concavity and convexity. By this configuration, tin can be prevented from adhering to the surface of the second protective layer 402A. The present embodiment that is configured as described above has an operation effect equivalent to that of the first embodiment. A fourth embodiment of the present invention will be described in the following with reference to FIG. 6. In the present embodiment, the inner surface of the substrate part 400 is roughened, and two sets of a pair of a first protective layer 401A and a second protective layer 402A are formed. More specifically, a first protective layer 401A (1) and a second protective layer 402A (1) are formed on the roughened inner surface of the substrate part 400, and the other first protective layer 401A (2) and the other second protective layer 402A (2) are formed on the layers 401A (1) and 402A (1). In the present embodiment that is configured as described above, since a plurality of pairs of a first protective layer 401A and a second protective layer 402A are formed, an erosion caused by tin can be suppressed for a longer period of time, and a reliability of the extreme ultraviolet light source device can be further improved. Moreover, three sets or more of a pair of a first protective layer 401A and a second protective layer 402A can also be formed. A fifth embodiment of the present invention will be described in the following with reference to FIG. 7. In the present embodiment, the tank part 122 and the nozzle part 121 have different configurations associated with an erosion resistance property. For the tank part 122, as described in FIG. 5, the inner surface of the substrate part 400 is roughened, and a first protective layer 401A and a second protective layer 402A are formed. On the other hand, for the nozzle part 121, as described in FIG. 3, a first protective layer 401 and a second protective layer 402 are formed on the flat inner surface of the substrate part 400. The present embodiment that is configured as described above has an operation effect equivalent to that of the first embodiment. Moreover, in the present embodiment, the first protective layer 401A and the second protective layer 402A that protect the inner surface of the tank part 122 are roughened, and the first protective layer 401 and the second protective layer 402 that protect the inner surface of the nozzle part 121 are formed in an even pattern. Consequently, a solidified particle that has been reacted with tin can be prevented from reaching the nozzle part. As a result, for the nozzle part 121, a direction and a speed of an injection of a target 201 can be stabilized. A sixth embodiment of the present invention will be described in the following with reference to FIGS. 8 and 9. In the present embodiment, the tank part 122 and the nozzle part 121A are formed as separate members. FIG. 8 is a cross-sectional view showing a configuration of the target generating unit 120. The nozzle part 121A is formed as a member separate from the tank part 122, and is fixed to the bottom face of the tank part 122 by a fixing means such as a welding. Moreover, the contact surface of the nozzle part 121A and the tank part 122 can also be processed in such a manner that a surface roughness becomes small, and the both parts can be made come into contact with each other by being pressed from the outside to be fixed to each other. FIG. 9 is a cross-sectional view showing a configuration of the nozzle part 121A and the tank part 122. As described in FIG. 5, for the tank part 122, the inner surface of the substrate part 400 is roughened, and a first protective layer 401A and a second protective layer 402A are formed on the substrate part 400. On the other hand, the substrate part 404 of the nozzle part 121A is made of a material such as a crystal that consists chiefly of molybdenum, a crystal that consists chiefly of titanium, a crystal that consists chiefly of tungsten, a crystal that consists chiefly of a diamond, a crystal that consists chiefly of a metal nitride, a crystal that consists chiefly of carbide, a crystal that consists chiefly of alumina ceramics, a crystal that consists chiefly of a carbon graphite, a crystal that consists chiefly of quartz, and a crystal that consists chiefly of alumina, which are provided with an erosion resistance property and a corrosion resistance property to tin, a pressure resistance property, and a heat resistance property. As an example of a crystal that consists chiefly of alumina, a crystal of ruby and a crystal of sapphire can be mentioned for instance. The present embodiment that is configured as described above has an operation effect equivalent to that of the first embodiment. Moreover, in the present embodiment, the nozzle part 121A is formed as a member separate from the tank part 122, and the nozzle part 121A and the tank part 122 are configured to be provided with an erosion resistance property and a corrosion resistance property to tin according to separate methods. Consequently, the minute nozzle part 121A to which a surface treatment is relatively hard to be carried out can be provided with an erosion resistance property to tin to a satisfactory extent. A seventh embodiment of the present invention will be described in the following with reference to FIG. 10. In the present embodiment, a nozzle holder 122A is formed on the leading end side of the tank part 122, and the nozzle part 121B is mounted into the nozzle holder 122A. A first protective layer 401 and a second protective layer 402 are formed on the inner surface of the tank part 122. The entire of the nozzle part 121B is made of a material provided with an erosion resistance property and a corrosion resistance property to tin, a pressure resistance property, and a heat resistance property. The present embodiment that is configured as described above has an operation effect equivalent to that of the first and sixth embodiments. Moreover, in the present embodiment, a nozzle holder 122A is formed on the lower side of the tank part 122, and the nozzle part 121B is mounted to the nozzle holder 122A. Consequently, the nozzle part 121B can be formed to be smaller as compared with the sixth embodiment. By this configuration, a used amount of costly materials such as a crystal that consists chiefly of molybdenum, a crystal that consists chiefly of titanium, a crystal that consists chiefly of tungsten, a crystal that consists chiefly of a diamond, a crystal that consists chiefly of a metal nitride, a crystal that consists chiefly of carbide, a crystal that consists chiefly of alumina ceramics, a crystal that consists chiefly of a carbon graphite, a crystal that consists chiefly of quartz, and a crystal that consists chiefly of alumina can be less, thereby reducing a production cost. An eighth embodiment of the present invention will be described in the following with reference to FIG. 11. In the present embodiment, the nozzle part 121C in a funnel shape is mounted into the nozzle holder 122B that has been formed on the lower side of the tank part 122. The present embodiment that is configured as described above has an operation effect equivalent to that of the first, sixth, and seventh embodiments. Moreover, in the present embodiment, a region to which a surface treatment is relatively hard to be carried out in the tank part 122, that is, a part in a turned conical shape can be protected by the nozzle part 121C in a funnel shape. A ninth embodiment of the present invention will be described in the following with reference to FIG. 12. In the present embodiment, the target generating unit 120 is made of the same substrate. More specifically, the tank part 122 and the nozzle part 121 are made of the same substrate. A vibration generating unit 125 is disposed outside the nozzle part 121. A heating device 124 is disposed in such a manner that the heating device 124 covers the periphery of the tank part 122 and the nozzle part 121 that are made of the same substrate. The substrate is made of a material such as a crystal that consists chiefly of molybdenum, a crystal that consists chiefly of titanium, a crystal that consists chiefly of tungsten, a crystal that consists chiefly of a diamond, a crystal that consists chiefly of a metal nitride, a crystal that consists chiefly of carbide, a crystal that consists chiefly of alumina ceramics, a crystal that consists chiefly of a carbon graphite, a crystal that consists chiefly of quartz, and a crystal that consists chiefly of alumina, which are provided with an erosion resistance property and a corrosion resistance property to tin, a pressure resistance property, and a heat resistance property. As an example of a crystal that consists chiefly of alumina, a crystal of ruby and a crystal of sapphire can be mentioned for instance. Tin in the target generating unit 120 is heated up to a temperature of at least 230° C. by the heating device 124 to be a molten metal. An Ar gas is introduced from the gas inflow port 123, and pressurizes a liquid level of tin in a molten state. By this step, a metal in a molten state can be output. By applying a vibration to the nozzle part 121 by an operation of the vibration generating unit 125, a droplet 201 having a small diameter is generated. As described above, an inner surface of a substrate that comes into contact with tin in a molten state is polished in order to suppress a generation of a particle. A surface roughness of a surface that comes into contact with tin in a molten state is specified to be a value of 1/10 or 1/100 or less of a diameter of a nozzle. By this configuration, the nozzle part 121 can be prevented from being clogged, and a stability of a target material that is output from the nozzle can be improved. A tenth embodiment of the present invention will be described in the following with reference to FIGS. 13 and 14. As shown in the whole block diagram of FIG. 13, the extreme ultraviolet light source device 1A in accordance with the present embodiment is provided with a target material supply device 130 that automatically supplies tin as a target material to the target generating unit 120. The target material supply device 130 is provided with a target supply device body 1301 and a supply pipe line 1302 that connects between the target supply device body 1301 and the tank part 122 of the target generating unit 120. FIG. 14 is a cross-sectional view showing a target material supply device 130. A first protective layer 401 and a second protective layer 402 are formed on the inner surface of the substrate part 400 of the target supply device body 1301. Tin in a molten state or in a state of solid is held in the target supply device body 1301. The supply pipe line 1302 is attached to the lower side of the target supply device body 1301. The substrate part 404 of the supply pipe line 1302 is made of a material such as a crystal that consists chiefly of molybdenum, a crystal that consists chiefly of titanium, a crystal that consists chiefly of tungsten, a crystal that consists chiefly of a diamond, a crystal that consists chiefly of a metal nitride, a crystal that consists chiefly of carbide, a crystal that consists chiefly of alumina ceramics, a crystal that consists chiefly of a carbon graphite, a crystal that consists chiefly of quartz, and a crystal that consists chiefly of alumina, which are provided with an erosion resistance property and a corrosion resistance property to tin, a pressure resistance property, and a heat resistance property. The present embodiment that is configured as described above has an operation effect equivalent to that of the first embodiment. Moreover, in the present embodiment, the extreme ultraviolet light source device is provided with a target material supply device 130 that supplies a target material to the target generating unit 120, and a surface that comes into contact with tin in the target material supply device 130 is configured to be provided with an erosion resistance property and a corrosion resistance property to tin. Consequently, since a target material of a sufficient amount can be used, a target can be ejected for a long period of time. Moreover, even in the case in which a target is ejected for a long period of time, the target material supply device 130 and the target generating unit 120 can be suppressed from being eroded and corroded by tin. As a result, even in the case in which the extreme ultraviolet light source device 1A is operated for a long period of time, a reliability of the extreme ultraviolet light source device 1A can be maintained. An eleventh embodiment of the present invention will be described in the following with reference to FIG. 15. In the present embodiment, an unused target 203 that has been collected is returned to the target generating unit 120, whereby a target material can be used in an effective manner and a continuous operating time of the extreme ultraviolet light source device 1B can be lengthened. For a comprehension of the present embodiment, the description of Japanese Patent Application Laid-Open Publication No. 2008-226462 can be referred to as needed. An argon gas tank 501 is connected to the upper side of a target collecting device 180A (an inflow side of an unused target 203) via a valve 503. A vacuum pump 502 is connected to the lower side of the target collecting device 180A (an outflow side of an unused target 203) via a valve 504. By an argon gas that flows from the upper side to the lower side in the target collecting device 180A, an unused target 203 in a molted state is cooled and solidified in the target collecting device 180A. By this configuration, the collector mirror 150 and so on can be prevented from being contaminated by a target material that is generated from the unused target 203. A plurality of opening boards 181 are formed separately in an axial direction on an inner circumferential surface of the target collecting device 180A. A hole in which the unused target 203 passes through is formed at the center part of each opening board. A size of the hole of each opening board 181 is specified to be smaller for a board disposed at a lower location. By the opening boards 181, an argon gas in the target collecting device 180A can be suppressed from leaking in the chamber 101. The unused target 203 that has passed through a hole of each opening board 181 is collected in a collection part 182 that collects a target material. The unused target 203 that has been collected is supplied to a target regenerating device 184 via a gate valve 183. The target regenerating device 184 is a device that regenerates the unused target 203, and is connected to the lower side of the target collecting device 180A. The target regenerating device 184 is provided with a temperature sensor 187 and a heating device 188. The heating device 188 heats the unused target 203 that has been supplied into the target regenerating device 184 to be a temperature in the range of 230° C. to 400° C. to convert the unused target 203 to a target material 200 in a molten state. An argon gas tank 301 is connected to the target regenerating device 184 via a valve 305. Moreover, a vacuum pump 307 is connected to the target regenerating device 184 via a valve 306. By supplying an argon gas from the argon gas tank 301 to the target regenerating device 184 and pressurizing the argon gas in the state in which the gate valve 183 is closed, the target material 200 in a molten state is transferred to the target generating unit 120 via a pipe 311 or the like. An argon gas in the target regenerating device 184 is exhausted by the vacuum pump 307, and a pressure in the target regenerating device 184 is reduced. In the case in which the gate valve 183 is then opened, the unused target 203 that has been stored into the target collection part 182 flows into the target regenerating device 184. A suction pipe 186 that suctions the target material 200 in the target regenerating device 184 is formed in such a manner that the suction pipe 186 is protruded upward from the lower side of the target regenerating device 184. A dome 185 is formed in such a manner that the dome 185 covers an admission port of the suction pipe 186. Since an impurity floats around a liquid level of the target material 200 in a molten state, the dome 185 covers the suction pipe 186 in order to prevent an impurity from being suctioned. The suction pipe 186 is connected to the pipe 311 via a valve 310. A heating unit 312 such as a heater is disposed on the periphery of the pipe 311. By this configuration, the target material 200 in a molten state (tin in a molten state) that has been suctioned from the suction pipe 186 is supplied in a molten state to the target generating unit 120. Moreover, in the present embodiment, a filter 600 is disposed along the path of the pipe 311. A role of the filter 600 is to remove a solid particle or the like in a target material that has been collected. The filter 600 can be configured as a porous filter made of a material such as alumina, silica, and silicon carbide. Alternatively, the filter 600 can also be made of a material such as molybdenum, titanium, tantalum, and a carbon fiber. Or more specifically, a material of a substrate of the filter 600 can be made of a sintered metal of a stainless steel or a fiber of a stainless steel, and the surface of the substrate can be coated with a metal nitride, a metal oxide, metal carbide, molybdenum, tungsten, or ceramics to configure the filter 600. Moreover, in the present embodiment, the surface of a filter housing that comes into contact with tin in a molted state and a material of the substrate of the filter housing are configured as described in the above embodiments. The periphery of the filter housing is covered by the heating unit 312 to be heated. Consequently, tin in the filter 600 can be prevented from being solidified. Moreover, in the present embodiment, the filter 600 is disposed along the path of the pipe 311 that is connected between the target regenerating device 184 and the target generating unit 120. However, the location of the filter 600 is not limited to this configuration example. In the case of the embodiment shown in FIG. 13, the filter 600 can also be disposed between the target material supply device 130 and the target generating unit 120. Moreover, in the cases of the embodiments shown in FIGS. 2, 8, 10, and 11, the filter 600 can also be disposed between the tank part 122 and the nozzle part 121. In the present embodiment, a part provided with a surface that comes into contact with tin in a molten state, such as the target generating unit 120, the target collecting device 180A, the target regenerating device 184, the pipe 311, the valve 310, and the target material supply device 130, is provided with an erosion resistance property to tin. As a method for providing an erosion resistance property to tin, as described in the above embodiments, there can be mentioned for instance a first method for forming one or a plurality of protective layers on the surface of the substrate part and a second method for forming the whole substrate part made of a material provided with an erosion resistance property, a pressure resistance property, and a heat resistance property. By the first method, an erosion resistance property can be achieved at a relatively low cost. However, for the first method, it is hard to form a protective layer on a narrow part or a slim location in some cases. In that case, the second method can be used. The present embodiment that is configured as described above has an operation effect equivalent to that of the first embodiment. Moreover, in the present embodiment, the unused target 203 is collected and regenerated for a recycle, whereby a target material can be utilized without an ineffective manner. While the preferred embodiments in accordance with the present invention have been described above, the present invention is not limited to the embodiments described above. Those skilled in the art can carry out various changes, modifications, and functional additions without departing from the scope of the present invention. Moreover, the embodiments described above can be properly combined with each other as needed. 1, 1A, 1B: EUV light source device 100: Vacuum chamber 101: First chamber 102: Second chamber 110: Driver laser light source 111: Light focusing lens 112: Incident window 120: Target generating unit 121, 121A, 121B, 121C: Nozzle parts 122, 122A, 122B: Tank parts 123: Gas inflow port 124: Heating device 125: Vibration generating unit 130: Target material supply device 140, 141: Magnetic field generating coils 150: EUV light collector mirror 152: Incident hole 160, 161: Bulkhead apertures 162: IF aperture 170: Gate valve 180, 180A: Target collecting devices 181: Opening board 182: Collection part 184: Target regenerating device 185: Dome 186: Suction pipe 187: Temperature sensor 188: Heating device 190: Vacuum pump 200: Target material 201: Target 202: Target plasma 203: Unused target 301, 501: Argon gas tanks 302, 304, 305, 306, 310, 503, 504: Valves 303: Exhaust pump 307, 502: Vacuum pumps 311: Pipe 312: Heating unit 400, 404: Substrate parts 401, 402, 401A, 402A, 403: Protective layers 600: Filter 1301: Target supply device body 1302: Supply pipe line

claims

1. A highly heat-resistant composite component for a fusion reactor, comprising:a plasma-facing area made of tungsten or a tungsten alloy with a tungsten concentration of >90% by weight, a heat-dissipating area of copper or a copper alloy with a thermal conductivity of >250 W/mK and a mean grain size of >100 μm, and an area in between said plasma-facing area and said heat-dissipating area of a refractory-metal-copper composite;said refractory-metal-copper composite having a macroscopically uniform copper and refractory metal concentration progression and a refractory metal concentration x of 60 vol. %<x<90 vol. % throughout a thickness d of 0.1 mm<d<4 mm, and a refractory metal phase forming a virtually continuous skeleton. 2. The component according to claim 1, which comprises a part of a metallic material having a strength of >300 MPa at room temperature bonded to said heat-dissipating area made of copper or the copper alloy. 3. The component according to claim 2, wherein said part consists of a Cu—Cr—Zr alloy. 4. The component according to claim 2, wherein said component consists of an austenitic steel. 5. The component according to claim 1, wherein said area between said plasma-facing area and said heat-dissipating area consists of a refractory-metal-copper composite produced with a powder-metallurgical process. 6. The component according to claim 5, wherein said refractory-metal-copper composite consists of tungsten and 10 to 40 vol. % copper. 7. The component according to claim 5, wherein said refractory metal-copper composite consists of molybdenum and 10 to 40 vol. % copper. 8. The component according to claim 1, wherein said plasma-facing area is a segmented structure of tungsten or a tungsten-alloy. 9. The component according to claim 1 in the form of a flat tile. 10. The component according to claim 1 in the form of a monoblock. 11. A method for producing a highly heat-resistant laminated composite flat tile component, which comprises:bonding one or more shaped parts of tungsten or tungsten alloy with one or more plate-shaped parts of a refractory metal-copper-composite and the plate-shaped parts with an area made of copper alloy in vacuum or a non-oxidative gas atmosphere by melting the copper-containing constituents and subsequently cooling to room temperature;joining the shaped parts to an area made of copper or a copper alloy by melting the copper-containing constituents and subsequently cooling to room temperature;mechanically processing the resulting component; andsubsequently bonding the mechanically processed component in a form-fit with a metal component having a strength of >300 MPa in a bonding process selected from the group consisting of welding, soldering, brazing, diffusion, and a plating process to thereby produce the highly heat-resistant composite component according to claim 1. 12. The method according to claim 11, which comprises bonding the shaped parts, plate-shaped parts, and the area of copper alloy in a temperature-resistant and corrosion-resistant form. 13. The method according to claim 12, wherein the temperature-resistant and corrosion-resistant form is a graphite form. 14. The method according to claim 11, which comprises introducing a foil of copper or copper alloy with a thickness of 0.005 to 0.5 mm between the shaped part of tungsten or tungsten alloy and the plate-shaped part of the refractory-metal-copper composite. 15. The method according to claim 14, which comprises applying a layer consisting of a ferrous metal in elemental or alloyed form to a bonding surface of one of the shaped part of tungsten or tungsten alloy, the plate-shaped part of the refractory-metal-copper composite, and the foil of copper or copper alloy. 16. The method according to claim 15, wherein the ferrous metal is nickel. 17. The method according to claim 11, which comprises applying a layer consisting of a ferrous metal in elemental or alloyed form to a bonding surface of one of the shaped part of tungsten or tungsten alloy and the plate-shaped part of the refractory-metal-copper composite. 18. The method according to claim 17, wherein the ferrous metal is nickel. 19. A method for producing a highly heat-resistant monoblock component, which comprises:bonding one or more shaped parts of tungsten or a tungsten alloy and formed with bores to one or more ring-shaped parts of a refractory metal copper-composite and the ring-shaped parts to an area consisting of copper alloy in a vacuum or inert gas atmosphere by melting the copper-containing constituents and subsequently cooling to room temperature;bonding to an area consisting of copper or a copper alloy by melting the copper-containing constituents and subsequently cooling to room temperature;mechanically processing the resulting component;subsequently bonding the mechanically processed component in a form-fit with a metal component having a strength of >300 MPa in a bonding process selected from the group consisting of welding, soldering, brazing, diffusion, and a plating process to thereby produce the highly heat-resistant composite component according to claim 1. 20. The method according to claim 19, which comprises bonding the shaped parts and plate-shaped parts in a temperature-resistant and corrosion-resistant form. 21. The method according to claim 20, wherein the temperature-resistant and corrosion-resistant form is a graphite form. 22. The method according to claim 19, which comprises introducing a foil of copper or copper alloy with a thickness of 0.005 to 0.5 mm between the shaped part of tungsten or tungsten alloy and the ring-shaped part of the refractory-metal-copper composite. 23. The method according to claim 22, which comprises applying a layer consisting of a ferrous metal in elemental or alloyed form to a bonding surface of one of the shaped part of tungsten or tungsten alloy, the ring-shaped part of the refractory-metal-copper composite, and the foil of copper or copper alloy. 24. The method according to claim 23, wherein the ferrous metal is nickel. 25. The method according to claim 19, which comprises applying a layer consisting of a ferrous metal in elemental or alloyed form to a bonding surface of one of the shaped part of tungsten or tungsten alloy and the ring-shaped part of the refractory-metal-copper composite. 26. The method according to claim 25, wherein the ferrous metal is nickel.

046474250

claims

1. A method for vacuum degassing a pressurized water reactor coolant system (RCS) having reactor coolant containing radiogas and nonradiogas and a reactor pressure vessel connected to at least one steam generator by a hot leg, comprising: draining down the RCS to approximately the midpoint of said hot leg; maintaining the RCS in an unvented condition during said step of draining down; refluxing any flashed reactor coolant in a primary side of said at least one steam generator; circulating the reactor coolant through a heat removal system; drawing a vacuum on said RCS to evacuate at least some of said radiogas and nonradiogas therefrom. draining down the RCS to approximately the midpoint of said hot leg; maintaining the RCS in an unvented condition during said step of draining down; circulating the reactor coolant through a heat removal system; drawing a vacuum on said RCS to evacuate at least some of said radiogas and nonradiogas therefrom. draining down the RCS to approximately the midpoint of said hot leg; drawing a vacuum on said RCS; refluxing any flashed reactor coolant in a primary side of said at least one steam generator; circulating the reactor coolant through a heat removal system; maintaining a vacuum on said RCS to evacuate at least some of said radiogas and nonradiogas therefrom. 2. The vacuum degassing method of claim 1, wherein said step of draining further comprises using a two-phase pump to establish a partial vacuum in said unvented RCS during draindown, said partial vacuum being sufficient to cause said reactor coolant to boil at prevailing temperatures in said RCS whereby degassing occurs during said draindown step. 3. The vacuum degassing method of claim 1, wherein said step of refluxing further comprises flowing secondary coolant through a secondary side of said at least one steam generator whereby any flashed reactor coolant in said primary side is condensed back into liquid and any non-condensible gases are stripped away. 4. The vacuum degassing method of claim 2, wherein said step of refluxing further comprises flowing secondary coolant through a secondary side of said at least one steam generator whereby any flashed reactor coolant in said primary side is condensed back into liquid and any non-condensible gases are stripped away. 5. The vacuum degassing method of claim 2, wherein said heat removal system is a residual heat removal system. 6. The vacuum degassing method of claim 5, wherein the step of drawing a vacuum is performed after the of draining down and after the heat removal system is operating. 7. The vacuum degassing method of claim 6, wherein the step of drawing a vacuum is performed using a waste gas removal system. 8. The vacuum degassing method of claim 6 further including the step of sampling the circulating reactor coolant in the heat removal system and continuing said drawing step until a predetermined level of gas concentration is detected during said sampling. 9. The vacuum degassing of claim 8 further including the steps of stopping said drawing step after detecting said predetermined level of gas concentration and then breaking said vacuum. 10. The vacuum degassing method of claim 9, wherein the step of breaking said vacuum comprises admitting air to the circulating reactor coolant. 11. The vacuum degassing method of claim 10 further including the step of purifying the circulating reactor coolant in a purification system. 12. The vacuum degassing method of claim 11, wherein the reactor coolant is purified in a mixed bed demineralizer. 13. The vacuum degassing method of claim 11, wherein the step of refluxing is stopped when the vacuum is broken. 14. The vacuum degassing method of claim 13, wherein the step of circulating further comprising increasing the circulation of reactor coolant through the residual heat removal system when the step of refluxing is stopped. 15. The vacuum degassing method of claim 9 further including the step of flooding the reactor after the step of breaking the vacuum. 16. The vacuum degassing method of claim 11 further including the step of flooding the reactor pressure vessel after the step of breaking the vacuum. 17. The vacuum degassing method of claim 16 further including the step of refilling the RCS under vacuum. 18. A method for vacuum degassing a pressurized water reactor coolant system (RCS) having reactor coolant containing radiogas and nonradiogas and a reactor pressure vessel connected to at least one steam generator by a hot leg, comprising: 19. The vacuum degassing method of claim 18, wherein said step of draining further comprises using a two-phase pump to establish a partial vacuum in said unvented RCS during draindown, said partial vacuum being sufficient to cause said reactor coolant to boil at prevailing temperatures in said RCS whereby degassing occurs during said draindown step. 20. The vacuum degassing method of claim 19, wherein said heat removal system is a residual heat removal system. 21. A method for vacuum degassing a pressurized water reactor coolant system (RCS) having reactor coolant containing radiogas and nonradiogas and a reactor pressure vessel connected to at least one steam generator by a hot leg, comprising: 22. The vacuum degassing method of claim 21, wherein said step of refluxing further comprises flowing secondary coolant through a secondary side of said at least one steam generator whereby any flashed reactor coolant in said primary side is condensed back into liquid and any non-condensible gases are stripped away. 23. The vacuum degassing method of claim 21, wherein said heat removal system is a residual heat removal system. 24. The vacuum degassing method of claim 23, wherein the step of maintaining a vacuum is performed after the draindown system and after the heat removal step is operating. 25. The vacuum degassing method of claim 24, wherein the step of maintaining a vacuum is performed using a waste gas removal system. 26. The vacuum degassing method of claim 24 further including the step of sampling the circulating reactor coolant in the heat removal system and continuing said maintaining a vacuum step until a predetermined level of gas concentration is detected during said sampling. 27. The vacuum degassing method of claim 26 further including the steps of stopping said maintaining a vacuum after detecting said step of predetermined level of gas concentration and then breaking said vacuum. 28. The vacuum degassing method of claim 27, wherein the step of breaking said vacuum comprises admitting air to the circulating reactor coolant. 29. The vacuum degassing method of claim 27 further including the step of flooding the reactor pressure vessel. 30. The vacuum degassing method of claim 29 further including the step of refilling the RCS under vacuum.

044316038

abstract

A self-actuated device, of particular use as a valve or an orifice for nuclear reactor fuel and blanket assemblies, in which a gas produced by a neutron induced nuclear reaction gradually accumulates as a function of neutron fluence. The gas pressure increase occasioned by such accumulation of gas is used to actuate the device.

abstract

In one embodiment, a system and method for dry storage comprises removing spent fuel rods from their fuel rod assemblies and placing the freed fuel rods in a storage cell of a dry storage canister with a high packing density and without a neutron absorber material present.

047114363

summary

CROSS-REFERENCE TO COPENDING APPLICATIONS Attention is drawn to the following copending, commonly assigned applications, all/each filed on even date and incorporated specifically by reference into the instant specification: (1) "FUEL GRID WITH SLEEVES WELDED IN NOTCHED GRID STRAPS", by R. Duncan, Ser. No. 414,232; now U.S. Pat. No. 4,521,374. (2) "PULSED LASER MACHINING APPARATUS", by R. A. Miller and G. D. Bucher, Ser. No. 414,264; now U.S. Pat. No. 4,560,856. (3) "APPARATUS AND METHOD FOR LASER MACHINING IN NON-REACTIVE ENVIRONMENT", by R. A. Miller and G. G. Lessman, Ser. No. 414,242; now U.S. Pat. No. 4,492,843. (4) "STRAP AND VANE POSITIONING FIXTURE FOR FUEL ROD GRID AND METHOD", by R. F. Antol, R. W. Kalkbrenner and R. M. Kobuck, Ser. No. 414,197; now U.S. Pat. No. 4,539,738. (5) "LASER MACHINING SYSTEM", by D. L. Wolfe, J. W. Clements and J. S. Kerrey, Ser. No. 414,241; now U.S. Pat. No. 4,541,055. (6) "MOVABLE MACHINING CHAMBER WITH ROTATABLE WORK PIECE FIXTURE", by R. F. Antol, R. Kalkbrenner and D. L. Wolfe, Ser. No. 414,263; now U.S. Pat. No. 4,501,949. (7) "WORKPIECE GRIPPING AND MANIPULATING APPARATUS FOR LASER WELDING SYSTEMS AND THE LIKE", by R. Kalkbrenner and R. Kobuck, Ser. No. 414,262; now U.S. Pat. No. 4,538,956. (8) "LASER LENS AND LIGHT ASSEMBLY", by R. Antol, R. Kalkbrenner and R. Kobuck, Ser. No. 414,205; now U.S. Pat. No. 4,518,843. (9) "WELDING PLATES FOR A FUEL ROD GRID", by R. M. Kobuck, R. Miller, R. W. Kalkbrenner, J. Kerrey and R. Duncan, Ser. No. 414,265; now U.S. Pat. No. 4,492,844. (10) "PLURAL COMPUTER CONTROL FOR SHARED LASER MACHINING", by J. W. Clements and W. D. Lanyi, Ser. No. 414,204; now U.S. Pat. No. 4,547,855. (11) "GRID AND SLEEVES WELDING FIXTURE AND METHOD", by J. S. Kerrey and R. Duncan, Ser. No. 414,203; now U.S. Pat. No. 4,522,330. (12) "CALIBRATION OF AUTOMATED LASER MACHINING APPARATUS" by J. W. Clements and J. R. Faulkner, Ser. No. 414,272; and now U.S. Pat. No. 4,545,018. (13) "RIGID SUPPORT FOR LASER MACHINING APPARATUS", by D. L. Wolfe, Ser. No, 414,191, now U.S. Pat. No. 4,493,967. BACKGROUND OF THE INVENTION Description of the Prior Art This invention, in its preferred form, relates to apparatus and a related method for assembling inner grid straps so as to form a grid of generally square configuration, and for providing outer grid straps on the grid formed from the inner grid straps. More particularly, the invention relates to (a) a grid assembly fixture for holding a first set of inner grid straps in parallel relationship, and for holding a second set of grid straps parallel to each other and perpendicular to the straps of the first set, and for holding outer grid straps, (b) to a retention strap for retaining the grid formed of the inner and outer grid straps in assembled relationship, and (c) to a method of assembling a grid from grid straps using the grid assembly fixture and retention strap. Nuclear fuel bundle assemblies include a matrix of nuclear fuel rods which are arrayed in rows and columns, and which are held in the desired configuration by a plurality of fuel rod grids. These grids are produced from "straps" which are linearly extending, generally rectangular elements, characterized by having slots extending from one edge approximately half way through the depth of the strap. The straps are assembled so that one strap is in mating relationship with the other strap. Thus, the slot of one strap engages the other strap at a portion thereof which is in alignment with the slot of that other strap, with the result that the grid is of the same depth as each of the straps which forms the grid. The resulting grid has a first set of straps which are substantially parallel to each other, and equally spaced, and a second set of straps which are parallel to each other and equally spaced, the straps of one set being perpendicular to the straps of the other set. All of the aforesaid straps are designated as "inner straps", and they are placed in mating relationship to form a square grid of square cells, in the above noted rows and columns. In addition, there are provided outer straps, which are placed on the four sides of the grid. The inner straps and outer straps were formerly assembled by first joining together two straps in mating relationship on a conventional table or plate. Typically, two additional straps were added, so that there resulted the four outer-most inner straps, which thereby formed a frame. The remaining inner straps were then placed in position, utilizing the frame provided by these first four placed straps. Then the outer straps where placed in position, and an encircling strap or holding strap was placed about the entire assembled grid. Further processing was then effected by placing brazing material at various locations on the grid, and the grid with the brazing material placed on it was then positioned in an oven, where brazing was effected. The above-described method and related apparatus resulted in a very time consuming operation. SUMMARY OF THE INVENTION It is therefore an object of this invention to provide equipment which will permit the rapid assembly of inner and outer grid straps into a grid. It is the most specific object of this invention to provide equipment, and attendant method, to permit assembly of inner and outer grid straps which will avoid excessive bending thereof. It is a still further object of the present invention to provide grid assembly equipment and method which will permit ready assembly of inner and outer grid straps without undue binding thereof, and which will provide for retention of the assembled grid for welding by a laser beam welding. It is yet another object of the present invention to provide a retention strap for an assembled fuel rod grid which will provide access for welding by a laser beam to all weld locations on the exterior of the grid. In accordance with these and other objects of the invention, there is disclosed a grid assembly fixture comprised of a generally flat plate of square plan form, having in a surface thereof a first set of equally spaced, parallel grooves and a second set of equally spaced, parallel grooves, the grooves of the two sets being perpendicular to each other. Preferably, the grid assembly fixture has a peripherally extending raised portion. In addition, bores are provided at the intersections of each two grooves, with smaller bores provided along one groove, adjacent an edge of the plate, so as to serve as locating holes. The plate is mounted on a support for rotation on both vertical and horizontal axes, and in an attendant method, there are positioned on the plate the straps of a first set, then the plate is rotated, and there are placed, in mating relationship with the straps of the first set, the straps of the second set. Thereafter, outer straps are provided, being supported on the plate, the outer straps having slots, and the inner straps having at their ends extending tabs, at least some of the tabs of the inner straps being caused to enter into the mating slots of the outer straps. The plate and grid are then tilted so that two of the outer straps face upwardly, and two bars of a retention strap, to be hereinbelow described, are placed on the two outer straps, and are held in position by clamps. The plate is then rotated, so that the other two outer straps face upwardly, and two additional bars of a retention strap are placed on these latter two outer straps, and are joined to the first two bars of the retention strap, thereby forming a complete retention strap encircling and engaging the outer straps forming the grid, after which the assembly of retention strap and grid may be removed from the the grid assembly plate. The retention strap is formed of four H-shaped bars having two end posts and a cross member between them. A first two and a second two of the bars are hingedly connected together by a hinge structure which causes the adjacent ends of the bars to be spaced from each other. There are thereby formed two pairs of hinged bars. Further, the bars are provided with releasable fastening elements, so that the two pairs of bars may be joined together to form a retention strap of four bars. The releasable fasteners are constructed so that the adjacent ends of two adjacent bars are in spaced relation. By this construction, a laser beam may pass in the space between adjacent ends of bars at all four corners of the grid, to permit corner welding of the grid, and in addition, the slot and tab welding may be effected since the cross member of the bars are located between upper and lower tab and slot connections of the inner and outer grid straps.