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claims
1. A fuel assembly charged in a reactor core of a nuclear reactor using a liquid metal as a coolant, the fuel assembly comprising:a vertically disposed wrapper tube including an entrance nozzle at a lower end that introduces the coolant and an operation handling head at an upper end, the wrapper tube stores a plurality of fuel pins;grids that support the plurality of fuel pins in the wrapper tube in a radial direction of the wrapper tube; andperipheral flow suppressing members, formed by a plurality of blocks, each block being a unitary structure extending around all fuel pins disposed on the periphery and controlling a flow of the coolant, the peripheral flow suppressing members being disposed in a peripheral flow passage between fuel pins disposed on the periphery of the fuel assembly and the wrapper tube, and extending over a length corresponding to a heat generation length, wherein the heat generation length corresponds to a length in the axial direction of the fuel pins storing a radioactive fuel material, and the blocks having an inner circumferential surface formed as a plurality of convexities, each of the convexities having a same focus and a larger radius as the respective fuel pin disposed on the periphery of the fuel assembly,wherein the radii of the convexities is determined such that a lateral cross sectional area of a first flow passage is substantially equal to a lateral cross sectional area of a second flow passage, the first flow passage being a flow passage disposed outside of a boundary line formed by a line drawn through the foci of the fuel pins disposed on the periphery of the fuel assembly, the lateral cross sectional area of the first flow passage being an area located outside of the boundary line and between outer circumferential portions of each of the fuel pins disposed on the periphery of the fuel assembly and the convexities formed on the inner circumferential surface of the blocks, and the lateral cross sectional area of the second flow passage being determined as an area located inside the boundary line and not occupied by the fuel pins. 2. The fuel assembly according to claim 1, wherein each of the blocks is disposed in the peripheral flow passage to reduce the lateral cross sectional area of the first flow passage. 3. The fuel assembly according to claim 2, wherein the blocks are stacked along an axial direction of the grids, and groups of the stacked blocks keep relative positions in the axial direction of the grids. 4. The fuel assembly according to claim 2, wherein the blocks are disposed in a ring shape at an inner circumferential surface of the wrapper tube and a coolant circulation hole is formed through each of the blocks to form a coolant flow passage that passes from the inner circumferential surface of the block to an outer circumferential side of the block. 5. The fuel assembly according to claim 1, further comprising sleeves disposed to cover the outer circumferential portions of each of the fuel pins disposed on the periphery of the fuel assembly within a range of a gas plenum of each fuel pin and to keep relative positions between the grids. 6. The fuel assembly according to claim 5, wherein a lower portion of the operation handling head is provided with a spring for pressing down one of the sleeves, a downward pressing force of the spring presses and holds the grids and the peripheral flow suppressing members from an upper side via the sleeve with an elastic force.
abstract
Methods and apparatus are disclosed for forming a sample of an object, extracting the sample from the object, and subjecting this sample to microanalysis including surface analysis and electron transparency analysis in a vacuum chamber. In some embodiments, a method is provided for imaging an object cross section surface of an extracted sample. Optionally, the sample is iteratively thinned and imaged within the vacuum chamber. In some embodiments, the sample is situated on a sample support including an optional aperture. Optionally, the sample is situated on a surface of the sample support such that the object cross section surface is substantially parallel to the surface of the sample support. Once mounted on the sample support, the sample is either subjected to microanalysis in the vacuum chamber, or loaded onto a loading station. In some embodiments, the sample is imaged with an electron beam substantially normally incident to the object cross section surface.
046684654
summary
BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is directed to a method and apparatus for remotely monitoring with high reliability a process carried out in a hazardous environment within a containment structure. More particularly, it is directed to a method and apparatus for transmitting redundant signals from a large number of detectors through the containment structure with a minimum number of penetrations. It is particularly applicable to transmitting to the plant control room outside of the containment building reliable indications of control rod position in a nuclear reactor. 2. Prior Art There are many installations wherein the hazardous conditions under which a process is carried out require that it be enclosed in a containment structure. Under such conditions, it is desirable to be able to remotely monitor and control the process and to be able to do so with a great deal of reliability to preclude having to shutdown for lack of sufficient control, and with a minimum of pentrations through the containment structure to reduce construction costs. The latter requirement becomes particularly important in installations in which a large amount of information must be transmitted through the containment structure. Radiation and toxic chemicals are exemplary hazardous conditions which require confinement within a containment structure to protect those working with them. A nuclear reactor is an example of an installation in which hundreds of detectors and control signals of various kinds must be transmitted through the containment structure for monitoring, protection, and control functions directed from outside. Remotely monitoring the position of the control rods within the core of the nuclear reactor is a procedure which requires the transmission of a great deal of information through the containment structure. In a typical pressurized water reactor, there are several scores of drive rods which each incrementally step several neutron absorbing rods connected by a spider into and out of the reactor core. The positions of the neutron absorbing rods within the reactor core are derived from the positions of the associated drive rods; each of which is equipped with a position detector. Early rod position detectors used the change in impedance of a coil or the change in coupling between primary and secondary coils effected by the end of the drive rod as it moved through the coil to generate an analog signal indicative of rod position. The susceptability of such analog systems to variations in temperature, rod magnetization, permeability of the rod, power supply voltages and frequency, and to interference from adjacent control rods and drive mechanisms, led to the development of digital position indicating systems such as that disclosed in U.S. Pat. No. 3,846,771. This system uses a number of discrete coils spaced along the linear path traced by the end of the rod. The change in impedance of each coil in sequence as the rod advances through successive coils is used to generate discrete output signals or one output signal with discrete levels. Discrete output signals are preferred over a single signal with discrete levels because they can be more easily transmitted to remote locations and reliably decoded. Their use, however, significantly multiplies the number of signals that must be transmitted. Reliability is of critical importance in monitoring the position of control rods in the core of a nuclear reactor. It is well-known that reliability can be enhanced through redundancy. In the digital rod position indicating systems disclosed in U.S. Pat. Nos. 3,858,191 and 3,893,090, redundant sets of coils are interleaved along the path of each drive rod and the signals generated as the end of the rod passes through the coils in each set are separately transmitted through the containment building wall through separate channels to the outside where they are combined to provide an indication of rod position. All of the data generated by one set of coils in each detector is transmitted over one channel and that generated by the second set of coils in each detector is transmitted over another channel. If either channel is inoperative, the remaining channel provides the position indication for all of the rods with half the resolution of the combined indication. While such systems provide protection against a single component failure, they are highly susceptible to certain dual component failures. For instance, if one transmission channel should fail, the signals from one entire set of coils for each detector are not available. A subsequent failure in the other set of coils for any detector results in a loss of all reliable information regarding the position of the neutron absorbing rods connected to the associated drive rod. It is a primary object of the present invention to provide the capability for remotely monitoring a process carried out in a hazardous environment within a containment structure with high reliability and with a large amount of digital information transmitted using a limited number of penetrations through the containment structure. SUMMARY OF THE INVENTION This and other objects are realized by generating within the containment structure a plurality of redundant sets of detector signals representative of the value of selected process parameters, storing all of these signals within the containment structure in each of a plurality of microprocessors, serially transmitting the plurality of sets of redundant detector signals stored in each microprocessor to the outside of the containment structure over a separate serial data link, and generating separately outside the containment structure, redundant representations of the value of each of the selected parameters, each from the redundant sets of signals transmitted over one of the data links. The data link from which the redundant sets of signals used to generate each redundant representation are taken is selectable. In addition, the signal used to generate the representation is selectable as to each parameter from among the redundant signals received over the selected data link. The apparatus used to carry out the invention includes means within the containment structure for generating a plurality of redundant sets of detector signals. Interface means applies all of the redundant signals to each of a plurality of communication buses equal in number to the number of redundant sets of signals. A plurality of bus controller/serial output devices located in the containment structure are each connected to one of the communications buses, to control the interface means in applying the redundant sets of detector signals to the associated communications bus, to store these signals, and to serially output them over its own data link extending through the containment structure to the outside. Redundant receiver devices on the outside of the containment structure generate from the redundant sets of detector signals received from one of the data links, a representation of the value of the detector signal. Switching means permit selection of the data link from which each receiver receives its redundant sets of detector signals and permits individual selection as to each detector of which of the redundant signal is to be used in generating the representation of the value of that detector signal. As applied to monitoring the position of the control rods in a nuclear reactor, the detector signals are generated as multi-digit digital signals from the signals generated by the discrete coils spaced along the travel path of the rod. The redundant signals can be generated simply by reproducing the coil signals, since these components have been proven to be very dependable. Alternatively, interleaved redundant sets of coils can be used to produce the redundant detector signals. The essence of the invention is that all of the redundant signals are all transmitted over all of the redundant transmission channels with each of the receivers being able to select the individual channel from which it receives the redundant signals. With such an arrangement, failure of the same component in each of the detector to display channels is required to cause a loss of any of the transmitted information thus providing increased reliability over the earlier systems in which the redundant signals were transmitted separately over independent transmission channels .
claims
1. A method of using an atomic force microscope by means of amplitude modulation, the method comprising the steps of:exciting at least one natural lower vibration mode and one natural higher vibration mode of a microlever of said atomic force microscope,analysing at least one of a variation of one variable of a first output signal that is representative of a response of said microlever to said excitation of said lower vibration mode, with respect to a variation of at least one parameter which is influenced by one variable of a second output signal that is representative of a response of said microlever to said excitation of said higher vibration mode, anda variation of one variable of the second output signal that is representative of a response of said microlever to said excitation of said higher vibration mode, with respect to a variation of at least one parameter which is influenced by one variable of a first output signal that is representative of a response of said microlever to said excitation of said lower vibration mode. 2. The method of claim 1, wherein at least one of said at least one parameters is equivalent to said one variable by which it is influenced. 3. The method of claim 1, wherein at least one of said at least one parameters is influenced, in a weighted manner, by at least two variables of, respectively,the first and the second output signals that are representative of the response of said microlever to, respectively, said excitation of said lower vibration mode and of said higher vibration mode. 4. The method of claim 1, wherein the variable of said first output signal and said variable of said second output signal are each relative to at least one of an oscillation amplitude, a phase, and a resonance frequency of the respective first and second output signals. 5. The method of claim 4, wherein said influencing variable or variables of at least one of said parameters are relative to the oscillation amplitude. 6. The method of claim 4, wherein the analysis step comprises using:a phase as the variable of said first output signal and an amplitude as the variable of said second output signal;oran amplitude as the variable of said first output signal and an resonance frequency as the variable of said second output signal;orthe phase as the variable of said first output signal and the resonance frequency as the variable of said second output signal;orthe amplitude as the variable of both output signals,orthe phase as the variable of both output signals,orthe resonance frequency as the variable of both output signals. 7. The method of claim 1, wherein said lower vibration mode is a first natural vibration mode of the microlever. 8. The method of claim 1, wherein said higher vibration mode is a second natural vibration mode of the microlever. 9. The method of claim 1, further comprising the step of exciting at least another higher vibration mode of the microlever, and wherein, said analysis steps further include at least one variable of an output signal obtained by said excitation of said other higher vibration mode. 10. The method of claim 1, wherein it comprises performing said excitation of at least said two modes externally. 11. The method of claim 10, wherein said external excitation is at least one excitation from the group that includes mechanical, thermal, electrostatic, and a combination thereof. 12. The method of claim 1, further comprising the steps of performing an excitation of one of said modes externally, andperforming the excitation of the other mode by one of self-excitation, harmonics, and sub-harmonics of the external excitation. 13. The method of claim 1, further comprising the step of performing said analysis or analyses to obtain at least one of topographic and compositional information about said sample. 14. The method of claim 13, wherein further comprising the steps of changing said sample to be examined by at least one second sample, andperforming, with said second sample, the same steps that were performed with the first sample. 15. The method of claim 14, wherein further comprising the steps of: recording and classifying the data obtained for a plurality of different samples. 16. The method of claim 15, further comprising the steps of:comparing the data obtained for an analysis of the sample located under said microlever to said recorded data, andestablishing, based on the comparison, a degree of similarity with at least one sample of said plurality of samples. 17. The method of claim 1, wherein further comprising the step of performing at least one cross-representation of the data obtained as a result of said analysis step, for two or more variables of, respectively, two or more output signals that are representative of the response of said microlever to the corresponding excitations of said natural vibration modes. 18. The method of claim 17, wherein said cross-representation is a visual representation, in the form of a graph or a table. 19. The method of claim 1, further comprising the step of performing at least two of said excitations of said natural vibration modes of the microlever simultaneously. 20. The method of claim 19, wherein performing said excitations, using a compound excitation signal composed of the sum of said two excitation signals. 21. The method of claim 20, wherein further comprising the steps of:breaking down a compound output signal that is representative of the response of said microlever to said excitation using said compound excitation signal;separating the compound output signal into parts that correspond to the response to each of said excitations, which are at least two, andsubsequently using the variables thereof to perform at least the above-mentioned analyses.
049816160
claims
1. In a method for recovering plutonium and uranium from spent nuclear fuel scrap comprising dissolving the scrap in nitric acid to form a solution containing plutonium nitrate and uranyl nitrate, separating the nitrates from said solution and converting the nitrates to plutonium and uranyl oxides, the improvement comprises extracting the nitric acid containing the plutonium nitrate and the uranyl nitrate with a solvent consisting of tri-n-butyl phosphate, dibutyl phosphate and n-dodecane, subsequently removing said nitrates from said solvent, freeze-drying said solvent to separate the n-dodecane from the phosphates and separating the phosphates from each other and residual impurities by fractional distillation.
summary
043893686
abstract
An improved pressurized fluid reactor system having a fluid cooled reactor core in which the coolant pump for delivering fluid to the reactor core is driven by a pump motor through a unidirectional drive means which enables the pump to operate at a greater speed than the pump motor in the pumping direction only. A preferred unidirectional drive means in the form of a ratchet means is disclosed.
claims
1. A mechanical bucket for separating small material from larger material, the mechanical bucket comprising:a bucket adapted to receive and retain material within the bucket;a roller screen assembly removably secured to a bottom portion of the bucket, wherein material received within the bucket rests on the roller screen assembly when deactivated, the roller screen assembly adapted to separate smaller material from larger material of the material received within the bucket when activated, the smaller material passing through the screen and the larger material remaining in the bucket; anda scraper device coupled to the bucket adjacent to a bottom side of the roller screen assembly, wherein the scraper removes debris from the roller screen assembly. 2. The mechanical bucket of claim 1, wherein the scraper device includes a base portion and a plurality of extensions that extend in a direction transverse to the base portion, the extensions engaging the roller screen to scrape debris from the roller screen. 3. The mechanical bucket of claim 1, wherein the roller screen assembly is adapted to agitate the material within the bucket when the roller screen assembly is activated. 4. The mechanical bucket of claim 3, wherein the roller screen assembly is driven to its operating speed at a predetermined rate when activated. 5. The mechanical bucket of claim 4, wherein the roller screen assembly is driven to a stop from operating speed at a predetermined rate when deactivated. 6. The mechanical bucket of claim 5, wherein the roller assembly when activated operates at a variable rotational speed. 7. The mechanical bucket of claim 1, further comprising a sub-base, the sub-base removably coupled to the bottom portion of the bucket, the sub-base adapted to removably secure the roller screen assembly to the bucket. 8. A material separator comprising:a mechanical bucket defining an inner volume, the mechanical bucket adapted to couple to a vehicle, the mechanical bucket movable between a first location and a second location by use of the vehicle;a roller screen assembly removably secured to a bottom portion of the mechanical bucket, wherein material received within the bucket rests on the roller screen assembly when deactivated, the roller screen assembly adapted to separate smaller material from larger material of the material received within the bucket when activated, the smaller material being passed through the roller screen assembly and deposited at the first location and the larger material remaining in the bucket;a scraper device coupled to the bucket adjacent to a bottom side of the roller screen assembly, wherein the scraper removes debris from the roller screen assembly; anda sub-base removably coupled to the bottom portion of the mechanical bucket, the sub-base adapted to removably secure the roller screen assembly to the bucket. 9. The mechanical separator of claim 8, wherein the roller screen assembly is adapted to agitate the material within the bucket when the roller screen assembly is activated. 10. The material separator of claim 8, further comprising a motor mechanically engaged with the roller screen assembly. 11. The material separator of claim 10, wherein motor is driven to its operating speed at a predetermined rate upon activation. 12. The material separator of claim 11, wherein the motor is driven to a stop from its operating speed at a predetermined rate upon deactivation. 13. The material separator of claim 12, wherein the motor operates the roller screen assembly at a variable rotational speed. 14. The material separator of claim 8, wherein the mechanical bucket is adapted to rotate for dumping the larger material at the second location. 15. A method of using a mechanical bucket for separating smaller material from larger material, the method comprising:receiving material within a mechanical bucket, the material including smaller material and larger material;moving the mechanical bucket to a location for depositing the smaller material;activating a roller screen assembly of the mechanical bucket to separate the smaller material from the larger material;removing debris from the roller screen assembly with a scraper; anddepositing the smaller material at the location, wherein the smaller material during separation passes through the roller screen assembly and is deposited at the location. 16. The method of claim 14, further comprising agitating the material to facilitate separation of the smaller material from the larger material. 17. The method of claim 14, further comprising retaining the larger material within the mechanical bucket. 18. The method of claim 14, further comprising deactivating the roller screen assembly when separation of the smaller material from the larger material is completed. 19. The method of claim 14, further comprising:moving the mechanical bucket to a second location; anddumping the larger material in the second location by rotating the bucket.
046831150
claims
1. Nuclear reactor fuel assembly having a grid-shaped spacer with square grid meshes, wherein mutually parallel rods are arranged, respectively, in a grid mesh, the spacer having flat outer straps extending transversely to the rods and an intermediate strip extending parallel to the rods between two of the respective outer straps, the intermediate strip being inclined relative to the two outer straps, comprising a rejection rise formed at the outside of the intermediate strip and extending outwardly and away from the grid meshes in direction of a diagonal of a grid mesh located at a corner betwen the two outer straps, said rejection rise being disposed transversely to the two outer straps and being inclined downwardly towards two respective ends of the intermediate strip in longitudinal direction of the rods. 2. Nuclear reactor fuel assembly according to claim 1 wherein said rejection rise is located on a spring strip suspended from the ends of the intermediate strip. 3. Nuclear reactor fuel assembly according to claim 1 wherein said rejection rise in located on a fishplate on one of the outer straps, said fishplate forming the intermediate strip and being secured at an inner side thereof to the other outer strip. 4. Nuclear reactor fuel assembly according to claim 1 wherein the two outer straps are inclined at respective corners starting from edges thereof and extending towards the intermediate strip, and form chamfers of like inclination. 5. Nuclear reactor fuel assembly according to claim 4, including a rectilinear inclination continued from the respective outer straps into the intermediate strip and forming a pointed cutout at the ends of the intermediate strip. 6. Nuclear reactor fuel assembly according to claim 3 wherein said rejection rise is formed by a tab cut out of said fishplate on the one outer strap and is disposed in the plane of this one outer strap, said tab being formed at lateral edges thereof with respective pointed cutouts, the points of said cutouts being located on a bending edge extending parallel to the rods, said tab being bent perpendicularly at said bending edge into a plane wherein the other outer strap is disposed, said tab being secured to the outside of the other outer strap.
summary
claims
1. A laser scanning microscope, which enables observation of a specimen, which is marked by a plurality of fluorescent probes, by emitting a laser beam onto the specimen and receiving fluorescent light, corresponding to the emission of the laser beam, back from the specimen, the laser scanning microscope comprising:at least one laser source for generating the laser beam in at least one excitation wavelength corresponding to the plurality of fluorescent probes;deflector means for scanning the generated laser beam over an observation plane of the specimen;dispersion means for dispersing the fluorescent light from the specimen to extract the dispersed fluorescent light by an arbitrary wavelength section;spectral data acquisition condition setting means for setting a spectral data acquisition condition for the dispersion means for acquiring spectral data based on spectrum characteristics of the plurality of fluorescent probes;dispersion control means for controlling the dispersion means based on the set spectral data acquisition condition; andphotoelectric conversion means for receiving the extracted fluorescent light and converting the received light into an electrical signal;wherein the dispersion means comprises a diffraction mirror for dispersing the fluorescent light from the specimen and selecting a wavelength of the fluorescent light, and a slit which selects the arbitrary wavelength section of the dispersed fluorescent light to be received by the photoelectric conversion means in accordance with the selected wavelength; andwherein the spectral data acquisition condition setting means sets a wavelength incrementing amount corresponding to a rotation angle of the diffraction mirror and a spectral resolution corresponding to a width of the slit, which are applicable to carrying out a wavelength scanning for the specimen based on the spectrum characteristics of the plurality of fluorescent probes. 2. A laser scanning microscope, which enables observation of a specimen, which is marked by a plurality of fluorescent probes, by emitting a laser beam onto the specimen and receiving fluorescent light, corresponding to the emission of the laser beam, back from the specimen, the laser scanning microscope comprising:at least one laser source which generates the laser beam in at least one excitation wavelength corresponding to the plurality of fluorescent probes;a laser beam scanner which scans the generated laser beam over an observation plane of the specimen;a dispersion unit which disperses the fluorescent light from the specimen to extract the fluorescent light by an arbitrary wavelength section;a spectrum characteristic data storage unit which stores spectrum characteristics of the plurality of fluorescent probes;a spectral data acquisition condition setting unit which sets a spectral data acquisition condition for the dispersion unit to extract a prescribed wavelength interval from the fluorescent light based on the spectrum characteristics of the plurality of fluorescent probes;a dispersion control unit which controls the dispersion unit based on the set spectral data acquisition condition; anda photoelectric conversion unit which receives the extracted fluorescent light, and which converts the received light into an electrical signal;wherein the dispersion unit comprises a diffraction mirror for dispersing the fluorescent light from the specimen and selecting a wavelength of the fluorescent light, and a slit for selecting a the arbitrary wavelength section of the dispersed fluorescent light to be received by the photoelectric conversion unit in accordance with the selected wavelength; andwherein the spectral data acquisition condition setting unit sets a wavelength incrementing amount corresponding to a rotation angle of the diffraction mirror and a spectral resolution corresponding to a width of the slit, which are applicable to carrying out a wavelength scanning for the specimen based on the spectrum characteristics of the plurality of fluorescent probes. 3. The laser scanning microscope according to claim 2, wherein the spectral data acquisition condition setting unit comprises:a proximate inter-peak distance calculation unit for calculating a distance between proximate peak wavelengths among a plurality of peak wavelengths of the fluorescent light from the plurality of fluorescent probes;an incrementing amount setting unit for setting the wavelength incrementing amount based on the calculated distance between proximate peak wavelengths; anda spectral resolution setting unit for setting the spectral resolution based on the calculated distance between proximate peak wavelengths; andwherein the dispersion control unit controls the dispersion unit based on the set spectral resolution and the set wavelength incrementing amount. 4. The laser scanning microscope according to claim 3, further comprising an acquisition start and end positions specification unit which is adapted to specify acquisition start and end wavelengths of the spectral data. 5. The laser scanning microscope according to claim 3, further comprising an acquisition range setting unit for setting acquisition start and end wavelengths of an acquisition range of the spectral data based on the spectrum characteristics of the plurality of fluorescent probes. 6. The laser scanning microscope according to claim 5, wherein the acquisition range setting unit sets the acquisition range of the spectral data so as to include all of the peak wavelengths of the fluorescent light from the fluorescent probes. 7. The laser scanning microscope according to claim 5, wherein the acquisition range setting unit sets acquisition start or end positions for the spectral data by using a value of wavelength of each edge in curves which decreases by a prescribed ratio from each peak value of curves being the lowest or the highest wavelength. 8. The laser scanning microscope according to claim 3, wherein the wavelength scanning for the specimen obtains the spectral data in a plurality of acquisition sections corresponding to successive wavelength ranges extracted in accordance with the set spectral resolution and incremented by the wavelength incrementing amount,wherein the spectral data acquisition condition setting unit further comprises a section judgment unit for judging whether or not one of the acquisition sections is set so as to include two among: the peak wavelengths of the fluorescent light from the fluorescent probes and any of said at least one excitation wavelength of the laser beam emitted onto the specimen, andwherein the dispersion control unit controls the dispersion unit based on the set acquisition sections if it is judged that each of the acquisition sections includes one or less among: the peak wavelengths of the fluorescent light from the fluorescent probes and any of said at least one excitation wavelength of the laser beam emitted onto the specimen. 9. The laser scanning microscope according to claim 8, wherein the spectral data acquisition condition setting unit further comprises a section division unit for dividing the acquisition sections into a prescribed number if the one of the set acquisition sections is set so as to include at least two among: the peak wavelengths of the fluorescent light from the fluorescent probes and any of said at least one excitation wavelength of the laser beam emitted onto the specimen,wherein the section judgment unit judges whether or not one of the divided acquisition sections includes two among: the peak wavelengths of the fluorescent light from the fluorescent probes and any of said at least one excitation wavelength of the laser beam emitted onto the specimen. 10. The laser scanning microscope according to claim 9, further comprising: a lowest limit resolution value storage unit for storing a lowest limit value of the spectral resolution which enables detection of a peak of fluorescent light; anda section width judgment unit for judging whether or not a section width of into which the acquisition sections are divided by the section division unit is equal to or less than the lowest limit value,wherein the dispersion control unit controls the dispersion unit based on the divided acquisition sections if the section width of is judged to be larger than the lowest limit value. 11. The laser scanning microscope according to claim 3, wherein the wavelength scanning for the specimen obtains the spectral data in a plurality of acquisition sections corresponding to successive wavelength ranges extracted in accordance with the set spectral resolution and incremented by the wavelength incrementing amount,wherein the laser scanning microscope further comprises:a lowest limit resolution value storage unit for storing a lowest limit value of the spectral resolution which enables detection of a peak of fluorescent light; anda section width judgment unit for judging whether or not a section width the acquisition sections is equal to, or smaller than, the lowest limit value,wherein the dispersion control unit controls the dispersion unit based on the set acquisition sections if the section width is judged to be larger than the lowest limit value. 12. The laser scanning microscope according to claim 3, wherein the wavelength scanning for the specimen obtains the spectral data in a plurality of acquisition sections corresponding to successive wavelength ranges extracted in accordance with the set spectral resolution and incremented by the wavelength incrementing amount, andwherein the spectral resolution setting unit sets the spectral resolution and the wavelength incrementing amount so that borders of the wavelength ranges of adjacent acquisition sections contact with each other. 13. The laser scanning microscope according to claim 3, wherein the wavelength scanning for the specimen obtains the spectral data in a plurality of acquisition sections corresponding to successive wavelength ranges extracted in accordance with the set spectral resolution and incremented by the wavelength incrementing amount, andwherein the spectral resolution setting unit sets the spectral resolution and the wavelength incrementing amount so that the wavelength ranges of adjacent acquisition sections overlap with each other for a prescribed interval. 14. A computer readable storage medium storing a spectral data acquisition program that is executable by a computer to cause the computer to carry out processing for setting a spectral data acquisition condition for acquiring spectral data with a laser scanning microscope which enables observation of a specimen, which is marked by a plurality of fluorescent probes, by emitting a laser beam onto the specimen and receiving fluorescent light, corresponding to the emission of the laser beam, back from the specimen, the program causing the computer carry out a process comprising:calculating a proximate inter-peak distance between approximate peak wavelengths among a plurality of peak wavelengths of the fluorescent light from the plurality of fluorescent probes;setting a wavelength incrementing amount corresponding to a rotation angle of a diffraction mirror which disperses the fluorescent light from the specimen into a spectrum and selects a wavelength, based on the calculated proximate inter-peak distance;setting a spectral resolution corresponding to a slit width of a slit which selects a wavelength section of the received fluorescent light, based on the calculated proximate inter-peak distance; andacquiring the spectral data based on the set wavelength incrementing amount and the set spectral resolution. 15. A method for defining a spectral data acquisition condition and acquiring spectral data with a laser scanning microscope which enables observation of a specimen, which is marked by a plurality of fluorescent probes, by emitting a laser beam onto the specimen and receiving fluorescent light, corresponding to the emission of the laser beam, back from the specimen, the method comprising:calculating a proximate inter-peak distance between proximate peak wavelengths among a plurality of peak wavelengths of fluorescent light from the plurality of fluorescent probes;setting a wavelength incrementing amount used for spectrally receiving the fluorescent light back from the specimen based on the calculated proximate inter-peak distance;setting a spectral resolution which is a wavelength section for one acquisition of the received fluorescent light based on the calculated proximate inter-peak distance; andacquiring the spectral data based on the set wavelength incrementing amount and the set spectral resolution. 16. The spectral data acquisition method according to claim 15, wherein acquiring the spectral data is carried out based on acquisition start and end wavelengths of the spectral data. 17. The spectral data acquisition method according to claim 15, further comprising: setting acquisition start and end wavelengths of the spectral data based on spectrum characteristics of the plurality of fluorescent probes,wherein acquiring the spectral data is carried out based on the acquisition start and end wavelengths of the spectral data. 18. The spectral data acquisition method according to claim 15, wherein the spectral data is obtained in a plurality of acquisition sections, which correspond to wavelength ranges incremented by the wavelength incrementing amount and acquired in successive said acquisitions in accordance with the spectral resolution, andwherein the method further comprises:judging whether or not one of the acquisition sections is set so as to include two among: the peak wavelengths of the fluorescent light from the fluorescent probes and any of said at least one excitation wavelength of the laser beam emitted onto the specimen, andacquiring the spectral data based on the set acquisition sections sections if it is judged that each of the acquisition sections includes one or less among: the peak wavelengths of the fluorescent light from the fluorescent probes and any of said at least one excitation wavelength of the laser beam emitted onto the specimen. 19. The spectral data acquisition method according to claim 18, further comprising:dividing the acquisition sections into a prescribed number if the one of the set acquisition sections is set so as to include at least two among: the peak wavelengths of the fluorescent light from the fluorescent probes and any of said at least one excitation wavelength of the laser beam emitted onto the specimen, andjudging whether or not one of the divided acquisition sections includes two among: the peak wavelengths of the fluorescent light from the fluorescent probes and any of said at least one excitation wavelength of the laser beam emitted onto the specimen. 20. The spectral data acquisition method according to claim 15, wherein the spectral data is obtained in a plurality of acquisition sections, which correspond to wavelength ranges incremented by the wavelength incrementing amount and acquired in successive said acquisitions in accordance with the spectral resolution, andwherein the method further comprises setting the spectral resolution and the wavelength incrementing amount so that borders of the wavelength ranges of adjacent acquisition sections contact with each other. 21. The spectral data acquisition method according to claim 15, wherein the spectral data is obtained in a plurality of acquisition sections, which correspond to wavelength ranges incremented by the wavelength incrementing amount and acquired in successive said acquisitions in accordance with the spectral resolution, andwherein the method further comprises setting the spectral resolution and the wavelength incrementing amount so that the wavelength ranges of adjacent acquisition sections overlap with each other for a prescribed interval. 22. The spectral data acquisition method according to claim 15, further comprising setting acquisition start or end positions for the spectral data by using a value of wavelength of each edge in curves which decreases by a prescribed ratio from each peak value of curves being the lowest or the highest wavelength. 23. A laser scanning microscope, which enables observation of a specimen, which is marked by a plurality of fluorescent probes, by emitting a laser beam onto the specimen and receiving fluorescent light, corresponding to the emission of the laser beam, back from the specimen, the laser scanning microscope comprising:proximate inter-peak distance calculation means for calculating a proximate inter-peak distance between proximate peak wavelengths among a plurality of peak wavelengths of fluorescent light from the plurality of fluorescent probes;incrementing amount setting means for setting a wavelength incrementing amount based on the calculated proximate inter-peak distance;spectral resolution setting means for setting a spectral resolution which is a wavelength section for receiving fluorescent light based on the calculated proximate inter-peak distance; andspectral data acquisition means for acquiring spectral data based on the set wavelength incrementing amount and the set spectral resolution. 24. A method for defining a spectral data acquisition condition and acquiring spectral data with a laser scanning microscope which enables observation of a specimen, which is marked by a plurality of fluorescent probes, by emitting a laser beam onto the specimen and receiving fluorescent light, corresponding to the emission of the laser beam, back from the specimen, the method comprising:generating the laser beam in at least one excitation wavelength which corresponds to the plurality of fluorescent probes;storing spectrum characteristics of the plurality of fluorescent probes;scanning the generated laser beam over the specimen;dispersing the fluorescent light from the specimen into a spectrum and selecting a wavelength of the fluorescent light using a diffraction mirror;extracting the dispersed fluorescent light by an arbitrary wavelength section using a slit, based on the selected wavelength;setting a wavelength incrementing amount corresponding to a rotation angle of the diffraction mirror and a spectral resolution corresponding to a width of the slit, based on the spectrum characteristics of the plurality of fluorescent probes as a spectral data acquisition condition to acquire the spectral data;controlling the diffraction mirror and the slit based on the spectral data acquisition condition; andreceiving the extracted fluorescent light and converting the received light into an electric signal.
summary
041750004
description
DESCRIPTION OF THE PREFERRED EMBODIMENTS For a more complete appreciation of the invention, attention is invited to FIG. 1, which shows a spent fuel element pool 10. The pool 10 usually is filled with water (not shown in FIG. 1) that is confined in a reinforced concrete well 11. A steel framework or fuel element storage rack 12 is provided at the bottom of the generally rectangular pool 10 in order to support fuel elements (also not shown in FIG. 1). As hereinbefore mentioned, these fuel elements usually are withdrawn from a nuclear reactor core in a partially used or in a "spent" condition. In these circumstances, personnel protection and good radiation safety procedures require that adequate shielding should be provided to attentuate the radiation that is emitted because of the residual radioactivity in these fuel elements. According to accepted radiation safety standards, moreover, a ten-foot depth of water between the pool surface and the closest part of any used or spent fuel element is adequate for personnel protection. Applying this standard to the instant invention, it is clear that all the subsequently described manipulations must be accomplished under not less than a ten-foot depth of water. Turning once more to FIG. 1 of the drawing, a track 13 is formed above the water level on the margin of the pool 10. The track 13, and an oppositely disposed parallel companion track 14, extend along the entire length of two opposing sides of the pool. In accordance with a feature of the invention, a movable bridge 15 spans the surface of the pool between the tracks 13 and 14 in a direction that is perpendicular to the longitudinal orientation of these tracks. The extreme ends of the bridge 15, moreover, are rigidly secured to respective trucks 18 and 19 that support the bridge and enable it to travel on the tracks 13 and 14. The trucks 18 and 19 have sets of wheels 16 and 17, respectively, that roll on the tracks 14 and 13 and promote the bridge translation. More specifically, the bridge 15 has depending members 20, 21, 22, and 23 that are secured to two parallel wide flange beams 24 and 25 that form the spanning portion of the bridge structure. The depending members 20, 21, 22, and 23 protrude downwardly into the water (not shown in FIG. 1). Within the pool 10, a strongback 26 is temporarily disposed in a direction that is below and generally parallel to the two beams 24 and 25. The strongback 26, however, is pivoted to the lower extremities of the depending members 20 and 21 by means of a pin 27, or the like. A horizontal stop 30 connects the depending members 22 and 23 and engages the upper free end of the strongback 26 in order to limit the travel of the strongback. The strongback and the depending members all are supported on wheeled carriages for span-wise movement on the lower flanges of the beams 24 and 25 of the bridge 15. This pivotal movement of the strongback 26 is controlled through the selective operation of a motor-driven winch 31, best shown in FIG. 2, and an associated cable 32. The cable 32 is wound and unwound on a drum that is driven by the winch 31 to raise and lower the free end of the strongback 26 as shown in broken and continuous lines. The winch 31 is, moreover, rigidly secured to the beam 24. The strongback 26 can be pivoted, moreover, from the depending members 22 and 23. To shift the pivotal point, the pin 27 (FIG. 2) can be withdrawn after a similar pin 27' has been inserted through the lower ends of the members 22 and 23. In this situation, moreover, the winch 31 and the cable 32 should be repositioned near the truck 18 (FIG. 1) and the cable 32 should be attached to the end of the strongback 26 that is nested between the depending members 20 and 21. Thus, the bridge enables the strongback 26 to be placed in a vertical position in either orientation. It can be further seen in FIG. 1 that a trolley 34 is adapted to roll on tracks 35. The tracks 35 are formed on the upper flanges of the bridge. The trolley 34 also is equipped with a pair of wheeled trucks 38 and 39 (FIG. 1) that align the wheels in the respective trucks in alignment with the upper flanges of the beams 24 and 25. The trolley 34 extends across the gap between the two parallel beams 24 and 25 for the purpose of providing a movable equipment support. As shown in FIG. 2 for instance, submerged combination periscope and television camera 36 is supported on the trolley 34. As illustrated, the trolley in traversing the tracks 35 on the bridge 15 enables the periscope 36 to scan the exposed upper surface of a fuel element 37 that is lodged on the strongback 26. In this manner a thorough visual inspection of the exposed upper horizontal surface of the fuel element 37 can be carried out in safety under the prescribed ten-foot depth of water. Naturally, the trolley provides a suitable support for other types of inspection devices, manipulators and remotely operated tools that are needed to complete the disassembly, inspection, and assembly of the fuel element 37 as described subsequently in more complete detail. In operation, the depending members 20 and 21 remain stationary as the cable 32 is unreeled from the winch 31 to enable the strongback 26 to pivot from the horizontal, as shown in solid lines, to the vertical, as shown in broken lines. While the strongback is vertically erect, a crane (not shown) or other suitable remote manipulator lifts fuel element 37' (FIG. 2) that is designated for inspection from the storage rack 12. The crane nests or cradles the fuel element in the vertical strongback 26. Because the free end of the strongback 26 has an end plate 28 (FIG. 1) the lower end of fuel element 37 rests on that plate. In this manner, the fuel element 37 is supported in the erect position when the strongback is pivoted to the vertical. Mechanical clamps, bands or the like, (not shown in the drawing) are used to secure the fuel element 37 in the stongback 26. These bands preferably are applied with the aid of remote handling equipment, e.g. conventional pool tongs. The winch 31 is activated to reel in the cable 32 and draw the free end of the strongback 26 from the vertical into the horizontal position as shown in solid lines in FIG. 2 of the drawing. The upper horizontal surface of the fuel element 37 is exposed for inspection through the combination television camera and periscope 36, "feeler" gauges and the like. It will be recalled that the remaining three outer surfaces of the typical fuel element under consideration also should be exposed for inspection. To accomplish this purpose, the fuel element 37 and the strongback 26 should be once more lowered into the vertical position. The bands or clamps that secure the fuel element to the strongback must be loosened or released and the remote manipulator activated to withdraw the fuel element 37 from the strongback. In the case of a fuel element that has an essentially square or rectangular cross section, the manipulator also rotates the fuel element through 90.degree. in either direction, or through 180.degree., to expose one of the three remaining unexamined sides. After the fuel element has been rotated through an angle that is appropriate to the side to be exposed, the manipulator replaces the fuel element in the strongback 26 and the process of clamping, leveling, and inspecting is repeated once more. All of these steps, including the rotation step, are repeated for each side until all of the exposed lateral sides of the fuel element have been subjected to an acceptable inspection. It will be recalled that the fuel rods that comprise most of the interior of the fuel element 37 also must be inspected. In the past, this need to examine the inner fuel rods imposed a requirement to destroy significant and expensive fuel element structural components. In this regard, FIG. 4 shows a portion of a typical cell 43 in one of the grids 48 (FIG. 2) that engages fuel rod 54. These grids are generally transverse to the longitudinal dimension of the individual fuel rods and are laterally spaced from each other. As described in more complete detail in U.S. Pat. No. 3,655,586 granted on May 30, 1972 to Felix S. Jabsen for "Nuclear Fuel Rod Supporting Arrangements", the grid is formed from a lattice of generally perpendicularly intersecting plates that establish an array of rectangular cells. Individual fuel rods are received in each of these cells. Small protrusions formed in the surfaces of the plates extend into the respective cells and bear against adjacent portions of the respective fuel rods surfaces in order to retain these rods in their relative positions and to suppress vibration or other undesirable motion. To remove the fuel rods from the individual cells, slots are provided in the cell corners to permit a cell wall deflecting key to be inserted into the grid structure. As described in the aforementioned patent, the keys are rotated within the grid structure to enable bosses on these keys to press the protrusions back out of the respective cells. So arranged, the individual fuel rods can be inserted into the grid cells without risk of gouging or scoring. After the fuel rods are situated within the grid, the keys are rotated in a direction that will disengage the bosses from the cell surfaces and thus allow the protrusions on the cell walls to extend into the respective cells and press against adjacent fuel rod surfaces. Remotely controlled withdrawal of the fuel rods from the grid structure for inspection purposes, however, can produce undesirable scratches and scoring on the rod surfaces unless some means is provided to relieve the forces that press the grid protrusions against the adjacent rods. In accordance with a further characteristic of the invention this problem is overcome through the bridge 15 (FIG. 2). Once having mounted a fuel element of the strongback 26 and having inspected the external surfaces of the fuel element, as hereinbefore mentioned, it is frequently advisable to remove individual fuel rods from the assembly for individual inspection and replacement, as indicated. Prior to the instant invention, it was necessary to cut the grids apart with the aid of remote handling equipment in order to provide access to individual fuel rods without scraping or scoring the rod surfaces on the protruding grid detents that otherwise would occur if the rods had been pulled out of the grids in a longitudinal direction. In accordance with the invention, however, the individual rods can be removed from the fuel element structure in an essentially non-destructive manner. For illustrative purposes, a fuel element of the type shown in my abandoned U.S. patent application Ser. No. 2,767 filed Jan. 14, 1970 for "Fuel Assembly For A Nuclear Reactor" will be used in connection with the description of the apparatus and methods that characterize this invention. As described in the aforesaid patent application, each fuel element has an upper end grid and a lower end grid to receive and constrain the extreme ends of the fuel rods in the array. Fuel rod stability is enhanced by means of the fuel element grid structure that engages the rods in transverse planes in between the two end grids, as described in more complete detail in the aforementioned U.S. Pat. No. 3,665,586. Although the ends of the individual fuel rods are received in the upper and lower end grids, the lower grid is secured to the upper grid through an array of control rod guide tubes. These tubes extend through the entire fuel element to enable threaded ends to protrude from the upper surface of the upper end grid and to protrude from the lower surface of the lower end grid. Threaded nuts are received on these protruding guide tube ends and, in this manner, clamp the two end grids together and secure the fuel rods between the two end grids. Accordingly, in order to dismount the fuel element 37 (FIG. 2) the fuel element is once more cradled in the horizontally disposed strongback 26. A conventional remote manipulator that is mounted on the trolley 34 is used to unscrew the nuts (not shown) that clamp together the upper and lower end grids (also not shown). For this purpose, Model MU-128 Pool Tongs available from Optics for Industry, 1929 N. Buffum Street, Milwaukee, Wisconsin are suitable. Continuing with the description of the fuel element disassembly, the nuts are removed and stowed within the pool 10 for subsequent use. The strongback 26 is once more lowered into an erect position. The pool tongs are then used to withdraw the control rod guide tubes and the upper end grid (not shown) from the fuel element 37. At this point in the procedure, for radiological safety, care must be exercised to maintain a ten-foot depth of water between the surface of the pool 10 and that part of the guide tube which is closest to the pool water surface. The withdrawn control rods and the upper end grid also are stowed within the pool. The now partially disassembled fuel element 37 is turned up-side-down to permit the lower end grid to face the surface of the pool water. In this position, the remote manipulator is used to remove the lower end grid from the fuel element and stow this lower end grid in some accessible place within the pool 10. Depending on the specific design of the fuel element being disassembled, it may be necessary to once more rotate the element through 90.degree. quadrants in order to expose all of the end grid nuts or fasteners to the grasp of the pool tongs. In a similar manner, tack welds that often are applied to prevent these fasteners from working loose during reactor operation also must be sliced through with remotely manipulated tools to allow the end grids and the control rod guide tubes to be withdrawn from the fuel element. The partially disassembled fuel element now consists only of the array of fuel rods that are held in position by means of the transverse grids which were positioned on the rods at stations in between the upper and lower end grids. In accordance with the invention, the strongback 26 (FIG. 2) raises the fuel assembly to a horizontal position in order to aid in releasing the grip that is established by the protruding grid detents on the fuel rods. Attention is invited to FIG. 3 which shows a typical bar 40 for use in releasing this engagement between detents and fuel rod. Preferably, the bar 40 has longitudinal shank portions 41 which are generally rectangular in transverse cross section. Protrusions 42 extend from the shank portions 41 of the bar 40 at regular intervals. Turning now to FIG. 4, a typical cell 43 in a larger grid structure (not shown in FIG. 4) comprises an array of four interlocking plates 44, 45, 46, and 47 that are spot welded at the mutually perpendicular intersections. Rigid detents 50, 51, 52, and 53 are stamped or formed in the respective surface of each of these plates. These detents protrude into the illustrative cell that is defined by the portions of the plates 44 through 47. The detents 50, 51, 52, and 53 rigidly engage the outer surface of the fuel rod 54 and serve to secure the rod 54 in proper relative position with respect to the array of rods and other structure components that comprise the fuel element (37 in FIG. 1). The bars 55 and 56 are inserted into the cell 43 through apertures formed in the vertical sides of the plates 44 through 47 at the intersection of the plates 44 and 45, 46 and 45, and 46 and 47. The bars, as shown in FIG. 4, should be inserted into the cell 43 with the protrusions 42 and 42' oriented in a vertical direction that is perpendicular to the plane of the drawing. With the protrusions 42 and 42' so oriented, the apertures in the cell 43 provide a sufficient clearance to enable the bars 42 and 42' to enter the cell 43. The protrusions 42 and 42', moreover, are positioned close to the adjacent cell walls. Naturally, although the bars 55 and 56 must be sufficiently strong to deflect the cell walls, they also must be sufficiently slender to fit within the space between the fuel rod 5- and the adjoining plates 45 and 46, respectively. This clearance is established by the depth to which the respective detents 51 and 52 protrude into the cell 43. During bar insertion the protrusions 42 and 42' are not in engagement with the structure of the cell 43. In order to relax the grip that the detents 50 through 53 apply to the fuel rod 54, and thus to enable the rod to be withdrawn from the grid structure without scoring, scraping, or otherwise marring the metal surface, attention is invited to FIG. 5. In FIG. 5 bars 55 and 56 are rotated through 90.degree. in a clockwise direction about the respective longitudinal axes of the bars in the plane of the drawing as shown by the arrows in FIG. 5. This rotation aligns the protrusions 42 and 42' with the adjacent cell walls that support the associated detents 51 and 52. In this condition, the protrusions 42 and 42' press the detents 51 and 52 in order to deflect these detents out of the cell 43 and thereby disengage all of the detents 50 through 53 from the surface of the fuel rod 54. This apparently slight outward movement of the detents 51 and 52 is sufficient to allow the fuel rod 54 to be withdrawn from the cell 43 in the grid structure without abrading or scraping the fuel rod surface against the detents. In another embodiment of the invention, however, the bar, or key 40, has a rectangular cross section. The short side of this rectangle is sufficient to slide through the gap between the protruding tip of one of the detents 50, 51, 52 and 53 and an associated one of the plates 44, 45, 46 and 47. The long side of the rectangle, moreover, must be large enough to deflect the adjacent plate a sufficient amount to release the rod 54 when the long dimension is rotated into contact with the plate. This procedure is repeated for all of the cells in all of the grid structures that are in engagement with the fuel rods in the array. The rods, moreover, are individually withdrawn from the array. Illustratively, remotely operated pool manipulators are used to withdraw each fuel rod from the partially disassembled fuel element array. To improve disassembly efficiency and, in accordance with a further aspect of the invention, parallel flat camming plates 64 and 65 (FIGS. 6 and 8) are provided to engage two opposite and parallel sides of a grid 66. The camming plates 64 and 65, moreover, have conical openings 67, 70, 71, and 72 formed with the truncated apices of the individual cones pointing inwardly toward the sides of the grid 66. As shown in the drawing, bars 68 and 69 are essentially guided by the conical openings through the apertures at the grid plate intersection (not shown in FIG. 6, but shown in FIGS. 4 and 5). Thus, two pool manipulators each grasp a respective handle 90 (FIG. 8) on the two respective camming plates 64 and 65. The manipulators press the respective plates up against the grid 66 (FIG. 6). Alignment cams 91 and 92 (FIG. 8) on the plate 64 center the conical openings 67 and 70 with the corresponding apertures in the grid 66 (FIG. 6). A third pool manipulator inserts bars end-first into the individual conical openings. The cones act as cams to guide the bars into the grid structure through retangular slots formed at the truncated apices of each of the cones to establish the proper orientation relative to the grid structure that is shown in FIG. 4. In order to rotate the bars 68 and 69 (FIG. 6) into the orientation that is shown in FIG. 5, the camming plates 64 and 65 are withdrawn and a fixture 63 embraces three of the four sides of the now bar-loaded grid 66. Bar-ends or terminal bar portions 73, 74, 75, and 76 protrude beyond the margin of the grid 66. For simiplicity of disclosure, however, the camming plates 64 and 65 are shown in contact with the grid 66 at the same time as the fixture 63. Mating nipples 81, 82, 83, and 84 on the fixture 63 are in alignment with the adjacent terminal bar portions. The nipples 81 through 84 are only shown as an illustrative group of four in a much larger nipple array that is mounted on the fixture 63. As shown in connection with the nipple 82, each nipple has a truncated conical recess 85 that has a truncated apex oriented away from the grid 66. The conical recess serves as a further cam or guide that directs the adjacent terminal bar portion 74 into a female slot 86 that has a shape which matches the cross section of the terminal bar portion 74. All of the nipples 81 through 84 are secured for pivotal movement to respective cranks that are essentially the same as two illustrative cranks 87 and 88. The crank 87, moreover, is journaled in two spaced-apart parallel plates 93 and 94. In a similar manner, the crank 88 also is jounaled in two parallel spaced-apart plates 95 and 96. The journaling described for the nipples 82 and 84 is, of course, repeated for all of the nipples on the fixture 63. The pairs of journal plates 93 and 94, 95 and 96, form two rigid rectangles as seen in FIG. 6 of the drawing. The crank 87, as well as all of the other cranks (not shown) that are journaled in the plates 93 and 94, are ganged together for rotational movement by means of a connecting rod 97. A parallel connecting rod structure 98 is provided for the cranks that are journaled between the journal plates 95 and 96. Movement is imparted to the connecting rods 97 and 98 (and hence, to the respective sets of nipples through the ganged cranks) by means of a yoke 100. The yoke 100 has a central aperture 101 that receives a shaft 102. The shaft 102, moreover, is pressed firmly against the side of the grid cell. The shaft 102 has a rack 103 that meshes with a pinion gear 104. The pinion gear is journaled in a collar 105 that is secured to the yoke 100. This structure enables the yoke 100 to move in the two linear directions as indicated by the double headed arrow 106. A lever 107 on the pinion gear 104 is manipulated by means of pool tongs, or the like, to drive the yoke in either direction along the shaft 102. This limited movement of the yoke 100 is sufficient to enable the individual cranks to sweep through a 90.degree. arc. As shown in FIG. 7, one end of the connecting rod 97 has a slot 110 that receives a pin 111 on the yoke 100 to accommodate the irregular or non-linear connecting rod movement. The other end of the connecting rod 97 is received in a slot 112 that is formed in a base 113 for the frame of journal plates 93, 94 (FIG. 6). The end of the connecting rod 97 (FIG. 7) that is received in the base 113 also has a stop 114 to insure that the connecting rod 97 does not disengage itself from the slot 112. As described the combination of the connecting rod 97, pin 111, slot 110, and the slot 112 with the stop 114 enables the essentially reciprocating stroke of the yoke 100 to translate into the non-linear motion of the connecting rod and the associated cranks. In accordance with the invention, a similar structural arrangement is provided for the cranks that are associated with the connecting rod 98 and the journal plates 95 and 96. To mate the terminal bar portions 75, 76 (FIG. 6) of the bars 68 and 69 with the nipples 83 and 84 and to mate the nipples 81 and 82 with the terminal bar portions 73 and 74, a further pair of racks 115 and 116 on sliding members 117 and 120, respectively, are provided. These racks 115 and 116 mesh with a pinion gear 121 on the stub end of the shaft 102. The sliding members 117 and 120 are arranged in an overlying, stacked relationship, the member 120 being sandwiched between the member 117 and a fixed, or immobile member 122. The member 122 not only provides a rigid support for the sliding members, but also has a recess 123 in which the stub end of the shaft 102 is journaled. Guide pins 124 and 125 protrude from the member 122 through mating slots 126 and 127, respectively and slots 130 and 131. The slots 126 and 130 are formed in the sandwiched sliding member 120 and the slots 127 and 131 are formed in the outer sliding member 117. The pins 124 and 125 with their associated slots cooperate with the pinion gear 121 by driving the members 117 and 120 in opposite lateral directions for distances that are determined by the lateral dimensions of the particular slots. These slot dimensions, moreover, are of sufficient size to enable the fixture 63 to be positioned about three sides of the grid 66 without engaging the exposed ends of the bars 68 and 69, as shown in FIG. 6. In operation, the shaft 102 is rotated to extend the sliding members 117 and 120 as far as possible in opposite lateral directions. The fixture 63 then is fitted around the grid 66, to embrace three sides of the grid. One side of the grid contacts the fixed member 122. As shown, the member 122 has a pair of guides 132 and 133 which align the fixture with the terminal bar portions 73, 74, 75 and 76. The shaft 102 is rotated to draw together the sliding member 117 and 120 and, in this manner, to engage the terminal bar portions within the adjacent female slot 86 of the nipples 81 through 84. The rack 105 is formed on the shaft 102 as a sequence of gear teeth that completely circumscribe the shaft. In this way, rotation of the shaft 102 for the purpose of shifting the position of the sliding members 117 and 120 will not disengage the lever operated pinion gear 104 from the rack 105. To rotate the bars 68 and 69 through 90.degree. in order to produce the bar orientation and detent relaxation that is shown in FIG. 5, the lever 107 is manipulated to drive the yoke 100 in a direction that is parallel to the axis of the shaft 102. This motion moves the connecting rods 97 and 98 with their respective sets of ganged cranks 87 and 88 through a 90.degree. arc. This rotation is transmitted from the nipples 81 through 84 through the entire length of the bars 68 and 69, thereby partially "opening" the cells. The shaft 102 (FIG. 6) is rotated in an opposite direction to shift the sliding members 117 and 120 as far apart as possible in a lateral direction. Thus, the bars 68 and 69 are disengaged from the nipples, and the balance of the fixture 63. The fixture 63 now can be withdrawn from the grid 66 and the partially dismantled fuel element, and either set aside or used to rotate the bars in another grid on the fuel element. It should be noted in FIGS. 4 and 5 that the bars, or the keys 55 and 56 intersect within the cell 43. In order to insert the second set of coordinate keys in the grid 66 (FIG. 6) the fuel element is once more placed on the strongback 26 (FIG. 2). The fuel element 37 is so positioned that the keys protrude from the grid in a vertical direction. Small clearance blocks (not shown in FIGS. 1 and 2) are secured to the strongback 26 to enable the fuel element to rest on these blocks and allow the ends of the keys to clear the horizontal surface of the strongback. The camming plates 64 and 65 (FIG. 8) are placed against the vertical sides of the grid 66 and a coordinate set of horizontally disposed keys are inserted into the fuel element in the manner described above. After key insertion, the camming plates 64 and 65 are removed to enable the fixture 63 (FIG. 6) to embrace the grid 66. The alignment guides 132 and 133 (or a set of alignment guides that will provide clearance for the protruding ends of the vertical keys) position the fixture 63 on the grid 66 in proper position relative to protruding ends of the coordinate horizontal keys and the nipples 81 through 84. Appropriate recesses, for example, can be formed in the fixed member 122 to accommodate the vertical adjacent ends of the keys that protrude from the grid 66. After the fixture 63 is aligned, the fixture and the horizontal array of keys are manipulated as described above to relieve the engagement between the detents 50 through 53 (FIGS. 4 and 5). The disassembly, inspection and reassembly proceeds as indicated. In accordance with a further feature of the invention, the fixture 63 can be supported from the trolley 34 (FIG. 2) on the bridge 15 and remotely operated from the side of the pool 10. With the relaxed grip between the cell detents and the respective fuel rods as hereinbefore described, pool tongs (not shown) are manipulated to withdraw the fuel rod 54 (FIG. 5) from the cell 43 in a direction that is perpendicular to the plane of the drawing. To reassemble the fuel element from the individual components after inspection is complete, individual fuel rods 54 (FIG. 5), of which the rod shown is typical, are reinserted into the cells on the grids. The fixture 63 (FIG. 6) is moved into place on the grid 66 and the nipples 81 through 84 are once more engaged with the bars 68 and 69. This is accomplished through rotation of the shaft 102 to draw together the sliding members 117 and 120. The lever 107 is manipulated once more to operate the connecting rods 97 and 98 with their respective cranks. This manipulation rotates the bars 68 and 69 (FIG. 6) backward through 90.degree. in a direction opposite to that which initially deflected the grid detents. The shaft 102 (FIG. 6) is once more rotated to shift the sliding members 117 and 120 in a lateral direction that will disengage the nipples 81 through 84 from the bars 68 and 69. The fixture 63 is removed from contact with the grid 66 and is applied to the coordinate set of rods that are shown in FIGS. 4 and 5. The fixture by now is available for application to another grid or is placed aside in the pool 10 (FIG. 1) for subsequent transport to a new job site. The now partially reassembled fuel element as lifted by means of a manipulator (not shown) and placed on end, if needed, to replace one of the fuel element end grids. The fuel element now is placed on the installed end grid and the other end grid also is added to the element. The control rod guide tubes are inserted through the end grids and the associated nuts are screwed on to the exposed threaded ends of these tubes. The fuel element is once more up-ended to enable the nuts to be threaded onto the exposed threaded ends of the guide tubes that protrude beyond the surface of the first-installed end grid. The fuel element has been completely dismantled, inspected and reassembled without inflicting any appreciable damage on the individual components. Although the invention is described in connection with the inspection of full spent or partially consumed nuclear reactor fuel elements, the techniques disclosed herein are also applicable to the assembly and inspection of new fuel elements.
summary
claims
1. A treatment planning system for creating treatment plan information for particle therapy, comprising:an input device;an arithmetic device for performing arithmetic processing based on a result of input to the input device and creating treatment plan information; anda display device for displaying the treatment plan information,wherein the arithmetic device calculates a scanning path by setting a pre-specified direction as a main direction for scanning irradiation positions with an ion beam using scanning magnets, the pre-specified direction being along a direction of movement of a target of treatment, andwherein the display device displays the direction of movement of the target of treatment. 2. The treatment planning system according to claim 1,wherein the arithmetic device extracts the direction of movement of the target of treatment using at least one feature points in one or more images. 3. The treatment planning system according to claim 2,wherein the arithmetic device calculates the scanning path based on the at least one feature points in the one or more images in different phases projected on an isocenter plane relative to the ion beam, where the at least one feature points are markers. 4. The treatment planning system according to claim 2,wherein the arithmetic device calculates the scanning path based on the at least one feature points in the one or more images in different phases which exist in a specified region of the target and are projected on an isocenter plane relative to the ion beam, where the at least one feature points are markers. 5. The treatment planning system according to claim 2,wherein the arithmetic device calculates the scanning path based on the at least one feature points of the one or more images in different phases, where the at least one feature points are markers. 6. The treatment planning system according to claim 1,wherein the display device displays the moving direction of the target of treatment and at least one feature point. 7. The treatment planning system according to claim 1,wherein the display device displays the scanning path calculated by the arithmetic device. 8. The treatment planning system according to claim 1,wherein the display device displays a component of the direction of movement of the target of treatment perpendicular to an isocenter plane with respect to the ion beam. 9. The treatment planning system according to claim 1,wherein the direction of movement of the target of treatment extracted by the arithmetic device is changed according to the input received by the input device. 10. The treatment planning system according to claim 1,wherein the direction of movement of the target of treatment is specified according to the input received by the input device.
061880736
abstract
A radiographic intensifying screen is composed of a support, a phosphor layer containing phosphor and a surface protective layer overlaid in order. The surface protective layer shows a scattering length of 5 to 80 .mu.m, in which the scattering length is measured at main wavelength of light emitted from the phosphor.
summary
061472743
claims
1. A process for decontaminating a contaminated material comprising: providing a solution containing less than 50 milli-moles of fluoroboric acid per liter; contacting the fluoroboric acid solution with a material which causes the oxidation potential (Eh) of the solution to range from about 500 to about 1200 mV versus a Standard Calomel Electrode, wherein the material which causes the oxidation potential (Eh) of the solution to range from about 500 to 1200 mV is selected from the group consisting of hydrazine, hydrogen peroxide, ozone, potassium permanganate and combinations thereof; contacting the fluoroboric acid solution with the contaminated material; and, removing a contaminant from the contaminated material by continuously contacting the fluoroboric acid solution with a cation exchange resin to remove the contaminants from the solution and to regenerate the fluoroboric acid in situ for use in continuous decontamination. providing a solution containing less than 50 milli-moles of fluoroboric acid per liter; contacting the fluoroboric acid solution with a material which causes the oxidation potential (Eh) of the solution to range from about 500 to about 1200 mV versus a Standard Calomel Electrode, wherein the material which causes the oxidation potential (Eh) of the solution to range from about 500 to 1200 mV is selected from the group consisting of hydrazine, hydrogen peroxide, ozone, potassium permanganate and combinations thereof; contacting the fluoroboric acid solution with the substrate; and, removing metal from the substrate by continuously contacting the fluoroboric acid solution with a cation exchange resin to remove the metal from the solution and to regenerate the fluoroboric acid in situ for use in continuous removal of metal. 2. A process according to claim 1 wherein pH of the fluoroboric acid solution ranges from about 2 to about 3. 3. A process according to claim 1 wherein the material which causes the oxidation potential (Eh) of the solution to range from about 500 to 1200 mV is potassium permanganate. 4. A process according to claim 3 wherein the concentration of the potassium permanganate in the solution is 10-100 ppm. 5. A process according to claim 1 further comprising maintaining the fluoroboric acid solution temperature from about 15.degree. C. to about 100.degree. C. 6. A process according to claim 1 wherein the contaminant is selected from the group consisting of radioactive metal and derivative of radioactive metal. 7. A process for removing metal from a substrate comprising: 8. A process according to claim 7 wherein pH of the solution ranges from about 2 to about 3. 9. A process according to claim 7 wherein the material which causes the oxidation potential (Eh) of the fluoroboric acid solution to range from about 500 to 1200 mV is potassium permanganate. 10. A process according to claim 9 wherein the concentration of the potassium permanganate in the solution is 10-100 ppm. 11. A process according to claim 7 further comprising maintaining the fluoroboric acid solution temperature from about 15.degree. C. to about 100.degree. C.
046541896
abstract
A medium power, high temperature pebble bed nuclear reactor, which includes a means for introduction and withdrawal of operating elements. The installation is provided in such a way that it can be more economically built and operated. The installation includes several input stations above a prestressed concrete pressure vessel, and charging hatch blocks positioned on top of the prestressed concrete pressure vessel. The blocks include selectors through which the pebble-shaped operating elements, after traversing helical and meandering charging conduits, reach into the reactor core. The selectors and charging conduits are installed within armored ducts which penetrate the prestressed concrete pressure vessel. Similar armored ducts are provided for exit ducts for withdrawal of pebbles from the core, and a first common exit hatch block is connected to the exit ducts. The block is arranged within foundation walls which support the prestressed concrete pressure vessel. A second exit hatch block, which is connected to the first exit hatch block by a shielded exit hatch channel, is provided in a reactor protection building. The withdrawal station is arranged in a reactor auxiliary building and connected to the shielded exit hatch channel.
058964312
summary
FIELD OF THE INVENTION This invention relates generally to nuclear reactors and, more particularly, to passive containment cooling systems for such reactors. BACKGROUND OF THE INVENTION One known boiling water nuclear reactor includes a drywell, or containment, a wetwell, a Gravity Driven Cooling System (GDCS) and a passive cooling containment system (PCCS). The drywell is designed to withstand pressure generated by a reactor pressure vessel (RPV) during reactor operation, and the PCCS is configured to limit the pressure within the containment to a pressure below a design pressure of the containment and to keep the RPV core substantially cool. The GDCS is substantially isolated from the drywell and is an emergency source of low pressure reactor coolant used following a loss of coolant event in at least one known boiling water reactor (BWR). A typical GDCS includes pools of coolant positioned so that when coolant from the pools must be supplied to the RPV, the coolant flows, under gravity forces, through the GDCS coolant delivery system into the RPV. Under normal reactor operating conditions, however, coolant from the GDCS does not flow into the RPV. A typical PCCS includes several condensers positioned in a PCCS pool of water. Each condenser includes an upper drum, a lower drum, and several heat exchanger tubes extending between the upper and lower drums. The upper drums are coupled to the drywell via a steam inlet passage, and steam generated within the containment flows from the upper drums and to the lower drums through the exchanger tubes. The steam is condensed into water and noncondensable gases, e.g., noncondensables, flow between the upper and lower drums. The condensed steam is drained from the lower drums and to the condensate drain tank via a condensate drain line. The noncondensables are drained from the lower drums utilizing vent lines which extend from each lower drum and into the wetwell suppression pool. Noncondensables are discharged from the lower drums and into the suppression pool, and rise through the suppression pool to the wetwell air space. The wetwell is separated from the containment by a wall having an opening therein. A vacuum breaker typically seals the opening and is movable between an open position and a closed position. The vacuum breaker is a check valve which allows the noncondensables and steam to pass from the wetwell to the drywell and substantially prevent a large differential pressure from developing between the wetwell and the drywell. Particularly, if pressure in the wetwell becomes sufficiently great compared to pressure in the drywell, the vacuum breaker opens and noncondensables and steam in the wetwell flow through the vacuum breaker and into the drywell to reduce the differential pressure. If the vacuum breaker becomes stuck in the open position, it is possible for the differential pressure between the wetwell and the drywell to reduce too much. Particularly, it is possible for steam in the drywell to bypass the PCCS steam inlet passage and flow directly into the wetwell via the vacuum breaker, which is undesirable. To prevent a vacuum breaker from sticking in the open position, it is known to utilize an isolation valve. However, isolation valves sometimes fail and thus cause the vacuum breaker to cease operating. In addition, isolation valves must often be monitored to ensure proper operation. It would be desirable to provide a system which substantially prevents steam and noncondensables from flowing from the drywell and into the wetwell while the vacuum breaker is in the open position. It further would be desirable for such system to facilitate the maintenance of an acceptable drywell to wetwell pressure differential. SUMMARY OF THE INVENTION These and other objects may be attained by a vacuum breaker condensing system which, in one embodiment, includes a condenser and a steam inlet pipe. The steam inlet pipe is substantially hollow and includes a first end, a second end, and a loop seal between the first and second ends. The first end of the pipe is positioned adjacent the drywell and the second end of the pipe is coupled to the vacuum breaker. The condenser is positioned proximate the steam inlet pipe and is configured to substantially condense steam flowing through the steam inlet pipe. The condenser includes an inlet, an outlet, and a plurality of condenser tubes. The condenser inlet and condenser outlet are each coupled to a pool of water, e.g., the Gravity Driven Cooling System pool, and configured to draw water from the pool of water and through the condenser tubes. In operation, and when the vacuum valve is stuck in the open position, steam and noncondensables flow from the drywell through the steam inlet pipe toward the vacuum breaker. The condenser substantially condenses the steam, and the condensate collects in the loop seal. The collected condensate substantially seals the steam inlet pipe and substantially prevents additional steam and noncondensables from flowing from the drywell toward the vacuum breaker. The above described system substantially prevents steam and noncondensables from flowing from the drywell and into the wetwell while the vacuum breaker is in the open position. Such system also facilitates maintaining an acceptable drywell to wetwell pressure differential.
059321784
claims
1. An FDG synthesizer, which comprises: a labeling reaction resin column in which (i) target water containing fluoride ion and (ii) a triflate solution are passed through said labeling reaction resin column, said labeling reaction resin column comprising a column filled with a polymer-supporter phase-transfer catalyst resin, for trapping the fluoride ion contained in the target water, and wherein a labeling reaction is performed between the thus trapped fluoride ion and the triflate, and a hydrolysis reaction vessel for receiving a reaction intermediate product obtained from the labeling reaction, and wherein a hydrolysis reaction is performed by the addition of a strong acidic aqueous solution or a strong alkaline aqueous solution. said polymer-supported phase-transfer catalyst resin comprises a phosphonium salt fixed to a polystyrene resin. a labeling reaction resin column in which (i) target water containing fluoride ion and (ii) a triflate solution are passed through said labeling reaction resin column, said labeling reaction resin column comprising a column filed with a polymer-supporter phase-transfer catalyst resin for trapping the fluoride ion contained in the target water, and wherein a labeling reaction is performed between the thus trapped fluoride ion and the triflate, and a cation-exchange resin column for receiving a reaction intermediate product obtained from the labeling reaction, and wherein a hydrolysis reaction is performed by bringing the reaction intermediate product into contact with a cation-exchange resin adjusted to an H.sup.+ cation-exchange resin in the cation-exchange resin column. the cation-exchange resin column has a heating means and a flow rate control means for controlling the flow of said reaction intermediate product which contains an organic solvent, and in said cation-exchange resin column, said reaction intermediate product containing said organic solvent obtained from said labeling reaction is heated, to evaporation-eliminate said organic solvent by the heating means in the cation-exchange resin column, and at the same time, said reaction intermediate product after the elimination of said organic solvent is brought into contact with the cation-exchange resin adjusted to an H.sup.+ cation-exchange resin in the cation-exchange resin column to perform said hydrolysis reaction. (a) a cartridge labeling reaction resin column, (b) a cartridge cation-exchange resin column, and (c) a disposable cartridge base into which passageways and switchover valves for communicating said labeling reaction resin column with said cation-exchange resin column, are incorporated; in said cartridge labeling reaction resin column (i) target water containing fluoride ion and (ii) a triflate solution are passed through, said cartridge labeling reaction resin column comprising a disposable column filled with a polymer-supported phase-transfer catalyst resin, said cartridge labeling reaction resin column being one-touch-releasably attachable to said disposable cartridge base, for trapping the fluoride ions contained in the target water, and wherein a labeling reaction between the thus trapped fluoride ion and the triflate take place; and said cartridge cation-exchange resin column comprising a disposable column filled with a cation-exchange resin adjusted to an H.sup.+ cation-exchange resin, said cartridge cation-exchange resin column being one-tough-releasably attachable to said disposable cartridge base, and wherein a reaction intermediate product obtained from said labeling reaction is brought into contact with said cation-exchange resin adjusted to said H.sup.+ cation-exchange resin in said cation-exchange resin column to perform a hydrolysis reaction. each of said switchover valves includes a three-way cock therein. 2. The FDG synthesizer as claimed in claim 1, wherein: 3. An FDG synthesizer, which comprises: 4. The FDG synthesizer as claimed in claim 3, wherein: 5. The FDG synthesizer as claimed in claim 4, wherein the heating means for the cation-exchange resin column heats the cation-exchange resin column from 90 to 150.degree. C., and wherein the flow rate control means controls the flow of the reaction intermediate product from 0.5 to 1.5 cc/minute. 6. An FDG synthesizer, which comprises: 7. The FDG synthesizer as claimed in claim 6, wherein: 8. The FDG synthesizer as claimed in claim 6, wherein the synthesizer body comprises a means for driving the switchover valves and a means for heating the cartridge labeling reaction resin column and the cartridge cation-exchange resin column. 9. The FDG synthesizer as claimed in claim 6, wherein the passageways comprise a teflon tube. 10. The FDG synthesizer as claimed in claim 6, wherein the passageways comprise a polypropylene tube.
063174839
claims
1. An optically curved device comprising: a plurality of curved atomic planes, at least some curved atomic planes being separated by a spacing d which varies in at least one direction; an optical surface disposed over said plurality of curved atomic planes, said optical surface being doubly curved; and wherein said spacing d varies in at least one direction and is determined from a Bragg equation, where a Bragg angle is an incident angle of an x-ray from a source impinging on said optical surface on each of at least some points of said optical surface. 2. The optically curved device of claim 1, wherein said spacing d varies in said at least one direction to achieve maximum reflectivity of x-rays from said divergent source. 3. The optically curved device of claim 1, wherein said doubly curved optical surface comprises one of an elliptic, parabolic, spheric or aspheric profile. 4. The optically curved device of claim 3, wherein said doubly curved optical surface comprises an elliptical profile and said optically curved device provides point to point focusing of x-rays. 5. The optically curved device of claim 3, wherein said doubly curved optical surface comprises a parabolic profile and said optically curved device provides collimation of x-rays from a point source. 6. The optically curved device of claim 3, wherein said doubly curved optical surface comprises a spherical profile and said optically curved device provides imaging of x-rays. 7. The optically curved device of claim 3, wherein said doubly curved optical surface has a profile adapted for at least one of point to point focusing, directing a divergent x-ray beam from a point source to a collimated beam, directing an x-ray beam from a point source to an x-ray beam with a different divergence angle, or imaging of x-rays. 8. The optically curved device of claim 1, wherein said optically curved device comprises an SiGe crystal, and wherein a ratio of silicon to germanium in said at least some curved atomic planes separated by said varying spacing d varies across said optically curved device. 9. The optically curved device of claim 1, wherein said optically curved device comprises at least a first crystal piece and a second crystal piece, wherein each crystal piece includes said plurality of curved atomic planes and said optical surface disposed thereover. 10. The optically curved device of claim 9, wherein said first crystal piece and said second crystal piece are disposed symmetrical about a center axis of said optically curved device. 11. The optically curved device of claim 9, wherein said first crystal piece comprises a first spherical optic and second crystal piece comprises a second spherical optic, wherein said first spherical optic and said second spherical optic are configured as Schwarzschild optics, and wherein said optically curved device provides demagnification of x-rays from said divergent source. 12. The optically curved device of claim 1, wherein said spacing d varies in two dimensions for matching of incident angles of x-rays from said divergent source impinging on said optical surface with a Bragg angle on each of a plurality of points disposed across said optical surface. 13. The optically curved device of claim 12, wherein said plurality of points are disposed in a radial distribution across said optical surface.
summary
claims
1. A method for forming a palladium sulfide film on a substrate, the method comprising:applying a palladium sulfide precursor to the substrate, wherein the palladium sulfide precursor comprises a palladium organothiolate; andheating the palladium sulfide precursor in an atmosphere to decompose the palladium sulfide precursor to form the palladium sulfide film, where the atmosphere includes hydrogen or a sulfur-containing gas. 2. The method of claim 1, wherein the palladium sulfide precursor has the formula Pd(SR)2, wherein R is a hydrocarbon group having from about 4 to about 20 carbon atoms and wherein R and is selected from the group consisting of an alkyl group, an alkenyl group and an aromatic group. 3. The method of claim 2, wherein R is an alkyl group having from 8 to 16 carbon atoms. 4. The method of claim 2, wherein the palladium sulfide precursor is selected from the group consisting of palladium octanethiolate and palladium hexadecylthiolate. 5. The method of claim 1, further comprising applying the palladium sulfide precursor by:dissolving a solution of the palladium sulfide precursor in a solvent to produce a solution;applying the solution to the substrate; andevaporating the solvent to produce a dry film. 6. The method of claim 5, further comprising spinning the substrate to distribute the solution across the substrate. 7. The method of claim 5, further comprising dissolving the solution in a solvent selected from the group consisting of ethanol and toluene. 8. The method of claim 1, further comprising applying the palladium sulfide precursor to a substrate fabricated from a material selected from the group consisting of silicon, glass, silica, alumina, metal, ceramic and polymer. 9. The method of claim 1, further comprising applying the palladium sulfide precursor to a flexible substrate. 10. The method of claim 1, further comprising applying the palladium sulfide precursor to a curved substrate. 11. The method of claim 1, further comprising patterning the palladium sulfide precursor. 12. The method of claim 11, further comprising patterning the palladium sulfide precursor by electron beam patterning. 13. The method of claim 11, further comprising patterning the palladium sulfide precursor by at least one of micromolding the precursor in capillaries, offset printing, inkjet printing, or silkscreen printing. 14. The method of claim 1, further comprising heating the palladium sulfide precursor in an atmosphere of flowing hydrogen in a reaction chamber and wherein the reaction conditions include a temperature of from about 180 degrees C. to about 300 degrees C. and a reaction time of from about 100 minutes to about 200 minutes, and the palladium sulfide film comprises single phase, crystalline Pd4S. 15. The method of claim 1, further comprising heating the palladium sulfide precursor in an atmosphere of flowing sulfur-containing gas in a reaction chamber and wherein the reaction conditions include a temperature of from about 180 degrees C. to about 300 degrees C. and a reaction time of from about 100 minutes to about 200 minutes, and the palladium sulfide comprises PdS. 16. The method of claim 1, further comprising, prior to applying the palladium sulfide precursor, coating the substrate with a gold layer. 17. The method of claim 16, further comprising patterning the palladium sulfide precursor. 18. The method of claim 17, further comprising etching at least some of the gold layer. 19. The method of claim 18, further comprising depositing a metal on the palladium sulfide film. 20. The method of claim 19, wherein the metal is selected from the group consisting of gold, silver and copper. 21. A method for forming a crystalline, single phase, electrically conductive Pd4S film on a substrate, the method comprising:applying a palladium alkanethiolate to a substrate;patterning the palladium alkanethiolate to form a patterned precursor, andheating the patterned precursor with hydrogen in a reaction chamber at a temperature of from about 180 degrees C. to about 300 degrees C., and for about 100 minutes to about 200 minutes, to form the Pd4S film on the substrate. 22. The method of claim 21, further comprising patterning the palladium alkanethiolate by at least one of micromolding the palladium alkanethiolate in capillaries, offset printing, inkjet printing, or silkscreen printing. 23. A method for forming a palladium sulfide film on a substrate, the method comprising:applying a palladium sulfide precursor to the substrate, wherein the palladium sulfide precursor comprises a palladium organothiolate; andheating the palladium sulfide precursor in an atmosphere of flowing argon in a reaction chamber and the palladium sulfide comprises Pd16S7. 24. The method of claim 23, wherein the conditions in the reaction chamber include a temperature of from about 180 degrees C. to about 300 degrees C. and a reaction time of from about 100 minutes to about 200 minutes. 25. A method for forming a palladium sulfide film on a substrate, the method comprising:applying a palladium sulfide precursor to the substrate, wherein the palladium sulfide precursor comprises a palladium organothiolate; andheating the palladium sulfide precursor to decompose the palladium sulfide precursor to form Pd4S. 26. The method of claim 25, wherein the Pd4S is a single phase, crystalline Pd4S.
052157075
description
DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, a thimble tube shroud 1 is disposed in a nozzle 2 of a nuclear fuel assembly (not shown). Typically, a pressurized water reactor has a number of fuel assemblies which form a core. Each fuel assembly has a flow distribution plate 3 spaced from a reactor lower support plate 4. The support plate 4 has openings 5 through which the reactor coolant flows. The flow distribution plate assists in a assuring uniform fluid flow about each fuel rod in the assembly to provide efficient cooling. The 10 shroud 1 has a cup portion 6 with a tapered end 7 and arms 8 which extend to support the shroud. Referring to FIG. 2, the cup 6 is disposed between the flow distribution plate 3 and the support plate 4. An instrument thimble tube 9 extends through an opening 10 in the support plate, passing through a hole 11 in a top surface 12 of the cup, and through an opening 13 in the flow distribution plate, into a thimble guide tube 14. The cup has a cylindrical shape and has an inner diametrical opening 15 sufficient to pass the instrument tube therethrough. Sufficient clearance is also provided to allow liquid flow around the instrument tube. For example, the cup may have an inner diametrical opening 15 of about 1.5 inches, with a clearance between the thimble tube 9 and hole 11 of about 0.071 inches. The cup isolates the thimble tube passing through the openings to prevent excessive wear due to vibratory contact with the adjacent surfaces due to the intensity of the fluid flowing through the fuel assembly. The cup allows flow through and about the instrument thimble tube 9 in a controlled fashion, using passages 16 in the tapered end 7. The arrows A illustrate the flow separation within the cup with part of the flow directed out of the passages 16 and part directed through the hole 11 into the guide tube 14. The cup isolates the instrument tube from cross flow in the spacing between the distribution plate 3 and support plate 4. Consequently, fluid flow is maintained within the guide tube 14 yet is moderated by the passages 16 to a degree which minimizes vibration and potential damage of the instrument thimble tube. Referring again to FIG. 1, cup 6 has four arms 8 which extend radially. The arms maintain the shroud in an axial orientation and prevent rotation or twisting which could cause the shroud to move and itself damage the instrument thimble tube. Each arm 8 has a locking pad 17 which engages complimentary structures in the nozzle 2. Referring to FIGS. 3, 4, and 5 a-c, each locking pad 17 has a spacing lip 18 and incorporates a spring plate 19, which is attached preferably by bolting or welding to the pad. Each spring plate 19 has a pair of spring arms 21 which have sloped surfaces 22 and 23 to ease entry and exit into the nozzle. These spring arms mate with recesses 20 in the nozzle 2, and bias the shroud into maintaining it's engagement with the recess. Referring to FIGS. 3 and 5a-5c, a separate retaining spring 25 locks the pad in it's engaged position. The retaining spring 25 has an angle surface 26 leading to an angled tab 27. As the angle surface 26 engages a shoulder 24 of the bottom nozzle 2, it causes the angled surface 26 to be deflected as the shroud is inserted in nozzle 2. Once the spring arms 21 seat in their respective recesses 20, the angle tabs 27 contact shoulders 24 and prevent the shroud from being withdrawn. Before the shroud can be removed, the retaining spring 25 must be released. FIG. 6a shows the spring 25 in a relaxed condition prior to mounting, FIG. 6b shows the springs at maximum deflection, traveling across a shoulder 24 in the nozzle 2. The shroud is preferably made of a material compatible with nuclear reactor service. For example, the shroud may be composed stainless steel, zirconium, or a zirconium alloy such as Zircaloy-2 or -4. The springs may be made of the same materials or of a nickel alloy material such as Inconel. In addition, the number and types of spring means and/or arms may vary depending on the location of the shroud within the fuel assembly. Utilizing the thimble tube shroud of the present invention, having arms and spring pads, prevents rotation or shifting of the shroud and prevents damage to the instrument thimble tube. Also, the shroud reduces and redirects flow around the instrument thimble tube without detrimentally affecting cooling or flow of the coolant about the instrument thimble tube. Consequently, the inventive shroud prevents vibration damage to the instrument thimble tube passing therethrough, enhancing life of the instrumentation and allowing continued observation of dynamics within the nuclear reactor. While preferred embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes and modifications could be made without varying from the scope of the present invention.
047643382
claims
1. In the method of controlling the dissolution of radioactive corrosion products deposited on the surface of fuel rods into the core water of a boiling water-type atomic power plant including a nuclear reactor having a recycling system with a reactor water-purifying unit, a turbine generator driven by steam generated in the nuclear reactor, a condensor, a condensed water-purifying unit, and a water heater positioned in the recycling system; wherein the improvement comprises, passing the reactor water of the recycling system through the reactor water-purifying unit containing a cation exchange resin, wherein a portion of said cation exchange resin had been previously replaced with an alkali metal-form cation exchange resin, and passing the condensed water of the recycling system through a condensed water-purifying unit containing a cation exchange resin, wherein a portion of said cation exchange resin had been previously replaced with an alkali metal-form cation exchange resin, so as to cause the pH of the reactor water and condensed water to be adjusted to a pH of between about 7.0 and 8.5 through the ion exchange reaction of the alkali metal-form cation exchange resins with the cations contained in the reactor water and the condensor water of the recycling system whereby the dissolution of radioactive corrosion products deposited on the surface of the fuel rods into the core water of a boiling water-type atomic power plant is controlled. 2. The method of claim 1 wherein said pH is maintained between 7.5 and 8.0. 3. The method of claim 1 wherein said radioactive corrosion product is cobalt ferrite. 4. The method of claim 1 wherein said radioactive corrosion product is nickel ferrite. 5. The method of claim 1 wherein said alkali-form cation exchange resins is a Na-form cation exchange resin. 6. The method of claim 1 wherein the reactor water-purifying unit and the condensed water-purifying unit contain a mixture of cation exchange resin and anion exchange resin with said cation exchange resin being in excess of said anion exchange resin, wherein said excess portion of the cation exchange resin is regenerated together with the anion exchange resin with an alkali, thereby converting the excess portion of the cation exchange resin into an alkali-form cation exchange resin. 7. The method of claim 6 wherein said alkali-form cation exchange resin is a Na-form cation exchange resin. 8. The method according to claim 7 wherein the ratio of the Na-form cation exchange resin produced to the total cation exchange resin is 0.1 to 0.5. 9. The method of claim 7 wherein said Na-form cation exchange resin has the formula R--(SO.sub.3 Na).sub.2.
061608637
claims
1. A volume control system for a nuclear reactor comprising: a primary coolant circuit for cooling a nuclear reactor, said primary coolant circuit including a pressurizer connected thereto; a secondary coolant circuit connected to said primary coolant circuit comprising: a pressurizer level control system connected to each of said first and second variable speed charging pumps to independently control the speed of each of said first and second charging pumps in accordance with a level of coolant in the pressurizer. 2. The volume control system of claim 1, wherein said pressurizer level control system includes a processor for monitoring and controlling the level of pressure and flow rates in the volume control system. 3. The volume control system of claim 1, wherein said variable speed drive is an AC variable speed drive, said power supply is an AC power supply bus and said motor is a synchronous AC motor. 4. The volume control system of claim 1, wherein a rate of charging flow into said primary coolant circuit is approximately the same as the rate of letdown flow.
description
The present application is related in general subject matter to the following application, which is being filed concurrently with the present application, and is hereby incorporated by reference into the present application in its entirety, U.S. application Ser. No. 12/056,738, filed Mar. 27, 2008. The present teachings relate to systems and methods for securely connecting, or interlocking, two pole sections together such that they do not disconnect during use. The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. Various industries incorporate the use of long poles to perform various operational, manufacturing, organizational, inspection and maintenance tasks. For convenience and flexibility, such poles are often constructed, or assembled, by connecting various length pole sections together to provide a pole of a specific length. Additionally, a tool or some other instrument or device is often connected to an end of the assembled pole to perform a desired task. In many instances the interconnection of the pole sections, and the interconnection of the tool and respective pole section, can incur substantial stress, vibration, shaking and/or rotational torque during use. Accordingly, it can be important that the interconnections be very secure to prevent loosening and/or separating of the sections and/or tool during use. For example, high torque, sectional handling poles are often used by nuclear reactor service technicians to manipulate tools utilized for performing various service, inspection and repair tasks inside the reactor vessel. Frequently, during manipulation of the pole and tool within the reactor vessel, particularly when the technician applies a rotational torque to the pole, one or more coupling assemblies used to connect the pole sections and tool together loosen and often separate. When such separation of the pole sections and/or tool occur, the activities must be interrupted until the section or tool is retrieved. In various embodiments, a system for interlocking a first pole section to a second pole section are provided, wherein the system includes a tubular female end portion of the first pole section and a male end portion of the second pole section that is insertable into the female end portion. The system additionally includes a locking nut threadingly engaged with the male end portion that is rotatable on the male end portion to longitudinally transition the locking nut into contact with the female end portion to fixedly interlock the male and female end portions. Furthermore, the system includes a biased locking sleeve assembly slidably and rotatably mounted on a locking assembly portion of the second pole. The locking sleeve assembly can include a locking sleeve and a biased plunger slidingly positioned within an interior of the locking sleeve for applying a locking force to the locking nut. In various other embodiments, a system for interlocking a first pole section to a second pole section is provided, wherein the system includes a tubular female end portion of the first pole section. The tubular female end portion includes a pair of opposing substantially J-shaped connecting slots. Each connecting slot includes a backbone section open at a distal end of the female end portion. The system additionally includes a male end portion of the second pole section having a connecting pin extending therethrough. The male end portion can be inserted into the female end portion such that opposing ends of the connecting pin are inserted into the backbone sections of the connecting slots and can be radially transitioned to a hook section of the respective connecting slots. The system further includes a locking nut threadingly engaged with the male end portion at a proximal end of the male end portion. The locking nut can be rotated to longitudinally transition the locking nut into contact with the female end portion such that the connecting pin ends are moved into the hook sections of the connecting slots to fixedly interlock the male end portion with the female end portion. The system can still further includes a locking sleeve retaining pin extending through a locking sleeve assembly portion of the second pole between the locking nut and a proximal end of the locking sleeve assembly portion. Further yet, the system can include a biased locking sleeve assembly that is slidably and rotatably mounted on the locking sleeve assembly portion between the locking nut and the locking sleeve retaining pin. In various embodiments, the locking sleeve assembly can include a locking sleeve having a collar portion and neck portion, a plunger slidingly positioned within an interior of the collar portion, and a biasing device located within the interior of the collar portion, between the neck portion and the plunger, for forcing the plunger against the locking nut. In yet other embodiments, a method for coupling a first pole section to a second pole section is provided, wherein the method includes inserting a tubular female end portion of the first pole section over a male end portion of the second pole section such that opposing ends of a connecting pin extending through the male end portion are inserted into backbone sections of opposing J-shaped connecting slots formed in the female end portion. Additionally, the method can include rotating at least one the male and female end portion relative to each other to radially transition the connecting pin ends to hook sections of the respective connecting slots. Furthermore, the method can include rotating a locking nut threadingly engaged with the male end portion at a proximal end of the male end portion to longitudinally transition the locking nut into contact with the female end portion, thereby moving the connecting pin ends into the hook sections to fixedly interlock the male end portion with the female end portion. Still further, the method can include longitudinally transitioning a biased locking sleeve assembly mounted on a locking sleeve assembly portion of the second pole toward the locking nut such that a biased plunger of the locking sleeve assembly exerts a locking force on the locking nut sufficient to prevent or considerably inhibit rotation of the locking nut and separation of the locking nut and female end portion. Further yet, the method can include rotating a locking sleeve of the locking sleeve assembly to engage a pair of locking slots radially located within an interior surface of a distal end portion of a neck portion of the locking sleeve with a locking sleeve retaining pin extending through the locking sleeve assembly portion, thereby locking the locking sleeve assembly in a ‘Locked’ position where the locking force exerted by the biased plunger is maintained on the locking nut. Further areas of applicability of the present teachings will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present teachings. The following description is merely exemplary in nature and is in no way intended to limit the present teachings, application, or uses. Throughout this specification, like reference numerals will be used to refer to like elements. Referring to FIGS. 1 and 1A, an exemplary illustration of a sectional handling pole 10 is provided. The handling pole 10 can be implemented to perform various operational, manufacturing, organizational, inspection and maintenance tasks where it is inconvenient or unfeasible for the task to be performed by a person in close proximity to the equipment, system, apparatus, device, component, etc., on which the task is to be preformed. For example, in various embodiments, the sectional handling pole 10 can be utilized by nuclear reactor service technicians to manipulate tools used for performing various service, inspection and repair tasks inside the reactor vessel. Generally, the handling pole 10 includes a first pole section 14 coupled together with a second pole section 18 utilizing a coupling system 22. The first and second pole sections 14 and 18 are generally the same in that they each comprise the same parts, components and structure, as described below. However, the first and second pole sections 14 and 18 are merely exemplary illustrations of two of a plurality of substantially similar pole sections that can be coupled together to construct, or assemble, the handling pole 10. That is, it should be understood that the first and second pole sections 14 and 18 can be of the same or different lengths, and that the handling pole 10 can comprise more pole sections than the first and second pole sections 14 and 18 exemplarily illustrated. Thus, the handling pole 10 can be constructed, or assembled, to have any desired length by coupling together two or more pole sections of desired lengths, e.g., first and second pole sections 14 and 18, using the coupling system 22, as described herein. Referring now to FIGS. 1, 1A and 2, in various embodiments, the coupling system 22 includes a tubular female end portion 26 of the first pole section 14 and a male end portion 30 of the second pole section 18. An inner diameter of the tubular female end portion 26 is sized to be substantially equal to an outer diameter of the male end portion 30. Therefore, the male end portion 30 can be inserted into the female end portion 26 with very little play, slop, gap or space between male end portion outer diameter and the female end portion inner diameter. Accordingly, the male end portion 30 fits snuggly within the female end portion 26 such that the first and second pole sections 14 and 18 become a substantially steady, or stable, extension of each other. Additionally, in various forms, the coupling system 22 includes a locking nut 34 threadingly engaged with threads 38 formed on the male end portion 30. The locking nut 34 can be rotatated about the male end portion 30 to longitudinally transition the locking nut 34 along an axis A of the male end portion 30 in the X+ and X− directions. For instance, once the male end portion 30 is inserted into the female end portion 36, the locking nut 34 can be rotated to longitudinally transition the locking nut 34 in the X− direction and into contact with the female end portion 26 (as shown in FIG. 4A) to fixedly couple the male end portion 30 with the female end portion 26. More particularly, in various embodiments, the male end portion 30 includes a connecting pin 42 that extends laterally through male end portion 30 between the threads 38 and a distal end 46 of the male end portion 30. Additionally, the female end portion 26 includes a pair of opposing substantially J-shaped connecting slots 50. As best shown in FIG. 1A, each of the J-shaped connecting slots 50 includes a backbone section 54 that is open at a distal end 58 of the female end portion 26, a hook section 62 and a bottom section 66 that connects the backbone section 54 with the hook section 62. In such embodiments, when the male end portion 30 is inserted into the female end portion 26, opposing ends 42A and 42B are inserted into the backbone section 54 of a respective J-shaped connecting slot 50. The first pole section 14 and/or the second pole section 18 can then be rotated relative to the other to transition the connecting pin ends 42A and 42B from the backbone sections 54 to the hook sections 62, via the bottom sections 66. The locking nut 34 can then be rotated about the threads 38 to longitudinally transition, or move, the locking nut 34 in the X− direction and into contact with the distal end 58 of the female end portion 26. Further rotation of the locking nut 34 will move the female end portion 26 in the X− direction drawing the locking pin ends 42A and 42B into the hook sections 62 until the locking pin ends 42A and 42B are drawn firmly and tightly into distal ends 70 of the hook sections 62. When the locking pin ends 42A and 42B are drawn firmly and tightly into distal ends 70 of the hook sections 62, the female and male end portions 26 and 30, and more particularly, the first and second pole sections 14 and 18, are fixedly coupled, or interlocked, together. Referring to FIGS. 2 and 3, in various embodiments, the coupling system 22 further includes a biased locking sleeve assembly 74 (best shown in FIG. 2) that is slidably and rotatably mounted on a locking assembly portion 78 of the second pole 18. In various implementations, the locking sleeve assembly 74 includes a locking sleeve 82 having a collar portion 86 and neck portion 90, a plunger 94 slidingly positioned within an interior of the locking sleeve collar portion 86, and a biasing device 98 located within the interior of the collar portion 86, between the neck portion 90 and the plunger 94. Although illustrated as a spring, the basing device 98 can be any biasing device such as a spring, resilient bushing or any other device suitable for exerting a force on the plunger in the X− direction to force the plunger 94 against the locking nut 34. Referring now to FIGS. 2, 3, 4A and 4B, as described in detail below, the locking sleeve 82 includes a plurality of locking slots 102 and a pair of retraction slots 106 formed along an interior surface of the locking sleeve neck portion 90. The locking slots 102 and retraction slots 106 are structured to engage a locking sleeve retaining pin 110 extending through the locking sleeve assembly portion 78 between the locking nut 34 and a proximal end 114 of the locking sleeve assembly portion 78. Particularly, the locking sleeve assembly 74 is operable such that opposing ends 110A and 110B of the locking sleeve retaining pin 110 are engaged with an opposing pair of the locking slots 102 to place the locking sleeve assembly 74 in a ‘Locked’ position (FIG. 4A) and engaged with the retraction slots 106 to place the locking sleeve assembly 74 in an ‘Unlocked’ position (FIG. 4B). More particularly, as best shown in FIG. 3, the locking slots 102 comprise short slots radially located within an interior surface of a distal end portion 118 of the locking sleeve neck portion 90. The locking slots 102 are sized to receive the ends 110A and 110B of the locking sleeve retaining pin 110 and have a length L sufficient to securely retain the locking sleeve retaining pin ends 110A and 110B when the biasing force of the biasing device 98 is exerted on the locking sleeve 82 in the X+ direction. To place the locking sleeve 82 in the ‘Locked’ position, once the locking nut 34 has been rotatingly transitioned in the X− direction to securely couple the first and second pole sections 14 and 18 together, as described above, a force is applied to the locking sleeve 82 in the X− direction sufficient to overcome the biasing force of the biasing device 98, thereby longitudinally transitioning the locking sleeve 82 in the X− direction. Specifically, force is applied, e.g., hand applied force, to the locking sleeve 82 sufficient to transition the locking sleeve 82 in the X− direction a sufficient distance to disengage, i.e., separate, the locking sleeve retaining pin ends 110A and 110B from the distal end portion 118 of the locking sleeve neck portion 90. More particularly, the locking sleeve 82 is transitioned in the X− direction a sufficient distance to disengage the locking sleeve retaining pin ends 110A and 110B from the retraction slots 106. The locking sleeve 82 can then be rotated about the second pole locking sleeve assembly portion 78 to align the locking sleeve retaining pin ends 110A and 110B with any opposing set of locking slots 102. Once the locking sleeve retaining pin ends 110A and 110B are aligned with a set of opposing locking slots 102, the force being applied to locking sleeve 82 in the X− direction can be removed, such that force exerted by the biasing device 98 will move the locking sleeve 82 in the X+ direction and force the locking sleeve retaining pin ends 110A and 110B into contact with bottom surfaces 102A of the respective opposing locking slots 102. Once the locking sleeve retaining pin ends 110A and 110B contact the bottom surfaces 102A, the locking sleeve 82 is prevented from moving further in the X+ direction, thereby securely engaging the locking sleeve retaining pin ends 110A and 110B within the locking slots 102, thereby placing the locking sleeve 82 in the ‘Locked’ position. When in the ‘Locked’ position, the biasing device 98 is compressed to exert a locking load, or force, on the plunger 94 that, in turn, exerts the locking load, or force, on the locking nut 34. More particularly, the biasing device 98 is structured to provide a locking load, or force, sufficient to prevent or considerably inhibit rotation of the locking nut 34 and any resulting separation of the locking nut 34 from the female end portion 26. For example, in various embodiments, the biasing device 98 is structured to exert between approximately 30 and 50 lbs/in of force on the locking nut 34, e.g., approximately 40 lbs/in, when the locking sleeve 82 is in the ‘Locked’ position. Additionally, as described below, the resulting gap ‘D’ between the locking sleeve 82 and the locking nut 34 is less than a distance needed to disengage the connecting pin 42 from the J-shaped connections slots 50, thereby further preventing the possibility of the first and second pole sections 14 and 18 separating. With further reference to FIG. 3, the retraction slots 106 comprise a pair of opposing slots located within the interior surface of the distal end portion 118 of the locking sleeve neck portion 90. As with the locking slots 102, the retraction slots 106 are also sized to receive the ends 110A and 110B of the locking sleeve retaining pin 110. Additionally, the retraction slots 106 have a length M that is considerably longer in the axial direction than the length L of the locking slots 102. The length M of the retraction slots 106 is sufficient to allow the locking sleeve 82 to be transitioned in the X+ direction a distance sufficient to remove the locking force applied to the locking nut 34 by the plunger 94 and biasing device 98. Particularly, removing the locking force allows the locking sleeve 82 to longitudinally transition in the X+ direction a sufficient distance from the locking nut 34 to allow the locking nut 34 to be unthreaded, i.e., rotated to longitudinally transition in the X+ direction, to allow the connecting pin 42 to be removed from the connecting slots 50 and the male end portion 30 separated from the female end portion 26. It should be understood that when the locking sleeve 82 is placed in the ‘Unlocked’ position the force applied on the locking nut 34 by the plunger 94 and biasing device 98 may or may not be completely removed. However, during unthreading of the locking nut 34, the spring may be slightly compressed to exert some force. However, this force will be considerably less than the locking force and is easily overcome. Therefore, the locking nut 34 can be rotated to transition the locking nut 34 in the X+ direction, thereby allowing the connection pin ends 42A and 42B to be removed from the respective J-shaped slots 50 such that the male and female end portions 30 and 26 can be separated. Thus, to place the locking sleeve 82 in the ‘Unlocked’ position, a force is applied to the locking sleeve 82 in the X− direction sufficient to overcome the locking force being exerted by the biasing device 98. The locking sleeve 82 is then longitudinally transitioned in the X− direction a sufficient distance to disengage the locking sleeve retaining pin ends 110A and 110B from the locking slots 102. The locking sleeve 82 can then be rotated about the locking sleeve portion of the second pole to align the retraction slots 106 with the locking sleeve retaining pin ends 110A and 110B. Once the retraction slots 106 are aligned with the locking sleeve retaining pin ends 110A and 110B, the force of the biasing device 98 can be allowed to transition the locking sleeve 82 in the X+ direction a distance substantially equal to the length M of the retraction slots 106, thereby placing the locking sleeve 82 in the ‘Unlocked’ position. As described above, when the locking assembly 74 is in the ‘Unlocked’ position, the locking force applied by the plunger 94 and compressed biasing device 98 is removed. Once the locking force is removed, the locking nut 34 can be rotated and longitudinally transitioned in the X+ direction a distance sufficient to allow the connection pin ends 42A and 42B to be removed from the respective J-shaped slots 50 and the first pole section 14 separated from the second pole section 18. As illustrated in FIG. 3, the length M of the retraction slots 106 is significantly longer than the length L of the locking slots 102. In various embodiments, the length M of the retraction slots 106 is approximately 5 to 25 times longer than the length L of the locking slots 102, e.g., 15 times longer than the length L of the locking slots 102. For example, in various configurations, the length L of the locking slots 102 can be approximately 1/16th of an inch and the length M of the retraction slots 106 can be approximately 1 to 2 inches. Referring particularly to FIG. 4A, as described above, in various embodiments the length L of the locking slots 102 are sized to position a distal end 122 of the locking sleeve collar portion 86 a particular distance D from the locking nut 34 when the locking sleeve assembly 74 is in the ‘Locked’ position. More specifically, the distance D is specifically sized such that, should the locking nut 34 back-off during use of the sectional handling pole 10, the locking nut 34 will only be allowed to longitudinally transition in the X+ direction the specific distance D. Still more particularly, the distance D is calculated such that should the locking nut 34 back-off the distance D, the locking nut 34 will abut the distal end 122 of the locking sleeve collar portion 86, thereby preventing the locking nut 34 from longitudinally transitioning a distance in the X+ direction sufficient to allow the connecting pin ends 42A and 42B to move out of the hook sections 62 of the J-shaped slots 50. Therefore, once the locking sleeve assembly 74 is placed in the ‘Locked’ position, should the locking nut 34 back-off during use of the sectional handling pole 10, separation of the male and female end portions 30 and 26 will be prevented because the locking nut 34 is only allowed to move the distance D in the X+ direction. The distance D is insufficient to allow the connecting pin ends 42A and 42B to disengage with the J-shaped slots 50. For example, in various embodiments, disengagement of the connecting pin ends 42A and 42B from the J-shaped slots 50 can require approximately ¼ of an inch travel in the X− directions, and the distance D can be approximately 1/10th of an inch to ⅛th of an inch. Referring now to FIG. 5, in various embodiments, the coupling system 22 additionally includes a protection sleeve 126 mounted on the locking sleeve assembly portion 78. The protection sleeve 126 includes a body 130 for mounting the protection sleeve 126 on the locking sleeve assembly portion 78, and a protective hood 134 that extends over the locking sleeve retaining pin ends 110A and 110B. Thus, the protective hood 134 covers the locking sleeve retaining pin ends 110A and 110B protecting them from damage. Additionally, the protective hood 134 is sized to receive the locking sleeve neck portion 90 and cover at least the distal end portion 118 of the locking sleeve neck portion 90. Therefore, the protective hood 134 covers and protects the locking slots 102 and retraction slots 106. In various embodiments wherein the protective hood 134 covers and protects the locking slots 102 and retraction slots 106, the neck portion 90 of the locking sleeve 82 includes an alignment indicator 138 on an exterior surface of the neck portion 90. The alignment indicator 138 can by any indicator suitable to indicate the location of the retraction slots 106 formed in the interior surface of the neck portion 90. For example, in various embodiments the alignment indicator can be a colored mark and embossed arrow, a recessed line or any other suitable indicator. Referring now to FIG. 6, it should be understood that although the coupling system 22 has been described herein as being structured and operable to connect two or more pole sections, e.g., the first and second pole sections 14 and 18, the couple system 22 can further be implemented to connect a tool 142 to any pole section. More particularly, the tool 142 can be connected to a tubular female end portion 26A that is identical in form, structure and function as the tubular female end portion 26 described above. Accordingly, the tool 142 can be coupled to the male end portion 30 of any pole section utilizing the coupling system 22 as described above with regard to the first and second pole sections 14 and 18. The tool 142 can be any tool, instrument or device for performing a desired task utilizing the handling pole 10 having poles sections coupled together and/or tools coupled to a pole section utilizing the coupling system 22 described herein. It will be understood that, although the terms first, second, third, etc., may be used herein to describe various elements, components and/or sections, these elements, components and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component or section from another element, component or section. Thus, a first element, component or section discussed below could be termed a second element, component or section without departing from the teachings of the example embodiments. The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The description herein is merely exemplary in nature and, thus, variations that do not depart from the gist of that which is described are intended to be within the scope of the teachings. Such variations are not to be regarded as a departure from the spirit and scope of the teachings.
abstract
In some aspects, this disclosure relates to improved Z-grade materials, such as those used for shielding, systems incorporating such materials, and processes for making such Z-grade materials. In some examples, the Z-grade material includes a diffusion zone including mixed metallic alloy material with both a high atomic number material and a lower atomic number material. In certain examples, a process for making Z-grade material includes combining a high atomic number material and a low atomic number material, and bonding the high atomic number material and the low atomic number together using diffusion bonding. The processes may include vacuum pressing material at an elevated temperature, such as a temperature near a softening or melting point of the low atomic number material. In another aspect, systems such as a vault or an electronic enclosure are disclosed, where one or more surfaces of Z-grade material make up part or all of the vault/enclosure.
claims
1. A magnetic energy filter having plural magnetic fields and designed to deflect a trajectory of an electron beam extending from an entrance window to an exit slit, said trajectory being in a plane, said magnetic energy filter comprising: said magnetic fields being at least four in number and including first, second, third, and fourth magnetic fields, the trajectory of the electron beam passing through said at least four magnetic fields in the order first, second, third, and fourth; said plural magnetic fields defining an electron trajectory that has a rotational symmetry axis located midway between said second and third magnetic fields, said axis being perpendicular to said plane; and said second and third magnetic fields located on opposite sides of a line and being opposite in polarity, said line being in said plane and intersecting said rotational symmetry axis at a point. 2. The magnetic energy filter of claim 1 , wherein said plural magnetic fields include first and second magnetic fields, and wherein said first and second magnetic fields are opposite in polarity. claim 1 3. The magnetic energy filter of claim 2 , wherein the sum of the absolute values of the beam deflection angles of said magnetic fields is in excess of 540xc2x0. claim 2 4. The magnetic energy filter of claim 2 , wherein said magnetic fields are four in number, and wherein the beam deflection angles of said magnetic fields, respectively, are about 110xc2x0, xe2x88x92250xc2x0, 250xc2x0, and xe2x88x92110xc2x0, respectively, in this order from the entrance side. claim 2 5. The magnetic energy filter of claim 1 , wherein said plural magnetic fields include first and second magnetic fields, and wherein said first and second magnetic fields are identical in polarity. claim 1 6. A magnetic energy filter having plural magnetic fields and designed to deflect a trajectory of an electron beam extending from an entrance window to an exit slit, said trajectory having a first direction in which the electron beam entering said entrance window and a second direction in which the electron beam passes through said exit slit, said second direction being aligned with said first direction, said trajectory being in a plane, said magnetic energy filter comprising: deflecting magnets mounted on opposite sides of a straight line in said plane, said straight line connecting said entrance window and said exit slit. 7. The magnetic energy filter of claim 5 or 6 , wherein the sum of the absolute values of the beam deflection angles of said magnetic fields is set to about 720xc2x0. claim 5 6
044735294
description
DETAILED DESCRIPTION OF AN EMBODIMENT With reference to FIG. 1, a section of conduit 1 of the cooling circuit of the shut-down reactor can be seen which is tapped by a purging means made up by a length of pipe 2 and a valve 3. An enclosure 5 of small dimension is connected in a sealed manner to the length of pipe 2 downstream of the valve 3, this enclosure 5 making it possible to connect up the collecting device to the purging means provided on the conduit 1. The enclosure 5 is connected, by a flexible tube 6, to a drawing-off and collecting unit 7, which can be moved over the floor 8 of the reactor building. This drawing-off and collecting unit is made up by a trolley 9, to which a reservoir 10, a separating and venting unit 11 and a vacuum pump 12 are fixed. The internal volume of the reservoir 10 is separated into two parts by a flexible membrane 15, the upper part of the vessel being connected by a pipe 16 to the vacuum pump 12 and the lower part being connected to the lower part of the phase separator 11, by means of a length of pipe, 18. A valve 43 allows air to be introduced into the vessel 10 in order to release the vacuum in the upper part of the vessel. A valve 20 is provided for closing off communication between the phase separator 11 and the lower half of the vessel 10. The upper half of the phase separator 11 is provided with a gas venting device 24, which is in communication with the inside of the container for venting the gases which have been separated from the liquid, via a filter 25. The flexible pipe 6 is extended inside the gas separator by a vertical crook-shaped pipe 27 which allows the gas and liquid to be separated as the liquid falls to the bottom of the phase separating container 11. In FIG. 2, the vessel 5 can be seen which allows the device for collecting the removed fluids to be connected to the purging means provided on the conduit 1 of the reactor cooling circuit. The short length of piping 2, constituting the purge means for the section of conduit 1, has a plate 30 fixed to it which includes an abutment region 31 and to which it is possible to fix, in a sealed manner, a lip 32 of a flexible material, constituting the upper end part of the vessel 5. A clamping ring 33 makes it possible to fix, in a sealed manner, the vessel 5 onto the base of the short length of pipe 2, constituting a purging means for the conduit 1. The vessel 5 is made of a flexible or rigid material and includes transparent regions which make it possible to follow the progress of the purging operation. The vessel 5 is provided with two manipulating gloves 34 which are fixed in a sealed manner into openings in the vessel 5. The end of the short length of pipe 2 which is arranged inside the vessel 5, when the collecting device has been connected up to this length of pipe includes a device for providing a sealed closure which can be operated by an operator from outside the vessel 5, making use of the gloves 34. This device for providing a sealed closure bears against a shoulder 35, constituting the lower part of the short length of pipe 2 and includes a sleeve 36 and a plug 38 against which the upper part of the screw 37 bears. A sealing gasket 40 is inserted between the plug 38 and the shoulder 35. Closing and release of the sealed closure for the length of pipe 2 can be carried out by the operator with the aid of a tool 41, which is placed inside the vessel 5 on a filtration grid 42, which has the dual purpose of providing a support for the tool and providing a filter element for the liquids removed, which penetrate into the vessel 5. This vessel 5 has, at its lower portion, an outlet 45 which is connected to the flexible pipe 6. A sprinkling device is also arranged inside the vessel 5 which provides for decontamination of the components of the closure device for the length of pipe 2, as well as decontamination of the vessel 5 and of the devices which this vessel may contain. The annular conduit 48 carrying sprinkling nozzles 50 is connected to a pipe 51 through which it is supplied with a decontamination solution which is held in a reservoir (not shown), and is sent under pressure through the pipe 51. An operation for collecting liquids and gas originating from the purging of the cooling concuit of a nuclear reactor will now be described. The complete device is brought to a position where it is close to a short length of pipe 2, constituting a purging means for a section of the conduit. Displacement of the apparatus is easy thanks to the provision of the trolley 9, which allows for transport of all the components constituting this device, the vessel 5 in this case being in a position where it is not connected to a purging means 2. The length of the pipe 6 is approximately 5 meters, which makes it possible, by arranging the trolley at the desired location, to reach all the points provided for purging on the cooling circuit of the shut-down reactor. The operator has available inside the glove box a complete replacement assembly for closing off the short length of pipe 2, this replacement assembly comprising a plug, such as that shown at 38, a sealing element, such as that shown at 40, and a screw, such as that shown at 37. A tool for disassembling the closure element from the short length of pipe such as that shown at 41, has also been placed inside the vessel. The purging pipe 2 is closed by a complete assembly such as that shown in FIG. 2. The vessel 5 which is provided with suitable handles so that it may be manipulated is then brought to a position where it is in the region of the bearing surface 31 of the plate 30 so that the flexible lip 32 becomes applied to this bearing region 31. Then connection between the vessel and the short length pipe 2, is established using the quick action clamping sleeve 33. The operator then carries out disassembly, using the gloves 34 and the tool 41 of the closure device which is in position at the end of the short length of pipe 2. The operator then places the screw 37 and the plug 38 as well as the seal 40 on the filtration grid 42 which provides an area where these closure components may be stored. The valve is then opened so as to carry out purging of the section 1 of conduit. If the difference in level between the point at which purging is being done and the reservoir 10 is adequate, it will not be necessary to start up the vacuum pump which makes it possible to provide a suction effect in the lower part of the collecting reservoir 10, via the intermediary of the flexible membrane 15. In the contrary case, it will be necessary to start up the pump 12, which can be done using a control box located close to the vessel 5, constituting the glove box, or actually inside it. As the vessel is partly transparent, it is possible to follow the drainage operation of the conduit by simple visual checking. The removed liquid flows through the length of pipe 2 to the inside of the vessel 5, and is then filtered by the grid 42 and leaves the vessel 5 by way of the outlet passage 45 which is joined to the pipe 6. The removed liquid flows into a phase separator 11, after having passed through pipe 6. The liquid which has collected in the lower part of this phase separator is then forced into the lower part of the reservoir 10 either as a result of suction due to the creation of a vacuum in the upper part of reservoir 10, or as a result of natural flow if a sufficient difference in level exists between the conduit which is being drained and the reservoir 10. When the removal of liquid has been finished, the length of pipe 2 is closed off with the new closure element assembly held in the vessel 5. The assembly, which has been dismounted before the purging operation was commenced, is decontaminated by making use of the sprinkling arrangement 48. When the entire conduit system has been drained and when it is intended to start the re-filling of this conduit system, collection of the air filling the conduit system is carried out by fixing the vessel 5 to the end of the conduit arrangement by connecting it to a vent pipe which includes a closure arrangement identical to the one used for the short pipes used for draining the liquid. As the piping system becomes filled, the air is driven out via the vent pipe and passes into the vessel 5, and then passes through the flexible tube 6 into the phase separator 11. In the phase separtor 11, the liquid which has been carried in the air falls into the lower part of the container while the air itself, after passing through the filtering wall 25, leaves by the vent pipe 24, the cock of which has been opened. The air is consequently discharged into the atmosphere of the building while the contaminated liquid is eliminated in the same way as was the case with the drained liquid which is collected in the lower part of the reservoir 10, before being sent to a retreatment installation. In order to do this, at the end of an operation for venting and removing purge liquids in the conduit system the collecting device is transferred to a position close to a circuit for effluent treatment which allows the effluence to be led to a treatment and decontamination unit. The invention is not limited to the embodiment which has just been described, but rather includes all variations of it. Thus, it may be possible to use a remote control device as a replacement for the gloves in the vessel 5, and one might use a manner of fixing the vessel 5 on the short pipe 2 different from the manner of fixing which has been envisaged, such fixing being done using a screw fitting or a bayonet fitting. It will be seen that the main advantages of the device according to the invention are the avoidance of a complex and cumbersome fixed circuit and the enablement to carry out the collecting operations for the liquid and gases in the conduit system in a rapid manner and in complete safety. A further advantage of the device which has been described is that there is no pump in the purge circuit, and that drawing-off of the contaminated substances is done by means of a sealed flexible membrane. Finally, the device according to the invention can be used not only in the case where it is desired to purge the conduit of a pressurized water nuclear reactor, but also where it is necessary to purge any piping system or equipment which may contain radioactive substances.
claims
1. A device for centering a temperature measurement device inside a tube reactor that will be filled with catalyst, comprising a single inflatable bladder mechanically and fluidically attached to a centering ring. 2. The device of claim 1, wherein a pressurized gas conduit is located inside the centering ring and is fluidically attached to a compressed gas source. 3. The device of claim 1, wherein the single inflatable bladder is configured to center the centering ring within a reactor tube when inflated. 4. A device for centering a temperature measurement device inside a tube reactor that will be filled with catalyst, comprising:a centering ring with an interior and an exterior, configured to accommodate a temperature measurement device and a pressurized gas conduit in the interior,a single inflatable bladder mechanically and fluidically attached to the exterior of the centering ring,the pressurized gas conduit fluidically attached to the centering ring such that a flow of pressurized gas exiting the pressurized gas conduit passes through a gas passage into the single inflatable bladder. 5. The device of claim 4, wherein the pressurized gas conduit is fluidically attached to a compressed nitrogen source. 6. The device of claim 4, wherein the pressurized gas conduit is fluidically attached to a compressed air source. 7. The device of claim 4, wherein the single inflatable bladder is configured to center the centering ring within a reactor tube when inflated. 8. The device of claim 4, wherein the temperature measurement device comprises a distal end, and the distal end is attached to a distal end mesh disk.
abstract
The present invention relates a probe forming lithography system for generating a pattern on to a target surface such as a wafer, using a black and white writing strategy, i.e. writing or not writing a grid cell, thereby dividing said pattern over a grid comprising grid cells, said pattern comprising features of a size larger than that of a grid cell, in each of which cells said probe is switched “on” or “off, wherein a probe on said target covers a significantly larger surface area than a grid cell, and wherein within a feature a position dependent distribution of black and white writings is effected within the range of the probe size as well as to a method upon which such system may be based.
description
This application is related to U.S. patent application Ser. No. 13/738,923 entitled “A Method of Timing Laser Beam Pulses to Regulate Extreme Ultraviolet Light Dosing,” filed on even date herewith. 1. Field of the Invention The present invention relates generally to laser technology for photolithography, and more particularly to EUV dose control during laser firing. 2. Description of the Prior Art The semiconductor industry continues to develop lithographic technologies which are able to print ever-smaller integrated circuit dimensions. Extreme ultraviolet (“EUV”) light (also sometimes referred to as soft x-rays) is generally defined to be electromagnetic radiation having wavelengths of between 10 and 110 nm. EUV lithography is generally considered to include EUV light at wavelengths in the range of 10-14 nm, and is used to produce extremely small features (e.g., sub-32 nm features) in substrates such as silicon wafers. These systems must be highly reliable and provide cost-effective throughput and reasonable process latitude. Methods to produce EUV light include, but are not necessarily limited to, converting a material into a plasma state that has one or more elements (e.g., xenon, lithium, tin, indium, antimony, tellurium, aluminum, etc.) with one or more emission line(s) in the EUV range. In one such method, often termed laser-produced plasma (“LPP”), the required plasma can be produced by irradiating a target material, such as a droplet, stream or cluster of material having the desired line-emitting element, with a laser beam at an irradiation site. The line-emitting element may be in pure form or alloy form (e.g., an alloy that is a liquid at desired temperatures), or may be mixed or dispersed with another material such as a liquid. Delivering this target material and the laser beam simultaneously to a desired irradiation site (e.g., a primary focal spot) within an LPP EUV source plasma chamber for plasma initiation presents certain timing and control challenges. Specifically, it is necessary for the laser beam to be focused on a position through which the target material will pass and timed so as to intersect the target material when it passes through that position in order to hit the target properly to obtain a good plasma, and thus, good EUV light. A droplet generator holds the target material and extrudes the target material as droplets which travel along an x-axis of the primary focal spot to intersect the laser beam traveling along a z-axis of the primary focal spot. Ideally, the droplets are targeted to pass through the primary focal spot. When the laser beam hits the droplets at the primary focal spot, EUV light output is theoretically maximized. In reality, however, achieving maximal EUV output light across bursts over time is very difficult because energy generated by irradiation of one droplet varies randomly from energy generated by irradiation of another droplet. Thus, maximal EUV light output might sometimes—but not always—be realized. This variability in output is a problem for downstream utilization of the EUV light. For example, if variable EUV light is used downstream in a lithography scanner, wafers can be non-uniformly processed, with resultant diminution of quality control of dies cut from the wafers. Thus, a tradeoff of non-maximal EUV for greater reliability may be desirable. A stroboscopic pattern produces EUV in short exposures throughout exposure of a wafer die. Although this pattern of bursts can be beneficial for control of the EUV energy dose, what is needed is a method to generate—with greater reliability—acceptable levels of EUV energy output for downstream purposes—that is, to more accurately control an EUV energy dose. In one embodiment is provided a method of regulating a dose of energy produced during stroboscopic firing of an EUV light source configured to generate an energy dose target within one or more packet comprising: (a) setting by a laser controller a dose servo value for a current packet; (b) timing by the laser controller a trigger to pulse a laser beam to irradiate a droplet during the current packet; (c) sensing by a sensor EUV energy generated by irradiation of the droplet; (d) accumulating by the laser controller the sensed EUV energy with EUV energy generated by irradiation of one or more preceding droplet during the current packet; (e) repeating steps (b), (c), and (d) when the accumulated EUV energy within the current packet is less than an adjusted dose target based on the energy dose target and an accumulated dose error; and (f) mistiming by the laser controller the trigger to pulse the laser beam to not irradiate another droplet during the current packet. In another embodiment is the method further comprising: (g) calculating by the laser controller a dose error for the current packet; (h) accumulating by the laser controller the dose error for the current packet with a dose error for one or more preceding packet; (i) calculating by the laser controller a new adjusted dose target for a next packet based on the energy dose target and the accumulated dose error; and (j) calculating by the laser controller a new dose servo value for the next packet. In still another embodiment is a system for regulating a dose of energy produced during stroboscopic burst-firing of an EUV light source configured to generate an energy dose target within one or more packet comprising: a drive laser configured to pulse a laser beam when a trigger is received; a sensor configured to sense EUV energy generated by irradiation of a droplet; and a controller configured to: (a) set a dose servo value for a current packet; (b) time the trigger to pulse the laser beam to irradiate a droplet during the current packet; (c) accumulate sensed EUV energy generated by irradiation of the droplet with EUV energy generated by irradiation of one or more preceding droplet during the current packet; (d) repeat steps (b) and (c) when the accumulated EUV energy within the current packet is less than an adjusted dose target based on the energy dose target and an accumulated dose error; and (e) mistime the trigger to pulse the laser beam to not irradiate another droplet during the current packet. In yet another embodiment is the system wherein the controller is further configured to: (f) calculate a dose error for the current packet; (g) accumulate the dose error for the current packet with a dose error for one or more preceding packet; (h) calculate a new adjusted dose target for a next packet based on the energy dose target and the accumulated dose error; and (i) calculate a new dose servo value for the next packet. A method of regulating a dose of energy produced during continuous burst mode of an EUV light source comprising: (a) beginning a burst having a predetermined energy dose target; (b) timing by the laser controller a trigger to pulse a laser beam to irradiate a droplet during the burst; (c) sensing EUV energy generated by the droplet; (d) calculating by the laser controller a current dose error for the droplet based on the sensed EUV energy and the energy dose target; (e) accumulating by the laser controller a burst error based on the current dose error and a running burst error calculated for one or more preceding droplet during the burst; (e) repeating steps (b)-(e) for a next droplet when the burst is not finished and the accumulated burst error does not meet or exceed a threshold burst error; (f) mistiming by the laser controller the trigger to pulse the laser beam to not irradiate the next droplet when the burst is not finished and the accumulated burst error meets or exceeds the threshold burst error; and (g) repeating steps (c)-(g) until the burst is finished. A system for regulating a dose of energy produced during continuous burst firing of an EUV light source configured to generate an energy dose target comprising: a drive laser configured to pulse a laser beam when a trigger is received; a sensor configured to sense EUV energy generated by irradiation of a droplet; and a controller configure to: (a) time the trigger to pulse a laser beam to irradiate a droplet during the burst; (b) calculate a current dose error for the droplet based on the sensed EUV energy and the energy dose target; (c) accumulate a burst error based on the current dose error and a running burst error calculated for one or more preceding droplet during the burst; (d) repeat steps (a)-(c) for a next droplet when the burst is not finished and the accumulated burst error does not meet or exceed a threshold burst error; (e) mistime the trigger to pulse the laser beam to not irradiate the next droplet when the burst is not finished and the accumulated burst error meets or exceeds the threshold burst error; and (f) repeat steps (b)-(e) until the burst is finished. As discussed above, energy (light) output by an EUV system can be used downstream in a number of applications, e.g., semiconductor lithography. In a typical scenario, EUV output might be passed to a lithography scanner in stroboscopic bursts to irradiate photoresist on successive wafers. In laser systems with no master oscillator (i.e., “NOMO” systems), such stroboscopic bursts of energy are achieved by controlling RF pump power to switch a laser between “on” and “off” states. Thus, the amount of energy passed for downstream dosing is controlled by this RF power pumping. MOPA laser systems (i.e., systems with a master oscillator and power amplifier, including those with a pre-pulse configuration, “MOPA+PP systems”) are capable of generating higher power output from a pulsed laser source than are NOMO systems, and are therefore preferable for some downstream applications. Downstream dosing in MOPA systems is not, however, as easily controlled as in NOMO systems because of laser start-up dynamics (e.g., temperature dependent oscillations) of MOPA systems and/or thermal instability of drive laser components (e.g., mirrors and/or lenses) during laser pulsing. Simply put, it is observed that the MOPA+PP system is unable to produce adequate stable levels of EUV for a period of time immediately after switching on an RF signal to power amplifiers. Thus, cycling the MOPA+PP laser system between “on” and “off” states is not a particularly practical or efficient way to control EUV dosing for downstream applications. As described herein with respect to various embodiments, the problematic laser start-up can be avoided by instead continuously pulsing the laser—that is, by keeping the laser system “on” (i.e., maintaining the RF signal gate in a continuous “on” state). Rather than switching the laser between “on” and “off” states, energy output levels can be controlled via a procedure to adjust timing of laser beam pulses so that some—but not all—pulses irradiate droplets at the primary focal spot. By regulating how many droplets are irradiated by laser beam pulses, the output energy dose can be maintained at a desired (and stable) dose target level. More specifically, the drive laser (e.g., MOPA) is switched “on” to fire long bursts (e.g., 2 sec.) of pulses, then switched “off” for a short period, then switched “on” to fire long bursts of pulses, etc. Within the long bursts, the drive laser can be timed to fire stroboscopically—that is, to continuously fire short mini-bursts (or “packets”), each having a pre-determined number of rapid pulses. During each packet, pulses are timed to lase droplets in the primary focal spot and thereby generate EUV energy-until a dose target of EUV has been achieved. Once the generated EUV energy within the packet reaches the dose target, pulses are timed to fire so as to not lase the droplets during the remainder of the packet, and thereby prevent additional EUV light generation during those portions of the packet. On a packet-to-packet basis (i.e., between packets), calculated dosing error (that is, how much the achieved dose differs from the dose target) from previous packets is used to fine-tune the dose target for the next packet. Alternatively, the drive laser (e.g., MOPA) can be timed to fire continuously throughout the long bursts of pulses (i.e., fire in a continuous burst mode). During each burst, pulses are timed to lase droplets in the primary focal spot and thereby generate EUV energy—as long as dose error (i.e., deviation of obtained EUV energy from the desired energy dose target) accumulated within the burst does not meet or exceed an acceptable level of error. Once the accumulated dose error for the burst (“accumulated burst error”) meets or exceeds the level of acceptable error, a next pulse is timed to fire so as to not lase a droplet, and thereby drive the accumulated burst error back to an acceptable level. When the dose error for the burst is at an acceptable level, a next pulse is again timed to lase a droplet in the primary focal spot and thereby generate EUV energy. Thus, the method described herein modulates pulse timing so that a desired dose target is obtained. For example, if pulses are fired at a rate of 50,000 pulses/sec, and all pulses are fired on-droplet, then an average packet output of 35 watts would be achieved. If, however, the dose target is only 30 watts, the method described herein provides a way to limit the achieved dose to that 30 watts—even at a pulse rate of 60,000 pulses/sec. FIG. 1 illustrates some of the components of a typical LPP EUV system 100. A drive laser 101, such as a CO2 laser, produces a laser beam 102 that passes through a beam delivery system 103 and through focusing optics 104. Focusing optics 104 have a primary focal spot 105 at an irradiation site within an LPP EUV source plasma chamber 110. A droplet generator 106 produces and ejects droplets 107 of an appropriate target material that, when hit by laser beam 102 at the irradiation site, produce plasma that emits EUV light. The EUV light is collected by an elliptical collector 108 which focuses the EUV light from the plasma at an intermediate focus 109 for delivering the produced EUV light to, e.g., a lithography system. Intermediate focus 109 will typically be within a scanner (not shown) containing boats of wafers that are to be exposed to the EUV light, with a portion of the boat containing wafers currently being irradiated by light through intermediate focus 109. In some embodiments, there may be multiple drive lasers 101, with beams that all converge on focusing optics 104. One type of LPP EUV light source may use a CO2 laser and a zinc selenide (ZnSe) lens with an anti-reflective coating and a clear aperture of about 6 to 8 inches. Energy output from the LPP EUV system varies based on how well laser beam 102 can be focused and can maintain focus over time on droplets 107 generated by droplet generator 106. Optimal energy is output from EUV system 100 if the droplets are positioned in primary focal spot 105 when hit by laser beam 102. Such positioning of the droplets allows elliptical collector 108 to collect a maximum amount of EUV light from the generated plasma for delivery to, e.g., a lithography system. A sensor (not shown, e.g., narrow field (NF) camera) senses the droplets as they pass from droplet generator 106 through a laser curtain during travel to primary focal spot 105 and provides droplet-to-droplet feedback to EUV system 100, which droplet-to-droplet feedback is used to adjust droplet generator 106 to re-align droplets 107 to primary focal spot 105 (i.e., “on-target”). When firing drive laser 101 in stroboscopic or continuous burst modes, EUV system 100 maintains droplets 107 on-target reasonably well using closed-loop (droplet-to-droplet) feedback according to techniques known in the art. Regardless of how well droplets are maintained on-target, however, total energy produced during a packet can vary due to random fluctuations in the amount of energy generated by each irradiated droplet. These random fluctuations make maintenance of a constant dose target output difficult. Maintaining a constant level of output energy is, however, important for downstream purposes. If a constant level of output energy cannot be maintained, then downstream use of the output energy within, e.g., a lithography scanner negatively affects silicon wafer patterning. Energy generated during burst firing can be maintained at a reliably constant level by adjusting the timing between the arrival of a droplet at the primary focal spot and the arrival of the laser beam at the primary focal spot as will now be described with reference to FIGS. 2, 3, and 4. FIGS. 2 and 3 illustrate schematically the orientation of droplets 107 during burst firing when the laser is timed to pulse, respectively, to irradiate a droplet (i.e., to pulse “on-droplet”) and to avoid irradiating a droplet (to pulse “off-droplet”). FIG. 4 is a graph depicting energy generated over time during periods of laser pulsing to irradiate droplets and during periods of mistimed laser pulsing to avoid irradiating droplets. Referring first to FIG. 2, when the laser is timed to pulse on-droplet (“on-droplet pulsing”), the pulse of laser beam 102 hits a droplet 107 at primary focal spot 105, the target material of droplet 107 is vaporized, and a plasma 202 is generated at primary focal spot 105. EUV energy emitted from plasma 202 is collected by elliptical collector 108 and reflected onto intermediate focus 109 where it passes into or is used by, e.g., a lithography system. As shown in FIG. 4, the generated EUV energy during on-droplet pulsing 401 clusters, on average, around a mean energy value (here, approximately 0.45 mJ), but is highly variable due to random fluctuations of energy generated for each droplet. This variability can drive the obtained energy dose from any given packet away from a desired constant EUV dose target and thereby negatively impact downstream operations. Referring now to FIG. 3, when the laser pulsing is mistimed to pulse off-droplet (“off-droplet pulsing”), the pulse of laser beam 102 passes through primary focal spot 105 between droplets so that the target material of the droplet is not vaporized, and no plasma is generated at primary focal spot 105. In the MOPA+PP system, timing of a trigger to pulse can be either advanced or delayed such that laser beam 102 passes through primary focal spot 105 without hitting droplet 107. As shown in FIG. 4, little or no EUV energy is therefore produced when pulsing off-droplet 402. Embodiments of the method described herein for stroboscopic firing determine, on a pulse-to-pulse basis within a packet, whether the desired energy dose target of a current packet has been achieved. Thus, after a droplet within a packet is lased, the total energy dose for the packet is calculated and compared to the desired energy dose target. If the desired energy dose target has not been achieved, the trigger to the drive laser for the next pulse is timed so that a next droplet is lased on-droplet. If the desired energy dose target has been achieved, the trigger to the drive laser for the next pulse is mistimed so that the next droplet is lased off-droplet so that no additional energy is generated within the current packet. Between packets (i.e., on a packet-to-packet basis), calculated dose error from the current packet is accumulated with dose error from previous packets and used as a “servo” to fine-tune the dose target for a next packet. The block diagram of FIG. 5 shows EUV system components involved in dose control of generated EUV light according to one embodiment. A laser controller 502 times a trigger to drive laser 101 to pulse on-droplet such that the droplets, when irradiated, generate plasma that emits EUV energy. The amount of collected EUV energy is sensed on a pulse-to-pulse basis by an energy output sensor 501 and passed to laser controller 502 which accumulates a running total of the total EUV energy generated during a current packet. Sensor 501 is either a sensor within LPP EUV source plasma chamber 110, e.g., an EUV side sensor positioned at 90° with respect to the laser beam 102 or a sensor within the scanner measuring energy passed through intermediate focus 109. When the accumulated EUV equals or minimally exceeds the dose target, laser controller 502 mistimes the trigger to drive laser 101 such that drive laser 101 pulses off-droplet to avoid generating additional EUV energy. Drive laser 101 continues to pulse off-droplet for the remainder of the current packet. When the current packet is complete, laser controller 502 calculates dose error for the current packet, and accumulates that dose error with dose error from preceding packets. Controller 502 then adjusts, based on that accumulated dose error, the dose target against which the accumulated achieved EUV energy is compared during a next packet. Embodiments of the method of laser beam pulse timing disclosed herein for stroboscopic pulsing regulate average EUV by firing some portion of pulses within a packet off-droplet. For example, when pulse energy increases, the number of pulses fired on droplet (the pulse count) is decreased in order to maintain the same average EUV. Over time, random fluctuations of generated EUV energy can be better understood so that packet size can be adjusted to minimize lasing time off-droplet. Referring now to FIG. 6, a flowchart of a method of timing laser beam pulses to control stroboscopic EUV dose according to one embodiment is presented. Before initiating the following steps, a dose target of EUV energy to be achieved within each packet of a burst (i.e., a setpoint to which the packet energy is to be regulated) and a packet size (i.e., a total number of pulses within each packet) are input by a user or determined by the system. The packet size is preferably selected so as to be the smallest packet size which allows the EUV energy dose to be controlled. If the packet size is too small (e.g., 1 or 2 droplets), it may not be possible to mistime pulsing for enough droplets to adequately control the EUV energy dose. If the packet size is too large (e.g., 1000 droplets), uncontrollable error accumulates throughout the packet (e.g., as shown in FIG. 4), with consequent poor control over the amount of EUV generated for downstream dosing. Thus, the packet size is ideally selected so that pulse timing can be modulated, but only for the droplets at the back end of a packet. For example, a packet size of 50 drops may be appropriate if an adequate dose can be achieved on average with 40 droplets (which would allow pulse mistiming to occur over the last 10 droplets). In step 601, laser controller 502 sets a dose servo value for a current packet. The dose servo value is an adjustment factor by which a dose target is increased or decreased as a function of the dose energies produced by previous packets. That is, the desired dose target is fine-tuned by the dose servo value which is determined (as discussed elsewhere herein) by error from previous packets. In one embodiment, the dose servo value is set to 0 for a first packet. Once the servo value has been set, firing of laser pulses for a packet can begin. Steps 602-607 are performed on a pulse-to-pulse basis—that is, for each pulse of the packet. In step 602, laser controller 502 times a trigger to pulse drive laser 101 on-droplet so that laser beam 102 irradiates droplet 107 in primary focal spot 105. In step 603, sensor 501 senses how much EUV energy has been generated by the irradiation of droplet 107 in step 602. In step 604, laser controller 502 accumulates EUV energy by adding the sensed EUV energy of step 603 to a running total of EUV generated since the first pulse of the packet (that is, since step 601). In step 605, laser controller 502 determines whether the accumulated EUV energy of step 604 is equal to or minimally greater than an adjusted dose target. The adjusted dose target is the sum of the dose target and the dose servo value of step 601. The accumulated EUV energy may be minimally greater than an adjusted dose target for various reasons, e.g., because of random fluctuations in EUV generated by each irradiated droplet and/or because energy generated by each irradiated droplet (even without random fluctuation) is not a constant even value. If the accumulated EUV energy is not greater than or equal to the adjusted dose target of step 601, laser controller 502 returns to step 602 to trigger another on-droplet pulse and repeat steps 603, 604, and 605. If the accumulated EUV energy is greater than or equal to the adjusted dose target, then in step 606, laser controller 502 mistimes the trigger to pulse drive laser 101 off-droplet such that laser beam 102 does not irradiate droplet 107 in primary focal spot 105. The mistimed trigger can be delayed or advanced in time relative to timing of a next trigger for on-droplet pulsing—that is, relative to timing of a next trigger for on-droplet pulsing if the accumulated EUV energy of step 604 were not greater than or equal to the adjusted dose target. In step 607, laser controller 502 determines whether the packet is complete—that is, whether the number of pulses fired by drive laser 101 is equal to the packet size. If laser controller 502 determines that the packet is not complete, laser controller 502 returns to step 606 to trigger another pulse off-droplet. If laser controller 502 determines that the packet is complete, then steps 608-611 and another step 601 are performed before a next packet begins. In step 608, laser controller 502 calculates a dose error for the packet. Dose error is defined as the dose target minus the EUV energy accumulated over the packet. Mathematically,dose errorpacket=dose target−ΣEUVpacket. In step 609, laser controller 502 accumulates dose error from the packet with dose error from previous packets. In step 610, laser controller 502 uses the accumulated dose error calculated in step 609 to calculate a new dose servo value. In one embodiment, the new dose servo value is calculated asprevious servo value+(gain*accumulated dose error)where the previous dose servo value is the dose servo value set in step 601. The gain is preferably 1.0. The gain can range between 0.01 and 100. In step 611, laser controller 502 resets the accumulated EUV to zero in preparation for a next packet and returns to step 601 where the new dose servo value is set as the dose servo value for the next packet. Importantly, packets repeat at a regular frequency. That is, regardless of how many pulses within a packet hit droplets at primary focal spot 105, a packet begins at a set time after firing the number of pulses in a packet. Because the number of pulses which hit droplets within a packet changes based on how much energy has been generated by irradiation of previous droplets, however, the last pulse to hit a droplet within a packet may vary across different packets. Further, because packets have a set number of pulses, although not shown in the figure, it is to be understood that if the set number of pulses has been reached during looping of steps 602-605, the packet may conclude without needing to mistime the trigger to pulse the laser off-droplet (e.g., if the accumulated EUV energy for the packet has not met or exceeded the adjusted dose target for the packet). Specifically, if laser controller 502 determines, after accumulating EUV energy for the packet in step 604, that the packet is complete (i.e., if the number of pulses fired by drive laser 101 is equal to the packet size), then laser controller 502 does not return to step 602 to time another trigger to pulse drive laser 101 on-droplet, and instead performs steps 608-611 before a next packet begins. Thus, laser controller 502 calculates the dose error for the packet (step 608), accumulates the dose error from the packet with dose error from previous packets (step 609), uses the accumulated dose error calculated in step 609 to calculate a new dose servo value (step 610), and resets the accumulated EUV to zero in preparation for a next packet before returning to step 601 where the new dose servo value is set as the dose servo value for the next packet (step 611). FIGS. 7 and 8 are time-aligned plots showing data generated over a 2-second burst using one embodiment of the laser beam pulse timing method to control EUV dose. FIG. 7 shows percent variation around an energy dose target achieved over the 2-second burst. As indicated by the plotted percent dose energy variation around a dose target seen in the figure, packet dosing controlled by pulse timing is achieved well within ±0.5% of dose target (i.e., within ±0.5% of 0 in the figure). The upper panel of FIG. 8 shows packet EUV generated over the 2-second burst. As seen in the figure, energy is maintained at the dose target (here, approximately 20 mJ) over time—and is stably maintained within ±0.5% of dose target. The lower panel of FIG. 8 shows a corresponding pulse count over the 2-second burst. Each diamond represents a count of the number of pulses on-droplet (“pulse count”) within a single packet. Exemplary packet EUV energy (upper panel) and packet pulse count (lower panel) with greater on-droplet pulsing 801 and with greater off-droplet pulsing 802 (and, therefore, a lower pulse count) are indicated by arrows. As indicated by the arrows, depending on random fluctuations of generated EUV energy, fewer pulses may be needed to achieve a constant EUV energy. As applied to continuous burst firing, embodiments of the method described herein determine, on a pulse-to-pulse basis within each burst, a dose error for each droplet (i.e., how much obtained EUV energy deviates from the desired energy dose target). Dose error is accumulated as the burst progresses. Thus, after a droplet within a burst is lased, dose error for that droplet is calculated and accumulated with dose error for preceding droplets within the burst. If the accumulated dose error for the burst (i.e., “accumulated burst error”) meets or exceeds an acceptable level of burst error (i.e., “threshold burst error”), the trigger to the drive laser for a next pulse is mistimed so that the next droplet is lased off-droplet and no additional energy is generated. Since no additional energy is generated, the dose error for that next droplet is of sufficient magnitude to drive the accumulated burst error back to an acceptable level (i.e., below a threshold burst error). When the accumulated burst error is less than the threshold burst error, the trigger to the drive laser for a next pulse is timed so that the next droplet is lased on-droplet to generate additional EUV energy. Referring now to FIG. 9, a flowchart of a method of timing laser beam pulses to control EUV dose during continuous burst firing according to one embodiment is presented. Before initiating the following steps, a dose target of EUV energy to be achieved within each burst (i.e., a setpoint to which the burst energy is to be regulated) and a threshold burst error (i.e., an acceptable level of burst error) are input by a user or determined by the system. Once the dose target has been set, then, in step 901, firing of laser pulses for a burst can begin. The process of steps 902-908 are performed on a pulse-to-pulse basis—that is, for each pulse of the burst. In step 902, laser controller 502 times a trigger to pulse drive laser 101 on-droplet so that laser beam 102 irradiates a current droplet 107 in primary focal spot 105. In step 903, sensor 501 senses how much EUV energy has been generated by the irradiation of current droplet 107 in step 902. In step 904, laser controller 502 calculates a current dose error for current droplet 107. Current dose error is defined as the EUV energy generated by irradiation of current droplet 107 (and sensed in step 903) minus the dose target. Mathematically,current dose error=EUVcurrent droplet−dose target. In step 905, laser controller 502 accumulates a burst error by adding the current dose error calculated in step 904 to a running total of dose error accumulated since the first pulse of the burst (that is, since step 901). The current dose error is adjusted by a gain which can range between 0.01 and 100, but is preferably 1. In one embodiment, the accumulated burst error is calculated asrunning burst error+(gain*current dose error)where the running burst error is a running total of dose error accumulated from preceding droplets within the burst. That is, the running burst error is the accumulated burst error determined for a preceding droplet 107 in step 905. The running burst error is set to 0 when the current droplet is the first droplet in a burst. In step 906, laser controller 502 determines whether the burst is finished. If laser controller 502 determines that the burst is finished, laser controller 502 exits the pulse timing method and/or returns to step 901 to begin another burst. If, in step 906, laser controller 502 determines that the burst is not finished, then, in step 907, laser controller 502 determines whether the accumulated burst error of step 905 meets or exceeds a burst error threshold. The burst error threshold is input by a user or determined by the system. The burst error threshold is preferably zero, but may be greater or less than zero. If laser controller 502 determines in step 907 that the accumulated burst error does not meet or exceed the burst error threshold, then laser controller 502 returns to step 902 to time a trigger to pulse drive laser 101 on-droplet so that laser beam 102 irradiates a next droplet 107 in primary focal spot 105. If laser controller 502 determines in step 907 that the accumulated burst error meets or exceeds the burst error threshold, then, in step 908, laser controller 502 mistimes the trigger to pulse drive laser 101 off-droplet such that laser beam 102 does not irradiate a next droplet 107 in primary focal spot 105. The mistimed trigger can be fired so the laser pulse arrives at the primary focal spot early or late relative to the arrival of the droplet. After mistiming the trigger to pulse drive laser 101 off-droplet for next droplet 107, laser controller 502 returns to step 903 to sense how much EUV energy has been generated by irradiation of current droplet 107, and then, in step 904, to calculate a current dose error for next droplet 107. Because no EUV is generated for next droplet 107 due to the mistiming of the pulse, the calculated current dose error for next droplet 107 is equal in magnitude but opposite in sign to the dose target. For example, if the dose target is 1.75 mJ, the calculated current dose error would be −1.75 mJ— or 100%—which is very high relative to error around the dose target for an irradiated droplet (which is typically much less than 40%). Thus, when laser controller 502, in step 905, accumulates burst error by adding the relatively large current dose error for next droplet 107 to the running burst error, the accumulated burst error is typically reduced relative to the accumulated burst error for previous droplet 107. Assuming logic controller 502 decides, in step 906, that the burst is not finished, logic controller 502 determines, in step 907, whether the accumulated burst error meets or exceeds the burst error threshold. If laser controller 502 determines that the accumulated burst error does not now meet or exceed the burst error threshold, then laser controller 502 returns to step 902 to time the trigger to pulse drive laser 101 on-droplet so that laser beam 102 irradiates another droplet 107 (which now becomes current droplet 107) in primary focal spot 105, and the process of FIG. 9 iterates from that step. If laser controller 502 determines that the accumulated burst error again meets or exceeds the burst error threshold, then, in step 908, laser controller 502 mistimes the trigger to pulse drive laser 101 off-droplet such that laser beam 102 does not irradiate a next droplet 107 in primary focal spot 105, and then returns again to step 903 to sense how much EUV energy has been generated. The process of FIG. 9 then iterates from that point. In another embodiment, the current dose error of step 904 is defined instead as the dose target minus the EUV energy generated by irradiation of current droplet 107 (and sensed in step 903). Mathematically,current dose error=dose target−EUVcurrent droplet. In this embodiment, a negative gain (rather than the positive gain of the above embodiment) is used to adjust the current dose error during computation of the accumulated burst error in step 905. The gain can range between −0.01 and −100, but is preferably −1. One of skill in the art will recognize that other embodiments that may be less intuitively satisfying are possible (but non-preferred) as long as aspects of the method are internally consistent to meet the objective of comparing, on a pulse-to-pulse basis, accumulating burst error throughout the burst to a threshold of acceptable burst error to determine whether to control energy generation by mistiming a next pulse. Specifically, the mathematics of the calculation of the current dose error (step 904) and the gain applied to the current dose error when calculating the accumulated burst error (step 905) should remain consistent with each other and with the decision rule outcomes following from the comparison of the accumulated burst error to the threshold burst error (step 907). FIG. 10 shows a sliding window of time-aligned EUV energy (upper panel) and energy dose (lower panel) generated during a continuous burst firing using laser beam pulse timing to control EUV dose according to one embodiment. As can be seen in the upper panel, although most pulses were fired on-droplet (e.g., on-droplet pulse 1001), a number of pulses were fired off-droplet (as indicated by the pulses generating 0 mJ EUV, e.g., off-droplet pulse 1002) to control error around the dose target 1003 (approximately 1.75 mJ in the figure). Consequently, as shown in the lower panel, constant dosing 1004 was achieved around 1.75 mJ and maintained well within ±0.5% of the dose target 1003 as indicated by reference number 1005. Ideally, it is believed that if targeting conditions are correct and the drive laser has adequate performance, then embodiments of the laser beam pulse timing method described herein can maintain dose energy within ±0.5% of the dose target. One of ordinary skill in the art will recognize that mistiming of laser pulses can be accomplished through a variety of mechanisms known in the art. For example, the drive laser can be fired so the laser pulse arrives at the primary focal spot early or late relative to the arrival of the droplet. Or, the timing of system shutters (e.g., electro-optic modulators or acousto-optic modulators) can be changed to let through low-level continuous wave light which is sufficient to seed amplifiers and reduce gain of the system. A preferred embodiment is to close the shutters early, and thereby advance the laser beam relative to the droplet. As is known in the art, a MOPA+PP laser system pulses both a pre-pulse and a main pulse. One of skill in the art will recognize that both the main pulse and the pre-pulse are used to lase a droplet when the laser is pulsed on-droplet, and that neither the main pulse nor the pre-pulse are used to lase a droplet when the laser is pulsed off-droplet. The disclosed method and apparatus has been explained above with reference to several embodiments. Other embodiments will be apparent to those skilled in the art in light of this disclosure. Certain aspects of the described method and apparatus may readily be implemented using configurations other than those described in the embodiments above, or in conjunction with elements other than those described above. Further, it should also be appreciated that the described method and apparatus can be implemented in numerous ways, including as a process, an apparatus, or a system. The methods described herein may be implemented by program instructions for instructing a processor to perform such methods, and such instructions recorded on a computer readable storage medium such as a hard disk drive, floppy disk, optical disc such as a compact disc (CD) or digital versatile disc (DVD), flash memory, etc., or a computer network wherein the program instructions are sent over optical or electronic communication links. It should be noted that the order of the steps of the methods described herein may be altered and still be within the scope of the disclosure. It is to be understood that the examples given are for illustrative purposes only and may be extended to other implementations and embodiments with different conventions and techniques. While a number of embodiments are described, there is no intent to limit the disclosure to the embodiment(s) disclosed herein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents apparent to those familiar with the art. In the foregoing specification, the invention is described with reference to specific embodiments thereof, but those skilled in the art will recognize that the invention is not limited thereto. Various features and aspects of the above-described invention may be used individually or jointly. Further, the invention can be utilized in any number of environments and applications beyond those described herein without departing from the broader spirit and scope of the specification. The specification and drawings are, accordingly, to be regarded as illustrative rather than restrictive. It will be recognized that the terms “comprising,” “including,” and “having,” as used herein, are specifically intended to be read as open-ended terms of art.
description
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/661,803 filed on Jun. 19, 2012, and entitled “Enclosure Package Design for Terahertz Photoconductive Antennas”, the entire contents of which are hereby incorporated by reference herein for all purposes. The disclosure herein relates to apparatus for transmitting or detecting terahertz waves, and in particular, to an enclosure with a terahertz photoconductive antenna, terahertz lens, and other optical components mounted within the enclosure. Terahertz photoconductive antennas (THz-PCAs) are used to generate or receive terahertz (THz) signals such as broadband terahertz pulses and narrowband terahertz continuous waves. After being demonstrated as practical THz sources and detectors, THz-PCAs have been the subject of a significant amount of scientific and industrial reports investigating their applications as terahertz wave transmitters and receivers. Narrowband terahertz continuous waves can be generated using two continuous-wave laser beams that are selected to provide a frequency difference in the THz range. The laser beams are combined inside an optical fiber or overlapped in free-space and subsequently mixed in a photomixer (e.g. a photo-absorbing medium) to generate a THz wave. In some cases, THz waves having a frequency line width of as low as a few KHz can be generated using this technique. Broadband terahertz pulses can be generated by exciting a THz-PCA with a femto-second short pulse laser. For example, when using a femto-second laser with an optical pulse duration of about 100-fs it is possible to generate THz pulses having a frequency content of up to about 5-THz, and an average power of a few micro-watts. In addition to generating THz waves, THz-PCAs are also capable of detecting THz waves. For example, optoelectronic techniques can be used to detect and extract both amplitude and phase information of a THz wave incident on an optically gated THz-PCA. In this case, a gating laser beam is applied using a short pulse laser, or a pair of continuous-wave lasers having a frequency difference selected to be equal to the frequency of the incident terahertz wave. The THz wave and gating laser beam applied to the THz-PCA generate a photocurrent, which is generally proportional to the amplitude of the incident terahertz wave. In conventional THz systems, one side of the THz-PCA is excited by one or more laser beams that pass through free-space to a focusing lens. Furthermore, a hyper-hemispherical silicon lens is positioned on the other side of the THz-PCA for collimating the THz signal being generated or detected. In practice, the THz-PCA and hyper-hemispherical silicon lens are mounted on two separate X-Y translation stages for maintaining optical alignment of the silicon lens, THz-PCA, and focusing lens. The X-Y translation stage typically includes a base and a platform slidably mounted to the base for supporting and moving the THz-PCA or the silicon lens. Unfortunately, these X-Y translations stages are cumbersome to operate and increase overall system complexity, thus making it difficult to calibrate and use the THz-PCA. Accordingly, there is a need for a new apparatus for transmitting or receiving terahertz waves. According to some embodiments, there is provided a design for an enclosure packaging, to package a THz-PCA with a terahertz lens in a single integrated unit. The enclosure package houses the THz-PCA with the terahertz lens attached to the back side of the THz-PCA chip. The laser beam can be delivered to the THz-PCA through free-space or through a fiber optic coupler. In the case of free-space laser beam delivery, a separate optical lens may be used to focus the laser beam on the THz-PCA. In some cases the optical lens can be integrated with the enclosure package. In the case of fiber optic laser beam delivery, small optical lenses and an optical fiber may be integrated with the enclosure package. The optical fiber may have a focusing lens structure on its tip. According to some embodiments, there is an apparatus for transmitting or receiving terahertz waves. The apparatus includes an enclosure having a front opening, a rear opening, and an internal passageway therebetween. The enclosure includes an antenna mounting structure and a lens mounting structure. A terahertz photoconductive antenna is mounted within the enclosure against the antenna mounting structure. The terahertz photoconductive antenna has a rear side for being optically energized by an optical beam passing through the rear opening of the enclosure, and a front side for transmitting or receiving the terahertz waves through the front opening. A terahertz lens is mounted within the enclosure against the lens mounting structure. The terahertz lens is positioned between the front opening and the terahertz photoconductive antenna for converging the terahertz waves being transmitted or received. The antenna mounting structure and the lens mounting structure are configured to optically align the terahertz photoconductive antenna and the terahertz lens. In some embodiments, the apparatus may include a position adjustment device for optically aligning the terahertz photoconductive antenna and the terahertz lens. The position adjustment device may include a plurality of set screws for adjustably positioning the antenna mounting structure within the enclosure. Similarly, the position adjustment device may include a plurality of set screws for adjustably positioning the lens mounting structure within the enclosure. The terahertz photoconductive antenna may include a terahertz chip dye mounted to a circuit board. Furthermore, the antenna mounting structure and the lens mounting structure may be configured to position the terahertz lens in contact with the terahertz chip dye. The enclosure may include a tubular main body with a front portion. The antenna mounting structure and the lens mounting structure may be located within the front portion of the tubular main body with the lens mounting structure being located forwardly of the antenna mounting structure. The antenna mounting structure may have a cylindrical shape with a longitudinal passageway and a recessed front portion for receiving the circuit board. The lens mounting structure may have a cylindrical shape with a longitudinal passageway and a beveled rear inner wall for holding the terahertz lens against the terahertz chip dye. The apparatus may include an O-ring between the beveled rear inner wall of the lens mounting structure and the terahertz lens. The tubular main body may have an inner annular flange for supporting the antenna mounting structure. The apparatus may also include a front lock ring for securing the lens mounting structure and the antenna mounting structure between the front lock ring and the inner annular flange of the tubular main body. The apparatus may include an optical focusing lens assembly mounted within the enclosure for directing the optical beam onto the terahertz photoconductive antenna. The optical focusing lens assembly may be movable lengthwise within the enclosure for providing an adjustable distance between the optical focusing lens assembly and the terahertz photoconductive antenna. For example, the enclosure may include a tubular main body with a rear portion having internal threads, and the optical focusing lens assembly may have a tubular lens housing with external threads for engaging the internal threads of the tubular main body so as to allow lengthwise movement. The apparatus may also include a middle lock ring and a rear lock ring for securing the optical focusing lens assembly in place within the tubular main body. The optical focusing lens assembly may include an optical focusing lens, and a retaining ring for securing the optical focusing lens to the tubular lens housing. The apparatus may also include a fiber optic coupler mounted to the tubular lens housing for receiving a fiber optic cable that supplies the optical beam through the optical focusing lens and onto the terahertz photoconductive antenna. The fiber optic coupler may include a collimating lens for collimating the optical beam onto the optical focusing lens. The apparatus may include a fiber optic coupler mounted to the enclosure for receiving a fiber optic cable that supplies the optical beam directed onto the terahertz photoconductive antenna. The apparatus may include at least one electrical connector for connecting the circuit board of the terahertz photoconductive antenna to an external electrical device. In some embodiments, the enclosure may include a main body having a rear recessed portion defining the antenna mounting structure, and a front recessed portion defining the lens mounting structure. The enclosure may also include a front cover for holding the terahertz lens against the front recessed portion of the main body. The front cover generally has a front opening therethrough. The apparatus may also include an O-ring located between the front cover and the terahertz lens. The circuit board of the terahertz photoconductive antenna may be secured to the main body using a plurality of fasteners. The front cover may be secured to the main body using a plurality of fasteners. The enclosure may include a rear cover secured to the main body using a plurality of fasteners. The rear cover general has a rear opening therethrough. The rear opening in the rear cover may have internal threads configured for attachment to an optical instrument. The apparatus may include a fiber optic cable mounted to the rear cover for directing the optical beam onto the terahertz chip dye. The apparatus may include a strain relief member for attaching the fiber optic cable to the rear cover. The fiber optic cable may include an optical fiber, and a rigid jacket wrapped around the optical fiber. The optical fiber may have a tapered tip. The fiber optic cable may further include a ferrule between the rigid jacket and the tapered tip. The tapered tip of the optical fiber may be spaced apart from the terahertz chip dye. Other aspects and features of the invention will become apparent, to those ordinarily skilled in the art, upon review of the following description of some exemplary embodiments. Referring to FIGS. 1-3, illustrated therein is an apparatus 100 for transmitting or receiving terahertz waves made in accordance with an embodiment of the present invention. As shown in FIG. 2, the apparatus 100 includes an enclosure 110, a terahertz photoconductive antenna 112 mounted within the enclosure 110 for transmitting or receiving terahertz waves, and a terahertz lens 114 mounted within the enclosure 110 for collimating or converging the terahertz waves being transmitted or received. As shown in FIG. 2, the enclosure 110 includes a tubular main body 120 having a front portion 121 with a front opening 122, a rear portion 123 with a rear opening 124, and an internal passageway 126 that extends between the front opening 122 and the rear opening 124. The enclosure 110 also includes a sleeve 128 that covers the main body 120. The enclosure 110 may be made from aluminum, which may provide strength and light weight. The enclosure 110 could also be made from other materials such as other metals, plastics, and the like. The enclosure 110 also includes an antenna mounting structure 132 for mounting the terahertz photoconductive antenna 112 within the internal passageway 126, and a lens mounting structure 134 for mounting the terahertz lens 114 within the internal passageway 126. In the illustrated embodiment, the antenna mounting structure 132 and the lens mounting structure 134 are separate pieces mounted within the tubular main body 120 and are generally cylindrical in shape with longitudinal passageways therethrough. Referring still to FIG. 2, the terahertz photoconductive antenna 112 includes a terahertz chip dye 140 mounted to a circuit board 142 such as a printed circuit board (PCB). The terahertz chip dye 140 is generally a highly resistive thin film semi-conductor and may be epitaxially grown on an InGaAs—InAlAs substrate, a GaAs substrate, or another substrate. The terahertz chip dye 140 generally includes an antenna structure such as a short or long dipole configuration, a spiral configuration, a large periodic array configuration, and the like. The terahertz chip dye 140 may be attached to the circuit board 142 using an electrically conductive epoxy such as silver epoxy or using wire bonding. This secures the terahertz chip dye 140 in place and connects the antenna structure to respective positive and negative electrical contacts on the circuit board 142. The terahertz photoconductive antenna 112 has a rear side for being optically energized by an optical beam passing through the rear opening 124 of the enclosure 110, and a front side for transmitting or receiving the terahertz waves through the front opening 122 of the enclosure 110. Furthermore, the circuit board 142 has an aperture aligned with terahertz chip dye for allowing the optical beam to impinge the terahertz chip dye 140. When transmitting terahertz waves from the terahertz photoconductive antenna 112, a voltage is applied across the positive and negative electrical contacts on the circuit board 142, and an optical beam is directed on the rear side of the terahertz dye 140. The optical beam generates mobile carriers across the terahertz chip dye 140 and results in an electrical pulse having a terahertz frequency, which in turn emits a terahertz wave from the front side of the terahertz photoconductive antenna 112. When receiving terahertz waves impinging the terahertz photoconductive antenna 112, an optical beam is directed on the rear side of the terahertz dye 140, and an incident terahertz wave impinging the front side of the terahertz dye 140 energizes the antenna structure. This produces an electrical signal across the positive and negative electrical contacts on the circuit board 142, which can be measured to determine characteristics of the terahertz wave. In some cases, a current amplifier may amplify the electrical signal produced as will be described later below. As described above, the terahertz lens 114 is generally configured to converge the terahertz waves being transmitted or received by the terahertz photoconductive antenna 112. For example, when operating as a transmitter, the terahertz lens 114 collimates the terahertz waves emitted from the terahertz photoconductive antenna 112. Alternatively, when operating as a receiver, the terahertz lens 114 focuses the terahertz waves onto the terahertz photoconductive antenna 112. In either case, the terahertz waves tend to converge. The terahertz lens 114 may have a refractive index similar to that of the terahertz photoconductive antenna 112. More specifically, the terahertz lens 114 may be made from silicon when the terahertz chip dye 140 is made from GaAs. This may reduce refraction of terahertz waves transmitted between the terahertz chip dye 140 and the terahertz lens 114. As shown in the illustrated embodiment, the terahertz lens 114 may have a hemispherical shape, and in particular, a hyper-hemispherical shape. This can help collimate or converge the terahertz waves. In some embodiments, the terahertz lens 114 may have a diameter of about 10-mm; however, larger or smaller diameter lenses could be used. In other embodiments, the terahertz lens 114 may have other configurations such as a bullet-shaped lens. In some embodiments, the terahertz lens 114 may be configured to be aplanatic, which may help reduce aberrations. In certain circumstances, a silicon hyper-hemispherical terahertz lens 114 as describe above may provide aplanatic functionality. As described above, the terahertz photoconductive antenna 112 is mounted within the enclosure 110 against the antenna mounting structure 132, and the terahertz lens 114 is mounted within the enclosure 110 against the lens mounting structure 134. More specifically, as shown, the lens mounting structure 134 is located within the front portion 121 of the tubular main body 120 forwardly of the antenna mounting structure 132. Thus, the terahertz lens 114 is located within the enclosure 110 forwardly of the terahertz photoconductive antenna 112. In some embodiments, the antenna mounting structure 132 and the lens mounting structure 134 may be configured to position the terahertz lens 114 in contact with the terahertz chip dye 140. For example, as shown in FIG. 2, the antenna mounting structure 132 may have a cylindrical shape with a recessed front portion 150 for receiving the circuit board 142. The circuit board 142 may be secured in place using fasteners such as screws (not shown). As shown in FIG. 3, the lens mounting structure 134 has a cylindrical shape with an opening smaller than the diameter of the terahertz lens 114. Furthermore, the lens mounting structure 134 has a beveled rear inner wall 152 for holding the terahertz lens 114 against the terahertz chip dye 140. The apparatus 100 may also include an O-ring 156 located between the beveled rear inner wall 152 and the terahertz lens 114. The lens mounting structure 134 may also have a conical front inner wall 154 opposite the beveled rear inner wall 152. The antenna mounting structure 132 and the lens mounting structure 134 may be secured within the enclosure 110 using a number of techniques. For example, as shown in FIG. 3, the tubular main body 120 may have an inner annular flange 160 for supporting the antenna mounting structure 132. Furthermore, the apparatus 100 may include a front lock ring 162 for securing the lens mounting structure 134 and the antenna mounting structure 132 between the front lock ring 162 and the inner annular flange 160. The lock ring 162 may be held in place using fasteners (not shown) such as screws, clips, and the like. The lock ring 162 could also be held in place using external threads that engage corresponding internal threads on the main body 120. Referring now to FIG. 2, the antenna mounting structure 132 and the lens mounting structure 134 are configured to optically align the terahertz photoconductive antenna and the terahertz lens. For example, the apparatus 100 may include one or more position adjustment devices for optically aligning the terahertz lens 114 and the terahertz photoconductive antenna 112 along an optical axis 170. As shown, the position adjustment device may include set screws 182, 184 for adjusting the position of the terahertz lens 114 or the terahertz photoconductive antenna 112. More particularly, in the illustrated embodiment, the position adjustment device includes a plurality of first set screws 182 for adjustably positioning the lens mounting structure 134 within the tubular main body 120, and a plurality of second set screws 184 for adjustably positioning the antenna mounting structure 132 within the tubular main body 120. The set screws 182, 184 extend through threaded openings on the main body 120 and engage corresponding surfaces on the antenna mounting structure 132, and the lens mounting structure 134. For example, the first set screws 182 are distributed circumferentially around the main body 120 and engage an annular recessed portion 186 that extends around the outer circumferential surface of the antenna mounting structure 132. The position of the antenna mounting structure 132 can be adjusted along a plane perpendicular to the optical axis 170 by screwing the first set screws 182 inward or outward relative to the annular recessed portion 186. In other words, the first set screws 182 can adjust the X-Y position of the antenna mounting structure 132 so as to align the terahertz photoconductive antenna 112 with the terahertz lens 114. Similar to the first set screws 182, the second set screws 184 are distributed circumferentially around the main body 120 and engage an annular recessed portion 188 that extends around the outer circumferential surface of the lens mounting structure 134. The position of the lens mounting structure 134 can be adjusted along a plane perpendicular to the optical axis 170 by screwing the second set screws 184 inward or outward relative to the annular recessed portion 188. In other words, the second set screws 184 can adjust the X-Y position of the lens mounting structure 134 so as to align the terahertz lens 114 with the terahertz photoconductive antenna 112. As shown in FIG. 3, the annular recessed portions 186, 188 may include convex protrusions 190, 192, respectively. This may provide a single point of contact between the set screws 182, 184 and the respective convex protrusions 190, 192, which can enable fine positional adjustments without significant binding. While both sets of the set screws 182, 184 are shown in the illustrated embodiment, the apparatus 100 it is possible to use only one set of set screws 182, 184 when optically aligning the terahertz lens 114 and the terahertz photoconductive antenna 11. Nevertheless, using both sets of set screws 182, 184 can be beneficial when aligning both the terahertz photoconductive antenna 112 and the terahertz lens 114 with a third optical component such as an optical focusing lens assembly 200 mounted within the enclosure, which will be described below. In other embodiments, the apparatus 100 may include other position adjustment devices. For example, the antenna mounting structure 132 and the lens mounting structure 134 may be mounted eccentrically within the tubular main body 120. In such cases, the terahertz photoconductive antenna 112 and the terahertz lens 114 could be optically aligned by adjusting the rotational position of the antenna mounting structure 132 and the lens mounting structure 134 within the tubular main body 120. In some embodiments, the terahertz photoconductive antenna 112 and the terahertz lens 114 may be pre-aligned during manufacture and assembly within the enclosure 110. In such cases, the position adjustment device may be omitted. In general, the cylindrical configuration of the enclosure 110 can help to optically align the various components of the apparatus 100. For example, the cylindrical configuration allows the terahertz photoconductive antenna 112, the terahertz lens 114, and other optical components to be concentrically aligned along the central axis of the tubular main body 120. In some embodiments, the terahertz lens 114 itself may be omitted. In such cases, the apparatus 100 may include other optical components within the enclosure 110. Referring now to FIGS. 2 and 3, the apparatus 100 may include an optical focusing lens assembly 200 mounted within the enclosure 110 for directing the optical beam onto the terahertz photoconductive antenna 112. As shown, the optical focusing lens assembly 200 includes a lens housing 210, an optical focusing lens 212, and a retaining ring 214 for securing the optical focusing lens 212 to the lens housing 210. More specifically, as shown in FIG. 2, the lens housing 210 has a recessed front portion 220 with an annular lip 222 for supporting the optical focusing lens 212. Furthermore, the recessed front portion 220 may have an internal thread for engaging a corresponding external thread on the retaining ring 214 such that screwing the retaining ring 214 into the recessed front portion 220 presses the optical focusing lens 212 against the annular lip 222 and thereby secures it in place. The apparatus 100 may also include a fiber optic coupler 240 mounted to the optical focusing lens assembly 200 for receiving a fiber optic cable (not shown). The fiber optic cable may supply the optical beam through the optical focusing lens 212 and onto the terahertz photoconductive antenna 112. In the illustrated embodiment, the fiber optic coupler 240 includes a housing 242 having a front portion 244 and a rear portion 246. The rear portion 246 is generally shaped to receive the fiber optic cable. The front portion 244 includes a collimating lens 248 for collimating the optical beam onto the optical focusing lens 212. As shown, the collimating lens 248 is positioned rearward of the optical focusing lens 212, and thus, the lenses 212, 248 form a compound lens assembly. Furthermore the spacing between the optical focusing lens 212 and the terahertz photoconductive antenna 112 may be selected based upon the focal length of the focusing lens 212. For example, when the focusing lens 212 has a focal length of about 30-mm, the distance between the optical focusing lens 212 and the terahertz photoconductive antenna 112 may also be about 30 mm. Furthermore, the spacing between the focusing lens 212 and the collimating lens 248 may be about 10-mm, although this distance could be greater or smaller. The focal point of the collimating lens 248 may be selected to be located approximately at the tip of the fiber optic cable that is received through the rear opening 124 of the enclosure 110. The above-noted configuration may help collimate and then focus the optical beam onto the terahertz photoconductive antenna 112. In some examples, the optical focusing lens assembly 200 may be movable lengthwise within the enclosure 110 for providing an adjustable distance between the optical focusing lens assembly 200 and the terahertz photoconductive antenna 112. For example, as shown in FIG. 2, the rear portion 123 of the main body 120 may have internal threads (not shown), and the lens housing 210 may have external threads 250 for engaging the internal threads on the rear portion 123 of the tubular main body 120. By allowing lengthwise movement, it is possible to adjust the position the optical focusing lens 212, and thus, focus the optical beam on the terahertz photoconductive antenna 112, and particularly, the terahertz chip dye 140. This enables the optical beam to have an adjustable spot size on the terahertz chip dye 140, which can help transfer optical energy to the terahertz photoconductive antenna 112. In some embodiments, the internal and external threads 250 may have a fine pitch, which may allow micrometer precision adjustment to position the focal point of the optical beam on the terahertz chip dye 140. Referring still to FIGS. 2 and 3, the apparatus 100 may include a middle lock ring 230 and a rear lock ring 232 for securing the optical focusing lens assembly 200 in place within the tubular main body 120. This may help keep the focal point aligned on the terahertz chip dye 140. While the illustrated embodiment includes a focusing lens 212, fiber optic coupler 240, and collimating lens 248, in other embodiments, one or more of these elements may be omitted. For example, in some embodiments, the fiber optic cable may extend through the main body 120 and may be positioned near or in contact with the terahertz chip dye 140, and thus, the focusing lens 212 and collimating lens 248 may be omitted. Furthermore, the fiber optic cable may have a tapered tip, which may help focus the optical beam onto the terahertz chip dye 140 without the use of a separate focusing lens. In other embodiments, the fiber optic coupler 240 may be omitted, for example, when the terahertz photoconductive antenna 112 is energized by a free-space optical beam instead of using a fiber optic cable. In such cases, the focusing lens 212 and collimating lens 248 may still be included within the enclosure 110, or alternatively, outside the enclosure 110. In some embodiments, it may be desirable to optically align the terahertz photoconductive antenna 112 with the optical beam. For example, when using the optical focusing assembly 200 as in the illustrated embodiment, the second set screws 184 can be used to adjust the X-Y position of the antenna mounting structure 132 to align the focal point of the focusing lens 212 on the terahertz chip dye 140. In other embodiments, for example when using a free-space optical beam, the relative position between the enclosure 110 and the free-space optical beam may be adjusted using an external positioning device such as an X-Y translation stage in order to align the free-space optical beam with the terahertz chip dye 140. In some embodiments, the enclosure 110 may be configured to be attached to a standard optical component. For example, the sleeve 128 may be sized and shaped to be received within a standard 1-inch diameter optical mount. Furthermore, while not shown, the sleeve 128 could have external threads for attachment to internally threaded optical mounts. Referring now to FIG. 3, the apparatus 100 may include one or more electrical connectors 270 for connecting the terahertz photoconductive antenna 112 to one or more external electrical devices. For example, the electrical connectors 270 may be coaxial cable connectors such as Sub-Miniature Version-A (SMA) connectors. As shown, the electrical connectors 270 are mounted to an end cap assembly 274, which is secured to the sleeve 128, for example, using fasteners such as screws (not shown). The electrical connectors 270 transmit electrical signals between the terahertz photoconductive antenna 112 and the external electronics. For example, in the illustrated embodiment, there are two electrical connectors 270. When operating as a terahertz receiver, one electrical connector 270 is used to carry an electrical output signal that is proportional to the terahertz wave impinging the terahertz photoconductive antenna 112. The second electrical connector 270 can be used to amplify the output signal. More particularly, with reference to FIG. 4, the apparatus 100 may include a pre-amplifier 280 within the enclosure 110, and the second electrical connector 270 may apply an input voltage bias to the pre-amplifier 280. The pre-amplifier 280 is electrically connected to the terahertz photoconductive antenna 112, and may include one or more electrical components mounted to a circuit board such as operation amplifiers, resistors, and capacitors. FIG. 4 illustrates an exemplary Low Noise Amplifier (LNA) circuit. In other embodiments, the pre-amplifier could have other configurations. In some embodiments, the electrical components of the pre-amplifier may be mounted to the same circuit board 142 as the terahertz dye 140, or alternatively, a separate circuit board mounted within the enclosure 110. In some embodiments, the pre-amplifier 280 may be omitted, or may be located externally from the enclosure 110. In such cases, there may be only one electrical connector 270. Furthermore, when operating as a terahertz transmitter, a single electrical connector 270 can be used. In this case, one electrical connector 270 is coupled to an external power supply in order to apply an input bias voltage to the terahertz photoconductive antenna 112 for generating terahertz waves. Referring now to FIG. 5, the apparatus 100 may include a voltage limit circuit 290, which may help protect the terahertz photoconductive antenna 112 from overvoltage damage when operating as a terahertz transmitter. As shown, the voltage limit circuit 290 is connected to one of the electrical connectors 270 for applying an input voltage. Furthermore, the voltage limit circuit 290 is also connected to the terahertz photoconductive antenna 112 for applying an output voltage to the terahertz photoconductive antenna 112. In the illustrated embodiment, the voltage limit circuit 290 includes a forward biased diode 292, a reverse biased diode 294 connected in series with the forward biased diode 292, and a protective resistor 296. The protective resistor 296 is selected to have a resistance substantially lower than that of the terahertz photoconductive antenna 112. The reverse biased diode 294 is selected to have a break-through voltage approximately equal to the maximum voltage for the terahertz photoconductive antenna 112. As an example, the maximum voltage may be about 15V. In operation, when the input voltage applied is less than the break-through voltage of the reverse biased diode 294 (e.g. less than 15V), the reverse biased diode 294 acts as an open circuit and the input voltage is approximate the same as the output voltage applied to the terahertz photoconductive antenna 112 (provided that the protective resistor 296 has an appropriately low resistance). When the input voltage applied is greater than the break-through voltage of the reverse biased diode 294 (e.g. greater than 15V), some current will flow across both diodes 292, 294 and through the resistor 296. Furthermore, the voltage drop across the diodes 292, 294 will be approximately equal to the break-through voltage of the reverse biased diode 294 (e.g. 15V), and thus the voltage drop across the terahertz photoconductive antenna 112 will be about the same (e.g. 15V), thereby limiting the voltage applied to the terahertz photoconductive antenna 112. Referring now to FIGS. 6 and 7, illustrated therein is an apparatus 600 for transmitting or receiving terahertz waves made in accordance with another embodiment of the present invention. The apparatus 600 is similar in some respects to the apparatus 100 and similar elements are given similar reference numerals incremented by five hundred. For example, the apparatus 600 includes an enclosure 610, a terahertz photoconductive antenna 612 (including a terahertz chip dye 640 and a circuit board 642), a terahertz lens 614, and electrical connectors 770. One difference is that the enclosure 610 includes a main body 620 having a generally square cross-sectional shape. The main body 620 has a front portion 621 with a front opening 622 (shown in the front perspective view of FIG. 6), a rear portion 623 with a rear opening 624 (shown in the rear perspective view of FIG. 7), and an internal passageway that extends between the front opening 622 and the rear opening 624. In this embodiment, the front portion 621 of the main body 620 has a front recessed portion 630 defining a lens mounting structure for mounting the terahertz lens 614 within the enclosure 610. More specifically, the front recessed portion 630 is shaped as a circumferential seat for receiving the hyper-hemispherical terahertz lens 614. Furthermore, the enclosure 610 includes a front cover 632 for holding the terahertz lens 614 against the front recessed portion 630. The front cover 632 has a front opening 634 smaller than the diameter of the terahertz lens 614, while still allowing terahertz waves to be transmitted or received by the terahertz photoconductive antenna 612. The front cover 632 may be secured to the main body 620 using fasteners such as screws 636. The apparatus 600 may also include an O-ring 656 located between the front cover 632 and the terahertz lens 614. Furthermore, as shown in FIG. 7, the front cover 632 may have a beveled rear inner wall 646 that presses the O-ring 656 against the terahertz lens 614. This configuration is generally sufficient to optical align the terahertz photoconductive antenna 612 and the terahertz lens 614 without the use of a position adjustment device such as set screws. In this case, the terahertz photoconductive antenna 612 and the terahertz lens 614 may be pre-aligned during manufacture and assembly within the enclosure 610. Referring still to FIG. 7, the rear portion 623 of the main body 620 has a rear recessed portion 650 defining an antenna mounting structure for mounting the terahertz photoconductive antenna 612 within the enclosure 610. More specifically, the rear recessed portion 650 is a generally square-shaped interior flange located at the end of an interior wall 652 within the main body 620. The terahertz photoconductive antenna 612 may be held against the rear recessed portion 650 using fasteners such as screws 658 that extend through the circuit board 642 and into threaded apertures on the rear recessed portion 650. As shown, the enclosure 610 may include a rear cover 660 secured to the main body 620 using a plurality of fasteners such as screws 662. The rear cover 660 generally has a rear opening 664 therethrough for allowing an optical beam to impinge the terahertz photoconductive antenna. Furthermore, the rear opening 664 may have internal threads 668 configured for attachment to an optical instrument such as another optical component or an optical bench. In other embodiments, the rear cover 660 may have other configurations. For example, the rear cover could be configured to be coupled to a fiber optic cable as will be described with respect to FIG. 8. The main body 620 may also have one or more threaded openings 670 for attachment to optical instruments. As shown, the threaded opening 670 may be located on the top of the main body 620. Furthermore, the apparatus 600 may include an optical adapter 672 that screws into the threaded opening 670 for allowing attachment to optical instruments having a different size than the threaded opening 670. While the optical adapter 672 is shown as providing a reduced diameter threaded opening, other adapters could provide reduced diameter threaded openings. As described above, the apparatus 600 also includes one or more electrical connectors 770 such as SMA connectors. As shown, the electrical connectors 770 extend through apertures 772 on the sides of the main body 620 for electrical connection to the circuit board 642 or other electrical components within the enclosure 110. As shown, the electrical connectors 770 may be secured to the main body 620 using fasteners such as screws 774. Referring now to FIGS. 8 and 9, illustrated therein is an apparatus 800 for transmitting or receiving terahertz waves made in accordance with another embodiment of the present invention. The apparatus 800 is similar in many respects to the apparatus 600 and similar elements are given similar reference numerals incremented by two hundred. For example, the apparatus 800 includes an enclosure 810 having a main body 820 and a front cover 832, a terahertz photoconductive antenna 812 (shown in FIG. 9), a terahertz lens 814, and electrical connectors 970. One difference is that the apparatus 800 includes a fiber optic cable 900 for directing an optical beam onto the terahertz photoconductive antenna 812. Furthermore, the enclosure 610 includes a rear cover 860 that is configured to receive the fiber optic cable 900. More specifically, the rear cover 860 has an opening 862 shaped to receive a strain relief member 910 that is coupled to the fiber optic cable 900. As shown, the strain relief member 910 has a two-piece construction that is configured to clamp onto the fiber optic cable 900. Epoxy or another adhesive may help secure the strain relief member 910 to the cable 900. Furthermore, the strain relief member 910 may have an undercut that allows for expansion of the epoxy during curing. Once attached to the fiber optic cable 900, the strain relief member 910 secures the cable 900 to the enclosure 810, and specifically, the rear cover 860. This can help keep the tip of the cable 900 aligned with the terahertz photoconductive antenna 812. As shown, the strain relief member 910 may have a rear portion 912 of reduced diameter that is shaped to fit within the opening 862 on the rear cover 860. This may be a friction fit in order to secure the strain relief member 910 in place. The strain relief member 910 could also be secured in place using an adhesive such as epoxy. In some embodiments, the strain relief member 910 may be sized and shaped to extend from the rear cover 860 to the circuit board of the terahertz photoconductive antenna 812 and may maintain contact therewith. This may help position the tip of the fiber optic cable 900 longitudinally within the enclosure 810, and thereby align the fiber optic cable 900 with the terahertz chip dye. In such cases, the rear cover 860 may have an interior recessed portion 864 for receiving a portion of the strain relief member 910. Referring now to FIG. 9, the fiber optic cable 900 includes an optical fiber 920 and a rigid jacket 930 wrapped around an optical fiber 920 within the enclosure 810. The jacket 930 may be made from a metal such as stainless steel. The jacket 930 may be added before, during, or after the strain relief member 910 is clamped onto the fiber optic cable 900. In some embodiments, the fiber optic cable 900 may also include a tapered tip 924, which may have an optical focal point aligned on the terahertz chip dye 842 of the terahertz photoconductive antenna 812. As shown, the tapered tip 924 may be spaced apart from the terahertz chip dye 842. Furthermore, the fiber optic cable 900 may include a ferrule 932 between the rigid jacket 930 and the tapered tip 924. Referring now to FIG. 10, illustrated therein is an apparatus 1000 for transmitting or receiving terahertz waves made in accordance with another embodiment of the present invention. The apparatus 1000 is similar in many respects to the apparatus 600 and similar elements are given similar reference numerals incremented by four hundred. For example, the apparatus 1000 includes an enclosure 1010 (including a main body 1020, a front cover 1032, and a rear cover 1060), a terahertz photoconductive antenna 1012, a terahertz lens 1014, and electrical connectors 1170. One difference is that the enclosure 1010 is generally larger than the enclosure 610 of the apparatus 600. Specifically, the enclosure 1010 is about twice the size of the enclosure 610. For example, the enclosure 610 may be about 1-inch by 1-inch, and the enclosure 1010 may be about 2-inches by 2-inches. Having different sizes enables attachment to various types of terahertz transmission or detection systems. Another difference is that the front portion 1021 of the main body 1020 has an outer peripheral flange 1050 that defines an interior recess sized and shaped to receive the front cover 1032 therein. While not shown, the rear portion of the main body 1020 may also have an outer peripheral flange that defines an interior recess sized and shaped to receive the rear cover 1060 therein. This may provide a slim profile without exposed edges. One or more of the embodiments described herein are capable of integrating THz-PCAs, terahertz lenses (e.g. hyper-hemispherical silicon lenses), and other optical components (such as optical lenses and optical fibers) within a single enclosure package. The enclosure is generally configured to optically align the THz-PCA and the terahertz lens, and thus, may allow for optimum operation. The enclosure may enable assembly of components in a repeatable and accurate fashion while also being simple and inexpensive. In some cases, the enclosure may be ruggedized and may withstand breakage during normal usage, particularly for industrial applications. In some cases, the enclosure may be sealed, for example, using O-rings. This may provide resistance to damage from water, dust, or other elements that are sometimes present within industrial environments. While the above description provides examples of one or more apparatus, methods, or systems, it will be appreciated that other apparatus, methods, or systems may be within the scope of the present description as interpreted by one of skill in the art.
047708476
claims
1. A nuclear fuel assembly comprising water rods and fuel rods having substantially equivalent irradiation growth wherein: the fuel rods comprise cladding tubes of a zirconium alloy formed by a first tube fabrication schedule wherein the final dimensions are achieved by cold-work reduction followed by heat treating the tube for about 1 to about 15 hours at about 1000.degree. F. to about 1300.degree. F.; and the water rods comprise cladding tubes of a zirconium alloy substantially the same as in the fuel rod cladding tubes and formed by a second tube fabrication schedule wherein the final dimensions are achieved by cold-work reduction followed by heat treating the tube for about 1 to about 4 hours at about 825.degree. F. to about 950.degree. F. the fuel rods comprise cladding tubes of a zirconium alloy formed by a first fabrication schedule wherein the final dimensions are achieved by about a 76% cold-work reduction in the thickness of the cladding wall followed by heat treating the tube for about 2.5 hours at about 1070.degree. F.; and the water rods comprise cladding tubes of a zirconium alloy substantially the same as in the fuel rod cladding tubes formed by a second fabrication schedule wherein the final dimensions are achieved by about a 20% cold-work reduction in the thickness of the cladding tube wall followed by heat treating the tube for about 4 hours at about 950.degree. F. 2. A nuclear fuel assembly as recited in claim 1 wherein the fuel rod cladding tube is heat treated for about 1 to about 4 hours at about 1000.degree. F. to about 1300.degree. F. 3. A nuclear fuel assembly as recited in claim 1 wherein the select cold-work reduction in the second tube fabrication schedule comprises about a 20 percent reduction in the thickness of the tube wall. 4. A nuclear fuel assembly comprising water rods and fuel rods having substantialy equivalent irradiation growth wherein:
summary
claims
1. A portable X-ray scanner, comprising:a digital X-ray detector, comprising:a scintillation screen;a reflector configured to reflect light generated by the scintillation screen, wherein the reflector and the scintillation screen are arranged at substantially a 30 degree angle; anda digital imaging sensor configured to generate digital images of the light reflected by the reflector, wherein a thickness of the digital X-ray detector is less than 2.5 inches;an X-ray tube configured to output X-ray radiation toward the scintillation screen;a frame configured to hold the X-ray detector and the X-ray tube;a handle couple to the frame and configured to enable a single user to position the X-ray detector and the X-ray tube while carrying the frame during output of the X-ray radiation; anda trigger coupled to the frame on a same side of the frame as the X-ray tube and configured to enable the user carrying the frame to control output of the X-ray radiation. 2. The portable X-ray scanner as defined in claim 1, further comprising a trigger configured to control the X-ray tube to output the X-ray radiation in response to user input. 3. The portable X-ray scanner as defined in claim 1, further comprising a housing coupled to the frame and configured to hold the scintillation screen and the reflector. 4. The portable X-ray scanner as defined in claim 1, further comprising a bracket configured to adjust an angle of the digital imaging sensor with respect to the reflector. 5. The portable X-ray scanner as defined in claim 1, further comprising a display device configured to display the digital images. 6. The portable X-ray scanner as defined in claim 5, wherein the display device is configured to display the digital images in real-time. 7. The portable X-ray scanner as defined in claim 1, wherein the display device is configured to receive the digital images via wireless communications. 8. The portable X-ray scanner as defined in claim 1, further comprising at least one of a reflective element or a refractive element to direct the light between the scintillation screen and the digital imaging sensor.
044302568
summary
BACKGROUND OF THE INVENTION The disposal of large quantities of toxic materials such as high level radioactive wastes stored in spent reactor storage pools, or generated in the reprocessing of spent nuclear reactor fuel, or generated in the operation and maintenance of nuclear power plants, is a problem of considerable importance to the utilization of nuclear power. It is generally accepted that the most promising approach is to convert these radioactive wastes to a dry solid form which would render such wastes chemically and thermally stable. The problem of dry solid stability of radioactive wastes is related to the safety of human life on earth. For example, radioactive wastes usually contain the isotopes Sr.sup.90, Pu.sup.239, and Cs.sup.137 whose half lives are 28 years, 24,000 years, and 30 years, respectively. These isotopes alone pose a significant threat to life and must be put into a dry, solid form which is stable for thousands of years. Any solid radioactive waste package must be able to keep the radioactive isotopes immobilized for this length of time, preferably even in the presence of an aqueous environment. The radioactive wastes are produced in high volumes and contain long-lived, intermediate-lived, and short-lived radioactive ions and some non-radioactive ions. The two most popular types of commercial reactors, both of which produce low level wastes, are the Boiling Water Reactor (B.W.R.) and the Pressurized Water Reactor (P.W.R.). In a typical Pressurized Water Reactor (P.W.R.), pressurized light water circulates through the reactor core (heat source) to an external heat sink (steam generator). In the steam generator, where primary and secondary fluids are separated by impervious surfaces to prevent contamination, heat is transferred from the pressurized primary coolant to secondary coolant water to form steam for driving turbines to generate electricity. In a typical Boiling Water Reactor (B.W.R.), light water circulates through the reactor core (heat source) where it boils to form steam that passes to an external heat sink (turbine and condenser). In both reactor types, the primary coolant from the heat sink is purified and recycled to the heat source. The primary coolant and dissolved impurities are activated by neutron interactions. Materials enter the primary coolant through corrosion of the fuel elements, reactor vessel, piping, and equipment. Activation of these corrosion products adds radioactive nuclides to the primary coolant. Corrosion inhibitors, such as lithium, are added to the reactor water. These chemicals are activated and add radionuclides to the primary coolant. Fission products diffuse or leak from fuel elements and add nuclides to the primary coolant. Radioactive materials from all these sources are transported around the system and appear in other parts of the plant through leaks and vents as well as in the effluent streams from processes used to treat the primary coolant. The mitigation of these normal engineering process leaks gives rise to a substantial volume of low and intermediate level wastes. On the other hand, the dissolution in nitric acid of the spent nuclear reactor fuel generates the so-called "high level radioactive nuclear waste liquids" which must eventually be solidified. Both of these types of radioactive wastes--high and low level--present problems in regard to transportation, disposal, storage, and immobilization of the same. The present invention is directed to a novel article, i.e., a secondary "container" or retarder for containerizing and storing radioactive solids primarily containing cesium, strontium, and actinide ions as well as novel processes for making such "containers" and storing such radioactive solids. SUMMARY OF THE INVENTION Up to the present time, all buffer materials have been designed to be "inert," or absorptive of the dangerous radionuclides chiefly Cs, Sr, and Actinides, but including all the normal fission product ions, I, Tc, etc. The buffer materials proposed have been rather generally quartz, clays (typically bentonite) and zeolites (and including FeSO.sub.4 as an Eh buffer). The present invention starts with a very different concept. The concept is the use, for example, of non-radioactive Cs, Sr, I, Mn, and Ln (lanthanide) in higher concentration than the same or analogous elements in the waste as a positive-action buffer. By this is meant that any reactions of the waste with the buffer will take place in a gradient of concentration that will be inward towards the waste form with respect to the most threatening nuclides. To achieve this, the present invention provides an overpack containing material with a higher chemical activity of Sr, Cs, and Ln or the like in the solid or in any solution in equilibrium with both waste and overpack. Typical materials which may be employed for such overpacks include, for example, the Cs and Sr containing aluminosilicates (including clays, zeolites, feldspars) and Cs, Sr, Ln aluminates and silicates, as well as carbonates, sulfates, and titanates where appropriate. The phases desirably are near to thermodynamic equilibrium with each other and with the radiophase(s) of the waste form. The ideal is to have the activity of each of the cold nuclides just slightly (say one order of magnitude) higher in contact with the overpack than the waste. Examples of Positive Chemical Buffers for nuclear waste canisters include: (a) Mixtures of CsAlSiO.sub.4, Sr-feldspar, Ln silicate. PA1 (b) Mixture of fixed (i.e., heated) Cs-vermiculite; Sr-wairakite+Ln-stabilized Y-zeolite+Pb-I zeolite. PA1 (c) Mixture of fixed Cs-chabazite; SrCO.sub.3 ; CePO.sub.4 ; pyrolusite.
062663925
description
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the soller slit according to the present invention will be described. Before describing the soller slit of the present invention in detail, the utilization of the soller slit will be described briefly. FIG. 5 illustrates a focusing type X-ray optical system that is an example of utilization of the soller slit. The X-ray optical system includes an X-ray focus `F` of a line type generating X-rays, a specimen `S` to be measured and an X-ray counter 1 for detecting X-rays diffracted by the specimen `s`. An incident side soller slit 2 and a divergence limiting slit 3 are arranged in the order between the X-ray focus `F` and the specimen `s`. A scatter limiting slit 4, a receiving side soller slit 6 and a receiving slit 7 are arranged in the order between the specimen `S` and the X-ray counter 1. Divergent X-rays generated from the X-ray focus `F` are directed to the incident side soller slit 2 to restrict divergence thereof in a vertical direction, that is height direction. The X-rays are subsequently incident on the divergence limiting slit 3 by which divergence thereof in a horizontal direction, that is width direction, is restricted. Then, the X-rays whose vertical and horizontal divergences are thus restricted are directed to the specimen `S`. When Bragg's diffraction condition is satisfied between crystal lattice plane of the specimen `S` and the incident X-rays, the X-rays are diffracted by the specimen `S`. X-rays diffracted by the specimen `S` passes through the scatter limiting slit 4 to remove scattered component thereof, and then through the receiving side soller slit 6 to limit divergence thereof in the height direction. Then, the diffracted X-rays are focused on the receiving slit 7. Portions of the focused diffracted X-rays that fall in areas defined by the receiving slit 7 passes therethrough and are received by the X-ray counter 1 to thereby calculate an intensity of X-rays. In the X-ray measurement mentioned above, it has been known that, when an X-ray component diverging in the height direction is taken in the X-ray counter 1, the so-called umbrella effect occurs, with which resolution is degraded. In order to avoid the degradation of resolution, the soller slits 2 and 6 prevent such X-ray component diverging in the height direction from being taken in the X-ray counter 1. FIG. 6 is a plan view of a parallel X-ray beam optical system that is another example of the utilization of the soller slit. This X-ray optical system includes an X-ray focus `F` of a line type generating X-rays, a specimen `S` to be measured and the X-ray counter 1 for detecting X-rays diffracted by the specimen `S`. An incident side soller slit 2 is arranged between the X-ray focus `F` and the specimen `S`. A receiving side soller slit 6 is arranged between the specimen `S` and the X-ray counter 1. Divergent X-rays generated from the X-ray focus `F` are transformed into parallel beams by the incident side soller slit 2 and is incident on the specimen `S`. X-rays diffracted by the specimen `S` is received in the X-ray counter 1 while its divergence is restricted by the receiving soller slit 6. And then, intensity of X-rays is calculated. The receiving side soller slit 6 functions to improve resolution in the X-ray measurement by restricting the divergence of X-rays diffracted by the specimen `S`. In the focusing type optical system shown in FIG. 5 and in the parallel beam optical system shown in FIG. 6, the incident side soller slit 2 is formed by laminating a plurality of metal foils 9 with interposing spacers 8 as shown in FIG. 1. This is also true for the receiving side soller slit 6. When diverging incident X-rays R1 are incident on the soller slit 2 or 6, divergence thereof in a vertical direction is restricted, resulting in parallel X-rays R2 on the receiving side. By rotating the soller slit 2 or 6 by an angle of 90.degree., it is possible to obtain parallel X-ray beams having a width in the lateral direction. As one of the optical characteristics of the soller slit 2 and 6, there have been known an opening angle .phi. shown in FIG. 2, which is defined by the following formula: EQU .phi.=2.times.tan.sup.-1 (t/L) where "L" is a length of the metal foil 9 and "t" is a gap between adjacent metal foils 9. The opening angle .phi. is an important element for defining the resolution of the X-ray optical system utilizing the soller slit. In this example, sintering a metal material such as tungsten (W) or molybdenum (Mo) forms the metal foils 9 of the soller slits 2 and 6. The total reflection of X-rays passing through the soller slits 2 and 6 is restricted by utilizing roughness of the surfaces of the metal foils, which is naturally provided by the sintering. According to the currently usable sintering processing, it is possible to effectively form a desired high harmonic surface roughness, that is, surface roughness having space period of, for example, not larger than 50 .mu.m, preferably 20.about.50 .mu.m, and having RMS value of, for example 20 nm.about.1 .mu.m, preferably 20.about.50 nm, on the material surfaces. The high harmonic surface roughness is very effective to restrict total reflection of X-rays. By restricting total refection of X-rays in this manner, it is possible to improve resolution in the X-ray measurement. Alternatively, the metal foils 9 of the soller slits 2 and 6 may be formed by using oxidized stainless steal or brass (Cu: Zn=5: 1), with improved resolution of the X-ray measurement. When stainless steal foil is oxidized, oxide material is formed on surfaces of the stainless steal foil, with which surface roughness having space period of, for example, not larger than 50 .mu.m, preferably 20.about.50 .mu.m, and having RMS value of, for example, 20 nm.about.1 .mu.m, preferably 20.about.50 nm, can be effectively formed on surfaces of the stainless steal foil. The high harmonic surface roughness is very effective to restrict total reflection of X-rays as mentioned previously. By restricting total reflection of X-rays in this manner, it is possible to improve resolution in the X-ray measurement. Embodiments of the soller slit according to the present invention will be described in detail. First Embodiment Metal foils 9 were prepared from tungsten plate formed by sintering and a soller slit 2 or 6 was fabricated by using the metal foils 9. Besides, metal foils 9 were prepared from a rolled stainless steal plate and a rolled brass plate. Further soller slits 2 or 6 of a prior art were fabricated by using the metal foils 9 and the brass foils 9, respectively. FIG. 3 shows X-ray intensity vs. diffraction angle characteristics curves obtained X-ray measurement performed using X-ray optical systems constructed with using the respective three soller slits. In this measurement, a peak broadening that is defined by FWHM (full width of half-maximum) intensity and a tailing is investigated. Incidentally, the term "tailing" means a width of a bottom portion T in the characteristic curve shown in FIG. 3. It was observed that the peak broadening was substantially smaller in the case (curve A) where the soller slit fabricated by sintering tungsten is used, compared with the cases where the soller slits fabricated by using the rolled stainless steal (curve B) and the rolled brass (curved C). This means that resolution when the soller slit fabricated by sintering tungsten is used is highest. Second Embodiment Metal foils 9 shown in FIG. 1 were prepared by the conventional method utilizing a rolled brass (Cu: Zn=5: 1) and then, soller slits 2 and 6 were fabricated by using the metal foils 9. Subsequently, an X-ray measurement was performed with using an X-ray optical system constructed by using of the soller slits thus formed. FIG. 4 shows an X-ray intensity vs. diffraction angle characteristic curve D obtained by an X-ray measurement performed with using X-ray optical systems constructed by using of the soller slits. Thereafter, the metal foils 9 of the soller slits 2 and 6 were disassembled from the latter and oxide material is formed on the surfaces of the metal foils 9 by oxidizing the latter with using dense nitric acid. Then, the oxidized metal foils 9 were re-assembled in the soller slits 2 and 6 and an X-ray measurement was performed with using thus re-assembled soller slits 2 and 6. The characteristic curve E shown in FIG. 4 is a result of the X-ray measurement. As compared the characteristic curve E corresponding to the oxidized metal foils and the characteristic curve D corresponding to the metal foils which are not oxidized, it is clear that the characteristic curve E is superior to the characteristic curve D in the peak broadening specified with both FWHM value and tailing. That is, when the soller slits fabricated by using the oxidized metal foils are employed, resolution of the X-ray measurement can be improved substantially. Other Embodiment Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited thereto and can be modified or changed variously within the scope of the present invention defined by the appended claims. For example, the soller slit according to the present invention can be applied to other X-ray optical system than the X-ray optical system shown in FIGS. 5 and 6. Further, the structure of the soller slit is not limited to that shown in FIG. 1 and can be any structure provided that the metal foils are arranged with a predetermined space between adjacent ones. For example, the spacers are not always arranged on both sides of each metal foil. It is possible to arrange the spacer on one side of each metal foil.
051749505
description
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS As indicated above, a grid according to the invention can be used in a fuel assembly having a hexagonal cross-section with two sub-structures, such as the assembly 10 shown in FIG. 1, in which only some fuel rods 14 have been shown. The support structure has two end pieces, an upper end piece 16 and a lower end piece 18, and guide tubes 20 and 24 replacing the rods at certain nodal points of the network of rods. The first sub-structure comprises the guide tubes 20, upper end piece 16 and a plate 23 movable within the lower end piece 18. The guide tubes pass through the bottom wall 22 of the end piece 18, in which they are vertically slidable. The first sub-structure further comprises the uppermost grid 12, which is intended to carry the fuel rods 14, and for this purpose is provided with means for clamping the fuel rods, i.e., some at least of the intermediate grids 13. The lowermost grid may also be fixed to the guide tubes 20. The connections of the guide tubes 20 of the first sub-structure, of grid 12 and of the bottom wall of the upper end piece 16 are shown by crosses in FIG. 1. The second sub-structure comprises the lower end piece 18, the other guide tubes 24 and a plate 28 movable vertically in the frame portion of the upper end piece 16, above the bottom wall 22 of piece 16. The guide tubes 24 pass through the bottom wall and are slidable therein. The second sub-structure may also comprise a central instrumentation tube 29. Springs 30, four in number for example, are placed between the plate 23 and a flange 32 formed at the lower part of the frame of the lower end piece 18. The springs exert a force on plate 23 tending to hold it applied against the bottom wall of plate 18. Rods 34 fixed to the lower end piece 18 guide the springs 30 and the plate 23. The fuel assemblies have been loaded in the reactor, the lower end piece 18 of each assembly rests on the core support plate 36. Springs 30 support the first sub-structure and hold plate 23 in position. When the upper core plate 38 is lowered, the pressure which it exerts on the upper end piece 16 is added to the weight of the first sub-structure. When the reactor is operating, the coolant exerts on the first sub-structure a force which tends to apply the upper end piece 16 against the upper core plate 38. The force which the coolant exerts on the second sub-structure, much smaller than that which it exerts on the first sub-structure, is absorbed by springs 30 without raising the lower end piece 18. The intermediate grids 13, for holding the rods in position at the nodal points of a triangular network, may be devoid of springs for supporting the rods and may have the construction shown in FIGS. 2 and 3. Each grid is formed by assembling together a plurality of sets of plates which are all made from an alloy having a low neutron absorption, generally a zirconium-base alloy. The grid 13 may be regarded as comprising a belt 40 and plates defining cells for receiving respective fuel rods 14, only one of which is shown schematically in FIG. 2. The belt may be formed b a metal strip of zirconium-base alloy which is bent into a hexagonal shape, or by strip sections each having a length equal to that of one side of the belt, the sections being joined together by welding, for example by electron beam or laser beam welding. To reduce the number of types of components, it is however more advantageous to form the belt of three plates 42 having the same shape as the internal plates 44, to which the internal plates are welded or brazed. The internal plates 44, 46 and 48 belong to three sets crossed at 120.degree. with respect to each other. All plates extend between two opposite faces of the belt and are angled at 120.degree. in the middle. They will in general form a single bed, obtained interlocking plates 44, 46 and 48. To this end, slits 49 whose length is equal to half the width of the plates are formed in the latter. One at least of the sets of plates 44, 46 and 48 has slits directed in opposite directions on opposed sides of the medium bend of the plate. As illustrated, plates 44 are inserted on plates 46 and 48 already assembled. Once interlocked, the plates are secured permanently together, for example by welding points at the intersections, using well-known techniques. For correct positioning of plates 44, 46 and 48 of the belt, the plates 42 which form the latter may comprise openings 51 receiving lugs (not shown) projecting from the end edges of plates 44, 46 and 48. As mentioned above, the plates may be provided with means for bearing rigidly or resiliently on the rods. Such bearing means may be embossments formed by press-shaping the plates, e.g., tongues press-cut and shaped or may be springs, which makes it possible to form a grid having plates of zirconium-base alloy and springs of "Inconel", having greater mechanical strength but on the other hand higher neutron absorption. The plates (or at least the internal plates 44, 46 and 48) may have a shape corrugated at the distribution spacing of the fuel rods when it is desired to reduce the spacing pitch. Bosses may be provided on all types of cells (diamond-shaped, herringbone, hexagonal). Support is less essential for the central hexagonal cell, for it is generally for an instrumentation tube. FIGS. 4A, 4B, 4C and 4D show, as examples, different bosses which may be used, formed by stamping and local pressing of the plates, in the form of buttons 50 (FIGS. 4A and 4D) or bridges 52 (FIGS. 4B and 4D). Bosses 50 may be provided on the wall of the central hexagonal cell for centering the instrumentation tube 56 (FIG. 4C). The cells may be provided with means for holding the rods axially in position, which means are formed by springs added to the plates or stamped in the plates, as in the case of conventional grids. The hexagonal cell shown schematically in FIGS. 5A and 5B comprises, in addition to bosses 52, a spring 58 formed by stamping a leg in a plate, shaping the stamped leg and end welding it at 60. Spring 58 could also be added. FIG. 6 shows a herringbone cell comprising two bosses 50 and two springs 58 which are added or formed by stamping. In all cases, the presence of spot welds or of a welding bead increases the mechanical strength of the grid. In still another embodiment, shown in FIG. 7, a fuel rod 14 is held in position by springs 60 having the same form as the bridge-shaped bosses 52, but cut out. The same type of spring could be used in herringbone cells. In most assemblies, some at least of the grids are provided with fins for mixing the coolant streams. The diamond-shaped cells as well as the herringbone cells of a grid in accordance to the invention may be thus equipped. FIG. 8 shows, by way of example, a diamond-shaped cell having two fins 62 formed as lugs attached to the plates, on one edge thereof, and bent. The area of such fins 62 may be greater than that found in grids where each cell is hexagonal, because the available space between the rod and the plate is greater. Such fins may be provided on cells also having bosses and/or springs for centering and/or holding the rods. FIG. 9 shows, by way of example, the orientation and flow of the fluid streams obtained using fins of the kind shown in FIG. 8. It will generally be advantageous to offset two successive grids 13 angularly by 60.degree., so that the fuel rods of a radial slow towards a corner of the grid, are alternately supported in a diamond-shaped cell and supported in a herringbone shaped cell.
abstract
The invention is concerned with a microlithography projection objective device for short wavelength microlithography, preferably less than 100 nm, with a first mirror (S1), a second mirror (S2), a third mirror (S3), a fourth mirror (S4) and a fifth mirror (S5). The invention is characterized by the fact that the image-side numerical aperture (NA) is greater than or equal to 0.10 and that the mirror closest to the object to be illuminated, preferably the wafer, is arranged in such a way that the image-side optical free working distance corresponds at least to the used diameter (D) of the mirror closest to the wafer; the image-side optical free working distance is at least the sum of one-third of the used diameter (D) of the mirror closest to the wafer and a length which lies between 20 mm and 30 mm; and/or the image-side optical free working distance is at least 50 mm, preferably 60 mm.
claims
1. A method to estimate scattered radiation contained in x-ray projections for computed tomography (CT) reconstruction, comprising:constructing an object model based on a plurality of projection images generated by CT scanning of an object using an x-ray radiation source and a detector panel, wherein the object model contains a plurality of voxels, and the constructing of the object model comprises assigning each of the plurality of voxels to at least one material type with density based on each of the plurality of voxels' Hounsfield Units (HU) value;constructing a virtual radiation source based on the x-ray radiation source;constructing a virtual detector panel based on the detector panel;performing a simulated CT scanning of the object model by simulating macroscopic behavior of particles being emitted from the virtual radiation source, passing through the object model, and being detected by the virtual detector panel;constructing a Boltzmann Transport Equation (BTE) for a first subset of particles scattered during the simulated CT scanning of the object model;using a deterministic method to solve the BTE and calculate the corresponding particle fluence distribution values in the plurality of voxels; andgenerating a simulated scatter image based on the corresponding particle fluence distribution values in the plurality of voxels. 2. The method as recited in claim 1, further comprising:estimating a scatter-reduced image corresponding to one of the plurality of projection images based on the simulated scatter image; andreconstructing a CT object volume with reduced scatter artifacts based on the scatter-reduced image. 3. The method as recited in claim 2, wherein the estimating of the scatter-reduced image comprising:generating a simulated primary image based on a second subset of particles attenuated but not scattered during the simulated CT scanning of the object model;generating a gain map based on the simulated primary image and the simulated scatter image; andestimating the scatter-reduced image by adjusting the plurality of projection images based on the simulated scatter image and the gain map. 4. The method as recited in claim 2, wherein the estimating of the scatter-reduced image comprising:estimating the scatter-reduced image by adjusting one of the plurality of projection images using subtraction or perturbation based on the simulated scatter image. 5. The method as recited in claim 1, wherein the plurality of projection images are generated using a bowtie filter, and the performing of the simulated CT scanning of the object model further comprising:constructing a virtual bowtie filter based on the bowtie filter; andsimulating the macroscopic behavior of the particles passing through the virtual bowtie filter after being emitted from the virtual radiation source. 6. The method as recited in claim 1, wherein the plurality of projection images are generated using an anti-scatter grid, and the performing of the simulated CT scanning of the object model further comprising:constructing a virtual anti-scatter grid based on the anti-scatter grid; andsimulating the macroscopic behavior of the particles passing through the virtual anti-scatter grid before being detected by the virtual detector panel. 7. The method as recited in claim 1, wherein the constructing of the object model comprising:constructing a virtual patient table into the object model. 8. The method as recited in claim 7, wherein the constructing of the object model further comprising:extending the object model in its axial direction or longitudinal direction to account for truncation occurred during the CT scanning. 9. The method as recited in claim 1, wherein the performing of the simulated CT scanning of the object model by simulating of the macroscopic behavior of particles comprising:simulating the particles emitted from the virtual radiation source, passed through the plurality of voxels, and detected by a plurality of virtual pixels in the virtual detector panel; andidentifying the first subset of particles scattered during the simulating of the particles. 10. The method as recited in claim 9, wherein the simulating of the particles comprising:transporting the particles emitted from the virtual radiation source through the plurality of voxels to calculate a set of scattering sources;transporting the particles from the set of scattering sources across the plurality of voxels;iterating through the calculation of scattering sources and transporting of the particles; andtransporting the particles from the plurality of voxels to the plurality of pixels in the virtual detector panel. 11. The method as recited in claim 1, further comprising:ray-tracing the first subset of particles from the virtual radiation source to the object model prior to the constructing of the BTE; andray-tracing the first subset of particles from the object model to the virtual detector panel after the constructing of the BTE. 12. The method as recited in claim 1, wherein the spatial resolution of the plurality of pixels in the virtual detector panel is coarser than pixels in the detector panel, and the generating the simulated scatter image based on the corresponding particle fluence distribution values in the plurality of pixels further comprising:using interpolation to up-sample the simulated scatter image to match spatial resolution of one of the plurality of the projection images. 13. A method to determine scattered radiation contained in x-ray projections for computed tomography (CT) reconstruction, comprising:reconstructing a first CT volume based on a plurality of projection images generated by CT scanning of an object using an x-ray radiation source and a detector panel;constructing an object model based on the CT volume, wherein the object model contains a plurality of voxels, and the constructing of the object model comprises assigning each of the plurality of voxels to at least one material type with density based on each of the plurality of voxels' Hounsfield Units (HU) value;constructing a virtual CT scanning environment having a virtual radiation source based on the x-ray radiation source and having a virtual detector panel based on the detector panel, wherein the virtual detector panel contains a plurality of virtual pixels;performing a simulated CT scanning of the object model by simulating macroscopic behavior of particles being emitted from the virtual radiation source, passing through the object model, and being detected by the virtual detector panel;generating a plurality of simulated scatter images corresponding to the plurality of projection images by estimating a first subset of particles scattered during the simulated CT scanning of the object model, wherein each simulated scatter image in the plurality of simulated scatter images is generated byconstructing a Boltzmann Transport Equation (BTE) for the first subset of particles scattered during the simulated CT scanning of the object model,using a deterministic method to solve the BTE and calculate corresponding particle fluence distribution values in the plurality of voxels, andgenerating the simulated scatter image based on the corresponding particle fluence distribution values in the plurality of voxels; andreconstructing a second CT volume with reduced scatter artifacts based on the plurality of projection images and the plurality of simulated scatter images. 14. The method as recited in claim 13, wherein a first subset of the plurality of simulated scatter images are calculated based on a subset of the plurality of projection images, and a second subset of the plurality of simulated scatter images are interpolated based on the calculated first subset of the plurality of simulated scatter images. 15. The method as recited in claim 13, wherein the x-ray radiation source has a Cone-beam CT (CBCT) geometry and the detector panel is a flat panel. 16. The method as recited in claim 13, whereingenerating the each simulated scatter image in the plurality of simulated scatter images further comprises:ray-tracing the first subset of particles from the virtual radiation source to the object model prior to the constructing of the BTE. 17. The method as recited in claim 16, wherein generating the each simulated scatter image in the plurality of simulated scatter images further comprises:ray-tracing the first subset of particles from the object model to the virtual detector panel after the constructing of the BTE. 18. A scatter-estimation system configured to estimate scattered radiation contained in x-ray projections for computed tomography (CT) reconstruction, comprising:a scan-simulation module configured toconstruct an object model based on a plurality of projection images generated by CT scanning of an object using an x-ray radiation source and a detector panel, wherein the object model contains a plurality of voxels, and the construction of the object model comprises assigning each of the plurality of voxels to at least one material type with density based on each of the plurality of voxels' Hounsfield Units (HU) value,construct a virtual radiation source based on the x-ray radiation source,construct a virtual detector panel based on the detector panel, andperform a simulated CT scanning of the object model by simulating macroscopic behavior of particles being emitted from the virtual radiation source, passing through the object model, and being detected by the virtual detector panel; andan image-correction module coupled with the scan-simulation module, wherein the image-correction module is configured togenerate a simulated scatter image byconstructing a Boltzmann Transport Equation (BTE) for a first subset of particles scattered during the simulated CT scanning of the object model,using a deterministic method to solve the BTE and calculate corresponding particle fluence distribution values in the plurality of voxels, andgenerating the simulated scatter image based on the corresponding particle fluence distribution values in the plurality of voxels, andestimate a scatter-reduced image corresponding to one of the plurality of projection images based on the simulated scatter image. 19. The scatter-estimation system as recited in claim 18, wherein the plurality of projection images are generated using a bowtie filter and an anti-scatter grid, and the scan-simulation module is further configured to:construct a virtual bowtie filter based on the bowtie filter;construct a virtual anti-scatter grid based on the anti-scatter grid; andsimulating the macroscopic behavior of the particles passing through the virtual bowtie filter and the virtual anti-scatter grid before being detected by the virtual detector panel.
summary
summary
summary
description
The present application is a continuation of U.S. patent application Ser. No. 15/288,436 filed Oct. 7, 2016, which is a continuation of U.S. patent application Ser. No. 14/417,628 filed Jan. 27, 2015, which claims priority as a national stage application, under 35 U.S.C. § 371, to international application No. PCT/US2013/053644, filed Aug. 5, 2013, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/680,133, filed Aug. 6, 2012. The disclosures of the aforementioned priority applications are incorporated herein by reference in their entireties. The present invention relates to control rod drive systems for nuclear reactors, and more particularly to a fail-safe control rod drive system. A rod cluster control assembly (RCCA) comprises an array of tubular elements (“control rods”) containing neutron absorber “poison” connected to a common support header for raising and lowering the control rod array as a unit. The control rods in an RCCA are arrayed at a precise spacing, which ensures each rod is perfectly aligned with respective circular cavities in the fuel assemblies of the fuel core. The extent of insertion of the rod assembly into the fuel core is controlled by the device referred to as a control rod drive mechanism (CRDM), which is a subcomponent of the control rod drive system (CRDS). In typical pressurized light water reactors (PLWRs), the CRDM is operated from the top of the reactor head which is approximately 15 to 20 feet above the top of the nuclear fuel core. However, in certain new reactor systems, the height of the reactor head may be many times greater above the top of the fuel core. For example, in the HI-SMUR™ SMR-160 from Holtec International, the RCCAs may require operation from a distance of over 60 feet, which using the present existing technology, would require the drive rod (DR) which is normally supplied with existing CRDM to be in excess of 60 feet long. DRs with such a long length, however, would be impractical for the following reasons: Removing drive rods from the reactor vessel would require an inordinate amount of crane head room; Performing routine maintenance would require a large laydown area; The weight of the drive rod becomes so large due to the increased length, that during a SCRAM (emergency shutdown procedure of the reactor in which control rod are quickly inserted into the fuel core to suppress the nuclear reaction), the top nozzle of the fuel assembly risks becoming damaged from the weight of the falling RCCA as well as the ESA; During a SCRAM, the drive rod is at risk of being damaged because of the inertia load, which is magnified in the CRDM which utilizes a lead screw for the drive rod; and Manufacture of drive rod becomes difficult thereby increasing the cost to fabricate the CRDS. Another problem is presented by the location of the CRDM. Contemporary commercial technology requires the CRDM to be installed External to the Reactor Vessel. This presents major concerns with regards to the operational safety of the CRDS. With presently available technology should a failure of the pressure retaining portion of the CRDM occur the pressure differential between the inside of the reactor vessel and the atmosphere external to the reactor vessel would subsequently cause the CRDM drive rod to be ejected from the reactor. This in turn could cause a spike in the reactivity of the reactor core, since the drive rod is mechanically connected to the RCCA in the current state-of-the-art technology. One solution would be to locate CRDM within the reactor vessel. However, this would pose several technical challenges. First, control rod drive mechanisms are complex electromechanical devices. Exposing these to the high pressure and temperature environment inside the reactor vessel can cause the mechanism to fail prematurely. Second, placing the control rod drive mechanism inside the reactor vessel presents possibly structural problems since the mechanism is also subject to flow induced vibration. Accordingly, although this approach would solve the long drive rod problem, it is undesirable for the foregoing reasons. An improved control rod drive system is desired. The present invention provides a control rod drive system (CRDS) that overcomes the foregoing problems and yields a number of additional benefits, which will be readily discerned from the description which follows. The present invention may be beneficially used for nuclear reactor vessel designs of a high head design described above (e.g. top of the reactor head located at a vertical distance greater than approximately 15 to 20 feet above the top of the nuclear fuel core), but has broader application as well to virtually any reactor vessel design. In one configuration, a control rod drive system (CRDS) generally includes a drive rod mechanically coupled to a control rod drive mechanism operable to linearly raise and lower the drive rod along a vertical axis, a rod cluster control assembly (RCCA) comprising a plurality of control rods positioned proximate to and insertable into a nuclear fuel core, and a drive rod extension (DRE) releasably engaged between the drive rod and RCCA. The CRDS is remotely operable to selectively couple and uncouple the DRE from the RCCA and drive rod. The CRDM includes an electromagnet which releasably couples the CRDM to DRE. This arrangement contrasts to known CRDSs in which the drive rod is directly coupled to the RCCA, which is unsuitable in situations requiring drive rods with excessively long lengths (e.g. greater than 15-20 feet). In the event of a power loss or SCRAM, the CRDM may be configured to remotely uncouple the RCCA from the DRE without releasing or dropping the drive rod which remains engaged with the CRDM and in axial position. Advantageously, this protects the integrity of the CRDM and eliminates potential problems with known designs caused by dropping the drive rod which may damage equipment, as described above. The present DRE includes unique features providing the remote coupling and uncoupling functionality, and failsafe operation in the event of a power loss or SCRAM, as further described herein. According to one exemplary embodiment of the present invention, a control rod drive system for a nuclear reactor vessel includes: a vertically oriented drive rod mechanically coupled to a control rod drive mechanism operable to raise and lower the drive rod through a plurality of axial positions; a rod cluster control assembly comprising a plurality of control rods configured for removable insertion into a nuclear fuel core; a drive rod extension extending axially between the rod cluster control assembly and the drive rod, the drive rod extension having a bottom end releasably coupled to the rod cluster control assembly; and a drive rod extension grapple assembly connected to the drive rod, the grapple assembly releasably coupled to a top end of the drive rod extension. Raising and lowering the drive rod raises and lowers the rod cluster control assembly. In one embodiment, the grapple assembly includes an electromagnet which magnetically couples the drive rod extension to the grapple assembly when the electromagnet is energized and uncouples the drive rod extension from the grapple assembly when the electromagnet is de-energized. According to another exemplary embodiment, a control rod drive system for a nuclear reactor vessel includes: a control rod drive mechanism mounted externally to the reactor vessel; a drive rod mechanically coupled to the control rod drive mechanism and extending through the reactor vessel into an interior cavity of the reactor vessel holding a nuclear fuel core, the control rod drive mechanism operable to raise and lower the drive rod through a plurality of vertical axial positions; a grapple assembly connected to the drive rod in the interior cavity of the reactor vessel and movable with the drive rod; an electromagnet mounted in the grapple assembly; a rod cluster control assembly comprising a plurality of control rods configured for removable insertion into the nuclear fuel core; and a drive rod extension extending axially between the rod cluster control assembly and the grapple assembly. The drive rod extension includes: an axially extending actuator shaft having a top end including a magnetic block configured to releas ably engage the electromagnet of the grapple assembly and a bottom end configured to releasably engage the rod cluster control assembly; and a lifting head sleeve including a diametrically enlarged lifting head, the lifting head sleeve slidably receiving the actuating rod therethrough for axial upward and downward movement. The electromagnet is operable to magnetically couple the actuating shaft to the grapple assembly at the top of the drive rod extension when the electromagnet is energized and uncouple the actuating shaft from the rod cluster control assembly at the bottom of the drive rod extension when the electromagnet is de-energized. Raising the actuator shaft when the electromagnet is energized couples the actuator shaft to the rod cluster control assembly and de-energizing the electromagnet lowers and uncouples the actuating shaft from the rod cluster control assembly. According to another exemplary embodiment, a control rod drive system for a nuclear reactor vessel includes: a reactor vessel having a top head and an interior cavity; a nuclear fuel core supported in the interior cavity of the reactor vessel; a rod cluster control assembly comprising a plurality of control rods configured for removable insertion into the nuclear fuel core; a control rod drive mechanism mounted externally to the reactor vessel above the top head; a drive rod mechanically coupled to the control rod drive mechanism and extending through the top head of reactor vessel into the interior cavity, the control rod drive mechanism operable to raise and lower the drive rod through a plurality of vertical axial positions; a grapple assembly connected to the drive rod inside the interior cavity of the reactor vessel and movable with the drive rod, the grapple assembly including an electromagnet; a drive rod extension extending axially between the rod cluster control assembly and the grapple assembly, the drive rod extension including a bottom end releasably coupled to the rod cluster control assembly and a top end releasably coupled to the grapple assembly via the electromagnet; and a longitudinally-extending drive rod extension support structure mounted in the reactor vessel above the nuclear fuel core, the support structure including a plurality of vertically-oriented guide tubes at least one of which is configured to slidably receive the drive rod extension therein for axial upward and downward movement. The electromagnet is operable to magnetically couple the drive rod extension to the grapple assembly when the electromagnet is energized and uncouple the drive rod extension from the grapple assembly when the electromagnet is de-energized. De-energizing the electromagnet drops and uncouples the drive rod extension from the rod cluster control assembly remotely at the bottom of the drive rod extension. An exemplary method for coupling a control rod drive mechanism to a rod cluster control assembly in a nuclear reactor vessel is provided. The method includes the steps of: providing: a reactor vessel having a top head and an interior cavity; a nuclear fuel core supported in the interior cavity; a rod cluster control assembly positioned at a top of the fuel core and comprising a plurality of control rods configured for removable insertion the fuel core; a control rod drive mechanism mounted externally above the reactor vessel; a drive rod assembly including a drive rod mechanically coupled to the control rod drive mechanism and extending into the interior cavity of the reactor vessel, and a grapple assembly disposed on an end of the drive rod and including an electromagnet. The method further includes lowering the drive rod assembly; contacting the drive rod assembly with a top end of a drive rod extension extending vertically between the rod cluster control assembly and the top head of the reactor vessel, a bottom end of the drive rod extension contacting the rod cluster control assembly in a non-locking manner; engergizing the electromagnet to magnetically couple the drive rod assembly with the drive rod extension; raising the drive rod assembly by a first vertical distance; locking the bottom end of the drive rod extension with the rod cluster control assembly, wherein raising and lowering the drive rod assembly with the control rod drive mechanism raises and lowers the rod cluster control assembly for controlling the reactivity within the fuel core. All drawings are schematic and not necessarily to scale. Parts given a reference numerical designation in one figure may be considered to be the same parts where they appear in other figures without a numerical designation for brevity unless specifically labeled with a different part number and described herein. In addition, a reference to a single figure number prefix (e.g. FIG. 10) which comprises multiple figures of the same prefix number distinguished by different alphabetical suffixes (e.g. FIGS. 10A and 10B) shall be construed as a general reference to all figures sharing that same prefix number. The features and benefits of the invention are illustrated and described herein by reference to exemplary embodiments. This description of exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description of embodiments disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation. Terms such as “attached,” “affixed,” “connected,” “coupled,” “interconnected,” and similar refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. Accordingly, the disclosure expressly should not be limited to such exemplary embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features. System Component Definitions In one non-limiting example to provide an overview, a control rod drive system according to the present disclosure may generally include the following major assemblies defined below in summary fashion and further described herein in greater detail: Rod ejection protection device (REPD)—a hydraulically-actuated mechanically-returned collet which engages the drive rod of the CRDM and prevents the drive rod from moving in position in the event of a failure of the CRDS. Control rod drive mechanism (CRDM)—An electro mechanical device used to control the position of the Control Rods located in the reactor core Drive rod (DR)—A shaft that passes through the CRDM into the reactor vessel through the reactor vessel nozzle and is attached to the DREGA. Drive rod extension grapple assembly (DREGA)—An assembly that is used to connect the DR to the DRE. This assembly also contains an electromagnet which, when energized and de-energized, engages and disengages the DRE with the RCCA respectively. Drive rod extension support structure (DRESS)—a support structure designed to hold and guide the DREs. In one illustrative embodiment, for example without limitation, the DRESS may include thirty seven guide tubes. The guide tubes may be perforated to allow for water circulation (e.g. primary coolant) therethrough. Retaining collars (located at the top of the DRESS) may hold spring loaded retention devices. These devices attach to the DRE lifting head sleeve. Their purpose is to prevent the guide DRE from being removed from the DRESS inadvertently during reactor vessel head removal. The DRESS provides lateral and seismic restraint of the DREs. Drive rod extension (DRE)—A device that is connected to the DR by means of the DREGA which extends the reach of the DR to engage the RCCA located below. FIGS. 1 and 2 depict an exemplary embodiment of a control rod drive system 100. The control rod drive system 100 is shown installed on a reactor vessel 110 which includes a longitudinally-extending and elongated cylindrical shell 111 defining a vertical axis, bottom head 112, and top head 113. In one embodiment, the top head 113 may be removable form the shell 111 such as via a bolted flange joint or other form of detachable mounting. The reactor vessel defines an interior cavity 114 which holds a core support structure 115 configured to support a nuclear fuel core 116. In one embodiment, the core support structure 115 may be in the form of a tubular riser pipe 119 which conveys primary coolant flowing in an annular space 118 between the riser pipe 119 and shell 111 upwards through the fuel core 116 and outwards through a flow nozzle 117 fluidly coupled to a steam generator for generating steam. The primary coolant is heated by flow upwards through the fuel core 116. In one embodiment, the fuel core 116 may in the form of a self-supporting fuel cartridge such as the SMR-160 unitary fuel cartridge available from Holtec International which is insertable into the core support structure 115. As will be well known to those skilled in the art without undue elaboration, a typical nuclear reactor core in a light water reactor comprises tightly packed fuel assemblies 700 (also referred to as fuel bundles) as further shown in FIG. 8B. Each fuel assembly 700 is an assemblage of bundled fuel rods 702 which are sealed hollow cylindrical metal tubes (e.g. stainless steel or zirconium alloy) packed with enriched uranium fuel pellets and integral burnable poisons arranged in an engineered pattern to facilitate as uniform a burning profile of the fuel as possible (in both axial and cross sectional/transverse directions). Multiple longitudinally-extending cavities are formed within each fuel assembly 700 for insertion of the control rods 504 into the fuel core in the usual manner, such as through the top nozzles boxes 704 mounted atop each fuel assembly 700 which are disposed proximate to the bottom of the drive rod extension support structure (DRESS) 160 and accessible to the RCCAs 500. Numerous variations in the arrangement are possible. It will be appreciated that numerous variations are possible in the arrangement of components within the reactor vessel 110; the foregoing arrangement described representing only one possible exemplary embodiment. Accordingly, the invention is not limited in this regard to the embodiment described herein. As shown in FIG. 2, reactor vessel 110 may be considered a high head reactor vessel design in which the fuel core 116 is disposed near the bottom head 112 of the vessel within the core support structure 115 riser pipe. The distance between the top of the fuel core and top head 113 of the reactor vessel may exceed the usual 15-20 feet distance in typical pressurized light water reactors (PLWRs). The reactor vessel 110 may be made of any suitable metal, such as for example without limitation steels such as stainless steel for corrosion resistance. With continuing reference to FIGS. 1 and 2, control rod drive system 100 includes drive rod (DR) 130, drive rod extension (DRE) 400, drive rod extension support structure (DRESS) 160, drive rod extension grapple assembly (DREGA) 200, control rod drive mechanism (CRDM) 300, and rod ejection protection device (REPD) 140. Other than the DRESS 160 and fuel core 116 for which a single assembly of each may be provided for a reactor vessel 110, the control rod drive system (CRDS) 100 may actually include a plurality of the foregoing remaining components each associated with providing a lifting mechanism for raising/lowering one of the plurality of rod cluster control assemblies (RCCA) 500 (see, e.g. FIG. 11B) provided with the reactor vessel 110. Accordingly, there may in fact be a plurality of the component assemblies shown in FIGS. 1 and 2 although only a single CRDM 300 rod drive mechanism 300 and associated lifting components are shown for clarity of description. In one exemplary embodiment, for illustration, a reactor vessel 110 installation of a small modular reactor design may include approximately 37 CRDMs 300 and associated DREs 400. The invention is not limited to any particular number of CRDMs or other components. Control rod drive mechanisms 300 may each be housed in a structural enclosure 302 mounted to top head 113 of reactor vessel 100 for protection of the drive mechanism. The function of this enclosure structure includes to provide lateral and seismic support of the CRDMs 300, protect the CRDMs from projectile or missile generated within the primary containment structure (not shown) which encloses the reactor vessel 110, protect the CRDMs from potential drops of equipment from the overhead crane, provide a means of lifting the reactor vessel head, and provide a mounting location for the REPD 140 which may be mounted on top of enclosure 302 in one embodiment. The CRDM enclosures 302 may be attached to the reactor vessel top head 113 by any suitable means, such as without limitation welding. In one embodiment, the top head 113 of reactor vessel 110 may include a flanged nozzle 304 configured to receive a bottom mounting flange 306 on control rod drive mechanism 300 for coupling and supporting the drive mechanism from the reactor vessel head. The bottom mounting flange 306 may be detachably coupled to the flanged nozzle 304 with fasteners (e.g. bolts and nuts) to allow the control rod drive mechanism 300 to be removed for maintenance or replacement. The drive rod 130 extends vertically downwards through the rod ejection protection device 140, top of the enclosure 302, control rod drive mechanism 300, and further through the flanged nozzle 304 into the top portion of reactor vessel beneath top head 113 as shown in FIGS. 1 and 2. A set of seals may be provided with the drive rod 130 at the flanged nozzle 304 to prevent leakage of reactor coolant from the reactor vessel along the drive rod during operation. The bottom end of the drive rod 130 is coupled to the drive rod extension grapple assembly (DREGA) 200, as further described herein. Control rod drive mechanism (CRDM) 300 may be any type of commercially available electro-mechanical drive operable to lower/raise the drive rod 130 (and in turn DREGA 200 attached to the drive rod). As one non-limiting example diagrammatically illustrated in FIG. 18, a CRDM 300 of one type may have a drive assembly 600 generally utilizing a motor drive to rotate a lead screw 604 formed on the drive rod 130. Such drive mechanisms for drive rods are well known to those skilled in the art. In one arrangement, as shown, the electric drive motor 610 may be axially offset from the drive rod 130 and rotates a worm 608 (i.e. worm gear) arranged transversely to the drive rod. The worm 608 in turn rotates a ring gear 606 rigidly affixed to a ball collar or nut or collar 602 having ball bearings 612 engaged with the lead screw 604 on the drive rod 130. Rotating the ring gear 606 in opposing directions using the motor drive 610 which operates to rotate the worm 608 in opposing rotational directions alternatingly axially raises or lowers the drive rod 130 in a controlled manner. In other possible arrangements, the ball nut or collar may be directly coupled to the drive motor which may be arranged axially in line with the drive rod. In either of the foregoing arrangements, the CRDM rotates the ball nut or collar which axially advances or retracts the drive rod via the lead screw. Numerous variations of CRDMs using drive rod lead screws are possible. CRDMs are commercially available from a number of manufacturers, including for example General Atomics of San Diego, Calif. CRDMs are further described in U.S. Pat. No. 5,999,583 and U.S. Patent Application Publication 2010/0316177, which are incorporated herein by reference in their entireties. FIGS. 3 and 4 show drive rod extension grapple assembly (DREGA) 200 in greater detail. DREGA 200 includes a cylindrical grapple body 202 having sidewalls 232 defining an interior chamber 212, an open top 224, and a downwardly open bottom 226. Top 224 may be closed by a removable top plate 204 in one embodiment which is attached to the top annular face of grapple body 202 via a plurality of circumferentially spaced fasteners 206. The open bottom 226 allows an upper portion of drive rod extension 400 to be inserted therein, as further described herein. An electromagnet 228 is disposed in chamber 212 which is engageable with a magnetic block 402 of drive rod extension 400 (see, e.g. FIG. 9). In one embodiment, electromagnet 228 may be mounted at the top end of chamber 212 and affixed to the underside of top plate 204 by one or more fasteners 208. Other variations for mounting electromagnet 228 are possible. With continuing reference to FIGS. 3 and 4, drive rod extension grapple assembly (DREGA) 200 further includes plurality of circumferentially spaced and radially movable lifting pins 216. Lifting pins 216 may be oriented horizontally in one embodiment and are operable to project radially inwards into chamber 212 towards the vertical centerline of grapple body 202 through corresponding circumferentially spaced openings 214 formed through the body. The lifting pins 216 are radially movable between a projected position (shown in FIG. 4) extending partially into the chamber 212 and a retracted position withdrawn from the chamber. Lifting pins 216 may each be biased inwards towards the projected position via a suitably configured lift spring 218 having an end which engages an outward facing open socket formed in each pin as shown. In one embodiment, lifting pins 216 may be movably disposed in an annular shaped housing 222 which extends radially outwards from grapple body 202. Housing 222 includes a plurality of circumferentially spaced bores 230 having a circular cross section configured to slidably receive lifting pins 216 therein. Bores 230 may extend radially completely through the housing 222 and sidewalls 232 of grapple body 202 communicating with openings 214. Each bore 230 includes a lifting pin 216 and associated spring 218. The lifting pins 216 may include a stepped shoulder 234 which engages a complementary configured stepped portion of the bore 230 to prevent the lifting pins from being ejected by the spring 218 completely through holes 214 into the chamber 212 of the grapple body 202. In one embodiment, the exterior opening in each bore 230 may be closed off by a removable cap 220 which threadably engages the annular housing 222. The caps 220 each have an interior surface which may engage one end of spring 218. In one embodiment, the annular housing 222 may be threaded along an exterior portion surrounding each bore 230 and the caps 220 may threadably engage these threaded bore surfaces. Other suitable arrangements of mounting caps 220 to close bores 230 may be used. The drive rod extension grapple assembly (DREGA) 200 may be mounted to the bottom end of the drive rod 130 by any suitable means. For example, without limitation, drive rod 130 may be threadably coupled directly to DREGA 200 via a threaded socket formed in the top plate 204 and threading the bottom end of the drive rod, via mounting brackets and fasteners, welding, or other suitable mechanical mounting techniques used in the art. Preferably, in certain embodiments, DREGA 200 is rigidly mounted to the drive rod 130. In one embodiment, cylindrical grapple body 202 may have a maximum outside diameter larger than the interior diameter of the flanged nozzle 304 so that the DREGA A cannot be inserted or retracted through the nozzle. In such an arrangement, the DREGA 200 is connected to the end of the drive rod 130 beneath the top head 113 of the reactor vessel 110. Other suitable arrangements are possible. FIGS. 5-8 (including all alphabetical subparts) depict the drive rod extension support structure (DRESS) 160. DRESS 160 is a vertically elongated structure which includes a plurality of upper guide tubes 161 and lower guide tubes 162 circumscribed by an open lattice outer support frame 163 having a cylindrical shape to complement the shape of the riser pipe 119 in which the DRESS may be inserted from the top. The open structure reduces the weight of the support frame 163 while providing structural strength. In one exemplary embodiment, without limitation, the outer support frame 163 may have an X-shaped lattice formed by diagonal supports 164 arranged in an X-pattern and enlarged junction plates 165 formed at the intersection of the diagonal supports. Other suitable open or closed structures are possible for support frame 163. The upper and lower guide tubes 161, 162 may be intermittently supported along their lengths by axially spaced apart horizontal supports 166. A horizontal support 166 is provided at the top 166a and bottom 166b of DRESS 160. In one exemplary embodiment, the supports 166 may be spaced axially apart at approximately 5-6 feet intervals along the longitudinal length of the guide tubes 161, 162. Other appropriate axial spacing may be used. In one embodiment, the horizontal supports 166 may be comprised of interconnected lateral grid plates 171 extending between adjacent guide tubes 161, 162. The outermost supports 166 may be attached at their ends to an annular shaped peripheral rim 169 which may be attached to the interior surface of the cylindrical outer support frame 163, such as at the junction plates 165 and/or along horizontal arcuately shaped strap members 167 connected between junction plates. In one embodiment, the horizontal supports 166 may be welded to the outer support frame; however, other suitable attachment methods may be used instead of or in addition to welding such as fasteners. In one embodiment, the uppermost horizontal support 166 may include an array of laterally spaced circular retaining collars 170 mounted onto the top ends of each upper guide tube 161. This forms a grid array of retaining collars 170 having a pattern or layout in top plan view which matches the horizontal pattern or layout of the upper guide tubes 161. The retaining collars 170 each have a central opening configured to receive a respective upper guide tube therein. The retaining collars 170, located at the top of the drive rod extension support structure (DRESS) 160, may include spring loaded retention devices in the form of radially movable retaining pins 172 spaced circumferentially around the retaining collars (see, e.g. FIGS. 5A and 11A). The retaining pins 172 may be horizontally oriented and movable to be retracted from or projected into the central hole of the retaining collar 170. As noted above the retaining pins 172 engage the DRE lifting head sleeve 408 (see also FIGS. 10 and 11). One of their purposes is to prevent the guide DRE 400 from being removed from the DRESS 160 inadvertently during reactor vessel head removal. The upper guide tubes 161 have a diameter selected to allow the drive rod extension (DRE) 400 to be axially inserted completely through the guide tube in one embodiment. This allows raising and lowering of the DREs 400 by the control rod drive mechanism (CRDM) 300. Each of the lower guide tubes 162 may have a larger diameter than the upper guide tubes 161. The lower guide tubes 162 have a diameter selected to allow the entire control rod support plate 502 of the rod cluster control assembly (RCCA) 500 (shown in FIG. 11B) to be raised and lowered within the lower guide tubes for inserting and retracting the control rods 504 into and from the fuel core 116. The control rod support plate 502 has a larger diameter than the widest component of the DRE 400 in the present exemplary embodiment, thereby necessitating a larger diameter for the lower guide tubes 162 than the upper guide tubes 161. In one embodiment, guide tube transition fittings 168 may be used to couple the lower ends of each upper smaller diameter upper guide tube 161 to a corresponding concentrically aligned lower guide tube 162. In one embodiment, the transition fittings 168 may be frusto-conical shaped as best shown in FIGS. 5B and 6A and have an open structure comprised of axially spaced apart upper and lower rings 168a, 168b each attached respectively to an upper and lower guide tube 161, 162. Accordingly, the lower rings 168b have a larger diameter than the upper rings 168a in this embodiment. The rings 168a, 168b may be joined to form a structural unit by angled and vertically extending struts 168c extending between the rings. In other embodiments, the guide tube transition fittings 168 may be closed. Other suitable configurations of guide tube transition fittings 168 are possible including non-frusto-conical shapes. The guide tube transition fittings 168 help maintain axial alignment between the upper and lower guide tubes 161, 162. The guide tubes 161, 162 in turn help maintain axial alignment of the control rods with respective corresponding cavities in the fuel core 118 for insertion or retraction of the rods to control the nuclear reaction rate in various portions of the core. Other suitable configurations of transition fitting, however, may be used and numerous variations are possible. In some embodiments, the upper and lower guide tubes 161, 162 may each include a plurality of holes or perforations along their respective lengths as shown in FIGS. 5-8 which allow the primary coolant to flow inside the guide tubes within the riser pipe 119. The holes or perforations may be distributed both circumferentially and longitudinally around each guide tube 161, 162 in a suitable pattern. Referring to FIGS. 2 and 8, the drive rod extension support structure (DRESS) 160 may be mounted inside the upper portion of riser pipe 119 proximate to the top of the fuel core 116. This allows the lower operating ends of each drive rod extensions (DREs) 400 which may be coupled and uncoupled from the rod cluster control assembly (RCCA) 500 to be in proper position for inserting or retracting the control rods 504 into/from the fuel core 116 for controlling the nuclear reaction rates in parts or all of the fuel core, as further described herein. FIGS. 9 and 10 show the drive rod extension (DRE) 400 in greater detail. Each DRE 400 is intermediate link which operably couples a drive rod 130 at top end 401 of the DRE to a corresponding rod cluster control assembly (RCCA) 500 at bottom end 403 of the DRE. DRE 400 includes an inner actuator shaft 404 which is disposed inside an outer actuator tube 406 and a lifting head sleeve 408. Actuator shaft 404 extends longitudinally for substantially the entire length of the DRE 400 and may be a single unitary structure in some embodiments. In one embodiment, lifting head sleeve 408 is positioned at an upper portion of the DRE above the top of the drive rod extension support structure (DRESS) 160. Lifting head sleeve 408 has a bottom end 421 and a top end 412 that abuts a lower surface 414 of a diametrically enlarged lifting head 410. Axially spaced between ends 412 and 421 is an annular stop flange 416 extending radially outwards from lifting head sleeve 408. The stop flange 416 is configured to engage an axially movable bobbin 430 which is slidable on lifting head sleeve 408 and defines a lower travel stop for the bobbin. Stop flange 416 may be further arranged to engage the top of retaining collar 170 to limit the insertion depth of the lifting head sleeve into the upper guide tube 161 (see also FIG. 11A). Lifting head sleeve 408 may further include a stepped portion 420 which defines a downward facing surface which abuts a top end 422 of actuator tube 406. In one embodiment, the bottom end 421 of lifting head sleeve 408 may be sized to be inserted into the open top end 422 of actuator tube 406. An axial portion of lifting head sleeve 408 disposed between stop flange 416 and stepped portion 420 defines a recessed annular seating surface 423 configured to removably receive and engage spring biased retaining pins 172 of retaining collar 170 which is initially positioned around the lifting head sleeve at this location (see also FIGS. 5A and 11A). With continuing reference to FIGS. 9 and 10, bobbin 430 includes an outward-upward facing angled upper bearing surface 432 and an opposing outward-downward facing angled lower bearing surface 434 which meet at a circumferentially extending apex A. Lower bearing surface 434 is selectively engageable with 216 of drive rod extension grapple assembly (DREGA) 200. Upper bearing surface 432 is selectively engageable with lifting head 410. The functionality of these bearing surfaces will be further described herein. Lifting head 410 may be an annular generally inverted cup-shaped member in some embodiments. Lifting head includes an annular outward-upward facing angled upper bearing surface 424 and opposing annular inward-downward facing angled lower bearing surface 414. Bearing surface 414 defines a downwardly open cavity 426 which is configured to receive and complement the configuration of bobbin upper bearing surface 432. A portion of lower bearing surface 414 is engaged by top end 412 of lifting head sleeve 408 to maintain the axial position of the lifting head 410. Lifting head 410 has a larger diameter than the top end 412 of lifting head sleeve 408. DRE 400 may further include a drive extension spring 462 having a bottom end engaging a top surface 427 of lifting head 410. Spring 462 is arranged concentrically around actuator shaft 404 and may be a helical coil spring in some embodiments. In one embodiment, a hollow and cylindrically-shaped spring retainer 460 may be provided which holds spring 462 therein. Spring retainer 460 may have an open bottom and a partially open top defining a central opening 466. A top end of spring 462 may engage the underside of a spring spacer 464 disposed inside the spring retainer beneath central top opening 466 configured to receive magnetic block 402 at least partially therethrough (see, e.g. FIGS. 15 and 16). The spring spacer 464 may be generally shaped as a washer having a diameter larger than the diameter of central opening 466 to prevent the drive extension spring 462 from being ejected out the top of the spring retainer 460. The bottom of magnetic block 402 may bear against the top side of spring spacer 464 in some positions. Lifting head 410 may further include a stepped portion 425 formed in the top surface 427 and/or upper bearing surface 424 which engages a bottom annular edge 429 of spring retainer 460 for locating the spring retainer on the lifting head. In one embodiment, as shown in FIGS. 9 and 10, lifting head 410 and spring retainer 460 may be disposed in the general proximity of top end 401 of actuator shaft 404 spaced axially downwards from the top end. With continuing reference to FIGS. 9 and 10, the lower portion of the drive rod extension (DRE) 400 includes an adapter sleeve 440 having a bottom end 444 and a top end 442 attached to the bottom end 428 of the actuator tube 406. Adapter sleeve 440 has a hollow cylindrical body which slidably receives actuator shaft 404 therein. In one embodiment, the bottom end 428 of the adapter sleeve 440 may be open. Actuator cap 454 may be inserted through the open bottom end 428 of adapter sleeve 440 to threadably engage bottom end 403 of actuator shaft 404 via a fastener. Adapter sleeve 440 includes an RCCA locking mechanism configured for releasably coupling the sleeve to the rod cluster control assembly (RCCA) 500. In one embodiment, the locking mechanism may be a locking element assembly 450 comprised of a plurality of circumferentially spaced apart and radially moveable locking elements. The locking elements in one exemplary configuration may be locking balls 452 which may be retained on an outer surface of the adapter sleeve 440 by ball retaining plates 451 spaced circumferentially about the sleeve. The locking balls 452 are engageable with an annular machined groove 510 formed on an inside surface of a tubular mounting extension 506 rising upwards from a hub 508 of the RCCA 500 (see, e.g. FIG. 11B). The locking balls 452 are actuated by the actuator cap 454, as further described herein. When the drive rod extension (DRE) 400 is mounted in the reactor vessel 110, the adapter sleeves 440 of each DRE are located proximate to the bottom ends of lower guide tubes 162 in the drive rod extension support structure (DRESS) 160. This positions the adapter sleeve 440 to releasably engage the rod cluster control assembly (RCCA) 500 via the locking ball assembly 450. The locking ball assembly 450 is operable to couple and uncouple the RCCA 500 from the DRE 400, as further described herein. The fuel core 116 is located at the bottom of the reactor vessel 110 supported inside the core support structure 115, such as riser pipe 119. On top of the fuel core 116 is the drive rod extension support structure (DRESS) 160. The DRESS 160 is oriented such that each guide tube is axially and vertically centered above a RCCA 500 installed in the fuel core 116. The drive rod extensions (DRE) 130 are each positioned in the DRESS 160 and the lower portion of each DRE is seated in and loosely engaged with an RCCA 500, although not yet locked in place during initial assembly as evidenced in FIG. 11B showing the actuator cap 454 positioned below the locking ball assembly 450 near the bottom of the adapter sleeve 440. Control Rod Drive System Operation An exemplary method for coupling a control rod drive mechanism (CRDM) 300 to a rod cluster control assembly (RCCA) 500 will now be described with various reference to FIGS. 11-17 showing sequential steps in the method or process. The drive rod extension support structure (DRESS) 160 is not shown in these figures for clarity. In one embodiment, as described in greater detail below, the method may be generally accomplished by first coupling the drive rod 130 to the top of the drive rod extension (DRE) 400 which will enable the DRE to then be finally coupled to the RCCA 500. It should be noted that the following process addresses the coupling of a single CRDM 300 to a RCCA 500. This same process, however, may be repeated for making the other CRDM-RCCA couplings for embodiments of control rod drive system (CRDS) 100 in which multiple RCCAs are each individually controlled by a separate dedicated CRDM. The reactor vessel 110 is initially provided with the drive rod extension support structure (DRESS) 160 installed above the fuel core 116 in the core support structure 115, in this embodiment tubular riser pipe 119. DRE 400 is preliminarily installed and inserted in the drive rod extension support structure (DRESS) 160. The DRE 400 is positioned within the upper and lower guide tubes 161, 162. At this juncture, however, the DRE 400 is initially not operably coupled to either the RCCA 500 or the drive rod assembly (i.e. drive rod extension grapple assembly (DREGA) 200 attached to drive rod 130). As shown in FIG. 11A, the drive rod extension (DRE) 400 is in an initial or starting vertical axial position with the top end of the actuator shaft 404, lifting head 410, and bobbin 430 exposed and extending above retaining collar 170 of the drive rod extension support structure (DRESS) 160. The makes the upper portion of DRE 400 accessible to the drive rod extension grapple assembly 200 below the top head 113 of the reactor vessel 110. In this initial position of DRE 400, the flange 416 of lifting head sleeve 408 may be engaged with the retaining collar 170 and the lifting head sleeve is engaged with the radially biased retaining pins 172 of the collar. At the bottom end of the DRE 400, the adapter sleeve 440 is positioned and inserted into, but not lockingly engaged with the tubular mounting extension of the rod cluster control assembly (RCCA) 500. Accordingly, at this initial starting position, the RCCA 500 cannot be operably raised or lowered by CRDM 300 because the RCCA has not yet been operably coupled and locked to the DRE 400. To engage the DRE 400 with the RCCA 500 at the fuel core 116, the DREGA 200 is first connected to the DRE in the overall coupling process. The DREGA 200 and drive rod 130 are axially (vertically) aligned with but spaced apart from top end 401 of DRE 400 (see FIG. 11A). The CRDM 300 is operated to lower the drive rod 130 with DREGA 200 attached thereto towards the top end 401 of DRE 400. As the DREGA 200 is lowered onto the DRE 400, the lifting pins 216 initially in a fully extended position engage angled upper bearing surface 424 of lifting head 410 (see FIGS. 4, 10, and 12A). The lifting pins 216 and lift springs 218 gradually retract farther and farther into the DREGA housing 222 on the grapple body 202 as DREGA 200 continues to be lowered and pushed over the lifting head 410 of DRE 400. The lifting pins 216 slidingly engage the upper bearing surface 424 moving from top to bottom of the lifting head 410 (see FIG. 12B). The lift springs 218 become compressed by the retracting motion of the lifting pins 216. When the lifting pins 216 clear and reach a position just beneath the lifting head 410, the pins return to their original fully extended positions inside DREGA interior chamber 212 under the inwards biasing force of the lift springs 218 (i.e. lifting pins are in a position slightly above that shown in FIG. 13). The DREGA 200 is now attached to the DRE 400 and lifting pins 216 are positioned above the bobbin 430 as shown. It should be noted that DREGA 200 cannot be disengaged from DRE 400 at this point with the lifting pins 216 in this axial position by merely raising the drive rod and DREGA with the CRDM 300. Accordingly, the method carries on by continuing to lower the DREGA 200 until the electromagnet 228 in the DREGA comes into complete physical contact with the magnetic block 402 fastened to the top end 401 of the DRE actuator shaft 404, as shown in FIG. 13. The electromagnet 228 is then activated (energized) from a power source. Activation of the electromagnet 228 causes the magnetic block 402 to be releasably coupled to the electromagnet. After this magnetic coupling is completed, the DREGA 200 and drive rod 130 assembly is now fully connected to the DRE 400 such that raising and lowering the drive rod using CRDM 300 concomitantly raises and lowers the actuator shaft 404 of the DRE as long as the electromagnet 228 remains energized. In the foregoing position shown in FIG. 13, it should be noted that drive extension spring 462 is uncompressed. The bottom of the magnetic block 402 is positioned proximate to and may be in contact with the top of the spring retainer 460. In order to attach the RCCA 500 remotely situated at the top of the fuel core 116 from the CRDM 500 to the DRE 400, the actuator shaft 404 in one embodiment needs to be pulled up to force the locking balls 452 radially outwards through the adapter sleeve 440 and into the machined groove 510 located in the RCCA which engages the actuator shaft with the RCCA to complete the coupling at the bottom of the DRE. At this point in the installation process, the lifting head sleeve 408 of DRE 400 is still in its initial axial starting position shown similarly in FIGS. 11A and 13, but with the DREGA 200 magnetically coupled to the DRE as shown in FIG. 13. The uncoupled DRE 400 and RCCA 500 are in their respective lowermost initial positions and at the bottom of their vertical range of travel in the reactor vessel 110 and DRESS 160. The control rods 504 are fully inserted in the fuel core 116. The lifting head sleeve 408 remains as yet engaged with the retaining pins 172 in retaining collar 170. With additional reference to FIG. 10A, the recessed annular seating surface 423 of lifting head sleeve 408 is engaged with the spring biased retaining pins 172 of retaining collar 170 which serve to releasably hold the sleeve 408 in position during coupling of the DREGA 200 to the DRE 400. As a point of reference, it may be noted that the lifting head sleeve stop flange 416 may still rest on the top of retaining collar 170 at present (see, e.g. FIG. 13) which prevents the lifting head sleeve 408 from dropping any lower into the upper guide tube 161 of the DRESS 160. With the DRE 400 in the position of FIG. 13 and the foregoing magnetic coupling completed of the DREGA 200 with the DRE, the DREGA is then next raised upwards by a first vertical distance (via the drive rod 130 using CRDM 300) which pulls and slides the actuator shaft 404 upwards inside the adapter sleeve 440 which remains stationary. The actuator cap 454 mounted to the bottom of the actuator shaft 404 moves axially upwards with the shaft from an unlocked position (shown, e.g. in FIG. 11B) to a locked position (shown, e.g. in FIG. 14B) forcing the locking balls 452 radially outwards from the adapter sleeve 440 to engage the machined groove 510 inside RCCA 500. As shown in FIG. 14B, the DRE 400 is now fully but releasably coupled at the bottom to RCCA 500 which can be raised or lowered by the CRDM 300 via the DRE 400. Accordingly, the CRDM 300 has now been linked to the RCCA 500 for controlling the insertion depth of the control rods 504 into the fuel core 116 for controlling the reactivity. It should be noted that in the unlocked position of actuator cap 454 (see, e.g. FIG. 11B, 15B, or 16B), the larger diameter lower actuating portion 470 of the cap with annular bearing surface 472 does not contact the locking balls 452 which remain seated but relatively loose in the ball retaining plate 451. This does not create positive locking engagement of the locking balls 452 with the machined groove 510 on the inside of the tubular mounting extension 506 of RCCA 500 sufficient to couple the DRE 400 to the RCCA. The reduced diameter upper portion 471 of actuator cap 454 even when positioned adjacent to the locking balls 452 (see, e.g. FIG. 10B) leaves an annular gap G between the cap and adapter sleeve 440 so the locking balls 452 remain loose and not positively engaged with the machined groove 510 of the RCCA 500. In the locked position of the actuator cap 454 (see, e.g. FIG. 14B), the annular bearing surface 472 of the larger diameter lower actuating portion 470 of the cap is adjacent to and contacts locking balls 452. Since there is no appreciable annular gap or space between the lower portion 470 of actuator cap 454 and adapter sleeve 440, the annular bearing surface 472 drives the locking balls 452 outwards to engage machined groove 510 of the RCCA tubular mounting extension 506 which positively couples the DRE 400 to the RCCA 500. In one embodiment, a sloping transition 475 (see, e.g. FIG. 16B) may be formed between the larger diameter lower portion 470 and reduced diameter upper portion 471 of the actuator cap 454 to provide smooth sliding operation and engagement of the lower portion 470 with the locking balls 452. After the RCCA 500 has been coupled to the CRDM 300 in the foregoing manner, the RCCA remains in its bottom and lowermost position within the lower guide tubes 162 proximate to the top of the fuel core 116. To provide the ability to operationally retract the control rods 504 from the fuel core 116, the DREGA 200 is slightly raised further upwards if necessary via the CRDM 300 until the lifting pins 216 engage the bottom of lifting head 410 (as shown in FIG. 14A) if not already engaged by the DREGA-RCCA coupling process). Until the lifting pins 216 engage the underside of lifting head 410, this initial limited upward range of travel raises the actuator shaft 404 and DREGA 200, but not the lifting head sleeve 408 which remains engaged with retaining collar 170 and retaining pins 172. DREGA 200 is then further raised through a second upward vertical distance and range of travel which pulls both the actuator shaft 404 (via the magnetic coupling with the DREGA) and lifting head 410 with lifting head sleeve 408 fixed thereto upwards together simultaneously. This action disengages the lifting head sleeve 408 from the retaining pins 172 in retaining collar 170 as also shown in FIG. 14A. The DRE 400 (including actuator shaft 404, lifting head sleeve, actuator tube 406, and adapter sleeve 440 shown in FIGS. 10A and 10B) and the RCCA 500 coupled thereto may now be freely raised as a unit to a maximum height within the reactor vessel 110 representing the fullest retracted position of the control rods 504 from the fuel core 116 during normal operation of the reactor vessel 110. The actuator shaft 404 and lifting head sleeve 408 may further be alternatingly lowered and then raised again through a plurality of possible axial positions via operation of the CRDM 300 and drive rod 130. It may be noted that the RCCA 500 fits inside and slides axially upward and downward within the confines of the lower guide tubes 162 of the DRESS 160 which have a diameter selected to fully receive the RCCA therein in one embodiment. The length of the lower guide tubes 162 establishes the maximum vertical range of travel of the RCCA 500 and correspondingly the control rods 504 mounted thereto. A method to detach the rod cluster control assembly (RCCA) 500 from the drive rod extension (DRE) 400 and CRDM 300 for SCRAM events or other purposes such as opening the reactor vessel head will now be described. In one embodiment, the electromagnet 228 is first de-activated. This allows the actuator shaft 404 to fall or drop by a preset distance determined by the drive extension spring 462 and the spring spacer 464. Doing so permits the locking balls 452 to fall into the gap G created by the reduced diameter upper portion 471 of the actuator cap 454. The RCCA 500 is now disengaged from the actuator shaft 404 of drive rod extension (DRE) 400 and the CRDM 300. The foregoing falling action of the actuator shaft 404 also re-engages the lifting head sleeve 408 with the retaining pins 172 in retaining collar 170 of the DRESS 160 (see FIG. 15A). It should be noted that this uncoupling action ensures that the control rods attached to the RCCA 500 remain fully inserted into the fuel core 116 which shuts down the nuclear reaction. FIGS. 14 and 15 illustrate this foregoing uncoupling sequence. When in the foregoing position, it should be noted that the DRE 400 can also be completely removed from the drive rod extension support structure (DRESS) 160 if desired by simply lifting the drive rod extension grapple assembly (DREGA) 200 via the control rod drive mechanism (CRDM) 300. Because the electromagnet 228 has been de-energized, this lifting action will disengage the lifting head sleeve 408 from the retaining pins 172 in retaining collar 170 of the DRESS 160 (see also FIGS. 5A and 11A). A method for uncoupling and removing the DREGA 200 from the DRE 400 (remaining in place in DRESS 160) will now be described. First, the electromagnet 228 is deactivated (and the RCCA 500 is unlocked) in the manner already described above and shown in FIGS. 15A and 15B. Next, the DREGA 200 is pushed downwards via the CRDM 300 (and drive rod 130) to engage the bobbin 430. The lifting pins 216 initially engage angled upper bearing surface 432 which increasingly drives the pins radially outwards (i.e. retracted from chamber 212) back into the DREGA 200 as the pins advance downwards along the upper bearing surface. The lifting pins 216 reach a maximum retracted position at the apex A of the bobbin 430, and then increasingly begin projecting back inwards into chamber 212 of DREGA 200 again as the pins travel downwards along the angled lower bearing surface 434 (see FIG. 16A). Eventually, the lifting pins 216 become fully extended beneath the bobbin 430 immediately above stop flange 416 on lifting head sleeve 408. The downward movement of DREGA 200 simultaneously compresses drive extension spring 462 as shown in FIG. 16A which allows the positioning of lifting pins 216 below bobbin 430 to occur. Note that a portion of magnetic block 402 has passed through the central opening 466 and entered spring retainer 460 to compress the spring 462. To complete the uncoupling of DREGA 200 from the DRE 400, the DREGA is then raised concomitantly lifting the bobbin 430 with it via the lifting pins 216 into the lifting head 410 until the bobbin cannot move any higher, as shown in FIG. 17A. This occurs when the angled upper bearing surface 432 of bobbin 430 enters cavity 426 and engages complementary configured lower bearing surface 414 of lifting head 410. The bobbin 430 is now nested in lifting head 410. As the DREGA 200 then continues to be raised, the lifting pins 216 will again retract outward back into DREGA housing 222 and ride along the outside of the bobbin (angled lower bearing surface 434) as shown in FIG. 17B. The lifting pins 216 then engage and slide along angled upper bearing surface 424 of lifting head 410 whereon the pins again increasingly begin projecting back inwards into chamber 212 of DREGA 200. Eventually, the lifting pins 216 become fully extended and are free of the lifting head 410 as shown in FIG. 17C. The DREGA 200 is now fully disengaged from the drive rod extension (DRE) 400 which in turn has disengaged the CRDM 300 from the DRE. A control rod drive system according to the present disclosure provides numerous advantages, including the following. The length of the CRDM drive rod 130 may be limited to a relatively short length that is easily manufacturable. The shorter length drive rod has the added benefits of ease of maintenance. There is no risk of the drive rod being damaged during a SCRAM because the drive rod does not fall in a SCRAM event for full insertion of control rods into the fuel core to suppress the nuclear reaction as in prior known designs. In embodiments of the present invention, the control rod assembly (RCCA) 500 holding the control rods is released by uncoupling the RCCA from the drive rod extension (DRE) 400 during a SCRAM. Furthermore, because the drive rod does not fall during a SCRAM, the top nozzle of the fuel assembly is not at risk for being damaged during a SCRAM. The complex electromechanical components in the CRDM system 100 are not subject to the harsh environment inside of the reactor vessel because the CRDM 300 is mounted external to the reactor vessel. The redundant rod ejection protection device (REPD) 140 eliminates the potential for the drive rod 130 to be ejected from the reactor vessel due to a CRDM housing failure. A final advantage is that the CRDS 100 may be designed so that so that the CRDS will always SCRAM under gravity if the power to the CRDM 300 is cut via magnetically uncoupling the DREGA 200 from the DRE 400, as described above. Unless otherwise specified, the components described herein may generally be formed of a suitable material appropriate for the intended application and service conditions. A suitable metal is generally preferred for the components described herein with exception of the magnetic components. Components exposed to a corrosive or wetted environment may be made of a corrosion resistant metal (e.g. stainless steel, galvanized steel, aluminum, etc.) or coated for corrosion protection. While the foregoing description and drawings represent exemplary embodiments of the present disclosure, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope and range of equivalents of the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, sizes, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. In addition, numerous variations in the methods/processes described herein may be made within the scope of the present disclosure. One skilled in the art will further appreciate that the embodiments may be used with many modifications of structure, arrangement, proportions, sizes, materials, and components and otherwise, used in the practice of the disclosure, which are particularly adapted to specific environments and operative requirements without departing from the principles described herein. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive. The appended claims should be construed broadly, to include other variants and embodiments of the disclosure, which may be made by those skilled in the art without departing from the scope and range of equivalents.
summary
claims
1. A control rod for a boiling water reactor comprising:a structure element;a handle mounted to an upper end potion of the structural element; anda lower support member mounted to a lower end portion of the structure element;wherein the structure element includes four blades having a neutron absorber-filling region in which neutron absorber is held, respectively, and the four blades are disposed perpendicularly to one another;wherein the structure element has a plurality of regions formed in an axial direction of the control rod, the plurality of regions including a first region having a first cross-section that forms a first united cruciform cross-section of the four blades connected to one another, a second region having a second cross-section that has each separated cross-section of the four blades, and a third region having a third cross-section that has a second united cross-section of continuous two blades, which are disposed in a diametrically opposite direction of the four blades, and each separated cross-section of remaining two blades, which are disposed in a diametrically opposite direction and disposed perpendicularly to the continuous two blades, of the four blades;wherein the first region is formed in a first end portion of a handle side of the structure element and a second end portion of a lower support member side of the structure element, respectively;wherein the third region is formed between the first region formed in the first end portion and another first region formed in the second end portion; andwherein the second region is formed between the first region formed in the first end portion and another first region formed in the second end portion exclusive of the third region. 2. The control rod for a boiling water reactor according to claim 1, wherein the structure element has plate members disposed perpendicularly to each other and connected to each other; the first, second and third regions are formed in the plate members; and the plate members includes the neutron absorber-filling regions of the four blades. 3. The control rod for a boiling water reactor according to claim 1, wherein in a second region, a first opening portion is formed between two first blades, which are disposed in the diametrically opposite direction, of the four blades, and a second opening portion is formed between two second blades, which are disposed in the diametrically opposite direction and disposed perpendicularly to the first blade, of the four blades, and in the third region, the second united cross-section is disposed in either the first or second opening portion. 4. The control rod for a boiling water reactor according to claim 3, wherein the first regions include a cruciform connection member that connects the four blades to one another; the third region include a cross-link member that is connects to the two blades included in the continuous two blades; and in the third region, the cross-link member is disposed in the second opening portion. 5. The control rod for a boiling water reactor according to claim 4, wherein in the third region, a ratio of a distance between the cross-link member and the blade disposed perpendicularly to the cross-link member to a width of the third blade is 2/25 or less. 6. The control rod for a boiling water reactor according to claim 1, wherein the four blades include a first blade and a second blade, and a third blade and a fourth blade disposed perpendicularly to the first and second blade; the first and second blades are disposed in a diametrically opposite direction and facing each other; the third and fourth blades are disposed in a diametrically opposite direction and facing each other; and the first cross-section of the first region, the second cross-section of the second region and the third cross-section of the third region include each cross-section of the first, second, third and fourth blades, respectively. 7. The control rod for a boiling water reactor according to claim 6, wherein in the second region, a first opening portion is formed between the first blade and the second blade and a second opening portion is formed between the third blade and the fourth blade; and in the third region, either the first or second opening portion is formed between the remaining two blades. 8. The control rod for a boiling water reactor according to claim 7, wherein the first regions include a cruciform connection member that connects the first, second, third and fourth blades to one another; the cross-link members include a first cross-link member and a second cross-link member; the third regions include a fourth region having the first cross-link member that connects the first and second blades to each other and a fifth region having the second cross-link member that connects the third and fourth blades to each other; the first cross-link member is disposed above the second cross-link member; the fourth region includes a fourth united cross-section, which has a cross-section of the first cross-link member and cross-sections of the first and second blades being the continuous two blades and each separated cross-section of the third and fourth blades, being the second united cross-section; and the fifth region includes a fifth united cross-section, which has a cross-section of the second cross-link member and cross-sections of the third and fourth blades being another continuous two blades and each separated cross-section of the first and second blades, being the second united cross-section. 9. The control rod for a boiling water reactor according to claim 8, wherein in the fourth region, the first opening portion is formed between the first blade and the second cross-link member and between the second blade and the second cross-link member, respectively; and in the fifth region, the second opening portion is formed between the third blade and the first cross-link member and between the fourth blade and the first cross-link member, respectively. 10. The control rod for a boiling water reactor according to claim 8, wherein in the fourth region, a ratio of a distance between the first cross-link member and the third blade to a width of the blade is 2/25 or less and a ratio of a distance between the first cross-link member and the fourth blade to the width of the blade is 2/25 or less; and fifth region, a ratio of a distance between the second cross-link member and the first blade to the width of the blade is 2/25 or less and a ratio of a distance between the second cross-link member and the second blade to the width of the blade is 2/25 or less. 11. The control rod for a boiling water reactor according to claim 1, wherein the third region includes a cross-link member connecting each of the two blades in the second united cross-section of the continuous two blades and an opening is formed between the cross-link member and each of the two blades in the each separated cross-section of the third region.
abstract
A reactor cooling and power generation system according to the present disclosure includes a reactor vessel, a heat exchange section formed to receive heat generated from a core inside the reactor vessel, from a feedwater system through a fluid, and an electric power production section. A Stirling engine is provided to produce electric energy using the energy of the fluid whose temperature has increased while receiving the heat of the reactor. The system is formed to circulate the fluid that has received heat from the core in the heat exchange section through the electric power production section. The system operates even during a normal operation and during an accident of the nuclear power plant.
summary
047132086
claims
1. Apparatus for forming and sustaining a spheromak plasma comprising: a closed vacuum vessel having a longitudinal axis; a generally circular conductive core disposed within said vacuum vessel symmetrically with respect to and along the longitudinal axis of said vacuum vessel, said conductive core having a plurality of electrical currents flowing therein for rapidly generating in an alternating manner first poloidal and toroidal magnetic fields, respectively, about said conductive core so as to form a spheromak plasma; and an inductive transformer disposed radially inwardly of said conductive core and said spheromak plasma and spaced therefrom, said inductive transformer being coaxial with said longitudinal axis of said vacuum vessel, said inductive transformer having a current flowing therein for producing a second poloidal magnetic field about said conductive core, means for rapidly reversing said inductive transformer current and for converting said second poloidal magnetic field to a second toroidal magnetic field about said conductive core for facilitating the formation of and sustaining the spheromak plasma. a closed vacuum vessel having a longitudinal axis; a generally circular conductive core disposed within and symmetrically about the longitudinal axis of said vacuum vessel, said conductive core including current carrying poloidal and toroidal flux coils, means for rapidly reversing the currents in said poloidal and toroidal flux coils in a sequential manner for alternately generating first poloidal and toroidal magnetic fields, respectively, about said conductive core so as to form a spheromak plasma; and inductive transformer means disposed radially inwardly of said circular conductor and said spheromak plasma and spaced therefrom, said inductive transformer being coaxial with said longitudinal axis of said vacuum vessel, said inductive transformer means having a current flowing therein for producing a second poloidal magnetic field about said conductive core, means for rapidly reversing said inductive transformer current and for converting said second poloidal magnetic field is converted to a second toroidal magnetic field about said conductive core for facilitating the formation of and sustaining the spheromak plasma, said inductive transformer means including an elongated coaxial conductor aligned along the longitudinal axis of said vacuum vessel and a plurality of conductive windings positioned on an end of and electrically coupled to said coaxial conductor and disposed generally within said conductive core. a closed vacuum vessel having a longitudinal axis; equilibrium field coil means for producing an equilibrium magnetic field along the longitudinal axis of said vacuum vessel; a generally circular conductive core disposed within and symmetrically about the longitudinal axis of said vacuum vessel, said conductive core including current carrying poloidal and toroidal flux coils, means for rapidly reversing the currents in said poloidal and toroidal flux coils in a sequential manner for alternately generating first poloidal and toroidal magnetic fields, respectively, about said conductive core so as to form a spheromak plasma; a conductive cylinder mounted to an inner wall of said vacuum vessel and aligned with and positioned along the longitudinal axis of said vacuum vessel, said conductive cylinder extending from the vacuum vessel inner wall to within said generally circular conductive core; and inductive transformer means coaxially disposed within and along the length of said conductive cylinder and aligned along the longitudinal axis of said vacuum vessel, said inductive transformer means further extending through said conductive core and having a current flowing therein for producing a second poloidal magnetic field about said conductive core, said conductive cylinder being spaced radially inwardly of both said spheromak plasma and said conductive core, means for rapidly reversing the inductive transformer current and for converting said second poloidal magnetic field to a second toroidal magnetic field about said conductive core for facilitating the formation of and sustaining the spheromak plasma, said inductive transformer means including an elongated coaxial conductor aligned along the longitudinal axis of said vacuum vessel and a plurality of conductive windings positioned on an end of and electrically coupled to said coaxial conductor and disposed generally within said conductive core. 2. Apparatus for forming and sustaining a spheromak plasma comprising: 3. Apparatus for forming and sustaining a spheromak plasma comprising:
claims
1. A beam intensity converting film comprisingone or more graphite films placed such that a surface thereof intersects a beam axis of a charged particle beam,wherein the one or more graphite films have an opening that allows passage of the charged particle beam,wherein the one or more graphite films each have a thickness of 1 μm or greater,wherein, in the one or more graphite films, a thermal conductivity in a surface direction is equal to or greater than 20 times a thermal conductivity in a thickness direction,wherein, in the one or more graphite films, an electric conductivity in a surface direction is equal to or greater than 100 times an electric conductivity in a thickness direction,wherein, in the one or more graphite films, the electric conductivity in the surface direction is 18000 S/cm or greater, andwherein the one or more graphite films have an open area ratio of 10 to 50%, wherein the open area ratio is a ratio of an area of the opening to an area of a surface of the one or more graphite films. 2. The beam intensity converting film according to claim 1, wherein, in each of the one or more graphite films, the thermal conductivity in the surface direction is 1000 W/(m·K) or greater. 3. The beam intensity converting film according to claim 2, wherein, in each of the one or more graphite films, the thermal conductivity in the surface direction is 1600 W/(m·K) or greater. 4. The beam intensity converting film according to claim 1, wherein the one or more graphite films have a density of 1.70 g/cm3 or greater and 2.26 g/cm3 or less. 5. The beam intensity converting film according to claim 4, wherein the one or more graphite films have a density of 2.00 g/cm3 or greater and 2.26 g/cm3 or less. 6. The beam intensity converting film according to claim 1, wherein the one or more graphite films are two or more graphite films, and the beam intensity converting film includes a stack of the two or more graphite films. 7. The beam intensity converting film according to claim 1, wherein the number of times each of the one or more graphite films is folded in an MIT folding endurance test is 1000 or more. 8. A method of producing a beam intensity converting film including one or more graphite films, the method comprisinga step of preparing the one or more graphite films by heat treating one or more polymeric films in a furnace,wherein the one or more graphite films have an opening that allows passage of a charged particle beam;wherein the one or more graphite films each have a thickness of 1 μm or greater,wherein, in the one or more graphite films, a thermal conductivity in a surface direction is equal to or greater than 20 times a thermal conductivity in a thickness direction,wherein, in the one or more graphite films, an electric conductivity in a surface direction is equal to or greater than 100 times an electric conductivity in a thickness direction,wherein, in the one or more graphite films, the electric conductivity in the surface direction is 18000 S/cm or greater, andwherein the one or more graphite films have an open area ratio of 10 to 50%, wherein the open area ratio is a ratio of an area of the opening to an area of a surface of the one or more graphite films.
abstract
A system or method which accesses or otherwise receives collected performance data for at least one server application, where the server application is capable of performing a plurality of transactions with client devices and the client devices are geographically dispersed from the server in known geographical locales, which automatically determines from the performance data which of the transactions are utilized by users of the client devices, which selects utilized transactions according to at least one pre-determined selection criteria, which automatically generates a transaction playback script for each of the selected transactions substituting test information in place of user-supplied or user-unique information in the transactions, which designates each script for execution from a geographical locale corresponding to the locale of the clients which execute the utilized transactions, which deploys the playback scripts to robotic agents geographically co-located with client devices according to the locale designation, and which executes the playback scripts.
051503913
abstract
An exposure apparatus for transferring a pattern of an original onto a workpiece, includes a blocking member for defining a rectangular exposure region with respect to at least one of the original and the workpiece, wherein the exposure for the pattern transfer can be effected with the exposure region defined by the blocking member. Plural detection systems detect a positional deviation between the original and the workpiece, each of which is disposed so as to be associated with at least one of four sides of the rectangular exposure region. Plural first movable stages each is provided so as to be associated with at least one of the four sides, and each is adapted to carry thereon one of the detection systems disposed to be associated with a corresponding side. Each first movable stage comprises a single-axis stage movable in a direction parallel to a corresponding side. Plural second stages each carryies thereon corresponding one of the first movable stages, and each comprises a single-axis stage movable in a direction perpendicular to a corresponding side and in a direction parallel to the rectangular exposure region. Each second movable state is operable to displace the light blocking member to change the rectangular exposure region.
abstract
A canister containing spent fuel assemblies is contained in a body of a transportation cask. A top opening of a vessel body of the canister is closed by a lid welded to the vessel body. A ring-shaped elastic tube is provided between the inner surface of the upper end portion of the body and the outer surface of the upper end portion of the vessel body. The tube seals the gap between these surfaces to prevent a fluid from getting into the gap between the surfaces through the top opening of the body. An inspection space for the insertion of a tester for detecting the welding state of the lid is defined between the inner surface of the upper end portion of the body and the outer surface of the upper end portion of the vessel body.
abstract
Method and apparatus for heating and/or compressing plasmas to thermonuclear temperatures and densities are provided. In one aspect, at least one of at least two plasmoids separated by a distance is accelerated towards the other. The plasmoids interact, for instance to form a resultant plasmoid, to convert a kinetic energy into a thermal energy. The resultant plasmoid is confined in a high energy density state using a magnetic field. One or more plasmoids may be compressed. Energy may be recovered, for example via a blanket and/or directly via one or more coils that create a magnetic field and/or circuits that control the coils.
abstract
Systems and methods of controlling characteristics of a proton beam emitted from a nozzle of a proton treatment system including one or more beam modifying members to define a characteristic of an emitted proton beam, and a clamping member mounted to the nozzle, the clamping member having one or more receiving portions to receive the one or more beam modifying members therein. In some embodiments, the beam modifying members comprise plate structures and the receiving portions include a plurality of slots spaced apart from one another on opposing surfaces of the clamping member to receive opposing ends of the plate structures.
039727726
description
Referring now to the drawing, blowdown water which is produced in the steam generators due to an accumulation of existing impurities conducted to a purifying device 4, 6 is from a non-illustrated blowdown tank as well as a brine cooler through a line 1, in which a measuring orifice 2 and a shut-off valve 3 are connected. The invention of this application is based on the realization that the impurities are formed mainly of iron oxides and salts, so that an electromagnetic precipitation or deposition device in combination with a mixed bed filter is considered basically to be adequate for effecting reclamation of the water. Accordingly, the blowdown is delivered to the electromagnetic filter 4 and emerges therefrom free of ferritic impurities, through line 5. The electromagnetic filter 4 operates in the following manner. The quantities of water to be purified traverse a hollow space which is partly or nearly completely filled with hard-magnetic steel balls, a strong magnetization of the steel balls, preferably far exceeding the magnetic saturation, thereof being produced by relatively high excitation currents, so that the magnetizable impurities then adhere to the hard magnetic balls. From time to time, a rinsing or regeneration of the electromagnetic filter becomes necessary; during the rinsing process, chopped or intermittent direct current of decreasing and alternately opposing polarity, may be used for de-excitation of the filter and, at the same time, rinsing water can be supplied under such pressure and in such quantities that the steel balls are whirled upwardly and perform a dancing motion. From the electromagnetic filter 4, the blowdown is passed through the line 5 to the mixed bed filter 6, the thus purified water being conducted through line 16 and 7 into the machine condenser or into the condensate line or string and thereby returned to the circulatory system of the power plant. If the water mainly contains oxidic impurities, the recycling can be effected by by-passing the mixed bed filter 6, with the shut-off valve 8 closed and the shut-off valve 9 open, through the by-pass 10, a relief valve 11 and a three-way valve 12, as well as through the line 7. On the other hand, ionogenic impurities are removed through the mixed bed filter 6, downstream of which a resin catcher or capturing device 13 is connectible for safety reasons. The rinsing and regeneration of the electromagnetic filter 4 can be effected by means of the water brought in from the non-illustrated brine cooler through the line 1. The mixed bed filter 6 can be regenerated, as indicated diagrammatically by a line 14, with caustic soda solution and, furthermore, as indicated diagrammatically by a line 15, with hydrochloric acid or with sulfuric acid. The lines 14 and 15 are brought in from the water-preparation plant. The rinsing and regenerating waters can be discharged to a non-illustrated neutralizing tank through line 18 from outlet line 16, when the valve 17 is opened. When leakages occur between the primary and the secondary circulatory systems, the discharge of these waters is effected through the line 20 to the waste water preparation installation by opening the valve 19. From the three-way valve 12, a line 21 leads to a main cooling water outlet (not shown).
description
1. Field The present disclosure relates to extreme ultraviolet (“EUV”) light sources that provide EUV light from plasma created by converting a target material. 2. Background Extreme ultraviolet light, e.g., electromagnetic radiation having wavelengths of around 50 nm or less (also sometimes referred to as soft x-rays), and including light at a wavelength of about 13.5 nm, can be used in photolithography processes to produce extremely small features in substrates such as silicon wafers. Methods for generating EUV light include converting a target material from a liquid state into a plasma state. The target material preferably includes at least one element, e.g., xenon, lithium or tin, with one or more emission lines in the EUV range. In one such method, often termed laser produced plasma (“LPP”) the required plasma can be produced by irradiating a target material having the required line-emitting element with a laser beam. One LPP technique involves generating a stream of target material droplets and irradiating at least some of the droplets with laser light pulses. In more theoretical terms, LPP light sources generate EUV radiation by depositing laser energy into a target material having at least one EUV emitting element, such as xenon (Xe), tin (Sn) or lithium (Li), creating a highly ionized plasma with electron temperatures of several 10's of eV. The energetic radiation generated during de-excitation and recombination of these ions is emitted from the plasma in all directions. In one common arrangement, a near-normal-incidence mirror (often termed a “collector mirror”) is positioned to collect, direct (and in some arrangements, focus) the light at an intermediate location, e.g., a focal point. The collected light may then be relayed from the intermediate location to a set of scanner optics and ultimately to a wafer. In quantitative terms, one arrangement that is currently being developed with the goal of producing about 100 W at the intermediate location contemplates the use of a pulsed, focused 10-12 kW CO2 drive laser which is synchronized with a droplet generator to sequentially irradiate about 10,000-200,000 tin droplets per second. For this purpose, there is a need to produce a stable stream of droplets at a relatively high repetition rate (e.g., 10-200 kHz or more). There is also a need to deliver the droplets to an irradiation site with high accuracy and good repeatability in terms of timing and position over relatively long periods of time. To ensure positional accuracy and repeatability, it is necessary to provide a high precision steering system that can release droplets from a range of positions to compensate for other systemic variations, for example, in laser targeting and timing. In this context, the term “steer” includes the concept of varying the position of the release point in at least two dimensions, i.e, with two angular degrees of freedom. It is also desirable to provide a steering system that is high bandwidth and that exhibits high stiffness with little or no hysteresis. Design of a steering system meeting these criteria must also take into account that the droplet generator itself may be relatively massive, for example, on the order of 30 kg. The steering system also preferably operates over a relatively large range of angles, for example, with an actuation range of at least +1-2 degrees. Also, design considerations impose about a 1 micron requirement for position control of the droplets at the plasma location. This imposes a need for micro-radian level precision for the steering system. With the above in mind, applicants disclose systems for steering a droplet generator. The following presents a simplified summary of one or more embodiments in order to provide a basic understanding of the embodiments. This summary is not an extensive overview of all contemplated embodiments, and is not intended to identify key or critical elements of all embodiments nor delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later. In one aspect, the invention is an apparatus including a first member adapted to be coupled to a frame, a second member adapted to receive a droplet generator, and a coupling system mechanically coupling the first member to the second member, wherein the coupling system may include a first coupling subsystem configured to constrain lateral movement between the first member and the second member, and a second coupling subsystem adapted to control an inclination of the second member with respect to the first member. The first coupling subsystem may include a plurality of first coupling subsystem elements mechanically coupling the first member to the second member. Each of the first coupling subsystem elements may include least one flexure, which may be a string flexure. In the case of a first member that is substantially plate-shaped, the string flexure may be oriented substantially parallel to the first member. The second coupling subsystem may include a plurality of second coupling subsystem elements mechanically coupling the first member to the second member. Each of the second coupling subsystem elements may include at least one first flexure which may be a cartwheel flexure. Each of the second coupling subsystem elements may also include at least one second flexure coupled to the at least one first flexure. The at least one second flexure may be a parallelogram flexure. Each of the second coupling subsystem elements may also include at least one linear motor coupled to the first member and to the first flexure. Each of the second coupling subsystem elements may also include at least one second flexure coupled to the at least one first flexure. Each of the second coupling subsystem elements may also include at least piezoelectric element coupled to the second member and to the at least one second flexure. In another aspect, the invention is an apparatus including a plate-shaped first member adapted to a coupled to a frame, a plate-shaped second member adapted to receive a droplet generator; and a coupling system mechanically coupling the first member to the second member, wherein the coupling system may include a first coupling subsystem configured to constrain lateral movement between the first member and the second member, the first coupling subsystem including a plurality of first coupling subsystem elements, each of the first coupling subsystem elements comprising at least one flexure, and a second coupling subsystem adapted to control inclination of the second member with respect to the first member, the first coupling subsystem including a plurality of first coupling subsystem elements, each of the first coupling subsystem elements comprising at a linear combination of a stepper motor coupled to the first member, a first flexure coupled to the stepper motor, a second flexure coupled to the first flexure, and a piezoelectric actuator coupled to the second flexure and to the second member. In yet another aspect, the invention is an apparatus including a first member adapted to a coupled to a frame, a second member adapted to receive a droplet generator; and a coupling system mechanically coupling the first member to the second member, wherein the coupling system may include at least one flexure. In still another aspect, the invention is an apparatus including a source adapted to produce a target of a material in a liquid state and a laser adapted to irradiate the target to change a state of the material from the liquid state to a plasma state to produce EUV light in an irradiation region. The apparatus also includes an optical system adapted to convey the EUV light from the irradiation region to a workpiece. The source includes a target generator and a target generator steering system coupled to the target generator, the target generator steering system including a first member adapted to be fixed relative to the irradiation region, a second member adapted to receive the target generator and adapted to be movable with respect to the irradiation region; and a coupling system mechanically coupling the first member to the second member, wherein the coupling system may include at least one flexure. In still another aspect, the invention is a product made using an apparatus including a source adapted to produce a target of a material in a liquid state, a laser adapted to irradiate the target to change a state of the material from the liquid state to a plasma state to produce EUV light in an irradiation region, and an optical system adapted to convey the EUV light from the irradiation region to a workpiece. The source includes a target generator and a target generator steering system coupled to the target generator, the target generator steering system including a first member adapted to be fixed relative to the irradiation region, a second member adapted to receive the target generator and adapted to be movable with respect to the irradiation region; and a coupling system mechanically coupling the first member to the second member, wherein the coupling system may include at least one flexure. Various embodiments are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to promote a thorough understanding of one or more embodiments. It may be evident in some or all instances, however, that any embodiment described below can be practiced without adopting the specific design details described below. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate description of one or more embodiments. With initial reference to FIG. 1 there is shown a schematic view of an exemplary EUV light source, e.g., a laser produced plasma EUV light source 20 according to one aspect of an embodiment of the present invention. As shown, the EUV light source 20 may include a pulsed or continuous laser source 22, which may for example be a pulsed gas discharge CO2 laser source producing radiation at 10.6 μm. The pulsed gas discharge CO2 laser source may have DC or RF excitation operating at high power and high pulse repetition rate. For example, a suitable CO2 laser source having a MO-PA1-PA2-PA3 configuration is disclosed in. U.S. Pat. No. 7,439,530, issued Oct. 21, 2008, and entitled, LPP EUV LIGHT SOURCE DRIVE LASER SYSTEM, the entire contents of which are hereby incorporated by reference herein. Depending on the application, other types of lasers may also be suitable. For example, a solid state laser, an excimer laser, a molecular fluorine laser, a MOPA configured excimer laser system, e.g., as shown in U.S. Pat. Nos. 6,625,191, 6,549,551, and 6,567,450, an excimer laser having a single chamber, an excimer laser having more than two chambers, e.g., an oscillator chamber and two amplifying chambers (with the amplifying chambers in parallel or in series), a master oscillator/power oscillator (MOPO) arrangement, a power oscillator/power amplifier (POPA) arrangement, or a solid state laser that seeds one or more CO2, excimer or molecular fluorine amplifier or oscillator chambers, may be suitable. Other designs are possible. The EUV light source 20 also includes a target delivery system 24 for delivering target material in the form of liquid droplets or a continuous liquid stream. The target material may be made up of tin or a tin compound, although other materials could be used. The target delivery system 24 introduces the target material into the interior of a chamber 26 to an irradiation region 28 where the target material may be irradiated to produce a plasma. In some cases, an electrical charge is placed on the target material to permit the target material to be steered toward or away from the irradiation region 28. It should be noted that as used herein an irradiation region is a region where target material irradiation may occur, and is an irradiation region even at times when no irradiation is actually occurring. Continuing with FIG. 1, the light source 20 may also include one or more optical elements such as a collector 30. The collector 30 may be a normal incidence reflector, for example, a SiC substrate coated with a Mo/Si multilayer with additional thin barrier layers deposited at each interface to effectively block thermally-induced interlayer diffusion, in the form of a prolate ellipsoid, with an aperture to allow the laser light to pass through and reach the irradiation region 28. The collector 30 may be, e.g., in the shape of a ellipsoid that has a first focus at the irradiation region 28 and a second focus at a so-called intermediate point 40 (also called the intermediate focus 40) where the EUV light may be output from the EUV light source 20 and input to, e.g., an integrated circuit lithography tool 50 which uses the light, for example, to process a silicon wafer workpiece 52 in a know manner. The silicon wafer workpiece 52 is then additionally processed in a known manner to obtain an integrated circuit device. The EUV light source 20 may also include an EUV light source controller system 60, which may also include a laser firing control system 65, along with, e.g., a laser beam positioning system (not shown). The EUV light source 20 may also include a target position detection system which may include one or more droplet imagers 70 that generate an output indicative of the absolute or relative position of a target droplet, e.g., relative to the irradiation region 28, and provide this output to a target position detection feedback system 62. The target position detection feedback system 62 may use this output to compute a target position and trajectory, from which a target error can be computed. The target error can be computed on a droplet-by-droplet basis, or on average, or on some other basis. The target error may then be provided as an input to the light source controller 60. In response, the light source controller 60 can generate a control signal such as a laser position, direction, or timing correction signal and provide this control signal to a laser beam positioning controller (not shown). The laser beam positioning system can use the control signal to control the laser timing circuit and/or to control a laser beam position and shaping system (not shown), e.g., to change the location and/or focal power of the laser beam focal spot within the chamber 26. As shown in FIG. 1, the light source 20 may include a target delivery control system 90. The target delivery control system 90 is operable in response to a signal, for example, the target error described above, or some quantity derived from the target error provided by the system controller 60, to correct for errors in positions of the target droplets within the irradiation region 28. This may be accomplished, for example, by repositioning the point at which the target delivery mechanism 92 releases the target droplets. FIG. 2 shows in greater detail a target delivery mechanism 92 for delivering targets of source material having into a chamber 26. The target delivery system 92 is described in general terms herein because the features and advantages of the invention are independent of the specific details of implementation of the target delivery system 92. For the generalized embodiment shown in FIG. 2, the target delivery mechanism 92 may include a cartridge 143 holding a molten source material such as tin. The molten source material may be placed under pressure by using an inert gas such as argon. The pressure preferably forces the source material to pass through a set of filters 145. From the filters 145, the source material may pass through an open/close thermal valve 147 to a dispenser 148. For example a Peltier device may be employed to establish the valve 147, freezing source material between the filters 145 and dispenser 148 to close the valve 147 and heating the frozen source material to open the valve 147. FIG. 2 also shows that the target delivery system 92 is coupled to a movable member 174 such that motion of the movable member 174 changes the position of the point at which droplets are released from the dispenser 148 in a manner that is described more thoroughly below. For the mechanism 92, one or more modulating or non-modulating source material dispenser(s) 148 may be used. For example, a modulating dispenser may be used having a capillary tube formed with an orifice. The dispenser 148 may include one or more electro-actuatable elements, e.g. actuators made of a piezoelectric material, which can be selectively expanded or contracted to deform the capillary tube and modulate a release of source material from the dispenser 148. As used herein, the term “electro-actuatable element” and its cognates mean a material or structure which undergoes a dimensional change when subjected to a voltage, electric field, magnetic field, or combinations thereof and includes, but is not limited to, piezoelectric materials, electrostrictive materials, and magnetostrictive materials. A heater may be used to maintain the source material in a molten state while passing through the dispenser 148. Examples of modulating droplet dispensers can be found in U.S. Pat. No. 7,838,854, from application Ser. No. 11/067,124 filed on Feb. 25, 2005, entitled METHOD AND APPARATUS FOR EUV PLASMA SOURCE TARGET DELIVERY, U.S. Pat. No. 7,589,337 from application Ser. No. 12/075,631 filed on Mar. 12, 2008, entitled LPP EUV PLASMA SOURCE MATERIAL TARGET DELIVERY SYSTEM, U.S. patent application Ser. No. 11/358,983 filed on Feb. 21, 2006, and entitled, SOURCE MATERIAL DISPENSER FOR EUV LIGHT SOURCE, the entire contents of each of which are hereby incorporated by reference herein. An example of non-modulating droplet dispenser can be found in co-pending U.S. patent application Ser. No. 11/358,988 filed on Feb. 21, 2006, and entitled, LASER PRODUCED PLASMA EUV LIGHT SOURCE WITH PRE-PULSE, the entire contents of each of which are hereby incorporated by reference herein. As shown in FIGS. 3A and 3B, the target delivery mechanism 92 can be mounted on a steering mechanism 170 capable of tilting the target delivery mechanism 92 in different directions to adjust the release point of the droplets and so to reposition the point at which the droplet generator releases droplets thus to control the path the droplets will take into the irradiation region 28. Although in the highly conceptual representation of FIGS. 3A and 3B the tilt is in the plane of the figure, one of ordinary skill in the art will readily appreciate that the tilt may in fact be in any direction. The present specification refers to this process as “steering” the droplet generator. In applications where such steering is desirable, it is clear that the droplet generator must be movable with respect to the other components and reference points in the system, and, in particular, the irradiation region 28 and that a mechanical coupling system 102 must be interposed between the droplet generator and the other components of the system so as to allow for such movement. Proper steering of the droplet generator (and, hence, of the droplets it generates) requires a coupling system that is highly precise and repeatable and which exhibits a low amount of hysteresis. It is also preferable that the coupling be very responsive, i.e., have a high bandwidth. As mentioned, the coupling preferably meets these requirements despite manipulating a relatively massive load, that is, the droplet generator 92, which can typically weigh on the order of 30 kg. According to the present embodiment, a coupling capable of having these attributes is realized in the form of a device having a fixed member 172 fixedly coupled to a stationary element in the system such as a wall of chamber 26 and a movable member 174 coupled to the target delivery mechanism (droplet generator) 92. The fixed member 172 and the movable member 174 are in turn coupled by a coupling system 176. The coupling system 176 preferably includes a first coupling subsystem 178 (elements 178a, 178b, and 178c) that reduces or eliminates any relative translational (e.g. sliding) motion of the movable member 174 relative to the fixed member 172 as well as relative rotations of the movable member 174 relative to the fixed member 172 around the device axis, while at the same time allowing the movable member 174 to tilt with respect to the fixed member 172. Stated another way, taking a three-dimensional cartesian coordinate system with the x and y axes lying in the plane of a substantially planar plate-like fixed member 172 and the z axis 182 passing through the release point of the target delivery mechanism (droplet generator) 92 when the release point is in a neutral (zero tilt) position as shown in FIG. 3A, the first coupling subsystem restrains translation in the x and y directions and rotation about the z axis. It will be understood by one of ordinary skill in the art that the terms “plate” and as used herein simply refer to a structural element to which other elements may be connected, such as a base or a frame, and is not limited to structural elements that are necessarily flat or substantially planar. The coupling system 176 also preferably includes a second coupling subsystem 180 (elements 180a, 180b, and 180c in FIG. 4) that includes one or linear combinations of coupling elements and motor elements coupling the fixed member 172 and the movable member 174 and providing a force having a tendency to tilt the movable member 174 with respect to the fixed member 172. The motor elements may be any element that produces a force, including but not limited to linear motors, stepper motors, piezoelectric actuators, or some combination of these. As mentioned, the first coupling subsystem 178 and second coupling subsystem 180 are configured to cooperate to permit relative tilting or inclination of the fixed member 172 and the movable member 174. Because the target delivery mechanism 92 is preferably rigidly coupled to the movable member 174, tilting the movable member 174 with respect to the fixed member 172 steers the target delivery mechanism 92, that is, alters the position of the droplet generator release point. This is shown in FIG. 3B. FIG. 4 is another conceptual representation of steering system according to another aspect of the invention. As depicted there, the steering system has a first coupling subsystem 178 made up of coupling elements 178a, 178b, and 178c arranged at corresponding locations around the respective peripheries of fixed member 172 and the movable member 174. The first coupling subsystem 178 in the arrangement of FIG. 4 has three coupling elements, but it will be apparent to one having ordinary skill in the art that other numbers of coupling elements could be used. Also in the arrangement of FIG. 4 the coupling elements 178a, 178b, and 178c are positioned symmetrically. In the particular arrangement of FIG. 4 they are positioned with 120 degree rotational symmetry about a central axis of the device (a line passing through the centers of the two circular apertures which accommodate the droplet generator.) It will be apparent to one having ordinary skill in the art that if a symmetric arrangement is used, other symmetries could be followed. Also in FIG. 4, the steering system has a second coupling subsystem 180 made up of coupling elements 180a, 180b, and 180c arranged at corresponding locations around the respective peripheries of fixed member 172 and the movable member 174. The second coupling subsystem 180 in the arrangement of FIG. 4 has three coupling elements, but it will be apparent to one having ordinary skill in the art that other numbers of coupling elements could be used. Also in the arrangement of FIG. 4 the coupling elements 180a, 180b, and 180c are positioned symmetrically. In the particular arrangement of FIG. 4 they are positioned with 120 degree rotational symmetry about a central axis of the device (a line passing through the centers of the two circular apertures.) It will be apparent to one having ordinary skill in the art that if a symmetric arrangement is used, other symmetries could be followed. In the arrangement of FIG. 4 the positions of the coupling elements of the second coupling subsystem 180 alternate with the coupling elements of the first coupling subsystem 178 around the periphery of the fixed member 172 and the movable member 174. As mentioned, the coupling system 176, which includes the first coupling subsystem 178 and the second coupling subsystem 180, serves at least two functions. One function is to restrain certain types of relative movements between the fixed member 172 and the movable member 174, such as a sliding or translational movement, while at the same time permitting a tilting motion. Another function is to cause a tilting motion between the two plates. One advantage of the present invention is that these two functions can be carried out by two separate subsystems. For example, the first coupling subsystem 178 can perform the function of permitting tilting while restraining other kinds of motions. The second coupling subsystem 180 can perform the function of inducing a tilting motion. This permits each of the two subsystems to be designed in such a way as to optimize its performance of its respective function without the need to address constraints that would otherwise be imposed by having the same coupling subsystem perform both functions. According to another aspect of the present invention, the first and second coupling subsystems employ flexures as coupling elements. One of ordinary skill in the art will appreciate that some connectors used to mechanically couple one structural element to another use rigid parts that mechanically mate with one another. Hinges, sliders, universal joints, and ball-and-socket joints are examples of this type of rigid connector or coupling. Such connectors permit a variety of kinematic degrees of freedom between the parts they connect. They suffer from the disadvantage, however, that the clearance between mating parts of these rigid joints can introduce positional error caused by backlash, that is, motion lost to clearance when a driving direction is reversed and contact between mating surfaces must be reestablished before relative motion continues. Further, operation of these connectors necessarily involves relative motion of their parts causing friction that leads to wear and undesirably increased clearances. A kinematic chain of such connectors results in an aggregation of individual errors from backlash and wear, resulting in limited accuracy and repeatability. For some applications, the problems associated with rigid connectors can be avoided or overcome by the use of so-called flexures. Flexures are also known as by a variety of names including flexible joints, flexible couplings, flexure pivots, flex connectors, living joints, and compliant joints. Unlike the rigid couplings described above, flexible joints generally are not comprised of rigid elements having a clearance between them. Rather flexures utilize the inherent compliance of a material under deformation. Flexures thus eliminate friction, backlash, and wear. This permits excellent accuracy and repeatability. In addition, making the flexure from a unitary monolithic material can simplify production and facilitate low-cost fabrication. In one aspect, the present invention provides a high bandwidth, high-precision, high-stiffness, hysteresis-free steering system for an EUV droplet generator through the use of flexures that are flexible enough to provide the required range of motion yet strong enough to be compatible with the preload forces required to achieve the needed stiffness. At the same time, it permits fabrication of a steering system that is not so massive as to reduce system resonance frequencies which would be undesirable in the context of steering the droplet generator. In another aspect, the invention uses two or more coupling subsystems each of which uses flexures to remove unwanted degrees of freedom while providing the required stiffness (or, equivalently, a sufficiently high mechanical resonance frequency). According to this aspect of the invention, the first coupling subsystem 178 includes two or more, and preferably three, coupling elements, each of which includes a first flexure element 190. In the embodiment shown in FIG. 5, the first flexure element 190 is a “string flexure.” FIG. 5 shows only one first coupling subsystem element 178a for purposes of clear presentation but one of ordinary skill in the art will readily appreciate that additional first coupling subsystem elements may be present as suggested by FIG. 4. In systems where the fixed member 172 and the movable member 174 are configured as substantially parallel plates, the first flexure element 190 is oriented approximately parallel to the stationary plate and the movable plate. This is shown in FIG. 5, where the first coupling subsystem 178 is made up of a first flexure element 190 one end of which is coupled to a triangular strut member 192. The triangular strut member 192 is fixed to the movable member 174. The other end of the first flexure element 190 is connected to a bracket 194 which is in turn attached to the fixed member 172. In addition, the end of the first flexure element 190 attached to the triangular strut member 192 is also attached to a bracket 196 which is in turn attached to the fixed member 172. The first flexure element 190 is attached to the bracket 196 through a joint arrangement 198 which allows for two degrees of freedom and through a spring 200 that pre-loads the first flexure element 190. The first coupling subsystem 178 provides a stiff connection between the fixed member 172 and the movable member 174 by limiting or even substantially eliminating translation, i.e., parallel sliding of the two plates with respect to each other, as well as rotations in the plane parallel to the plates. At the same time, the first coupling subsystem 178 allows for relative tilt of the plates with respect to each other. The second coupling subsystem 180 is preferably made up of two or more series combinations of flexures and one or more motive devices. Here and elsewhere in this specification the term “series combination” is intended to refer to a linear configuration in which the elements are arranged in an ordered series, each to the next, so that their overall effect is essentially additive. Also, the term “motive device” is intended to refer to any device capable of generating a motive force and includes without limitation linear motors, linear actuators, stepping motors, and piezoelectric elements. In a particular configuration each coupling element of the second coupling subsystem 180 includes a linear combinations of elements. Again, FIG. 5 shows only one second coupling subsystem element 180a for purposes of clear presentation but one of ordinary skill in the art will readily appreciate that additional second coupling subsystem elements may be present as suggested by FIG. 4. As shown in FIG. 5 the second coupling subsystem element 180a may include a linear motor 202, a second flexure element 204, a third flexure element 206, and a piezoelectric actuator 208 (atop the second flexure element 206; occluded by movable member 174 in FIG. 5 but visible in FIG. 10). This is one possible configuration. It will be readily appreciated by one of ordinary skill in the art that other elements could be used or that the same or other elements could be used in a different order. In the configuration shown in FIG. 5, the linear motor 202 is rigidly coupled to the fixed member 172 and the piezoelectric actuator 208 is rigidly coupled to the movable member 174 to provide for coarse and fine motion, respectively. The linear motor 202 is mechanically connected to the piezoelectric actuator 208 through the second and third flexure elements 204, 206. In a particular embodiment, the second flexure element 204 may be a so-called “cartwheel” flexure as shown and described more fully below. The third flexure element 206 may be a “double” or “parallelogram” flexure as shown and described more fully below. The second coupling subsystem 180 allows control of x and y rotation and z translation of the movable member 174 relative to the fixed member 172. The second flexure element 204 allows some lateral relative movement of the movable member 174 relative to the fixed member 172, such that the motion can be pivoting about a fixed point in space which is near the axis of the device but below the fixed member 172 (i.e. towards the release point of droplet generator). At the same time the second flexure element 204 provides stiffness against translations along the long (z) axis of the droplet generator and allow for small misalignments between the linear motor 202 and the movable member 174. The third flexure element 206 allows the piezoelectric actuator 208 to exert a force on the movable member 174 without applying any lateral moment to the piezoelectric actuator 208. This is preferred for piezoelectric transducers because of their relative brittleness. It will be appreciated that the specific materials, dimensions, and forms of the first flexure element 190 and the second flexure element 204, and the third flexure element 204 are preferably chosen for the three types of flexures so that the desired range of motion can be achieved while meeting stiffness and fatigue stress requirements. For example, when a string flexure is used as the first flexure element 190 it may be configured as shown in FIGS. 6A, 6B, and 6C. As can be seen, the first flexure element of these figures has two narrowed portions to permit flexing side-to-side or up-and-down. The overall dimensions of the first flexure element 190 will vary according to the specific application. One of a number of materials could be used to make the first flexure element 190. As one example, the first flexure element 190 could be made of heat treated stainless steel. As an additional example, when a cartwheel flexure is used as the second flexure element 204 it may be configured as shown in FIGS. 7A and 7B. As can be seen, the second flexure element 204 of these figures has two flexible leaves intersecting at their mid points. The example in FIGS. 7A and 7B shows a second flexure element 204 made up of three sections, each of which comprises a cartwheel flexure, but one of ordinary skill in the art will readily appreciate that one, two, or some other number of sections can be used. The overall dimensions of the second flexure element 204 will vary according to the specific application. One of a number of materials could be used to make the second flexure element 204. As one example, the second flexure element 204 could be made of stainless steel. As a third example, when a parallelogram flexure is used as the third flexure element 206 it may be configured as shown in FIGS. 8A and 8B. As can be seen, the third flexure element 206 of these figures is generally box shaped with a lower portion of the box serving as a platform and the upper part of the box serving as a cantilevered beam. The platform and beam are integral with one another and also interact through a series of internal ridges and gaps which permit the cantilevered beam to flex in a direction corresponding to up and down in the figure. The example in FIGS. 8A and 8B shows a particular configuration for third flexure element 206 but one of ordinary skill in the art will readily appreciate other flexure configurations can be used. The overall dimensions of the third flexure element 206 will vary according to the specific application. One of a number of materials could be used to make the third flexure element 206. As one example, the third flexure element 206 could be made of heat treated stainless steel. FIG. 9 shows an embodiment of a droplet generator according to the invention where the first coupling subsystem 178 is depicted as including coupling elements 178a, 178b, and 178c arranged at corresponding locations around the respective periphery of fixed member 172 (the movable member 174 being omitted from the drawing to make the piezoelectric actuator 208 more visible. The first coupling subsystem 178 in the arrangement of FIG. 9 has three coupling elements, but it will be apparent to one having ordinary skill in the art that other numbers of coupling elements could be used. Also in the arrangement of FIG. 9 the coupling elements 178a, 178b, and 178c are positioned symmetrically. In the particular arrangement of FIG. 9 they are positioned with 120 degree rotational symmetry about a central axis of the device (a line passing through the centers of the two circular apertures which accommodate the droplet generator.) It will be apparent to one having ordinary skill in the art that if a symmetric arrangement is used, other symmetries could be followed. Also, each coupling element is depicted as including a first flexure element 190 connected as described in connection with FIG. 5. The embodiment depicted in FIG. 9 also includes shows an embodiment of a droplet generator according to the invention that includes a second coupling subsystem 180 made up of coupling elements 180a, 180b, and 180c arranged at corresponding locations around the respective periphery of fixed member 172. The second coupling subsystem 180 in the arrangement of FIG. 9 has three coupling elements, but it will be apparent to one having ordinary skill in the art that other numbers of coupling elements could be used. Also in the arrangement of FIG. 9 the coupling elements 180a, 180b, and 180c are positioned symmetrically. In the particular arrangement of FIG. 9 they are positioned with 120 degree rotational symmetry about a central axis of the device (a line passing through the centers of the two circular apertures.) It will be apparent to one having ordinary skill in the art that if a symmetric arrangement is used, other symmetries could be followed. In the arrangement of FIG. 9 the positions of the coupling elements of the second coupling subsystem 180 alternate with the coupling elements of the first coupling subsystem 178 around the periphery of the fixed member 172. Also, each coupling element is depicted as including a linear motor, second flexure element, third flexure element, and piezoelectric actuator 208 connected as described in connection with FIG. 5. What has been described above includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is construed when employed as a transitional word in a claim. Furthermore, although elements of the described aspects and/or embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any aspect and/or embodiment may be utilized with all or a portion of any other aspect and/or embodiment, unless stated otherwise.
claims
1. A method of accelerating an ion beam having an initial energy to a final higher energy and final direction while substantially eliminating contaminant ions and neutral atoms having energies other than the final energy, the method comprising:generating a beam of ions at an initial energy, guiding the ion beam along an ion beam path;controlling and adjusting the electrostatic potential and electric fields along the beam path so as to cause the ion beam to follow a generally s-shaped path while being accelerated, so that the ions in the ion beam are accelerated to the final energy and a centroid of the beam after acceleration travels generally in the final direction; andintercepting undeflected neutral atoms or molecules and/or charged fragmented molecular ions so as to remove them from the ion beam. 2. The method of claim 1 wherein the beam is deflected by a set of electrodes that provide two opposed successive sideways components on an accelerator field to provide the generally s-shaped path. 3. The method of claim 2 wherein the deflections each amount to an angle of at least 10 degrees. 4. The method of claim 1 wherein beam stops are utilized to intercept the undeflected ions. 5. The method of claim 1 wherein the energy of the beam is raised beyond the desired final energy, then retarded to the final energy in a short, approximately straight, final decelerating gap. 6. A method of decelerating an ion beam having an initial energy to a final higher energy and final direction while substantially eliminating contaminant ions and neutral atoms having energies other than the final energy, the method comprising:generating a beam of ions at an initial energy, guiding the ion beam along an ion beam path;controlling and adjusting the electrostatic potential and electric fields along the beam path so as to cause the ion beam to follow a generally s-shaped path while being decelerated, so that the ions in the ion beam are decelerated to the final energy and a centroid of the beam after acceleration travels generally in the final direction; andintercepting undeflected neutral atoms or molecules and/or charged fragmented molecular ions so as to remove them from the ion beam. 7. The method of claim 6 wherein the beam is deflected by a set of electrodes that provide two opposed successive sideways components on an accelerator field to provide the generally s-shaped path. 8. The method of claim 7 wherein the deflections each amount to an angle of at least 10 degrees. 9. The method of claim 6 wherein beam stops are utilized to intercept the undeflected ions. 10. The method of decelerating an ion beam wherein the energy of the beam is slightly increased prior to deceleration according to the method of claim 6, thereby preventing the acceleration of unwanted particles of opposite charge to the desired ions. 11. A system of accelerating an ion beam having an initial energy to a final higher energy and final direction while substantially eliminating contaminant ions and neutral atoms having energies other than the final energy, the system comprising:means for generating a beam of ions at an initial energy, guiding the ion beam along an ion beam path;means for controlling and adjusting the electrostatic potential and electric fields along the beam path so as to cause the ion beam to follow a generally s-shaped path while being accelerated, so that the ions in the ion beam are accelerated to the final energy and a centroid of the beam after acceleration travels generally in the final direction; andmeans for intercepting undeflected neutral atoms or molecules and/or charged fragmented molecular ions so as to remove them from the ion beam. 12. The system of claim 11 wherein the beam is deflected by a set of electrodes that provide two opposed successive sideways components on an accelerator field to provide the generally s-shaped path. 13. The system of claim 12 wherein the deflections each amount to an angle of at least 10 degrees. 14. The system of claim 11 wherein beam stops are utilized to intercept the undeflected ions. 15. The system of claim 11 wherein the energy of the beam is raised beyond the desired final energy, then retarded to the final energy in a short, approximately straight, final decelerating gap. 16. A system of decelerating an ion beam having an initial energy to a final higher energy and final direction while substantially eliminating contaminant ions and neutral atoms having energies other than the final energy, the system comprising:means for generating a beam of ions at an initial energy, guiding the ion beam along an ion beam path;means for controlling and adjusting the electrostatic potential and electric fields along the beam path so as to cause the ion beam to follow a generally s-shaped path while being decelerated, so that the ions in the ion beam are decelerated to the final energy and a centroid of the beam after acceleration travels generally in the final direction; andmeans for intercepting undeflected neutral atoms or molecules and/or charged fragmented molecular ions so as to remove them from the ion beam. 17. The system of claim 16 wherein the beam is deflected by a set of electrodes that provide two opposed successive sideways components on an accelerator field to provide the generally s-shaped path. 18. The system of claim 17 wherein the deflections each amount to an angle of at least 10 degrees. 19. The system of claim 16 wherein beam stops are utilized to intercept the undeflected ions. 20. The system of decelerating an ion beam wherein the energy of the beam is initially raised beyond the desired final energy, then retarded to the final energy gy using the system of claim 16. 21. An ion implantation apparatus comprising:an ion source, an extraction assembly for extracting an ion beam;a magnetic analyzer for separating unwanted ion species from a traveling ribbon ion beam; anda target chamber in which is mounted a target for implantation, Illustratively, the target is a semiconductor wafer or flat panel display, which is moved through the beam (optionally back and forth) along a single path; wherein the beam is ribbon shaped, with one dimension many times greater than the other, and the longer dimension is aligned with the non-dispersive plane of the magnetic analyzer. 22. The on implantation apparatus of claim 21 wherein the magnetic analyzer comprises:central axis and intended arc pathway for a ribbon ion beam as it travels, said central axis having a curvilinear shape;an arcuate yoke construct encompassing said predetermined curvilinear shaped central axis and surrounding said intended arc pathway for the continuous ribbon ion beam as it travels, said arcuate yoke construct being formed at least in part of a ferromagnetic material and comprising an arcuate wall structure having fixed dimensions and a substantially rectangular cross-section, two discrete open ends which serve as an entrance and exit for the traveling beam, and an internal spatial region of determinable volume which serves as a spatial passageway for the traveling beam; anda mirror symmetrical pair of discrete loop-shaped coils utilized as an aligned array. 23. The on implantation apparatus of claim 22 wherein each discrete coil of the pair in the aligned array (i) is an elongated complete loop comprised at least in part of electrically conductive material, (ii) is an elongated complete loop having two rounded and inclined discrete loop ends, each of which is bent in the same direction, and (iii) is an elongated complete loop formed as a set of multiple conductive segments placed in sequential series wherein each segment lies at a pre-chosen sequence position and individual angle orientation with respect to the central axis and intended arc pathway for the ribbon ion beam as it travels within said internal spatial region of said arcuate yoke construct. 24. The ion implantation apparatus of claim 23 wherein the aligned array of two looped-shaped coils set in mirror symmetry (iv) presents a bend direction for the two rounded inclined ends of one looped-shaped coil which is opposite to the bend direction for the two rounded inclined ends of the other looped-shaped coil in the pair, (v) provides a central open spatial channel via the cavity volume of the closed loop in each of the two coils, said central open spatial channel extending from each pair of inclined rounded loop ends to the other over the linear dimensional distance of the array, (vi) is positioned within said internal spatial region along the interior surfaces of two opposing walls of said arcuate yoke construct such that one pair of oppositely bent inclined loop ends extends from and lies adjacent to each of the two open ends of said arcuate yoke construct, (vii) serves as limiting boundaries for said curvilinear central axis and intended arc pathway for the continuous ribbon ion beam as it travels in the gap space between said two loop-shaped coils after being positioned within said internal spatial region of said arcuate yoke construct. 25. The ion implantation apparatus of claim 22 wherein in order to create a magnetic field with good uniformity, without excessive stray field, the field is generated by at least two coils or symmetric sets of coils, which are of saddle shape, one above and one below the beam, wherein the region of uniform field is bounded by the coil windings. 26. The ion implantation apparatus of claim 22 in which the arc pathway includes, an arc with a radius ranging between about 0.25 and 2 meters, and an angle of curvature ranging from not less than about 45 degrees to not more than about 110 degrees of curvature.
summary
summary
description
The present disclosure relates to the technical field of reactor engineering, and particularly, to a nuclear power plant spent fuel negative pressure unloading system. China is currently actively developing pebble bed modular high temperature gas-cooled reactor nuclear power plant. High temperature reactor nuclear power plant is recognized as a nuclear power plant with main features of the fourth generation of nuclear power plants, which has advantages of inherent safety, preventing nuclear proliferation, producing high temperature process heat and so forth. High temperature gas-cooled reactor can be divided into two categories according to the shape of fuel elements. One category is the pebble bed high temperature gas-cooled reactor which utilizes spherical fuel elements, and the other category is the prismatic high temperature gas-cooled reactor which utilizes prismatic fuel elements. Both the spherical fuel element and the prismatic fuel element are dispersed with coated fuel particles, and the diameter of the coated fuel particles is about 1 mm. The spherical fuel element is made by thoroughly mixing a certain amount of fuel particles and matrix graphite, pressing the mixture into graphite pebbles with a diameter of 50 mm, and then wrapping and pressing a layer of pure graphite on their outside as a housing of the fuel element, and the pressed fuel element has an outer diameter of 60 mm. Fissile material in the fuel elements of the pebble bed high temperature gas-cooled reactor will release a large quantity of heat, that is, nuclear energy, in the fission process. When fissile material is consumed to a certain extent, it will become spent fuel, which is mainly characterized in that it has a strong radioactivity and needs radiation shielding. The spherical spent fuel discharged from the reactor core of the pebble bed high temperature gas-cooled reactor requires the use of a suitable unloading system, which loads the spent fuel element discharged from the reactor into a storage canister suitable for storage of the spherical fuel element, sealing the storage canister after filling it up, and then storing it in a suitable storage facility. The technical problem to be solved by the present disclosure is to solve the problem of how to safely unload spent fuel elements discharged from a reactor. In order to solve the technical problem above, the present disclosure provides a nuclear power plant spent fuel negative pressure unloading system, comprising a fuel element transport pipe and a gas transport pipe. The fuel element transport pipe comprises a fuel element output pipe, a fuel element lifting pipe, and a fuel element unloading pipe connected in series. The fuel element unloading pipe is arranged obliquely downward in the direction of movement of a fuel element. The distal end of the fuel element unloading pipe is connected sequentially to a fuel loading apparatus and a transfer apparatus. The gas transport pipe is connected at either end thereof respectively to set positions of the fuel element output pipe and the fuel element unloading pipe. A gas driving mechanism is connected to the gas transport pipe. An inlet of the gas driving mechanism is arranged at an end in proximity to the fuel element unloading pipe for sucking gas in the fuel element transport pipe, the fuel loading apparatus and the transfer apparatus and releasing the gas to the fuel element output pipe via the gas transport pipe so as to drive the movement of the fuel element. According to the present disclosure, an iodine adsorber is installed between the end of the gas transport pipe in proximity to the fuel element unloading pipe and the gas driving mechanism. According to the present disclosure, a dust filter is installed between the end of the gas transport pipe in proximity to the fuel element unloading pipe and the gas driving mechanism. According to the present disclosure, an outlet pipe in parallel with the gas transport pipe is connected to the outlet of the gas driving mechanism for connecting with the atmosphere. According to the present disclosure, the fuel elements comprise spent fuel elements and graphite pebble elements. According to the present disclosure, a radiation measuring instrument is installed at the inlet of the fuel element output pipe, the fuel loading apparatus and the transfer apparatus comprise a graphite pebble loading apparatus and a graphite pebble transfer apparatus connected sequentially and a spent fuel loading apparatus and a spent fuel transfer apparatus connected sequentially, an element dispenser is installed at the distal end of the fuel element unloading pipe, and the two outlets of the element dispenser are connected with the graphite pebble loading apparatus and the spent fuel loading apparatus through pipes, respectively. According to the present disclosure, ball valves are installed on the pipes through which the two outlets of the element dispenser are connected with the graphite pebble loading apparatus and the spent fuel loading apparatus respectively, for controlling opening and closing of the pipes. According to the present disclosure, the fuel loading apparatus comprises a feeding pipe, a fuel loading pipe, a lifting slider and a driving motor; a canister plug claw is installed in the fuel loading pipe, a cylinder is installed above the fuel loading pipe, a telescopic rod of the cylinder is connected with the canister plug claw, and a fuel discharging port is fixed to the lower end of the fuel loading pipe; one end of the feeding pipe is connected with the distal end of the fuel element unloading pipe, and the other end is connected with the fuel loading pipe; the cylinder is connected to the lifting slider, and the driving motor is used to drive the lifting slider to move up and down. According to the present disclosure, the transfer apparatus comprises a storage canister, a shield top cover, a shield cylindrical body, a movable bottom plate which realizes opening and closing of the shield cylindrical body by drawing, a moving mechanism which drives the storage canister to move in two vertical directions, and a hoisting system for hoisting the storage canister, wherein the shield top cover and the shield cylindrical body are connected and fixed, the movable bottom plate is located at the bottom of the shield cylindrical body for supporting the storage canister, and a shield fuel loading port is installed on the shield top cover. According to the present disclosure, a vent which is connected with an air intake pipe is set on the movable bottom plate; and a vent which is connected with an air exhaust pipe is set on the shield top cover. The above-mentioned technical solution of the present disclosure has the following advantages as compared with the prior art: the nuclear power plant spent fuel negative pressure unloading system provided by the present disclosure is a closed system, and the oxygen content in the system is very little. During spent fuel loading, even if the temperature of the spent fuel is high, the spent fuel element will not undergo significant oxidation due to high temperature, thereby guaranteeing the integrity of the fuel elements within the transfer apparatus. The spent fuel negative pressure unloading system in the present disclosure has maintained a negative pressure state for the fuel element transport pipe, the fuel loading apparatus and the transfer apparatus in the fuel loading process, which can effectively prevent the uncontrollable release of graphite dust and radioactive gases generated in the spent fuel and ensure that the graphite dust is retained by the dust filter and the radioactive gases can be adsorbed by the iodine adsorber, thereby guaranteeing the safety of the spent fuel loading system. 1: gas transport pipe; 2: radiation measuring instrument; 3: first gas diverter; 4: first ball counter; 5: fourth ball counter; 6: second ball valve; 7: second ball counter; 8: second gas diverter; 9: third ball counter; 10: first ball valve; 11: element dispenser; 12: dust filter; 13: iodine adsorber; 14: forth globe valve; 15: second fan; 16: fifth globe valve; 17: ventilation device room; 18: sixth globe valve; 19: first fan; 20: second globe valve; 21: third globe valve; 22: first globe valve; 23: third ball valve; 24: fifth ball counter; 26: spent fuel loading apparatus; 27: air exhaust pipe; 28: shield cylindrical body; 29: trolley; 30: small wheel group; 31: air intake pipe; 32: movable bottom plate; 33: spent fuel storage canister; 34: large wheel group; 35: bridge; 36: railcar; 37: auxiliary driving motor; 38: graphite pebble storage canister; 39: graphite pebble loading apparatus; 42: shield top cover; 43: hanger; 51: hoisting hoister group; 52: pulley; 53: wire rope; 54: trolley rail; 55: bridge rail; 60: upper panel; 61: primary driving motor; 62: walking wheel group; 63: longitudinal rail; 64: fixed mount; 65: sliding bracket; 71: slider driving motor; 72: cylinder; 73: feeding pipe; 74: lifting slider; 75: fuel loading skew tee; 75-1: shield cylindrical body; 76: fuel loading pipe; 77: fuel element discharging port; 81: spherical head plate; 82: elliptic head plate; 83: nozzle; 84: top plate; 85: supporting rib; 86: supporting bottom plate, 87: fuel element transport pipe; 88: fuel element output pipe; 89: fuel element lifting pipe; 90: fuel element unloading pipe; 91: transfer apparatus; 92: gas driving mechanism; 93: outlet pipe; 92O: outlet of the gas driving mechanism; 94: spent fuel transfer apparatus; 11O: two outlets of the element dispenser; 11P: the pipes through which the two outlets of the element dispenser are connected; 95: canister plug claw; 96: telescopic rod; 97: moving mechanism; 98: shield fuel loading port; 99: vent which is connected with the air intake pipe; 100: vent which is connected with the air exhaust pipe. In order to make the purposes, technical solutions and advantages of the embodiments of the present disclosure more clear, hereinafter, apparent and full descriptions for the technical solutions in the embodiments of the present disclosure will be made in combination with the drawings in the embodiments of the present disclosure. It is apparent that the described embodiments are a part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all of other embodiments obtained by those of ordinary skilled in the art without creative work belong to the scope of the present disclosure. As illustrated in FIG. 1, a nuclear power plant spent fuel negative pressure unloading system provided by an embodiment of the present disclosure comprises a fuel element transport pipe 87 and a gas transport pipe 1, and specifically, the fuel element in the present embodiment comprises spent fuel element and graphite pebble element. The fuel element transport pipe 87 comprises fuel element output pipe 88, fuel element lifting pipe 89, and fuel element unloading pipe 90 connected in series. The fuel element lifting pipe 89 is arranged vertically for lifting fuel element at a lower position to a certain height for subsequent unloading processing. The fuel element unloading pipe 90 is arranged obliquely downward in the direction of fuel element movement. The distal end of the fuel element unloading pipe 90 is connected sequentially to fuel loading apparatus and a transfer apparatus 91; specifically, a radiation measuring instrument 2 is installed at the inlet of the fuel element output pipe 88, the fuel loading apparatus and the transfer apparatus 91 comprise a graphite pebble loading apparatus 39 and a graphite pebble transfer apparatus connected sequentially and a spent fuel loading apparatus 26 and a spent fuel transfer apparatus 94 connected sequentially, an element dispenser 11 is installed at the distal end of the fuel element unloading pipe 90, and the two outlets 11O of the element dispenser 11 are connected with the graphite pebble loading apparatus 39 and the spent fuel loading apparatus 26 through pipes, respectively. The gas transport pipe 1 is connected at either end thereof respectively to set positions on the fuel element output pipe 88 and the fuel element unloading pipe 90. Specifically, a first gas diverter 3 is installed at the junction of the gas transport pipe 1 and the fuel element output pipe, and the first gas diverter 3 allows driving gas to enter into the fuel element transport pipe 87 from the gas transport pipe 1. A second gas diverter 8 is installed at the junction of the gas transport pipe 1 and the fuel element unloading pipe 90, and the first gas diverter 8 allows driving gas to flow into the gas transport pipe 1 from the fuel element transport pipe 87. A gas driving mechanism 92 is connected onto the gas transport pipe 1. In the present embodiment, the gas driving mechanism 92 utilizes a fan. An inlet of the fan is arranged at an end in proximity to the fuel element unloading pipe 90 for sucking gas in the fuel element transport pipe 87, the fuel loading apparatus and the transfer apparatus 91 and releasing the gas to the fuel element output pipe via the gas transport pipe 1 so as to drive the movement of the fuel element. Specifically, a fourth ball counter 4 is installed between the first gas diverter 3 on the fuel element output pipe and the fuel element lifting pipe 89 for counting the number of fuel elements discharged from the reactor. A second ball counter 7 is installed at the upper part of the fuel element lifting pipe 89 for counting the number of fuel elements successfully lifted to the upper part of the fuel element lifting pipe 89. A third ball counter 9 is installed between the gas diverter on the fuel element unloading pipe 90 and an element dispenser 11 for counting the total number of the fuel elements unloaded to the fuel loading apparatus. A first ball valve 10 is installed between the third ball counter 9 and the first ball valve 10 for controlling opening and closing of the fuel element transport pipe 87 and the fuel loading apparatus. In use, starting the fan, and the fuel elements discharged from the reactor enter the fuel element lifting pipe 89 from the fuel element output pipe 88 under the driving of gas and are further lifted to the fuel element unloading pipe 90. The gas flows into the fan via the second gas diverter 8. Since the fuel element unloading pipe 90 is arranged obliquely downward, the fuel elements can enter into the fuel loading apparatus and the transfer apparatus 91 under the influence of inertia and gravity. Since the radiation measuring instrument 2 is installed at the inlet of the fuel element output pipe 88, the element dispenser 11 can determine the type of the element based on the detection results of the radiation measuring instrument 2, thereby transporting the spent fuel elements with strong radiation to the spent fuel loading apparatus 26 and transporting the graphite pebble elements with little radiation to the graphite pebble loading apparatus 39. The nuclear power plant spent fuel negative pressure unloading system provided by the present disclosure is a sealed system, and the oxygen content in the system is very little. During spent fuel loading, even if the temperature of the spent fuel is high, the spent fuel element will not undergo significant oxidation due to high temperature, thereby guaranteeing the integrity of the fuel elements within the transfer apparatus 91. It can be realized that the spent fuel elements and the graphite pebble elements are loaded simultaneously and can be loaded into the spent fuel transfer apparatus 94 and the graphite pebble transfer apparatus respectively for separate storage by the radiation measuring instrument 2 and the element dispenser 11 installed at the inlet of the fuel element output pipe 88. Further, an iodine adsorber 13 is installed between the end of the gas transport pipe 1 in proximity to the fuel element unloading pipe 90 and the fan, and a dust filter 12 is also installed between the end of the gas transport pipe 1 in proximity to the fuel element unloading pipe 90 and the fan. The gas flows into the dust filter 12 installed in the ventilation device room 17 after flowing out of the fuel element transport pipe 87. The graphite dust in the gas can be filtered cleanly, and radioactive materials in the gas can be absorbed as the gas flows through the iodine adsorber 13. The spent fuel negative pressure unloading system in the embodiment of the present disclosure can maintain a negative pressure state in the fuel element transport pipe 87, the fuel loading apparatus and the transfer apparatus 91 in fuel loading process, which can effectively prevent the uncontrollable release of graphite dust and radioactive gases generated in the spent fuel and ensure that the graphite dust is retained by the dust filter 12 and the radioactive gases can be absorbed by the iodine adsorber 13, thereby guaranteeing the safety of the spent fuel loading system. Further, an outlet pipe that is connected in parallel with the gas transport pipe 1 is connected to the outlet of the fan for connecting the atmosphere. Specifically, two fans are installed in parallel on the gas transport pipe 1, that is, a first fan 19 and a second fan 15, respectively. A first globe valve 22 is installed at the inlet of the first fan 19, a second globe valve 20 is installed on the pipe where the outlet of the first fan 19 is connected with the atmosphere, a third globe valve 21 is installed on the pipe where the outlet of the first fan 19 is connected with the gas transport pipe 1, a fourth globe valve 14 is installed at the inlet of the second fan 15, a fifth globe valve 16 is installed on the pipe where the outlet of the first fan 19 is connected with the atmosphere, and a sixth globe valve 18 is installed on the pipe where the outlet of the first fan 19 is connected with the gas transport pipe 1. Since the outlet of the first fan 19 is connected with external environment by the second globe valve 20, and the external environment is of one atmospheric pressure, the gas pressure in the fuel element transport pipe 87 can be adjusted to be lower than the atmospheric pressure through adjusting the opening degree of the second globe valve 20, thereby realizing negative pressure closed fuel loading function of the spent fuel. It can start an alternate second fan 15 and complete operating switch of the fan group by closing the first fan 19 and the first globe valve 22 on its front and the third globe valve 21 on its rear, opening the fourth globe valve 14 in front of the second fan 15 and the sixth globe valve 18 on the rear of the second fan 15 and starting the second fan 15. The two sets of the installed fan group satisfy redundant design requirements for the ventilation system, and improve the operating reliability of the ventilation system and the safety of the spent fuel unloading system. Further, ball valves are installed on the pipes 11P through which the two outlets 11O of the element dispenser 11 are connected with the graphite pebble loading apparatus 39 and the spent fuel loading apparatus 26 respectively, that is, a second ball valve 6 and a third ball valve 23 respectively, for controlling opening and closing of respective pipes. Specifically, a fourth ball counter 5 is installed on the pipe between the second ball valve 6 and the graphite pebble loading apparatus, and a fifth ball counter 24 is installed on the pipe between the third ball valve 23 and the spent fuel loading apparatus 26. The fourth ball counter 5 is used to count the number of the elements which enter into the graphite pebble transfer apparatus through the graphite pebble loading apparatus 39, and the fifth ball counter 24 is used to count the number of elements which enter into the spent fuel transfer apparatus 94 through the spent fuel loading apparatus 26. Further, the first ball valve 10, the second ball valve 6 and the third ball valve 23 are driven by electric apparatus and can be remotely controlled and operated. Further, as illustrated in FIG. 2, the spent fuel loading apparatus 26 and the graphite pebble loading apparatus 39 comprises a feeding pipe 73, a fuel loading pipe 76, a lifting slider 74 and a driving motor 71; a canister plug claw 95 is installed in the fuel loading pipe 76, a cylinder 72 is installed above the fuel loading pipe 76, a telescopic rod 96 of the cylinder 72 is connected with the canister plug claw 95, and a fuel discharging port 77 is fixed to the lower end of the fuel loading pipe 76; one end of the feeding pipe 73 is connected with the distal end of the fuel element unloading pipe 90, and the other end is connected with the fuel loading pipe 76; specifically, a fuel loading skew tee 75 is also installed at the junction of the fuel loading pipe 76 and the feeding pipe 73, and the other outlet of the fuel loading skew tee 75 is a drawing pebble port from which the fuel elements can be drawn. The cylinder 72 is fixedly connected to the lifting slider 74, and the driving motor 71 is used to drive the lifting slider 74 to move up and down by a screw. Specifically, the spent fuel loading apparatus 26 is similar to the graphite pebble loading apparatus 39, but the spent fuel loading apparatus 26 also comprises a radiation shielding cylindrical body 75-1 installed on the external side of the fuel loading skew tee 75. The spent fuel loading apparatus 26 and the graphite pebble loading apparatus 39 provided in the embodiment of the present disclosure can dock with the nozzle of the spent fuel storage canister 33 and the graphite pebble storage canister 38 in seal way, which is not only flexible and reliable, but also can effectively guarantees the sealing property of the spent fuel negative pressure unloading system. Further, as illustrated in FIG. 1 and FIG. 4, the transfer apparatus 91 comprises a storage canister, a shield top cover 42, a shield cylindrical body 28, a movable bottom plate 32 which realizes opening and closing of the shield cylindrical body 28 by drawing, a moving mechanism 97 which drives the storage canister to move in two vertical directions, and a hoisting system for hoisting the storage canister, wherein the shield top cover 42 and the shield cylindrical body 28 are connected and fixed, the movable bottom plate 32 is located at the bottom of the shield cylindrical body 28 for supporting the storage canister. Specifically, in the present embodiment, the movable bottom plate 32 is preferably a drawing bottom plate which can be drawn to both sides. A shield fuel loading port 98 is installed on the shield top cover 42. The hoisting system comprises: pulleys 52, which installed on the outer surface of the shield cover; hoisting hoister groups 51, the number of which matches the number of the pulleys 52, and the hoisting hoister groups are installed outside of the shield cylindrical body 28; and a hanger 43, which is installed in the inner cavity of the shield cylindrical body 28, connected to the hoisting hoister groups 51 by wire ropes 53 for hoisting the spent fuel storage canister 33. In the present disclosure, it is provided with 4 pulleys 52. 4 wire ropes 53 extended from the two sets of the hoisting hoister groups 51 enter into the internal cavity of the shield cylindrical body 28 through channels for wire ropes 53 installed on the shield top cover 42 after passing the pulleys 52 and are fixedly installed on the hangers 43. The two sets of the hoisting hoister groups 51 can satisfy the single failure criteria and ensure the safety and reliability of the hoisting operation of the storage canister. Specifically, the graphite pebble transfer apparatus does not have radiation, the design of the shield is omitted. Moreover, in order to simplify the structure of the unloading system, the hoisting system is not designed in the graphite pebble transfer apparatus. When it is required to hoist the graphite pebble storage canister 38, it is moved to the hoisting port of the spent fuel transfer apparatus 94 for hoisting. Specifically, as illustrated in FIG. 3, the spent fuel storage canister 33 and the graphite pebble storage canister 38 both have cylindrical body, an elliptic head plate 82 is installed on the upper part of the cylindrical body and a spherical head plate 81 is installed on the bottom of the cylindrical body. A top plate 84 is installed on the top of the cylindrical body, and a nozzle 83 is installed at the middle position of the elliptic head plate 82. Supporting bottom plates 86 with a circumferentially uniform arrangement are installed on the bottom of the cylindrical body of the spent fuel storage canister 33. Supporting ribs 85 with a circumferentially uniform arrangement are also installed between the supporting bottom plate 86 and the spherical head plate 81. The supporting ribs 85 not only plays a role of supporting the storage canister, but also plays a role of buffering in the falling process of the storage canister, thereby protecting the integrity of the storage canister. The spent fuel storage canister 33 and the graphite pebble storage canister are both made of stainless steel material, which have advantages of long service life, good impact resistance, reliable sealing, and easy to lift and transport, thereby realizing long-term safe storage of the spent fuel elements and the graphite pebble elements. Further, as illustrated in FIG. 4, the spent fuel storage canister 33 moving mechanism, which can drive the spent fuel storage canister 33 to move in two vertical directions, comprising a bridge 35 and a trolley 29, which is perpendicular to each other, and a bridge rail 55 and a trolley rail 54, which is perpendicular to each other also. The trolley rail 54 is installed on the bridge 35, a small wheel group 30 of the trolley 29 can operate laterally on the bridge 35 along the trolley rail 54, and a large wheel group 34 of the bridge 35 can operates longitudinally on the ground along the bridge rail 55. A through hole is set on the trolley 29, the shield cylindrical body is fixed in the through hole of the trolley 29, and the hoisting hoister group 51 is also fixed on the upper surface of the trolley 29. Further, as illustrated in FIG. 5, the graphite pebble storage canister 38 moving mechanism, which can drive the graphite pebble storage canister 38 to move in two vertical directions, comprising a railcar 36 and a longitudinal rail 63. The railcar 36 comprises an upper panel 60 and a walking wheel group 62 matching with the longitudinal rail 63. The railcar 36 also comprises an auxiliary driving motor 37, which can drive the upper panel 60 to move laterally, and a primary driving motor 61, which can drive the railcar 36 to move along the longitudinal rail 63. A fixed mount 64 of the graphite pebble storage canister 38 is also installed on the upper plate 60 of the railcar 36. In the loading process of the graphite pebble elements, the graphite pebble storage canister 38 can be placed in its fixed mount 64. A sliding bracket 65 is also installed on the upper plate 60 of the railcar 36 for power supply and control for the railcar 36 in moving process. Further, as illustrated in FIG. 1, a vent 99 connected to an air intake pipe 31 is set on the movable bottom plate 32, and a vent 100 connected to an air exhaust pipe 27 is set on the shield top cover 42. The vent 99 on the movable bottom plate 32 and the vent 100 on the shield top cover 42 can realize ventilation of the storage canister. The vent 99 on the movable bottom plate 32 is used to introduce cooling air from the outside, and the fan installed on the top cover of the shield cylindrical body 28 can discharge residual heat of the storage canister to the air exhaust pipe 27, and thus discharge the residual heat to the outside atmosphere. It can realize safe radiation shield for the spent fuel storage canister 33 by disposing the shield cylindrical body 28, the shield top cover 42 and the movable bottom plate 32, and it can efficiently discharge the residual heat of the spent fuel storage canister 33 in fuel loading process through the air intake pipe 31 and the air exhaust pipe 27. The spent fuel storage canister 33 can be transported to each designated position by using of the moving mechanism 97 which drives the spent fuel storage canister 33 to move in two vertical directions, thereby completing any operation of hoisting and loading of the spent fuel storage canister 33. It can realize reliable fixing and precise positioning of the graphite pebble storage canister 38, which can be transported to each designated position, and complete any operation of hoisting and loading of the graphite pebble storage canister 38 by disposing the moving mechanism 97 which drives the graphite pebble storage canister 38 to move in two vertical directions. The specific operating flow of the structural schematic diagram of the nuclear power plant spent fuel negative pressure unloading system of the embodiment of the present disclosure is as follows: Firstly, hoisting the spent fuel storage canister 33 into the shield cylindrical body 28 by the hanger 43, and placing it on the movable bottom plate 32. Moving and positioning the shield cylindrical body 28 to the spent fuel loading position by the bridge 35 and the trolley 29, and start-up the fan installed on the top cover of the shield cylindrical body 28 to suck cooling air from the air intake pipe 31 and discharge it to the outside atmosphere through the residual heat exhaust pipe 27 so as to discharge the residual heat emitted from the spent fuel storage canister 33. Operating the slider driving motor 71 on the spent fuel loading apparatus 26 to drive the lifting slider 74 to move downward, which drives the cylinder 72 and the fuel loading pipe 76 and other parts to move downward, insert the fuel loading pipe 76 into the center hole on the top cover of the shield cylindrical body 28, connect the fuel element discharging port 77 with the nozzle 83 of the spent fuel storage canister 33 within the shield cylindrical body 28, and drive canister plug claw 95 to slide up and down by the cylinder 72, thereby taking out and putting back the canister plug of the spent fuel storage canister 33. Then, hoisting the graphite pebble storage canister 38 onto the railcar 36, placing the graphite pebble storage canister 38 into its fixed mount 64, and moving and positioning the graphite pebble storage canister 38 to the graphite pebble loading position by operation of the primary driving motor 61 and the auxiliary driving motor 37 of the railcar 36. The operating steps of operating the graphite pebble loading apparatus are similar to that of operating the spent fuel loading apparatus, which needs to connect the fuel element discharging port 77 with the nozzle 83 of the spent fuel storage canister 33. After that, opening the first globe valve 22 in front of the first fan 19 and the third globe valve 21 on the rear of the first fan 19, closing the fourth globe valve 14 in front of the second fan 15 and the sixth globe valve 18 on the rear of the second fan 15, starting the first fan 19, and adjusting the second globe valve 20 to a suitable opening degree, so that the transport speed of the spent fuel elements can satisfy design requirements. The transport speed of the spent fuel elements can be read out from several ball counters at different positions. Opening the first ball valve 10, the second ball valve 6 and the third ball valve 23 on the spent fuel element transport pipe 87. Whether or not the fuel elements discharged from the reactor have radiation can be determined at the radiation measuring instrument 2. According to the result of radiation measurement, if it is determined to be a spent fuel element, the element dispenser 11 operates, so that the fuel element unloading pipe 90 is connected to the spent fuel loading apparatus 26, and then the spent fuel element is transported to the downstream of the first gas diverter 3 and lifted to the top from the fuel element lifting pipe 89 behind the ball counters under the driving of gas in the gas transport pipe 1 above the first gas diverter 3, and after that, the spent fuel element flows out of the fuel element transport pipe 87 under the action of inertia and gravity, and is loaded into the spent fuel storage canister 33 in the shield cylindrical body 28 through the spent fuel loading apparatus 26, thereby completing the fuel loading operation for the spent fuel element. After the spent fuel storage canister 33 is filled up with the spent fuel elements and undergoes sealing processing, it is transported to a storage silo by the moving mechanism 97 which drives the spent fuel storage canister 33 to move in two vertical directions and hoisted into the storage silo by the hanger 43 for storage. If the fuel elements discharged from the reactor is determined to be a graphite pebble element at the radiation measuring instrument 2, the element dispenser 11 operates, so that the fuel element unloading pipe 90 is connected to the graphite pebble loading apparatus 39, and then the graphite pebble element is transported to the downstream of the first gas diverter 3 and lifted to the top from the fuel element lifting pipe 89 behind the ball counters under the driving of gas in the gas transport pipe 1 above the first gas diverter 3, and after that, the graphite pebble element flows out of the fuel element transport pipe 87 under the action of inertia and gravity, and is loaded into the graphite pebble storage canister 38 by the graphite pebble loading apparatus 39, thereby completing the fuel loading operation for the graphite pebble element. After the graphite pebble storage canister 38 is filled up with the graphite pebble elements and undergoes sealing processing, it is transported to a hoisting port by the moving mechanism 97 which drives the graphite pebble storage canister 38 to move in two vertical directions and hoisted into the shield cylindrical body 28 through operation of the hanger 43, and then it is transported to a storage silo through the moving mechanism 97 which drives the spent fuel storage canister 33 to move in two vertical directions and hoisted into the silo by the hanger 43 for storage. After the driving gas flows into the fuel element transport pipe 87 from the upper end of the first gas diverter 3, it drives the fuel elements to transport forward and lifts the fuel elements to the top of the transport pipe from the fuel element lifting pipe 89 behind the ball counters. And then, the gas flows out of the gas transport pipe 1 above the second gas diverter 8 mounted on the fuel element unloading pipe 90. After that, the driving gas flows into the dust filter 12 in the ventilation device room, where the graphite dust in the driving gas is filtered cleanly. After clean air flows out of the dust filter 12, the radioactive material in the air is absorbed in the iodine adsorber 13. After that, the gas flows through the first globe valve 22 in front of the first fan 19, and then flows into the first fan 19, and the gas is pressurized by the first fan 19, after that the gas flows through the third globe valve 21 on the rear of the first fan 19, then the gas flows back to the upper inlet of the first gas diverter 3 through the gas transport pipe 1, and then the gas flows into the fuel element transport pipe 87 again, thereby completing a closed circulation. Since the outlet of the first fan 19 is connected with external environment by the second globe valve 20, and the external environment is of one atmospheric pressure, the gas pressure in the fuel element transport pipe 87 can be adjusted to be lower than the atmospheric pressure by adjusting the opening degree of the second globe valve 20, thereby realizing negative pressure closed fuel unloading function of the spent fuel. It can start-up an alternate second fan 15 and complete operating switch of the fan group by closing the first fan 19 and the first globe valve 22 on its front and the third globe valve 21 on its rear, opening the fourth globe valve 14 in front of the second fan 15 and the sixth globe valve 18 on the rear of the second fan 15, and then the second fan 15 can be started-up. In summary, the nuclear power plant spent fuel negative pressure unloading system of the present disclosure has the following advantages: 1. The nuclear power plant spent fuel negative pressure unloading system provided by the present disclosure is a sealed system, and the oxygen content in the system is very little. During spent fuel unloading period, even if the temperature of the spent fuel is high, the spent fuel element will not undergo significant oxidation due to high temperature, thereby guaranteeing the integrity of the fuel elements within the transfer apparatus. It can be realized that the spent fuel elements and the graphite pebble elements are unloaded into the spent fuel transfer apparatus and the graphite pebble transfer apparatus simultaneously and respectively for separate storage through the usage of the radiation measuring instrument and the element dispenser installed at the inlet of the fuel element output pipe. 2. The spent fuel negative pressure unloading system provided in the present disclosure can maintain a negative pressure state for the fuel element transport pipe, the fuel loading apparatus and the transfer apparatus in the fuel unloading process, which can effectively prevent the uncontrollable release of graphite dust and radioactive gases generated in the spent fuel and ensure that the graphite dust is retained in the dust filter and the radioactive gases can be absorbed in the iodine adsorber, thereby guaranteeing the safety of the spent fuel unloading system. 3. The two sets of the installed fan group of the spent fuel negative pressure unloading system provided in the present disclosure can satisfy redundant design requirements for the ventilation system, and can improve the operating reliability of the ventilation system and the safety of the spent fuel unloading system. 4. The spent fuel loading apparatus and the graphite pebble loading apparatus of the spent fuel negative pressure unloading system provided in the present disclosure can be sealed when docking with the nozzle of the spent fuel storage canister and the graphite pebble storage canister, which is not only flexible and reliable, but also can effectively guarantee the sealing property of the spent fuel negative pressure unloading system. 5. The spent fuel negative pressure unloading system provided in the present disclosure can realize safe radiation shield of the spent fuel storage canister by disposing the shield cylindrical body, the shield top cover and the movable bottom plate. It can efficiently discharge the residual heat of the spent fuel storage canister in the loading process by disposing the air intake pipe and the air exhaust pipe. The spent fuel storage canister can be transported to each designated position by disposing the moving mechanism which drives the spent fuel storage canister to move in two vertical directions, thereby completing any operation of hoisting and loading of the spent fuel storage canister. It can realize reliable fixing and precise positioning of the graphite pebble storage canister, which can be transported to each designated position, and complete any operation of hoisting and loading of the graphite pebble storage canister by disposing the moving mechanism which drives the graphite pebble storage canister to move in two vertical directions. The spent fuel negative pressure unloading system described in the embodiment in the present disclosure, which is used for a pebble bed high temperature reactor nuclear power plant, can also be used for spent fuel transport and unloading of other similar nuclear power plants by suitable modification. Finally, it is to be noted that the embodiments above are only used to explain the technical solutions of the present disclosure, and are not intended to be limiting thereto; although the present disclosure has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skilled in the art that the technical solutions described in the foregoing embodiments may be modified or equivalently replaced with some of the technical features; while these modifications or replacements do not make the essence of corresponding technical solutions to depart from the spirit and scope of various embodiments of the present disclosure.
description
The present application is a divisional of U.S. patent application Ser. No. 14/289,525 filed May 28, 2014 which claims the benefit of U.S. Provisional Patent Application No. 61/827,943 filed May 28, 2013. U.S. patent application Ser. No. 14/289,525 is further a continuation-in-part of International Patent Application No. PCT/US13/42070 filed May 21, 2013, which claims the benefit of U.S. Provisional Patent Application No. 61/649,593 filed May 21, 2012; the entireties of all of the foregoing disclosures being incorporated herein by reference. The present invention relates nuclear reactors, and more particularly to a reactor and reactor containment system with passive reactor cooling system for reactor shutdown operation. The containment for a nuclear reactor is defined as the enclosure that provides environmental isolation to the nuclear steam supply system (NSSS) of the plant in which nuclear fission is harnessed to produce pressurized steam. A commercial nuclear reactor is required to be enclosed in a pressure retaining structure which can withstand the temperature and pressure resulting from the most severe accident that can be postulated for the facility. The most severe energy release accidents that can be postulated for a reactor and its containment can be of two types. First, an event that follows a loss-of-coolant accident (LOCA) and involve a rapid large release of thermal energy from the plant's nuclear steam supply system (NSSS) due to a sudden release of reactor's coolant in the containment space. The reactor coolant, suddenly depressurized, would violently flash resulting in a rapid rise of pressure and temperature in the containment space. The in-containment space is rendered into a mixture of air and steam. LOCAs can be credibly postulated by assuming a sudden failure in a pipe carrying the reactor coolant. Another second thermal event of potential risk to the integrity of the containment is the scenario wherein all heat rejection paths from the plant's nuclear steam supply system (NSSS) are lost, forcing the reactor into a “scram.” A station black-out is such an event. The decay heat generated in the reactor must be removed to protect it from an uncontrolled pressure rise. More recently, the containment structure has also been called upon by the regulators to withstand the impact from a crashing aircraft. Containment structures have typically been built as massive reinforced concrete domes to withstand the internal pressure from LOCA. Although its thick concrete wall could be capable of withstanding an aircraft impact, it is also unfortunately a good insulator of heat, requiring pumped heat rejection systems (employ heat exchangers and pumps) to reject its unwanted heat to the external environment (to minimize the pressure rise or to remove decay heat). Such heat rejection systems, however, rely on a robust power source (off-site or local diesel generator, for example) to power the pumps. The station black out at Fukushima in the wake of the tsunami is a sobering reminder of the folly of relying on pumps. The above weaknesses in the state-of-the-art call for an improved nuclear reactor containment system. Besides the foregoing containment cooling issues, a nuclear reactor continues to produce a substantial quantity of heat energy after it has been shut down. FIG. 20 shows a typical heat generation curve of a light water reactor subsequent to a scram (i.e., a sudden cessation of chain reaction by a rapid insertion of control rods or other means). In the current reactor designs, as noted above, the reactor's decay heat is removed by the plant's residual heat removal (RHR) system which utilizes a system of pumps and heat exchangers to convey the heat energy to a suitable source of cooling water maintained by the plant. As can be seen from FIG. 20, the reactor's decay heat begins to attenuate exponentially with time but is still quite significant to threaten the reactor's safety if the generated heat were not removed (as was the case at Fukushima where the pumps needed to extract the reactors' heat failed because of submergence of their electric motors in the tsunami driven water surge). The Fukushima disaster provided a stark lesson in the vulnerability of forced flow (pump dependent) systems under extreme environmental conditions. An improved reactor cooling system is desired. A reactor cooling system according to the present disclosure provides a completely passive means to reject the reactor's decay heat without any reliance on and drawbacks of pumps and motors requiring an available electric power supply, as described above. In one embodiment, the cooling system relies entirely on gravity and varying fluid densities to induce flow through the cooling system. In one embodiment, this gravity driven system may be configured and referred to as a submerged bundled cooling system (SBCS) for convenience (this arbitrary nomenclature not being limiting in any respect). The cooling system is engineered to passively extract heat from the reactor primary coolant in the event of a station black out or another postulated accident scenario wherein the normal heat rejection path from the fuel core via the power plant's Rankine cycle is lost. In one embodiment, a passive nuclear reactor shutdown cooling system includes a reactor vessel housing a nuclear fuel core inside, the reactor vessel containing a primary coolant heated by the fuel core, and a steam generator fluidly coupled to the reactor vessel and containing a liquid secondary coolant. The primary coolant circulates in a first closed flow loop between the reactor vessel and steam generator, the primary coolant transferring heat to the secondary coolant in the steam generator and producing secondary coolant steam. A heat exchanger includes an inventory of a liquid third coolant and a tube bundle, the tube bundle being submerged in the third coolant. The secondary coolant circulates via gravity flow in a second closed flow loop between the submerged tube bundle and the steam generator. The secondary coolant steam is extracted from the steam generator and flows in the second closed flow loop to the tube bundle, condenses forming condensate, and the condensate flows back to the steam generator. In another embodiment, a passive nuclear reactor shutdown cooling system includes a reactor vessel housing a nuclear fuel core inside, the reactor vessel containing a primary coolant heated by the fuel core, and a heat exchanger including an inventory of cooling water and a tube bundle, the tube bundle being submerged in the cooling water. The primary coolant circulates via gravity flow in a first closed flow loop between the submerged tube bundle and the reactor vessel, wherein the primary coolant transfers heat to the inventory of cooling water in the heat exchanger and is cooled before flowing back to the reactor vessel. In another embodiment, a method for passively cooling a nuclear reactor after shutdown is provided. The method includes: heating a primary coolant in a reactor vessel with a nuclear fuel core; heating a secondary coolant in a steam generator with the heated primary coolant to produce secondary coolant steam; extracting the secondary coolant steam from the steam generator; flowing the extracted secondary coolant steam through a tube bundle submerged in an inventory of cooling water in a pressure vessel; condensing the secondary coolant steam forming a secondary coolant condensate; and returning the secondary coolant condensate to the steam generator, wherein the secondary coolant steam and condensate circulates through a first closed flow loop between the tube bundle and steam generator. In one embodiment, the method further includes: heating of the cooling water in the pressure vessel by the secondary coolant steam; converting a portion of the cooling water into steam phase; extracting the cooling water steam from the pressure vessel; flowing the extracted cooling water steam through heat dissipater ducts attached to a reactor containment vessel in thermal communication with a heat sink; condensing the cooling water steam; and returning the condensed cooling water to the pressure vessel to replenish the inventory of cooling water. Another method for passively cooling a nuclear reactor after shutdown is provided. The method includes: heating a primary coolant in a reactor vessel with a nuclear fuel core; extracting the heated primary coolant from the reactor vessel; flowing the heated primary coolant through a tube bundle submerged in an inventory of cooling water in a pressure vessel; cooling the heated primary coolant to lower its temperature; and returning the cooled primary coolant to the reactor vessel, wherein the primary coolant circulates through a first closed flow loop between the tube bundle and reactor vessel. In one embodiment, the method further includes: heating of the cooling water in the pressure vessel by the secondary coolant steam; converting a portion of the cooling water into steam phase; extracting the cooling water steam from the pressure vessel; flowing the extracted cooling water steam through heat dissipater ducts attached to a reactor containment vessel in thermal communication with a heat sink; condensing the cooling water steam; and returning the condensed cooling water to the pressure vessel to replenish the inventory of cooling water. According to other aspects, the present invention further provides nuclear reactor containment system that overcomes the deficiencies of the foregoing arrangements for rejecting heat released into the environment within the containment by a thermal event. The containment system generally includes an inner containment vessel which may be formed of steel or another ductile material and an outer containment enclosure structure (CES) thereby forming a double walled containment system. In one embodiment, a water-filled annulus may be provided between the containment vessel and the containment enclosure structure providing an annular cooling reservoir. The containment vessel may include a plurality of longitudinal heat transfer fins which extend (substantially) radial outwards from the vessel in the manner of “fin”. The containment vessel thus serves not only as the primary structural containment for the reactor, but is configured and operable to function as a heat exchanger with the annular water reservoir acting as the heat sink. Accordingly, as further described herein, the containment vessel advantageously provides a passive (i.e. non-pumped) heat rejection system when needed during a thermal energy release accident such as a LOCA or reactor scram to dissipate heat and cool the reactor. In one embodiment according to the present disclosure, a nuclear reactor containment system includes a containment vessel configured for housing a nuclear reactor, a containment enclosure structure (CES) surrounding the containment vessel, and an annular reservoir formed between the containment vessel and containment enclosure structure (CES) for extracting heat energy from the containment space. In the event of a thermal energy release incident inside the containment vessel, heat generated by the containment vessel is transferred to the annular reservoir which operates to cool the containment vessel. In one embodiment, the annular reservoir contains water for cooling the containment vessel. A portion of the containment vessel may include substantially radial heat transfer fins disposed in the annular reservoir and extending between the containment vessel and containment enclosure structure (CES) to improve the dissipation of heat to the water-filled annular reservoir. When a thermal energy release incident occurs inside the containment vessel, a portion of the water in the annulus is evaporated and vented to atmosphere through the containment enclosure structure (CES) annular reservoir in the form of water vapor. Embodiments of the system may further include an auxiliary air cooling system including a plurality of vertical inlet air conduits spaced circumferentially around the containment vessel in the annular reservoir. The air conduits are in fluid communication with the annular reservoir and outside ambient air external to the containment enclosure structure (CES). When a thermal energy release incident occurs inside the containment vessel and water in the annular reservoir is substantially depleted by evaporation, the air cooling system becomes operable by providing a ventilation path from the reservoir space to the external ambient. The ventilation system can thus be viewed as a secondary system that can continue to cool the containment ad infinitum. According to another embodiment, a nuclear reactor containment system includes a containment vessel configured for housing a nuclear reactor, a containment enclosure structure (CES) surrounding the containment vessel, a water filled annulus formed between the containment vessel and containment enclosure structure (CES) for cooling the containment vessel, and a plurality of substantially radial fins protruding outwards from the containment vessel and located in the annulus. In the event of a thermal energy release incident inside the containment vessel, heat generated by the containment vessel is transferred to the water filled reservoir in the annulus through direct contact with the external surface of the containment vessel and its fins substantially radial thus cooling the containment vessel. In one embodiment, when a thermal energy release incident occurs inside the containment vessel and water in the annulus is substantially depleted by evaporation, the air cooling system is operable to draw outside ambient air into the annulus through the air conduits to cool the heat generated in the containment (which decreases exponentially with time) by natural convection. The existence of water in the annular region completely surrounding the containment vessel will maintain a consistent temperature distribution in the containment vessel to prevent warping of the containment vessel during the thermal energy release incident or accident. In another embodiment, a nuclear reactor containment system includes a containment vessel including a cylindrical shell configured for housing a nuclear reactor, a containment enclosure structure (CES) surrounding the containment vessel, an annular reservoir containing water formed between the shell of the containment vessel and containment enclosure structure (CES) for cooling the containment vessel, a plurality of external (substantially) radial fins protruding outwards from the containment vessel into the annulus, and an air cooling system including a plurality of vertical inlet air conduits spaced circumferentially around the containment vessel in the annular reservoir. The air conduits are in fluid communication with the annular reservoir and outside ambient air external to the containment enclosure structure (CES). In the event of a thermal energy release incident inside the containment vessel, heat generated by the containment vessel is transferred to the annular reservoir via the (substantially) radial containment wall along with its internal and external fins which operates to cool the containment vessel. Advantages and aspects of a nuclear reactor containment system according to the present disclosure include the following: Containment structures and systems configured so that a severe energy release event as described above can be contained passively (e.g. without relying on active components such as pumps, valves, heat exchangers and motors); Containment structures and systems that continue to work autonomously for an unlimited duration (e.g. no time limit for human intervention); Containment structures fortified with internal and external ribs (fins) configured to withstand a projectile impact such as a crashing aircraft without losing its primary function (i.e. pressure & radionuclide (if any) retention and heat rejection); and Containment vessel equipped with provisions that allow for the ready removal (or installation) of major equipment through the containment structure. All drawings are schematic and not necessarily to scale. The features and benefits of the invention are illustrated and described herein by reference to illustrative embodiments. This description of illustrative embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description of embodiments disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the nominal orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a rigorously specific orientation denoted by the term. Terms such as “attached,” “affixed,” “connected,” “coupled,” “interconnected,” and similar refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. Accordingly, the disclosure expressly should not be limited to such illustrative embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features. Referring to FIGS. 1-15, a nuclear reactor containment system 100 according to the present disclosure is shown. The system 100 generally includes an inner containment structure such as containment vessel 200 and an outer containment enclosure structure (CES) 300 collectively defining a containment vessel-enclosure assembly 200-300. The containment vessel 200 and containment enclosure structure (CES) 300 are vertically elongated and oriented, and define a vertical axis VA. In one embodiment, the containment vessel-enclosure assembly 200-300 is configured to be buried in the subgrade at least partially below grade (see also FIGS. 6-8). The containment vessel-enclosure assembly 200-300 may be supported by a concrete foundation 301 comprised of a bottom slab 302 and vertically extending sidewalls 303 rising from the slab forming a top base mat 304. The sidewalls 303 may circumferentially enclose containment vessel 200 as shown wherein a lower portion of the containment vessel may be positioned inside the sidewalls. In some embodiments, the sidewalls 303 may be poured after placement of the containment vessel 200 on the bottom slab 302 (which may be poured and set first) thereby completely embedding the lower portion of the containment vessel 200 within the foundation. The foundation walls 303 may terminate below grade in some embodiments as shown to provide additional protection for the containment vessel-enclosure assembly 200-300 from projectile impacts (e.g. crashing plane, etc.). The foundation 301 may have any suitable configuration in top plan view, including without limitation polygonal (e.g. rectangular, hexagon, circular, etc.). In one embodiment, the weight of the containment vessel 200 may be primarily supported by the bottom slab 302 on which the containment vessel rests and the containment enclosure structure (CES) 300 may be supported by the base mat 304 formed atop the sidewalls 303 of the foundation 301. Other suitable vessel and containment enclosure structure (CES) support arrangements may be used. With continuing reference to FIGS. 1-15, the containment structure vessel 200 may be an elongated vessel including a hollow cylindrical shell 204 with circular transverse cross-section defining an outer diameter D1, a top head 206, and a bottom head 208. In one embodiment, the containment vessel 200 (i.e. shell and heads) may be made from a suitably strong and ductile metallic plate and bar stock that is readily weldable (e.g. low carbon steel). In one embodiment, a low carbon steel shell 204 may have a thickness of at least 1 inch. Other suitable metallic materials of corresponding appropriate thickness including various alloys may be used. The top head 206 may be attached to the shell 204 via a flanged joint 210 comprised of a first annular flange 212 disposed on the lower end or bottom of the top head and a second mating annular flange 214 disposed on the upper end or top of the shell. The flanged joint 210 may be a bolted joint, which optionally may further be seal welded after assembly with a circumferentially extending annular seal weld being made between the adjoining flanges 212 and 214. The top head 206 of containment vessel 200 may be an ASME (American Society of Mechanical Engineers) dome-shaped flanged and dished head to add structural strength (i.e. internal pressure retention and external impact resistance); however, other possible configurations including a flat top head might be used. The bottom head 208 may similarly be a dome-shaped dished head or alternatively flat in other possible embodiments. In one containment vessel construction, the bottom head 208 may be directly welded to the lower portion or end of the shell 204 via an integral straight flange (SF) portion of the head matching the diameter of shell. In one embodiment, the bottom of the containment vessel 200 may include a ribbed support stand 208a or similar structure attached to the bottom head 208 to help stabilize and provide level support for the containment vessel on the slab 302 of the foundation 301, as further described herein. In some embodiments, the top portion 216 of the containment vessel shell 204 may be a diametrically enlarged segment of the shell that forms a housing to support and accommodate a polar crane (not shown) for moving equipment, fuel, etc. inside the containment vessel. This will provide crane access to the very inside periphery of the containment vessel and enable placement of equipment very close to the periphery of the containment vessel 200 making the containment vessel structure compact. In one configuration, therefore, the above grade portion of the containment vessel 200 may resemble a mushroom-shaped structure. In one possible embodiment, the enlarged top portion 216 of containment vessel 200 may have an outer diameter D2 that is larger than the outer diameter D1 of the rest of the adjoining lower portion 218 of the containment vessel shell 204. In one non-limiting example, the top portion 216 may have a diameter D2 that is approximately 10 feet larger than the diameter D1 of the lower portion 218 of the shell 204. The top portion 216 of shell 204 may have a suitable height H2 selected to accommodate the polar crane with allowance for working clearances which may be less than 50% of the total height H1 of the containment vessel 200. In one non-limiting example, approximately the top ten feet of the containment vessel 200 (H2) may be formed by the enlarged diameter top portion 216 in comparison to a total height H1 of 200 feet of the containment vessel. The top portion 216 of containment vessel 200 may terminate at the upper end with flange 214 at the flanged connection to the top head 206 of the containment vessel. In one embodiment, the diametrically enlarged top portion 216 of containment vessel 200 has a diameter D2 which is smaller than the inside diameter D3 of the containment enclosure structure (CES) 300 to provide a (substantially) radial gap or secondary annulus 330 (see, e.g. FIG. 4). This provides a cushion of space or buffer region between the containment enclosure structure (CES) 300 and containment vessel top portion 216 in the advent of a projectile impact on the containment enclosure structure (CES). Furthermore, the annulus 330 further significantly creates a flow path between primary annulus 313 (between the shells of the containment enclosure structure (CES) 300 and containment vessel 200) and the head space 318 between the containment enclosure structure (CES) dome 316 and top head 206 of the containment vessel 200 for steam and/or air to be vented from the containment enclosure structure (CES) as further described herein. Accordingly, the secondary annulus 330 is in fluid communication with the primary annulus 313 and the head space 318 which in turn is in fluid communication with vent 317 which penetrates the dome 316. In one embodiment, the secondary annulus 330 has a smaller (substantially) radial width than the primary annulus 313. Referring to FIGS. 1-4, the containment enclosure structure (CES) 300 may be double-walled structure in some embodiments having sidewalls 320 formed by two (substantially) radially spaced and interconnected concentric shells 310 (inner) and 311(outer) with plain or reinforced concrete 312 installed in the annular space between them. The concentric shells 310, 311 may be made of any suitably strong material, such as for example without limitation ductile metallic plates that are readily weldable (e.g. low carbon steel). Other suitable metallic materials including various alloys may be used. In one embodiment, without limitation, the double-walled containment enclosure structure (CES) 300 may have a concrete 312 thickness of 6 feet or more which ensures adequate ability to withstand high energy projectile impacts such as that from an airliner. The containment enclosure structure (CES) 300 circumscribes the containment vessel shell 204 and is spaced (substantially) radially apart from shell 204, thereby creating primary annulus 313. Annulus 313 may be a water-filled in one embodiment to create a heat sink for receiving and dissipating heat from the containment vessel 200 in the case of a thermal energy release incident inside the containment vessel. This water-filled annular reservoir preferably extends circumferentially for a full 360 degrees in one embodiment around the perimeter of upper portions of the containment vessel shell 204 lying above the concrete foundation 301. FIG. 4 shows a cross-section of the water-filled annulus 313 without the external (substantially) radial fins 221 in this figure for clarity. In one embodiment, the annulus 313 is filled with water from the base mat 304 at the bottom end 314 to approximately the top end 315 of the concentric shells 310, 311 of the containment enclosure structure (CES) 300 to form an annular cooling water reservoir between the containment vessel shell 204 and inner shell 310 of the containment enclosure structure (CES). This annular reservoir may be coated or lined in some embodiments with a suitable corrosion resistant material such as aluminum, stainless steel, or a suitable preservative for corrosion protection. In one representative example, without limitation, the annulus 313 may be about 10 feet wide and about 100 feet high. In one embodiment, the containment enclosure structure (CES) 300 includes a steel dome 316 that is suitably thick and reinforced to harden it against crashing aircraft and other incident projectiles. The dome 316 may be removably fastened to the shells 310, 311 by a robust flanged joint 318. In one embodiment, the containment enclosure structure (CES) 300 is entirely surrounded on all exposed above grade portions by the containment enclosure structure (CES) 300, which preferably is sufficiently tall to provide protection for the containment vessel against aircraft hazard or comparable projectile to preserve the structural integrity of the water mass in the annulus 313 surrounding the containment vessel. In one embodiment, as shown, the containment enclosure structure (CES) 300 extends vertically below grade to a substantial portion of the distance to the top of the base mat 304. The containment enclosure structure (CES) 300 may further include at least one rain-protected vent 317 which is in fluid communication with the head space 318 beneath the dome 316 and water-filled annulus 313 to allow water vapor to flow, escape, and vent to atmosphere. In one embodiment, the vent 317 may be located at the center of the dome 316. In other embodiments, a plurality of vents may be provided spaced (substantially) radially around the dome 316. The vent 317 may be formed by a short section of piping in some embodiments which is covered by a rain hood of any suitable configuration that allows steam to escape from the containment enclosure structure (CES) but minimizes the ingress of water. In some possible embodiments, the head space 318 between the dome 316 and top head 206 of the containment vessel 200 may be filled with an energy absorbing material or structure to minimize the impact load on the containment enclosure structure (CES) dome 316 from a crashing (falling) projecting (e.g. airliner, etc.). In one example, a plurality of tightly-packed undulating or corrugated deformable aluminum plates may be disposed in part or all of the head space to form a crumple zone which will help absorb and dissipate the impact forces on the dome 316. Referring primarily to FIGS. 1-5 and 8-17, the buried portions of the containment vessel 200 within the concrete foundation 301 below the base mat 304 may have a plain shell 204 without external features. Portions of the containment vessel shell 204 above the base mat 304, however, may include a plurality of longitudinal external (substantially) radial ribs or fins 220 which extend axially (substantially) parallel to vertical axis VA of the containment vessel-enclosure assembly 200-300. The external longitudinal fins 220 are spaced circumferentially around the perimeter of the containment vessel shell 204 and extend (substantially) radially outwards from the containment vessel. The ribs 220 serve multiple advantageous functions including without limitation (1) to stiffen the containment vessel shell 204, (2) prevent excessive “sloshing” of water reserve in annulus 313 in the occurrence of a seismic event, and (3) significantly to act as heat transfer “fins” to dissipate heat absorbed by conduction through the shell 204 to the environment of the annulus 313 in the situation of a fluid/steam release event in the containment vessel. Accordingly, in one embodiment to maximize the heat transfer effectiveness, the longitudinal fins 220 extend vertically for substantially the entire height of the water-filled annulus 313 covering the effective heat transfer surfaces of the containment vessel 200 (i.e. portions not buried in concrete foundation) to transfer heat from the containment vessel 200 to the water reservoir, as further described herein. In one embodiment, the external longitudinal fins 220 have upper horizontal ends 220a which terminate at or proximate to the underside or bottom of the larger diameter top portion 216 of the containment vessel 200, and lower horizontal ends 220b which terminate at or proximate to the base mat 304 of the concrete foundation 301. In one embodiment, the external longitudinal fins 220 may have a height H3 which is equal to or greater than one half of a total height of the shell of the containment vessel. In one embodiment, the upper horizontal ends 220a of the longitudinal fins 220 are free ends not permanently attached (e.g. welded) to the containment vessel 200 or other structure. At least part of the lower horizontal ends 220b of the longitudinal fins 220 may abuttingly contact and rest on a horizontal circumferential rib 222 welded to the exterior surface of the containment vessel shell 204 to help support the weight of the longitudinal fins 220 and minimize stresses on the longitudinal rib-to-shell welds. Circumferential rib 222 is annular in shape and may extend a full 360 degrees completely around the circumferential of the containment vessel shell 204. In one embodiment, the circumferential rib 222 is located to rest on the base mat 304 of the concrete foundation 301 which transfers the loads of the longitudinal fins 220 to the foundation. The longitudinal fins 220 may have a lateral extent or width that projects outwards beyond the outer peripheral edge of the circumferential rib 222. Accordingly, in this embodiment, only the inner portions of the lower horizontal end 220b of each rib 220 contacts the circumferential rib 222. In other possible embodiments, the circumferential rib 222 may extend (substantially) radially outwards far enough so that substantially the entire lower horizontal end 220b of each longitudinal rib 220 rests on the circumferential rib 222. The lower horizontal ends 220b may be welded to the circumferential rib 222 in some embodiments to further strengthen and stiffen the longitudinal fins 220. The external longitudinal fins 220 may be made of steel (e.g. low carbon steel), or other suitable metallic materials including alloys which are each welded on one of the longitudinally-extending sides to the exterior of the containment vessel shell 204. The opposing longitudinally-extending side of each rib 220 lies proximate to, but is preferably not permanently affixed to the interior of the inner shell 310 of the containment enclosure structure (CES) 300 to maximize the heat transfer surface of the ribs acting as heat dissipation fins. In one embodiment, the external longitudinal fins 220 extend (substantially) radially outwards beyond the larger diameter top portion 216 of the containment vessel 200 as shown. In one representative example, without limitation, steel ribs 220 may have a thickness of about 1 inch. Other suitable thickness of ribs may be used as appropriate. Accordingly, in some embodiments, the ribs 220 have a radial width that is more than 10 times the thickness of the ribs. In one embodiment, the longitudinal fins 220 are oriented at an oblique angle Al to containment vessel shell 204 as best shown in FIGS. 2-3 and 5. This orientation forms a crumple zone extending 360 degrees around the circumference of the containment vessel 200 to better resist projectile impacts functioning in cooperation with the outer containment enclosure structure (CES) 300. Accordingly, an impact causing inward deformation of the containment enclosure structure (CES) shells 210, 211 will bend the longitudinal fins 220 which in the process will distribute the impact forces preferably without direct transfer to and rupturing of the inner containment vessel shell 204 as might possibly occur with ribs oriented 90 degrees to the containment vessel shell 204. In other possible embodiments, depending on the construction of the containment enclosure structure (CES) 300 and other factors, a perpendicular arrangement of ribs 220 to the containment vessel shell 204 may be appropriate. In one embodiment, referring to FIGS. 6-8, portions of the containment vessel shell 204 having and protected by the external (substantially) radial fins 220 against projectile impacts may extend below grade to provide protection against projectile strikes at or slightly below grade on the containment enclosure structure (CES) 300. Accordingly, the base mat 304 formed at the top of the vertically extending sidewalls 303 of the foundation 301 where the fins 220 terminate at their lower ends may be positioned a number of feet below grade to improve impact resistance of the nuclear reactor containment system. In one embodiment, the containment vessel 200 may optionally include a plurality of circumferentially spaced apart internal (substantially) radial fins 221 attached to the interior surface of the shell 204 (shown as dashed in FIGS. 2 and 3). Internal fins 221 extend (substantially) radially inwards from containment vessel shell 204 and longitudinally in a vertical direction of a suitable height. In one embodiment, the internal (substantially) radial fins 221 may have a height substantially coextensive with the height of the water-filled annulus 313 and extend from the base mat 304 to approximately the top of the shell 204. In one embodiment, without limitation, the internal fins 221 may be oriented substantially perpendicular (i.e. 90 degrees) to the containment vessel shell 204. Other suitable angles and oblique orientations may be used. The internal fins function to both increase the available heat transfer surface area and structurally reinforce the containment vessel shell against external impact (e.g. projectiles) or internal pressure increase within the containment vessel 200 in the event of a containment pressurization event (e.g. LOCA or reactor scram). In one embodiment, without limitation, the internal fins 221 may be made of steel. Referring to FIGS. 1-15, a plurality of vertical structural support columns 331 may be attached to the exterior surface of the containment vessel shell 204 to help support the diametrically larger top portion 216 of containment vessel 200 which has peripheral sides that are cantilevered (substantially) radially outwards beyond the shell 204. The support columns 331 are spaced circumferentially apart around the perimeter of containment vessel shell 204. In one embodiment, the support columns 331 may be formed of steel hollow structural members, for example without limitation C-shaped members in cross-section (i.e. structural channels), which are welded to the exterior surface of containment vessel shell 204. The two parallel legs of the channels may be vertically welded to the containment vessel shell 204 along the height of each support column 331 using either continuous or intermittent welds such as stitch welds. The support columns 331 extend vertically downwards from and may be welded at their top ends to the bottom/underside of the larger diameter top portion 216 of containment vessel housing the polar crane. The bottom ends of the support columns 331 rest on or are welded to the circumferential rib 222 which engages the base mat 304 of the concrete foundation 301 near the buried portion of the containment. The columns 331 help transfer part of the dead load or weight from the crane and the top portion 216 of the containment vessel 300 down to the foundation. In one embodiment, the hollow space inside the support columns may be filled with concrete (with or without rebar) to help stiffen and further support the dead load or weight. In other possible embodiments, other structural steel shapes including filled or unfilled box beams, I-beams, tubular, angles, etc. may be used. The longitudinal fins 220 may extend farther outwards in a (substantially) radial direction than the support columns 331 which serve a structural role rather than a heat transfer role as the ribs 220. In certain embodiments, the ribs 220 have a (substantially) radial width that is at least twice the (substantially) radial width of support columns. FIGS. 11-15 show various cross sections (both longitudinal and transverse) of containment vessel 200 with equipment shown therein. In one embodiment, the containment vessel 200 may be part of a small modular reactor (SMR) system such as SMR-160 by Holtec International. The equipment may generally include a nuclear reactor vessel 500 disposed in a wet well 504 and defining an interior space housing a nuclear fuel core inside and circulating primary coolant, and a steam generator 502 fluidly coupled to the reactor and circulating a secondary coolant which may form part of a Rankine power generation cycle. Such a system is described for example in PCT International Patent Application No. PCT/US13/66777 filed Oct. 25, 2013, which is incorporated herein by reference in its entirety. Other appurtenances and equipment may be provided to create a complete steam generation system. Auxiliary Heat Dissipation System Referring primarily now to FIGS. 2-3, 16, and 18, the containment vessel 200 may further include an auxiliary heat dissipation system 340 comprising a discrete set or array of heat dissipater ducts 610 (HDD). In one embodiment, the auxiliary heat dissipation system 340 and associated heat dissipater ducts 610 may form part of a passive reactor core cooling system described in further detail below and shown in FIGS. 22 and 23. Heat dissipater ducts 610 include a plurality of internal longitudinal ducts 341 (i.e. flow conduits) circumferentially spaced around the circumference of containment vessel shell 204. Ducts 341 extend vertically parallel to the vertical axis VA and in one embodiment are attached to the interior surface of shell 204. The ducts 341 may be made of metal such as steel and are welded to interior of the shell 204. In one possible configuration, without limitation, the ducts 341 may be comprised of vertically oriented C-shaped structural channels (in cross section) or half-sections of pipe/tube positioned so that the parallel legs of the channels or pipe/tubes are each seam welded to the shell 204 for their entire height to define a sealed vertical flow conduit. The fluid (liquid or steam phase) in the heat dissipater ducts in this embodiment therefore directly contacts the reactor containment vessel 200 to maximize heat transfer through the vessel to the water in the annular reservoir (primary annulus 313) which forms a heat sink for the reactor containment vessel 200 and the heat dissipater ducts. Other suitably shaped and configured heat dissipater ducts 341 may be provided for this type construction so long as the fluid conveyed in the ducts contacts at least a portion of the interior containment vessel shell 204 to transfer heat to the water-filled annulus 313. In other possible but less preferred acceptable embodiments, the heat dissipater ducts 341 may be formed from completely tubular walled flow conduits (e.g. full circumferential tube or pipe sections rather than half sections) which are welded to the interior containment vessel shell 204. In these type constructions, the fluid conveyed in the ducts 341 will transfer heat indirectly to the reactor containment vessel shell 204 through the wall of the ducts first, and then to the water-filled annulus 313. Any suitable number and arrangement of ducts 341 may be provided depending on the heat transfer surface area required for cooling the fluid flowing through the ducts. The ducts 341 may be uniformly or non-uniformly spaced on the interior of the containment vessel shell 204, and in some embodiments grouped clusters of ducts may be circumferentially distributed around the containment vessel. The ducts 341 may have any suitable cross-sectional dimensions depending on the flow rate of fluid carried by the ducts and heat transfer considerations. The open upper and lower ends 341a, 341b of the ducts 341 are each fluidly connected to a common upper inlet ring header 343 and lower outlet ring header 344. The annular shaped ring headers 343, 344 are vertically spaced apart and positioned at suitable elevations on the interior of the containment vessel 200 to maximize the transfer of heat between fluid flowing vertically inside ducts 341 and the shell 204 of the containment vessel in the active heat transfer zone defined by portions of the containment vessel having the external longitudinal fins 220 in the primary annulus 313. To take advantage of the primary water-filled annulus 313 for heat transfer, upper and lower ring headers 343, 344 may each respectively be located on the interior of the containment vessel shell 204 adjacent and near to the top and bottom of the annulus. In one embodiment, the ring headers 343, 344 may each be formed of half-sections of arcuately curved steel pipe as shown which are welded directly to the interior surface of containment vessel shell 204 in the manner shown. In other embodiments, the ring headers 343, 344 may be formed of complete sections of arcuately curved piping supported by and attached to the interior of the shell 204 by any suitable means. In one embodiment, the heat dissipation system 340 is fluidly connected to a source of steam that may be generated from a water mass inside the containment vessel 200 to reject radioactive material decay heat from the reactor core. The containment surface enclosed by the ducts 341 serves as the heat transfer surface to transmit the latent heat of the steam inside the ducts to the shell 204 of the containment vessel 200 for cooling via the external longitudinal fins 220 and water filled annulus 313. In operation, steam enters the inlet ring header 343 and is distributed to the open inlet ends of the ducts 341 penetrating the header. The steam enters the ducts 341 and flows downwards therein along the height of the containment vessel shell 204 interior and undergoes a phase change from steam (vapor) to liquid. The condensed steam drains down by gravity in the ducts and is collected by the lower ring header 344 from which it is returned back to the source of steam also preferably by gravity in one embodiment. It should be noted that no pumps are involved or required in the foregoing process. It will be appreciated that in certain embodiments, more than one set or array of heat dissipater ducts 610 may be provided and arranged on the inside surface of the inner containment vessel 200 within the containment space defined by the vessel. Auxiliary Air Cooling System According to another aspect of the present disclosure, a secondary or backup passive air cooling system 400 is provided to initiate air cooling by natural convection of the containment vessel 200 if, for some reason, the water inventory in the primary annulus 313 were to be depleted during a thermal reactor related event (e.g. LOCA or reactor scram). Referring to FIG. 8, the air cooling system 400 may be comprised of a plurality of vertical inlet air conduits 401 spaced circumferentially around the containment vessel 200 in the primary annulus 313. Each air conduit 401 includes an inlet 402 which penetrates the sidewalls 320 of the containment enclosure structure (CES) 300 and is open to the atmosphere outside to draw in ambient cooling air. Inlets 402 are preferably positioned near the upper end of the containment enclosure structure's sidewalls 320. The air conduits 401 extend vertically downwards inside the annulus 313 and terminate a short distance above the base mat 304 of the foundation (e.g. approximately 1 foot) to allow air to escape from the open bottom ends of the conduits. Using the air conduits 401, a natural convection cooling airflow pathway is established in cooperation with the annulus 313. In the event the cooling water inventory in the primary annulus 313 is depleted by evaporation during a thermal event, air cooling automatically initiates by natural convection as the air inside the annulus will continue to be heated by the containment vessel 200. The heated air rises in the primary annulus 313, passes through the secondary annulus 330, enters the head space 318, and exits the dome 316 of the containment enclosure structure (CES) 300 through the vent 317 (see directional flow arrows, FIG. 8). The rising heated air creates a reduction in air pressure towards the bottom of the primary annulus 313 sufficient to draw in outside ambient downwards through the air conduits 401 thereby creating a natural air circulation pattern which continues to cool the heated containment vessel 200. Advantageously, this passive air cooling system and circulation may continue for an indefinite period of time to cool the containment vessel 200. It should be noted that the primary annulus 313 acts as the ultimate heat sink for the heat generated inside the containment vessel 200. The water in this annular reservoir also acts to maintain the temperature of all crane vertical support columns 331 (described earlier) at essentially the same temperature thus ensuring the levelness of the crane rails (not shown) at all times which are mounted in the larger portion 216 of the containment vessel 200. Operation of the reactor containment system 100 as a heat exchanger will now be briefly described with initial reference to FIG. 19. This figure is a simplified diagrammatic representation of the reactor containment system 100 without all of the appurtenances and structures described herein for clarity in describing the active heat transfer and rejection processes performed by the system. In the event of a loss-of-coolant (LOCA) accident, the high energy fluid or liquid coolant (which may typically be water) spills into the containment environment formed by the containment vessel 200. The liquid flashes instantaneously into steam and the vapor mixes with the air inside the containment and migrates to the inside surface of the containment vessel 200 sidewalls or shell 204 (since the shell of the containment is cooler due the water in the annulus 313). The vapor then condenses on the vertical shell walls by losing its latent heat to the containment structure metal which in turn rejects the heat to the water in the annulus 313 through the longitudinal fins 220 and exposed portions of the shell 204 inside the annulus. The water in the annulus 313 heats up and eventually evaporates forming a vapor which rises in the annulus and leaves the containment enclosure structure (CES) 300 through the secondary annulus 330, head space 318, and finally the vent 317 to atmosphere. As the water reservoir in annulus 313 is located outside the containment vessel environment, in some embodiments the water inventory may be easily replenished using external means if available to compensate for the evaporative loss of water. However, if no replenishment water is provided or available, then the height of the water column in the annulus 313 will begin to drop. As the water level in the annulus 313 drops, the containment vessel 200 also starts to heat the air in the annulus above the water level, thereby rejecting a portion of the heat to the air which rises and is vented from the containment enclosure structure (CES) 300 through vent 317 with the water vapor. When the water level drops sufficiently such that the open bottom ends of the air conduits 401 (see, e.g. FIG. 8) become exposed above the water line, fresh outside ambient air will then be pulled in from the air conduits 401 as described above to initiate a natural convection air circulation pattern that continues cooling the containment vessel 200. In one embodiment, provisions (e.g. water inlet line) are provided through the containment enclosure structure (CES) 300 for water replenishment in the annulus 313 although this is not required to insure adequate heat dissipation. The mass of water inventory in this annular reservoir is sized such that the decay heat produced in the containment vessel 200 has declined sufficiently such that the containment is capable of rejecting all its heat through air cooling alone once the water inventory is depleted. The containment vessel 200 preferably has sufficient heat rejection capability to limit the pressure and temperature of the vapor mix inside the containment vessel (within its design limits) by rejecting the thermal energy rapidly. In the event of a station blackout, the reactor core is forced into a “scram” and the passive core cooling systems will reject the decay heat of the core in the form of steam directed to upper inlet ring header 343 of heat dissipation system 340 already described herein (see, e.g. FIGS. 16 and 18). The steam then flowing downwards through the network of internal longitudinal ducts 341 comes in contact with the containment vessel shell 204 interior surface enclosed within the heat dissipation ducts and condenses by rejecting its latent heat to the containment structure metal, which in turn rejects the heat to the water in the annulus via heat transfer assistance provide by the longitudinal fins 220. The water in the annular reservoir (primary annulus 313) heats up eventually evaporating. The containment vessel 200 rejects the heat to the annulus by sensible heating and then by a combination of evaporation and air cooling, and then further eventually by natural convection air cooling only as described herein. As mentioned above, the reactor containment system 100 is designed and configured so that air cooling alone is sufficient to reject the decay heat once the effective water inventory in annulus 313 is entirely depleted. In both these foregoing scenarios, the heat rejection can continue indefinitely until alternate means are available to bring the plant back online. Not only does the system operate indefinitely, but the operation is entirely passive without the use of any pumps or operator intervention. Passive Reactor Cooling System According to another aspect of the invention, a passive gravity-driven nuclear reactor cooling system is provided to reject the reactor's decay heat during a reactor shutdown (e.g. “scram”) without any reliance on and drawbacks of pumps and motors. In one embodiment, a passive nuclear reactor shutdown cooling system 600 may comprise a submerged bundle cooling system 602 (SBCS) including components generally shown in FIGS. 21-23. The submerged bundle cooling system 602 is preferably a closed loop pressurized flow system comprised of three major parts or sub-systems, namely (i) a submerged bundle heat exchanger 620 (SBHX), (ii) a discrete set or array of heat dissipater ducts 610 (HDD) integrally connected to the inner wall of the containment structure (described in detail above), and (iii) the steam generator 502 with superheater or reactor pressure vessel 500 as further described herein. Steam and condensate flow paths are established between these components as described below. The submerged bundle cooling system 602 is configured to utilize the secondary steam in the steam generator to extract the thermal energy generated by the fuel core in a closed loop process during a reactor shutdown that can continue indefinitely in the absence of a ready source of electric power. Steam generator 502 is more fully described in International PCT Application No. PCT/US13/38289 filed Apr. 25, 2013, which is incorporated herein by reference in its entirety. As described therein and shown in FIGS. 11, 12, and 24 of the present application, the steam generator 502 may be vertically oriented and axially elongated similarly to submerged bundle heat exchanger 620. The steam generator 502 may be comprised of a set of tubular heat exchangers arranged in a vertical stack configured to extract the reactor's decay heat from the primary coolant by gravity-driven passive flow means. The circulation flow loops of primary coolant (liquid water) and secondary coolant (liquid feedwater and steam) through the reactor vessel and steam generator during normal operation of the reactor and power plant with an available electric supply produced by the station turbine-generator (T-G) set is shown in FIG. 24 herein. The primary coolant flow between the fluidly coupled steam generator 502 and reactor vessel 500 forms a first closed flow loop for purposes of the present discussion. In one embodiment, the primary coolant flow is gravity-driven relying on the change in temperature and corresponding density of the coolant as it is heated in the reactor vessel 500 by nuclear fuel core 501, and then cooled in the steam generator 502 as heat is transferred to the secondary coolant loop of the Rankine cycle which drives the turbine-generator set. The pressure head created by the changing different densities of the primary coolant (i.e. hot—lower density and cold—higher density) induces flow or circulation through the reactor vessel-steam generating vessel system as shown by the directional flow arrows. In general with respect to the first closed flow loop, the primary coolant is heated by the nuclear fuel core 501 and flows upwards in riser column 224. The primary coolant from the reactor vessel 500 then flows through the primary coolant fluid coupling 273 between the reactor vessel 500 and steam generator 502 and enters the steam generator. The primary coolant flows upward in the centrally located riser pipe 337 to a pressurizer 380 at the top of the steam generator. The primary coolant reverses direction and flows down through the tube side of the steam generator 502 and returns to the reactor vessel 500 through the fluid coupling 273 where it enters an annular downcomer 222 to complete the primary coolant flow loop. The steam generator 502 may include three vertically stacked heat transfer sections—from bottom up a preheater section 351, steam generator section 352, and superheater section 350 (see, e.g. FIGS. 11, 12, and 24). Secondary coolant flows on the shellside of the steam generator 502 vessel. Secondary coolant in the form of liquid feedwater from the turbine-generator (T-G) set of the Rankine cycle enters the steam generator at the bottom in the preheater section 351 and flows upwards through the steam generator section 352 being converted to steam. The steam flows upwards into the superheater section 350 and reaches superheat conditions. From there, the superheated steam is extracted and flows to the T-G set to produce electric power. Referring now to FIGS. 21-23, the submerged bundle heat exchanger 620 includes a pressure vessel 621 defining a longitudinal axis LA and having a hollow cylindrical shell 625 defining an internal cavity 626 and opposing top and bottom heads 622, 623 on opposite ends 624, 627 of the shell. The heads 622, 623 may be any suitable type and configuration, including flat, spherical, hemi-spherical, etc. Internal cavity 626 extends completely between the top and bottom heads 622, 623. The pressure vessel 621 may be axially elongated in shape and have a vertical orientation in one embodiment as shown to promote gravity flow. Preferably, the heat exchanger 620 is mounted and disposed inside the inner vessel 202 of the containment structure 200 above the reactor vessel 500 and in relatively close proximity to the steam generator 502. The close coupling of the heat exchanger 620 and steam generator 502 minimizes steam and condensate piping run lengths (see also FIGS. 11 and 13) and conserves horizontal space thereby minimizing the diameter needed for the containment vessel 200 to house the reactor vessel 500, steam generator 502, and heat exchanger. Any suitable structural base 650 may be provided to mount and support the heat exchanger 620 from the inner containment vessel 200 preferably from a structural steel and/or concrete platform or floor in the vessel to adequately support the weight of the heat exchanger. A reserve or inventory (i.e. volume) of cooling water W (liquid) is held in the heat exchanger pressure vessel 621 which acts as a heat sink for cooling the secondary coolant during reactor shutdown event, as further described herein. Accordingly, the cooling water W serves as a heat sink of a third coolant which has an initial temperature which is less than the initial temperature of the secondary coolant during a shutdown. The submerged bundle heat exchanger 620 may be a relatively a large cylindrical pressure vessel 621 housing a comparatively smaller heat exchanger tube bundle 630 disposed inside as shown in FIG. 21. In one example, without limitation, pressure vessel 621 may have an outer diameter of approximately 10 feet and a height of approximately 20 feet whereas the tube bundle 630 housed therein may be circular in transverse shape having a diameter of approximately 4 feet and a height less than the height of the pressure vessel. Other suitable dimensions may be provided. Accordingly, the tube bundle 630 in this embodiment does not substantially fill the entire cavity 626 of the pressure vessel 621. Preferably, the tube bundle 630 may be positioned closer to the bottom end 627 and head 623 than the top end 624 and head 622 (see, e.g. FIG. 21). This positioning helps ensure that the tube bundle 630 remains substantially submerged for a majority or preferably all of its height in the inventory of liquid water W stored in the pressure vessel 621. Accordingly, in some embodiments the tube bundle 630 is completely surrounded by and immersed in the liquid condensate on all sides and parts. The tube bundle 630 may be elevated and spaced apart above the bottom head 623 of the heat exchanger pressure vessel 625 to provide a sufficient depth of water beneath the bundle to permit flow beneath the tube bundle on the shellside of the vessel. Any suitable arrangement of structural supports and brackets inside the pressure vessel 625 to fixedly support the tube bundle assembly 630 may be used. Pressure vessel 621 may be made of any suitable metal capable of withstanding the steam and operating pressures anticipated from the steam generator 502. In some embodiments, pressure vessel 621 may be formed of a corrosion resistant material such as without limitation stainless steel. Other corrosion resistant metallic materials may be used. The tube bundle 630 is disposed in cavity 626 of the pressure vessel 621. In one non-limiting configuration, tube bundle 630 assembly may include an inlet flow plenum 631 defining a top tube sheet 632, an outlet flow plenum 633 defining a bottom tube sheet 634 and spaced apart from the top tube sheet, and a plurality of tubes 635 extending between and fluidly coupled to the top and bottom tube sheets. The tube sheets 632, 634 each include a plurality of flow openings 636, 637 respectively which are in fluid communication with the inlet and outlet flow plenums 631, 633 and tubes 635. In operation and description of the flow path, flow enters the inlet flow plenum 631 and through openings 636 into one end of the tubes 635, exits the opposite end of the tubes 635 through openings 637 into outlet plenum 633, and leaves the outlet plenum. In one embodiment, the tubes 635 of tube bundle 630 may be axially elongated and vertically oriented as shown. Other orientations are possible however such as horizontal, and angled between horizontal and vertical. The tubes 635 may have any suitable shape including without limitation straight, curvilinear such as helically coiled (see, e.g. FIG. 21) or another curvilinear configuration, or other appropriate shape. In one preferred embodiment, the tubes may have a curvilinear shape which maximizes available heat transfer surface area without requiring as much height as straight tubes having the same surface area. Any suitable diameter tubes and tube arrangement/pattern may be used. For example, single or multiple rows of tubes 635 may be provided; the number being dependent at least in part on the heat transfer requirements for the heat exchanger 620. In one embodiment, the tube bundle 630 may have a generally circular shape in transverse cross section. Tubes 635 may be formed of any suitable preferably corrosion resistant metal having conductive heat transfer properties suitable for a given application. Some non-limiting examples of the tube materials that may be used include stainless steel, aluminum, titanium, corrosion resistant steel alloys, Inconel®, Monel®, or others. The inlet and outlet flow plenums 631 and 633 each comprise a substantially hollow outer body of any suitable shape forming a pressure boundary and an open interior plenum. The tube sheets 632, 634 may have any suitable thickness and shape in plane including planar and arcuate (e.g. if the plenums are shapes as pipe sections) and in top plan view (e.g. circular for a round cross-sectional tube bundle). The tube sheets and plenums may be formed of any suitable corrosion resistant metal or metal alloy, some examples of which are mentioned above with respect to possible materials for tubes 635. The submerged bundle heat exchanger 620 may variously be fluidly interconnected with and coupled to the steam generator 502, rector vessel 500, and heat dissipater ducts 610 by suitable steam and condensate piping 603 shown in FIGS. 22 and 23. The piping 603 is configured to establish the flow paths shown in these figures. Any suitable type of piping and materials may be used for piping 603 which may depend in part on whether the piping run is for conveying condensate or steam and their associated service temperatures and pressures anticipated. In some embodiments, for example without limitation, the piping preferably may be made of a corrosion resistant metal such as stainless steel or steel alloy. It is well within the ambit of those skilled in the art to select and design appropriate piping and related appurtenances such as valving. Notably, no pumps are involved to establish the flow paths shown in FIGS. 22 and 23 which are gravity driven. Operation of the reactor cooling system 600 will now be briefly described. During the postulated reactor shutdown event such as a station black-out or similar event wherein power generation from the turbo-generator ceases and the normal non-safety active systems are unavailable, the main steam and main feedwater isolation valves (not shown) are first closed to isolate the steam generator 502 from the extra-containment power generation portion of Rankine cycle. Accordingly, the isolation valves shut off steam flow from the steam generator 502 to the turbine-generator (T-G) set and feedwater flow back to the steam generator returned from the T-G set in a well-known manner to those skilled in the art without further elaboration. Excess steam may first be dumped to the atmosphere before closing the main isolation valves. Closing the main isolation valves activates the reactor core cooling system 600. Two potential operating scenarios or methods for employing the cooling system 600 are disclosed and described in further detail below which passively (i.e. without electric power) continue cooling the reactor in the event of a shutdown to remove decay heat using the submerged bundle cooling system 602. In a first operating scenario or method for cooling the reactor shown in FIG. 22, the steam produced in the steam generator 502 on the shellside in the upper half of the steam generator vessel (by residual decay heat generated from the now shut down reactor) is extracted and routed to the submerged bundle heat exchanger 620 where it condenses inside the tubes 635 of the submerged bundle heat exchanger 620 (see also FIG. 21). The condensing steam gives up its latent heat to the volume or inventory of water W (the third coolant) stored in the shellside of the submerged bundle heat exchanger pressure vessel 621 surrounding the tube bundle 630. In one embodiment, the tube bundle 630 may be completely submerged in the inventory of water W inside the heat exchanger 620 so that the water provides the cooling medium on the outside of the tubes 635 for condensing the steam. In one embodiment, the tube bundle 630 preferably may be positioned near the longitudinal axis LA coinciding with the axial centerline of the submerged bundle heat exchanger 620 to evenly surround the tube bundle with water W on all sides to promote uniform cooling of all tubes 635 in bundle. Other mounting positions of the tube bundle however are possible. The inflow of steam and outflow of collected condensate may be controlled and maintained passively by appropriate design of the valving, piping, or other flow control devices (e.g. orifices, etc.) that do not rely on electric or another power source for operation. On the tube side of the heat exchanger tube bundle 630, steam extracted from the steam generator 502 may enter the heat exchanger pressure vessel 621 at any convenient location. In one embodiment, the steam inlet piping 603 may penetrate laterally through the pressure vessel shell 625 and piping may extend inside the heat exchanger pressure vessel 621 to the inlet plenum 631 of tube bundle 630 to which it is fluidly coupled. Other steam inlet locations may be used such as without limitation through the top head 622. The condensate collected in the lower plenum 633 of the tube bundle 630 is then returned to the shellside of the steam generator 502 via piping 603, purely by natural gravity flow. The condensate outlet piping 503 may be located in the general vicinity towards or near the bottom 627 of the heat exchanger pressure vessel 621 and is reintroduced back into the steam generator 502 at an injection point (e.g. preheater 351 section) lower than the extraction point of steam from the steam generator (e.g. superheater section 350) which is supplied to the submerged bundle heat exchanger 620. A second closed flow loop is established between the steam generator 502 and tube side of the submerged bundle heat exchanger 620 (i.e. tube bundle 630). Appropriate piping may be routed inside the pressure vessel 621 between the lower plenum 633 and shell 625 of the vessel which is then coupled to the condensate outlet piping 503 connected to the steam generator 503. With continuing reference to the first operating scenario or method shown FIG. 22, the inventory of water W outside the tubes 635 in the shellside of the submerged bundle heat exchanger pressure vessel 621(which is fluidly isolated and separated from condensate on the tube side of the tube bundle 630) is heated by condensing steam inside the tube bundle which transfers it heat to the water. The water W acts as a heat sink for cooling the secondary coolant during reactor shutdown event. Accordingly, the water W serves as a third coolant which has an initial temperature that is less than the initial temperature of the secondary coolant during a shutdown. The water W gradually heats up during the reactor shutdown process. After a period of time, the water W reaches the boiling point temperature at which a portion of the water inventory is converted to steam. The steam accumulates in a steam space formed above the water line L in the pressure vessel 621 beneath the top head 622. To cool the inventory of water W (third coolant) which provides the cooling fluid for condensing the secondary coolant steam inside the tube bundle 630, the accumulated steam on the shellside is extracted and routed via suitable piping 603 to the heat dissipater ducts 610 of the auxiliary heat dissipation system 340 described in detail above. The steam flows through the heat dissipater ducts 610 and is condensed in the manner already described. Specifically, the water in the annular reservoir (primary annulus 313) as a temperature lower than the temperature of the third coolant steam to form a heat sink for condensing the third coolant steam which transfers heat to the reservoir. The condensate is then returned to the submerged bundle heat exchanger 620 via suitable piping 603 and enters the shellside of the pressure vessel 621 where it is reintroduced into the inventory of water W. This cooling system helps to substantially maintain the water level keeping the tube bundle 630 submerged in water W beneath the water line L. This system further forms a third closed flow loop of steam and condensate using the heat dissipater ducts 610 to condense the steam which is distinct and isolated from the second closed flow loop formed on the tube side of the submerged bundle heat exchanger 620 and the steam generator 502. In summary, the first and second closed flow loops described herein function to cool the primary coolant and secondary coolant, respectively. The third closed flow loop cools the cooling fluid of the submerged bundle heat exchanger 620 (i.e. heat sink of water formed by inventory of water W) which indirectly contributes to cooling the secondary coolant vis-à-vis the tube bundle 630. In the alternative second operating scenario or method for cooling the reactor shown in FIG. 23, the primary coolant in the reactor vessel 500 is directly cooled by the submerged bundle heat exchanger 620 rather than using the steam continuing to be produced in the steam generator 502 by the reactor decay heat. In this process arrangement, once the steam and feedwater isolation valves are closed, the hot primary coolant from the riser column 224 of the reactor pressure vessel (“hot leg”) is routed via piping 603 directly to the tubeside of tube bundle 630 in the submerged bundle heat exchanger 620 (see FIGS. 23 and 24). The primary coolant will cool by rejecting its heat to the shellside water W in the submerged bundle heat exchanger 620 in a very much similar manner shown in FIG. 22 and described above while flowing downwards inside the tubes 635. A difference being that the primary coolant always remains substantially in liquid state during this entire cooling process and also when circulating through the reactor vessel 500. This cooling creates a natural circulation flow due to the buoyancy head created by the density difference between the hot primary coolant at the inlet to the submerged bundle heat exchanger 620 and the cold primary coolant at the outlet of the heat exchanger. The cooler primary coolant is routed via suitable piping 603 and re-introduced back into the annular downcomer 222 region of the reactor vessel 500 (“cold leg”). The submerged bundle heat exchanger 620 higher elevation with respect to the reactor vessel 500 and the size of the piping 603 that routes the primary coolant to the heat exchanger may be designed to ensure that there is adequate natural circulation flow to reject the heat from the core to the shellside water W in the heat exchanger. In both the first and second methods for cooling the reactor described above, the quantity of water W in cavity 626 of the submerged bundle heat exchanger 620 is preferably sufficient to remove the decay heat from the reactor core (via the primary coolant) through sensible heating of shellside water in the early phase of the postulated reactor shutdown event when the decay heat generation is at its highest. The may be accomplished in part by adequately sizing the storage volume and size of the submerged bundle heat exchanger pressure vessel 621. The operational interaction of the reactor cooling system 600 and air cooling system 400 of the containment structure will be briefly described. As described above, the remainder of the heat not used in condensing steam inside the tube bundle 630 of the heat exchanger 620 leads to the production of steam in the shellside of the heat exchanger by heating the inventory of water W. This shellside steam is routed to the heat dissipater ducts 610 where the steam condenses by rejecting its latent heat to the containment structure (e.g. inner containment vessel 200). The containment vessel 200 rejects the heat to the water in the annulus 313 between the containment structure and the containment enclosure structure 300 (and eventually to the ultimate heat sink or atmosphere) of the passive reactor containment protection system described herein. The condensed steam from the heat dissipater ducts 610 then drains back to a collection manifold (lower outlet ring header 344 shown in FIGS. 16 and 18) which in turn routes the condensate back to the submerged bundle heat exchanger 620 purely by gravity. As the cooling water inventory in the annulus 313 between the inner containment vessel 200 and outer containment enclosure structure 300 evaporates, the exposed inner containment vessel 200 will heat reject heat to the air now occupying the annulus 313 by natural convection. A fresh supply of air is provided by the inlet air conduits 401 (through suction) spaced circumferentially around the containment vessel 200 in the primary annulus 313 (see, e.g. FIG. 16 and foregoing description). Once all the water in the annular 313 has evaporated, the containment vessel 200 will continue to reject heat by air cooling alone. Air cooling after a prolonged period of water cooling (which removes a significant portion of reactor decay heat) is sufficient to remove all the decay heat. Since the submerged bundle cooling system 602 is a closed loop natural flow system, the cooling process can continue indefinitely. It will be appreciated that variations and combinations of the foregoing two methods may be used to passively cool the reactor during a powerless reactor shutdown event. While the foregoing description and drawings represent some example systems, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope and range of equivalents of the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, sizes, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. In addition, numerous variations in the methods/processes described herein may be made. One skilled in the art will further appreciate that the invention may be used with many modifications of structure, arrangement, proportions, sizes, materials, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims and equivalents thereof, and not limited to the foregoing description or embodiments. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.
abstract
Techniques for forming a target and for producing extreme ultraviolet light include releasing an initial target material toward a target location, the target material including a material that emits extreme ultraviolet (EUV) light when converted to plasma; directing a first amplified light beam toward the initial target material, the first amplified light beam having an energy sufficient to form a collection of pieces of target material from the initial target material, each of the pieces being smaller than the initial target material and being spatially distributed throughout a hemisphere shaped volume; and directing a second amplified light beam toward the collection of pieces to convert the pieces of target material to plasma that emits EUV light.
abstract
Apparatus and methods for compensating for the movement of a substrate in a lithographic apparatus during a pulse of radiation include providing a pivotable mirror configured to move a patterned radiation beam incident on the substrate in substantial synchronism with the substrate.
048624900
abstract
A vacuum window including a support substrate provided with a window aperture, and a membrane attached to a front surface of the substrate. The membrane has a relatively thick perimeter portion attached to the support substrate, and has a window portion aligned with the window aperture. The window portion of the membrane includes a number of relatively thin pane sections separated by relatively thick, structural rib sections. The membrane material is preferably boron nitride, boron carbide, or silicon carbide.
043938990
summary
BACKGROUND OF THE INVENTION This invention relates to apparatus for plugging cylindrical holes provided at an inner wall of a cylindrical container and, more particularly, apparatus for plugging openings of main steam pipes of a nuclear reactor to easily inspect or maintain safety valves, relief valves, and main steam insulation valves, at the time of shutting-down the reactor. Generally, at a time of a periodical inspection of a nuclear reactor, the reactor is shut down and the inlet openings of the main steam pipes must be plugged. A reactor pressure vessel is then filled with water until the reactor core is entirely submerged under the water to reduce leakage of radioactive rays from the reactor core. Thereafter, safety valves, relief valves and main steam insulation valves disposed in the steam pipes are overhauled and periodically inspected. A conventional apparatus for plugging the inlet opening of the steam pipe will firstly be described hereinbelow in conjunction with FIG. 1. FIG. 1, reference numeral 1 designates a main steam pipe provided with an inlet opening. Usually four steam pipes are provided. A cylindrical member 2, which has an outer diameter somewhat smaller than the inner diameter of the steam pipe 1, is inserted into the steam pipe 1 opened into a reactor pressure vessel 9. A cylindrical hollow elastic member 3 is disposed in a space between the outer surface of the support member 2 and the inner surface of the steam pipe 1 so that the inlet opening of the steam pipe 1 is plugged at a time when compressed air is admitted into the hollow elastic member 3 through an air feed pipe 4 connected therewith. Another cylindrical hollow elastic member 5 is disposed between the outer surface of the support member 2 and the inner surface of the steam pipe 1 at the inner end of the support member 2 and is filled with water fed through a pipe 5A thereby to increase the sealing effect of the plugging apparatus. An O-ring 6 is disposed at the outer end of the support member 2 to further increase the sealing effect of the plugging apparatus due to hydraulic pressure caused by the water filled in the reactor pressure vessel 9. An annular plate 7 is water-tightly welded to the inside wall of the cylindrical support member 2, and to the annular plate 7 is secured a pipe 8 through which the support member 2 is operated or controlled at the upper portion of the reactor core. In a case where it is desired to remove the plugging apparatus from the steam pipe 1, water is supplied into an inner portion 2A of the support member 2 through the pipe 8 to maintain water pressure balance between the steam pipe 1 and the reactor pressure vessel 9. Between the cylindrical members or rings 5, 3 or 6 are disposed detecting means, not shown, for detecting leakage water, thereby to maintain or inspect the sealing condition therebetween. According to the conventional plugging apparatus described above, it is necessary to independently insert four plugging apparatus into four steam pipes 1 and it takes much time and labor for attaching or removing the plugging apparatus. Moreover, in a case where an operator checks air-tight capability of the safety valves, relief valves, and main steam insulation valves after the inspection or maintenance thereof, although it is required to apply air pressure between the safety valve and the inserted plugging apparatus, the apparatus will be blown into the reactor pressure vessel by counter pressure of the applied air for the reason that the conventional plugging apparatus has no means for withstanding the counter pressure. SUMMARY OF THE INVENTION Accordingly, an object of this invention is to obviate defects of the conventional apparatus described above and to provide plugging apparatus for plugging simultaneously cylindrical holes provided at the inner side wall of a cylindrical container. Another object of this invention is to provide plugging apparatus comprising a plug support ring which firmly supports the plugs inserted into the cylindrical holes against counter pressure caused by air pressure applied to the inside of the holes. According to this invention, there is provided apparatus for plugging a plurality of cylindrical holes provided at an inner peripheral wall of a cylindrical container. The apparatus comprises a plurality of plugs to be inserted into the holes for plugging the same, a support ring assembly having an outer diameter smaller than an inner diameter of the container, and a beam assembly for operating the support ring assembly and the plugs. The support ring assembly supports the plugs on an inner side of the container after the plugs have been inserted into the cylindrical holes, respectively.
abstract
A method for discharging a sample, the method includes: determining whether to discharge a negatively charged area of a sample or to discharge a positively charged area of the sample; and injecting gas, via an electrode and gas supply component, or setting a first electrode to a first voltage and set the electrode and gas supply component to a second voltage, in response to the determination. A system including: a first electrode adapted to be set to at least a first potential; an electrode and gas supply component, adapted to be set to at least a second potential and to selectively supply gas to a vicinity of the sample; wherein at least one out of the first electrode and the electrode and gas supply component are positioned close to the sample.
claims
1. A process for creating isotopes using laser beams, comprising steps of:/1/ converting a target, comprising a fuel, to a plasma state, and/2/ generating particles with a set of laser beams and bombarding the target in the plasma state with the particles wherein:the particle generation is synchronized with the target conversion; andthe bombarding produces nuclear reactions between the fuel and the particles and creates said isotopes. 2. The process as claimed in claim 1, wherein the step /2/ is repeated several times on the same target. 3. The process as claimed in claim 1, wherein the step /2/ comprises irradiating a second solid, gaseous or liquid target with the set of laser beams. 4. The process as claimed in claim 1, wherein the set of laser beams used to bombard the target is a first set of laser beams, the target being converted to the plasma state by using a second set of laser beams. 5. The process as claimed in claim 1, wherein the target comprises a hollow depression, and, at step /2/, the particles are directed into the hollow depression. 6. The process as claimed in claim 1, wherein the target is surrounded by an envelope comprising an opening, and, at step /2/, the particles bombarding the target are directed through the opening to the target. 7. The process as claimed in claim 1, wherein the nuclear reactions include nuclear chain reactions. 8. A process for creating stable isotopes, radioisotopes, or nuclear isomers using laser beams, comprising steps of:/1/ converting a target, comprising a fuel, to a plasma state, and/2/ generating particles with a set of laser beams and bombarding the target in the plasma state with the particles, wherein:the particle generation is synchronized with the target conversion; andthe bombarding produces nuclear reactions between the fuel and the particles and creates said stable isotopes, radioisotopes, or nuclear isomers.
claims
1. A method for generating and maintaining a magnetic field with a field reversed configuration (FRC) comprisinggenerating a magnetic field with a magnetic system coupled to a confinement chamber, first and second diametrically opposed FRC formation sections coupled to the confinement chamber, and first and second divertors coupled to the first and second formation sections, the magnetic system including first and second mirror plugs positioned between the first and second formation sections and the first and second divertors and two or more saddle coils coupled to the confinement chamber,gettering the confinement chamber and the first and second divertors with a layer of gettering material from a gettering system coupled to the confinement chamber and the first and second divertors,generating an FRC in each of the first and second formation sections and translating each FRC toward a midplane of the confinement chamber where the FRCs merge into a merged FRC, the first and second formation sections comprising a modularized formation system,injecting neutral atom beams into the merged FRC from a plurality of neutral atom beam injectors coupled to the confinement chamber and oriented normal to the axis of the confinement chamber,injecting plasma into the merged FRC from first and second axial plasma guns operably coupled to the first and second divertors, the first and second formation sections and the confinement chamber, andelectrically biasing open flux surfaces of the merged FRC with one or more biasing electrodes being positioned within one or more of the confinement chamber, the first and second formation sections, and the first and second divertors. 2. The method of claim 1 further comprising confining particles in the merged FRC for a period of time that is greater by at least a factor of two (2) deviations than the particle confinement time of an FRC having substantially the same radius of a magnetic field null (R) and particle confinement scaling that substantially depends on the ratio R2/ρi, where ρi is an ion lamor radius evaluated in an externally applied field. 3. The method of claim 1 wherein the magnetic system includes a plurality of quasi-dc coils axially spaced in positions along the confinement chamber, the first and second formation sections, and the first and second divertors. 4. The method of claim 3 wherein the magnetic system further comprises a first set of mirror coils positioned between the ends of the confinement chamber and the first and second formation sections. 5. The method of claim 4 wherein the mirror plug comprises a second set of mirror coils between each of the first and second formation sections and the first and second divertors. 6. The method of claim 5 wherein the mirror plug further comprises a set of mirror plug coils wrapped around a constriction in the passageway between each of the first and second formation sections and the first and second divertors. 7. The method of claim 1 wherein the mirror plug coils are compact pulsed mirror coils. 8. The method of claim 1 wherein the first and second formation sections comprises an elongate tube. 9. The method of claim 8 wherein the formation systems are pulsed power formation systems. 10. The method of claim 8 wherein the step of forming and translating the FRCs includes energizing a set of coils of individual ones of a plurality of strap assemblies wrapped around the elongate tube of the first and second formation sections, wherein the formation systems comprise a plurality of power and control units coupled to individual ones of the plurality of strap assemblies. 11. The method of claim 10 wherein individual ones of the plurality of power and control units comprising a trigger and control system. 12. The method of claim 11 wherein the trigger and control systems of the individual ones of the plurality of power and control units being synchronizable to enable static FRC formation wherein the FRC is formed and then injected or dynamic FRC formation wherein the FRC is formed and translated simultaneously. 13. The method of claim 1 wherein the plurality of neutral atom beam injectors comprises one or more RF plasma source neutral atom beam injectors and one or more arc source neutral atom beam injectors. 14. The method of claim 1 wherein the gettering system comprises one or more of a Titanium deposition system and a Lithium deposition system that coat the plasma facing surfaces of the confine chamber and the first and second divertors. 15. The method of claim 1 wherein biasing electrodes includes one or more of one or more point electrodes positioned within the containment chamber to contact open field lines, a set of annular electrodes between the confinement chamber and the first and second formation sections to charge far-edge flux layers in an azimuthally symmetric fashion, a plurality of concentric stacked electrodes positioned in the first and second divertors to charge multiple concentric flux layers, and anodes of the plasma guns to intercept open flux. 16. A method for generating and maintaining a magnetic field with a field reversed configuration (FRC) comprisinggenerating magnetic field with a magnetic system coupled to a confinement chamber, and second diametrically opposed FRC formation sections coupled to the confinement chamber, and first and second divertors coupled to the first and second formation sections,generating an FRC in each of the first and second formation sections and translating each FRC toward a midplane of the confinement chamber where the FRCs merge into a merged FRC,injecting neutral atom beams into the merged FRC from a plurality of neutral atom beam injectors coupled to the confinement chamber and oriented normal to the axis of the confinement chamber, andinjecting plasma into the merged FRC from first and second axial plasma guns operably coupled to the first and second divertors, the first and second formation sections and the confinement chamber. 17. The method of claim 16 further comprising confining particles in the merged FRC for a period of time that is greater by at least a factor of two (2) deviations than the particle confinement time of an FRC having substantially the same radius of a magnetic field null (R) and particle confinement scaling that substantially depends on the ratio R2/pi, where pi is an ion lamor radius evaluated in an externally applied field. 18. The method of claim 16 wherein the magnetic system includes a plurality of quasi-dc coils axially spaced in positions along the confinement chamber, the first and second formation sections, and the first and second divertors. 19. The method of claim 18 wherein the magnetic system further comprises a first set of mirror coils positioned between the ends of the confinement chamber and the first and second formation sections. 20. The method of claim 19 wherein the mirror plug comprises a second set of mirror coils between each of the first and second formation sections and the first and second divertors. 21. The method of claim 20 wherein the mirror plug further comprises a set of mirror plug coils wrapped around a constriction in the passageway between each of the first and second formation sections and the first and second divertors. 22. The method of claim 21 wherein the mirror plug coils are compact pulsed mirror coils. 23. The method of claim 22 further comprising injecting plasma into the merged FRC from first and second axial plasma guns operably coupled to the first and second divertors, the first and second formation sections and the confinement chamber. 24. The method of claim 22 further comprising gettering the confinement chamber and the first and second divertors with a layer of gettering material from a gettering system coupled to the confinement chamber and the first and second divertors. 25. The method of claim 22 further comprising electrically biasing open flux surfaces of the merged FRC with one or more biasing electrodes being positioned within one or more of the confinement chamber, the first and second formation sections, and the first and second divertors. 26. The method of claim 22 the magnetic system further comprising two or more saddle coils coupled to the confinement chamber. 27. The method of claim 22 further comprising injecting ion pellets into the merged FRC from an ion pellet injector coupled to the confinement chamber. 28. The method of claim 22 wherein the formation section comprises modularized formation systems for generating an FRC and translating it toward a midplane of the confinement chamber.
summary
abstract
A method for producing a multilayer coating (17) for reflecting radiation in the soft X-ray or EUV wavelength range on an optical element (8, 9) operated at an operating temperature (TOP) of 30° C. or more, including: determining an optical design for the multilayer coating (17) which defines an optical desired layer thickness (nOP dOP) of the layers (17.1, 17.2) of the multilayer coating (17) at the operating temperature (TOP), and applying the layers (17.1, 17.2) of the multilayer coating (17) with an optical actual layer thickness (nB dB) chosen such that a layer thickness change(nOP dOP−nB dB) caused by thermal expansion of the layers (17.1, 17.2) between the coating temperature (TB) and the operating temperature (TOP) is compensated for. Also provided are an associated optical element (8, 9) and a projection exposure apparatus having at least one such optical element (8, 9).
062051962
claims
1. A boiling water type nuclear reactor core in which a plurality of fuel assemblies, each enclosed in a channel box, are loaded and a plurality of control rods, each having control blades with a neutron absorber, are arranged between said channel boxes comprising: square bundle regions, each of which is formed by a plurality of fuel assemblies; short blade control rods, each of which has a latitudinal control rod blade length of about one half of the width of said square bundle region and is arranged between said channel boxes in the center of each of said square bundle regions; and long blade control rods, each of which has a latitudinal control rod blade length of about twice as long as that of said short blade control rods and is arranged between said channel boxes on a diagonal line of each of said square bundle regions. square bundle regions, each of which is formed by a plurality of fuel assemblies; axially movable short blade control rods, each of which has a latitudinal control rod blade length of about one half of the width of one of said square bundle regions and is arranged in the center of each of said square bundle regions; and axially movable long blade control rods, each of which has a latitudinal control rod blade length substantially the same as the width of said square bundle region and is arranged between said channel boxes on a diagonal line of each of said square bundle regions. square bundle regions, each of which is formed by a plurality of fuel assemblies; axially movable short blade control rods, each of which has a latitudinal control rod blade length of about one half of the width of one of said square bundle regions and is arranged in the center of each of said square bundle regions; and axially movable long blade control rods, each of which has a latitudinal control rod blade length substantially the same as the width of one of said square bundle regions and is arranged at one of two diagonal corners of each of said square bundle regions. 2. A boiling water type nuclear reactor core according to claim 1, wherein said long blade control rods are arranged between channel boxes on the diagonal line of each square bundle region formed of 16 fuel assemblies each having a fuel rod lattice structure of 8.times.8, 9.times.9 or 10.times.10, each short blade control rod is arranged in the center of said square bundle region, the blade length of said long blade control rods is about 4 times as long as the width of said fuel assembly, and the blade length of said short blade control rods is about twice as long as the width of the fuel assemblies. 3. A boiling water type nuclear reactor core according to claim 1, wherein each of said fuel assemblies constituting said square bundle region is provided with a water rod, said water rod has therein an ascending flow path and a descending flow path, said flow paths are connected to an inflow hole and an outflow hole of said water rod, respectively, and said inflow hole is positioned at a position lower than said outflow hole. 4. A boiling water type nuclear reactor core according to claim 1, wherein as neutron absorber arranged in each of said control rod blades, a material which becomes higher in control rod worth is used in portion facing a central side portion of said fuel assembly. 5. A boiling water type nuclear reactor core in which a plurality of fuel assemblies enclosed in respective channel boxes are loaded and a plurality of control rods, each having control blades, are arranged between said fuel assemblies, comprising: 6. A boiling water type nuclear reactor core in which a plurality of fuel assemblies are loaded and a plurality of control rods, each having control blades, are arranged between said fuel assemblies, comprising: 7. A boiling water type nuclear reactor core according to claim 6, wherein each of said square bundle regions is formed of four fuel assemblies, and the latitudinal blade length of each of said long blade control rods is about twice as long as the width of one of said fuel assemblies. 8. A boiling water type nuclear reactor core according to claim 6, wherein said short blade control rods each have a neutron absorber used therein, which is high in reactivity effect, whereby control rod worth is raised. 9. A boiling water type nuclear reactor core according to claim 8, wherein said short blade control rods each have neutron absorber of a higher enrichment in an upper region thereof than in the other region thereof. 10. A boiling water type nuclear reactor core according to claim 6, wherein said fuel assemblies are enclosed in respective channel boxes, and each said long blade control rod is arranged between channel boxes on the diagonal line of a square bundle region formed of four fuel assemblies, each said fuel assembly having a fuel rod lattice structure of 8.times.8, 9.times.9 or 10.times.10. 11. A boiling water type nuclear reactor core according to claim 6, wherein each of said fuel assemblies constituting a square bundle region has a water rod arranged therein, said water rod having a cross-sectional area corresponding to a cross-sectional area of several fuel rods. 12. A boiling water type nuclear reactor core according to claim 6, wherein a hydraulic driving mechanism is provided for hydraulically driving said long blade control rods.
claims
1. A fuel channel assembly for use in a pressurized fuel-channel-type nuclear reactor of the type adapted to be refueled on-line by the insertion and removal of fuel bundles into and from a plurality of fuel channel assemblies, each of said fuel channel assemblies comprising an elongated pressure tube and a plurality of fuel bundles longitudinally disposed in said pressure tube in end-to-end relation, each of said fuel bundles comprising a plurality of elongated fuel elements retained in parallel spaced relation uniformly about a longitudinal axis between transversely disposed end-plates, said end plates having apertures there through to permit coolant flow through said fuel channels in contact with said fuel elements, the fuel channel assembly further comprising at least one fuel bundle pair assembly, said fuel bundle pair assembly comprising a pair of fuel bundles in end-to-end relation and interconnecting means for interconnecting the adjacent facing end-plates of said pair of fuel bundles, said adjacent facing end-plates of said pair of fuel bundles being interconnected by said interconnecting means for maintaining said fuel elements in a predetermined position of relative rotational alignment about said longitudinal axis and preventing axial separation of said pair of fuel bundles in the pressure tube, the non-facing end-plates at opposite ends of said fuel bundle pair assembly permitting said fuel bundle pair assembly to be axially separable from adjacent bundles in the pressure tube to permit independent loading or unloading of said fuel bundle pair assembly. 2. The fuel channel assembly of claim 1 wherein the means for interconnecting comprises at least one retaining member fixed to one of said facing end-plates and closely engaging the other of said end-plates. claim 1 3. The fuel channel assembly of claim 2 wherein each end-plate comprises inner, intermediate and outer concentric ring web members, said inner and intermediate ring web members being interconnected by inner cross-webs and said intermediate and outer ring web members being interconnected by outer cross-webs, and comprising two hook members each connected to an outer cross-web of said one of said facing end-plates and extending longitudinally through an aperture and transversely behind the corresponding outer cross-web of the other of said facing end-plates. claim 2 4. The fuel channel assembly of claim 2 wherein each end-plate comprises inner, intermediate and outer concentric ring web members, said inner and intermediate ring web members being interconnected by inner cross-webs and said intermediate and outer ring web members being interconnected by outer cross-webs, and comprising two hook members each connected to an inner cross-web of said one of said facing end-plates and extending longitudinally through an aperture and transversely behind the corresponding inner cross-web of the other of said facing end-plates. claim 2 5. The fuel channel assembly of claim 1 wherein the predetermined position of relative rotational alignment is selected to produce minimum hydraulic resistance to coolant flow through said fuel bundle pair assembly. claim 1 6. The fuel channel assembly of claim 1 wherein the predetermined position of relative rotational alignment is selected to longitudinally align the fuel elements of said pair of fuel bundles. claim 1
052375943
summary
BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to the detection and quantification of certain earth formation elements surrounding a borehole, and especially elements sensitive to the nuclear activation reaction. 2. Description of the related art The detection and determination of certain elements present in an earth formation or in the well itself is of great importance in the oil production business, since the presence and amount of these elements provide useful information. Among the logging techniques used for such determination are the nuclear logging techniques, and particularly the nuclear activation method wherein a sonde comprising a high energy neutron source and a gamma ray detector is lowered in the well to investigate. Certain atoms interact with neutrons in being activated to an unstable state which decays back exponentially in time to a stable state, while emitting gamma rays of given energy representative of the activated atom. Count rates in the gamma ray detector are proportional to the total amount of the element of interest present around the sonde. By way of example, oxygen, silicon, aluminum, magnesium, or gold atoms may be activated. Oxygen atoms are representative of water. For example, a well which has been determined to be promising for oil production, is provided with a metallic casing, and cement is injected between the earth formation and the casing. Perforations are then made through the casing/cement and in the oil productive formation, so as to allow oil to flow up to the surface through a tubing beforehand arranged in the well coaxially to the casing. Unwanted vertical flow of water can occur in the cement, between the casing and the formation. This phenomenon, usually called "water channeling", causes undesirable paths between formations located at different depths, i.e. at different pressures, e.g. by allowing water from a first formation layer to mix with oil coming from a second formation layer. This phenomenon disturbs substantially the oil production. It is of great importance to identify fluid points of entrance to or exit from the borehole, as well as to determine the mechanical integrity of the cement annulus. The invention may also be used, besides the water flow detection hereabove referred to, to qualify gravel packing which is usually disposed in the annulus between the productive formation and the screened tubing, for preventing sand invasion in the tubing. As a matter of fact, aluminum and silicon are found in abundance in gravel-pack material. Aluminum e.g. is found in sintered bauxite and silicon in standard gravel pack. The use of the activation method for the detection of aluminum has been depicted in the article "The Aluminum Activation Log" from H. D. Scott and M. P. Smith, in The Log Analyst, Sep.-Oct. 1973, pages 3-12. Magnesium is another element of interest which is sensitive to the activation reaction. Magnesium is indicative of the presence of shales. Moreover, gold atoms, when bombarded with high energy neutrons, become activated. It is known to inject gold as a tracer in oil wells. Activated gold follows the fluid paths in the formation and thus, presence of gold is thus representative of fractures in the formations. Accordingly, there is a need for a better knowledge relating to the above mentioned elements in the earth formation. However, the known methods and apparatus, although satisfactory, show limitations. First, they do not offer a straightforward and simple way to distinguish the different activated elements one from the other. As a matter of fact, the gamma rays received by the detector may come from different types of activated atoms. Furthermore, the known methods do not generally provide any quick and reliable information about the radial distance between the activated elements and the borehole. According to the above, there is a need for a reliable method for obtaining quantitative and qualitative information related to given earth formation elements able to be activated by neutrons. SUMMARY OF THE INVENTION An object of the invention is a logging method and apparatus providing reliable quantitative and qualitative information on elements able to be activated present in earth formation surrounding a borehole. Another object of the invention is to identify the activated element(s). A further object of the invention is to provide information on the radial distance between the activated atoms of the element of interest and the borehole. An even further object of the invention is to provide a straightforward and simple method providing easily interpretable results to the user. The foregoing and other objects are attained in accordance with the invention by a nuclear logging method for obtaining qualitative and quantitative information related to elements in earth formation surrounding a borehole, comprising the steps of: (1) irradiating the formation with neutrons from a neutron source, the neutrons being of sufficient energy to interact with at least one element according to the activation reaction; PA1 (2) detecting and counting, at at least two locations spaced from the source, the gamma rays resulting from the activation of the element; PA1 (3) determining at each depth number of gamma ray counts detected during a time period starting when the neutron source passes that depth and ending when the detector passes that depth, this determination being made for each detector at each depth; and establishing a relationship between the instant times and the counts for all of the detecting locations; and PA1 (4) deriving from the relationship, for each depth, at least one characteristic of said element. PA1 (1) neutron source means for irradiating the earth formation with neutrons of sufficient energy to interact with atoms of at least a given element according to the activation reaction; PA1 (2) means for detecting and counting at at least two locations spaced from the source, the gamma rays emitted during the activation reaction; PA1 (3) means for determining, at each depth, the number of gamma ray counts detected during a time period starting when the source passes that depth and ending when the detector passes that depth, this determination being made for each detector at each depth; PA1 (4) means for establishing a relationship, for each depth, between the counts from the respective detectors for that depth and the corresponding times when the corresponding detector reaches that depth; and PA1 (5) means for deriving from the relationship at least one characteristic of said element. More particularly, the relationship is expressed in the form of a plot of counts versus time; the plot is approximately a straight line the slope of which is representative of the element of interest. Moreover, the number of counts is representative of the quantity of the activated element at the depth at stake and of the radial distance between the activated element and the borehole. In a preferred embodiment, the method includes moving in the borehole an elongated sonde comprising four detectors longitudinally spaced from the neutron source. The present invention also contemplates a nuclear apparatus for obtaining qualitative and quantitative information related to an element of earth formation surrounding a borehole, comprising: The characteristics and advantages of the invention will appear better from the description to follow, given by way of a nonlimiting example, with reference to the appended drawing in which:
claims
1. An x-ray beam processor system comprising:an x-ray beam generator for generating x-ray beams;multilayered planar waveguide optics wrapped into a diverging cone on a substrate, wherein the diverging cone is an inner collecting cone and x-ray beams are collected on an outer surface of the diverging cone;an outer collecting cone, wherein the outer collecting cone collects x-ray beams on an inner surface of the outer collecting cone;a planar waveguide formed by the joining of the outer collecting cone and the inner collecting cone,wherein the planar waveguide forms a converging cone that includes straight angles and x-rays increase in coherence and adherence within the converging cone; anda mirror ring for aiming x-rays exiting the planar waveguide. 2. The x-ray beam processor system according to claim 1, wherein the collecting cones and converging cone are continuous and are an integral unit. 3. The x-ray beam processor system according to claim 1, wherein the substrate is smooth stainless steel. 4. The x-ray beam processor system according to claim 1, wherein the substrate is coated with alternating layers of dense and light materials. 5. The x-ray beam processor system according to claim 1, wherein the collecting cones and converging cone are linked by a ring of polycapillary optics. 6. The x-ray beam processor system according to claim 1, wherein cooling tubes are disposed in a core to cool the surface. 7. The x-ray beam processor system according to claim 1, wherein a lead shield is placed on the outside of the cones to absorb x-rays. 8. The x-ray beam processor system according to claim 1, wherein the diverging cone is slightly concave and the outer collecting cone is slightly convex with respect to incoming x-ray beams. 9. The x-ray beam processor system according to claim 1, wherein the mirror ring comprises at least one actuated mirror. 10. The x-ray beam processor system according to claim 1, wherein the outer collecting cone is a multilayer planar waveguide wrapped into a slightly diverging cone. 11. The x-ray beam processor system according to claim 5, wherein the polycapillary optics are mounted on actuated chips such that photons are directed into the converging cone or kept out of the converging cone to control flux. 12. An x-ray beam processor system comprising:an x-ray beam generator for generating x-ray beams;an outer collecting cone adjacent to the x-ray beam generator that collects x-ray beams on its inner surface through an inlet;a multilayer waveguide wrapped into a diverging cone with slightly convex sides;a condensing cone made of a multilayer waveguide wrapped into a converging cone with straight sides,wherein the diverging cone is connected to the condensing cone at a meeting point; anda lead shield is disposed at the meeting point in between the diverging cone and condensing cone to prevent unchanneled x-ray beams from entering the condensing cone. 13. The x-ray beam processor system according to claim 12, wherein the cones are rigid and actuated as a unit for aiming. 14. The x-ray beam processor system according to claim 12, wherein lead leafs are used to form an aperture at the inlet of the collecting cone. 15. The x-ray beam processor system according to claim 12, wherein the inlet of the collecting cone is situated immediately adjacent to the x-ray beam generator. 16. The x-ray beam processor system according to claim 12, wherein the diverging and converging cones are linked by a ring of polycapillary tubes. 17. The x-ray beam processor system according to claim 12, wherein the diverging and converging cones are linked by multilayer waveguides on actuated chips for controlling flux. 18. The x-ray beam processor system according to claim 12, wherein exiting x-ray beams are manipulated by a ring of single or multiple actuated mirrors for aiming. 19. The x-ray beam processor system according to claim 12, wherein there are a plurality of x-ray beams exiting the system in different directions. 20. The x-ray beam processor system according to claim 19, wherein a lead shield is used to absorb unwanted x-ray beams at an exit cone of a waveguide. 21. An x-ray beam processor system comprising:an x-ray beam generator for generating x-ray beams;a collecting cone made of a multilayer planar waveguide wrapped into a diverging cone with slightly concave sides;a condensing cone made of a multilayer planar waveguide wrapped into a converging cone,wherein the collecting cone is connected to the condensing cone and x-rays are collected on the outside of the collecting cone;an exit located at an end of the condensing cone; anda ring of actuated mirrors disposed at the exit of the condensing cone. 22. The x-ray beam processor system according to claim 21, wherein the diverging and converging cones are linked by a ring of polycapillary tubes. 23. The x-ray beam processor system according to claim 21, wherein the diverging and converging cones are linked by multilayer waveguides on actuated chips for controlling flux. 24. An x-ray beam processor system comprising:an x-ray beam generator for generating x-ray beams;a collecting cone comprising multilayer waveguide optics;a condensing cone comprising multilayer waveguide optics; anda plurality of polycapillary tubes with channels, wherein the polycapillary tubes link the collecting cone and the condensing cone. 25. The x-ray beam processor system according to claim 24, wherein the channels of the polycapillary tubes are approximately 1 micron in diameter. 26. The x-ray beam processor system according to claim 24, wherein the diameter of the polycapillary tubes is approximately 7 microns. 27. The x-ray beam processor system according to claim 24, wherein the polycapillary tubes are actuated to change the direction of the x-ray beams. 28. The x-ray beam processor system according to claim 27, wherein the polycapillary tubes are actuated separately. 29. The x-ray beam processor system according to claim 24, wherein the polycapillary tubes can be used to turn off certain waveguides.
abstract
An x-ray optical device delivers an x-ray beam with variable convergence. The convergence or the divergence of the x-ray beams varies over different parts of the reflector. The device may include an adjustable aperture to further select the convergence or divergence. The adjustable aperture selects the convergence angle by selectively occluding a portion of the x-ray beams.
045253242
abstract
The invention is directed to a dry storage facility for storing radioactive materials such as irradiated nuclear reactor fuel elements. The radioactive materials release heat generated by the radioactive decay and are held in gas-tight storage containers. The dry storage facility includes several storage modules for receiving the storage containers. The storage modules are arranged in the enclosure of the dry storage facility which can be in the form of a secure building or an underground storage cavern. A transport passageway extends alongside of the storage modules and a transport apparatus is arranged so as to be movable along this passageway. The storage containers are cooled in the storage modules by natural convection which is direct or indirect. In order to obtain an improved transfer of heat between the storage containers and the rising cooling air, the storage containers are arranged in the storage module such that the storage containers in each of two mutually adjacent planes are arranged crosswise with respect to each other. This crosswise arrangement of the storage containers leads to a swirling of the cooling air as it rises.
summary
description
This application claims the benefit of DE 10 2012 201 856.5, filed on Feb. 8, 2012, which is hereby incorporated by reference. The present embodiments relate to a contour collimator or an adaptive filter and an associated method for adjusting a contour of a ray path of x-ray radiation. A contour collimator is used in radiation therapy for treatment of tumors. In radiation therapy, a tumor is irradiated with energy-rich radiation (e.g., with high-energy x-ray radiation of a linear accelerator). In such treatment, the contour collimator is brought into the ray path of the x-ray radiation. The contour collimator has an opening, through which radiation may pass. The contour of the opening is intended to correspond to the contour of the tumor. The contour thus forms an aperture for the passage of the x-ray radiation. This provides that the tumor, and not the adjoining healthy body tissue, is irradiated with the x-ray radiation. By embodying the contour collimator in a suitable manner almost any given contour of a tumor may be mapped. Collimators widely used for radiation therapy are multi-leaf collimators, as described, for example, in patent DE 10 2006 039793 B3. The multi-leaf collimator has a number of leaves (e.g., 160 leaves) able to be moved by motors in relation to one another to form the opening. The leaves include a material absorbing the x-ray radiation. Two packages of leaves are disposed opposite one another so that the leaves may be moved with end face sides towards one another or away from one another. Each of these leaves is displaceable individually using an electric motor. Since there may be slight deviations in the positioning of the leaves between a required specification and the actual position of the leaves currently set, each leaf has a position measurement device, with which the position currently set may be determined. In examinations with the aid of x-rays, the patient or organs of the patient may exhibit a greatly differing absorption behavior with respect to the applied x-ray radiation in the area under examination. For example, in images of the thorax, the attenuation in the area in front of the lungs is very large, as a result of the organs disposed there, while in the area of the lungs, the attenuation is small. Both to obtain an informative image and also to protect the patient, the applied dose may be adjusted as a function of the area so that more x-ray radiation than necessary is not supplied. This provides that a larger dose is to be applied in the areas with high attenuation than in the areas with low attenuation. In addition, there are applications, in which only a part of the area under examination is to be imaged with high diagnostic quality (e.g., with little noise). The surrounding parts are of importance for orientation but not for the actual diagnosis. These surrounding areas may thus be mapped with a lower dose in order to reduce the overall applied dose. Filters are used to attenuate the x-ray radiation. Such a filter is known, for example, from DE 44 22 780 A1. This has a housing with a controllable electrode matrix, by which an electrical field that acts on a fluid connected to the electrode matrix, in which x-ray radiation-absorbing ions are present, is able to be generated. These are freely movable and move around according to the field applied. By forming an appropriate field, many or few ions may accumulate correspondingly in the area of one or more electrodes in order to change the absorption behavior of the filter locally. Polymers are known from the prior art that change shape through the application of an electrical voltage. The polymers may be electroactive polymers (EAP). An example for an electroactive polymer is a dielectric elastomer. A dielectric elastomer converts electrical energy directly into mechanical work. An actuator based on a dielectric elastomer may be filtered, for example, by an elastomer film being coated on both sides with electrodes, to which an electrical voltage may be applied. Through the applied voltage, the elastomer film is pressed together in the width direction. The elastomer film expands laterally. In this process, the elastomer film may perform work and thus acts as an actuator. If the voltage between the electrodes is removed again, the elastomer film assumes an original shape again. The present embodiments may obviate one or more of the drawbacks or limitations in the related art. For example, a further contour collimator and a further adaptive filter that may map a contour robustly and rapidly are provided. In another example, an appropriate method for forming a contour is provided. An aperture forming the contour is generated with the aid of electroactive polymer elements (EAP elements) in a fluid absorbing x-ray radiation or in a fluid impermeable for x-ray radiation. In such cases, by applying an electrical voltage to the EAP elements, the fluid or parts of the fluid are displaced such that the aperture allowing the passage of x-rays is produced. EAPs are polymers that may change shape through the application of an electrical voltage. In one embodiment, a contour collimator or an adaptive filter for adjusting a contour of a ray path of x-ray radiation is provided. The apparatus includes a fluid impermeable for x-ray radiation and electroactive polymer elements actively connected to the fluid. The electroactive polymer elements are disposed and embodied such that the electroactive polymer elements form an aperture forming the contour in the fluid by application of an electrical voltage. The polymer elements activated by the voltage partly displace the fluid through the changing shape. The advantage offered by the embodiment is that the contour of a contour collimator or of an adaptive filter may be adjusted rapidly and robustly. In one embodiment, the fluid is a eutectic alloy of gallium, indium and tin. Such a fluid is available commercially under the trade name Galinstan®. In a further embodiment, the contour collimator or the adaptive filter may include a first layered unit that is filled with the fluid. The contour collimator or the adaptive filter may include a second layered unit having the electroactive polymer elements and electric leads for supplying the voltage. In one embodiment, the contour collimator or the adaptive filter may have a third layered unit impermeable for x-ray radiation with a plurality of indentations disposed in the form of a grid. In a further embodiment, the first layered unit may be disposed between the second and the third layered unit such that, on application of the electrical voltage, the electroactive polymer elements are able to be pressed into the indentations of the third layered unit. In such cases, the fluid is displaced from the areas of the indentations, so that the aperture is made in the first layered unit. In a development, the contour collimator or the adaptive filter may include at least one voltage source and switching elements, via which the electroactive polymer elements are supplied with voltage from the voltage source. The contour collimator or the adaptive filter may have an electrical control unit that controls or switches on the switching elements such that the aperture is formed. In one embodiment, a number of first, second and third layered units may be stacked. In another embodiment, a method for adjusting a contour of a ray path of x-ray radiation with a contour collimator or with an adaptive filter is provided. By applying an electrical voltage to a number of electroactive polymer elements, an aperture forming the contour is formed in a fluid impermeable for x-ray radiation. The electroactive polymer elements activated by the voltage partly displace the fluid. In addition, the electroactive polymer elements may be activated and deactivated by switching elements conducting the voltage (e.g., disconnected from the voltage source or connected to the voltage source). FIG. 1 shows a perspective diagram of one embodiment of a contour collimator 1 with a number of stacked collimator plates 3. Embodied in the collimator plates 3 are apertures 11 forming a contour 10. The apertures 11 allow x-ray radiation 12 to pass through to an object 13 (e.g., a tumor). Except for the aperture 11, the collimator plates 3 are impermeable for the x-ray radiation 12. The layered units absorbing the x-ray radiation 12 are formed by a fluid 9 absorbing x-ray radiation. Such fluids are, for example, available on the market under the trade name Galinstan®. The aperture 11 is formed where the fluid 9 is displaced or is absent. FIG. 2 shows a perspective diagram of one embodiment of an adaptive filter 2 with three stacked filter plates 3. Embodied in the filter plates 3 are apertures 11 forming the contour 10. The apertures 11 let x-ray radiation 12 pass. Except for the apertures 11, the filter plates 3 are impermeable for the x-ray radiation 12. The layered units absorbing x-ray radiation 12 are formed by a fluid 9 absorbing the x-ray radiation 12. Where the fluid 9 is displaced or is absent, the apertures 11 are formed. FIG. 3 shows a section of one embodiment of a collimator plate or of a filter plate 3 in an exploded view. The plate 3 includes a first layered unit 4 that is disposed between a second and a third layered unit 5, 6. In the first layered unit 4, there is the fluid 9 for absorbing the x-ray radiation. The second layered unit 5 includes a number of electroactive polymer elements 7 and electrical wiring for applying an electrical voltage not shown in the diagram. The third layered unit 6 includes a material transparent for x-ray radiation and possesses a plurality of indentations 8 that are disposed in the form of a grid. By application of an electrical voltage to the second layered unit 5, the electroactive polymer elements 7 are pressed into the indentations 8, which displaces the fluid 9 from areas of the first layered unit 4 corresponding thereto. FIG. 4 shows an overhead view of one embodiment of the second layered unit 5. The circular electroactive polymer elements 7, which are disposed on a carrier plate 20, are shown in the diagram. Each polymer element 7 is connected by a separate copper cable 16 to a switching element 21. The switching elements 21 are connected electrically-conductively to a voltage source 15. If the switching element 21 is switched on, electrical potential is present at the polymer element 7. Since each polymer element 7 is supplied with voltage individually, the polymer elements 7 may also be activated individually. This enables the aperture in the shape of the desired contour to be formed. The resolution of the contour increases with the number of polymer elements 7 and the smaller the elements are. FIG. 5 shows a longitudinal section through a part of one embodiment of the second layered unit 5. An insulation layer 18 lies on a printed circuit board 17 made of copper. Contact wires 19 are fed through the insulation layer that connect the circuit board 17 to the electroactive polymer elements 7 attached to a carrier plate 20. The printed circuit board 17 is connected to a plus pole of the voltage source 15. The polymer elements 7 are connected via the switching elements 21 to a minus pole of the voltage source 15 with electrical leads (e.g., copper cables 16) that are connected to the polymer elements 7. The raised shape of the polymer elements 7 indicates that these are activated. In FIG. 6, three plates 3 of one embodiment of a contour collimator 1 are presented in a block diagram. Each plate 3 includes the stacked first, second and third layered units 4, 5, 6. The second layered unit 5 is supplied by a single voltage source 15. In FIG. 6, three plates 3 of one embodiment of a filter 2 are shown in block diagram. Each filter plate 3 includes the stacked first, second and third layered units 4, 5, 6. The second layered units 5 are each supplied by a separate voltage source 15. The contour collimator is used for x-ray radiation therapy, and the filter is used for x-ray imaging. While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.
056569025
abstract
A robot having a pair of magnetic couplings that each couple a motor in a cylindrical first chamber to an associated cylindrical ring closely spaced from the cylindrical wall of said first chamber. The robot includes a mechanism to convert rotation of each of these rings into separate motions of the robot. In the preferred embodiment, these separate motions are radial and rotational.
description
The present invention refers to a filter according to the preamble of claim 1. The invention also refers to a fuel assembly. The invention will be described in an application for nuclear plants for cleaning the cooling water, which flows through a nuclear reactor of a light water type, from debris and other particles. However, the invention is not limited to any particular positioning of the filter in the nuclear plant. It is important to clean the cooling water in a nuclear plant. The purpose of the cooling water is to function as a cooling fluid and a moderator in the nuclear reactor of the nuclear plant. If debris or other particles are permitted to follow the cooling water in the core of the reactor, these may cause defects to the cladding of the fuel rods, which may result in such defects that nuclear fuel, i.e. uranium leaks out into the cooling water. At larger defect, the operation of the reactor has then to be interrupted and the failed fuel be replaced. Such a replacement is time-consuming and expensive. Debris and other particles may of course also cause defects to other components in a nuclear plant, for instance pumps. Such debris may consist of metal chips, which are formed in connection with different repairs of components of the plant, metal wires or other foreign particles which have reached the plant from outside. Particularly difficult particles are such with an elongated shape, i.e. thin wires or chips which may have a length of down to 10 mm. Such particles tend to get attached to the fuel assembly at a higher level, for instance to spacers. The particles are vibrating in the cooling water stream and may wear the cladding of the fuel rods so that a hole arises. At the same time it is important not to filter away particles which are not considered to be dangerous since all matters which are caught by the filter increase the pressure drop across the filter. Such particles may for instance be blasting sand with the size of 1–2 mm and mineral particles, which may reach the cooling water in case of defects. In order to solve this problem, it is known to provide some form of a filter in the lower part of the fuel assemblies, which include a number of fuel rods and which form the core of the reactor. The cooling water, which circulates through the reactor, passes through this lower part of the fuel assemblies. For instance, the bottom plate of the fuel assembly may be provided with a plurality of small holes through which the cooling water passes. Possible debris or other particles may thus be caught by such a filter. There are two important requirements on such a filter, on one hand it is to catch all particles which may cause defects in the reactor in an efficient manner and on the other hand it is to have a low flow resistance and pressure drop. SE-B-465 192, U.S. Pat. No. 5,481,577 and U.S. Pat. No. 5,030,412 disclose different such filters for catching debris in the cooling water flowing through a nuclear reactor. SE-B-465 192 suggests holes in the bottom plate, which have different portions with centre lines that are displaced in relation to each other. U.S. Pat. No. 5,481,577 suggests a filter which consists of a number of sheets arranged beside each other and forming passages for the cooling water. The passages are relatively thin but have a large width, which makes it possible for elongated debris particles to pass. U.S. Pat. No. 5,030,412 discloses a filter, which includes a plane metal sheet, which has relatively elongated passages that let the cooling water through but stops possible particles. Upstream of the metal plate, parallel, substantially vertical sheets are provided at a small distance from each other. These parallel sheets have an intermediate curvature, which contributes to giving the particles a desired extension transversally to the cooling water flow before they reach the metal sheet. DE-U-296 15 575 discloses another filter for a fuel assembly in a nuclear plant. The filter consists of a frame, in which a package of sheets are provided beside each other in such a way that cooling water passages are formed between the plates. The plates have a wave-shape, which either extends in a direction transversally to the flow direction or in the flow direction. The object of the present invention is to provide a filter, which has a low flow resistance and which may separate particles from a fluid in an efficient manner. Furthermore, it is aimed at a filter that can be manufactured at a low cost. This object is obtained by the device initially defined, which is characterised by the combination of the features that said sheets along the first portion have a wave-shape extending in a direction transversally to the flow direction and that said sheets along the third portion have a wave-shape extending in the flow direction. Such a filter, which may be manufactured of relatively thin sheets, has a low flow resistance since it does not require any loose components, connection members or the like which extend in the flow path. Thanks to the defined wave-shape of the sheets, a plurality of separate channels, which are arranged beside each other and which enable an efficient catching of particles in the cooling water, are obtained. The applicant has found that elongated particles are transported in the cooling water flow with an extension which substantially extends transversally to the flow direction. Such particles may consequently be caught by the filter by means of the wave-shape of the first portion. The particles, which for any reason are transported with an extension extending substantially in parallel with the flow direction, will be caught by the filter by means of the wave-shape of the third portion. The wave-shape of the sheets into directions perpendicular to each other also gives a high strength to the filter, which thus may be made self-supporting and may be mounted in for instance a fuel assembly without any frame extending around the sheets. According to an embodiment of the invention, said wave-shapes are continuous, i.e. without any sharp transitions. In such a way, the strength is further improved and at the same time the manufacturing of the sheets by form-pressing is facilitated. According to a further embodiment of the invention, said sheets have, also along the second portion a wave-shape in said direction transversally to the flow direction. Elongated particles which for any reason pass the third portion will have an extension transversally to the flow direction and thus be stopped by means of the wave-shape of the second portion. Advantageously, said sheets are along the first portion arranged beside each other in such a way that substantially each pair of adjacent sheets abuts each other at valleys and ridges, respectively, of said wave-shape, wherein each passage between two adjacent sheets forms a plurality of inlet channels arranged beside each other. Furthermore, said sheets may, along the second portion, also be arranged beside each other in such a way that substantially each pair of adjacent sheets abuts each other at valleys and ridges, respectively, of said wave-shape, wherein each passage between two adjacent sheets forms a plurality of outlet channels arranged beside each other. According to a further embodiment of the invention, said sheets are connected to each other at at least one point at said valleys and ridges, respectively, preferably by means of a fuse weld, for instance in the form of a spot weld. A further simple welding method is to weld the sheet edges with or without supply of additional weld material. The heat may be supplied by means of for instance an arc (TIG), laser or electron beam. The sheets may also be welded or brazed together with additional material. By means of such a connection of the sheets, a package of attached sheets which are self-supporting is obtained, i.e. no further members are necessary for keeping the package of sheets together. According to a further embodiment of the invention, substantially each wave of said wave-shape of the first portion and the second portion has a maximum amplitude, wherein the maximum amplitude decreases continuously in the direction towards the third portion. Advantageously, this maximum amplitude is substantially zero at the transition to the third portion. According to a further embodiment of the invention, each inlet channel has substantially the same flow area as each outlet channel. The centre line of substantially each inlet channel may advantageously be substantially concentric with the centre line of a respective corresponding outlet channel. According to a further embodiment of the invention, the third portion forms an intermediate channel between two adjacent sheets, which is arranged to convey the cooling water between the first portion and the second portion. Preferably, the sheets along substantially the whole third portion are arranged at a distance from each other, i.e. they do not abut each other. In this connection said sheets may along the third portion at least include a part portion extending substantially in parallel with said direction transversally to the flow direction. According to a further embodiment of the invention, the third portion includes projections extending into the intermediate channel. By means of such projections, possible particles, which have penetrated the filter through the inlet channel and are transported with an extension transversally to the flow direction, may in an efficient manner be prevented from flowing through the filter. Advantageously, said projections are arranged along a line extending substantially in parallel with said direction transversally to the flow direction, wherein one such part portion is arranged on each side of the projections. According to a further embodiment of the invention, said centre line of the inlet channel and the outlet channel extends between two adjacent projections of the third portion. In such a way a possible particle has to deviate further from its path in order to be able to pass through the third channel. Such projections, which may be formed by means of a plastic deformation of the sheet and/or include a tab cut from the sheet, will hinder elongated particles extending transversally to the flow direction from passing through the intermediate channel. The object is also obtained by the fuel assembly initially defined, which is characterised by the combination of features that said sheets along the first portion have a wave-shape extending in a direction transversally to the flow direction and that said sheets along the third portion have a wave-shape extending in the flow direction. The filter and the bottom part may then be arranged to convey the cooling water into said interspace. FIGS. 1–3 disclose a filter 1 for separating particles from the cooling water in a nuclear plant. The filter 1 has an inlet end 2 and an outlet end 3. The cooling water may thus flow through the filter 1 from the inlet end 2 to the outlet end 3 in a main flow direction x. The filter 1 includes a number of sheets 4, which extend substantially in the flow direction x from the inlet end 2 to the outlet end 3. The sheets 4 are arranged beside each other and form a package of attached sheets 4. The sheets 4 are preferably manufactured of a metallic material, for instance stainless steel. The sheets 4 have a first portion 4′, which extends from the inlet end 2 in the flow direction x and which has a wave-shape in a direction y extending transversally to the flow direction x. The sheets 4 also have a second portion 4″, which extends from the outlet end 3 opposite to the flow direction x and which has a wave-shape in a direction y extending transversally to the flow direction x. Furthermore, the sheets 4 have a third portion 4′″, which extends in the flow direction x between the first portion 4′ and the second portion 4″. The third portion 4′″ has a wave-shape in the flow direction x, i.e. the waves of the third portion 4′″ extend transversally to the waves of the first portion 4′ and the second portion 4″. The sheets 4 are arranged beside each other and form passages for the cooling water through the filter 1 from the inlet end 2 to the outlet end 3. Thanks to the wave-shape of the first portion 4′, the sheets 4 may be provided beside each other in such a way that substantially each pair of adjacent sheets abuts each other at abutment points or possibly along abutment lines extending along the ridges in the flow direction x. In such a way each passage between two adjacent sheets 4 will form a plurality of channels arranged beside each other between adjacent abutment lines. Such an abutment is also obtained adjacent pairs of sheets 4 along the length of the second portion 4″. The sheets 4 are attached to each other by means of one or several welds, which are applied at the abutment. In such a way, the package of sheets 4 may be kept together to a self-supporting structure. It is an advantage that the sheets have many attachment points. The particles, which by wear risk to damage the fuel, may of course damage the filter. By means of many redundant attachment points, the structure and assembly of the filter is not risked. However, it is possible to keep the package together in another way than by weld joints. For instance, various types of clamping members may be arranged around the package of sheets and press these together against each other along said abutment lines. The channels of the first portion 4′ form the inlet channels 6 for the cooling water flowing through the filter 1. In the same way, the channels of the second portion 4″ form the outlet channels 7 leading the cooling water out of the filter 1. As appears from FIG. 3, the inlet channels 6 have a longer length than the outlet channels 7 in the flow direction x. However, it is to be noted that the inlet channels 6 also may be equally long as the outlet channels 7 or even shorter than the outlet channels 7. As appears from primarily FIGS. 1 and 3, the inlet channel 6 has a centre line, which is substantially concentric with the centre line of the outlet channel 7 for each channel in the filter 1, i.e. there is an outlet channel 7 located substantially opposite to an inlet channel 6. Seen in the flow direction x, the inlet channels 6 and the outlet channels 7 have a larger width in the direction y than in a direction z, which is perpendicular to the direction y and the flow direction x and which extends transversally through the plates 4 substantially perpendicular to the extension plane x, y of the sheets 4. The width of each inlet channel 6 and outlet channel 7 in the direction y may be in the order of 8–11 mm, for instance 10 mm, and the width of each inlet channel 6 and outlet channel 7 in the direction z may be in the order of 3–6 mm, for instance 5,5 mm. The total width of the filter 1 in the flow direction x may be in the order of 20–30 mm, for instance 25 or 28 mm, wherein the inlet channel 6 has a length in the order of 6–8 mm and the outlet channel 7 has a length in the order of 3–8 mm. It may be an advantage from a manufacturing point of view if the inlet and the outlet are symmetrical. Each channel also includes an intermediate channel 8, which extends between the inlet channel 6 and the outlet channel 7 and is arranged to convey the cooling water between the first portion 4′ and the second portion 4″. The intermediate channels 8 are formed by the third portion 4″ of said sheets 4. The third portion 4′″ connects the first portion 4′ and the second portion 4″. Since the third portion 4′″ of each sheet 4 also includes a wave-shape, which is perpendicular to the wave-shape of the first portion 4′ and the second portion 4″, the intermediate channel 8 will extend in a curved path between the inlet channel 6 and the outlet channel 7. The curved path will thus have a curvature in a plane including the flow direction x and the direction z. The intermediate channel 8 does not include channels that are delimited from each other in the same way as the inlet channels 6 and the outlet channels 7. Separate intermediate channels are defined partly by projections 9 of the sheets 4. The projections 9 are in the embodiment disclosed shaped as plastically deformed buckles of the sheet 4. These buckles are positioned at the same distance from each other along a straight line as the ridges of the wave-shape of the first portion 4′ and the second portion 4″. Advantageously, the projections 9 are synchronised with the ridges of the first portion 4′ and the second portion 4″, see FIG. 1, but may also be displaced by half a wavelength in relation to the ridges of the first portion 4′ and the second portion 4″, see FIG. 2. By such a design, elongated particles, which have penetrated an inlet channel 6, are prevented in a secure manner from passing through the intermediate channel 8. It is to be noted that all sheets 4 except for the uppermost one, see FIG. 3, are provided with such projections 9. The projections 9 may be designed in many different ways, for instance they can be formed by tabs being cut from the sheet 4. The third portion 4′″ includes two part portions 10, 11, which extend substantially in parallel with the direction y and perpendicularly to the flow direction x. The part portions 10 and 11 are arranged on a respective side of the line of projections 9. The filter 1 is suitable especially but not exclusively for mounting in a fuel assembly for a nuclear plant. FIGS. 4 and 5 disclose two different types of fuel assemblies 15 and 16, respectively, which are suitable for including the filter 1. FIG. 4 discloses a fuel assembly 15 intended for a boiling water reactor, BWR, and including an upper part 20 and a bottom part 21. A number of fuel rods 22 are provided between the upper part 20 and the bottom part 21. The fuel rods are in their lower ends connected to the bottom part 21 and in their upper end to the upper part 20. Furthermore, the fuel assembly 15 includes spacers 23, which are distributed along the length of the fuel rod 22 and which serve the purpose of keeping the fuel rods 22 in a desired position. Moreover, the fuel assembly 15 includes a casing 24, which extends between the upper part 20 and the bottom part 21 and which encloses all the fuel rods 22. A filter 1 according to the description above is arranged in the bottom part 21. The filter 1 is schematically indicated in FIG. 4. The fuel assembly 15 is arranged to permit cooling water to flow into the fuel assembly through the bottom part 21 and in between the fuel rods 22. The bottom part 21 is disclosed more closely in FIGS. 6–8. From FIGS. 7 and 8 appears that the fuel assembly includes four filters 1, which are located in a respective substantially square opening 27 of the bottom part 21. The filters 1 are provided in parallel with each other and all cooling water flowing into the bottom part 21 via an inlet orifice 28 will flow through any of the filters 1. It is to be noted that the bottom part 21 also could include another number of openings 27 and filters 1, for instance one single larger opening 27 with only one filter 1. FIG. 5 discloses a fuel assembly 16 for a pressure water reactor, PWR. The fuel assembly 16 also includes an upper part 30, a bottom part 31 and a number fuel rods 32. In addition, the fuel assembly 16 includes a number of guide tubes 33 extending between and connecting the bottom part 31 and the upper part 30. The fuel rods 32 are held by means of spacers 34 which are connected with the guide tubes 33. The filter 1 is also in this case arranged in the bottom part 31 and schematically indicated in FIG. 5. All cooling water flowing into the fuel assembly between the fuel rods 32 will thus flow through the filter 1. In the embodiment disclosed in FIG. 5, the fuel assembly 16 includes only one single filter covering the whole area of the bottom part 31 seen in a horizontal section but also in this case the fuel assembly 16 may of course include more filters 1, for instance four. The invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims.
claims
1. A sealing integrity testing apparatus for detecting a defective boiler tube plug comprising: a cylindrical plug sealably locatable within a boiler tube for sealing flow through the boiler tube; a test monitor located around said cylindrical plug and said boiler tube to provide a sealed space for said plug and said tube; means for pressurizing said sealed space to a known pressure; and a pressure monitor connected to said space to measure the pressure therein to determine any pressure drop as an indication of a defective boiler tube plug. 2. An apparatus as set forth in claim 1 wherein said test member comprises a cup shaped member having a O-ring seal along the open end thereof to seal said test member against a surface around said plug and said tube. claim 1 3. An apparatus as set forth in claim 2 wherein said plug is a ribbed plug having an internally threaded extender member therein for pressing the ribs of said ribbed member against said tube to seal said tube thereby. claim 2 4. An apparatus as set forth in claim 3 wherein said test member includes a hollow tubular member sealably extending through said cup shaped member and having a threaded mandrel at the end hereof for screwing into said extender member of said ribbed plug to seal said test member to said plug and said tube. claim 3 5. An apparatus as set forth in claim 4 wherein said hollow tubular member has an aperture therein for communicating a fluid pressure in said test member to said ribbed plug area below said expanding member. claim 4 6. An apparatus as set forth in claim 5 wherein said boiler tube is located inside a nuclear reactor. claim 5
abstract
An X-ray localizer light system comprises: a long life X-ray localizer light source; an optical concentrator, the light source being situated at a first focal spot, the optical concentrator being configured for concentrating X-ray localizer light from the light source to a second focal spot; and an opaque shield having an aperture therein situated proximate to the second focal spot and being of such a geometrical shape so as to maximize light throughput while meeting light field edge contrast requirements. In another light system, the optical concentrator comprises a reflector comprising a quasi-ellipsoidal portion within which the light source is situated, a cylindrical portion situated between the quasi-ellipsoidal portion and the shield for reflecting stray light, a back reflector portion situated proximate to the shield, and a centrally-mounted portion situated between the aperture and the light source for directing back-reflected light in the direction of the aperture.
summary
047770163
claims
1. A fuel assembly comprising: upper and lower tie plates disposed so as to be spaced from each other; a plurality of fuel rods both end portions of each of which is held by said upper and lower tie plates; a plurality of spacers disposed between said upper and lower tie plates for providing spacings between said fuel rods; a water rod disposed among said fuel rods and held at its lower end portion by said lower tie plate, said water rod having holes for passing water therethrough at its side portion, and a closed upper end portion of said water rod being substantially as high as an upper end of an effective enriched fuel section, which is filled with enriched fuel, of said each fuel rod; and a channel box enclosing said fuel rods and said water rod, said upper and lower tie plates being fitted in said channel box; wherein said water rod has a larger diameter than that of each of said fuel rods, and is disposed among said fuel rods so as to be positioned at a substantially central portion of said fuel assembly. a channel box elongated axially; upper and lower tie plates mounted in upper and lower end portions of said channel box; fuel rods disposed in said channel box and held by said upper and lower tie plates at upper and lower ends of said fuel rods, respectively; a large diameter central water rod disposed among said fuel rods around an axis of said channel box, and having a larger diameter than said each fuel rod, said large diameter central water rod having a closed upper end portion, and having holes for passing water at upper and lower side portions, and having a lower end plug held by said lower tie plate, and the upper end portion of said large diameter central water rod being substantially as high as an upper end of an effective enriched fuel section of said each fuel rod; and spacers, disposed between said upper and lower tie plates, for keeping said fuel rods and said large diameter central water rod spaced from one another. upper and lower tie plates; a plurality of fuel rods each held by said upper and lower tie plates at upper and lower ends of said fuel rods, respectively, each of said fuel rods including an effective enriched fuel section and a plenum section thereon; a plurality of spacers arranged axially for keeping said fuel rods spaced from each other; and a large diameter central water rod, disposed among said fuel rods so as to be positioned at a central portion of said fuel rods, and having a larger diameter than said each fuel rod; said large diameter central water rod having a lower end plug held by said lower tie plate and an upper closed end spaced from said upper tie plate so as to not engage said upper tie plate, said large diameter central water rod having holes for passing water therethrough proximate to the upper and lower ends thereof, said large diameter central water rod having a height at the upper end substantially as high as an upper end of said effective enriched fuel section of said each fuel rod which is filled with enriched fuel pellets. 2. The fuel assembly as defined in claim 1, wherein each of said fuel rods has a natural uranium blanket on said effective fuel portion, said upper end of said water rod being set substantially as high as a lower end of said natural uranium blanket region. 3. The fuel assembly as defined in claim 1, wherein said closed upper end portion of said water rod is spaced from said upper tie plate so that said water rod does not engage said upper tie plate. 4. The fuel assembly as defined in claim 3, wherein each fuel rod includes an effective enriched fuel section and a plenum section at the upper end of said fuel rod, said closed upper end portion of said water rod having a height substantially as high as said upper end of said effective enriched fuel section and a height substantially less than an upper end of said plenum section of said fuel rod. 5. The fuel assembly as defined in claim 4, wherein each of said fuel rods has a natural uranium blanket region on said effective fuel portion, said plenum section being disposed above said natural uranium blanket region, said upper end of said water rod having a height substantially as high as a lower end of said natural uranium blanket region. 6. A fuel assembly comprising: 7. The fuel assembly as defined in claim 6, wherein the diameter of said large diameter central water rod is extended to the extent that said large diameter central water rod occupies a space corresponding to one occupied by four of said fuel rods. 8. The fuel assembly as defined in claim 7, wherein said large diameter central water rod is provided with tabs engaged with said spacers. 9. The fuel assembly as defined in claim 6, wherein said closed upper end portion of said water rod is spaced from said upper tie plate so that said water rod does not engage with upper tie plate. 10. The fuel assembly as defined in claim 9, wherein each fuel rod includes an effective enriched fuel section and a plenum section at the upper end of said fuel rod, said closed upper end portion of said water rod having a height substantially as high as said upper end of said effective enriched fuel section and a height substantially less than an upper end of said plenum section of said fuel rod. 11. The fuel assembly as defined in claim 10, wherein each of said fuel rods has a natural uranium blanket region on said effective fuel portion, said plenum section being disposed above said natural uranium blanket region, said upper end of said water rod having a height substantially as high as a lower end of said natural uranium blanket region. 12. A fuel assembly comprising: 13. The fuel assembly as defined in claim 12, wherein said large diameter central water rod occupies a space corresponding to four of said fuel rods, said large diameter central water rod having tabs for engaging said spacers. 14. The fuel assembly as defined in claim 13, wherein said upper closed end of said large diameter central water rod has a substantially flat shape and has a height so as to provide a space between said upper closed end of said large diameter central water rod and said upper tie plate.
048809896
claims
1. A shielding containing comprising: an outer shell; an inner shell supported within said outer shell, said inner shell being formed with an inner wall and outer wall defining a space therebetween for receiving radiation shielding material, said inner wall including means conforming generally to the contours of a radioaerosol source and a transport means for supporting said radioaerosol source and said transport means; and a removable cover formed with radiation shielding material and including means conforming generally to the contours of the radioaerosol transport means to be positioned thereunder, said inner wall and said cover defining means including at least one opening between them to permit the transport means placed therein to be in fluid communication with the surrounding atmosphere when in use. 2. The shielding container of claim 1 wherein said inner wall defines a ramp to support a fluid delivery tube to the radioaerosol source. 3. The shielding container of claim 1 containing auxiliary radiation shielding means to close said at least one opening when said source and said transport means are not in use to effectively isolate said source and said transport means from the surrounding atmosphere. 4. The shielding container of claim 3 including a lid to be retained on said outer shell by said auxiliary shielding means when said auxiliary shielding means is positioned to close said at least one opening.
abstract
Efficiency of installation work of equipment such as an ECCS pump is enhanced. In an installation method of equipment, a pit can unit in which an upper side frame, a pit can, various reinforcing steels including vertical reinforcing bars reinforcing the above from a periphery, and an anchor plate supporting mechanism are integrated is manufactured in advance, and the pit can unit is placed on an MMR via a lower side frame. Further, an anchor bolt unit is disposed on the anchor plate supporting mechanism after primary concrete is deposited, a relative positional relationship of respective foundation bolts relative to the pit can is corrected by using a template, and secondary concrete is deposited under the state in which the positional relationship is corrected. After that, the ECCS pump is carried into the pit can, and an installation of the ECCS pump is completed by fixing the carried ECCS pump through the respective foundation bolts of which bottom sides are embedded.
054266777
summary
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a device and method for temperature measurement of a liquid contained in a pressurizer vessel of a nuclear power plant and, more particularly, to such a device and method which measure the temperature of the liquid at preselected elevations for detecting temperature gradients in the liquid. 2. Description of the Related Art A typical nuclear power facility includes a nuclear reactor wherein a controlled nuclear reaction, which generates heat, is occurring. Typically, borated water is contained in the reactor for controlling the nuclear reaction process and for passing the heat away from the reactor. A primary loop communicating with the reactor functions to pass the borated water (i.e., the heat) away from the reactor and to transfer the heat to a secondary loop. The secondary loop is isolated from the primary loop and generates steam from the heat passed from the primary loop. The steam of the secondary loop is used to produce electricity as is well known in the art. The primary loop then returns the borated water back into the reactor where the above described process is repeated. A pressurizer vessel is connected to the primary loop for maintaining a constant pressure in the primary loop. The pressurizer vessel includes a protective shell forming an interior portion for containing any water and steam therein. The protective shell includes a cylindrical shaped side terminating at a hemispherical shaped head at both its top and bottom end, with the bottom end attached to a cylindrical support skirt. An outwardly extending flange extends radially outwardly from the skirt bottom for attaching it to its support structure, typically a floor. A nozzle at the bottom of the lower hemisphere connects to piping which attaches to the primary loop for allowing the primary loop and the pressurizer vessel to pass the borated therebetween which, in turn, functions to maintain proper pressurization of the primary loop. A heater support plate is located in a lower portion of the shell interior for receiving a plurality of electrical heaters which, during plant operation, are turned on to further heat the water or to maintain the temperature of the water at a constant temperature. A spray valve is positioned at an upper portion of the shell interior for spraying water in the shell interior which condenses the steam back to water. A liquid space temperature detector is attached to the shell side and projects radially into the interior of the shell for measuring the water temperature. During operation of the power plant, a transient event that could decrease system pressure, for example, is counteracted by increasing the water temperature via the electrical heaters which, in turn, causes a portion of the water to flash to steam. An increasing pressure transient is limited by spraying cooler water from the primary loop via the spray valve into the shell interior which, in turn, causes a portion of the steam to condense to water. The detector is positioned below and generally parallel to the water surface so that the temperature of the water is detected at a constant elevation. However, the water level varies up and down in the vessel interior during operation due to the electrical power demand of the power plant; thus, the temperature detector monitors different portions of the water as it varies up and down in the vessel interior. If a vertically oriented, temperature gradient exists, as is usually the case, it will only be detected when it passes upwardly or downwardly past the temperature detector. Although the present device for monitoring the water temperature is satisfactory, it is not without drawbacks. The water temperature is presently measured at only one elevation so that temperature gradients are only detected when the water level rises or falls enough to cause the temperature gradient to pass by the temperature detector. Therefore, temperature gradients are not detected on a real time basis. Consequently, a need exists for an improved device and method for monitoring the water temperature in a pressurizer vessel which overcomes the deficiencies of the presently known and utilized method and device. SUMMARY OF THE INVENTION The present invention provides an improvement designed to satisfy the aforementioned needs. Particularly, the present invention is directed to a pressurizer vessel for containing a liquid and steam both of which function to maintain pressure in a primary loop of a nuclear power plant comprising: a) a heater support plate disposed in an interior portion of the pressurizer vessel; b) a plurality of heaters mating with said heater support assembly for heating the liquid; c) a temperature detector operatively connected to said heater support assembly in a structural arrangement which allows for measuring the temperature of the liquid at preselected elevations; and wherein said temperature detector includes temperature measuring means for measuring a plurality of temperature readings of the liquid at preselected elevations of the liquid. In another broad form, the invention is directed to a method for measuring temperature of a liquid in a pressurizer vessel of a nuclear power plant comprising: a) installing a plurality of electrical heaters in a plurality of receiving receptacles of a heater support assembly disposed in an interior portion of the pressurizer vessel for heating the liquid; and b) replacing at least one electrical heater with a temperature detector having means for measuring the temperature of the liquid at preselected elevations. It is an object of the present invention to provide a method and apparatus for measuring the temperature of the water in the pressurizer vessel so that temperature gradients are detected on a real time basis. It is a feature of the present invention to provide a temperature measuring device for constantly measuring a plurality of temperature readings of the liquid at preselected elevations of the liquid. It is an advantage of the present invention to provide a temperature measuring device which is interchangeable with the presently utilized electrical heaters. These and other objects, features, and advantages will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described illustrative embodiments of the invention.
abstract
A target irradiation system including an irradiated target removal system having a body defining a central bore, an elevator received within the central bore, and a docking surface for placing the irradiated target removal system in fluid communication with a vessel penetration of a reactor. A target canister slidably receives the radioisotope target therein, and the elevator is configured to receive the target canister. The elevator is lowered into the reactor when irradiating the radioisotope target, and the irradiated target removal system forms a portion of a pressure boundary of the reactor during target irradiation.
summary
claims
1. A nuclear thermoacoustic device for remotely monitoring a fuel assembly in a nuclear reactor, comprising:a housing defining an interior chamber;a nuclear heat source comprising a portion of nuclear fuel disposed in the interior chamber of the housing;a stack having a hot end and a cold end, the stack disposed in a mid portion of the interior chamber of the housing with the hot end directed toward the nuclear heat source; anda volume of gas or gas mixture disposed in the interior chamber;wherein the stack is configured to receive heat energy directly from the nuclear heat source, to convert the received heat energy into an acoustic standing wave within the volume of gas or gas mixture in the interior chamber, and to provide a frequency of the acoustic standing wave corresponding to an effective temperature of gas or gas mixture in the interior chamber such that the effective temperature of the volume of gas or gas mixture in the interior chamber is capable of being monitored remotely from outside the interior chamber by measuring the frequency of the acoustic energy radiated from the housing caused by the acoustic standing wave. 2. A device in accordance with claim 1, wherein:the stack is a ceramic element having an array of parallel channels. 3. A device in accordance with claim 1, wherein:the thermoacoustic device lacks heat exchangers. 4. A device in accordance with claim 1, wherein the stack is further configured to provide an amplitude of the acoustic standing wave for monitoring information related to the volume of gas or gas mixture in the interior chamber. 5. A device in accordance with claim 1, wherein the hot end of the stack is spaced from the nuclear heat source. 6. A device in accordance with claim 1, wherein the nuclear heat source is in one end of the interior chamber.
claims
1. A method of producing Tc-99m, the method comprising:irradiating a fluid target matrix comprising Mo-100 with a proton beam to directly transform at least a portion of Mo-100 to Tc-99m via a Mo-100(p,2n)Tc-99m reaction and provide an irradiated fluid target matrix; andisolating Tc-99m from the irradiated fluid target matrix. 2. The method of claim 1, wherein the fluid target matrix further comprises water. 3. The method of claim 2, wherein the Mo-100 is derived from a water soluble molybdenum compound selected from the group consisting of molybdenum oxide, ammonium molybdate, and alkali metal molybdates. 4. The method of claim 2, wherein the water is H218O, and at least a portion of the O-18 is transformed to F-18. 5. The method of claim 4, further comprising:separating at least a portion of the F-18 from the irradiated fluid target matrix. 6. The method of claim 2 wherein the fluid target matrix has a pH of about 2 to about 12. 7. The method of claim 1 further comprising:isolating the Mo-100 from the irradiated fluid target matrix to provide a recovered sample of the Mo-100; andirradiating the recovered sample of the Mo-100 with a proton beam to transform at least a portion of the recovered sample of the Mo-100 to the Tc-99m. 8. The method of claim 1, wherein the fluid target matrix comprises an organic liquid. 9. The method of claim 1, wherein the fluid target matrix comprises a gas or a mixture of gases, and the Mo-100 is derived from a gaseous molybdenum compound. 10. The method of claim 1 wherein protons of the proton beam have an average energy of at least about 7 MeV. 11. The method of claim 1, wherein isolating Tc-99m from the fluid target matrix comprises:transferring the irradiated liquid target matrix out of an irradiation target body; andseparating at least a portion of Tc-99m from Mo-100. 12. The method of claim 11, wherein separating at least a portion of Tc-99m from Mo-100 comprises:loading a sample of the irradiated liquid target matrix onto a solid phase extraction system;eluting the Tc-99m and the Mo-100 from the solid phase extraction system with at least one eluent solution to separate at least a portion of the Tc-99m from at least a portion of the Mo-100; andcollecting at least a portion of the at least one eluent solution discharged from the solid phase extraction system to provide an eluted technetium fraction enriched in the Tc-99m and an eluted molybdenum fraction enriched in the Mo-100. 13. The method of claim 12, wherein the eluted technetium fraction is eluted from the solid phase extraction system before the eluted molybdenum fraction. 14. The method of claim 12, wherein the eluted molybdenum fraction is eluted from the solid phase extraction system before the eluted technetium fraction. 15. The method of claim 11, wherein separating at least a portion of the Tc-99m from the Mo-100 comprises:partitioning the irradiated liquid target matrix between an organic solvent phase and an aqueous phase to produce a product enriched in the Tc-99m. 16. The method of claim 15, wherein the organic solvent phase comprises methyl ethyl ketone. 17. The method of claim 1, wherein another portion of the Mo-100 in the fluid target matrix is transformed to Mo-99 in the irradiated fluid target matrix, and the method further comprisingisolating Mo-100 and Mo-99 from the irradiated fluid target matrix to provide a recovered sample of molybdenum that is substantially free of a direct irradiation produced Tc-99m; andseparating at least a portion of Tc-99m derived from a natural decay of Mo-99 from the recovered sample of molybdenum. 18. The method of claim 1, further comprising producing a plurality of radionuclides:by concurrently producing at least one of F-18, N-13, O-15, or C-11,wherein the fluid target matrix further comprises at least one of O-18, O-16, or N-14, wherein irradiating the fluid target matrix with the proton beam transforms at least a portion of Mo-100 to Tc-99m, and transforms at least a portion of the O-18 to F-18, at least a portion of the O-16 to N-13, at least a portion of the O-16 to O-15, or at least a portion of the N-14 to C-11, and thereby provide an the irradiated fluid target matrix; andseparating from the irradiated fluid target matrix at least a portion of the Tc-99m and at least a portion of the F-18, the N-13, O-15, and/or the C-11. 19. The method of claim 18, wherein the Mo-100 is derived from a water soluble molybdenum compound selected from the group consisting of molybdenum oxide, ammonium molybdate, and alkali metal molybdates. 20. The method of claim 18, wherein the O-18 is derived from H218O, 18O2, or 100Mo18O3, the O-16 is derived from H216O, 16O2, or 100Mo16O3, or the N-14 is derived from 14NH3, 14NH4+1, 14N2, 14N16O3−1, 14N18O3−1, or (14NH4)6Mo7O24. 21. The method of claim 1, further comprising:transferring an aqueous solution of a water soluble molybdenum compound comprising Mo-100 into a target assembly,wherein the aqueous solution has a pH in a range from about 2 to about 12; wherein the target assembly comprises a target body and a beam window; wherein the target body comprises stainless steel, tantalum, a cobalt alloy, or a polyether ether ketone; and wherein the beam window comprises cobalt, titanium, tantalum, tungsten, stainless steel, gold, or alloys thereof. 22. The method of claim 21, wherein the beam window has a thickness in a range from approximately 0.3 μm to 50 μm. 23. The method of claim 21, wherein irradiating the fluid target matrix comprising Mo-100 with the proton beam is performed with proton energies in a range from about 7 MeV to about 30 MeV at a beam power within a range from approximately 1.5 kW to 15.0 kW.
043127746
abstract
This invention relates to the immobilization of toxic materials, e.g., radioactive materials, in glass for extremely long periods of time. Toxic materials, such as radioactive wastes, which may be in the form of liquids, or solids dissolved or dispersed in liquids or gases, are deposited in a glass container which is heated to evaporate off non-radioactive volatile materials, if present; to decompose salts, such as nitrates, if any, and to drive off volatile non-radioactive decomposition products, and then to collapse the walls of said container on said radwaste and seal the container and immobilize the contained radwaste, and then burying the resulting product underground or at sea. In another embodiment, the glass container also contains glass particles, e.g., spheres or granules, on which the radwaste solids are deposited. In other embodiments, the glass container can be made of porous glass or non-porous glass, and/or the contained glass particles can be made of porous or non-porous glass or mixtures of porous or non-porous glass, and/or the glass container can be open at one end and closed at the other or open at both ends, and/or the glass container can be closed at one end with a porous or non-porous closure and open at the other end or closed at the other end with a porous closure. When a porous glass container and/or porous glass particles are used, the radwaste deposits within the pores of the glass which are closed during the subsequent heating step after non-radioactive volatiles have been driven off and prior to sealing the container. There results a substantially impervious glass article in which the radwaste is entrapped and which is highly resistant to leaching action. The products resulting from the use of porous glass, as the container, contents, or both, can be used as sources of radioactivity for a variety of applications in medicine, sterilization, food preservation and any other application where radiation can be beneficially employed.
claims
1. An apparatus comprising a radiation source and a processing organ for processing radiation from the radiation source, wherein a filter for suppressing undesired atomic and microscopic particles is placed between the radiation source and the processing organ, which filter comprises a plurality of foils or plates having surfaces for trapping atomic and microscopic particles thereon, wherein each foil or plate essentially points in a radial direction when viewed from the radiation source. 2. The apparatus according to claim 1 , wherein the foils or plates are positioned in a honeycomb construction. claim 1 3. The apparatus according to claim 1 , wherein the foils or plates are coneshaped and are positioned concentrically. claim 1 4. The apparatus according to claim 1 , wherein in the radial direction the foils or plates are positioned such as to be evenly distributed in relation to one another. claim 1 5. The apparatus according to claim 1 , wherein the radiation source and the processing organ are placed in a buffer gas, and wherein a distance between the radiation source and a proximal end of the filter in relation to the radiation source is selected subject to a pressure and a type of buffer gas. claim 1 6. The apparatus according to claim 5 , wherein the buffer gas is krypton, wherein the pressure is at least approximately 0.1 Torr, and wherein the distance between the radiation source and the proximal end of the filter is 5 cm. claim 5 7. The apparatus according to claim 5 , wherein a length of the filter, which is formed by the distance between the proximal end of the filter and its distal end in relation to the radiation source, is selected subject to the pressure of the buffer gas and a form of the filter. claim 5 8. The apparatus according to claim 7 , wherein the length of the filter is at least 1 cm. claim 7 9. The apparatus according to claim 1 , wherein the number of plates in the filter is adjusted subject to a thickness of each plate and a desired optical transparency of the filter as determined by the formula claim 1 in which d=a distance between two plates of the filter at a proximal side of the filter; and d f =a thickness of a plate of the filter. 10. The apparatus according to claim 9 , wherein the number of plates is adjusted such that the distance between two plates is approximately 1 mm. claim 9 11. The apparatus according to claim 1 , wherein a surface of the plates is rough. claim 1 12. A filter for suppressing undesired atomic and microscopic particles which are emitted by a radiation source, wherein a plurality of plates are positioned substantially parallel in relation to one another, for trapping atomic and microscopic particles on their respective surfaces, wherein the plates are directed radially from the radiation source.
047059508
description
DETAILED DESCRIPTION With reference to the drawings, a vacuumized specimen chamber 1 and a specimen-exchanging chamber 2 are connected with each other by way of a specimen-removing aperture 3. A valve mechanism 4 is designed to open and close a specimen-removing aperture 3 so as to accomplish the connection or the disconnection between the specimen chamber 1 and the specimen-exchanging chamber 2. In the valve mechanism, when the thrusting operation of an operation shaft 401, caused by a driving device (not shown) is carried out outside the specimen-exchanging chamber 2, a valve body 403, connected to the tip of the operation shaft 401 by a connector 402, is thrust at a stopper 404. As a result, the valve body 403 closely fits on a valve seat surface on the side of the specimen-exchanging chamber 2 situated around the specimen-removing aperture 3 so as to close the specimen-removing aperture 403. Here, a stopper 405 serves to prevent more removal of the operation shaft 401 o the left side in FIG. 3 than it is really needed. On the contrary, when the operation shaft 401 is pulled by the driving device (not shown), the valve body 403 is removed to the location at a distance from the specimen-removing aperture 3 so as to open the aperture. A plate spring 406 has a function of always acting in direction of urging the valve body 403 away from the valve seat surface. Accordingly, when the valve body 403 is removed so as to open the specimen-removing aperture 3, substantially at the same time with the removal, the valve body 403 is displaced from the valve seat surface and thus the removal of the valve body 403 is smoothly carried out. Further, in case of carrying out the operation of pushing or pulling the operation shaft 401, it is possible to prevent the connection between the specimen-exchanging chamber 2 and an outside thereof bellows 407. The specimen-exchanging chamber 2 is composed of a base part 201 and a lid 203 coupled to be loaded and unloaded with the base part through a vacuum rail 202. The lid 203 is coupled to the base part 201 by a member 204 by a hinge (not shown). Thus, the loading and unloading of the lid 203 with the base part 201 is carried out by a rotational movement of the lid 203 at the center of hinge. Inside the specimen-exchanging chamber 2, the exhaust is accomplished through an exhaust aperture 5 by an exhaust device. As long as the exhaust inside the specimen-exchanging chamber 2 is carried out and a predetermined vacuum degree is maintained, the vacuum of the specimen chamber 1 is maintained even if the specimen-removing aperture 3 is opened. When the lid 203 is opened, the inside of the specimen-exchanging chamber 2 is to the ambient air. Then, there is no need of accomplishing the exhaust inside the specimen-exchanging chamber 2 and thus, the exhausting inside the specimen-exchanging chamber by the exhaust device 6 is topped and the specimen-removing aperture 3 is closed by the valve mechanism 4. Consequently, even if the inside of the specimen-exchanging chamber 2 is exposed to the ambient air, there the vacuum inside the specimen chamber 1 is maintained. Now, it is presumed that the specimen-removing aperture is opened and that the inside of the specimen-exchanging chamber 2 is maintained at a predetermined vacuum degree. Under the above-described condition, when a rotatable shaft 7, extending through the wall of the specimen-exchanging chamber 2 from the outside to the inside of the chamber in a manner of keeping vacuum of the chamber is rotated by a motor (not shown) connected at the outside of the specimen-exchanging chamber 2, the rotation is transmitted to a feed screw 10 supported by bearings 8 and 9 by way of bevel gears 11, 12 provided in the rotatable shaft 7 and the feed screw 10 and engaging with each other. Thus, a nut 13 threaded through the feed screw 8 is removed to the right side in FIGS. 1 and 3. A guide 14 is disposed in parallel with the feed screw 10 and a slider 15 is slidably connected to the guide 14. In order to smoothly remove the slider 15, a plurality of balls (not shown) are interposed between the guide 14 and the slider 15. A removable element 16 is fixed so as to bridge the nut 13 and the slider 15. Accordingly, the removal of the nut 13 to the right serves to remove the removable element 16 to the right without rotating the element 16. With the removal of the removable nut 16 to the right, the specimen holder 17', coupled to be loaded and unloaded with the removable element 16 through a specimen-chucking mechanism 17 provided in the removable element 16, is guided by a pair of guides 18 and thus is passed through the specimen-removing aperture 3 and is transferred to a pair of guides 19 disposed in the specimen chamber 1. Either end of the specimen holder 17' is shaped into a V-like shape. The specimen holder 17' is guided by a pair of guides 18 in the form of stretching V-forms at both ends between lower side rollers 30 and upper side rollers 31. This design is arranged so as to enable a smooth removal of the specimen holder 17'. Thus, when the specimen holder 17' is removed to the specimen chamber 1, a wafer 22 forming a specimen is retained on the specimen holder 17' by means of a well-known method. Accordingly, with the removal of the specimen holder 17' to the specimen chamber 1, the wafer 22 forming the specimen is similarly removed to the specimen chamber 1. Thus, inside the specimen chamber 1, it is possible to carry out a desired treatment of the specimen. Concretely, this treatment means, for example, in case of a scanning electron microscope, two-dimensional scanning using an electron beam required for observation of the image of specimen and, in case of an electron-beam drawing device, patterning of a specimen by using an electron beam. The specimen-chucking mechanism 17 as shown in FIG. 4 includes a switching shaft 1701 extending through the wall of the specimen-exchanging chamber 2 from the outside to the inside of the chamber in a manner enabling a maintaining of vacuum therein. The driving device (not shown), connected to the outer end thereof, serves to selectively switch a chuck arm 1703 and an unchuck arm 1704 provided in the inside end thereof to a chuck position and an unchuck one. When the chuck arm 1703 is switched to the chuck position, the chuck arm 1703 serves to rotate a lever 1705 counterclockwise with a center as a supporting shaft 1706 supporting the lever on the removable element 16 and to be located as shown by a solid line. Namely, the lever 1705 is stopped at the location where a stopper 1710 always biased counterclockwise by a spring 1709 with a center as a supporting shaft 1708 provided in a lever 1707 and releasably supporting the lever 1707 to the removable element 16 is made to be thrust on a stopper surface 1711. On the other hand, when the unchuck arm 1704 is switched to the unchuck position, the lever 1705 serves to rotate in a clockwise direction by an unchuck arm 1704 and stops at the location where the stopper 1710 is thrust on the stopper surface 1713. The sample holder 17' provides a concave portion 1713, a part of which is designed to be an engaging part 1714 to be engaged with a L-form tip portion of the lever 1705. In the process where the specimen 22 is removed from the specimen-exchanging chamber 2 to the specimen chamber 1, the unchuck arm 1704 stays at the unchuck position and thus, the stopper 1710 is in contact with the stopper surface 1713 and the L-form tip portion of the lever 1705 enters into the concave portion 1713, but is not engaged with the engaging part 1714. Upon completion of removal of the specimen 22 to the specimen chamber 1, the feed screw 10 is reversely rotated under the state where the specimen 22 and the specimen holder 17' are left in the specimen chamber 1. By the reverse rotation, the removable element 16 is removed to the specimen-exchanging chamber 2. Afterwards, the specimen-removing aperture 3 is closed by the valve mechanism 4. The predetermined treatment is carried out with respect to the specimen 22 remaining in the specimen chamber 1. After the treatment specimen 22 with a new specimen with the exchange being carried out in the following manner. The chuck arm 1703 is switched to the chuck position. By this switching, the stopper 1710 contacts the stopper surface 1711. Next, the specimen-removing aperture 3 is opened and the removable element 16 is removed to the specimen chamber 1. When the L-form tip portion of the lever 1705 passes through a projecting part 1714a just before the engaging part 1714, this projecting part serves to rotate the L-form tip portion slightly in a clockwise direction, with a center, the supporting shaft 1706 as opposing a tractive force of the spring 1709. Then, the L-form tip portion passes through the projecting portion 1714a, when it is automatically engaged with the engaging part 1714 by the tractive force of the spring 1709. Afterwards, the feed screw 10 is rotated in a reverse direction. By this reverse rotation, the specimen holder 17' where the removable element 16, therefore, the treated specimen 22 is retained, is removed to the specimen-exchanging chamber 21. After that, the valve mechanism 4 serves to close the specimen-removing aperture 3 and then to release the engagement of the L-form tip portion of the lever 1705 with the engaging part 1714. Accordingly, under this state, when the lid 203 is opened and the specimen-exchanging chamber 2 is opened to the ambient air, it is possible to exchange the treated specimen 22 with a new specimen. After exchanging a specimen, the lid 203 is closed and the exhausting is carried out so as to bring the specimen-exchanging chamber 2 to a predetermined degree of vacuum. After that, in order to remove an exchanged new specimen to the specimen chamber 1, the same operation as described above should be carried out. A base plate 20 is provided on the bottom of the specimen-exchanging chamber 2 with the bearings 8, 9 and the guide 14 being fixed on the base plate 20. A support means for supporting a pair of guides 18 is also fixed on the base plate 10. According to the embodiment described above, there are no chances of a breaking down of the vacuum of the specimen-exchanging chamber 1 when exchanging a specimen. Further, the removal of a specimen between the specimen chamber 1 and the specimen-exchanging chamber 2 is automatically carried out by a linear movement of the chucking mechanism 17. Accordingly, conditions of raising or creating do not arise and thus, a dry vacuumizing is possible. Further, it is possible to automatically accomplish drive the feed screw 10, switching of positions of the lever 1705 and drive of the valve mechanism 4 from the outside of the specimen-exchanging chamber 2. Thus, the automatic switching of a specimen can be easily realized. It is also possible to delete the bevel gears 11 and 12 and the rotation shaft 7 and to project the feed screw 10 from the inside of the specimen-exchanging chamber 2 to the outside thereof in a vacuum sealed manner and to directly connect the feed screw 10 with a motor (not shown). In the embodiment described above, it is possible for the persons in the art to which the present invention pertains to accomplish some transformations or conversions without departing from the principle of the present invention and I therefore do not wish to be limited to the details shown and described hereinabove, but intend to cover all modifications as are encompassed by the scope of the appended claims.
description
The present application is related to and claims the benefit of the earliest available effective filing date(s) from the following listed application(s) (the “Related Applications”) (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 Related Application(s)). All subject matter of the Related Applications and of any and all parent, grandparent, great-grandparent, etc. applications of the Related Applications, including any priority claims, is incorporated herein by reference to the extent such subject matter is not inconsistent herewith. Related Applications: For purposes of the USPTO extra-statutory requirements, the present application constitutes a continuation of U.S. patent application Ser. No. 13/373,139, entitled SYSTEMS, DEVICES, METHODS, AND COMPOSITIONS INCLUDING FLUIDIZED X-RAY SHIELDING COMPOSITIONS, naming Philip A. Eckhoff, William H. Gates III, Peter L. Hagelstein, Roderick A. Hyde, Jordin T. Kare, Robert Langer, Erez Lieberman, Eric C. Leuthardt, Nathan P. Myhrvold, Michael Schnall-Levin, Clarence T. Tegreene, Lowell L. Wood, Jr. as inventors, filed 3, Nov. 2011, 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. The United States Patent Office (USPTO) has published a notice to the effect that the USPTO's computer programs require that patent applicants reference both a serial number and indicate whether an application is a continuation, continuation-in-part, or divisional of a parent application. Stephen G. Kunin, Benefit of Prior-Filed Application, USPTO Official Gazette Mar. 18, 2003. The present Applicant Entity (hereinafter “Applicant”) has provided above a specific reference to the application(s) from which priority is being claimed as recited by statute. Applicant understands that the statute is unambiguous in its specific reference language and does not require either a serial number or any characterization, such as “continuation” or “continuation-in-part,” for claiming priority to U.S. patent applications. Notwithstanding the foregoing, Applicant understands that the USPTO's computer programs have certain data entry requirements, and hence Applicant has provided designation(s) of a relationship between the present application and its parent application(s) as set forth above, but expressly points out that such designation(s) are not to be construed in any way as any type of commentary and/or admission as to whether or not the present application contains any new matter in addition to the matter of its parent application(s). In an aspect, the present disclosure is directed to, among other things, an x-ray shielding fluid composition including a plurality of x-ray shielding particles, each having at least a first x-ray shielding agent and a second x-ray shielding agent, and a carrier fluid. In an embodiment, the second x-ray shielding agent includes one or more absorption edges different from the first x-ray shielding agent. In an embodiment, the plurality of x-ray shielding particles includes a second x-ray having one or more characteristic x-ray absorption edges different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes one or more k-edges, or one or more l-edges, different from the first x-ray shielding agent. In an embodiment, the plurality of x-ray shielding particles includes a second x-ray having an x-ray mass attenuation coefficient different from the first x-ray shielding agent. In an embodiment, the plurality of x-ray shielding particles include a second x-ray having at least one k-edge having an energy level lower than at least one k-edge of the first x-ray shielding agent In an embodiment, the plurality of x-ray shielding particles include a second x-ray having at least one k-edge or l-edge corresponding to an x-ray energy absorption minimum of the first x-ray shielding agent. In an aspect, the present disclosure is directed to, among other things, an x-ray shielding fluid composition including 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, and a carrier fluid. In an embodiment, the x-ray shielding fluid composition includes a third x-ray shielding agent having one or more absorption edges different from the second x-ray shielding agent and the first x-ray shielding agent. In an embodiment, the x-ray shielding fluid composition includes a fourth x-ray shielding agent, the fourth x-ray shielding agent having one or more absorption edges different from the third x-ray shielding, the second x-ray shielding agent, and the first x-ray shielding agent. In an embodiment, the x-ray shielding fluid composition includes a fifth x-ray shielding agent, the fifth x-ray shielding agent having one or more absorption edges different from the fourth x-ray shielding agent, the third x-ray shielding, the second x-ray shielding agent, and the first x-ray shielding agent. In an aspect, the present disclosure is directed to, among other things, dynamic x-ray shielding garments (e.g., aprons, coats, eye protectors, gloves, neck protectors, pants, scrub caps, shirts, skirts, sleeves, socks, surgical scrubs, vests, etc.) including at least a first layer including a support structure having a plurality of interconnected interstitial spaces that provide a circulation network for an x-ray shielding fluid composition. In an embodiment, the support structure is configured to constrain the x-ray shielding fluid composition to move along one or more of the plurality of interconnected interstitial spaces. In an embodiment, a dynamic x-ray shielding garment includes at least one x-ray shielding fluid reservoir assembly including one or more x-ray shielding fluid reservoirs. In an embodiment, the x-ray shielding fluid reservoir assembly is structured and arranged to hold the x-ray shielding fluid composition and to selectively enable fluid communication between one or more x-ray shielding fluid reservoirs and the plurality of interconnected interstitial spaces. In an embodiment, the dynamic x-ray shielding garment includes an x-ray shielding fluid supply controller operable to manage fluid flow of the x-ray shielding fluid composition to or from the x-ray shielding agent reservoir assembly, and along one or more of the plurality of interconnected interstitial spaces. In an aspect, the present disclosure is directed to, among other things, a dynamic x-ray shielding method including receiving x-ray potential exposure event data associated with delivery of an x-ray radiation stimulus from an x-ray radiation-emitting system. In an embodiment, the dynamic x-ray shielding method includes directing fluid flow of an x-ray shielding fluid composition received in an x-ray shielding fluid reservoir assembly associated with a dynamic x-ray shielding garment, to or from the x-ray shielding agent reservoir, and along one or more of a plurality of interconnected interstitial spaces within the dynamic x-ray shielding garment, responsive to the x-ray potential exposure event data. In an aspect, the present disclosure is directed to, among other things, an x-ray shielding method including actuating fluid flow of an x-ray shielding fluid composition received in one or more x-ray shielding fluid reservoirs associated with a dynamic x-ray shielding garment, to or from the x-ray shielding agent reservoir, and along one or more of a plurality of interconnected interstitial spaces within the dynamic x-ray shielding garment responsive to a determination that an x-ray radiation-emitting system is in operation. In an aspect, the present disclosure is directed to, among other things, an x-ray shielding method including actuating fluid flow of an x-ray shielding fluid composition received in one or more x-ray shielding fluid reservoirs associated with a dynamic x-ray shielding garment, to or from the x-ray shielding agent reservoir, and along one or more of a plurality of interconnected interstitial spaces within the dynamic x-ray shielding garment responsive to an input associated with a potential delivery of an x-ray radiation stimulus from an x-ray radiation-emitting system. In an aspect, the present disclosure is directed to, among other things, a dynamic x-ray shielding system including an x-ray shielding fluid reservoir configured to store and supply at least a first x-ray shielding fluid composition and a second x-ray shielding fluid composition. In an embodiment, the dynamic x-ray shielding system includes at least a first layer including a first flow path in fluid communication with the x-ray shielding fluid reservoir assembly and configured to receive the first x-ray shielding fluid composition. In an embodiment, the first flow path includes a first flow valve assembly selectively actuatable between an open state which permits fluid flow through the first flow valve assembly such that the first x-ray shielding fluid composition flows from the x-ray shielding fluid reservoir assembly along at least a portion of the first flow path, and a restrict state which restricts fluid flow through the first flow valve assembly. In an embodiment, the dynamic x-ray shielding system includes a second layer including a second flow path in fluid communication with the x-ray shielding fluid reservoir assembly and configured to receive the second x-ray shielding fluid composition. In an embodiment, the second flow path includes a second flow valve assembly selectively actuatable between an open state which permits fluid flow through the second flow valve assembly such that the second x-ray shielding fluid composition flows from the x-ray shielding fluid reservoir assembly along at least a portion of the first flow path, and a restrict state which restricts fluid flow through the second flow valve assembly. In an embodiment, the dynamic x-ray shielding system includes an x-ray, shielding fluid supply controller associated with at least the first flow valve assembly and the second flow valve assembly and configured to selectively actuate the first or the second flow valve assembly to regulate fluid flow of a defined quantity of at least one of the first x-ray shielding fluid composition or the second x-ray shielding fluid composition from the reservoir, through at least one of the first flow valve or the second flow valve, into the at least a portion of the first flow path or the second flow path. In an aspect, the present disclosure is directed to, among other things, a dynamic x-ray shielding method including receiving x-ray potential exposure event data associated with delivery of an x-ray radiation stimulus from an x-ray radiation-emitting system. In an embodiment, the dynamic x-ray shielding method includes concurrent or sequential actuating fluid flow of a first x-ray shielding fluid composition or the second x-ray shielding fluid, received in an x-ray shielding fluid reservoir assembly, to or from the x-ray shielding agent reservoir and along respectively one of a first flow path or a second flow path of a dynamic x-ray shielding apparatus, responsive to potential exposure event data indicative of an x-ray potential exposure event. In an aspect, the present disclosure is directed to, among other things, a dynamic x-ray shielding method including determining an actuate flow condition. In an embodiment, the dynamic x-ray shielding method includes concurrent or sequential actuating fluid flow of a first x-ray shielding fluid composition or the second x-ray shielding fluid, received in a plurality of x-ray shielding fluid reservoirs, to or from the plurality of x-ray shielding fluid reservoirs and along respectively one of a first flow path or a second flow path of a dynamic x-ray shielding apparatus, responsive to the actuate flow condition. 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. Medical systems (e.g., fluoroscopy systems, computed tomography systems, radiography systems, radiation treatment systems, x-ray imaging system, etc.) are valuable diagnostics and treatment tools in medical practice. Likewise, cabinet x-ray systems (e.g., closed x-ray systems, x-ray inspection systems, x-ray screening systems, x-ray security systems, baggage x-ray systems, etc.) are useful tools for detection of contraband, contaminants, or manufacturing defects without damaging or destroying the item being examined. Exposure to radiation may cause cancer (especially leukemia), birth defects in the children of exposed parents and cataracts. These health effects (excluding genetic effects) have been observed in studies of medical radiologists, uranium miners, radium workers, and radiotherapy patients who have received large doses of radiation. Studies of radiation effects on laboratory animals have provided a large body of data on radiation health effects including genetic effects. Most of the studies mentioned above involve acute exposure to high levels of radiation. Acute exposure can be, for example, exposure to hundreds of rem (Röentgen equivalent in man) within a few hours or less. Such radiation doses far exceed the occupational dose limits currently recommended (less than 5 rem per year). However, the major concerns today are about delayed health effects arising from chronic cumulative exposure to radiation. The major health concern from chronic cumulative exposure to radiation is cancer which may appear 5 to 20 years after exposure to relatively low levels of radiation. The current limits for radiation exposure set by the FDA for adults are: 50 mSv (millisieverts) (5 rems) per year and 30 mSv (3 rems) per single dose. (http://tech.mit.edu/Bulletins/Radiation/rad5.txt). For children, who are more vulnerable to radiation, the limits are 5 mSv (0.5 rems) annually and 3 mSv (0.3 rems) per single dose. A lifetime occupational exposure level of no greater than 400 mSv (40 rems) is recommended by government agencies (Hall et al., Canadian Fam. Physician 52: 976-77, 2006). Compliance with these radiation exposure limits is complicated by the lack of cumulative radiation exposure data, especially in regard to lifetime exposure limits. Also the increased usage of computed tomography scans for medical imaging (Brenner and Hall, N. Engl. J. Med. 357: 2277-84, 2007) has created a need for monitoring, x-ray shielding, and protecting against a radiation exposure event to avoid exceeding exposure limits. X-ray shielding fluid compositions are described with which one or more methodologies or technologies can be implemented such as, for example, providing x-ray shielding and protection. Factors affecting the radiation amount or dose received from an x-ray source include the exposure time, the distance from x-ray source, the utilization of x-ray shielding, or the like. The type and amount of material to attenuate (shield) x-ray radiation is dependent upon the energy of the x rays, the material's chemical composition, and the material's density. In an embodiment, an x-ray shielding fluid composition includes a plurality of x-ray shielding particles and a carrier fluid. Non-limiting examples of particles include glass beads having one or more x-ray shielding agents, nanoparticles having a plurality of shielding agents within a glass material matrix, particles having a plurality of elemental dopants within a material matrix, or the like. In an embodiment, each of the x-ray shielding particles includes at least a first x-ray shielding agent and a second x-ray shielding agent. In an embodiment, the plurality of x-ray shielding particles includes a third x-ray shielding agent, the third x-ray shielding agent having one or more absorption edges different from the second x-ray shielding agent and the first x-ray shielding agent. In an embodiment, the plurality of x-ray shielding particles includes a fourth x-ray shielding agent, the fourth x-ray shielding agent having one or more absorption edges different from the third x-ray shielding agent, the second x-ray shielding agent, and the first x-ray shielding agent. In an embodiment, the plurality of x-ray shielding particles includes a fifth x-ray shielding agent, the fifth x-ray shielding agent having one or more absorption edges different from the fourth x-ray shielding agent, the third x-ray shielding agent, the second x-ray shielding agent, and the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes one or more absorption edges different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes one or more characteristic x-ray absorption edges different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes one or more k-edges, or one or more l-edges, different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes an x-ray mass attenuation coefficient different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes at least one k-edge having an energy level lower than at least one k-edge of the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes at least one k-edge or l-edge corresponding to an x-ray energy absorption minimum of the first x-ray shielding agent. In an embodiment, the plurality of x-ray shielding particles includes one or more x-ray radio-opaque materials (e.g., barium sulfate, silicon carbide, silicon nitride, alumina, zirconia, etc.). In an embodiment, the plurality of x-ray shielding particles includes one or more x-ray attenuating materials. In an embodiment, the plurality of x-ray shielding particles includes one or more x-ray attenuating ceramic materials. In an embodiment, the plurality of x-ray shielding particles comprise one or 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. Among ferromagnetic materials, examples include, but are not limited to, 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 examples of ferromagnetic materials include, but are not limited to, 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 examples of ferromagnetic materials include, but are not limited to, 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 examples of ferromagnetic materials include, but are not limited to, 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, one or more of the plurality of x-ray shielding particles include at least one iron oxide. Among iron oxides, examples include, but are not limited to, 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. Among iron oxides, examples include, but are not limited to, 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 are configured to include one or more magnetic components. In an embodiment, the plurality of x-ray shielding particles comprise 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). Among ferrimagnetic materials, examples include, but are not limited to, ferrimagnetic oxides (e.g., ferrites, garnets, or the like). Further 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. Further 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. Further examples of ferromagnetic 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, the plurality of x-ray shielding particles comprises one or more paramagnetic materials. In an embodiment, at least one of the first x-ray shielding agent or the second x-ray shielding agent 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 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 one or more SiO2—PbO-alkali metal oxide glasses, CaO—SrO—B2O3 glasses, or boron-lithium glasses. 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, at least one of the first x-ray shielding agent or the second x-ray shielding agent includes 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 mercury (Hg), lead (Pb), lithium fluoride (LiF), 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 teflon (C2F4). In an embodiment, the carrier fluid ranges from about 1 to about 98 volume percent of the total volume of the x-ray shielding fluid composition. In an embodiment, an x-ray shielding fluid composition includes a carrier fluid including a fluid material having one or more x-ray absorption edges. In an embodiment, the carrier fluid includes a fluid material having one or more x-ray absorption edges different from the second x-ray shielding agent and the first x-ray shielding agent. In an embodiment, the carrier fluid includes a fluid material having one or more x-ray absorption edges different from the second x-ray shielding agent and the first x-ray shielding agent. In an embodiment, the carrier fluid includes a fluid that is substantially non-volatile, non-polar, or non-aqueous. In an embodiment, the carrier fluid includes mineral oil, paraffin oil, cycloparaffin oil, or synthetic hydrocarbon oil. In an embodiment, the carrier fluid includes a gas carrier. In an embodiment, the carrier fluid includes an aerosol. In an embodiment, the carrier fluid includes two or more immiscible liquids. In an embodiment, an x-ray shielding fluid composition includes one or more anti-flocculant agents. In an embodiment, the anti-flocculant agents adsorb onto the x-ray shielding particle surface, increasing the x-ray shielding particle electrostatic repulsion. The increased electrostatic repulsion of like charged x-ray shielding particles decreases the occurrence of x-ray shielding particle aggregates. In an embodiment the addition of anti-flocculant agents enhanced stability of the x-ray shielding fluid composition. In an embodiment, at least some of the plurality of x-ray shielding particles are coated with an anti-flocculant coating. In an embodiment, the x-ray shielding fluid composition 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, and a carrier fluid. In an embodiment, the second x-ray shielding agent includes one or more characteristic x-ray absorption edges different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes one or more k-edges, or one or more l-edges, different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes an x-ray mass attenuation coefficient different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes at least one k-edge having an energy level lower than at least one k-edge of the first 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 lead (Pb), lithium fluoride (LiF), 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 teflon (C2F4). In an embodiment, the x-ray shielding fluid composition includes a third x-ray shielding agent, the third x-ray shielding agent having one or more absorption edges different from the second x-ray shielding agent and the first x-ray shielding agent. In an embodiment, the x-ray shielding fluid composition includes a fourth x-ray shielding agent, the fourth x-ray shielding agent having one or more absorption edges different from the third x-ray shielding, the second x-ray shielding agent, and the first x-ray shielding agent. In an embodiment, the x-ray shielding fluid composition includes a fifth x-ray shielding agent, the fifth x-ray shielding agent having one or more absorption edges different from the fourth x-ray shielding agent, the third x-ray shielding, the second x-ray shielding agent, and the first x-ray shielding agent. FIGS. 1 through 4 show a dynamic x-ray shielding system 100 including one or more dynamic x-ray shielding devices 102, in which one or more methodologies or technologies can be implemented such as, for example, providing x-ray shielding, x-ray radiation protection, or the like. In an embodiment, the dynamic x-ray shielding device 102 forms part of a dynamic x-ray shielding garment 104. In an embodiment, the x-ray shielding system 100 includes one or more dynamic x-ray shielding devices 102 having at least a flexible layer 106 including a support structure 108 having a plurality of interconnected interstitial spaces 110 that provide a circulation network for an x-ray shielding fluid composition. In an embodiment, the dynamic x-ray shielding system 100 includes one or more x-ray shielding fluid reservoir assemblies 112 including one or more reservoirs 114 configured to store and supply an x-ray shielding fluid composition to or from the x-ray shielding agent reservoir 114, and along one or more of the plurality of interconnected interstitial space 110. In an embodiment, the dynamic x-ray shielding system 100 includes one or more pump assemblies 116 including one or more pumps 117 (e.g., mechanical pumps, magnetic pumps, centrifugal pumps, diaphragm pumps, gear pumps, flexible impeller pumps, peristaltic pumps, piston pumps, rotary valve pumps, etc.) that circulates the x-ray shielding fluid composition within at least a portion of the circulation network. For example, in an embodiment, the dynamic x-ray shielding system 100 includes an x-ray shielding fluid composition pump assembly 116 that is in fluid communication with at least one of the x-ray shielding fluid reservoir assembly 112 or the circulation network and that supplies and circulates the x-ray shielding fluid composition to or from the x-ray shielding agent reservoir assembly 112, and along one or more regions within the circulation network. In an embodiment, the dynamic x-ray shielding garment 104 includes one or more pumps 117 that configured to generate magnetic forces on magnetic components of the x-ray shielding fluid composition to circulate the x-ray shielding fluid composition to or from the x-ray shielding agent reservoir assembly 112, and along one or more regions within the circulation network. In an embodiment, the dynamic x-ray shielding devices 102 includes one or more pumps 117 that circulate the x-ray shielding fluid composition within at least a portion of the circulation network. In an embodiment, the dynamic x-ray shielding system 100 includes one or more flow valve assemblies 118, including one or more flow valves 119, that are selectively actuatable between an open state which permits fluid flow through the one or more valve assemblies 118 such that the x-ray shielding fluid composition flows from the x-ray shielding fluid reservoir assembly 112 along at least a portion of a flow path, and a restrict state which restricts fluid flow through the assembly 118. In an embodiment, the dynamic x-ray shielding system 100 includes one or more flow valves 119 to selectively direct flow of the x-ray shielding fluid composition to or from the x-ray shielding agent reservoir 114. In an embodiment, the dynamic x-ray shielding system 100 includes one or more flow valves 119 to selectively direct flow of the x-ray shielding fluid composition within the circulation network. In an embodiment, dynamic x-ray shielding devices 102 includes support structure 108 configured to constrain the x-ray shielding fluid composition to move along one or more of the plurality of interconnected interstitial spaces 110. In an embodiment, the support structure 108 defines one or more tubular structures (e.g., as shown in FIG. 5) forming part of the plurality of interconnected interstitial spaces 110 that provide the circulation network for the x-ray shielding fluid composition. In an embodiment, the support structure 108 comprises one or more x-ray shielding agents. In an embodiment, the support structure 108 comprises one or more x-ray radio-opaque materials. In an embodiment, the support structure 108 comprises one or more x-ray attenuating materials. In an embodiment, the support structure 108 comprises one or more x-ray attenuating ceramic materials. Referring to FIG. 3, in an embodiment, the dynamic x-ray shielding device 102 includes at least a first layer 202 including one on more flow paths in fluid communication with the x-ray shielding fluid reservoir assembly 112 and configured to receive a first x-ray shielding fluid composition. Flow paths can take a variety of shapes, configurations, and geometric forms including regular or irregular forms and can have a cross-section of substantially any shape including, among others, circular, triangular, square, rectangular, polygonal, regular or irregular shapes, or the like, as well as other symmetrical and asymmetrical shapes, or combinations thereof. In an embodiment, the flow paths includes one or more interstitial spaces configured to receive the x-ray shielding fluid composition, and to provide the circulation network for the x-ray shielding fluid composition. In an embodiment, the first flow path includes a first flow valve assembly 108a selectively actuatable between an open state which permits fluid flow through the first flow valve assembly 108a such that the first x-ray shielding fluid composition flows from the x-ray shielding fluid reservoir assembly 112 along at least a portion of the first flow path, and a restrict state which restricts fluid flow through the first flow valve assembly 108a and along the first flow path. In an embodiment, the dynamic x-ray shielding device 102 includes a second layer 206 including a second flow path in fluid communication with the x-ray shielding fluid reservoir assembly 112 and configured to receive the second x-ray shielding fluid composition, the second flow path including a second flow valve assembly 118b selectively actuatable between an open state which permits fluid flow through the second flow valve assembly 118b such that the second x-ray shielding fluid composition flows from the x-ray shielding fluid reservoir assembly 112 along at least a portion of the first flow path, and a restrict state which restricts fluid flow through the second flow valve assembly 118b. In an embodiment, the dynamic x-ray shielding device 102 includes a third layer 210 including a third flow path in fluid communication with the x-ray shielding fluid reservoir assembly 112 and configured to receive the third x-ray shielding fluid composition, the third flow path including a third flow valve assembly selectively actuatable between an open state which permits fluid flow through the third flow valve assembly such that the third x-ray shielding fluid composition flows from the x-ray shielding fluid reservoir assembly 112 along at least a portion of the first flow path, and a restrict state which restricts fluid flow through the third flow valve assembly. In an embodiment, at least one of the first flow path or the second flow path includes one or more tubular structures. In an embodiment, at least one of the first flow path or the second flow path includes one or more recirculation tubular structures in fluid communication with the x-ray shielding fluid reservoir assembly 112 and operable to distribute at least one of the first x-ray shielding fluid composition or the second x-ray shielding fluid composition through at least a portion of the first flow path or the second flow path. In an embodiment, at least one of the first layer 202 or the second layer 206 comprises one or more x-ray shielding agents. In an embodiment, at least one of the first layer 202 or the second layer 206 comprises one or more x-ray radio-opaque materials. In an embodiment, at least one of the first layer 202 or the second layer 206 comprises one or more x-ray attenuating materials. In an embodiment, at least one of the first layer 202 or the second layer 206 comprises one or more x-ray attenuating ceramic materials. In an embodiment, the dynamic x-ray shielding system 100 includes one or more x-ray shielding fluid reservoirs 114 configured to store and supply at least a first x-ray shielding fluid composition and a second x-ray shielding fluid composition. In an embodiment, the dynamic x-ray shielding device 102 includes at least one x-ray shielding fluid reservoir assembly 112 including one or more x-ray shielding fluid reservoirs 114. In an embodiment, the x-ray shielding fluid reservoir assembly 112 is structured and arranged to hold the x-ray shielding fluid composition and to selectively enable fluid communication between one or more x-ray shielding fluid reservoirs and the plurality of interconnected interstitial spaces 110. In an embodiment, the dynamic x-ray shielding garment 104 includes an x-ray shielding fluid supply controller 120 that is operable to manage fluid flow of the x-ray shielding fluid composition to or from the x-ray shielding agent reservoir assembly 112, and along one or more of the plurality of interconnected interstitial space 110. In an embodiment, the one or more x-ray shielding fluid reservoirs 114 include at least a first x-ray shielding fluid composition and a second x-ray shielding fluid composition. In an embodiment, the second x-ray shielding fluid composition comprises one or more x-ray shielding agents different from those of the first x-ray shielding fluid composition. In an embodiment, the second x-ray shielding fluid composition comprises one or more x-ray shielding agents having one or more absorption edges different from those of the first x-ray shielding fluid composition. In an embodiment, the second x-ray shielding fluid composition comprises one or more x-ray shielding agents having one or more characteristic x-ray absorption edges different from those of the first x-ray shielding fluid composition. In an embodiment, the one or more x-ray shielding fluid reservoirs 114 include at least a first x-ray shielding fluid composition and a second x-ray shielding fluid composition, the second x-ray shielding fluid composition comprises one or more x-ray shielding agents having one or more k-edges, or one or more l-edges, different from those of the first x-ray shielding fluid composition. In an embodiment, the second x-ray shielding fluid composition comprises one or more x-ray shielding agents having one or more x-ray mass attenuation coefficients different from those of the first x-ray shielding fluid composition. In an embodiment, the second x-ray shielding fluid composition comprises one or more x-ray shielding agents having at least one k-edge having an energy level lower than at least one k-edge of the first x-ray shielding fluid composition. In an embodiment, the second x-ray shielding fluid composition comprises one or more x-ray shielding agents different from those of the second x-ray shielding fluid composition and the first x-ray shielding fluid composition. In an embodiment, the one or more x-ray shielding fluid reservoirs 114 include an x-ray shielding fluid composition having a plurality of x-ray shielding particles, each including one or more x-ray shielding agents, and a carrier fluid. In an embodiment, the plurality of x-ray shielding particles includes one or more x-ray radio-opaque materials. In an embodiment, the plurality of x-ray shielding particles includes one or more x-ray attenuating materials. In an embodiment, the plurality of x-ray shielding particles includes one or more x-ray attenuating ceramic materials. In an embodiment, the plurality of x-ray shielding particles includes one or more x-ray absorbers. In an embodiment, the plurality of x-ray shielding particles include one or more x-ray scattering materials. 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 one or more SiO2—PbO-alkali metal oxide glasses, CaO—SrO—B2O3 glasses, or boron-lithium glasses. 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, at least one of the first x-ray shielding agent or the second x-ray shielding agent includes 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 lead (Pb), lithium fluoride (LiF), 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 teflon (C2F4). In an embodiment, at least one of the first x-ray shielding agent or the second x-ray shielding agent includes lead (II) oxide (PbO). In an embodiment, the carrier fluid comprises about 1 to about 98 volume percent of the total volume of the x-ray shielding fluid composition. In an embodiment, the one or more x-ray shielding fluid reservoirs 114 include an x-ray shielding fluid composition having 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, and a carrier fluid. In an embodiment, the second x-ray shielding agent includes one or more characteristic x-ray absorption edges different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes one or more k-edges, or one or more l-edges, different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes an x-ray mass attenuation coefficient different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes at least one k-edge having an energy level lower than at least one k-edge of the first x-ray shielding agent. In an embodiment, the one or more x-ray shielding fluid reservoirs 114 include an x-ray shielding fluid composition having a plurality of x-ray shielding particles having at least a third x-ray shielding agent, the third x-ray shielding agent having one or more absorption edges different from the second x-ray shielding agent and the first x-ray shielding agent. In an embodiment, the one or more x-ray shielding fluid reservoirs 114 include an x-ray shielding fluid composition having a plurality of x-ray shielding particles having at least a fourth x-ray shielding agent, the fourth x-ray shielding agent having one or more absorption edges different from the third x-ray shielding agent, the second x-ray shielding agent, and the first x-ray shielding agent. In an embodiment, the one or more x-ray shielding fluid reservoirs 114 include an x-ray shielding fluid composition having a plurality of x-ray shielding particles having at least a fifth x-ray shielding agent, the fifth x-ray shielding agent having one or more absorption edges different from the fourth x-ray shielding agent, the third x-ray shielding agent, the second x-ray shielding agent, and the first x-ray shielding agent. In an embodiment, the one or more x-ray shielding fluid reservoirs 114 include an x-ray shielding fluid composition 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, and a carrier fluid. In an embodiment, the second x-ray shielding agent includes one or more characteristic x-ray absorption edges different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes one or more k-edges, or one or more l-edges, different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes an x-ray mass attenuation coefficient different from the first x-ray shielding agent. In an embodiment, the second x-ray shielding agent includes at least one k-edge having an energy level lower than at least one k-edge of the first 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), lithium fluoride (LiF), 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 teflon (C2F4). In an embodiment, the one or more x-ray shielding fluid reservoirs 114 include an x-ray shielding fluid composition having a third x-ray shielding agent, the third x-ray shielding agent having one or more absorption edges different from the second x-ray shielding agent and the first x-ray shielding agent. In an embodiment, the one or more x-ray shielding fluid reservoirs 114 include an x-ray shielding fluid composition having a fourth x-ray shielding agent, the fourth x-ray shielding agent having one or more absorption edges different from the third x-ray shielding, the second x-ray shielding agent, and the first x-ray shielding agent. In an embodiment, the one or more x-ray shielding fluid reservoirs 114 include an x-ray shielding fluid composition having a fifth x-ray shielding agent, the fifth x-ray shielding agent having one or more absorption edges different from the fourth x-ray shielding agent, the third x-ray shielding, the second x-ray shielding agent, and the first x-ray shielding agent. In an embodiment, the dynamic x-ray shielding system 100 includes an x-ray shielding fluid supply controller 120 associated with one or more flow valve assemblies 116 and configured to selectively actuate the one or more flow valve assemblies 118 to regulate fluid flow of a defined quantity of x-ray shielding fluid composition from one or more reservoirs 114, through the one or more flow valve assemblies 118, into the at least a portion of the circulation network. For example, in an embodiment, the dynamic x-ray shielding system 100 includes an x-ray shielding fluid supply controller 120 associated with at least the first flow valve assembly 108a and the second flow valve assembly 118b and configured to selectively actuate the first or the second flow valve assembly 118b to regulate fluid flow of a defined quantity of at least one of the first x-ray shielding fluid composition or the second x-ray shielding fluid composition from the reservoir, through at least one of the first flow valve or the second flow valve, into the at least a portion of the first flow path or the second flow path. In an embodiment, the x-ray shielding fluid supply controller 120 includes, among other things, one or more computing devices 122 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. For example, in an embodiment, the x-ray shielding fluid supply controller 120 includes one or more computing devices 122 operably couple to at least one of an x-ray shielding fluid composition pump assembly 116 or a flow valve assembly 118 and configured to actuate at least one of the x-ray shielding fluid composition pump assembly 116 or the flow valve assembly 118. In an embodiment, the x-ray shielding fluid supply controller 120 includes one or more computing devices 122 operably couple to at least one flow valve assembly 118 and is configured to actuate the flow valve assembly 118 between an open state which permits fluid flow through the flow valve assembly 118 such that an x-ray shielding fluid composition flows from the x-ray shielding fluid reservoir assembly 112 along at least a portion of a flow path, and a restrict state which restricts fluid flow through the flow valve assembly 118. In an embodiment, the x-ray shielding fluid supply controller 120 includes discrete digital or analog circuit elements or electronics, or combinations thereof. In an embodiment, the x-ray shielding fluid supply controller 120 includes one or more ASICs having a plurality of predefined logic components. In an embodiment, the x-ray shielding fluid supply controller 120 includes one or more FPGA having a plurality of programmable logic components. In an embodiment, the x-ray shielding fluid supply controller 120 includes 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, the x-ray shielding fluid supply controller 120 includes one or more remotely located components. In an embodiment, remotely located components are operably coupled via wireless communication. In an embodiment, remotely located components are operably coupled via one or more receivers 182, transceivers 184, or transmitters 186, or the like. In an embodiment, the x-ray shielding fluid supply controller 120 includes one or more memory devices 124 that, for example, store flow control instructions or data. Non-limiting examples of one or more memory devices 124 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 one or more memory devices 124 include Erasable Programmable Read-Only Memory (EPROM), flash memory, or the like. The one or more memory devices 124 can be coupled to, for example, one or more computing devices 122 by one or more instructions, data, or power buses. In an embodiment, the x-ray shielding fluid supply controller 120 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, the x-ray shielding fluid supply controller 120 includes one or more user input/output components that are operably coupled to at least one computing device 122 to control (electrical, electromechanical, software-implemented, firmware-implemented, or other control, or combinations thereof) at least one parameter associated with, for example, determining an exposure status of a user in response to one or more transcutaneously received x-ray radiation stimuli obtained via the implantable radiation sensing device 102. In an embodiment, the x-ray shielding fluid supply controller 120 includes a computer-readable media drive or memory slot 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 and/or an analog communication medium (e.g., a fiber optic cable, a waveguide, etc.), a wired communications link, a wireless communication link (e.g., receiver 182, transceiver 184, transmitter 186, 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 shielding fluid supply controller 120 includes circuitry having one or more modules optionally operable for communication with one or more input/output components that are configured to relay user output and/or input. In an embodiment, a module includes one or more instances of electrical, electromechanical, software-implemented, firmware-implemented, or other control devices. Such devices include one or more instances of memory 120, computing devices 122, antennas, power or other supplies, logic modules or other signaling modules, gauges or other such active or passive detection components, piezoelectric transducers, shape memory elements, micro-electro-mechanical system (MEMS) elements, or other actuators. In an embodiment, the dynamic x-ray shielding system 100 includes an x-ray shielding fluid supply controller 120 associated with at least the first flow valve assembly 108a and the second flow valve assembly 118b and configured to selectively actuate the first or the second flow valve assembly 118b to regulate fluid flow of a defined quantity of at least one of the first x-ray shielding fluid composition or the second x-ray shielding fluid composition from the reservoir, through at least one of the first flow valve or the second flow valve, into the at least a portion of the first flow path or the second flow path. In an embodiment, the x-ray shielding fluid supply controller 120 is operable to actuate fluid flow of the first x-ray shielding fluid composition or the second x-ray shielding fluid, received in the x-ray shielding fluid reservoir assembly 112, to or from the x-ray shielding agent reservoir and along respectively one of the first flow path or the second flow path. In an embodiment, the x-ray shielding fluid supply controller 120 is operable to actuate concurrent or sequential fluid flow of the first x-ray shielding fluid composition or the second x-ray shielding fluid, received in the x-ray shielding fluid reservoir assembly 112, to or from the x-ray shielding agent reservoir and along respectively one of the first flow path or the second flow path. In an embodiment, then x-ray shielding fluid supply controller 120 includes control logic 149 arranged to determine an actuate flow condition and to actuate the flow of the first x-ray shielding fluid composition or the second x-ray shielding fluid, received in the x-ray shielding fluid reservoir assembly 112, to or from the x-ray shielding agent reservoir and along respectively one of the first flow path or the second flow path, responsive to the actuate flow condition. In an embodiment, then x-ray shielding fluid supply controller 120 includes control logic 149 arranged to determine an actuate flow condition and to actuate the flow of the first x-ray shielding fluid composition or the second x-ray shielding fluid, received in the x-ray shielding fluid reservoir assembly 112, to or from the x-ray shielding agent reservoir and along respectively one of the first flow path or the second flow path, responsive to at least one of an authorization protocol, an authentication protocol, or an activation protocol. In an embodiment, the x-ray shielding fluid supply controller 120 includes a speech recognition module 123 that causes the x-ray shielding fluid supply controller 120 to modulate the flow of the first x-ray shielding fluid composition or the second x-ray shielding fluid, received in the x-ray shielding fluid reservoir assembly 112, to or from the x-ray shielding agent reservoir 114 and along respective one of the first flow path or the second flow path 210, responsive to one or more audio inputs. In an embodiment, the dynamic x-ray shielding system 100 includes a power source 150 including at least one of a thermoelectric generator 152, a piezoelectric generator 154, a microelectromechanical system generator 156, or a biomechanical-energy harvesting generator 158. In an embodiment, the dynamic x-ray shielding system 100 includes a power source 150 electromagnetically, magnetically, ultrasonically, optically, inductively, electrically, or capacitively coupled to the x-ray shielding fluid supply controller 120. In an embodiment, the dynamic x-ray shielding system 100 includes an energy transfer system 160 electromagnetically, magnetically, ultrasonically, optically, inductively, electrically, or capacitively coupled to the x-ray shielding fluid supply controller 120. In an embodiment, the dynamic x-ray shielding system 100 includes one or more x-ray radiation sensor devices 170. In an embodiment, the one or more x-radiation sensing devices 170 are operable to detect (e.g., assess, calculate, evaluate, determine, gauge, measure, monitor, quantify, resolve, sense, or the like) an incident x-ray radiation. In an embodiment, during operation, the x-ray radiation sensor devices 170 detects at least one of an actual or a potential exposure event and alerts the dynamic x-ray shielding devices 102, or the x-ray shielding fluid supply controller 120, to check whether the dynamic x-ray shielding devices 102 is activated or functional to shield or protect the user. In an embodiment, during operation, the x-ray radiation sensor devices 170 detects at least one of an actual or a potential exposure event and alerts the dynamic x-ray shielding devices 102, or the x-ray shielding fluid supply controller 120, to activate the flow of the x-ray shielding fluid composition to or from the one or more x-ray shielding fluid reservoirs and along one or more of the plurality of interconnected interstitial spaces. In an embodiment, the dynamic x-ray shielding devices 102 includes one or more an x-ray radiation sensor devices 170 operably coupled to the x-ray shielding fluid supply controller 120. In an embodiment, the radiation sensing device 170 is operable to detect at least one characteristic (e.g., a fundamental characteristic, a spectral characteristic, a spectral signature, a physical quantity, an absorption coefficient, or the like) associated with an x-ray radiation exposure event. In an embodiment, the dynamic x-ray shielding device 102 includes one or more x-ray radiation sensor devices 170 disposed on a user-side of the first layer that acquire at least a portion of penetrating x-ray radiation stimulus and transduce the penetrating x-ray radiation stimulus acquired by the x-ray radiation sensor device 170 into at least one measurand indicative of an x-ray flux throughput during an integration period of the one or more x-ray radiation sensor devices 170. Non-limiting examples of x-ray radiation sensor devices 170 include scintillators 172 (e.g., inorganic scintillators, thallium doped cesium iodide scintillators, scintillator-photodiode pairs, scintillation detection devices, etc.), dosimeters 174 (e.g., x-ray dosimeters, thermoluminescent dosimeters, etc.), optically stimulated luminescence detectors, photodiode arrays, charge-coupled devices (CCDs) 176, complementary metal-oxide-semiconductor (CMOS) devices 178, or the like. In an embodiment, the x-ray radiation sensor device 170 includes one or more x-ray radiation fluoroscopic elements. In an embodiment, the x-ray radiation sensor device 170 includes one or more phosphorus doped elements (e.g., ZnCdS:Ag phosphorus doped elements). In an embodiment, the x-ray radiation sensor device includes one or more amorphous silicon thin-film transistor arrays. In an embodiment, the x-ray radiation sensor device includes one or more phosphors. In an embodiment, the x-ray radiation sensor device 170 includes one or more transducers 175 that detect and convert x-rays into electronic signals. For example, in an embodiment, the x-ray radiation sensor device 170 includes one or more x-ray radiation scintillation crystals. In an embodiment, the x-ray radiation sensor device 170 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 x-ray radiation sensor device's 170 computing device 122 processes the electronic signals generated by the one or more transducers 175 to determine one or more of intensity, energy, time of exposure, date of exposure, exposure duration, rate of energy deposition, depth of energy deposition, or 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 x-ray radiation sensor device 170, which results in the generation of a current indicative of, for example, the energy of the incident x-ray radiation. In an embodiment, the radiation sensing device 170 includes circuitry 173 configured to, for example, detect x-ray radiation, determine exposure information based on one or more measurands, or the like. For example, in an embodiment, the x-ray radiation sensor device 170 includes at least one computing device 122 operably coupled to one or more sensors 171 that measure at least one of intensity data, energy, exposure time, rate of energy deposition, or depth of energy deposition associated with an x-ray radiation stimulus. In an embodiment, the x-ray radiation sensor device 170 includes at least one of a photodiode array, a scintillator, a thermoluminescent dosimeter, an x-ray radiation fluoroscopic element, or an amorphous silicon thin-film transistor array (e.g., amorphous silicon, thin-film transistor, active matrix array, etc.) operably coupled to at least one computing device 122. In an embodiment, at least one of the x-ray radiation sensor devices 170 is configured to detect an x-ray radiation stimulus associated with an x-ray radiation-emitting system 146 (e.g., a medical systems, a cabinet x-ray system, closed x-ray systems, x-ray inspection systems, x-ray screening systems, x-ray security systems, baggage x-ray systems, etc.) and to generate at least one measurand indicative of an x-ray radiation exposure event during an integration period of the x-ray radiation sensor device 170. For example, during operation, in an embodiment, the x-ray radiation sensor devices 170 associated with a dynamic x-ray shielding device 102 alerts the dynamic x-ray shielding device 102 of the actual or prospective x-ray exposure event. In response, in an embodiment, a dynamic x-ray shielding device 102 (via one or more x-ray shielding fluid supply controller 120) activates the flow of an x-ray shielding fluid composition to one or more region of dynamic x-ray shielding device 102 to provide x-ray shielding and protection. In an embodiment, the x-ray radiation sensor device 170 includes one or more pixels that acquire at least a portion of an x-ray radiation stimulus and transduces the x-ray radiation stimulus acquired by the x-ray radiation sensor device 170 into at least one measurand indicative of an x-ray radiation exposure during an integration period of the x-ray radiation sensor device 170. In an embodiment, the x-ray radiation sensor device 170 includes at least one charge-coupled device 176, complementary metal-oxide-semiconductor device 178, or a scintillation detection device. In an embodiment, the x-ray radiation sensor device 170 includes at least one of a photodiode array, a scintillator 172, a thermoluminescent dosimeter, an x-ray radiation fluoroscopic element, or an amorphous silicon thin-film transistor array. In an embodiment, the x-ray radiation sensor device 170 includes at least one computing device 122 operably coupled to one or more sensors 171 configured to acquire at least one of intensity data, x-ray energy, exposure time, rate of energy deposition, or depth of energy deposition associated with the x-ray radiation stimulus. In an embodiment, the dynamic x-ray shielding system 100 includes an x-ray radiation sensor device 170 operable to detect at least one x-ray radiation exposure event. In an embodiment, the dynamic x-ray shielding system 100 an x-ray radiation sensor device 170 operable to determine an x-ray shielding status of the dynamic x-ray shielding device 102 by detecting the presence or absence of x-ray shielding fluid composition within one or more regions of the dynamic x-ray shielding device 102. In an embodiment, the x-ray shielding fluid supply controller 120 actuates at least one of a pump assembly 116 or a flow valve assembly 118 to actuate fluid flow of an x-ray shielding fluid composition, received in the one or more x-ray shielding fluid reservoirs 114, to or from the one or more x-ray shielding fluid reservoirs 114 and along one or more of the plurality of interconnected interstitial spaces 110 responsive to an output from the x-ray radiation sensor device 170 indicative of the x-ray radiation exposure event, a lack of x-ray shielding fluid composition in a region of the dynamic x-ray shielding device 102, the incorrect shield agent, or the like. FIG. 5 shows a dynamic x-ray shielding garment 104 in which one or more methodologies or technologies can be implemented such as, for example, detecting an x-ray radiation stimulus, providing x-ray shielding, providing x-ray radiation protection, or the like. In an embodiment, the dynamic x-ray shielding garment 104 includes an x-ray shielding fluid reservoir assembly 112 including a plurality of reservoirs 114 configured to store and supply at least a first x-ray shielding fluid composition and a second x-ray shielding fluid composition. In an embodiment, a dynamic x-ray shielding garment 104 includes at least a first layer 202 including a first flow path in fluid communication with the x-ray shielding fluid reservoir assembly 112 and configured to receive the first x-ray shielding fluid composition. In an embodiment, the first flow path includes first flow valve assembly 118a selectively actuatable between an open state which permits fluid flow through the first flow valve assembly 118a such that the first x-ray shielding fluid composition flows from the x-ray shielding fluid reservoir assembly along at least a portion of the first flow path, and a restrict state which restricts fluid flow through the first flow valve assembly 118a. In an embodiment, the first layer 202 includes an x-ray source side and a user protection side, and wherein the x-ray radiation sensor device 170 is located on the x-ray source of the first layer 202 so as to determine an incident x-ray flux. In an embodiment, the first layer 202 includes an x-ray source side and a user protection side. In an embodiment, the x-ray radiation sensor device 170 is located on the user protection side so as to determine an x-ray flux through the dynamic x-ray shielding garment 104. In an embodiment, a dynamic x-ray shielding garment 104 includes a second layer 206 including a second flow path in fluid communication with the x-ray shielding fluid reservoir assembly 112 and configured to receive the second x-ray shielding fluid composition, the second flow path including a second flow valve assembly 118b selectively actuatable between an open state which permits fluid flow through the second flow valve assembly 118b such that the second x-ray shielding fluid composition flows from the x-ray shielding fluid reservoir assembly 112 along at least a portion of the first flow path, and a restrict state which restricts fluid flow through the second flow valve assembly 118b. In an embodiment, a dynamic x-ray shielding garment 104 includes one or more x-ray radiation sensor devices 170 disposed on an x-ray source-side of the first layer 202 that acquire at least a portion of an incident x-ray radiation stimulus and transduce the incident x-ray radiation stimulus acquired by the x-ray radiation sensor device 170 into at least one measurand indicative of an incident x-ray flux during an integration period of the one or more x-ray radiation sensor devices 170. In an embodiment, a dynamic x-ray shielding garment 104 includes one or more x-ray radiation sensor devices 170 disposed on an x-ray source-side of the first layer 202 that detect an incident x-ray stimulus, and one or more x-ray radiation sensor devices 170 disposed on user-side of the first layer 202 that detect a transmitted x-ray stimulus. In an embodiment, a dynamic x-ray shielding garment 104 includes at least one computing device 122 that generates one or more parameters associated with a comparison between an incident x-ray stimulus and a transmitted x-ray stimulus. In an embodiment, the dynamic x-ray shielding garment 104 includes one or more sensors 171 to determine a presence of the x-ray shielding fluid composition within one or more sites within the circulation network. In an embodiment, the dynamic x-ray shielding garment 104 includes one or more sensors 171 to determine a presence of the x-ray shielding fluid composition within one or more locations within the dynamic x-ray shielding garment. In an embodiment, the dynamic x-ray shielding garment 104 includes one or more sensors 171 to determine a presence of the x-ray shielding fluid composition within one or more of the plurality of interconnected interstitial spaces 110. In an embodiment, a dynamic x-ray shielding garment 104 includes an x-ray shielding fluid supply controller 120 includes control logic 149 arranged to determine an actuate flow condition and to actuate the flow of the x-ray shielding fluid composition to or from the x-ray shielding fluid reservoir assembly 112, and along one or more of the plurality of interconnected interstitial spaces 110, responsive to the actuate flow condition. In an embodiment, the x-ray shielding fluid supply controller 120 actuates the flow of the x-ray shielding fluid composition to or from the x-ray shielding fluid reservoir assembly 112, and along one or more of the plurality of interconnected interstitial spaces 110, responsive to at least one of an authorization protocol, an authentication protocol, or an activation protocol. In an embodiment, the x-ray shielding fluid supply controller 120 includes a speech recognition module 123 that causes the x-ray shielding fluid supply controller 120 to modulate the flow of the x-ray shielding fluid composition to or from the x-ray shielding fluid reservoir assembly 112, and along one or more of the plurality of interconnected interstitial spaces 110, responsive to one or more audio inputs. In an embodiment, during operation, the x-ray shielding fluid supply controller 120 receives an input from the speech recognition module 123 associated with a verbal command to actuate flow to the x-ray shielding fluid composition. Responsive to the input from the speech recognition module 123, the x-ray shielding fluid supply controller 120 actuates at least one pump assembly 116 or flow valve assembly 118 to initiate the supply of x-ray shielding fluid composition to or from the x-ray shielding fluid reservoir assembly 112, and along a circulation network within the dynamic x-ray shielding device 102. In an embodiment, the dynamic x-ray shielding garment 104 includes a power source 150 including at least one battery. In an embodiment, the dynamic x-ray shielding garment 104 includes a power source 150 wired, or wireless coupled, to an external source. In an embodiment, the dynamic x-ray shielding garment 104 includes a power source 150 including at least one of a thermoelectric generator, a piezoelectric generator, a microelectromechanical system generator, or a biomechanical-energy harvesting generator. In an embodiment, the dynamic x-ray shielding garment 104 includes a power source 150 electromagnetically, magnetically, ultrasonically, optically, inductively, electrically, or capacitively coupled to the x-ray shielding fluid supply controller 120. In an embodiment, the dynamic x-ray shielding garment 104 includes an energy transfer system 160 electromagnetically, magnetically, ultrasonically, optically, inductively, electrically, or capacitively coupled to the x-ray shielding fluid supply controller 120. In an embodiment, the dynamic x-ray shielding garment 104 includes a pump assembly 116 including one or more pumps 117 that circulate the x-ray shielding fluid composition within at least a portion of the circulation network (mechanical, magnetic, etc.) For example, in an embodiment, the dynamic x-ray shielding garment 104 includes an x-ray shielding fluid composition pump assembly 116 that is in fluid communication with at least one of the x-ray shielding fluid reservoir assembly 112 or the circulation network that supplies and circulates the x-ray shielding fluid composition to or from the x-ray shielding agent reservoir assembly 112, and along one or more regions within the circulation network. In an embodiment, the dynamic x-ray shielding garment 104 includes one or more pumps 117 that employ magnetic forces on magnetic components of the x-ray shielding fluid composition to circulate the x-ray shielding fluid composition to or from the x-ray shielding agent reservoir assembly 112, and along one or more regions within the circulation network. In an embodiment, the dynamic x-ray shielding garment 104 includes one or more valves 119 to selectively direct flow of the x-ray shielding fluid composition to or from the x-ray shielding agent reservoir 114. In an embodiment, the dynamic x-ray shielding garment 104 includes one or more valves 119 to selectively direct flow of the x-ray shielding fluid composition within the circulation network. In an embodiment, the dynamic x-ray shielding garment 104 includes at least a second x-ray shielding fluid reservoir assembly 112 including one or more x-ray shielding fluid reservoirs 114. In an embodiment, the dynamic x-ray shielding garment 104 includes an x-ray shielding status reporter device 180 including one or more receivers 182, transceivers 184, or transmitters 186 that generate an output indicative of at least one of an x-ray shielding fluid composition presence within one or more regions of the plurality of interconnected interstitial spaces. In an embodiment, the dynamic x-ray shielding garment 104 includes an x-ray shielding status reporter device 180 including one or more receivers 182, transceivers 184, or transmitters 186 that generate an output indicative of x-ray sensor value. In an embodiment, the dynamic x-ray shielding garment 104 includes an x-ray shielding status reporter device 180 including one or more receivers 182, transceivers 184, or transmitters 186 that generate an output indicative of an authorization to x-ray source to irradiate. In an embodiment, the dynamic x-ray shielding garment 104 includes an x-ray shielding status reporter device 180 including one or more receivers 182, transceivers 184, or transmitters 186 that generate an output indicative of authorization to x-ray source spectrum or intensity. In an embodiment, the dynamic x-ray shielding garment 104 includes an x-ray shielding status reporter device 180 including an irradiation authorization component 188 that generates one or more cryptographic keys that provide authorization to the external x-ray radiation-emitting system 146 to initiate x-ray radiation delivery. In an embodiment, the dynamic x-ray shielding garment 104 includes an x-ray shielding status reporter device 180 including an irradiation authorization component 188 that generates one or more cryptographic keys that provide authorization to the external x-ray radiation-emitting system 146 to initiate a spectrum-specific x-ray dose regimen. In an embodiment, the dynamic x-ray shielding garment 104 includes an x-ray shielding status reporter device 180 including an irradiation authorization component 188 that generates one or more cryptographic keys that provide authorization to the external x-ray radiation-emitting system 146 to initiate an intensity-specific x-ray dose regimen. In an embodiment, the dynamic x-ray shielding garment 104 includes fluid supply controller 120 having one or more computing devices 122, operably coupled to one or more pump assemblies 116 including one or more pumps 117, that manage fluid flow of an x-ray shielding fluid composition to or from the x-ray shielding agent reservoir assembly 112, and along one or more of the plurality of interconnected interstitial spaces. In an embodiment, the dynamic x-ray shielding garment 104 includes an x-ray shielding status reporter device 180 that receives x-ray potential exposure event data associated with delivery of an x-ray radiation stimulus from an x-ray radiation-emitting system 146. In an embodiment, the x-ray shielding status reporter device 180 is operably coupled to one or more x-ray shielding fluid supply controllers 120 that direct fluid flow of an x-ray shielding fluid composition received in an x-ray shielding fluid reservoir assembly associated with a dynamic x-ray shielding garment, to or from the x-ray shielding agent reservoir, and along one or more of a plurality of interconnected interstitial spaces within the dynamic x-ray shielding garment 104, responsive to an output signal from the x-ray shielding status reporter device 180. In an embodiment, the dynamic x-ray shielding garment 104 includes fluid supply controller 120 is configured to manage fluid flow of a gravity-fed x-ray shielding fluid composition to or from the x-ray shielding agent reservoir assembly 112, and along one or more of the plurality of interconnected interstitial spaces. In an embodiment, the dynamic x-ray shielding garment 104 includes fluid supply controller 120 is configured to manage fluid flow of a pressure-fed x-ray shielding fluid composition to or from the x-ray shielding agent reservoir assembly 112, and along one or more of the plurality of interconnected interstitial spaces. FIG. 5 shows a dynamic x-ray shielding method 500. At 510, the dynamic x-ray shielding method 500 includes receiving x-ray potential exposure event data associated with delivery of an x-ray radiation stimulus from an x-ray radiation-emitting system 146. For example, in an embodiment, the dynamic x-ray shielding garment 104 includes an x-ray shielding status reporter device 180 having one or more receivers 182, transceivers 184, or transmitters 186 that receiving x-ray potential exposure event data associated with delivery of an x-ray radiation stimulus from an x-ray radiation-emitting system 146. At 512, receiving the potential x-ray exposure event data includes initiating a data transmission transfer between a dynamic x-ray shielding device and an x-ray radiation-emitting system 146. At 514, receiving the potential x-ray exposure event data includes initiating a data transmission transfer between a dynamic x-ray shielding device and an x-ray radiation-emitting system 146 based on the identification of the x-ray radiation sensing device 170. At 516, receiving the potential x-ray exposure event data includes telemetrically receiving, via one or more receivers 182, transceivers 184, or transmitters 186, proposed dose data, time to exposure data, time to exposure data, or duration of exposure data. At 518, receiving the potential x-ray exposure event data includes wirelessly receiving at least one of radiation intensity data, radiation energy data, radiation exposure time data, rate of radiation energy deposition, depth of radiation energy deposition data, absorbed dose data, absorbed dose rate data, committed effective dose data, cumulative dose data, effective dose data, equivalent dose data, or exposure data associated with the potential x-ray exposure event. At 520, the dynamic x-ray shielding method 500 includes directing fluid flow of an x-ray shielding fluid composition received in an x-ray shielding fluid reservoir assembly 112 associated with a dynamic x-ray shielding garment, to or from the x-ray shielding agent reservoir, and along one or more of a plurality of interconnected interstitial spaces 110 within the dynamic x-ray shielding garment, responsive to the x-ray potential exposure event data. For example, in an embodiment, the dynamic x-ray shielding garment includes 104 an x-ray shielding fluid supply controller 120 that is operable to directing fluid flow of an x-ray shielding fluid composition received in the x-ray shielding fluid reservoir assembly 116 associated with the dynamic x-ray shielding garment 104, to or from the one or more x-ray shielding agent reservoirs 117, and along one or more of a plurality of interconnected interstitial spaces 110 within the dynamic x-ray shielding garment, responsive to the x-ray potential exposure event data. At 522, directing the fluid flow of the x-ray shielding fluid composition includes directing a flow sufficient of the x-ray shielding fluid composition to modulate at least one of a penetration depth, intensity, or energy associated with the x-ray radiation stimulus. At 524, directing the fluid flow of the x-ray shielding fluid composition includes directing a flow sufficient of the x-ray shielding fluid composition to cause at least a portion of the dynamic x-ray shielding garment to have an x-ray shielding lead equivalence of about 0.25 millimeters to about 0.5 millimeters. At 526, directing the fluid flow of the x-ray shielding fluid composition includes directing a flow sufficient of the x-ray shielding fluid composition to cause at least a portion of the dynamic x-ray shielding garment to have an x-ray shielding lead equivalence of greater than about 0.25 millimeters. FIG. 6 shows an x-ray shielding method 600. At 610, the x-ray shielding method 600 includes actuating fluid flow of an x-ray shielding fluid composition received in one or more x-ray shielding fluid reservoirs associated with a dynamic x-ray shielding garment, to or from the x-ray shielding agent reservoir, and along one or more of a plurality of interconnected interstitial spaces 110 within the dynamic x-ray shielding garment responsive to a determination that an x-ray radiation-emitting system 146 is in operation. At 620, the x-ray shielding method 600 includes actuating fluid flow of an x-ray shielding fluid composition received in one or more x-ray shielding fluid reservoirs associated with a dynamic x-ray shielding garment, to or from the x-ray shielding agent reservoir, and along one or more of a plurality of interconnected interstitial spaces 110 within the dynamic x-ray shielding garment responsive to an input associated with a potential delivery of an x-ray radiation stimulus from an x-ray radiation-emitting system 146. At 630, the x-ray shielding method 600 includes receiving x-ray potential exposure event data associated with delivery of an x-ray radiation stimulus from an x-ray radiation-emitting system 146. At 640, the x-ray shielding method 600 includes concurrent or sequential actuating fluid flow of a first x-ray shielding fluid composition or the second x-ray shielding fluid, received in an x-ray shielding fluid reservoir assembly 112, to or from the x-ray shielding agent reservoir and along respectively one of a first flow path 204 or a second flow path 210 of a dynamic x-ray shielding apparatus, responsive to potential exposure event data indicative of an x-ray potential exposure event. FIG. 7 shows a dynamic x-ray shielding method 700. At 710, the dynamic x-ray shielding method 700 includes determining an actuate flow condition. At 720, the dynamic x-ray shielding method 700 includes concurrent or sequential actuating fluid flow of a first x-ray shielding fluid composition or the second x-ray shielding fluid, received in a plurality of x-ray shielding fluid reservoirs, to or from the plurality of x-ray shielding fluid reservoirs and along respectively one of a first flow path 204 or a second flow path 210 of a dynamic x-ray shielding apparatus, responsive to the actuate flow condition. At least a portion of the devices and/or processes described herein can be integrated into a data processing system. A data 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.), and/or control systems including feedback loops and control motors (e.g., feedback for detecting position and/or velocity, control motors for moving and/or adjusting components and/or quantities). A data processing system can be implemented utilizing suitable commercially available components, such as those typically found in data computing/communication and/or network computing/communication systems. Those having skill in the art will recognize that 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. Those having skill in the art will appreciate that there are various vehicles by which processes and/or systems and/or other technologies described herein can be effected (e.g., hardware, software, and/or firmware in one or more machines or articles of manufacture), and that the preferred vehicle will vary with the context in which the processes and/or systems and/or other technologies are deployed. For example, if an implementer determines that speed and accuracy are paramount, the implementer may opt for a mainly hardware and/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, and/or firmware in one or more machines or articles of manufacture. Hence, there are several possible vehicles by which the processes and/or devices and/or other technologies 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. Those skilled in the art will recognize that optical aspects of implementations will typically employ optically-oriented hardware, software, and or firmware 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 and/or physically interacting components, and/or wirelessly interactable, and/or wirelessly interacting components, and/or logically interacting, and/or logically interactable components. 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 and/or inactive-state components and/or standby-state components, unless context requires otherwise. The foregoing detailed description has set forth various embodiments of the devices and/or processes via the use of block diagrams, flowcharts, and/or examples. Insofar as such block diagrams, flowcharts, and/or examples contain one or more functions and/or operations, it will be understood by the reader that each function and/or operation within such block diagrams, flowcharts, or examples can be implemented, individually and/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 and/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 and/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 and/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.
047626690
abstract
In a nuclear reactor, the core is composed of fuel assemblies disposed in side-by-side spaced relationships with an outer group thereof defining the periphery of the core and an inner group thereof positioned inwardly of the outer group. A baffle structure extends about the reactor core adjacent the fuel assemblies in the outer group. Any jetting of coolant fluid through the baffle structure will impinge upon fuel rods in the outer group of fuel assemblies so as to cause vibration of the fuel rods. To prevent such vibration, a plurality of annular anti-vibration grids are axially spaced along and connected to guide thimbles of the fuel assemblies in the outer group thereof between at least some of the support grids of such fuel assemblies. The annular grids are separate from and unconnected to the support grids. Each annular grid defines a plurality of cells being less in number than the multiplicity of fuel rods of each fuel assembly in the outer group but at least equal in number to the plurality of the fuel rods positioned about the periphery of each such fuel assembly. The cells receive respective ones of the peripheral fuel rods therethrough and engage them so as to dampen vibration thereof due to impingement by coolant fluid jetting from the baffle structure.