Patent Publication Number: US-2016243591-A1

Title: Radiation measuring and sorting device and radiation measuring and sorting method

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a radiation measuring and sorting device and to a radiation measuring and sorting method. Additionally, in greater detail, the present invention relates to a sorting device and a sorting method that provide a transporting mechanism for transporting an introduced target object in a fixed transportation direction, a measuring device for measuring the radiation of the target object being transported by the transporting mechanism, a sorting mechanism for sorting the target object disposed at a downstream end of the transporting mechanism based on the measurement result of the measuring device, and a control unit for controlling the operation of a transporting belt of the transporting mechanism and a sorting belt of the sorting mechanism. 
     2. Background 
     Conventionally, a conveyor type sorting device, like, for example, that described in Non-patent Document 1, is known as a radiation measuring and sorting device like that described above. However, sorting performance based on levels of radioactivity is inadequate. 
     DOCUMENTS OF THE RELATED ART 
     Non-Patent Documents 
     ISO Pacific Nuclear Assay Systems, “S3 System Technical Document (ISO PACIFIC TECHNICAL,” (US), 2009 
     SUMMARY 
     Problem to be Solved by the Invention 
     In view of the conventional conditions, an object of the present invention is to provide a radiation measuring and sorting device and a radiation measuring and sorting method having high sorting performance. 
     Means for Solving the Problem 
     In order to achieve the object described above, the radiation measuring and sorting device according to the present invention is characterized by a configuration providing a transporting mechanism for transporting an introduced target object in a fixed transportation direction, a measuring device for measuring the radiation of the target object being transported by the transporting mechanism, a sorting mechanism for sorting the target object disposed at a downstream end of the transporting mechanism based on the measurement result of the measuring device, and a control unit for controlling the operation of a transporting belt of the transporting mechanism and a sorting belt of the sorting mechanism, where the sorting mechanism is disposed so that an operating direction of the sorting belt intersects an operating direction of the transporting belt and is capable of forward and reverse rotation, and, when the measurement result changes, the control unit stops the transporting belt after a specific time period has passed, discharges the target object on the sorting belt to the outside, releases the stopping of the transporting belt, and causes the sorting belt to rotate in reverse. 
     According to the configuration described above, the sorting mechanism is disposed so that the operating direction of the sorting belt thereof intersects the operating direction of the transporting belt, and thus not only does the target object transported by the transporting belt drop onto the sorting belt, the device configuration is simple. Furthermore, the sorting belt is capable of forward and reverse rotation, and thus the target object is efficiently sorted in the operating direction of the sorting belt by a simple control. Moreover, when the measurement result changes, the control unit stops the transporting belt after a specific time period has passed, discharges the target object on the sorting belt to the outside, releases the stopping of the transporting belt, and causes the sorting belt to rotate in reverse. By this, a target object that has passed the measuring device is made to wait just before moving to the sorting belt, and, during this time, a target object on the sorting belt can be discharged so that a target object with a different measurement result does not become mixed onto the sorting belt. Additionally, after the target object on the sorting belt has been discharged, the stopping of the transporting belt is released and the sorting belt is rotated in reverse, and thus the target object can be separated (sorted) based on the measurement result. In this way, because sorting accuracy is extremely high and is activated when the measurement result changes, sorting efficiency is also good. 
     When the measurement result exceeds a reference value, it is advisable that the control unit stop the transporting belt at a time that is a first stopping time before an arrival time at which a portion of the target object corresponding to the measurement result will arrive at the downstream end of the transporting belt. Because the transporting belt is stopped at the time of the first stopping time before the arrival time, even if there is a portion where the measurement value is high locally, that portion can be prevented from being moved to the sorting belt, thus improving sorting accuracy. Furthermore, using the small amount of time before a motor, and the like, of the transporting belt completely stops, a portion of a target object that exceeds the reference value is not mixed onto the sorting belt with a portion of the target object that falls below the reference value. 
     Additionally, when the measurement result falls below the reference value, it is advisable that the control unit stop the transporting belt at a time that is a second stopping time after an arrival time at which a portion of the target object corresponding to the measurement result will arrive at the downstream end of the transporting belt. Because the transporting belt is stopped at the time of the second stopping time after the arrival time, even if there is a portion where the measurement value is high locally, that portion can be prevented from being moved to the sorting belt, thus improving sorting accuracy. Furthermore, using the small amount of time before a motor, and the like, of the transporting belt completely stops, a portion of a target object that falls below the reference value is not mixed onto the sorting belt with a portion of the target object that exceeds the reference value. 
     In this case, it is preferable that the first stopping time be at least equal to a measurement unit of time of the measuring device, and that the second stopping time is longer than the first stopping time. By making the first stopping time at least equal to the measurement unit of time of the measuring device, the mixing of target objects having different results based on measurement timing can be prevented. Furthermore, because when the measurement result falls below the reference value it means that the value just before had exceeded the reference value, by setting the second stopping time longer than a stopping time that is at least equal to the measurement time, a portion of a target object, particularly a portion that exceeds a determining standard, can be reliably separated (sorted). 
     It is advisable that the measuring device have a collimator for limiting a field of vision of the measuring device, which is based on the height of the transporting belt, which limits an energy window of the measuring device to match a specific radio nuclide in the target object. The effect of the radiation in the vicinity of the measuring device can be eliminated by the collimator, thus enhancing measuring accuracy. However, by matching the energy window to a specific radio nuclide, the effect of the energy and background data of other radio nuclides can be minimized, thus enhancing measuring accuracy and enhancing sorting accuracy. 
     In this case, it is advisable that a shielding body for blocking external radiation below the transporting belt be provided in the field of vision. By this, radiation from the ground is blocked and measuring accuracy is enhanced further. Additionally, it is advisable that a second shielding body, for blocking external radiation, be provided above the collimator. By this, the effect of radiation from above the measuring device can be eliminated, making it possible to enhance accuracy even more. 
     It is advisable that the radiation measuring and sorting device have a hopper for introducing the target object upstream of the measuring device where adjusting means for adjusting the thickness of the target object is provided on the hopper side between the hopper and the measuring device. By this, forming the thickness of the target object substantially uniformly and the surface thereof substantially flat, and then passing (transporting) the target object under the measuring device, can suppress variations in measurement results caused by the thickness and shape of the target object, which can enhance accuracy. 
     The target object is, for example, a radioactively contaminated object containing at least soil, a waste product, incineration ash, fly ash, or vegetation. 
     In order to achieve the object described above, the radiation measuring and sorting method according to the present invention is characterized by a method for transporting an introduced target object using a transporting mechanism in a fixed transportation direction, measuring the radiation of the target object being transported by the transporting mechanism, and sorting the target object disposed downstream of the transporting mechanism based on the measurement result of the measuring device, where the sorting mechanism is disposed so that an operating direction of a sorting belt of the sorting mechanism intersects an operating direction of a transporting belt of the transporting mechanism and is capable of forward and reverse rotation, and, when the measurement result changes, the transporting belt is stopped after a specific time period has passed, the target object on the sorting belt is discharged to the outside, the stopping of the transporting belt is released, and the sorting belt is caused to rotate in reverse. 
     When the measurement result exceeds a reference value, it is advisable that the transporting belt be stopped at a time that is a first stopping time before an arrival time at which a portion of the target object corresponding to the measurement result will arrive at the downstream end of the transporting belt. Additionally, when the measurement result falls below a reference value, it is advisable that the transporting belt be stopped at a time that is a second stopping time after an arrival time at which a portion of the target object corresponding to the measurement result will arrive at the downstream end of the transporting belt. In this case, it is preferable that the first stopping time be at least equal to the measurement unit of time of the measuring device, and that the second stopping time is longer than the first stopping time. 
     Effect of the Invention 
     Use of the sorting device and the sorting method according to the present invention leads to enhanced sorting performance compared to conventional devices and methods. 
     Another object of the present invention, with regard to configuration and effect, will become obvious from the matters of the following description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of the radiation measuring and sorting device according to the present invention. 
         FIG. 2  is a side view of the radiation measuring and sorting device. 
         FIG. 3  is a front view of the radiation measuring and sorting device. 
         FIG. 4  is a cross sectional view of a sorting mechanism. 
         FIG. 5  is a plan view of a transporting mechanism upstream from a measuring apparatus. 
         FIG. 6  is a cross sectional view of the transporting mechanism upstream from the measuring apparatus. 
         FIG. 7 a    is a cross sectional view along A-A (a transverse cross sectional view of an introduction hopper) of  FIG. 5 . 
         FIG. 7 b    is a cross sectional view along B-B (a longitudinal cross sectional view of the introduction hopper) of  FIG. 5 . 
         FIG. 8 a    is a plan view of a height adjusting device. 
         FIG. 8 b    is a cross sectional view along C-C (a side view of the height adjusting device). 
         FIG. 9 a    is a cross sectional view along D-D (a transverse cross sectional view of the measuring apparatus). 
         FIG. 9 b    is a cross sectional view along E-E (a longitudinal cross sectional view of the measuring apparatus). 
         FIG. 10  is the energy spectrum of a  137 Cs radiation source. 
         FIG. 11  is a drawing schematically illustrating the display contents of a monitor of a control device. 
         FIG. 12  is a diagram for describing the relationship between a column and a measurement range. 
         FIG. 13  is a diagram for describing the control of a main belt and a sorting belt, where (a) illustrates a measurement result, (b) illustrates a drive state of the main belt, and (c) illustrates a drive state of the sorting belt. 
     
    
    
     DETAILED DESCRIPTION 
     Next, the present invention will be described in greater detail while making reference to the appropriate attached drawings. A radiation measuring and sorting device  1  according to the present invention was developed to sort large quantities of radioactively contaminated objects by the radiation levels thereof based on a wide range of radioactive contamination. A radioactively contaminated object that is to be a target object  100  is, for example, soil, a waste product, incineration ash, fly ash, vegetation, and the like. For example, the state of the target object  100  may be either hard like stone, clay like, sand like, dry, or wet. The sorting device  1  is able to remove a portion that is highly radioactively contaminated from the target object  100 , and thus it is possible to reduce a radioactive air dose rate at a given location. 
     For example, the radiation measuring and sorting device  1  can be mounted on a large trailer, and the like, and transported to a location where the radioactive air dose rate is high due to radioactive contamination such as the site of a nuclear testing facility, the site of a nuclear power plant, or the like, and the radiation measuring and sorting device  1  can be activated at that location to reduce the radioactive air dose rate at that location by removing a highly radioactively contaminated portion from the target object  100 . The radiation measuring and sorting device  1  is configured to continuously measure the radioactivity of the target object  100  and to implement sorting based on the radioactivity level of the target object  100  in a continuous fashion. Therefore, if a width W of a main belt  20  for transporting is made wide, it becomes possible to process, for example, approximately 200 m 3  each hour. 
     As illustrated in  FIGS. 1 and 2 , in outline, the radiation measuring and sorting device  1  has a transporting mechanism  2  that includes a main belt  20  as a transporting belt for transporting the target object  100  in a fixed transportation direction F 1 , a measuring apparatus  4  that includes a measuring device (gauging device)  40  for measuring (gauging) the radiation of the target object  100  being transported by the main belt  20 , and a sorting mechanism  3  that includes a sorting belt  30  for sorting the target object  100 , which has been disposed at the downstream end  20   a  of the main belt  20  and measured for radiation, based on a measurement result of the measuring device  40 . An introduction hopper  6 , a height adjusting device  7 , the measuring apparatus  4 , and a power supply device  9  are disposed in the transporting mechanism  2 , in that order in the transportation direction F 1 , which is the operating direction of the main belt  20 , from an upstream end  20   b  to the downstream end  20   a  of the main belt  20 . A control device  5 , configured from a computer for example, is connected to the measuring apparatus  4  and the power supply device  9 . 
     As illustrated in  FIGS. 1 and 2 , the main belt  20  passes the target object  100  introduced from the introduction hopper  6  directly under the measuring apparatus  4 , and then transports the object to the sorting mechanism  3 . The main belt  20  is stretched between a drive pulley  22   a  and a tail pulley  22   b  by a snap pulley  22   c  and a return roller  23  within a chassis  21 . The distance between the drive pulley  22   a  and the tail pulley  22   b  is set at, for example, about  6  m. The drive pulley  22   a  is provided on the downstream end  20   a  side, and an inverter motor  24  is connected thereto. The inverter motor  24  drives the main belt  20  at a fixed rotating speed and at a fixed transporting speed in the transportation direction F 1  only. The transporting speed is set at, for example, 7.5 cm to 20 cm per second, based on the state and measuring accuracy of the target object  100 . The tail pulley  22   b  is provided on the upstream end  20   b  side, and is provided with a meander prevention mechanism  25  for keeping the main belt  20  from meandering. By these, the target object  100 , which has been molded into a fixed shape by the introduction hopper  6 , is transported along the transportation direction F 1  at a fixed speed without destroying the molded shape. Accordingly, reductions in radiation measuring accuracy can be suppressed. 
     Furthermore, a multistage scraper  26  is provided on the outside of the drive pulley  22   a  and under the measuring apparatus  4 . The scraper  26  is made of either metal or synthetic resin and has a plate like shape. The scraper  26  presses against the surface of the main belt  20  to remove the target object  100  stuck to the main belt  20 . A baffle plate  27  for dropping the transported target object  100  onto the center of the sorting belt  30  is provided on the downstream end  20   a  side of the main belt  20  through an angle adjustable attaching member  27   a.  Furthermore, the transporting portion of the main belt  20  is disposed on a plate like member  28 , which provides a backup member  28   a  made of resin on an edge thereof. Additionally, a skirt  29  is provided on an edge of the main belt  20  along the transportation direction F 1 . Note that a width W 1  of the main belt  20  can be adjusted suitably based on the number of measuring devices  40 . 
     As illustrated in  FIGS. 1 and 2 , the sorting mechanism  3  is disposed to intersect the transporting mechanism  2  directly below the downstream end  20   a  of the main belt  20 . In the present embodiment, an operating direction F 2  of the sorting belt  30  is orthogonally aligned with the transportation direction (operating direction) F 1  of the main belt  20 . As illustrated in  FIGS. 3 and 4 , the sorting belt  30  is stretched between a pair of pulleys  32   a  and  32   a  within a chassis  31  through a pair of snap pulleys  32   b  and  32   b  and a drive pulley  32   c.  The distance between the pairs of pulleys  32   a  and  32   b  is set at, for example, about 1.8 m. The drive pulley  32   c  is connected to the inverter motor  34  and is capable of forward and reverse rotation. By this, the sorting belt  30  is able to switch a driving (advancing) direction based on the measurement result of the measuring apparatus  4 , and thus distribute the target object  100  to sorting area S 1  or S 2 . In the present embodiment, the sorting area S 1  is set as a HOT side (abnormal), and the sorting area S 2  is set as a CLEAN side (normal). The speed of the sorting belt  30  is, for example, about five times the speed of the main belt  20 . 
     Furthermore, a scraper  36 , that is the same as the previous scraper  26 , is provided outside and in the vicinities of the lower portions of a pair of rollers  32   a  and  32   a.  The scraper  36  prevents the target object  100  from sticking to, or the target object  100  having a different measurement result from being introduced to, the surface of the sorting belt  30 . 
     As illustrated in  FIG. 4 , a carrier roller  38  made up of three trough rollers  37  is secured in a middle level  31   b  of the chassis  31  through a securing member  38   a.  The carrier roller  38  is in a vicinity just below the downstream end  20   a  of the main belt  20 , and the sorting belt  30  is thus maintained in the shape of a trough. By this, the target object  100  dropped from the main belt  20  is received and a transport volume is ensured. The trough angle θ of the trough roller  37  can be adjusted as appropriate, and is set at, for example, 20°. Furthermore, an inclined skirt  39  is provided along the operating direction F 2  in an upper level  31   c  of the chassis  31 . 
     As illustrated in  FIG. 5 through 7 , the introduction hopper  6  discharges the target object  100  introduced to an introduction port  61  onto the main belt  20 . The introduction port  61  is formed by an upper front wall  60   a,  an upper rear wall  60   b,  and an upper side wall  60   c.  The transportation direction F 1  length of the introduction port  61  is shorter than the length of a height direction middle part  62  of a main body part  60  interior formed by the tilted upper front wall  60   a.  Each upper wall  60   a  through c and each lower wall  60   d  through f is linked and secured to the middle part  62 . A lower part rear wall  60   e  is tilted toward the upstream side in the transportation direction F 1 . A lower side wall  60   f  is tilted toward the middle (center of the main belt  20 ) of the main body part  60 . Through the shape of this type of main body part  60 , the introduced target object  100  will move toward the forward middle part of the main body part  60  without becoming stuck in place on the wall surfaces  60   a  through f Furthermore, the target object  100  is discharged so as to be narrowed down toward the main belt  20 . 
     As illustrated in  FIGS. 7 a  and 7 b   , a skirt  65  is attached to the bottom end part of the lower side wall  60   f  through a fixture  64 . Furthermore, an inclined plate  66  is attached to the bottom end part of the lower front wall  60   d.  The skirt  65  and the inclined plate  66  form a discharge port  67  on the bottom part  63  of the main body part  60 . The discharge port  67  demonstrates a function for forming the target object  100  into a fixed shape and then feeding the object onto the main belt  20 , and thus performs the roll of a buffer for feeding the target object  100  to the main belt  20  in a continuous fashion. 
     The height H of the discharge port  67  can be adjusted by a height adjusting mechanism  68 , as illustrated in  FIG. 7 b   . The height adjusting mechanism  68  is made up of a jack  68   a  for moving a contacting part  68   b,  which abuts the main body  60 , up and down, an operating handle  68   c  for operating the jack  68   a,  a mounting shaft  68   d  attached to the lower rear wall  60   e,  and a fixed base  68   e  that is fixed to the chassis  21 . By raising and lowering, with the mounting shaft  68   d  as a height adjusting fulcrum and the contacting part  68   b  as a height adjusting leverage point  4   b,  the height H of the discharge port  67  can be adjusted to any height. In this way, the processed volume (inspected volume) per unit of time for radiation sorting varies based on the width W 1  and transporting speed of the main belt  20 , and the height of the discharge port  67 . That is, by adjusting these, the processed volume can be adjusted. 
     As has been described above, the target object  100  introduced through the introduction hopper  6  is molded into a substantially trapezoidal shape and then discharged by the walls  60   a  through f and the discharge port  67  of the main body part  60 . However, when the target object  100  is, for example, a highly viscous soil, the object can be pulled by the discharge port  67  and thus become higher than a set height H. Thus, a height adjusting device  7  for making the height of the target object  100  uniform is disposed on the downstream side of the discharge port  67 . 
     As illustrated in  FIGS. 8 a    and  b,  the height adjusting device  7  has an adjusting bar  70 , which is substantially V shaped when seen in a planar view, a plate like scraper  72  attached to the adjusting bar  70 , and a height adjusting part  73  for adjusting the height of the adjusting bar  70  in a vertical direction h. The adjusting bar  70  is secured by an end part thereof to the chassis  21  through a securing part  71  and the height adjusting part  73 , and an apex part  70   a  is disposed facing the upstream side. An uneven part  101  formed on a top surface  100   a  of the target object  100  is removed and made smooth, as illustrated in  FIG. 6 , by the shape (substantially triangular) and disposition of such an adjusting bar  70 . By smoothing the top surface  100   a,  which is to be an inspection surface, measurement variations caused by surface shape can be suppressed, and thus reductions in accuracy can be prevented. 
     The scraper plate  72  is secured to a front surface on the upstream side of the adjusting bar  70 . By this, a foreign object that is higher than a specific height H that gets mixed in with the target object  100  is moved from the apex part  70   a  toward an end part  72   a.  Therefore, the foreign object is prevented from colliding with the measuring apparatus  4  positioned downstream. Furthermore, because the apex part  70   a  of the adjusting bar  70  is aligned with the center of the main belt  20 , substantially equal tension is applied to both edges of the main belt  20  such that belt meander is also prevented. Note that any foreign object caught in the end part  72   a  is recovered as appropriate by a worker. 
     As illustrated in  FIGS. 9 a    and  b,  the measuring apparatus  4 , in outline, has a box  41  in which a plurality of measuring devices  40  are housed, a collimator  42  disposed surrounding the measuring devices  40 , a temperature adjusting part  43  for adjusting the temperature inside the box  41 , and a height adjusting part  44 . The measuring devices  40  are arranged, for example, four in a row across the collimator  42  along a direction orthogonal to the transportation direction F 1 . An energy spectrum measuring device, represented by, for example, an NaI (TI) scintillation detector, and the like, is used in the measuring device  40 . The temperature adjusting part  43  keeps the temperature inside the box  41  constant in order to suppress the impact of the temperature of the measuring device  40 . Furthermore, energy drift can be prevented by the combined use of the temperature compensation function of the measuring device  40 , and thus readjustment time can be shortened and operating efficiency improved. 
     As illustrated in  FIG. 9 b   , a plate like first shielding body  45  is provided below the main belt  20  that includes a measurement range A of the measuring device  40 . The first shielding body  45  is big enough to contain the measurement range A, and is disposed above a supporting member  46 . By this, it is possible to move the measuring device  40  close to, and thus measure, the target object  100 . Furthermore, the effect of radiation from the ground GL can be eliminated, and thus a reduction in measuring accuracy can be prevented. 
     Here, while it is feasible to use a structure of a conveyor of steel plate, and the like, as the first shielding body  45 , a 90 mm thick lead plate is used in the present embodiment to obtain an adequate shielding effect. However, due to the weight thereof, the first shielding body  45  is, for example, divided and then disposed as a plurality of pieces. In this case, it is advisable to provide the supporting member  46  with an additional shielding body in order to prevent a reduction in the shielding effect caused by seams. Furthermore, the strength of the structure and the shielding effect can be retained by stacking the added shielding body of the supporting member  46  on the seams of the first shielding body  45 . 
     The collimator  42  is a cylindrical ring like member surrounding the measuring device  40 . Being disposed around the periphery of the measuring device  40 , the collimator is, as illustrated in  FIG. 9 b   , thus able to adjust the measurement range A (field of vision) through the vertical movement of the measuring device  40 . Therefore, the measurement volume of the transported target object  100  can be a variable. For example, when the measuring device  40  is raised as illustrated in  FIG. 9 b   , a measurement range a 1  according to the collimator  42  shrinks to a measurement range a 2 , and the measurement volume of the target object  100  is thus reduced. 
     For example, a material having a significant shielding effect, such as a tungsten alloy, lead, iron, copper, and the like, is used in the collimator  42 , which thus functions as a shielding body. Therefore, the first shielding body  45 , which is below the collimator  42  and the main belt  20 , shields the natural radiation from the periphery of the measuring apparatus  4 , and thus reduces the background of the measurement range A. 
     In the present embodiment, a high density tungsten alloy was used in the collimator  42  and was disposed in the vicinity of the measuring device  40 , and thus a maximum shielding effect was obtained. The density of a tungsten alloy is approximately 18 g/cm 3  while the density of lead is approximately 11.34 g/cm 3 . This density ratio correlates to the thickness of the shielding body, and thus the same shielding effect can be obtained using a tungsten alloy that is approximately 63% as thick as a collimator made of lead, allowing a plurality of the measuring devices  40  to be disposed in close proximity with one another. In the present embodiment, the measuring devices  40  are disposed in the bottom part of the box  41  at a pitch of approximately 15 cm, and are thus set in close proximity to the target object  100 . 
     Additionally, in the present embodiment, a second cylindrical shielding body  46  is provided on the top part of the collimator  42 . By this, the effect of the background from above the measuring device  40  is reduced. For example, lead 30 mm thick is used as the second shielding body  46 . 
     When radioactivity sorting is executed with a focus on a specific radio nuclide in the target object  100 , an energy window range  40   x  of the measuring device  40  is set in an energy area of the specific radio nuclide. By setting an optimal energy window range  40   x  in relation to a photoelectric peak (emitted gamma ray energy) caused by the targeted radio nuclide, the effect of a natural nuclide contained in the target object  100  is minimized. As an example, an energy spectrum of a  137 Cs radiation source measured by an NaI (TI) scintillation detector is illustrated in  FIG. 10 . 
     The peak of  137 Cs is at 662 KeV. Thus, by making the setting 50 KeV to 950 KeV with a focus mainly on this peak portion, measurement can be done with a focus on  137 Cs and on  134 Cs as well. Because the scale of the horizontal axis is equivalent to three times the KeV units, a range of 150 to 2850 equates to the energy window range  40   x.  Because the energy window range  40   x  part is acceptable with regard to the background as well, the value of the obtained background is small. For example, uranium series and thorium series natural nuclides exhibit spectra resembling that of the aforementioned cesium, and thus energy is also distributed in a wide range. These effects can be made smaller by limiting the energy window range  40   x.  Additionally, potassium  40  ( 40 K) is present in particular abundance in the natural world, and the peak thereof is 1460 KeV. Therefore, by setting the energy window range  40   x  like that described above, the photoelectric peak of potassium  40  is not measured, the effect of potassium  40  is eliminated, and measuring accuracy is thus enhanced. In general, a measurement value obtained using three times the square root of the background, becomes the detection limit value. When the value of the background becomes low, the detection limit value also gets smaller. 
     The energy window range  40   x  is applied to reduce the effect of radiation caused by a natural radio nuclide present in the target object  100  or in the background, and to reduce the background. In other words, by reducing a volume, which is to be the base, the ability to detect radiation, which is to be the target to be measured, is enhanced. Furthermore, it thus becomes possible to sort based on the density of the radioactivity contained in the target object  100  without altering the nature of the object. 
     A vertical adjustment tool  47  is provided so that the box  41  can be changed to any height relative to the main belt  20  (target object  100 ). The range in which the measuring device  40  is reduced by the collimator  42  can be defined as the measurement range A using the height of the target object  100  on the main belt  20 , and the dispositions of the collimator  42  and the measuring device  40 . 
     The control device  5  controls the driving of the main belt  20  and the sorting belt  30  and displays various information on a monitor  51 . In the example illustrated in  FIG. 11 , a variety of windows  52 , such as a window  52   a  displaying the results of the measuring devices  40 , a window  52   b  displaying the driving direction of the sorting belt  30 , and a window  52   c  displaying the driving status of the main belt  20 , and the like, are displayed on the monitor  51 . 
     A column C displayed in the window  52   a  was obtained by viewing measurement values at the measurement unit of time (for example, one second) in each of the measuring devices  40 . In the example in  FIG. 11 , the column C differentiates levels of densities of radioactivity by color, and displays the levels so the densities of radioactivity thereof can be grasped visually. In the example in  FIG. 11 , the radioactivity level of a column Ca is the highest, and the level in a column Cb is the next highest. Furthermore, a top line L 1  of the window  52   a  illustrates the position of the measuring device  40 , and a line L 2  farthest to the back illustrates a position just before drop off on the sorting belt  30  at the downstream end  20   a  of the main belt  20 . 
     By the way, the target object  100  on the main belt  20  passes under the measuring device  40  at a fixed speed. As illustrated in  FIG. 12 , the measurement range A 1  of the target object  100  at a start time of a measurement unit of time is moved to a location illustrated by the symbol A 2  after the unit of time has passed. That is, the column C is the measurement value in the volume of the target object  100  that has passed the measurement range A during a specific unit of time. Additionally, because the target object  100  is transported at a specific speed, the measurement area of the next column C overlaps the measurement area of the previous column C. Therefore, the column C is the average value of the measurement values in the measurement unit of time, and the next column C can be regarded as the moving averaged value. Using these values, the measuring apparatus  4  converts the measurement result into a density of radioactivity and the control device  5  displays the result on the monitor  51  in real time and also determines a change in the measurement result. Here, a change in the measurement result either means that a measurement result (measurement value) that had fallen below the reference value has now exceeded the reference value, or the reverse. The control unit  5  controls the operation (driving) of the main belt  20  and the sorting belt  30  based on the change in the measurement result. Note that in the present embodiment, the highest measurement value of a line is determined by the line unit of the measuring device  40 . 
     The control device  5  stores the measurement values of the measuring device  40  in chronological order. For example, as illustrated in  FIG. 13 , the measurement results from the past  10  columns (C 1  through C 10 ) up to the current measurement time (time) are kept. In this example, columns C 4  through C 6  are larger than a reference value N, and the target object  100  for this portion is sorted to the sorting area S 1 . In  FIG. 13 , the symbol Δt indicates the movement time from directly under the measuring device  40  (measurement range A) to the downstream end  20   a  of the main belt  20 . 
     As has been described above, the measurement value of the column C is the average value in the measurement unit of time, and thus, for example, when a portion is present that is locally highly radioactive, there is a possibility that a variation in the result will be generated by the measurement timing due to the position of that portion. Thus, when the measurement value exceeds the reference value N, the main belt  20  is stopped at a time that is a specific first stopping time before an arrival time at which the portion will arrive at the downstream end  20   a.  In the example in  FIG. 13 , when a measurement start time is set as tp 0 , the main belt  20  stops at a time (arrival time tp 1 −first stopping time T 1 ) that is just the first stopping time T 1  earlier than the arrival time tp 1  (measurement start time tp 0 +measurement time t 1 +movement time Δt) when the portion of the target object  100  of the column C 4  will arrive at the downstream end  20   a.  In the present embodiment, the first stopping time T 1  is set at one second, which is the same as the measurement unit of time, and thus corresponds to one column. By this, the portion will not drop onto the sorting belt  30 , and thus will not be mixed in with a normal portion (column C 3 ). Therefore, sorting can be done with high accuracy. Furthermore, when the measurement value exceeds the reference value N and thus the measurement result changes, because the column C is the moving averaged value, it is unlikely that a highly radioactive portion will be mixed into the sorting area S 2 , even if stopping is done just before the measurement value rises. Therefore, efficiency can be raised without reducing sorting accuracy. 
     After that, the control device  5  rotates the sorting belt  30  in reverse to a time tp 2  that is after a sorting belt drive time T 2  from time tp 1  has elapsed, and also releases the stopping of the main belt  20 . The time T 2  is the time required to discharge all of the target object  100  on the sorting belt  30 , and is determined based on the distance between the pulleys  32   a  and the drive speed of the sorting belt  30 . By this, the target object  100  having different results will not be mixed in on the sorting belt  30 . In the example in  FIG. 13 , the target object  100  corresponding to the column C 4  was made to wait until the target object  100  corresponding to the column C 3  on the sorting belt  30  was discharged to the sorting area S 2 . 
     After that, when the measurement value falls below the reference value N, the main belt  20  is stopped at a time that is a specific second stopping time after an arrival time at which the portion will arrive at the downstream end  20   a.  In the example in  FIG. 13 , the main belt  20  is stopped after a time (arrival time tp 3 +second stopping time) that is just the second stopping time T 3  later than the arrival time tp 3  (measurement start time tp 0 +measurement time t 2 +movement time Δt) when the portion of the target object  100  of the column C 7  will arrive at the downstream end  20   a.  In the present embodiment, the second stopping time T 1  is three seconds, which is longer than the first stopping time T 1 , and thus corresponds to three columns worth of time. Just as with the previous case, there are variations due to the measurement unit of time in this case as well. Furthermore, when the value falls below the reference value N, the columns C until just before this indicate a target object with radioactivity that is higher than the reference value N. Because the measurement results of the columns C is a moving average, there is a possibility that portions with high radioactivity are included in the columns C that fall below the reference value N. Therefore, if the stopping time is set the same as for cases where the reference value N is exceeded, there is a risk that portions with high levels of radioactivity will become mixed into the sorting area S 2 . Accordingly, sorting accuracy can be prevented from declining by setting a time that is longer than the first stopping time T 1 . Furthermore, all of the target object with high radioactivity on the sorting belt  30  is discharged to the sorting area S 1  in the period from the time tp 4  after the second stopping time T 3  until the sorting belt drive time T 2  has elapsed. By repeating the operation described above, highly accurate and efficient sorting can be performed in a continuous fashion based on radioactivity levels. Note that when the measurement result changes within a period of time that is shorter than the second stopping time T 3 , the operation can be continued without changing the driving of the main belt  20  or the sorting belt  30 . 
     Note that daily inspections adjust equipment based on measurement values measured during the transport of a check source of known radioactivity using the main belt  20 . With regard to the measurement value, a comparison to a set value is performed, in view of statistical fluctuations, with a 95% degree of reliability, and taking the 5% portion into consideration, then the sorting is executed based on radioactivity. 
     Finally, the possibilities of other embodiments will be mentioned. While the aforementioned embodiment described an example using cesium, the embodiment is not intended to be limited thereto. It is physically possible to continuously sort the target object  100  using measurement values of the densities of radioactivity of any other substance. Furthermore, four of the measuring devices  40  were disposed in one row in a direction orthogonal to the transportation direction F 1 . However, the number and arrangement of the measuring devices is not limited to that given in the description above. 
     Furthermore, in the embodiment described above, the density of the target object  100  may be corrected by the control device  5 . For example, a weight scale is provided below the main belt  20  to measure weight, and the measurement value is corrected based on that weight. Furthermore, it is also possible to gauge the shape of the target object  100  in the vicinity of the discharge port  67  of the introduction hopper  6 , calculate the quantity of the target object  100  based on said shape, and then correct the measurement value. Additionally, it is also possible to capture an image of the target object  100  in the vicinity of the discharge port  67  of the introduction hopper  6 , and then correct the measurement value based on image processing of the captured image. By this, measuring accuracy can be further enhanced. 
     In the embodiment described above, the energy window range  40   x  was set as a comparatively wide range including the peak portion of  137 Cs (cesium), however, this range is not intended to be limited thereto. For example, by focusing only on the peak portion of  137 Cs (cesium) and thus setting the range from 500 KeV to 870 KeV, the energy window range  40   x  can be set in the range of 1500 to 2610. Of course, the range is not limited to  137 Cs (cesium), and thus may be suitably set based on the radio nuclide, target object to be measured, or the like, which is the object to be detected. 
     In the embodiment described above, sorting was executed by changing the operating direction of the sorting belt  30 , however, sorting can be combined, for example, with a system using a segmenting method (a method that sets small box shaped sorting ducts on each of the lines of the measuring devices  40  and then sorts by each of the lines) so that sorting can be done in narrow ranges. Furthermore, sorting can also be done by driving the main belt intermittently to ensure measuring times in cases where low level radioactivity is to be measured. 
     POSSIBILITY OF INDUSTRIAL USE 
     The present invention can sort large quantities of radioactively contaminated objects by the radiation levels thereof based on a wide range of radioactive contamination. Targeted radioactively contaminated objects are soil, waste products, incineration ash, fly ash, vegetation, and the like, as well as mixtures thereof, and may also apply to food products such as rice, fish, and the like. Furthermore, sorting is executed physically, and thus reuse after sorting is easy because the physical properties possessed by the target object to be measured are not changed. 
     BRIEF DESCRIPTION OF THE NUMERICAL REFERENCES 
       1 : Radiation measuring and sorting device,  2 : Transporting mechanism,  3 : Sorting mechanism,  4 : Measuring apparatus,  5 : Control device (personal computer),  6 : Introduction hopper,  7 : Height adjusting device,  9 : Power supply device,  20 : Main belt (transporting belt),  20   a:  Downstream end,  20   b:  Upstream end,  21 : Chassis,  21   z:  Leg part,  22   a:  Drive (transport) pulley,  22   b:  Tail pulley,  22   c:  Snap pulley,  23 : Return roller,  24 : Inverter motor,  25 : Meander prevention mechanism,  26 : Scraper,  27 : Baffle plate,  27   a:  Attaching member,  28 : Plate like member,  28   a:  Backup member,  29 : Skirt,  30 : Sorting belt,  31 : Chassis,  31   a:  Lower level,  31   b:  Middle level,  31   c:  Upper level,  32   a:  Pulley,  32   b:  Snap pulley,  32   c:  Drive pulley,  34 : Inverter motor,  36 : Scraper,  37 : Trough roller,  38 : Carrier roller,  38   a:  Securing member,  39 : Skirt,  40 : Measuring device,  40   x:  Energy window range,  41 : Box,  41   a:  Cover,  42 : Collimator,  43 : Temperature adjusting part,  44 : Height adjusting part,  45 : First shielding body,  46 : Second shielding body,  51 : Monitor,  52 : Window,  52   a:  Result window,  52   b:  Drive direction window,  52   c:  Operation control window,  60 : Main body part,  60   a:  Upper front wall,  60   b:  Upper rear wall,  60   c:  Upper side wall,  60   d:  Lower front wall,  60   e:  Lower rear wall,  60   f:  Lower side wall,  61 : Introduction port,  62 : Height direction middle part,  63 : Lower part,  64 : Fixture,  65 : Skirt,  66 : Inclined plate,  67 : Discharge port,  68 : Height adjusting mechanism,  68   a:  Jack,  68   b:  End part (leverage point),  68   c:  Operating handle,  68   d:  Mounting shaft (fulcrum),  68   e:  Fixed base,  70 : Adjusting bar,  70   a:  Apex part,  71 : Securing part,  72 : Scraper,  72   a:  End part,  73 : Height adjusting part,  100 : Target object,  100   a:  Top surface,  101 : Uneven part, θ: Trough angle, A, A 1 , and A 2 : Ranges of measurement, C: Column, F 1 : Transportation direction (operating direction), F 2 : Operating direction, GL: Ground, H: Height, L 1 , and L 2 : Lines, S 1 : Sorting area (HOT side), S 2 : Sorting area (CLEAN side), T 1 : First stopping time, T 2 : Sorting belt drive time, T 3 : Second stopping time, W 1 : Belt width, and N: Reference value.