JP2015111069A - Radioactivity inspection apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce measurement error of an amount of radioactivity due to uneven distribution of radioactivity for a vessel storing radiation-emitting waste.SOLUTION: A radioactivity inspection device includes: a radiation detector 13 detecting γ-rays emitted from waste 11 stored in a vessel 12 at a plurality of relative positions to the vessel 12, and outputting radiation signals; radiation counting means 14 counting the radiation signals and determining a detector response pattern; uneven-distribution-pattern storage means 16 storing a plurality of types of radioactivity uneven distribution patterns of the waste 11 stored in the vessel 12 and a plurality of estimation detection response patterns corresponding to the radioactivity uneven distribution patterns, respectively; uneven-distribution-pattern estimation means 15 collating the detector response pattern with the estimation detector response patterns, and selecting one radioactivity uneven distribution pattern corresponding to any of the estimation detector response patterns; and radioactivity calculation means 17 calculating an amount of radioactivity of the vessel 12 from a radiation count value using a radioactivity conversion coefficient set associated with the selected radioactivity uneven distribution pattern.

Description

  Embodiments described herein relate generally to a radioactivity inspection apparatus and method for measuring a radioactivity amount of a measurement object housed in a container.

  The amount of radioactivity present in the environment, such as soil and food, has been examined by a small amount of sampling analysis until now, but a large amount of radioactivity was released into the general environment due to an accident at a nuclear power plant. Therefore, it has become necessary to conduct a complete inspection of radioactivity on a large amount of contaminated soil, waste, or food. In this case, since manual measurement using a radiation survey meter is limited in quantity, an apparatus capable of automatically measuring a large number of objects at high speed is required.

  As a conventional technique corresponding to this, for example, there is an article carry-out monitor used in radiation management of a nuclear facility. This is a device for inspecting the presence or absence of radioactivity by measuring the radioactivity density on the surface of an article in a short time at a time, arranging a plurality of articles on a large tray on a roller conveyor and transporting them to a β-ray detector. Β-rays emitted mainly from the surface of the article are detected and converted to surface radioactivity density, and further, the amount of radioactivity inside the article is detected using a γ-ray detector as an auxiliary. Since this apparatus mainly performs radioactivity inspection on the surface of an article using β-rays, it is not suitable for inspection of a thick and large object.

  In addition, as a device for inspecting large waste and a large amount of waste in a nuclear facility, there are inspection devices for radioactive waste stored in a 200 L drum can or a large rectangular container. This is to measure the γ-rays generated from the waste stored in drums etc. and convert it into radioactivity, and all the commercially available ones include large-scale inspections including the mechanism that drives the container. It is a device.

  In these devices, if the waste in the container to be measured has a radioactivity bias, there will be a difference in the transmission distance of the gamma ray through the waste. When the activity is concentrated, the sensitivity of γ-ray detection is significantly reduced due to the effect of γ-ray absorption by the waste. Conversely, when the radioactivity is concentrated near the front of the detector, almost no γ-ray is absorbed. Since the light is incident on the γ-ray detector, the detection sensitivity of γ-ray increases. When there is a bias in radioactivity in the container that contains waste in this way, the measurement error of the radioactivity amount increases due to a significant fluctuation in the detection sensitivity of γ-rays. Has been proposed.

  The simplest method among them is to make the deviation in the circumferential direction of radioactivity uniform by measuring while rotating the container in which the waste is stored. In general, the drum can be continuously rotated, but in the case of a rectangular container, the measurement may be performed by intermittently rotating the container every 90 °, for example.

  Since the radial deviation of radioactivity cannot be corrected only by rotating the container, it may be corrected in combination with another method. One of them, the emission CT method, is to specify the radiation generation position by the CT method, and it is possible to obtain a detailed radioactivity distribution although it is affected by the density distribution. However, since a large number of γ-ray detectors and collimators are required for CT scanning, the apparatus scale is increased.

  In addition, there are methods for estimating the source position from the ratio between the photoelectric peak count rate and the scattered ray count rate of the γ-ray energy spectrum, and nuclides that emit two or more γ rays, such as Co-60 and Eu-154. In the case of an object, a method is used in which the source position is estimated from the ratio of the photoelectric peak count rate of the energy spectrum in each γ-ray. In this case, without rotating the container, for example, the object to be measured is divided into several parts in the horizontal direction and measurement is performed for each divided section, and the response function of the γ-ray detector such as the scattered ray count rate obtained in advance is obtained. There is a method for estimating the position of the radiation source by using it.

JP-A-4-235379 JP-A-2005-180936

Tetsuo Goto et al. A RADIOACTIVITY ASSAY METHOD USING COMPUTED TOMOGRAPHY American Nuclear Society NUCLEAR TECHNOLOGY VOL. 100 DEC. 1992

  However, the first problem of the prior art for correcting the bias of the radioactivity distribution as described above is that a mechanism unit for continuously rotating the container or dividing the measurement object and measuring for each divided section. In particular, in the case of the emission CT method, since the number of γ-ray detectors and collimators increases, the scale of the apparatus becomes large and complicated, and the cost increases.

  The second problem is that in the case of realistic waste resulting from a nuclear power plant accident, it is not a local bias of radioactivity but a gentle radioactivity distribution, and the main nuclide is a γ-ray energy spectrum. Since it is considered that Cs-137 exhibits a single peak at the same time, it is difficult to clearly estimate the source position by correction using only the conventional scattered ray count rate together with the peak count rate. The conventional correction using the is not applicable.

  The object of the embodiment of the present invention is made in consideration of the above-mentioned circumstances, and the amount of radioactivity due to the uneven distribution of radioactivity is measured with a relatively simple configuration for a container in which a measurement object that emits radiation is stored. An object of the present invention is to provide a radioactivity inspection apparatus and method that can reduce measurement errors.

  A radioactivity inspection apparatus according to an embodiment of the present invention detects a radiation emitted from an object to be measured housed in a container and outputs a radiation signal, and a radiation detector capable of changing a relative position with the container. The radiation detector counts the radiation signal output for each of a plurality of relative positions with respect to the container, and obtains a detector response pattern from the radiation count value, and the measurement object stored in the container A plurality of types of radioactive uneven distribution patterns of objects, and a plurality of types of estimation detector response patterns corresponding to each of the plurality of types of radioactive uneven distribution patterns are preliminarily stored, and obtained by the radiation counting unit. A detector response pattern is collated with a plurality of types of estimation detector response patterns stored in advance in the uneven distribution pattern storage means, and one of the estimation detection patterns is checked. The radiation count using the uneven distribution pattern estimation means for selecting the radiation uneven distribution pattern corresponding to the response pattern of the vessel and the radioactivity conversion coefficient set in association with the radiation uneven distribution pattern selected by the uneven distribution pattern estimation means And a radioactivity calculating means for calculating the radioactivity amount of the container from the radiation count value counted by the means.

  In the radioactivity inspection method according to the embodiment of the present invention, a radiation detector detects radiation at a plurality of positions around a container in which a measurement object that emits radiation is stored, outputs a radiation signal, and counts the radiation signal. A detector response pattern is obtained from the radiation count value, and using this detector response pattern, the radioactivity uneven distribution pattern of the measurement object stored in the container is estimated, and the radioactivity uneven distribution pattern is set in association with the radioactivity distribution pattern. The radioactivity amount of the container is calculated from the radiation count value using a radioactivity conversion count.

  According to the embodiment described above, the measurement error of the radioactivity amount due to the uneven distribution of radioactivity can be reduced with a relatively simple configuration for the container in which the measurement object that emits radiation is stored.

The block diagram which shows the radioactivity inspection apparatus which concerns on 1st Embodiment. The graph which shows the relationship between the ratio of the photoelectric peak count rate and scattering area count rate in a gamma ray energy spectrum, and the radiation source position in a container. The chart which shows an example of databases, such as a radioactivity uneven distribution pattern and the detector response spectrum for estimation memorize | stored in the uneven distribution pattern memory | storage means of FIG. The block diagram which shows the radioactivity inspection apparatus which concerns on 2nd Embodiment. The side view which shows the case where the height direction with respect to the container of a radiation detector is changed in the radioactivity inspection apparatus of FIG.1 and FIG.4.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
[A] First embodiment (FIGS. 1 to 3)
FIG. 1 is a configuration diagram showing a radioactivity inspection apparatus according to the first embodiment. The radioactivity inspection apparatus 10 according to the first embodiment detects radiation emitted from the waste 11 as a measurement target housed in the container 12 and outputs a radiation signal, and in the circumferential direction on the side surface of the container 12. The radiation detector 13 capable of changing the relative position, the radiation counting means 14 provided at the subsequent stage of the radiation detector 13, the uneven pattern estimating means 15 provided at the subsequent stage of the radiation counting means 14, and the uneven distribution pattern The uneven distribution pattern storage means 16 connected to the estimation means 15 and the radioactivity calculation means 17 provided in the subsequent stage of the uneven distribution pattern estimation means 15 are comprised.

  The container 12 is a large waste container such as a 200 L drum can or a flexible container bag. The waste 11 stored in the container 12 emits γ-rays as radiation, and the γ-rays are incident on the radiation detector 13 while being absorbed by the waste 11 itself and the container 12.

  The radiation detector 13 is a γ-ray detector that detects γ-rays as radiation. Generally, a NaI (Tl) scintillation detector or a Ge semiconductor detector is used, but γ-ray energy information is obtained. The type is not particularly limited as long as it is possible. The radiation detection means 13 has a variable relative position with respect to the side surface of the container 12. In the example of FIG. 1, a plurality of circumferential positions of the container 12, i. To detect gamma rays. The radiation detector 13 outputs a radiation signal (for example, a pulse having a peak value) proportional to the incident γ-ray energy, and the radiation signal is counted by the radiation counting means 14.

  The radiation counting means 14 is, for example, a multiwave height analyzer, and the radiation detector 13 detects and outputs a γ-ray for each of a plurality of relative positions (the aforementioned positions a, b, c, d) with respect to the container 12. And the γ-ray energy spectrum is measured for each relative position of the radiation detector 13. Further, the radiation counting means 14 obtains a radiation count value (that is, a peak count rate of the γ-ray energy spectrum for each relative position of the radiation detector 13 and a scattering region count rate) from the measured γ-ray energy spectrum for each relative position, A detector response pattern is calculated from the radiation count value.

  This detector response pattern shows the ratio of the photoelectric peak count rate in the γ-ray energy spectrum at the opposite relative positions of the radiation detector 13 (for example, positions a and c, positions b and d), and the relative positions adjacent to the radiation detector 13. The ratio of the photoelectric peak count rate in the γ-ray energy spectrum at positions (for example, positions a and c, positions c and d), and γ at each relative position (ie, positions a, b, c, d) of the radiation detector 13. The ratio between the photoelectric peak count and the scattering region count rate in the line energy spectrum is combined. In this detector response pattern, a relative value may be used as the numerical value of the ratio of each count rate.

  By comparing the photoelectric peak count rate of the γ-ray energy spectrum at each position a to d at the opposite position and the adjacent position, the circumferential direction in the container 12 can be obtained regardless of the amount of radioactivity of the waste 11. Count rate distribution can be obtained.

  Further, the source position in the depth direction (radial direction) in the container 12 can be obtained by comparing the photoelectric peak count rate and the scattering region count rate of the γ-ray energy spectrum at each position a to d. .

For example, FIG. 2 shows the source position of Cs-137 in the container 12 when gamma rays from the waste 11 having a density of 1.3 g / cm ³ are measured, and Cs using a NaI (Tl) scintillation detector. The relationship between the photoelectric peak count rate of the γ-ray energy spectrum from −137 and the ratio of the scattered ray region count rate is shown. Since γ rays from the source near the center of the container 12 are affected by absorption and scattering by the waste 11, the photoelectric peak count rate of the γ-ray energy spectrum is reduced, and the scattering region count rate is increased instead. . On the other hand, γ-rays from the radiation source near the surface of the container 12 are hardly affected by the above-described absorption and the like, and the peak count rate of the γ-ray energy spectrum increases. Further, when the radioactivity is uniformly distributed in the container 12, the ratio between the photoelectric peak count rate and the scattering region count rate of the γ-ray energy spectrum is the same as when the radiation source is near the center of the container 12 and near the surface. In the example of FIG. 2, it is approximately 0.5.

  Here, FIG. 2 is an example, and the relationship between the ratio between the photoelectric peak count rate and the scattering region count rate and the source position is actually the material of the waste 11 in the container 12 and the disposal in the container 12. It varies depending on the density of the object 11 and the shape of the container 12.

  As shown in FIG. 3, the uneven distribution pattern storage means 16 includes waste conditions such as the shape of the container 12 and the density of the waste 11 in the container 12, and the radioactivity concentration ratio of the waste 11 stored in the container 12. And a plurality of types obtained for each relative position of the radiation detector 13 corresponding to each of the distribution conditions such as a plurality of types of radioactive uneven distribution patterns of the waste 11 stored in the container 12 and the radiation uneven distribution patterns. Are stored in association with each other in advance.

  Among these, the estimation detector response pattern is matched with the detector response pattern obtained by the radiation counting means 14, and at the relative positions (for example, positions a and c, positions b and d) of the radiation detector 13. The ratio of the photoelectric peak count rate in the γ-ray energy spectrum, the ratio of the photoelectric peak count rate in the γ-ray energy spectrum at the adjacent relative positions of the radiation detector 13 (for example, positions a and c, position c and d), radiation detection The ratio of the photoelectric peak count rate and the scattering region count rate in the γ-ray energy spectrum at each relative position (namely, position a, b, c, d) of the vessel 13 is combined.

  The numerical value of the estimation detector response pattern may be calculated by actually measuring in advance a combination of the standard radiation source and the simulated waste, or may be calculated by simulation calculation. Even in this estimated detector response pattern, a relative value may be used as the numerical value of the ratio of each count rate.

  Also, the radioactivity uneven distribution pattern is determined in advance from the distribution pattern of the waste 11 in the container 12 that is actually assumed in accordance with the arrangement of the radiation detector 13 and the storage state of the waste 11 in the container 12. You just have to. FIG. 3 shows an example of a pattern in which the cylindrical container 12 is divided into the circumferential direction, the height direction, and the radial direction, and the radioactive concentration in the white area is 10 times the radioactive concentration in the hatched area. Is set to The division may be further subdivided, and the shape of the division is not particularly limited.

  Furthermore, the radioactivity concentration ratio may be set to a concentration ratio that is actually assumed according to the target waste 11, and the strength classification is not limited to two stages, but is increased to three or more stages as necessary. Also good.

  The uneven distribution pattern estimation means 15 collates the detector response pattern obtained by the radiation counting means 14 with the estimation detector response pattern stored in the uneven distribution pattern storage means 16, and the detector response pattern obtained by the radiation counting means 14. The radioactivity uneven distribution pattern of the waste 11 in the container 12 is estimated by selecting the radioactivity uneven distribution pattern corresponding to the estimation detector response pattern that substantially coincides with.

  Specifically, the uneven distribution pattern estimation unit 15 determines that the individual numerical values of the estimation detector response pattern corresponding to the radioactivity uneven distribution pattern stored in the uneven distribution pattern storage unit 16 substantially match at the time of collation described later. The determination range for this is determined in advance. Next, the uneven distribution pattern estimation means 15 compares the individual numerical values of the detector response pattern obtained by the radiation counting means 14 with the individual numerical values of the estimation detector response pattern, and enters the determination range when it is determined. A radioactivity uneven distribution pattern corresponding to the estimation detector response pattern in which the width is set is extracted.

  When there is one extracted radioactivity uneven distribution pattern, this radioactivity uneven distribution pattern becomes the radioactivity uneven distribution pattern to be estimated. When there are a plurality of extracted radioactivity uneven distribution patterns, the uneven distribution pattern estimation means 15 performs the following. Follow the procedure. In other words, the uneven distribution pattern estimation means 15 calculates the difference between the individual numerical values of the estimation detector response pattern corresponding to the extracted radioactive uneven distribution pattern and the individual numerical values of the detector response pattern obtained by the radiation counting means 14. When it becomes the smallest, the radiation uneven distribution pattern corresponding to the estimation detector response pattern having the smallest difference is selected as the radiation uneven distribution pattern to be estimated.

  If there are a plurality of estimation detector response patterns that minimize the difference between the individual detector response patterns obtained by the radioactivity counting means 14, these estimation detector response patterns A plurality of radioactivity uneven distribution patterns corresponding to the respective patterns are output to the radioactivity calculation means 17.

  The radioactivity calculation means 17 first sums up the radiation count values (especially the photoelectric peak count rate of the γ-ray energy spectrum) counted by the radiation counting means 14 at each relative position of the radiation detector 13 with respect to the container 12. Next, the radioactivity calculation means 17 is counted by the radiation counting means 14 using the radioactivity uneven distribution pattern estimated by the uneven distribution pattern estimation means 15 and the radioactivity conversion coefficient set in association with the waste conditions. The radioactivity amount of the container 12 in which the waste 11 is stored is calculated by multiplying the total value of the radiation count values by the radioactivity conversion coefficient. The calculation result of the radioactivity amount is displayed and recorded on the screen when the radioactivity calculation means 17 is constituted by a personal computer.

  When a plurality of radioactivity uneven distribution patterns are estimated and output from the uneven distribution pattern estimation means 15, the radioactivity calculation means 17 obtains a radioactivity conversion coefficient for each of the plurality of radioactivity uneven distribution patterns and separately separates the amount of radioactivity. In consideration of the safety factor, the largest amount of radioactivity is taken as the calculated value.

With the configuration as described above, the following effects (1) and (2) are achieved according to the first embodiment.
(1) The radiation detector 13 detects γ-rays and outputs radiation signals at a plurality of positions around the container 12 in which the waste 11 that emits γ-rays as radiation is stored. The radiation counting means 14 counts the radiation signal to obtain a radiation count value (photo peak count rate of γ-ray energy spectrum, scattering region count rate), and a detector response pattern from the radiation count value. The uneven distribution pattern estimation means 15 estimates the radioactivity uneven distribution pattern of the waste 11 stored in the container 12 using the detector response pattern and the estimation detector response pattern stored in the uneven distribution pattern storage means 16. . The radioactivity calculation means 17 uses the radioactivity conversion coefficient set in association with this radioactivity uneven distribution pattern or the like to calculate the container 12 from the total value of the radiation count values (particularly the photoelectric peak count rate) counted by the radiation count means 14. Calculate the amount of radioactivity. For this reason, the measurement error of the radioactivity amount due to the uneven distribution of radioactivity can be reduced with a relatively simple configuration for the container 12 in which the waste 11 that emits γ rays is stored.

  (2) Moreover, in the radiation inspection apparatus 10, since the required number of the radiation detectors 13 is small and the structure of the apparatus is not large and complicated, low cost can be realized.

[B] Second Embodiment (FIG. 4)
FIG. 4 is a configuration diagram showing a radioactivity inspection apparatus according to the second embodiment. In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description is simplified or omitted.

  The radiation inspection apparatus 20 of the second embodiment is different from the first embodiment in that a plurality of (for example, two) radiation detectors 13 are arranged in the circumferential direction of the container 12 and rotation for mounting the container 12 is performed. The base 21 is configured such that the relative position of the radiation detector 13 with respect to the side surface of the container 12 can be changed by rotating the container 12 at a predetermined pitch of 180 ° or less in the circumferential direction. Further, the radiation counting means 14 is individually provided in the subsequent stage of the plurality of radiation detectors 13, and the plurality of radiation counting means 14 are connected to a single uneven distribution pattern estimating means 15.

  That is, when two radiation detectors 13 are arranged at opposing positions (opposite positions in the circumferential direction of the container 12), and further, the container 12 is rotated in the e direction at a pitch of 90 ° by the rotating table 21, twice. In this detection operation, detection at four positions a to d in FIG. 1 becomes possible. Similarly, when the two radiation detectors 13 are arranged at a circumferential angle of 90 ° in the container 12 and the container 12 is rotated in the e direction at a pitch of 180 ° by the turntable 21, 2 is similarly applied. The detection operation at one time makes it possible to detect at four positions a to d in FIG. Although the arrangement angle with respect to the container 12 in which the radiation detector 13 is arranged is not particularly limited, the detection position of the radiation detector 13 obtained by the combination of the arrangement angle of the radiation detector 13 and the rotation pitch of the turntable 21 is an unevenly distributed pattern storage unit. 16 is matched with the detection position of the radiation detector 13 in the estimation detector response pattern stored in FIG.

  The radiation signals (crest value pulses) output from the two radiation detectors 13 are counted by the two radiation counting means 14 at the subsequent stage. Each radiation counting means 14 measures a γ-ray energy spectrum at the detection position of the connected radiation detector 13 and partially calculates a detector response pattern. Furthermore, the uneven distribution pattern estimation means 15 combines the detector response patterns obtained by the radiation counting means 14 into one, and the combined detector response patterns are stored in the uneven distribution pattern storage means 16 as radioactive uneven distribution. A radioactivity uneven distribution pattern is estimated by collating with an estimation detector response pattern corresponding to the pattern. The process from the estimation of the radioactivity uneven distribution pattern to the calculation of the radioactivity amount is the same as in the first embodiment.

  With the configuration as described above, the second embodiment also provides the following effect (3) in addition to the same effects as the effects (1) and (2) of the first embodiment.

  (3) A plurality of radiation detectors 13 are arranged in the circumferential direction of the container 12, and each radiation detector 13 is rotated by rotating the container 12 at a predetermined pitch in the circumferential direction by a turntable 21 for mounting the container 12. Since the uneven distribution pattern estimation means 15 estimates the radioactive uneven distribution pattern with a small number of detections of γ rays, the amount of radioactivity of the container 12 in which the waste 11 is stored can be calculated in a short time.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. Is included in the scope and gist of the invention, and is included in the invention described in the claims and the equivalents thereof.

  For example, as shown in FIG. 5, the position a of the radiation detector 13 is changed in the height direction of the container 12 such as positions a1 and a2 with respect to the container 12, and the radiation detector 13 is at each height position. Γ rays may be detected by relative movement in the circumferential direction of the container 12.

  In both of the above-described embodiments, the radiation counting means 14 is a multi-wave height analyzer capable of measuring a γ-ray energy spectrum. However, the γ-ray energy spectrum has a simple spectral shape and has a peak region and a scattering region. If it can be easily distinguished, a single channel analyzer that can discriminate and measure about two regions may be used.

10 Radiation Inspection Equipment 11 Waste (Measurement Object)
12 Container 13 Radiation detector 14 Radiation counting means 15 Uneven distribution pattern estimation means 16 Uneven distribution pattern storage means 17 Radioactivity calculation means 20 Radiation inspection apparatus 21 Turntable

Claims (8)

A radiation detector capable of detecting radiation emitted from a measurement object stored in a container and outputting a radiation signal, and capable of changing a relative position with the container;
The radiation detector counts the radiation signal output for each of a plurality of relative positions with the container, and the radiation counting means obtains a detector response pattern from the radiation count value,
A plurality of types of radioactivity uneven distribution patterns of the measurement object stored in the container and a plurality of types of estimation detector response patterns corresponding to the plurality of types of radioactivity uneven distribution patterns are stored in advance. When,
The radioactivity corresponding to one of the estimation detector response patterns is obtained by collating the detector response pattern obtained by the radiation counting means with a plurality of types of estimation detector response patterns stored in advance in the uneven distribution pattern storage means. An uneven distribution pattern estimating means for selecting an uneven distribution pattern;
Radiation for calculating the radioactivity amount of the container from the radiation count value counted by the radiation counting means, using the radioactivity conversion coefficient set in association with the radioactivity uneven distribution pattern selected by the uneven distribution pattern estimating means A radioactivity inspection apparatus comprising: The radiation detector is a γ-ray detector that detects γ-rays,
The detector response pattern obtained by the radiation counting means and the estimation detector response pattern stored in the uneven distribution pattern storage means are the ratio of the photoelectric peak count rate in the γ-ray energy spectrum at the opposite position of the radiation detector, The ratio of the photoelectric peak count rate in the γ-ray energy spectrum at the position adjacent to the radiation detector, the ratio of the photoelectric peak count rate and the scattering region count rate in the γ-ray energy spectrum at each position of the radiation detector, The radioactivity test apparatus according to claim 1, wherein the radioactivity test apparatus is combined. The uneven pattern estimation means has a predetermined determination width for each numerical value of the estimation detector response pattern corresponding to the radioactivity uneven distribution pattern stored in the uneven distribution pattern storage means,
When each numerical value of the detector response pattern obtained by the radiation counting means is compared with each numerical value of the estimation detector response pattern and enters the determination range, the radioactivity corresponding to the estimation detector response pattern Extract the uneven distribution pattern,
When the difference between the individual numerical value of the estimation detector response pattern corresponding to the extracted radioactivity uneven distribution pattern and the individual numerical value of the detector response pattern is the smallest, the detection for estimation in which the difference is the smallest The radioactivity inspection apparatus according to claim 1, wherein a radioactivity uneven distribution pattern corresponding to the vessel response pattern is selected as the radioactivity uneven distribution pattern. 4. The radiation detector according to any one of claims 1 to 3, wherein the radiation detector is configured such that a relative position with respect to a side surface of the container can be changed by rotating the container by a turntable for mounting the container. The radioactivity test apparatus according to claim 1. A plurality of the radiation detectors are arranged in the circumferential direction of the container, and the relative position with respect to the side surface of the container can be changed by rotating the container at a pitch of 180 ° or less in the circumferential direction. The radioactivity inspection apparatus according to any one of claims 1 to 4. The radiation detector detects radiation at a plurality of positions around the container containing the measurement object that emits radiation, outputs a radiation signal, obtains a detector response pattern from the radiation count value obtained by counting the radiation signal,
Using this detector response pattern, estimate the radioactivity uneven distribution pattern of the measurement object stored in the container,
A radioactivity inspection method, wherein a radioactivity amount of the container is calculated from the radiation count value using a radioactivity conversion count set in association with the radioactivity uneven distribution pattern. The estimation of the radioactivity uneven distribution pattern includes a plurality of types of radioactivity uneven distribution patterns of the measurement object stored in the container, and a plurality of types of estimation detector response patterns corresponding to the plurality of types of radioactivity uneven distribution patterns, respectively. Prepare memorized uneven distribution pattern storage means,
It is performed by collating a detector response pattern obtained from a radiation count value with the estimation detector response pattern and selecting a radioactivity uneven distribution pattern corresponding to any one of the estimation detector response patterns. The radioactivity test method according to claim 6. The radiation detector is a gamma ray detector that detects gamma rays,
The detector response pattern obtained from the radiation count value and the detector response pattern for estimation stored in the uneven distribution pattern storage means are the ratio of the photoelectric peak count rate in the γ-ray energy spectrum at the opposite position of the radiation detector, The ratio of the photoelectric peak count rate in the γ-ray energy spectrum at the position adjacent to the radiation detector, the ratio of the photoelectric peak count rate and the scattering region count rate in the γ-ray energy spectrum at each position of the radiation detector, The radioactivity test method according to claim 6 or 7, wherein the radioactivity test method is combined.

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