JP2020003327A - Radioactivity concentration evaluation system, and radioactivity concentration evaluation system - Google Patents

Abstract

To make it possible to evaluate radioactivity concentration in a short calculation time and with high accuracy in a radioactivity concentration system.SOLUTION: A radioactivity concentration evaluation system 1 comprises: an analysis unit 101 that calculates a first gamma ray spectrum 65 on the basis of a three-dimensional model 18 of a measurement object 24 stored in a container 41; a screening measurement unit 201 that acquires radiation actual measurement data 70 serving actual measurement data on a radiation distribution in the measurement object 24 before storing the measurement object 24 in the container 41; and an inner-container concentration distribution evaluation unit 501 that evaluates a radioactivity concentration distribution in the container 41 on the basis of an actual gamma ray spectrum 72 to be actually measured using a plurality of gamma ray detectors 47 arranged around the container 41 after storing the measurement object 24 in the container 41 and corresponding to the first gamma ray spectrum 65, and the radiation actual measurement data 70.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a radioactivity concentration evaluation system and a radioactivity concentration evaluation method.

  In the decommissioning of nuclear power facilities, radioactive waste such as radioactive waste and waste contaminated by radioactivity is generated as the facilities are dismantled. Since the treatment and disposal of these wastes is required according to the radioactivity concentration level, it is necessary to measure the radioactivity concentration. In measuring the radioactivity concentration, gamma rays emitted from a gamma ray source such as Co-60 or Cs-137 are mainly used. Radioactive waste includes metals such as pipes and valves, concrete generated when buildings are dismantled, and the like. Conventionally, these wastes are stored in drums, and the drums are filled with mortar, sand, or the like, and then the management, treatment, disposal, etc. of the wastes are performed. In management, processing, disposal, etc., it is necessary to measure and quantify the radioactivity concentration of the measurement target such as waste stored in a drum. As a method for measuring the radioactivity concentration in a drum can, for example, a method disclosed in Patent Document 1 is known.

  The abstract of Patent Document 1 states that "a collimator is installed in front of a radiation detector, and a plurality of radiations emitted from the radioactive waste are converted into an energy spectrum in the height direction of the radioactive waste while rotating and lifting the radioactive waste. And the amount of radiation attenuation in the region is evaluated based on the ratio of the scattered radiation intensity to the non-scattered radiation intensity obtained from the energy spectrum of each region. "

In recent years, in order to streamline the transportation, treatment and disposal of waste, it has been discussed that the waste storage container is changed from a drum can to a square container. Patent Literatures 2 to 4 disclose devices for measuring the radioactivity in a rectangular container.
That is, the abstract of Patent Literature 2 includes “a radiation detection unit 2 that detects a radiation dose of a radioactivity measurement target, an information acquisition unit 8 that obtains mass, height, and density of the radioactivity measurement target, The storage unit 9 in which the relationship between the radiation detection limit and the radiation detection time according to the mass, height, and density of the object is stored in advance, and the mass, height, and density are input from the information acquisition unit 8, and the storage unit is 9 for reading out the relationship between the radiation detection limit and the radiation detection time stored in 9 and setting the radiation detection time in the radiation detection unit 2. "

  In addition, the abstract of Patent Document 3 states that “the maximum value of the amount of radioactivity in each small area divided by dividing the measurement site of the measurement target can be obtained by a preliminary investigation of the contamination status of the radioactive substance in the measurement target. The radiation detector count is calculated for each small area based on the maximum value of the radioactivity for each small area and the radioactivity conversion coefficient for each small area. The sum obtained by adding the count rates in the order of the radioactivity conversion coefficient of the small area in the descending order is the count rate obtained by actually measuring the measurement object with the radiation detector. The amount of radioactivity of the object to be measured is determined based on the number of additions of the small areas and the maximum value of the small areas when the above is achieved. "

  In addition, the abstract of Patent Document 4 states that “in a state where a radioactive waste body is stored in a storage container, the radiation energy spectrum is simulated to measure the energy spectrum of radiation leaking from the inside outside the storage container. Refer to the radiation energy spectrum analysis procedure to be analyzed, the radiation energy spectrum measurement procedure, and the radiation energy spectrum analysis result, compare with the radiation energy spectrum measurement result, and repeat the search for the radiation energy spectrum analysis result based on the difference. A radiation energy spectrum search procedure for determining a radiation energy spectrum analysis result having a small difference from a measurement result, and a radioactivity estimation procedure for estimating a radioactivity amount or a radioactivity concentration based on the determined radiation energy spectrum analysis result are provided. " That.

JP 2000-56025 A JP-A-2015-121505 JP 2015-145792 A JP 2015-219046 A

  By the way, when a drum can is used as a waste container, a gap is generated when the drum can is transported or buried in a disposal site, so that there is a problem that the space cannot be effectively used. Therefore, it is preferable to use a square (substantially rectangular parallelepiped) container as a storage container instead of a drum can for the purpose of streamlining transport, processing and disposal. In addition, dismantling waste generated when dismantling a nuclear power plant may have various shapes and sizes. Therefore, regardless of whether the container is a drum or square container, when waste is stored in a container, the distribution of radioactive waste density and the distribution of radioactivity concentration may be biased in the container. There is. Here, when the radioactivity is evaluated assuming that the density and concentration in the container are uniform without considering the possibility of the radioactive waste density and the distribution of the radioactivity concentration distribution, the evaluation error is extremely large. Could be.

  According to the technique described in Patent Document 1, the radioactivity concentration distribution and the like are measured while rotating the drum. Therefore, even when the radioactive waste density and the radioactivity concentration distribution in the drum can are unevenly distributed, it is possible to measure the average value by measuring while rotating the drum. On the other hand, in the case of a rectangular container, it is difficult to apply the method described in Patent Document 1 because there is no rotational symmetry unlike a drum can. For this reason, there is a problem that it is difficult to evaluate the influence when the radioactive waste density and the radioactivity concentration distribution in the container are biased.

The technique described in Patent Literature 2 is a measurement device mainly for a rectangular container, but the radioactive waste density used in the evaluation uses a uniform average density in the container. Furthermore, the technique of the literature is evaluated on the assumption that the radioactivity concentration in the container is almost uniform. Therefore, the technique of the document has a problem that the above-described evaluation error increases.
Further, the technique described in Patent Document 3 evaluates the radioactivity concentration based on the influence from the divided small areas. Although the technique of this document takes into account the radioactivity concentration distribution, the radioactivity is evaluated assuming that the radioactivity in a small area is the maximum value, so that the radioactivity concentration and the like are overestimated.

The apparatus described in Patent Document 4 is a measurement / evaluation method in consideration of the radioactivity concentration distribution, so that the evaluation accuracy is improved (evaluation error is reduced), but the size of the small area set for evaluation is Is rough, there is a problem that the radioactivity concentration distribution in the small area is not considered. Further, when the size of the small region is further subdivided in order to evaluate the radioactivity concentration distribution in more detail, there is a problem that the calculation time in the evaluation increases.
The present invention has been made in view of the above circumstances, and has as its object to provide a radioactivity concentration evaluation system and a radioactivity concentration evaluation method capable of evaluating a radioactivity concentration distribution with high accuracy in a short calculation time.

  In order to solve the above-mentioned problems, a radioactivity concentration evaluation system according to the present invention includes: an analysis unit that calculates a first gamma ray spectrum based on a three-dimensional model of a measurement target stored in a container; Before storing, a screening measurement unit that obtains radiation measurement data that is measurement data of radiation distribution in the measurement object, and a plurality of measurement units arranged around the container after storing the measurement object in the container. Concentration distribution evaluation in a container for evaluating a radioactivity concentration distribution in the container based on an actually measured gamma ray spectrum corresponding to the first gamma ray spectrum and actually measured using a gamma ray detector, and the radiation measurement data. And a unit.

  According to the present invention, the radioactivity concentration distribution can be evaluated with high accuracy in a short calculation time.

It is a perspective view which shows an example of the container and the measurement object which are assumed to be used. FIG. 3 is a schematic diagram of a three-dimensional model of a container storing a measurement target. It is a schematic diagram of another three-dimensional model of the container which stores the measurement object. It is a block diagram of a radioactivity concentration evaluation system according to a first embodiment of the present invention. FIG. 9 is an operation explanatory diagram of an operation of calculating measurement model data after correction and the like in an evaluation unit. It is a block diagram of a radioactivity concentration evaluation system by a 2nd embodiment. It is a block diagram of the radioactivity concentration evaluation system by a 3rd embodiment.

[First Embodiment]
<Measurement object and model data>
First, a measurement object and model data applied to the first embodiment and other embodiments described later will be described.
FIG. 1 is a perspective view illustrating an example of the container 41 and the measurement target 24 that are assumed to be used. The measurement object 24 is, for example, radioactive waste. Actual measurement objects have various shapes, but for simplicity of description, FIG. 1 shows a rectangular plate as an example.
The container 41 is formed in a substantially rectangular parallelepiped box shape, and accommodates a plurality of plate-shaped measurement objects 24 therein. In the illustrated example, the container 41 has a cubic box shape of 1 m (meter) × 1 m × 1 m.
A plurality of gamma ray detectors 47 are arranged on the outer surface of the container 41. These gamma ray detectors 47 detect gamma rays at the respective locations.

FIG. 2 is a schematic diagram of model data 16 (a three-dimensional model) expressing a three-dimensional model of the container 41 and the measurement target 24 (see FIG. 1).
2, the model data 16 includes a container model 141 that is a model of the container 41 and a measurement object model 124 that is a model of the measurement object 24. The gamma ray detector model 17 which is a model of the gamma ray detector 47 added to the model data 16 is called measurement model data 36. A virtual area divided from the measurement object model 124 by the boundary L1 indicated by a broken line in the drawing is referred to as “virtual divided area 61”. FIG. 2 shows, as an example, a virtual divided area 61 (grouped virtual area) obtained by dividing the measurement object model 124 into 3 × 3 = 9 areas.

  When analyzing the radioactivity concentration distribution using the measurement model data 36, a radiation source model using one virtual divided region 61 as a volume radiation source is assumed. Then, a calculated gamma ray spectrum 68 in the gamma ray detector model 17 is obtained based on these radiation source models. The calculated gamma ray spectrum 68 is represented as a two-dimensional graph in which the energy on the horizontal axis is associated with the count rate on the vertical axis, as shown in the figure.

  FIG. 3 is a schematic diagram of the subdivided model data 18 (a three-dimensional model) that is another model data of the measurement target 24 (see FIG. 1) stored in the container 41. The subdivision model data 18 includes a container model 141 and a subdivision measurement object model 134. That is, in the segmented model data 18, a segmented measurement object model 134 is applied instead of the measurement object model 124 in FIG. The data obtained by adding the gamma ray detector model 17 to the segmented model data 18 is referred to as segmented measurement model data 38.

  In the subdivision measurement object model 134, each of the virtual subdivided regions 61 is divided into four (6 × 6 = 36 in total) subdivided virtual along the boundary L2 which further subdivides the virtual subdivided region 61 vertically and horizontally. It is divided into divided regions 63 (virtual regions). When analyzing the radioactivity concentration distribution using the subdivision model data 18, a radiation source model using one subdivision virtual division region 63 as a volume source is assumed. Then, based on these radiation source models, a subdivided calculation gamma ray spectrum 65 (first gamma ray spectrum) in the gamma ray detector model 17 is obtained. Similar to the above-described calculated gamma ray spectrum 68 (see FIG. 2), the subdivided calculated gamma ray spectrum 65 is expressed as a two-dimensional graph in which the energy on the horizontal axis is associated with the count rate on the vertical axis.

Here, the reason why the model data 16 and the segmented model data 18 are used together will be described.
First, in FIG. 3, it is assumed that the radioactivity concentration in each radiation source model (virtual division area 61 or subdivided virtual division area 63) is set, and thereby the calculated gamma ray spectrum in each gamma ray detector model 17 is obtained. View. The amount of calculation for obtaining the calculated gamma ray spectrum is substantially proportional to the number of each radiation source model (61 or 63). Therefore, even if the number of radiation source models increases, the amount of calculation does not increase so much. In such a case, as shown in FIG. 3, it is preferable to employ the subdivision measurement model data 38 in which the subdivision virtual divided region 63 is a radiation source model. Thereby, an accurate subdivision calculation gamma ray spectrum 65 can be obtained.

  Next, the radioactivity concentration of the radiation source model (61 or 63) is evaluated (that is, estimated) based on the gamma ray spectrum actually measured by the gamma ray detector 47 (see FIG. 1) (hereinafter referred to as an actually measured gamma ray spectrum). ) Let's assume the case. In performing this evaluation, for example, an analysis method based on the Monte Carlo method is applied. That is, the calculated gamma ray spectrum in each gamma ray detector model 17 is calculated while randomly changing the radioactivity concentration in each radiation source model, and the measured gamma ray spectrum is approximated from the calculated gamma ray spectrums calculated a plurality of times. An object (for example, an object that is close enough to fall within a predetermined allowable range) is selected.

  As a method for evaluating the radioactivity concentration in each radiation source model (61 or 63), an analysis method other than the Monte Carlo method can be adopted. However, in various analysis methods known today, the required amount of calculation increases exponentially as the number of radiation source models increases. Therefore, when performing such an evaluation, it is preferable to suppress the number of radiation source models to a degree that can be calculated in real time, such as when dismantling a nuclear power plant. For example, as shown in FIG. 2, it is preferable to adopt the measurement model data 36 in which the virtual divided region 61 is a radiation source model, and to suppress the calculation time.

<FIG. 4: Overall Configuration of First Embodiment>
FIG. 4 is a block diagram of the radioactivity concentration evaluation system 1 according to the first embodiment of the present invention.
In FIG. 4, the radioactivity concentration evaluation system 1 includes an analysis unit 101 (analysis process), a screening measurement unit 201 (screening measurement process), a measurement object storage unit 301, an in-container concentration distribution measurement unit 401, A concentration distribution evaluation section 501 (in-container concentration distribution evaluation process).

  Here, the analyzing unit 101 and the in-container concentration distribution evaluating unit 501 are general computers such as a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an HDD (Hard Disk Drive). The HDD stores an OS (Operating System), application programs, various data, and the like. The OS and the application programs are expanded in the RAM and executed by the CPU. In FIG. 4, functions realized by an application program or the like are shown as blocks in the analysis unit 101 and the inside of the container concentration distribution evaluation unit 501.

(Analysis unit 101)
The analysis unit 101 performs various analyzes prior to the operation of the screening measurement unit 201 and the concentration distribution measurement unit 401 in the container, which will be described later, in evaluating the radioactivity concentration in the container.
The analysis unit 101 includes a plant dismantling plan support system 11 (dismantling support system), a model database 12, an analysis condition input unit 13, a gamma ray spectrum analysis unit 14, and a calculated gamma ray spectrum storage unit 15.

  Here, the plant dismantling plan support system 11 supports the formulation of an execution plan for decommissioning of a nuclear power plant, other plants, and the like. The plant dismantling plan support system 11 calculates the size of waste generated by dismantling, that is, the measurement target 24. The model database 12 is a database that stores data created by the plant demolition plan support system 11. That is, the model database 12 stores various subdivided model data 18 (see FIG. 3) corresponding to the measurement object 24 having various shapes and the container 41 (see FIG. 1) storing the same. The subdivided model data 18 (see FIG. 3) stored in the model database 12 is created on the assumption that the subdivided virtual divided region 63 as each radiation source model has a uniform radioactivity concentration. Have been.

  The analysis condition input unit 13 reads out the subdivided model data 18 from the model database 12 and adds the gamma ray detector model 17 to this to generate subdivided measurement model data 38 (see FIG. 3). In other words, the analysis condition input unit 13 determines the analysis condition by adding the gamma ray detector model 17 to the segmented model data 18. The gamma ray spectrum analysis unit 14 analyzes the segmentation measurement model data 38 based on the analysis conditions determined by the analysis condition input unit 13. Specifically, a subdivision calculation gamma ray spectrum 65 in each gamma ray detector model 17 is calculated. The calculated gamma ray spectrum storage unit 15 stores the subdivided calculated gamma ray spectrum 65, which is the analysis result of the gamma ray spectrum analysis unit 14, and the corresponding subdivided measurement model data 38.

  Generally, in a decommissioning of a nuclear power generation facility or the like, in a measurement performed to confirm a radioactive concentration of radioactive waste, a gamma nuclide to be measured is usually Co-60 or Cs-137. . For this reason, the calculated gamma ray spectrum analysis of the present system also targets Co-60 or Cs-137. However, if measurement is possible, the calculated gamma ray spectrum may be analyzed for other gamma ray nuclides. Similarly, the measured gamma ray spectrum is also targeted for Co-60 or Cs-137, but if it can be measured, the measured gamma ray spectrum may be measured for other gamma nuclides. However, the gamma ray spectrum to be calculated by the analysis unit 101 and the gamma ray nuclide to be measured by the in-vessel concentration distribution measurement unit 401 described later are the same.

  In the above example, the subdivision model data 18 of the measurement target is created by the plant dismantling plan support system 11. However, the segmented model data 18 may be three-dimensional model data created by ordinary three-dimensional CAD software, as long as the segmented model data 18 is created before the screening measurement unit 201 and the concentration distribution measurement unit in the container described below. . Since the operation of the analysis unit 101 described above is independent of the operation of the screening measurement unit 201, the in-container concentration distribution measurement unit 401, and the like, it can be completed in advance before the dismantling operation. As described above, if the segmentation measurement model data 38 and the segmentation calculation gamma ray spectrum 65 are obtained before the disassembly operation, the operation time of the analysis unit 101 has almost no effect on the time required for the disassembly operation. .

  However, the segmentation measurement model data 38 and the segmentation calculation gamma ray spectrum 65 do not necessarily need to be obtained in advance. That is, when the measurement target 24 is cut out during the disassembly work, before storing the measurement target 24 in the container 41, three-dimensional shape measurement using a laser shape measurement, a stereo camera, or the like is performed. The subdivision model data 18, the subdivision measurement model data 38, and the subdivision calculation gamma ray spectrum 65 may be calculated based on the subdivision model data 18, the subdivision measurement model data 38, and the subdivision calculation gamma ray spectrum 65. As described above, when the segmented model data 18 and the like are configured based on the actual shape of the measurement target 24, accurate segmented model data 18 can be obtained.

(Screening measurement unit 201)
The screening measurement unit 201 performs screening measurement of radiation such as surface contamination of the measurement target 24 before storing the measurement target 24 in the container 41.
4, the screening measurement unit 201 includes a screening measurement device 21, a data collection unit 22, a screening measurement result storage unit 23, and a belt conveyor 25.

  The screening measurement device 21 measures the radiation concentration distribution of the measurement object 24. In addition, the data collection unit 22 collects measurement data obtained by the screening measurement device 21. In addition, the screening measurement result storage unit 23 stores the collected measurement data as screening measurement data 70 (radiation measurement data). Here, the screening measurement data 70 represents the radiation density of each part of the measurement target 24 with the size (spatial resolution) corresponding to the subdivided virtual divided region 63 (see FIG. 3) as a unit. In other words, in FIG. 3, the size of the subdivided virtual divided region 63 can be reduced to the resolution of the screening measurement device 21.

  The belt conveyor 25 transports the measurement target 24. As described above, when the measurement target 24 is transported by the belt conveyor 25, the position of the screening measurement device 21 can be fixed, and the efficiency of the measurement operation can be improved. When the belt conveyor 25 transports the measurement target 24 to the installation position of the screening measurement device 21, the screening measurement is performed by the screening measurement device 21. It is preferable that the screening measurement device 21 can collectively measure a wide range at a high spatial resolution from the viewpoint of throughput.

  In the present embodiment, the screening measuring instrument 21 has a pair of plastic scintillating fibers (PSFs) that can collectively measure a range of about 10 m to 20 m and is arranged so as to sandwich the passage of the measurement target 24. It is. Thereby, the screening measurement device 21 can simultaneously measure the radiation concentration on the front surface and the back surface of the measurement target 24. In order to shorten the measurement time, it is preferable to arrange two PSFs as described above. However, the front and back surfaces of the measurement target 24 may be sequentially measured using one PSF. Thereby, the screening measurement unit 201 can be configured at low cost.

  The screening measuring instrument 21 using the PSF generally measures a count rate representing the number of gamma rays incident on the measuring instrument in a unit time. The screening measuring device 21 converts the measured counting rate into a radioactivity using a conversion coefficient obtained in advance. Here, the conversion coefficient is obtained by a simulation, an experiment, or the like, based on the shape of the measurement target 24 or the distribution state of the radiation source, and the relationship between the radioactivity and the counting rate.

  However, the screening measurement device 21 is not limited to the configuration shown in FIG. 4, and may be, for example, radiation detectors arranged in a two-dimensional matrix. Further, the radiation concentration distribution of the measurement target 24 does not necessarily need to be measured collectively. Therefore, the screening measurement device 21 may scan a survey meter or a one-dimensional array of radiation detectors (not shown) along the measurement target 24. Further, as the screening measurement device 21, a handheld measurement device held by an operator may be applied. Thereby, the screening measuring device 21 and the screening measuring unit 201 can be constructed economically.

(Measurement object storage unit 301)
In the measurement object storage section 301, the measurement object 24 is stored in the container 41. Here, the measurement object 24 to be stored is an object whose radiation concentration distribution has already been measured by the screening measurement unit 201.

(Concentration distribution measuring unit 401 in the container)
The container 41 in which the measurement object 24 is stored in the measurement object storage unit 301 is supplied to the in-container concentration distribution measurement unit 401. As described above, in the in-container concentration distribution measuring unit 401, a plurality of gamma ray detectors 47 are arranged on the outer surface of the container 41 in which the measurement target 24 is stored. Then, in that state, the gamma ray originating from the measurement target 24 is measured by the gamma ray detector 47.

The in-container concentration distribution measurement unit 401 includes a gamma ray spectrum collection unit 48 and an actually measured gamma ray spectrum storage unit 49, in addition to the above-described gamma ray detector 47. The gamma ray spectrum collecting section 48 collects the measurement data of the gamma ray detectors 47 and outputs the measured gamma ray spectra 72 of each gamma ray detector 47. Then, the measured gamma ray spectrum storage unit 49 stores the measured gamma ray spectrum 72. These measured gamma ray spectra 72 are expressed as two-dimensional graphs in which the energy on the horizontal axis is associated with the count rate on the vertical axis, similarly to the above-described segmentation calculation gamma ray spectrum 65 (see FIG. 3).
The installation position of the gamma ray detector 47 is not limited to the outer surface of the container 41 as long as the relative positional relationship with the container 41 can be grasped.

(Concentration distribution evaluation unit 501 in the container)
The in-vessel concentration distribution evaluation unit 501 evaluates the radioactivity concentration distribution and the radioactivity concentration in the container 41 based on the analysis results of the analysis unit 101, the screening measurement unit 201, and the in-vessel concentration distribution measurement unit 401. . The in-container concentration distribution evaluation unit 501 includes a calculated gamma ray spectrum correction unit 51, an evaluation condition input unit 52, an evaluation unit 53, and an output unit 54.

  The calculation gamma ray spectrum correction unit 51 receives the segmentation measurement model data 38 and the segmentation calculation gamma ray spectrum 65 from the analysis unit 101. Further, the screening measurement data 70 is input from the screening measurement unit 201 to the calculated gamma ray spectrum correction unit 51. The calculated gamma ray spectrum correction unit 51 performs a correction process on the subdivision measurement model data 38 based on the screening measurement data 70, and outputs the result as corrected subdivision measurement model data 138.

  The details of this correction processing will be described below. First, the subdivision measurement model data 38 and the subdivision calculation gamma-ray spectrum 65 supplied to the calculation gamma ray spectrum correction unit 51 have the same radioactivity in the subdivision virtual division region 63 (see FIG. 3) as each radiation source model. It is calculated assuming that it has a concentration. On the other hand, the screening measurement data 70 represents the actual radiation density of each part of the measurement target 24 in units of a size corresponding to the subdivided virtual divided region 63 (see FIG. 3).

  The calculated gamma ray spectrum correction unit 51 gives the radioactivity concentration according to the screening measurement data 70 to each of the subdivided virtual divided regions 63 in the subdivision measurement model data 38, and corrects the result to obtain the corrected subdivision measurement model data. 138 is output. Further, the calculated gamma ray spectrum correction unit 51 calculates a gamma ray spectrum in each gamma ray detector model 17 included in the corrected segmentation measurement model data 138. The gamma ray spectrum calculated in this manner is referred to as “corrected gamma ray spectrum 66 (second gamma ray spectrum)”. In other words, the calculated gamma ray spectrum correction unit 51 calculates the corrected gamma ray spectrum 66 by correcting the segmented calculation gamma ray spectrum 65 based on the screening measurement data 70.

  The post-correction segmentation measurement model data 138, the post-correction gamma ray spectrum 66, and the actually measured gamma ray spectrum 72 are input to the evaluation condition input unit 52. The evaluation condition input unit 52 determines various evaluation conditions based on the input data, and evaluates the determined evaluation conditions, the corrected gamma ray spectrum 66, and the corrected fragmentation measurement model data 138, into an evaluation unit 53. To supply. The evaluation unit 53 evaluates the radioactivity concentration in the container 41 and the radioactivity concentration distribution of the container 41 and the measurement target 24 based on the input evaluation conditions and the like.

  As described above, the amount of calculation for the evaluation performed by the evaluation unit 53 increases exponentially as the number of radiation source models (virtual division areas 61 or subdivided virtual division areas 63) increases. The post-correction subdivision measurement model data 138 supplied via the evaluation condition input unit 52 uses the subdivision virtual sub-region 63 (see FIG. 3) as the radiation source model, so that the calculation amount becomes excessive as it is. . Therefore, the evaluation unit 53 converts the corrected segmented measurement model data 138 into corrected measurement model data 136 using the virtual divided region 61 as a radiation source model. At this time, it is preferable that the size of the virtual divided region 61 is such that the evaluation unit 53 can evaluate the radioactivity concentration distribution and radioactivity concentration of the measurement object 24 and the container 41 in real time.

FIG. 5 is an operation explanatory diagram of the operation of calculating the corrected measurement model data and the like in the evaluation unit 53.
In FIG. 5, the segmentation calculation gamma ray spectrum 65 is calculated by the analysis unit 101 (see FIG. 4). As described above, the subdivision calculation gamma ray spectrum 65 is calculated on the assumption that the subdivision virtual division region 63 (see FIG. 3) as each radiation source model has a uniform radioactivity concentration. Things. The corrected gamma ray spectrum 66 is included in the above-described corrected segmentation measurement model data 138 (see FIG. 4). The corrected gamma ray spectrum 66 is a gamma ray spectrum when the radioactivity density corresponding to the actual density distribution in the measurement target 24 is assigned to the subdivided virtual divided area 63.

  The corrected total calculated gamma ray spectrum 67 (third gamma ray spectrum) is a gamma ray spectrum corresponding to the radiation source model in the corrected measurement model data 136, that is, the virtual divided region 61 (see FIG. 3). In the example shown in FIG. 3, one virtual divided area 61 is divided into four subdivided virtual divided areas 63. Thus, the average value of the radioactivity concentrations of these four subdivided virtual divided regions 63 may be set as the radioactivity concentration of the virtual divided region 61 in the corrected measurement model data 136. Further, a graph of the average value of the corrected gamma ray spectrum 66 corresponding to these four subdivided virtual divided regions 63 may be obtained, and the result may be adopted as the corrected total calculated gamma ray spectrum 67.

  Referring back to FIG. 4, the evaluation unit 53 evaluates the actually measured gamma ray spectrum 72 while changing the radioactivity concentration to be assigned to the virtual divided region 61 using the corrected measurement model data 136 as an initial value. That is, the radioactivity concentration distribution of the virtual divided region 61 that realizes the actually measured gamma ray spectrum 72 is calculated, and the radioactivity concentration in the container 41 is obtained. As described above, in the evaluation unit 53, for example, an analysis method based on the Monte Carlo method is applied. That is, a gamma ray spectrum is calculated while randomly changing the radioactivity concentration in each radiation source model, and a gamma ray spectrum calculated over a plurality of times is approximated to an actually measured gamma ray spectrum (for example, within a predetermined allowable range). That are close enough to fit in the list).

  However, also in the Monte Carlo method or the like, if a value with high accuracy is given as an initial value of each radiation source model (that is, the virtual divided region 61), the time until the evaluation converges can be shortened. In the present embodiment, since the initial value of the corrected measurement model data 136 is determined based on the screening measurement data 70 that is the actual measurement value of the radioactivity concentration of the measurement target 24, the corrected measurement model data 136 is At the stage of the initial value, the accuracy is considerably high. Therefore, the evaluation unit 53 quickly converges the evaluation of the radioactivity concentration distribution and the radioactivity concentration of the container 41 and the measurement target 24, and can realize high work efficiency.

  The evaluation result of the radioactivity concentration evaluated by the evaluation unit 53 is referred to as “radioactivity concentration evaluation value”. The evaluation result of the radioactivity concentration distribution evaluated by the evaluation unit 53 is referred to as “radioactivity concentration distribution evaluation result”. The output unit 54 displays the radioactivity concentration evaluation value and the radioactivity concentration distribution evaluation result supplied from the evaluation unit 53 on a display or the like in the form of numbers, graphs, figures, and the like.

<Effect of First Embodiment>
As described above, the radioactivity concentration evaluation system (1) of the present embodiment uses the first gamma ray spectrum (65) based on the three-dimensional model (18) of the measurement object (24) stored in the container (41). The analysis unit (101) that calculates the measurement target and the radiation measurement data (70) that is the radiation measurement measurement data of the measurement target (24) are acquired before the measurement target (24) is stored in the container (41). The measurement is performed using a screening measurement unit (201) and a plurality of gamma ray detectors (47) arranged around the container (41) after the measurement target (24) is stored in the container (41), and the first measurement is performed. Concentration distribution evaluation in the container for evaluating the radioactivity concentration distribution in the container (41) based on the actually measured gamma ray spectrum (72) corresponding to the gamma ray spectrum (65) and the radiation measurement data (70) And (501), and a.

  Thereby, the in-container concentration distribution evaluation section (501) can evaluate the radioactivity concentration distribution in the container (41) based on the actually measured gamma ray spectrum (72), and thus the radioactivity concentration can be accurately calculated in a short calculation time. The concentration distribution can be evaluated.

Further, according to the present embodiment, the gamma ray spectrum correction unit (51) that calculates the second gamma ray spectrum (66) by correcting the first gamma ray spectrum (65) based on the radiation measurement data (70). The container concentration distribution evaluator (501) is configured to measure the measured gamma ray spectrum (72), the measured radiation data (70), and the second gamma ray spectrum (66) based on the measured gamma ray spectrum (72) and the second gamma ray spectrum (66). Evaluate the radioactivity concentration distribution.
As a result, the in-vessel concentration distribution evaluation unit (501) evaluates the radioactivity concentration distribution in the container (41) using the second gamma ray spectrum (66) calculated based on the radiation measurement data (70). Therefore, the radioactivity concentration distribution can be evaluated with high accuracy in a shorter calculation time.

Further, according to the configuration in which the screening measurement unit (201) includes the handheld measurement device held by the worker, the screening measurement unit (201) can be economically constructed.
In addition, according to the aspect in which the distribution of radiation emitted from the measurement target (24) is measured at a predetermined spatial resolution as the screening measurement unit (201), the distribution of radiation can be accurately measured.
As a three-dimensional model (18) of the measurement object (24), a model obtained by measuring the shape of the measurement object (24) before storing the measurement object (24) in the container (41). According to the aspect where is applied, it is possible to apply the three-dimensional model (18) reflecting the accurate shape of the measurement target (24).

According to the aspect in which a three-dimensional model (18) of the measurement target (24) is output by a disassembly support system that supports a dismantling plan of the device, there is no actual measurement target (24). Even in the state, the three-dimensional model (18) can be constructed, and the analysis can be performed efficiently.
In the first gamma ray spectrum (65) and the measured gamma ray spectrum (72), the target gamma nuclide is Co-60 or Cs-137. Thereby, the radioactivity concentration can be evaluated corresponding to the main gamma-ray nuclides.

The analysis unit (101) divides the model (134) of the measurement target (24) in the three-dimensional model (18) into a plurality of virtual regions (63), and individually divides the plurality of virtual regions (63) into radiations. The first gamma ray spectrum (65) is calculated as a source, and the screening measurement unit (201) measures the radiation dose of a portion corresponding to each virtual region (63) in the measurement target (24). Is output as radiation actual measurement data (70), and the in-container concentration distribution evaluator (501) corrects the first gamma ray spectrum (65) based on the radiation actual measurement data (70), and corrects the second gamma ray spectrum. (66) is generated.
This makes it possible to generate a highly accurate second gamma ray spectrum (66) based on the radiation measurement data (70).

The in-container concentration distribution evaluation unit (501) performs an average calculation on the second gamma ray spectrum (66) based on the count value of the gamma ray corresponding to the virtual area (63) or the ratio of the count rate per unit time. As a result, a third gamma ray spectrum (67) corresponding to the grouped virtual area (61) obtained by grouping the virtual areas (63) is obtained.
In this way, by applying the grouped virtual area (61) obtained by grouping the virtual areas (63), the calculation time in the in-concentration distribution evaluation unit (501) can be reduced.

  Further, the content of the above-described radioactivity concentration evaluation system (1) can be considered to be a “radioactivity concentration evaluation method” having a series of processes. That is, the radioactivity concentration evaluation method according to the present embodiment uses an analysis process of calculating the first gamma ray spectrum (65) based on the three-dimensional model (18) of the measurement object (24) stored in the container (41). (101) and a screening measurement step (201) of acquiring radiation measurement data (70) which is radiation measurement data of the measurement target (24) before storing the measurement target (24) in the container (41). ) And a step of actually measuring an actually measured gamma ray spectrum (72) using a plurality of gamma ray detectors (47) arranged around the container (41) after storing the measurement object (24) in the container (41). A container concentration distribution evaluation step (501) for evaluating the radioactivity concentration distribution in the container (41) based on the measured gamma ray spectrum (72) and the measured radiation data (70). And it has a.

[Second embodiment]
<Configuration of Second Embodiment>
FIG. 6 is a block diagram of the radioactivity concentration evaluation system 2 according to the second embodiment of the present invention. In the following description, portions corresponding to the respective portions of the first embodiment are denoted by the same reference numerals, and description thereof may be omitted.

6, the radioactivity concentration evaluation system 2 includes an analysis unit 101, a screening measurement unit 201, a measurement target storage unit 301, and a radioactivity concentration evaluation system 1 (see FIG. 4) in the first embodiment. The apparatus includes an in-container concentration distribution measuring unit 401 and an in-container concentration distribution evaluation unit 501.
The radioactivity concentration evaluation system 2 according to the present embodiment further includes a refilling process determining unit 81 (processing determining unit).

  The refilling process determination unit 81 determines whether the radioactivity concentration evaluation value supplied from the evaluation unit 53 is equal to or less than a predetermined radioactivity concentration reference value. Further, the refilling process judging unit 81 refills the measurement object 24 stored in the container 41 when the judgment result is negative (the radioactivity concentration evaluation value exceeds the radioactivity concentration reference value). The information to be instructed (called refill instruction information) is output. Here, the radioactivity concentration reference value is determined based on a radioactivity concentration level specified in advance for the container 41.

  When the refilling process determining unit 81 outputs the refilling instruction information, the refilling instruction information is notified to the plant dismantling plan support system 11. In response, the plant demolition plan support system 11 changes the correspondence between the container 41 and the measurement target 24 and re-evaluates the measurement target 24 stored in the container 41 based on the changed correspondence. Execute After the re-evaluation has been performed, the analysis unit 101 re-executes the processes after the model database 12. Further, the refill instruction information output by the refill process determination unit 81 is also supplied to the measurement object storage unit 301. Thereby, the actual refilling operation is performed in the measurement object storage section 301.

  As described above, the case where the refill process determination unit 81 outputs the refill instruction information is the case where the radioactivity concentration evaluation value exceeds the radioactivity concentration reference value. In such a case, the plant demolition plan support system 11 specifies the measurement target 24 having a high radioactivity level based on the screening measurement data 70 output from the screening measurement unit 201. Then, the plant dismantling plan support system 11 changes the correspondence between the container 41 and the measurement target 24 so that the specified measurement target 24 is replaced with the measurement target 24 having a lower radioactivity level.

<Effect of Second Embodiment>
As described above, the radioactivity concentration evaluation system (2) of the present embodiment has the same configuration as the radioactivity concentration evaluation system (1) of the first embodiment, so that the measurement stored in the container (41) is possible. Even when the radioactivity concentration distribution exists in the object (24), the radioactivity concentration distribution and the radioactivity concentration can be evaluated with high accuracy without increasing the calculation time in the evaluation.

  Further, according to the present embodiment, it is determined whether the radioactivity concentration evaluation value is equal to or less than a predetermined radioactivity concentration reference value, and if the judgment result is negative, the measurement object (24) is refilled. And a process determining unit (81) for outputting information instructing the user. Thereby, even when the radioactivity concentration evaluation value exceeds the radioactivity concentration reference value, the worker can feed back information based on the judgment result of the processing judgment unit (81) and the like, The object (24) can be refilled, and the object to be measured (24) can be stored in the container (41) at a radioactivity concentration lower than the radioactivity concentration reference value.

[Third embodiment]
FIG. 7 is a block diagram of the radioactivity concentration evaluation system 3 according to the third embodiment of the present invention. In the following description, portions corresponding to the respective portions of the above-described other embodiments are denoted by the same reference numerals, and description thereof may be omitted.
In FIG. 7, the radioactivity concentration evaluation system 3 includes an analysis unit 101, a screening measurement unit 221, a measurement object storage unit 301, a concentration distribution measurement unit 401 in a container, and a concentration distribution evaluation unit 501 in a container. ing. That is, the radioactivity concentration evaluation system 3 includes a screening measurement unit 221 instead of the screening measurement unit 201 in the radioactivity concentration evaluation system 1 (see FIG. 4) in the first embodiment.

  In the screening measurement unit 221 of the present embodiment, the measurement target is the pre-dismantling structure 26 before being cut out as the measurement target 24. In the illustrated example, the pre-dismantling structure 26 is a wall-like structure that is installed in the vertical direction. The screening measurement device 21 is the same as that of the first embodiment (see FIG. 4), but in this embodiment, the screening measurement device 21 is mounted on the lifting device 27. The lifting device 27 raises and lowers the screening measurement device 21 along the surface of the pre-dismantling structure 26. Accordingly, the data collection unit 22 performs the screening measurement corresponding to the cut out measurement target 24 (see FIG. 1) based on the measurement result by the screening measurement device 21 and the elevation position of the screening measurement device 21. The data 70 is output.

  In the example shown in FIG. 7, the pre-dismantling structure 26 is installed in the vertical direction, but the pre-dismantling structure 26 may be installed in the horizontal direction. In this case, the screening measurement data 70 can be acquired while moving the screening measurement device 21 in the horizontal direction. As shown in the figure, when the PSF is applied as the screening measurement device 21, since the shape of the PSF is rich in flexibility, accurate screening measurement data 70 is obtained even if the shape of the pre-demolition structure 26 is complicated. be able to. The pre-disassembly structure 26 may be a structure that has not been dismantled at all, or may be a structure that has been partially dismantled. That is, any structure having a volume larger than at least the volume of the container 41 or a structure wider than the frontage of the container 41 can be applied as the pre-disassembly structure 26.

<Effect of Third Embodiment>
As described above, according to the present embodiment, the measurement object (24) has a larger volume than the volume of the container (41), or has a wider width than the frontage of the container (41). The object (26) was divided, and a measuring device for acquiring radiation measurement data (70) of the pre-dismantling structure (26) was applied to the screening measurement unit (201).
In this way, by performing the screening measurement of the pre-demolition structure (26), when the measurement target (24) is generated in the process of dismantling the pre-demolition structure (26), the measurement target (24) Can be immediately stored in the container (41), and the throughput can be further improved.

[Modification]
The present invention is not limited to the embodiments described above, and various modifications are possible. The above-described embodiments are exemplarily illustrated for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described above. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of one embodiment can be added to the configuration of another embodiment. Further, a part of the configuration of each embodiment can be deleted, or another configuration can be added or replaced. Further, the control lines and information lines shown in the drawing indicate those which are considered necessary for the description, and do not necessarily indicate all the control lines and information lines necessary for the product. In fact, it may be considered that almost all components are interconnected. Possible modifications to the above embodiment are, for example, as follows.

(1) Since the hardware of the analyzing unit 101 and the in-container concentration distribution evaluating unit 501 in each of the above embodiments can be realized by a general computer, a program or the like for realizing these functions is stored in a storage medium, or a transmission It may be distributed via.

(2) In the above embodiments, the processing executed in the analysis unit 101 and the in-container concentration distribution evaluation unit 501 has been described as software processing using a program. An application specific integrated circuit (IC) or a hardware-based process using an FPGA (field-programmable gate array) may be used.

1,2,3 Radioactivity concentration evaluation system 11 Plant dismantling plan support system (dismantling support system)
16 Model data (3D model)
18 Subdivision model data (3D model)
24 Measurement object 26 Structure before dismantling 41 Container 47 Gamma ray detector 51 Calculated gamma ray spectrum correction unit (gamma ray spectrum correction unit)
52 Evaluation condition input unit 53 Evaluation unit 54 Output unit 61 Virtual divided area (grouped virtual area)
63 Subdivision virtual division area (virtual area)
65 Subdivision calculation gamma ray spectrum (first gamma ray spectrum)
66 Gamma ray spectrum after correction (second gamma ray spectrum)
67 Total calculated gamma ray spectrum after correction (third gamma ray spectrum)
68 Calculated gamma ray spectrum 70 Screening measurement data (actual radiation measurement data)
72 Actual gamma ray spectrum 81 Radioactivity concentration evaluation result comparison / processing judgment device (processing judgment unit)
101 Analysis unit (analysis process)
134 Subdivision measurement object model (model)
201, 221 Screening measurement section (screening measurement process)
501 Concentration Distribution Evaluation Unit in Container (Concentration Distribution Evaluation Process in Container)

Claims (12)

An analysis unit that calculates a first gamma-ray spectrum based on a three-dimensional model of the measurement object stored in the container;
Before storing the measurement target in the container, a screening measurement unit that acquires radiation measurement data that is measurement data of radiation distribution in the measurement target,
The measured gamma ray spectrum corresponding to the first gamma ray spectrum and measured using a plurality of gamma ray detectors arranged around the container after storing the measurement target in the container, and the radiation measured data. And a container concentration distribution evaluation unit for evaluating the concentration distribution of radioactivity in the container based on the following. A gamma-ray spectrum correction unit that calculates a second gamma-ray spectrum by correcting the first gamma-ray spectrum based on the radiation measurement data,
The said concentration distribution evaluation part in a container evaluates the radioactivity concentration distribution in the said container based on the said measured gamma ray spectrum, the said radiation measurement data, and the said 2nd gamma ray spectrum. Item 4. The radioactivity concentration evaluation system according to Item 1. The radioactivity concentration evaluation system according to claim 1, wherein the screening measurement unit includes a handheld measurement device held by an operator. The radioactivity concentration evaluation system according to claim 1, wherein the screening measurement unit measures a distribution of radiation emitted from the measurement target at a predetermined spatial resolution. The three-dimensional model of the measurement object is a model obtained by measuring the shape of the measurement object before storing the measurement object in the container. The radioactivity concentration evaluation system according to any one of the above. The radioactivity concentration evaluation according to any one of claims 1 to 4, wherein the three-dimensional model of the measurement object is output by a disassembly support system that supports a dismantling plan of equipment. system. An evaluation unit that evaluates the radioactivity concentration in the container and outputs a radioactivity concentration evaluation value that is a result thereof,
A process determining unit that determines whether the radioactivity concentration evaluation value is equal to or less than a predetermined radioactivity concentration reference value, and outputs information instructing refilling of the measurement target when the result of the determination is negative. The radioactivity concentration evaluation system according to any one of claims 1 to 6, further comprising: The measurement object has a volume larger than the volume of the container, or is a material obtained by dividing the pre-disassembly structure having a width wider than the frontage of the container,
The radioactivity concentration evaluation system according to any one of claims 1 to 6, wherein the screening measurement unit is a measurement device that acquires the radiation measurement data of the structure before dismantling. The radioactive concentration evaluation according to any one of claims 1 to 8, wherein a target gamma ray nuclide is Co-60 or Cs-137 in the first gamma ray spectrum and the actually measured gamma ray spectrum. system. The analysis unit divides the model of the measurement target in the three-dimensional model into a plurality of virtual regions, and calculates the first gamma ray spectrum using the plurality of virtual regions individually as radiation sources.
The screening measurement unit is to output a measurement result of a radiation dose of a portion corresponding to each of the virtual regions in the measurement target as the radiation measurement data,
The radioactivity concentration evaluation system according to claim 2, wherein the in-container concentration distribution evaluation unit corrects the first gamma ray spectrum based on the radiation measurement data to generate the second gamma ray spectrum. . The in-container concentration distribution evaluation unit performs an average calculation on the second gamma ray spectrum based on a count value of a gamma ray corresponding to the virtual area or a ratio of a count rate per unit time, thereby calculating the virtual area. The radioactivity concentration evaluation system according to claim 10, wherein a third gamma ray spectrum corresponding to the grouped virtual region is obtained. An analysis process of calculating a first gamma ray spectrum based on a three-dimensional model of the measurement object stored in the container;
Before storing the measurement target in the container, a screening measurement step of acquiring radiation measurement data that is measurement data of radiation distribution in the measurement target,
Using a plurality of gamma ray detectors placed around the container after storing the measurement target in the container, a step of actually measuring the measured gamma ray spectrum,
A method for evaluating the concentration distribution of radioactivity in the container based on the measured gamma ray spectrum and the measured radiation data.

Images