Radioactive substance management system and radioactive substance management method

Abstract

To reduce excessive safety measures.SOLUTION: A radioactive substance management system 100 includes an acquisition device 10 for acquiring an internal image showing a state of a content 60 including a radioactive substance stored in a container 50, and a management device 20 for managing whether or not the content is a guarantee measure substance requiring a guarantee measure of safety measures based on the internal image. The management device includes a substance evaluation unit for warranty measure 21 that evaluates whether or not the content is the substance for warranty measure based on the internal image, a hydrogen generation rate evaluation unit 22 that evaluates a hydrogen generation rate generated from the content stored in the container based on the internal image, a hydrogen concentration evaluation unit 23 that evaluates a hydrogen concentration inside the container based on the internal image, and a recording unit 26 that records data of the substance for warranty measure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a radioactive material management system and a radioactive material management method. [Background technology]

[0002] Suppose an accident occurs at a nuclear power plant. In this case, materials such as nuclear fuel, structural materials, and concrete remain in their original form or in the form of molten debris inside the reactor pressure vessel (RPV) or primary containment vessel (PCV). The distribution of these materials inside the RPV or PCV has been estimated through accident progression analysis. However, due to uncertainties in the assumed accident progression scenario, the distribution of these materials differs from the actual state. Therefore, studies are being conducted to clarify the distribution of materials by removing radioactive materials, such as fuel debris, from the RPV or PCV and storing them in a container. Analyzing the contents (especially the composition and shape of the fuel debris) is being considered. Furthermore, for safeguards purposes such as confirming the safety of the materials and considering future methods for processing and disposing of them, safety measures such as drying and dehydration of the contents are being considered before transferring the containers to a storage facility. In addition, as a safety measure, measures such as criticality prevention and hydrogen removal are being considered for the contents. "Criticality prevention" could include the installation of neutron-absorbing materials. "Hydrogen removal" could include the installation of filters that allow hydrogen to escape, the installation of hydrogen removal equipment that removes hydrogen, and drying the contents. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-205883 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the nature of the contents is unclear. Therefore, conservative safety measures are required when transferring the container to a storage facility. "Conservative safety measures" refer to the uniform implementation of excessive safety measures formulated in accordance with pre-determined accident progression scenarios, regardless of whether the contents stored in the container are safeguarded materials that require safeguards, such as in criticality prevention processing or hydrogen removal processing. Therefore, there is a possibility that the time and cost required for safety measures will increase compared to the past.

[0005] A technology for analyzing the contents stored in a container is described, for example, in Patent Document 1. Patent Document 1 describes a "device for measuring the amount of nuclear material in damaged or melted fuel-containing material, comprising: an X-ray generator that irradiates X-rays onto a fuel debris storage container containing fuel debris; a radiation detector that detects the X-rays that have passed through the fuel debris storage container; a rotary drive mechanism that rotates and scans the X-ray generator and the radiation detector relative to the fuel debris storage container; and a signal processor that obtains a detection signal detected by the radiation detector, wherein the signal processor determines the amount of nuclear material in the fuel debris using the density at each point of the fuel debris determined from the detection signal and the known densities of the nuclear material and structural materials that make up the fuel debris." However, the prior art described in Patent Document 1 does not evaluate whether the contents stored in the container are safeguards material. Furthermore, the prior art described in Patent Document 1 does not evaluate the hydrogen generation rate or hydrogen concentration. Therefore, even if the amount of nuclear material in melted fuel-containing material is measured using the prior art described in Patent Document 1, conservative safety measures are still required. In other words, excessive safety measures formulated in accordance with pre-determined accident progression scenarios are required to be implemented uniformly.

[0006] The present invention has been made to solve the above-mentioned problems, and a main object of the present invention is to provide a radioactive material management system and a radioactive material management method that reduce excessive safety measures. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present invention is a radioactive material management system comprising an acquisition device that acquires an internal image showing the state of contents, including radioactive materials, stored in a container, and a management device that manages, based on the internal image, whether the contents are safeguard materials that require safety measures. Other means will be described later. [Effects of the Invention]

[0008] According to the present invention, excessive safety measures can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of a radioactive material management system according to an embodiment. [Figure 2A] 4 is a flowchart showing a first pattern of operation of the radioactive substance management system according to the embodiment. [Figure 2B] 10 is a flowchart showing a second pattern of operation of the radioactive substance management system according to the embodiment. [Figure 2C] 10 is a flowchart showing a third pattern of operation of the radioactive substance management system according to the embodiment. [Figure 2D] 10 is a flowchart showing a fourth pattern of operation of the radioactive substance management system according to the embodiment. [Figure 3] 4 is a flowchart showing a first pattern of operation of the radioactive substance management system according to the embodiment. [Figure 4A] 10 is a flowchart showing a second pattern of operation of the radioactive substance management system according to the embodiment. [Figure 4B] 10 is a flowchart showing the operation of a radioactive material management system of a comparative example. [Figure 5] FIG. 2 is an explanatory diagram of the hydrogen generation rate. [Figure 6A] FIG. 1 is an explanatory diagram of a first substance. [Figure 6B] FIG. 1 is an explanatory diagram of a second substance. [Figure 6C] FIG. 10 is an explanatory diagram of a third substance. [Figure 7] FIG. 10 is an explanatory diagram of internal image data. [Figure 8] FIG. 1 is an explanatory diagram of the diffusion coefficient of hydrogen used in calculating the hydrogen concentration. [Figure 9] FIG. 2 is a hardware configuration diagram illustrating an example of a computer that realizes the functions of a management device. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings. Note that each drawing is merely a schematic illustration to allow a sufficient understanding of the present invention. Therefore, the present invention is not limited to the illustrated examples. Furthermore, in each drawing, common or similar components are given the same reference numerals, and redundant explanations thereof will be omitted.

[0011] <Configuration of radioactive material management system> The configuration of a radioactive material management system 100 according to this embodiment will be described below with reference to Fig. 1. Fig. 1 is a schematic diagram of the configuration of a radioactive material management system 100 according to this embodiment.

[0012] As shown in FIG. 1, a radioactive material management system 100 according to this embodiment includes an acquisition device 10 and a management device 20. The acquisition device 10 is a device that acquires an internal image that represents the state of contents 60, including radioactive materials, stored in a container 50. The acquisition device 10 can be configured, for example, by a computed tomography device (CT device), an ultrasound imaging device, a gamma camera, an X-ray camera, or the like. Here, as an example, a description will be given assuming that the acquisition device 10 is configured by a computed tomography device (X-ray CT device) that uses X-rays. The management device 20 is a device that manages, based on the internal image, whether the contents 60 are safeguarded materials that require safeguards as safety measures.

[0013] Note that a gamma camera detects and images gamma rays emitted from radioactive materials inside the container 50, and its principle is different from that of an X-ray camera (radiography), which irradiates the container 50 with X-rays and uses the transmitted X-rays to capture an image of the inside of the container. Incidentally, a SPECT (Single Photon Emission Computed Tomography) can also be used as the acquisition device 10. SPECT is a type of gamma camera, and is a CT device that can perform tomography by rotating a detector around the container 50. Gamma cameras and SPECT differ from X-ray cameras and X-ray CT, which irradiate X-rays toward the container 50, in that they capture images of only materials that emit gamma rays.

[0014] The acquisition device 10 has an X-ray source 11 , an X-ray detection unit 12 , a rotation mechanism 13 , a vertical movement mechanism 14 , a body unit 15 , a mounting unit 16 , and an image creation unit 17 .

[0015] X-ray source 11 is a component that irradiates X-rays. X-ray source 11 is provided inside body 15. X-ray source 11 is arranged around opening 15a provided in body 15. X-ray source 11 radiates X-rays radially from an irradiation unit (not shown) provided near the center of a portion adjacent to opening 15a when viewed from above (for example, irradiates X-rays as a cone beam or a fan beam).

[0016] The X-ray detection unit 12 is a component that detects X-rays irradiated from the X-ray source 11. The X-ray detection unit 12 is provided inside the body 15. The X-ray detection unit 12 is arranged around an opening 15a provided in the body 15 so as to face the X-ray source 11 via the opening 15a. When viewed from above, the X-ray detection unit 12 has a shape that spreads out in a fan shape from a portion facing an irradiation unit (not shown) of the X-ray source 11 (a fan shape corresponding to the fan beam described above).

[0017] The rotation mechanism 13 is a mechanism that rotates the X-ray source 11 and the X-ray detection unit 12. The rotation mechanism 13 is provided inside the body unit 15. The rotation mechanism 13 rotates the X-ray source 11 and the X-ray detection unit 12 in the direction of arrow A11 while maintaining the relative positions of the X-ray source 11 and the X-ray detection unit 12. However, the rotation mechanism 13 may be configured to rotate in the opposite direction to the arrow A11.

[0018] The vertical movement mechanism 14 is a mechanism that moves the X-ray source 11 and the X-ray detection unit 12 up and down. The vertical movement mechanism 14 is provided outside the body unit 15 so as to support the body unit 15. The vertical movement mechanism 14 moves the X-ray source 11 and the X-ray detection unit 12 up and down together with the body unit 15 in the direction of arrow A12 while maintaining the relative positions of the X-ray source 11 and the X-ray detection unit 12.

[0019] The body 15 is a component that has the X-ray source 11 and the X-ray detection unit 12 inside. In the example shown in Fig. 1, the body 15 has a cylindrical shape. When viewed from above, an opening 15a that penetrates in the vertical direction is provided at approximately the center of the body 15. The opening 15a is a space formed to avoid the container 50 when the X-ray source 11 and the X-ray detection unit 12 are moved up and down.

[0020] The placement unit 16 is a component on which a container 50 containing contents 60 including radioactive materials is placed. In the example shown in FIG. 1 , the container 50 contains a first type material 61, a second type material 62, a third type material 63, and a fourth type material 64 as the contents 60. Here, the first type material 61 will be described as a radioactive material with a relatively large particle size (fuel debris or deposits). The second type material 62 will be described as a radioactive material with a medium particle size (fuel debris or deposits). The third type material 63 will be described as a radioactive material with a relatively small particle size (fuel debris or deposits). The fourth type material 64 will be described as a non-radioactive material (for example, fallen objects such as grating).

[0021] The image creating unit 17 is a component that creates an internal image that shows the state of the contents 60 that contain radioactive materials stored in the container 50.

[0022] The acquisition device 10 rotates the X-ray source 11 and the X-ray detection unit 12 using the rotation mechanism 13, while vertically moving the X-ray source 11 and the X-ray detection unit 12 together with the body unit 15 using the vertical movement mechanism 14. At this time, the X-rays irradiated from the X-ray source 11 are detected by the X-ray detection unit 12, and the detection data detected by the X-ray detection unit 12 is output to the image creation unit 17. The detection data is a plurality of X-ray images corresponding to any height position of the container 50. Each X-ray image has pixel-like content that two-dimensionally represents the cross-sectional structure of the content 60. Each X-ray image represents the content moved in the height direction of the container 50. The image creation unit 17 synthesizes each X-ray image to create a voxel-like structural image that stereoscopically (three-dimensionally) represents the structure of the content 60. As a result, the acquisition device 10 acquires an internal image that represents the state of the content 60, including the radioactive material contained in the container 50, using the image creation unit 17. The acquisition device 10 transmits the voxel-shaped constituent image created by the image creation unit 17 to the management device 20 as internal image data 30a.

[0023] However, the acquisition device 10 may be configured to rotate the container 50 without rotating the X-ray source 11 and the X-ray detection unit 12. The acquisition device 10 may also be configured to move the container 50 up and down without moving the X-ray source 11 and the X-ray detection unit 12 up and down. The acquisition device 10 may also be configured to rotate and move the container 50 up and down without rotating or moving the X-ray source 11 and the X-ray detection unit 12 up and down.

[0024] Furthermore, the acquisition device 10 can be configured with a device other than an X-ray CT device, such as an ultrasound imaging device, a gamma camera, or an X-ray camera. When the acquisition device 10 is configured with an ultrasound imaging device, the acquisition device 10 is configured to have an ultrasound transmitter (not shown) and an ultrasound detector (not shown) instead of the X-ray source 11 and the X-ray detector 12 (the ultrasound transmitter can also serve as the ultrasound detector). When the acquisition device 10 is configured with a gamma camera, the X-ray source 11 is unnecessary. In the case of an X-ray camera, the acquisition device 10 is configured to have both the X-ray source 11 and the X-ray detector 12. Note that the reason why the X-ray source 11 is unnecessary in the case of a gamma camera is that gamma rays and the like are radiated (emitted) from the contents 60 containing a radioactive material stored in the container 50, and the X-ray detector 12 only needs to detect the gamma rays and the like.

[0025] The management device 20 has a safeguards material evaluation unit 21, a hydrogen generation rate evaluation unit 22, a hydrogen concentration evaluation unit 23, a main calculation unit 24, and a recording unit 26.

[0026] The safeguard material evaluation unit 21 is a component that evaluates, based on the internal image, whether or not the contents 60 are safeguard materials that require safeguards as safety measures.

[0027] The hydrogen generation rate evaluation unit 22 is a component that evaluates the rate at which hydrogen is generated from the contents 60 stored in the container 50 based on the internal image. As will be described later, the hydrogen generation rate varies depending on the type of contents 60, particle size, etc. Incidentally, the greater the amount of radioactive material (fuel debris), the greater the hydrogen generation rate. Furthermore, even if the amount of radioactive material is the same, the hydrogen generation rate is greater when the particle size (particle size) of the radioactive material is small than when the particle size is large.

[0028] The hydrogen concentration evaluation unit 23 is a component that evaluates the hydrogen concentration inside the container 50 based on an internal image. As will be described later, when the porosity inside the container 50 is small, the hydrogen concentration is more likely to be high than when the porosity is large.

[0029] The main calculation unit 24 is a component that executes various calculations. The recording unit 26 is a component that records data on safeguard materials. In this embodiment, the recording unit 26 will be described as recording data 30 including internal image data 30a, content evaluation data 31, hydrogen generation rate data 32, hydrogen concentration data 33, and a control program 99.

[0030] The internal image data 30a is data representing the state of the contents 60 of the container 50, created by the image creation unit 17 of the acquisition device 10. Here, the internal image data 30a will be described as voxel-like constituent image data of the contents 60, created by the image creation unit 17 of the acquisition device 10.

[0031] The content evaluation data 31 is data that indicates the evaluation result of the content 60. Here, the description will be given assuming that safeguard material data indicating whether the content 60 is a safeguard material is used as the content evaluation data 31. The hydrogen generation rate data 32 is data that represents the rate at which hydrogen is generated from the contents 60 contained in the container 50 . The hydrogen concentration data 33 is data that represents the hydrogen concentration inside the container 50.

[0032] The management device 20 is configured with a personal computer, a server, or the like, and by installing a control program 99 from a storage medium 90, the calculation unit functions as a safeguards material evaluation unit 21, a hydrogen generation rate evaluation unit 22, and a hydrogen concentration evaluation unit 23. The storage medium 90 may be in the form of, for example, a memory member such as a USB memory, an HDD device, an optical medium such as a CD-ROM or DVD, a magnetic medium such as a flexible disk, or other forms.

[0033] <Operation of the radioactive material management system> The operation of the radioactive material management system 100 will be described below with reference to Figures 2A to 4B. Figures 2A to 2D are flowcharts showing first to fourth patterns of operation of the radioactive material management system 100. Note that the example of operation shown in Figures 2A to 4B is merely an example, and the operation of the radioactive material management system 100 can be changed depending on the operation.

[0034] Assume that an accident occurs at a nuclear power plant. In this case, as shown in Figures 2A to 2D, materials containing radioactive materials, such as fuel debris, are removed from the inside of a reactor pressure vessel (RPV) or a primary containment vessel (PCV) (step S105). The removed materials are stored in a container 50 (step S110).

[0035] The container 50 is placed on the placement unit 16 at any timing. Then, the acquisition device 10 of the radioactive material management system 100 moves the X-ray source 11 and the X-ray detection unit 12 up and down while rotating them around the container 50 to acquire an internal image representing the state of the contents 60 of the container 50 (step S115). The acquired internal image (internal image data 30a) is transmitted from the acquisition device 10 to the management device 20. Then, the management device 20 manages the contents 60 of the container 50 (step S116).

[0036] In step S116, the radioactive material management system 100 can execute the first to fourth patterns of operation shown in FIGS. 2A to 2D. The first pattern of operation shown in FIG. 2A involves performing the processes of steps S120 to S125 in step S116. The second pattern of operation shown in FIG. 2B involves performing the processes of steps S130 to S140 in step S116. The third pattern of operation shown in FIG. 2C involves performing the processes of steps S120 to S125 in step S116, followed by the processes of steps S130 to S140. The fourth pattern of operation shown in FIG. 2D involves performing the processes of steps S130 to S140 in step S116, followed by the processes of steps S120 to S125. The processes of steps S120 to S140 will be described below.

[0037] In step S120, the management device 20 uses the safeguard material evaluation unit 21 to evaluate, based on the internal image, whether or not the contents 60 are safeguard materials that require safeguards as safety measures.

[0038] In step S125, the management device 20 records in the recording unit 26 the data of the contents 60 that have been evaluated as safeguards materials.

[0039] In step S130, the management device 20 causes the hydrogen generation rate evaluation unit 22 to evaluate the rate of hydrogen generation from the contents 60 contained in the container 50 based on the internal image.

[0040] In step S135, the management device 20 causes the hydrogen concentration evaluation unit 23 to evaluate the hydrogen concentration inside the container 50 based on the internal image.

[0041] In step S140, the management device 20, through the main control unit 24, shortens or reduces excessive safety measures that have been formulated in accordance with a pre-determined accident progression scenario based on the evaluation results of the hydrogen generation rate and the hydrogen concentration.

[0042] The processing of steps S120 to S125 shown in Figures 2A to 4B is intended to non-destructively acquire and record property data such as the shape and composition of the contents 60 of the container 50 using an X-ray CT device (acquisition device 10).

[0043] Details of the processing from step S120 to step S125 will be described below with reference to Fig. 3. Fig. 3 is a flowchart showing the operation of the first pattern of the radioactive material management system 100. Fig. 3 shows details of the processing from step S120 to step S125 shown in Fig. 2A.

[0044] 3, the radioactive material management system 100 performs the process of step S120 after step S115. In step S120, first, the safeguards material evaluation unit 21 of the management device 20 determines whether the shape of the content 60 in the container 50 is a molten material or not, based on the internal image data 30a recorded in the recording unit 26 (step S120a).

[0045] In step S115, internal image data 30a is acquired. From the internal image data 30a, it is possible to acquire data such as the state of the contents 60 (e.g., lumps or particles), the shape of the contents 60, the size (particle size, etc.) of the contents 60, the density distribution of the contents 60, the moisture content of the contents 60, the porosity of the contents 60, and other data. In step S120a, the management device 20 can determine whether the contents 60 are molten material based on the shape of the contents 60, the radiation dose of the contents 60, and the location where the contents 60 were removed.

[0046] If the judgment in step S120a determines that the shape of the contents 60 is not molten (if "No"), the safeguard material evaluation unit 21 determines whether the contents 60 are equivalent to iron based on the internal image data 30a (step S120b).

[0047] If it is determined in step S120b that the contents 60 are equivalent to iron (if "Yes"), the safeguards material evaluation unit 21 evaluates the contents 60 as a structural material (radioactive waste) (step S120c). Then, the safeguards material evaluation unit 21 records the contents evaluation data 31 of the contents 60 evaluated as a structural material (radioactive waste) in the recording unit 26 (step S125). The contents evaluation data 31 preferably represents the properties of the contents 60, such as the shape and composition of the contents 60. Furthermore, the contents evaluation data 31 preferably includes a classification of whether the contents 60 are safeguards material (fuel debris, deposits, structural materials such as grating, etc.).

[0048] If the determination in step S120a determines that the shape of the contents 60 is molten (if "Yes"), the safeguards material evaluation unit 21 determines that the contents 60 are fuel debris or deposits (step S120d). In this case, the safeguards material evaluation unit 21 determines whether the contents 60 are equivalent to concrete (step S120e). Also, if the determination in step S120b determines that the contents 60 are not equivalent to iron (if "No"), the safeguards material evaluation unit 21 determines that the contents 60 are fuel debris or deposits (step S120d). In this case as well, the safeguards material evaluation unit 21 determines whether the contents 60 are equivalent to concrete (step S120e).

[0049] Here, "fuel debris" refers to the material formed by melting nuclear fuel. Also, "deposits" refers to the material formed by melting and mixing concrete and other materials deposited on the pedestal. Since "deposits" are primarily materials formed by melting concrete that constitutes the building, if it is determined that the contents 60 are equivalent to concrete based on density, etc., then in step S120f, the contents 60 are evaluated as deposits.

[0050] In step S120b, even if it is determined that the contents 60 are not molten material based on the shape of the contents 60, if the density of the contents 60, etc. indicates that the contents 60 are not equivalent to iron, the management device 20 can determine that the contents 60 are fuel debris or deposits.

[0051] If the determination in step S120e determines that the contents 60 are equivalent to concrete (if "Yes"), the safeguards material evaluation unit 21 evaluates the contents 60 as deposits (step S120f). Then, the safeguards material evaluation unit 21 records the contents evaluation data 31 of the contents 60 evaluated as deposits in the recording unit 26 (step S125). The contents evaluation data 31 preferably represents the properties of the contents 60, such as the shape and composition of the contents 60. Furthermore, the contents evaluation data 31 preferably includes a classification of whether the contents 60 are safeguards materials (fuel debris, deposits, structural materials such as grating, etc.).

[0052] If the determination in step S120e determines that the contents 60 are not equivalent to concrete (in the case of "No"), the safeguards material evaluation unit 21 evaluates the contents 60 as fuel debris (step S120g). Then, the safeguards material evaluation unit 21 records content evaluation data 31 of the contents 60 evaluated as fuel debris in the recording unit 26 (step S125). The content evaluation data 31 preferably represents properties such as the shape and composition of the contents 60. Furthermore, the content evaluation data 31 preferably includes data that classifies the contents 60 as safeguards material (fuel debris, deposits, structural materials such as grating, etc.).

[0053] After step S125, the radioactive material control system 100 ends the series of routine processes shown in Fig. 3. The contents 60 evaluated as deposits in step S120f and the contents 60 evaluated as fuel debris in step S120g are transported to a storage facility (not shown) while still contained in the container 50, and are managed as safeguards materials in the storage facility (not shown).

[0054] Furthermore, the processing of steps S130 to S140 shown in Figures 2A to 4B is intended to evaluate the hydrogen generation rate and hydrogen concentration inside the container 50 based on data acquired by the X-ray CT device (acquisition device 10), thereby reducing excessive safety measures.

[0055] In this regard, when the properties of the contents 60 in the container 50 are unclear, safety measures are formulated based on the results of evaluations made under conservative assumptions. As a result, conservative safety measures, including excessive safety measures, are formulated. The radioactive material management system 100 evaluates the hydrogen generation rate and hydrogen concentration using optimized assumptions from data acquired by the X-ray CT device (acquisition device 10), and reduces excessive safety measures (for example, drying treatment of the contents 60).

[0056] Details of the processing of steps S130 to S140 will be explained below with reference to Fig. 4A. Fig. 4A is a flowchart showing the operation of a second pattern of the radioactive material control system 100. Fig. 4A shows details of the processing of steps S130 to S140 shown in Fig. 2B. In the example shown in Fig. 4A, the radioactive material control system 100 is configured not to perform drying processing on contents 60 that do not require drying processing, as this is an excessive safety measure among the safety measures formulated in accordance with a previously assumed accident progression scenario.

[0057] In the example shown in FIG. 4A, the radioactive material management system 100 performs the processes of steps S130 and S135 after step S115. In step S115, internal image data 30a measured for approximately one hour per container 50 is acquired. In steps S130 and S135, first, the hydrogen generation rate evaluation unit 22 of the management device 20 calculates the rate of hydrogen generation from the contents 60 of the container 50 based on the internal image data 30a recorded in the recording unit 26 (step S130a). Next, the hydrogen concentration evaluation unit 23 of the management device 20 calculates the hydrogen concentration inside the container 50 based on the internal image data 30a recorded in the recording unit 26 (step S135a). Next, the main calculation unit 24 of the management device 20 determines whether or not a drying process is required for the contents 60 (step S135b).

[0058] If it is determined in step S135b that drying processing of the contents 60 is necessary, in step S140, the management device 20 performs drying processing of the contents 60 (step S140a). Once the contents 60 have been sufficiently dried, the management device 20 transfers the container 50 to a storage facility (not shown) using a transfer means (not shown) (step S140b). Then, the management device 20 stores the container 50 in the storage facility (not shown) (step S140c).

[0059] On the other hand, if it is determined in step S135b that drying treatment of the contents 60 is not necessary, the container 50 is transported to a storage facility (not shown) by a transport means (not shown) (step S140d) without performing the drying treatment (step S140a) of the contents 60. Then, the management device 20 stores the container 50 in the storage facility (not shown) (step S140e).

[0060] Here, to clearly explain the operation of the radioactive material control system 100, the operation of a radioactive material control system (not shown) of a comparative example will be described with reference to FIG. 4B. FIG. 4B is a flowchart showing the operation of the radioactive material control system (not shown) of the comparative example. In the example shown in FIG. 4B, the radioactive material control system (not shown) of the comparative example uniformly performs the processing of step S140a after step S110. That is, the radioactive material control system (not shown) of the comparative example uniformly performs the drying process of the contents 60 in step S140a as a safety measure for the contents 60, regardless of whether the drying process of the contents 60 is necessary. Such a radioactive material control system (not shown) of the comparative example uniformly performs excessive safety measures formulated in accordance with a pre-determined accident progression scenario. As a result, the radioactive material control system (not shown) of the comparative example increases the time and cost required for safety measures.

[0061] In contrast, as shown in FIG. 4A, the radioactive material control system 100 according to this embodiment does not perform the drying process (step S140a) on the contents 60 that do not require drying. Such a radioactive material control system 100 according to this embodiment can shorten the time and reduce costs required for safety measures. Note that the drying process (step S140a) of the contents 60 takes approximately 10 hours to dry the contents 60 of one container 50 until the moisture content reaches a few percent. When it is determined in step S135b that the drying process of the contents 60 is not required, the radioactive material control system 100 can reduce the time required by approximately 10 hours per container 50.

[0062] <Hydrogen generation rate> Here, the hydrogen generation rate will be explained. The rate at which hydrogen is generated from the contents 60 stored in the container 50 varies depending on the type of contents 60, particle size, etc. Figure 5 is an explanatory diagram of the hydrogen generation rate. Figure 5 shows the hydrogen generation rate according to the particle size of the substance contained in the contents 60. Figure 5 shows the amount of hydrogen generated (R H2 power ) hydrogen generation rate and the amount of hydrogen generated when particle size dependence is taken into account (R H2 d 5, the horizontal axis represents the particle size, and the vertical axis represents the hydrogen generation rate.

[0063] Here, the self-shielding effect of fuel debris limits the energy that contributes to radiolysis. Therefore, in order to evaluate the self-shielding effect, the amount of hydrogen generated when fuel debris particles are fine particles (R H2 power ) hydrogen generation rate and the amount of hydrogen generated when particle size dependence is taken into account (R H2 d) can be evaluated. In FIG. 5, it is assumed that most of the materials stored in the container 50 have particle sizes equal to or larger than the threshold value α1 [mm]. The threshold value α1 depends on the specifications of the handling device (not shown) that removes the materials from the inside of the reactor pressure vessel (RPV) or the containment vessel (PCV). In the example shown in FIG. 5, the hydrogen generation rate of materials with particle sizes equal to or larger than the threshold value α1 (i.e., most of the materials stored in the container 50) is several times lower than the hydrogen generation rate when the materials are fine particles.

[0064] Here, we will explain the evaluation formula for the hydrogen generation rate when the particle size characteristics are clear. The hydrogen generation rate R when the fuel debris particles are fine particles is H2 power The evaluation formula for this is as follows: (1) The hydrogen generation rate R when particle size dependency is also taken into consideration is H2 d The evaluation formula is as follows:

number

number

[0065] The radioactive material management system 100 can measure the shape and particle size of the contents 60 based on internal images acquired by the X-ray CT device (acquisition device 10). FIGS. 6A to 6C are explanatory diagrams of a first type material 61, a second type material 62, and a third type material 63, respectively, as examples of the contents 60. The first type material 61 shown in FIG. 6A is a radioactive material (fuel debris or deposits) with a relatively large particle size. The second type material 62 shown in FIG. 6B is a radioactive material (fuel debris or deposits) with a medium particle size. The third type material 63 shown in FIG. 6C is a radioactive material (fuel debris or deposits) with a relatively small particle size. When the spatial resolution of the X-ray CT device (acquisition device 10) is X1 [mm], the radioactive material management system 100 can measure the shape and particle size of the contents 60 for materials up to a particle size of diameter X1 [mm].

[0066] The radioactive material management system 100 can also estimate the weight of fuel debris and the fuel content ratio contained in the contents 60 based on internal images acquired by the X-ray CT scanner (acquisition device 10). FIG. 7 is an explanatory diagram of internal image data 30a. Here, as an example, the internal image data 30a shown in FIG. 7 is described as X-ray image data (X-ray cross-sectional image = slice image of a certain cross section). The slice image of the container 50 in FIG. 7 shows the state in which the container 50 contains molten material 111 containing radioactive material, molten material 112 attached to structural materials, and structural materials 113 such as grating. The radioactive material management system 100 identifies materials (mainly nuclear fuel materials) contained in the contents 60 based on the density distribution obtained from the internal image data 30a shown in FIG. 7 and calculates the volume of the materials. The radioactive material management system 100 can estimate the weight of fuel debris and the fuel content ratio based on the density and volume of the materials. 7 shows a slice image of a cross section at an arbitrary location of the container 50, but it is also possible to obtain a slice image of a vertical section at an arbitrary location of the container 50. Also, a three-dimensional image can be obtained.

[0067] Furthermore, the radioactive material management system 100 can estimate the amount of water used in evaluating the energy absorption rate based on internal images acquired by the X-ray CT device (acquisition device 10). The energy absorption rate when all energy contributes to the radiolysis of water will be an overly conservative value. The radioactive material management system 100 can identify the water inside the container 50 based on internal images acquired by the X-ray CT device (acquisition device 10) and estimate the amount of water inside the container 50 from the volume of the water. The radioactive material management system 100 can improve the estimation accuracy of the energy absorption rate by evaluating the energy absorption rate through particle transport calculations using the estimated amount of water.

[0068] <Hydrogen concentration> Here, the hydrogen concentration inside the container 50 will be described. The hydrogen concentration inside the container 50 varies depending on the type of content 60, particle size, etc. Furthermore, hydrogen moves within the particles, and the movement of hydrogen within the particles occurs due to diffusion caused by differences in hydrogen concentration and advection caused by pressure differences. Diffusion can be expressed by Fick's law, and advection can be expressed by Darcy's law. The evaluation formula for hydrogen concentration can be expressed by an advection-diffusion equation using a diffusion coefficient and porosity that vary depending on factors such as particle size (particle diameter). For example, the evaluation formula for hydrogen concentration is as shown in Equation (3) below. The hydrogen concentration is evaluated using Equation (3) below, the law of conservation of mass, and the law of conservation of momentum.

number

[0069] The hydrogen diffusion coefficient varies depending on the diameter of surrounding particles, for example, as shown in FIG. 8. FIG. 8 is an explanatory diagram of the hydrogen diffusion coefficient used to calculate the hydrogen concentration. The horizontal axis of FIG. 8 represents the void fraction (porosity), and the vertical axis represents the hydrogen diffusion coefficient in the packed bed. The radioactive material management system 100 can improve the accuracy of the evaluation of the hydrogen concentration by measuring the void fraction (porosity) based on internal images acquired by the X-ray CT device (acquisition device 10).

[0070] <Major features of the radioactive material management system> The radioactive material management system 100 according to this embodiment can be configured to have the following features. (1) As shown in Fig. 1, a radioactive material management system 100 according to this embodiment includes an acquisition device 10 and a management device 20. The acquisition device 10 is a device that acquires an internal image that represents the state of contents 60, including radioactive materials, stored in a container 50. The management device 20 is a device that manages, based on the internal image, whether or not the contents 60 are safeguarded materials that require safeguards as safety measures.

[0071] The radioactive material control system 100 according to this embodiment manages whether the contents 60 are safeguarded material or not based on internal images using the management device 20. Such a radioactive material control system 100 only needs to increase the level of safety measures when the contents 60 are safeguarded material. Therefore, the radioactive material control system 100 can reduce excessive safety measures in accordance with the evaluation of the contents 60, rather than uniformly implementing excessive safety measures formulated in accordance with a pre-determined accident progression scenario.

[0072] (2) As shown in Fig. 1, in the radioactive material management system 100 according to this embodiment, the management device 20 has a safeguards material evaluation unit 21 and a recording unit 26. The safeguards material evaluation unit 21 is a component that evaluates whether or not the contents 60 are safeguards material based on an internal image. The recording unit 26 is a component that records data on the safeguards material.

[0073] The radioactive material management system 100 according to this embodiment records data on the contents 60 that have been evaluated as safeguards material in the recording unit 26. Such a radioactive material management system 100 can later take safeguards measures such as confirming the safety of the material and considering future methods of processing and disposing of the material.

[0074] (3) As shown in FIG. 1 , in the radioactive material management system 100 according to this embodiment, the management device 20 has a hydrogen generation rate evaluation unit 22 and a hydrogen concentration evaluation unit 23. The hydrogen generation rate evaluation unit 22 is a component that evaluates the rate at which hydrogen is generated from the contents 60 stored in the container 50 based on an internal image. The hydrogen concentration evaluation unit 23 is a component that evaluates the hydrogen concentration inside the container 50 based on an internal image.

[0075] In the radioactive material management system 100 according to this embodiment, the hydrogen generation rate evaluation unit 22 evaluates the rate at which hydrogen is generated from the contents 60 stored in the container 50, and the hydrogen concentration evaluation unit 23 evaluates the hydrogen concentration inside the container 50. Such a radioactive material management system 100 can reduce excessive safety measures, thereby saving time and reducing costs.

[0076] (4) As shown in Figures 2A to 2D, the radioactive material management method according to this embodiment includes an acquisition step (step S115) and a management step (step S116). The acquisition step (step S115) is a step of acquiring an internal image that represents the state of contents 60, including radioactive materials, stored in container 50. The management step (step S116) is a step of managing, based on the internal image, whether contents 60 are safeguarded materials that require safeguards as safety measures.

[0077] The radioactive material management method according to this embodiment manages whether or not the contents 60 are safeguards material based on internal images in the management step (step S116). Such a radioactive material management method only requires increasing the level of safety measures if the contents 60 are safeguards material. Therefore, the radioactive material management method can reduce excessive safety measures in accordance with the evaluation of the contents 60, rather than uniformly implementing excessive safety measures formulated in accordance with a previously assumed accident progression scenario.

[0078] (5) As shown in Figures 2A, 2C, and 2D, in the radioactive material management method according to this embodiment, the management process (step S116) includes a contents determination process (step S120) and a recording process (step S125). The contents determination process (step S120) is a process of evaluating whether or not the contents 60 are safeguards materials based on an internal image. The recording process (step S125) is a process of recording data on the safeguards materials.

[0079] In the radioactive material management method according to this embodiment, data on the contents 60 that have been evaluated as safeguards material is recorded in the recording unit 26. Such a radioactive material management method allows safeguards measures, such as confirmation of the safety of the material and consideration of future methods of processing and disposing of the material, to be taken later.

[0080] (6) As shown in Figures 2B, 2C, and 2D, in the radioactive material management method according to this embodiment, the management step (step S116) includes a hydrogen generation rate evaluation step (step S130) and a hydrogen concentration evaluation step (step S135). The hydrogen generation rate evaluation step (step S130) is a step of evaluating the rate at which hydrogen is generated from the contents 60 contained in the container 50 based on an internal image. The hydrogen concentration evaluation step (step S135) is a step of evaluating the hydrogen concentration inside the container 50 based on an internal image.

[0081] In the radioactive material management method according to this embodiment, a hydrogen generation rate evaluation step (step S130) evaluates the rate at which hydrogen is generated from contents 60 stored in container 50, and a hydrogen concentration evaluation step (step S135) evaluates the hydrogen concentration inside container 50. Such a radioactive material management method can reduce excessive safety measures, save time, and reduce costs.

[0082] As described above, the radioactive material management system 100 according to this embodiment can reduce excessive safety measures (for example, can lead to reductions in various costs involved in storage, transportation, and various processes).

[0083] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of the embodiments with other configurations, and it is also possible to add other configurations to the configuration of the embodiments. Furthermore, it is possible to add, delete, or replace part of each configuration with other configurations.

[0084] In the above-described embodiment, the drying process of the contents 60 is presented as an example of shortening or reducing the excessive safety measures shown in Figures 2A to 2D. However, excessive safety measures that can be shortened or reduced are not limited to the drying process of the contents 60. For example, the following can be presented as excessive safety measures that can be shortened or reduced. (Filling process) Calculate the volume of an object from its shape to evaluate the filling rate of a container and use it in operational methods to manage the filling amount. - Utilize it as a processing method to increase the filling rate (for example, if there are cavities, it is better to crush them). -Use it to determine the processing area. (Dehydration treatment) · Use the internal moisture content as a method to determine whether processing is necessary. -Used as a method to control whether or not there is corrosion in the container. (Property evaluation process) -Used as a method to evaluate porosity rather than shape. -Used as a method for setting the effective hydrogen diffusion coefficient and effective thermal diffusion coefficient from the porosity. -Used to reflect in various evaluations. - Utilize it as a method to determine the composition distribution inside the furnace to improve the efficiency of removal work. -Used to determine when removal is complete. -Used to review accident progression scenarios. -Used to reconfirm the properties during storage. -Use it to change storage methods. -Used to determine sampling locations and processing methods for detailed property analysis. -Use in sampling analysis methods. -Used to improve imaging plates. - Utilize it to improve field emission scanning electron microscopes (FE-SEM). Here, an FE-SEM is a microscope with the following configuration: An FE-SEM uses an electron lens to focus an electron beam to a very small diameter, similar to how a magnifying glass (convex lens) focuses sunlight onto a single point, and then irradiates the sample. The FE-SEM scans this incident electron beam over the sample (i.e., traces the electron beam to obtain information about the sample's lines and surfaces). In this way, an FE-SEM obtains images by detecting secondary electron images (mainly images of the minute topography of the sample surface) and backscattered electron images (compositional images: dependent on the average atomic number and crystal orientation) emitted from the sample. ·αUsed for various analyses. -Used for gamma nuclide analysis. -Used in inductively coupled plasma mass spectrometry (ICP-MS). Here, ICP-MS is a technique for elemental analysis as follows. Specifically, ICP-MS uses an inductively coupled plasma (ICP) generated by applying high-frequency power to argon (Ar) gas as an ion source. In ICP-MS, a liquid sample is introduced into the ICP in a mist form, and the elements in the sample ionized by the plasma are separated and detected by a mass spectrometer (MS). Used for Transmission Electron Microscopy-Energy Dispersive X-ray Spectroscopy (TEM-EDX). Here, EDX is a technique for performing elemental analysis and qualitative analysis by measuring the energy and number of occurrences of characteristic X-rays generated when an area to be analyzed is irradiated with an electron beam.

[0085] In the above-described embodiment, the acquisition device is an X-ray CT device. However, the acquisition device can be configured with devices other than an X-ray CT device, such as an ultrasound imaging device, a gamma camera, an X-ray camera, or other devices. When using a gamma camera or an X-ray camera, the acquisition device can be configured to use an optical camera in combination, and a gamma-ray image acquired by the gamma camera or an X-ray image acquired by the X-ray camera can be superimposed on an image captured by the optical camera.

[0086] Furthermore, the X-ray CT device and the above-mentioned SPECT have different functions (principles), and they may be combined. That is, the X-ray CT device as an acquisition device irradiates the container 50 with X-rays to obtain the internal morphology of the container 50 (such as the shape of the objects inside) (a morphological image of the contents is obtained). The SPECT and gamma camera as acquisition devices detect gamma rays from inside the container 50 to obtain the presence (amount) of radioactive material inside the container 50 (a functional image is obtained). By combining the X-ray CT device and the SPCT (by superimposing the morphological image and the functional image), the shape, position, and amount of radioactive material inside the container 50 can be more accurately determined. The SPCT may be a gamma camera.

[0087] The management device 20 according to the embodiment is realized by a computer 900 having a configuration as shown in FIG. 9, for example. FIG. 9 is a hardware configuration diagram showing an example of a computer 900 that realizes the functions of the management device 20 according to the embodiment described above. The computer 900 includes a CPU 901, a ROM 902, a RAM 903, an SSD 904, an input / output interface 905 (referred to as an input / output I / F (Interface) in FIG. 9), a communication interface 906 (referred to as a communication I / F in FIG. 9), and a media interface 907 (referred to as a media I / F in FIG. 9). The computer 900 may include an HDD (Hard Disc Drive) instead of the SSD 904, or may include an HDD in addition to the SSD 904.

[0088] CPU 901 operates based on a program stored in ROM 902 or SSD 904 (stored in recording unit 26), and performs control by safeguard material evaluation unit 21 in Fig. 1 and the like. ROM 902 stores a boot program executed by CPU 901 when computer 900 is started up, programs related to the hardware of computer 900, and the like. Recording medium 912 corresponds to storage medium 90 in Fig. 1. [Explanation of symbols]

[0089] 10 Acquisition device (computed tomography device) 11 X-ray source 12 X-ray detection unit 13 Rotation mechanism 14 Up and down movement mechanism 15 Torso 15a opening 16 Placement section 17 Image Creation Department 20 Management device 21 Safeguards Materials Evaluation Division 22 Hydrogen generation rate evaluation section 23 Hydrogen concentration evaluation section 24 Main calculation section 26 Recording Section 30 Recorded Data (Safeguards Material Data) 30a Internal image data 31 Contents evaluation data (safeguard material data) 32 Hydrogen generation rate data 33 Hydrogen concentration data 50 containers 60 Contents (specimen) 61 Class 1 substances (radioactive substances) 62 Class 2 substances (radioactive substances) 63 Type 3 substances (radioactive substances) 64 Type 4 substances (non-radioactive substances) 90 Storage medium 99 Control Program 100 Radioactive Material Management System 111 Melt 112 Melt 113 Structural materials

Claims

1. an acquisition device for acquiring an internal image representing the state of the contents, including the radioactive material, stored in the container; and a management device that manages whether the contents are safeguard substances that require safety measures based on the internal image. A radioactive material management system characterized by the above.

2. 2. The radioactive material management system according to claim 1, The management device a safeguard material evaluation unit that evaluates whether the contents are the safeguard material based on the internal image; and a recording unit for recording data on the safeguard material; A radioactive material management system characterized by the above.

3. 3. The radioactive material management system according to claim 2, The management device further a hydrogen generation rate evaluation unit that evaluates a rate at which hydrogen is generated from the content stored in the container based on the internal image; a hydrogen concentration evaluation unit that evaluates the hydrogen concentration inside the container based on the internal image. A radioactive material management system characterized by the above.

4. 2. The radioactive material management system according to claim 1, The management device a hydrogen generation rate evaluation unit that evaluates a rate at which hydrogen is generated from the content stored in the container based on the internal image; a hydrogen concentration evaluation unit that evaluates the hydrogen concentration inside the container based on the internal image. A radioactive material management system characterized by the above.

5. 5. The radioactive material management system according to claim 3, the hydrogen generation rate evaluation unit classifies the contents based on an arbitrarily determined threshold value, and evaluates the hydrogen generation rate in accordance with the proportion of the classified contents; The hydrogen concentration evaluation unit calculates the porosity inside the container to evaluate the hydrogen concentration. A radioactive material management system characterized by the above.

6. an acquisition step of acquiring an internal image representing the state of the contents, including the radioactive material, contained in the container; and a management step of managing whether the contents are safeguard materials that require safeguards based on the internal image. A radioactive material management method.

7. 7. The radioactive material management method according to claim 6, The management step includes: a contents determination step of evaluating whether the contents are the safeguard material based on the internal image; a recording step of recording data on the safeguard material. A radioactive material management method.

8. The radioactive material management method according to claim 7, The management step further comprises: a hydrogen generation rate evaluation step of evaluating a rate at which hydrogen is generated from the content housed in the container based on the internal image; and a hydrogen concentration evaluation step of evaluating the hydrogen concentration inside the container based on the internal image. A radioactive material management method.

9. 7. The radioactive material management method according to claim 6, The management step includes: a hydrogen generation rate evaluation step of evaluating a rate at which hydrogen is generated from the content housed in the container based on the internal image; and a hydrogen concentration evaluation step of evaluating the hydrogen concentration inside the container based on the internal image. A radioactive material management method.

10. The radioactive material management method according to claim 8 or 9, In the hydrogen generation rate evaluation step, the contents are classified based on an arbitrarily determined threshold value, and the hydrogen generation rate is evaluated according to the proportion of the classified contents; In the hydrogen concentration evaluation step, the porosity inside the container is calculated to evaluate the hydrogen concentration. A radioactive material management method.

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