Radiation measurement plan support system and measurement plan support method

Abstract

To support a preparation of a plan of a detector arrangement that can highly accurately measure radiation of waste, and enables a series of work of installation, measurement and removal in a short time.SOLUTION: A measurement plan support system comprises: a shape mesh generation unit that generates a three-dimensional shape mesh model of waste; a mesh development unit that develops a shape mesh model to a two-dimensional plane mesh development diagram; a local contamination mode database that has a plurality of local contamination modes two-dimensionally expressing an aspect of local contamination recorded; a local contamination mode assignment unit that assigns the local contamination mode acquired from the local contamination mode database to an arbitrary mesh of the plane mesh development diagram; a three-dimensional dose rate calculation unit that restores the plane mesh development diagram having the local contamination mode assigned to the three-dimensional shape mesh model, and calculates a three-dimensional dose rate of radiation from the local contamination on the shape mesh model; and a detector arrangement calculation unit that calculates an arrangement of a radiation detector detecting the radiation from the local contamination.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a radiation measurement planning support system and a measurement planning support method that support the creation of a radiation detector placement plan prior to the measurement of the radioactivity concentration of waste contaminated with radiation. [Background technology]

[0002] Among the radioactive waste discharged from environments where strong radiation is present (such as nuclear power plants, hospital X-ray and CT examination rooms), there is a large amount of waste with low radioactivity that does not affect the human body. It is not realistic to strictly manage all of the large amounts of waste discharged from these types of environments in the same way as highly radioactive waste that can affect the human body, due to reasons such as cost. Therefore, while highly radioactive waste is strictly managed, it is common practice to reuse or ultimately dispose of low-radioactivity waste in the same way as regular waste.

[0003] Therefore, there has been a demand for a technology that can measure radioactivity concentration with high accuracy in order to identify waste with high radioactivity concentrations with high accuracy. For example, a radioactivity measuring device disclosed in Patent Document 1 is known as a conventional technology for measuring radioactivity concentration with high accuracy. As shown in Figures 1, 2, 5, etc. of the document, this radioactivity measuring device detects the radioactivity distribution of a radioactivity measurement target 1 with high accuracy by bringing a plate-shaped radiation detection unit 10 close to the radioactivity measurement target 1 on a tray. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-173652 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the radioactivity measuring device in Patent Document 1 cannot measure the radioactivity distribution of objects that cannot be placed on a tray, and therefore has the problem of being unable to identify waste with high radioactivity concentrations from large amounts of waste items in actual use environments (for example, piping and valves installed in a plant).

[0006] Furthermore, in environments with strong radiation, such as nuclear power plants, workers' working hours are limited to reduce their exposure. Therefore, in order to measure the radioactivity concentration of waste materials (pipes, valves, etc.) that are installed in the nuclear power plant, it was necessary to plan a detector layout that would allow the series of installation, measurement, and removal tasks to be completed in a short period of time, while also being able to measure the radioactivity distribution of the waste materials with high accuracy, before the measurement work began.

[0007] Therefore, the present invention aims to provide a radiation measurement planning support system and a measurement planning support method that support the creation of detector placement plans that enable highly accurate measurement of the radioactivity of materials to be disposed of in an actual usage environment, while also enabling installation, measurement, and removal operations to be completed in a short period of time. [Means for solving the problem]

[0008] In order to solve the above problems, the measurement planning support system of the present invention is a measurement planning support system that supports the creation of a layout plan for radiation detectors that measure the radioactive concentration of waste, and is equipped with a shape mesh generation unit that generates a three-dimensional shape mesh model of the waste, a mesh development unit that develops the shape mesh model into a two-dimensional planar mesh development, a local contamination mode database that records a plurality of local contamination modes that two-dimensionally express the state of local contamination, a local contamination mode assignment unit that assigns a local contamination mode obtained from the local contamination mode database to any mesh on the planar mesh development, a three-dimensional dose rate calculation unit that restores the planar mesh development to which the local contamination mode has been assigned into a three-dimensional shape mesh model and calculates a three-dimensional dose rate of radiation from local contamination on the shape mesh model, and a detector layout calculation unit that calculates the layout of radiation detectors that detect radiation from the local contamination. [Effects of the Invention]

[0009] The radiation measurement planning support system or measurement planning support method of the present invention can support the creation of plans for detector placement that allows for highly accurate measurement of the radioactivity of items to be disposed of in an actual usage environment, while also enabling installation, measurement, and removal work to be completed in a short period of time. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a functional block diagram of a measurement plan support system according to an embodiment. [Figure 2] FIG. 10 is an explanatory diagram of a method for recording an outline of a contamination range. [Figure 3] FIG. 10 is an explanatory diagram of local contamination modes recorded in a local contamination mode database. [Figure 4] An example of a 3D valve geometry mesh generated by the equipment geometry mesh generator. [Figure 5] 10 shows an example of a method for expanding a geometric mesh into a plane mesh by a mesh expansion unit. [Figure 6] An example of local contamination mode assignment to a plane mesh by the local contamination mode assignment unit. [Figure 7] An example of the allocation of contamination sources to geometric meshes by the 3D dose rate calculation section. [Figure 8] An example of detector layout calculated by the detector layout calculation unit. [Figure 9] An example of a table representation of the detector layout calculated by the detector layout calculation unit. [Figure 10] 1 is a process flowchart of a measurement plan support system according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the measurement planning support system of the present invention will be described below with reference to the drawings. Note that the following will illustrate a situation in which the placement of radiation detectors around waste (pipes, valves, etc.) installed in a nuclear power plant is planned before the radioactivity concentration of the waste is measured. However, the environment in which the present invention is used is not limited to this example, and the present invention may be used in other environments, such as hospitals, as long as the environment is one in which radioactively contaminated waste is present.

[0012] FIG. 1 is a functional block diagram of a measurement planning support system 100 according to this embodiment. As shown in the figure, the measurement planning support system 100 according to this embodiment includes an input unit 1, an output unit 2, a measurement range selection unit 3, an equipment shape mesh generation unit 4, a mesh development unit 5, a local contamination mode assignment unit 6, a 3D dose rate calculation unit 7, a detector placement calculation unit 8, a plant model database DB1, a general contamination range database DB2, a local contamination mode database DB3, and a detector specification database DB4. The configuration within the dashed line in FIG. 1 specifically represents a computer including a calculation device such as a CPU, a storage device such as a semiconductor memory, and hardware such as a communication device. The calculation device executes a predetermined program to realize various functional units, such as the measurement range selection unit 3. Below, the details of each unit will be sequentially described, omitting such well-known techniques as appropriate.

[0013] The plant model database DB1 is a database that records a 3D model of the entire nuclear power plant. Therefore, by referencing this database, it is possible to obtain not only the 3D connection relationships of the pipes, valves, and other components of the nuclear power plant, but also the 3D shapes of each component.

[0014] The general contamination extent database DB2 is a database that records the general contamination extent of the entire nuclear power plant. Therefore, by referring to this database, it is possible to identify the general contamination extent of the nuclear power plant. Note that this database is a database that registers the general contamination extent that workers have conducted simple surveys in advance, and does not have the measurement accuracy to identify the radioactivity concentration of each part of the waste.

[0015] FIG. 2 illustrates a method for easily investigating the extent of contamination of plant components in an actual operating environment. In this example, an operator installs three radiation detectors 9 (9a, 9b, and 9c) near the approximately cylindrical plant component at the positions shown in the figure and performs simple measurements of the radiation dose at each position in a short time. A distance measuring camera 10 is also installed at the position shown in the figure to measure the relative positions of the plant component and radiation detectors 9a through 9c. If the radiation measured by radiation detector 9a is strong, the radiation measured by radiation detector 9c is weak, and the radiation measured by radiation detector 9b is medium, it can be estimated that the contamination area is located near radiation detector 9a of the plant component. This estimation result is recorded as a rough contamination area in the rough contamination area database DB2. By performing this procedure at various locations in the plant, the rough contamination area of ​​the entire nuclear power plant can be registered.

[0016] The local contamination mode database DB3 is a database that records a plurality of local contamination modes that are two-dimensional representations of the local contamination patterns of highly radioactive waste.

[0017] Figure 3 illustrates several local contamination modes R, which are based on the assumption that the radioactivity concentration of the contamination source is normally distributed. Here, mode R1, in which only one local contamination exists within a specified range, mode R2, in which two local contaminations exist close together within a specified range, and mode R3, in which two local contaminations exist somewhat apart within a specified range, are illustrated. However, modes with more local contaminations within a specified range may also be prepared, or modes with multiple local contaminations with different radioactivity concentrations within a specified range may also be prepared. Furthermore, modes with a predetermined rotation of modes R2, R3, etc. may also be prepared.

[0018] The detector specification database DB4 is a database that records the specifications of the radiation detectors 9 used when measuring the radioactivity concentration of waste. The specifications of the radiation detectors 9 recorded here include, for example, the volume of the radiation detector 9, measurement efficiency, and the standard number of radiation detectors 9 used in combination to measure the radioactivity of one piece of waste. If the measurement efficiency of the radiation detectors 9 is high, it is possible to shorten the time required to complete measurement with a predetermined accuracy, and also to reduce the number of radiation detectors 9 used in combination to achieve measurement with a predetermined accuracy.

[0019] The input unit 1 is a man-machine interface such as a keyboard, a mouse, or a touch panel, and is used when an operator inputs desired information into the measurement plan support system 100 .

[0020] The output unit 2 is a man-machine interface such as a liquid crystal display, and is used when the measurement plan support system 100 presents desired information to the operator.

[0021] The measurement range selection unit 3 is a functional unit that selects plant components to be measured from the entire nuclear power plant based on the outputs of the input unit 1, the plant model database DB1, and the general contamination range database DB2. Specifically, when a 3D model of the entire nuclear power plant (output of the plant model database DB1) and the general contamination range (output of the general contamination range database DB2) are displayed on the liquid crystal display (output unit 2), the operator operates a mouse or the like (input unit 1) to specify a partial area of ​​the nuclear power plant (such as a specific floor or a specific room). Then, upon receiving this specification, the measurement range selection unit 3 selects the plant components within the specified area as the measurement targets.

[0022] The equipment geometry mesh generator 4 is a functional unit that generates a three-dimensional geometry mesh of each plant component selected by the measurement range selector 3 with reference to the plant model database DB1.

[0023] Fig. 4 shows an example of a three-dimensional geometric mesh model generated for valve B by the equipment geometric mesh generator 4 when valve B is included in the plant components selected by the measurement range selector 3. As shown in the figure, the position of each mesh in Fig. 4 can be specified by an xyz coordinate system in which three axes intersect at right angles.

[0024] The mesh development unit 5 is a functional unit that develops the 3D shape mesh model generated by the equipment shape mesh generation unit 4 into a 2D planar mesh. When the equipment shape mesh generation unit 4 generates a shape mesh model for a complexly shaped plant component, the curvature and shape of the shape mesh vary greatly for each part. In such cases, it becomes cumbersome to define the information on the correspondence between arbitrary shape meshes using an xyz coordinate system. Therefore, the mesh development unit 5 of this embodiment converts various shape meshes with different curvatures and shapes into 2D planar meshes with standardized shapes, and then makes it possible to easily define the information on the correspondence between arbitrary meshes using a uv coordinate system with two orthogonal axes.

[0025] Figure 5 illustrates a method for expanding the geometric mesh of the inner surface of valve B in Figure 4 into a planar mesh. The left side of Figure 5 is a virtual cross-section of the geometric mesh model of valve B in Figure 4 at cross section A. As shown in Figures 4 and 5, the approximately cylindrical valve B has a flow path penetrating from its upper end to its lower end, with an ellipsoidal inflation channel formed in the center of the flow path. Due to this complex shape of the inner surface of valve B, the geometric mesh generated corresponding to the inner shape of valve B is not uniform. For example, meshes M1 and M2 on the inner surface of the inflation channel have different curvatures and dimensions, making it cumbersome to define their correspondence using an xyz coordinate system. Therefore, the geometric mesh group in the left side of Figure 5 is divided vertically into three regions, and each region is expanded onto planes P1, P2, and P3 using a uv coordinate system, as shown in the right side of Figure 5. This allows the correspondence between meshes M1 and M2, which would be cumbersome to define on a three-dimensional geometric mesh, to be easily defined on a two-dimensional planar mesh.

[0026] The local pollution mode allocation unit 6 is a functional unit that sequentially allocates local pollution modes registered in the local pollution mode database DB3 onto any planar mesh of the plane P developed by the mesh development unit 5.

[0027] FIG. 6 shows an example of a state in which mode R2 (see FIG. 3) registered in the local contamination mode database DB3 is assigned to a predetermined mesh on plane P2 (see FIG. 5). Note that, hereinafter, the local contaminations assigned to plane P2 will be referred to as r1 and r2. In this way, by simulating two contamination sources r1 and r2 that should be assigned three-dimensionally to the inner surface of the expansion passage of valve B on a two-dimensional plane, it is possible to easily specify the assignment positions of the contamination sources. Note that the significance of the assignment of contamination source r by the local contamination mode assignment unit 6 will be described later.

[0028] The three-dimensional dose rate calculation unit 7 is a functional unit that assigns the contamination source r to a geometric mesh corresponding to the planar mesh to which the contamination source r is assigned, and then calculates the three-dimensional dose rate of radiation from the contamination source r, assuming that the radioactivity concentration of the contamination source r on the geometric mesh is normally distributed.

[0029] Fig. 7 shows a state in which contamination sources r1 and r2 on plane P2 shown in the right diagram of Fig. 6 are assigned to corresponding geometric meshes in the geometric mesh model of valve B. In this case, the three-dimensional dose rate calculation unit 7 assumes that contamination sources r1 and r2 with predetermined radioactivity concentrations are located at the two locations shown in the diagram, and can calculate the three-dimensional dose rate of radiation in the vicinity of valve B by using the Monte Carlo method or the like.

[0030] The detector placement calculation unit 8 is a functional unit that calculates the appropriate placement (coordinates, direction) of the radiation detector 9 based on the specifications of the radiation detector 9 obtained from the detector specification database DB4 and the three-dimensional dose rate calculated by the three-dimensional dose rate calculation unit 7.

[0031] FIG. 8 shows an example of an appropriate placement of the radiation detectors 9 (90-94) when the number of concurrent uses specified in the detector specification database DB4 is five. In this example, the first radiation detector 90 is provisionally placed in the direction (e.g., on the normal vector of the contamination source r) where the three-dimensional dose rate calculated by the three-dimensional dose rate calculation unit 7 is maximized. Next, the distance from the contamination source r to the radiation detector 90 is determined taking into consideration the volume of the radiation detector 90, the measurement efficiency [%], the radioactivity of the contamination source r [Bq = counts / s], the planned measurement time, and other factors. This identifies the placement (coordinates, direction) of the radiation detector 90. The remaining four radiation detectors 91-94 are then placed on the surface of a virtual sphere with the contamination source r at its center and the distance from the contamination source r to the radiation detector 90 as its radius. It is desirable to evenly place the radiation detectors 91-94 with the line of sight of the radiation detector 90 as the axis. This detector placement enables the radioactivity concentration of the valve B to be measured with high accuracy using a small number of radiation detectors 9.

[0032] <Flowchart> Next, the procedure of the process for supporting creation of a layout plan for the radiation detectors 9 by the measurement plan support system 100 of this embodiment will be described with reference to the flowchart of FIG.

[0033] In step S1, the measurement range selection unit 3 selects a measurement range for the plant. Specifically, the measurement range selection unit 3 first acquires a three-dimensional model of the entire nuclear power plant from the plant model database DB1, and acquires general contamination measurement data from the general contamination range database DB2. Thereafter, the measurement range selection unit 3 notifies the operator of the general contamination range for the entire nuclear power plant via the output unit 2 (liquid crystal display). Then, when the operator who has received the notification inputs the desired measurement range, the measurement range selection unit 3 selects the equipment (plant components) to be measured that are included in the measurement range input by the operator.

[0034] In step S2, the equipment geometry mesh generator 4 generates a geometry mesh model of the measurement target equipment selected in step S1 based on the three-dimensional model also acquired in step S1 (see FIG. 4).

[0035] In step S3, the mesh development unit 5 converts the geometric mesh model generated in step S2 into a planar mesh development view (see FIG. 5).

[0036] In step S4, the local contamination mode allocation unit 6 acquires a local contamination mode from the local contamination mode database DB3 (see FIG. 3). Note that even if multiple local contamination modes are recorded in the local contamination mode database DB3, any one of the local contamination modes is acquired in this step.

[0037] In step S5, the local contamination mode assigning unit 6 assigns the local contamination mode acquired in step S4 to any one of the meshes in the planar mesh development prepared in step S3 (see FIG. 6).

[0038] In step S6, the three-dimensional dose rate calculation unit 7 restores the planar mesh development to which the local contamination was assigned in step S5 into a three-dimensional geometric mesh model (see FIG. 7), and calculates the three-dimensional dose rate around the measurement target device, assuming that there is local contamination at that position. Note that, as described above, the Monte Carlo method or the like can be used for this calculation.

[0039] In step S7, the detector arrangement calculation unit 8 acquires the specification data of the radiation detector 9 from the detector specification database DB4.

[0040] In step S8, the detector arrangement calculation unit 8 arranges n radiation detectors 9 around the local contamination in the three-dimensional geometric mesh model restored in step S6, and calculates the coordinates and line of sight direction of each radiation detector (see FIG. 8). Note that the above n may be the number of concurrent uses specified by the specification data acquired in step S7, or may be a number specified by the operator.

[0041] In step S9, the detector arrangement calculation unit 8 calculates the radiation dose when the three-dimensional dose rate calculated in step S6 is detected by the group of radiation detectors 9 arranged in step S8.

[0042] In step S10, the detector placement calculation unit 8 compares the general contamination distribution obtained from the general contamination range database DB2 with the radiation dose distribution calculated in step S9, and calculates the sum of squares of the differences in the representative coordinates of the contamination concentration curve. From this calculation result, the likelihood of the position to which local contamination was assigned in step S5 can be estimated.

[0043] In step S11, the local pollution mode allocation unit 6 determines whether the local pollution mode acquired in step S4 has been assigned to all meshes. If the requirements are met, the process proceeds to step S12. On the other hand, if the requirements are not met, the process proceeds to step S5, where the local pollution mode is assigned to other meshes, and the processes from step S6 to step S10 are performed again.

[0044] In step S12, the local contamination mode allocation unit 6 determines whether the processing from step S5 to step S10 has been completed for all local contamination modes registered in the local contamination mode database DB3. If the requirements are met, the process proceeds to step S13. On the other hand, if the requirements are not met, the process proceeds to step S4, where another local contamination mode is acquired, and the processing from step S5 to step S11 is performed again.

[0045] Finally, in step S13, the detector placement calculation unit 8 identifies the smallest sum of squares from the many sums of squares calculated in step S10, which is repeated depending on the number of meshes and the number of local contamination modes. The local contamination mode when this smallest sum of squares was calculated and the position of the mesh to which that local contamination mode is assigned are similar to the actual contamination status of the equipment to be measured, and the placement of the radiation detectors 9 corresponding to this is considered to be the optimal placement for measuring the actual contamination status. Therefore, the detector placement calculation unit 8 outputs the placement of the radiation detectors 9 when the smallest sum of squares was calculated as a detector placement plan (S14).

[0046] Figure 9 is an example of a tabular detector layout plan displayed on the liquid crystal display (output unit 2). In this Table 1, an identification number is assigned to each radiation detector 9, and the coordinates of the detector center, direction, detection efficiency, measurement time, etc. are output in tabular form. Note that an illustration such as that in Figure 8 may be displayed directly on the liquid crystal display (output unit 2) as the detector layout plan.

[0047] As described above, the measurement planning support system of this embodiment can assist in creating a plan for detector placement that allows for highly accurate measurement of the radioactivity of waste materials in the actual usage environment, while also enabling installation, measurement, and removal work to be completed in a short period of time. [Explanation of symbols]

[0048] 100 Measurement Planning Support System 1 Input section 2 Output section 3 Measurement range selection section 4. Equipment geometry mesh generation section 5 Mesh development section 6 Local contamination mode assignment section 7. 3D dose rate calculation section 8. Detector layout calculation section 9. Radiation detectors 10 Range finding camera DB1 Plant Model Database DB2 Contamination Summary Database DB3 Local Contamination Mode Database DB4 Detector Specification Database

Claims

1. A measurement planning support system that supports the creation of a layout plan for radiation detectors that measure radioactivity concentrations in waste, a shape mesh generation unit that generates a three-dimensional shape mesh model of the waste; a mesh development unit that develops the shape mesh model into a two-dimensional planar mesh development diagram; a local contamination mode database that records a plurality of local contamination modes that are two-dimensional representations of local contamination modes; a local contamination mode allocation unit that sequentially allocates local contamination modes selected from the local contamination mode database to all meshes of the planar mesh development; a three-dimensional dose rate calculation unit that reconstructs the planar mesh development to which the local contamination mode is assigned into a three-dimensional geometric mesh model and calculates a three-dimensional dose rate of radiation from the local contamination on the geometric mesh model; a detector arrangement calculation unit that calculates an arrangement of a radiation detector that detects radiation from the local contamination; A measurement planning support system comprising:

2. 2. The measurement planning support system according to claim 1, wherein the detector placement calculation unit calculates placement of the radiation detectors for local contamination on the shape mesh model when the local contamination mode assignment unit sequentially selects a plurality of local contamination modes recorded in the local contamination mode database and sequentially selects meshes of the planar mesh development to which the local contamination mode is assigned, and calculates a three-dimensional dose rate that approximates a general contamination range measured in advance from a plurality of three-dimensional dose rates calculated by the three-dimensional dose rate calculation unit under each situation.

3. 3. The measurement planning support system according to claim 2, A measurement planning support system characterized in that the three-dimensional dose rate approximating the general contamination range measured in advance is a three-dimensional dose rate for which the sum of squares of the difference between the representative coordinates of the contamination concentration curve of the general contamination range and the representative coordinates of the contamination concentration curve of the three-dimensional dose rate is minimum.

4. The measurement plan support system according to any one of claims 1 to 3, A measurement planning support system characterized in that the detector placement calculation unit places radiation detectors in the number specified by specifications or the number specified by the operator at coordinates and directions that allow the radioactive concentration of the waste to be measured within a set measurement time.

5. 5. The measurement planning support system according to claim 4, The measurement planning support system is characterized in that the detector arrangement calculation unit arranges a plurality of radiation detectors on the surface of a virtual sphere centered on the local contamination.

6. A measurement planning support method for supporting the creation of a layout plan for radiation detectors that measure radioactive concentrations of waste, comprising: a shape mesh generation step of generating a three-dimensional shape mesh model of the waste; a mesh development step of developing the shape mesh model into a two-dimensional planar mesh development diagram; a local contamination mode assignment step of sequentially assigning local contamination modes selected from a local contamination mode database in which a plurality of local contamination modes, each representing a mode of local contamination in two dimensions, are recorded to all meshes of the planar mesh development; a three-dimensional dose rate calculation step of restoring the planar mesh development to which the local contamination mode has been assigned into a three-dimensional geometric mesh model and calculating a three-dimensional dose rate of radiation from the local contamination on the geometric mesh model; a detector placement calculation step of calculating placement of a radiation detector for detecting radiation from the local contamination; A measurement planning support method comprising:

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