JP6582558B2 - Dose prediction apparatus, dose prediction method, and dose prediction program - Google Patents

Description

  The present invention relates to a dose prediction apparatus, a dose prediction method, and a dose prediction program for predicting a radiation dose from a radiation source.

  When the radiation dose distribution in the environment is predicted (evaluated), the radiation dose from the radiation source is predicted using a dose prediction program. As a typical example of a dose prediction program, a radiation transport calculation code by the Monte Carlo method (hereinafter referred to as a Monte Carlo transport calculation code) is known. The Monte Carlo method is a calculation method for obtaining an approximate solution by performing simulations using random numbers many times. The Monte Carlo transport calculation code uses the Monte Carlo method to calculate radiation transport calculations (such as the scattering and absorption of a large number of particles in a system and the leakage of particles outside the system), and calculates the radiation dose in a given environment. The calculation code to be evaluated. For example, Patent Document 1 below discloses a method for evaluating the degree of activation of a shield region having a nuclear reactor equipment or shield using a Monte Carlo transport calculation code.

JP 2014-238358 A

  When predicting (evaluating) radiation dose using a dose prediction program, the evaluation target 3D shape model (3D shape information) is automatically generated based on the evaluation target dimensions such as radiation sources and shields, CAD data, etc. A program to be created automatically has been developed. However, the creation of a three-dimensional shape model by such a program simulates an actual evaluation object by combining simple geometric shapes such as a flat plate and a cylinder. Accordingly, the shapes that can be handled as the shape of the evaluation target such as a radiation source or a shield are limited. That is, it is difficult to create a three-dimensional shape model having a complicated geometric shape. For this reason, for example, when the evaluation target is not composed of a combination of simple geometric shapes such as natural terrain, a difference between the evaluation target three-dimensional shape model and the actual evaluation target shape is generated, and dose prediction is performed based on the difference. An error occurs in the prediction result (calculation result) by the program.

  In addition, a dose prediction program such as a Monte Carlo transport calculation code is generally used to predict a radiation dose in an environment where the position of a radiation source exists locally or limitedly. For example, it is often used for radiation dose prediction in shielding designs such as nuclear facilities and medical facilities. Therefore, when the position of the radiation source to be evaluated does not exist locally or in a limited manner, that is, when the radiation source is distributed over a wide area, the radiation dose from the radiation source is set to one place (locally). Must be evaluated. For this reason, it takes an enormous amount of time to evaluate the radiation dose from all radiation sources distributed over a wide range.

  The present invention has been made in view of the above-described circumstances, can simulate the shape model to be evaluated as faithfully as possible, and requires a huge amount of time even when the radiation source is distributed over a wide range. It is an object of the present invention to provide a dose prediction apparatus, a dose prediction method, and a dose prediction program that can obtain a prediction result without any problem.

  In order to achieve the above object, the present invention divides a shape surface of a three-dimensional shape model into a mesh shape and a CG processing unit that sets radiation source information indicating the intensity of the radiation source on the shape surface of the three-dimensional shape model. Sets a plurality of meshes, sets a plurality of cells in each mesh, sets a radiation source having a radiation intensity corresponding to the radiation source information in each cell, and sets a calculation point at a predetermined position. There is provided a dose prediction apparatus including a second information setting unit and a dose calculation processing unit that calculates a radiation dose at a calculation point from a radiation source set in each cell.

  Moreover, the structure provided with the subdivision process part which subdivides a mesh by dividing | segmenting the cell with a short distance from a calculation point may be sufficient. In addition, the subdivision processing unit has an angle formed by a line connecting the center of the equivalent circle equal to the cell area and the calculation point and a line connecting the predetermined position on the circumference of the equivalent circle and the calculation point equal to or greater than a certain angle. In this case, the cell may be divided.

  The first information setting unit may be configured to set a point source in a layered manner in the depth direction of each cell for each cell. Moreover, the structure which sets the intensity distribution of the depth direction of the point source of each layer with respect to each cell may be sufficient as a 1st information setting part.

The CG processing unit may be configured to create a three-dimensional shape model based on topographic data, altitude data, and structure shape data. The CG processing unit may be configured to set radiation source information with color information on the shape surface of the three-dimensional shape model. The CG processing unit sets radiation source information on the shape surface of the three-dimensional shape model based on the radiation source intensity distribution before and after decontamination, and the radiation dose distribution image before and after decontamination calculated by the dose calculation processing unit. The structure which produces | generates may be sufficient. The dose calculation processing unit may be configured to calculate the radiation dose at the calculation point from the radiation source set in each cell based on the point attenuation kernel calculation method.

  Also, a line-of-sight determination unit that determines whether or not an object exists between a calculation point and each cell, and if the line-of-sight determination unit determines that an object exists between the calculation point and each cell, A shielding calculation processing unit that calculates the attenuation of radiation from the radiation source of each cell, and the dose calculation processing unit calculates the radiation dose at the calculation point in consideration of the radiation attenuation calculated by the shielding calculation processing unit. The structure to do may be sufficient. The CG processing unit sets the radiation transmittance on the shape surface of the three-dimensional shape model, and the shielding calculation processing unit performs radiation from the radiation source of each cell by the object based on the radiation transmittance and the thickness of the object. It is also possible to use a configuration for calculating the attenuation.

  Further, the present invention sets radiation source information indicating the intensity of the radiation source on the shape surface of the three-dimensional shape model, and sets a plurality of meshes by dividing the shape surface of the three-dimensional shape model into mesh shapes. Set multiple cells in each mesh, set a radiation source of radiation intensity according to the radiation source information in each cell, set a calculation point at a predetermined position, and from the radiation source set in each cell And calculating a radiation dose at a calculation point of

  In addition, the present invention provides a computer with CG processing for setting radiation source information indicating the intensity of a radiation source on the shape surface of a three-dimensional shape model, and dividing the shape surface of the three-dimensional shape model into a mesh shape. A first information setting process for setting a plurality of cells in each mesh and setting a radiation source having a radiation intensity corresponding to the radiation source information in each cell; and a second information setting for setting a calculation point at a predetermined position Provided is a dose prediction program that executes a process and a dose calculation process for calculating a radiation dose at a calculation point from a radiation source set in each cell.

  According to the present invention, a CG processing unit that sets radiation source information indicating the intensity of the radiation source on the shape surface of the three-dimensional shape model, and a plurality of meshes are set by dividing the shape surface of the three-dimensional shape model into a mesh shape In addition, a first information setting unit that sets a plurality of cells in each mesh, sets a radiation source having a radiation intensity corresponding to the radiation source information in each cell, and a second information setting unit sets a calculation point at a predetermined position; And a dose calculation processing unit for calculating a radiation dose at a calculation point from the radiation source set in each cell. According to such a configuration, the three-dimensional shape model to be evaluated can be simulated as faithfully as possible. As a result, the difference between the three-dimensional shape model to be evaluated and the three-dimensional shape to be actually evaluated is reduced, and the error in the calculation result of the radiation dose can be reduced. In addition, by setting a radiation source in each cell, a calculation result (prediction result) at a calculation point can be obtained without requiring an enormous amount of time even when the radiation source is distributed over a wide range.

It is a figure which shows the control program with which the dose prediction apparatus of this invention is provided, and the information processed with the control program. It is a block diagram which shows the structure of the dose prediction apparatus which concerns on 1st Embodiment. It is a figure which shows the state by which the mesh of the several unit area | region was set to the three-dimensional shape model. It is a figure which shows the cell in the mesh shown in FIG. It is a figure which shows the structure of a layered volume radiation source model. It is a figure for demonstrating the division | segmentation of a cell. It is a flowchart which shows an example of the production | generation process of an input file. It is a flowchart which shows an example of the calculation process of an air dose. It is a figure which shows the state which subdivided the mesh of the three-dimensional shape model shown in FIG. It is a block diagram which shows an example of the dose prediction apparatus which concerns on 2nd Embodiment. It is a figure which shows an example of the analysis information mesh for demonstrating a vision determination process. It is a figure which shows the modification of intensity distribution of a radiation source.

  Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to this. Further, in the drawings, in order to describe the embodiment, the scale may be appropriately changed and expressed, for example, partly enlarged or emphasized.

<First Embodiment>
A control program provided in the dose prediction apparatus of the present invention and information processed by the control program will be described. FIG. 1 is a diagram showing a control program provided in the dose prediction apparatus of the present invention and information processed by the control program. The dose prediction apparatus of the present invention shown in FIG. 1 includes a three-dimensional CG program 200 (a three-dimensional computer graphics program) and a dose prediction program 210 as control programs. The three-dimensional CG program 200 is a program for creating (modeling) a three-dimensional shape model and generating (rendering) an image of the three-dimensional shape model. The dose prediction program 210 is a program for predicting the radiation dose from the radiation source.

  The three-dimensional CG program 200 inputs information 100 to be calculated. As shown in FIG. 1, the calculation target information 100 includes information such as terrain data (map data), elevation data, building shape data, radiation source intensity distribution before and after decontamination, surface radiation transmittance, and the like.

  Here, the terrain data is two-dimensional data indicating the terrain (map) in the region to be evaluated by the dose prediction device, and the altitude data is data indicating the altitude of each point of the terrain data. Moreover, the shape data of a building etc. is three-dimensional data which shows the shape of the building etc. which exist in the evaluation object area | region by a dose prediction apparatus. The radiation source intensity distribution is data indicating, for example, a measurement value (a space dose rate [μSv / h] having a height of 1 cm) obtained by monitoring or the like at each point in the region to be evaluated by the dose prediction apparatus. If the area to be evaluated by the dose prediction device is an area contaminated with radioactive material, the operator must determine the radiation source intensity distribution before decontamination and the radiation source intensity distribution after decontamination. Input to the three-dimensional CG program 200. The surface radiation transmittance is data indicating the radiation transmittance of the surface in the area to be evaluated by the dose prediction apparatus.

  The three-dimensional CG program 200 creates a three-dimensional shape model based on topographic data, elevation data, and shape data such as buildings. For example, the three-dimensional CG program 200 reproduces the three-dimensional shape of the terrain of the evaluation target region with a polygon mesh based on the terrain data and the elevation data, and exists in the evaluation target region based on the shape data of the building or the like. A three-dimensional shape model in an evaluation target area is created by reproducing a three-dimensional shape of a building or the like to be evaluated with a polygon mesh.

  The three-dimensional CG program 200 sets radiation source information indicating the intensity of the radiation source on the shape surface of the three-dimensional shape model based on the radiation source intensity distribution. Specifically, the three-dimensional CG program 200 texture-maps color information (for example, 256 tone color information) corresponding to the radiation source intensity on each polygon mesh on the shape surface of the three-dimensional shape model. For example, on the shape surface of the three-dimensional shape model, a portion having a relatively high radiation source intensity is red, and a portion having a relatively low radiation source intensity is blue.

  As described above, the three-dimensional shape model created by the three-dimensional CG program 200 and the radiation source information set as color information on the shape surface (each polygon mesh) of the three-dimensional shape model by the three-dimensional CG program 200 are analyzed information. 110. The three-dimensional CG program 200 can generate a three-dimensional shape model and radiation source information (color information) as CG common format data (common format data in a general-purpose three-dimensional CG program). The three-dimensional CG program 200 outputs the CG common format analysis information 110 to the dose prediction program 210.

  The dose prediction program 210 receives analysis information 110 (three-dimensional shape model, radiation source information) output from the three-dimensional CG program 200. In addition, the dose prediction program 210 inputs the setting information 120 that is text data in accordance with the operation of the operation unit (keyboard 2 and mouse 3 shown in FIG. 2) by the operator. As shown in FIG. 1, the setting information 120 includes calculation control information, model options, calculation point coordinates, radiation-related data, and the like.

  Here, the calculation control information includes information such as coefficients and setting values in the calculation method (approximate calculation method) when calculating the radiation dose, and the position (hereinafter, calculation point or evaluation point) where the radiation dose is calculated in the evaluation target area. Including information indicating the number of. The model option is a radiation source model (in this embodiment, a model in which point sources are considered to be deposited in layers in the thickness direction (depth direction) of each cell; see the layered volume source model shown in FIG. ) Is information indicating the distribution status of the radiation source. The calculation point coordinates are information indicating the three-dimensional coordinates of the calculation points. The radiation-related data is information such as the composition ratio of radionuclides in the radiation source. The analysis information 110 and the setting information 120 are called input files.

  The dose prediction program 210 reads the input file and calculates the radiation dose (radiation intensity) at the calculation point based on the analysis information 110 and the setting information 120 included in the input file. Then, the dose prediction program 210 outputs a calculation result 130 including information such as a dose distribution before and after decontamination and a dose reduction ratio in the evaluation target area to the three-dimensional CG program 200. The calculation result 130 is generated as CG common format data. Further, the dose prediction program 210 outputs a detailed calculation result 140, which is text data, to a display device (see FIG. 2).

  The three-dimensional CG program 200 calculates the dose distribution before and after decontamination in the three-dimensional shape model based on information such as the dose distribution before and after decontamination and the dose reduction ratio in the evaluation target area included in the calculation result 130. An image showing the dose distribution and dose reduction ratio before and after decontamination is generated. Thereby, the dose distribution and dose reduction ratio before and after decontamination can be visually recognized.

  FIG. 2 is a block diagram showing the configuration of the dose prediction apparatus 1 according to the first embodiment. A dose prediction apparatus 1 according to the first embodiment shown in FIG. 2 is an apparatus that predicts (evaluates) a radiation dose from a radiation source. In the present embodiment, the dose prediction apparatus 1 predicts the distribution of radiation dose from radiation sources distributed over a wide range. The dose prediction apparatus 1 is configured by a computer, for example. As shown in FIG. 2, the dose prediction device 1 is connected to a display device 2, a keyboard 3, and a mouse 4.

  As shown in FIG. 2, the dose prediction apparatus 1 includes an arithmetic processing unit 10 and a storage unit 20. The arithmetic processing unit 10 performs overall control related to radiation dose prediction. The storage unit 20 includes various control programs (such as the three-dimensional CG program 200, the dose prediction program 210, and the operating system (not shown) shown in FIG. 1) for causing the arithmetic processing unit 10 to execute various types of processing. Information necessary for processing (calculation target information 100, analysis information 110, setting information 120 shown in FIG. 1), calculation result information (calculation result 130 and detailed calculation result 140 shown in FIG. 1), and the like are stored. .

  As shown in FIG. 2, the arithmetic processing unit 10 includes a display control unit 11, a data input unit 12, a CG processing unit 13, an information setting unit 14 (first information setting unit, second information setting unit), and a subdivision processing unit. 15 and a dose calculation processing unit 16. The display control unit 11 and the data input unit 12 correspond to processing or control executed by an arithmetic device such as a CPU (Central Processing Unit) based on an operating system, and the CG processing unit 13 has a three-dimensional CG. The information setting unit 14, the segmentation processing unit 15, and the dose calculation processing unit 16 correspond to processing or control executed by the arithmetic device based on the dose prediction program 210. .

  The display control unit 11 controls the display of information on the display device 2 such as a liquid crystal display. For example, the display control unit 11 displays on the display screen of the display device 2 a control for displaying an image of a three-dimensional shape model generated by the CG processing unit 13 and an image of an information input area for inputting various information. Control to perform. The data input unit 12 is connected to the keyboard 3 and the mouse 4. The data input unit 12 inputs information (calculation target information 100, setting information 120, etc.) according to the operation of the keyboard 3 and mouse 4 by the operator.

  The CG processing unit 13 is a processing unit that performs CG processing (computer graphics processing). The CG processing unit 13 is a process (modeling process) for creating a three-dimensional shape model (three-dimensional shape information) based on terrain data, elevation data, the shape of a building, etc., and applies radiation to each polygon mesh of the three-dimensional shape model. Performs processing to set source information. The CG processing unit 13 performs processing (rendering processing) for generating an image of three-dimensional shape information. The CG processing unit 13 also visually represents the decontamination effect based on the calculation results 130 calculated by the dose calculation processing unit 16 (dose distribution before and after decontamination, dose reduction ratio, etc.). Are displayed on the display device 2.

  The information setting unit 14 resets the three-dimensional shape model of the CG common format created by the CG processing unit 13 to another format (data format for calculation processing by the dose prediction program 210). Then, the information setting unit 14 sets a plurality of unit region meshes on the shape surface of the three-dimensional shape model by dividing the shape surface of the three-dimensional shape model created by the CG processing unit 13 into a mesh shape. The meshes of the plurality of unit regions may be the same size region as the polygon mesh in the three-dimensional shape model created by the CG processing unit 13 or a different size region. Further, the information setting unit 14 calculates the intensity of the radiation source for each mesh unit based on the radiation source information (color information) set on the shape surface of the three-dimensional shape model.

  FIG. 3 is a diagram illustrating a state where a plurality of unit area meshes are set in the three-dimensional shape model 300. In the three-dimensional shape model 300 shown in FIG. 3, objects 310 and 320 such as buildings are provided. The three-dimensional shape model 300 is divided into a plurality of square unit regions meshes M by a plurality of orthogonally spaced lines. In the three-dimensional shape model 300, the region 300a is a low radiation source region, and the region 300b is a high radiation source region. The intensity of the radiation source set for each mesh M of the high radiation source region 300b is higher than the intensity of the radiation source set for each mesh M of the low radiation source region 300a. In FIG. 3, a calculation point 400 is set at a height of a predetermined distance from the ground surface (a position away from the ground surface by a predetermined distance). Although the height of the calculation point 400 is arbitrary, for example, a height of 1 m is basically used.

  Returning to the description of FIG. 2, the information setting unit 14 divides each mesh set on the shape surface of the three-dimensional shape model into four cells. Then, the information setting unit 14 sets a point source for each cell.

  FIG. 4 is a diagram illustrating cells Sel1 to Sel4 in the mesh M illustrated in FIG. Each mesh M is specified by position information of four vertices p1 to p4. The phase shape of the three-dimensional shape model cannot be constituted by the mesh M on the plane constituted by the four vertices p1 to p4. Therefore, by adding the vertex p5 to the center of the mesh M, the mesh M is divided into four cells Sel1 to Sel4. Also, the information setting unit 14 assumes that there are virtual point sources r1 to r4 at the centers (or centroids) of the divided cells Sel1 to Sel4 based on the intensity of the radiation source of each entire mesh. The dose of each point source r1 to r4 is calculated. Then, the information setting unit 14 sets the point line sources r1 to r4 at the centers (or centroids) of the cells Sel1 to Sel4, respectively.

  Returning to the description of FIG. 2, the information setting unit 14, based on the model option of the setting information 120, dotted lines in layers (layers) in the thickness direction (depth direction) of each cell. Set up a layered volume source model assuming that the source is deposited. Thereby, the radiation source in one layer (layer) is approximated by one point source.

  FIG. 5 is a diagram showing the configuration of the layered volume source model. In FIG. 5, the structure of the hierarchized cell Seli and the intensity distribution in the depth direction of the radiation sources ri1 to rij to rim are shown. Model options include how far the depth (thickness) is in the normal direction (normal vector direction) to the surface of each cell Seli, and how many layers the depth is divided into. Is set. In the example shown in FIG. 5, the cell Seli has m layers (first to j-th to m-th layers) set in the depth direction up to a predetermined depth, and one dotted line for each of the m layers. Sources (point line source ri1 to point line source rij to point line source rim) are set. The information setting unit 14 sets a predetermined number of layers for each cell based on the model option, and sets a predetermined number of point sources for each layer. When the surface of the three-dimensional shape model is soil, the information setting unit 14 sets a depth of, for example, about 4 cm to 5 cm as the cell depth (thickness).

  Also, in the model option, information on the intensity distribution in the depth direction of the point line sources ri1 to rij to rim of each layer is set. In the example shown in FIG. 5, the intensity distribution W1 of the point source ri1 to rij to rim is a uniform distribution whose intensity does not change depending on the depth. The intensity distribution W2 of the point source ri1-rij-rim is a linear decrease (ramp-shaped) distribution in which the intensity decreases linearly as the depth increases. The information setting unit 14 also sets the intensity distribution of the point line sources ri1 to rij to rim of each layer in association with the cell Seli. As described above, the information in which the layered point source is set in the depth direction for each cell constituting the three-dimensional shape model is referred to as an analysis information mesh.

  Returning to the description of FIG. 2, the information setting unit 14 sets a calculation point at a position represented by the calculation point coordinates of the setting information 120. The subdivision processing unit 15 performs a process of subdividing the mesh by dividing cells that are close to the calculation point.

  FIG. 6 is a diagram for explaining cell division. The triangular cell Sel shown in FIG. 6 includes a side having a length L1, a side having a length L2, and a side having a length L3. A point source r is set at the center position (each layer) of the cell Sel. The subdivision processing unit 15 calculates the area of the cell Sel based on the position of the vertex of the cell Sel. Then, the subdivision processing unit 15 assumes an equivalent circle C equal to the area of the cell Sel, and matches the center of the equivalent circle C with the center of the cell Sel. As shown in FIG. 6, the radius of the equivalent circle C is R. The subdivision processing unit 15 obtains an angle α formed by a line connecting the calculation point 400 and the center point of the equivalent circle C and a line connecting the calculation point 400 and a predetermined position on the circumference of the equivalent circle C. The subdivision processing unit 15 divides the cell Sel when the angle α is equal to or larger than a predetermined angle. Note that a predetermined angle is set in the calculation control information of the setting information 120.

  The subdivision processing unit 15 identifies the longest side (the side having the length L1 in the example shown in FIG. 6) among the three sides constituting the cell Sel. Then, the subdivision processing unit 15 divides the cell Sel by a line connecting the point Pd at a predetermined position (for example, the center position of the side) of the specified side and the apex of the cell Sel facing the specified side. In this case, as shown in FIG. 6, the cell Sel is divided into a cell Sel-1 and a cell Sel-2. Such processing is repeatedly executed. By performing the above processing, the cell Sel close to the calculation point 400 is finely divided. When the subdivision processing unit 15 divides the cell, the information setting unit 14 calculates the intensity of the point source of each layer in each cell according to the area of each cell divided by the subdivision processing unit 15. Then, the information setting unit 14 sets a point source for each layer in each divided cell.

  The dose calculation processing unit 16 converts the radiation dose (radiation intensity) at the calculation point 400 from the point source set in layers in each cell constituting the three-dimensional shape model into a point attenuation nuclear calculation method which is a kind of approximate calculation method. Calculate based on. The point decay kernel calculation method will be described later.

  Next, the operation of predicting the radiation dose (radiation intensity) by the dose prediction apparatus 1 will be described.

  FIG. 7 is a flowchart illustrating an example of input file generation processing. In the process shown in FIG. 7, the data input unit 12 inputs the information 100 to be calculated in response to the operation of the keyboard 3 and the mouse 4 by the worker (step S1). The CG processing unit 13 creates a three-dimensional shape model from terrain data, altitude data, etc. in the input information 100 to be calculated (step S2). Further, the CG processing unit 13 sets the radiation source information as color information in each polygon mesh constituting the three-dimensional shape model based on the radiation source intensity distribution in the input information 100 to be calculated (step S3). . Then, the CG processing unit 13 stores the three-dimensional shape model in which the radiation source information is set in the storage unit 20 as the analysis information 110 (Step S4).

  The data input unit 12 inputs analysis information 110 including calculation control information, model options, calculation point coordinates, radiation-related data, and the like according to the operation of the keyboard 3 and the mouse 4 by the operator. 110 is stored in the storage unit 20.

  FIG. 8 is a flowchart illustrating an example of air dose calculation processing. In the process shown in FIG. 8, the information setting unit 14 reads an input file composed of the analysis information 110 and the setting information 120 stored in the storage unit 20 (step S11). Then, the information setting unit 14 sets an analysis information mesh based on the analysis information 110 and setting information 120 of the read input file (step S12).

  That is, as described above, the information setting unit 14 divides the shape surface of the three-dimensional shape model created by the CG processing unit 13 into a mesh shape, thereby meshing a plurality of unit region meshes on the shape surface of the three-dimensional shape model. Set. Further, the information setting unit 14 calculates the intensity of the radiation source for each mesh unit based on the radiation source information (color information) set on the shape surface of the three-dimensional shape model. The information setting unit 14 divides each mesh set on the shape surface of the three-dimensional shape model into four cells. Then, the information setting unit 14 sets a point source for each cell. In addition, the information setting unit 14 sets a layered volume source model in which point sources are accumulated in layers in the depth direction of each cell based on the model option of the setting information 120. To do.

  Next, the information setting unit 14 sets an air dose calculation point (step S13). Then, the segmentation processing unit 15 executes a segmentation process (detailing process) for segmenting the analysis information mesh by dividing a cell that is close to the calculation point set in step S13 (step S14). When the subdivision processing unit 15 divides the cell, the information setting unit 14 calculates the intensity of the point source of each layer in each cell according to the area of each cell divided by the subdivision processing unit 15 and the like. A point source with the intensity obtained is set for each layer.

  FIG. 9 is a diagram showing a state where the mesh of the three-dimensional shape model shown in FIG. 3 is subdivided. As shown in FIG. 9, the mesh in the region 300P near the calculation point 400 is most finely divided. The mesh of the region 300Q next to the calculation point 400 next to the region 300P is coarser than the mesh of the region 300P. The mesh in the region 300R next to the calculation point 400 next to the region 300Q is coarser than the mesh in the region 300Q. The mesh of the region 300S next to the calculation point 400 next to the region 300R is coarser than the mesh of the region 300R.

  As described above, by subdividing the mesh close to the calculation point 400 (that is, dividing the cells in the mesh), the error in the calculation of the radiation dose at the calculation point 400 can be minimized. That is, the radiation source in the mesh (cell) close to the calculation point 400 has a large influence on the calculation of the radiation dose, and if the mesh (cell) close to the calculation point 400 is rough, the distance from the point source to the calculation point of each layer, etc. It will change, and the error in calculating the radiation dose will increase. However, by subdividing the mesh close to the calculation point 400, such an error can be reduced.

  Next, the dose calculation processing unit 16 calculates the radiation dose at the calculation point 400 from the point source set in layers in each cell constituting the three-dimensional shape model based on the point attenuation kernel calculation method (step S15). . Specifically, in the layered volume source model shown in FIG. 5, the dose calculation processing unit 16 uses the following equation (1) for each cell based on the point attenuation kernel calculation method, and the radiation dose at the calculation point 400. Calculate (radiation intensity).

Here, I _i indicates the radiation dose (photon flux [photons / m ² s] or relative value) from the cell i. R _efrdens indicates a conversion coefficient (arbitrary). S _i represents the radioactivity intensity of cell i (arbitrary numerical value of 0.0 to 1.0: color setting of a three-dimensional shape model). As _i indicates the area [m ² ] of the cell i. F _n represents the constituent ratio of the photon energy n emitted from the radionuclide. BA _{i, n} represents the build-up coefficient of the main medium of photon energy n emitted from the radionuclide of cell i. For example, air is the main medium. BS _{i, n, j} represents the build-up coefficient of the volume source of photon energy n emitted from the radionuclide of the j-th layer of cell i. Sorily _{i, j} indicates the radioactive volume density (relative value or [Bq / m ³ ]) in the j-th layer of cell i. Th _layer indicates the thickness [m] of one layer.

.mu.a _n denotes the linear attenuation coefficient in the main medium of photon energy n emitted from a radionuclide. μν _n represents a linear attenuation coefficient in the volume source. DIS _i indicates the distance between the center of cell i and the calculation point. plenly _{i, j} indicates the distance (line attenuation distance) that the radiation from the j-th layer of the cell i crosses through the volume radiation source. pdisly _{i, j} indicates the distance between the j-th layer of cell i and the calculation point. The subscript i is an index representing a cell, n is an index representing photon energy emitted from the radionuclide, and j is an index representing a layer.

  In general, a plurality of photons (gamma rays or the like) having different energies are emitted from the radionuclide. Since the attenuation of these photons varies depending on the energy, the attenuation coefficient μan is defined for each photon beam (gamma ray or the like) with different energy emitted from the nuclide.

  The dose calculation processing unit 16 obtains the sum of the radiation doses at the calculation points 400 by adding the radiation doses of all the cells Seli constituting the three-dimensional shape model. In addition, if the radiation-related data specifies the composition ratio of various types of radiation (for example, what percentage is specified for cesium 137, what percentage for cesium 134, what percentage for other nuclides, etc.) The calculation processing unit 16 obtains the sum of the radiation doses at the calculation points 400 for each type of radiation, and adds these values.

  Next, the dose calculation processing unit 16 determines whether or not the radiation dose has been calculated at all the calculation points designated by the calculation point coordinates of the setting information 120 (step S16). When it is determined that the dose calculation processing unit 16 has not calculated the radiation dose at all the calculation points (NO in step S16), the information setting unit 14 executes mesh initialization (step S17). That is, the information setting unit 14 returns the mesh to a state where it is not subdivided (the state shown in FIG. 3). And the process of step S13-S17 is repeatedly performed. When it is determined that the radiation dose at all calculation points has been calculated (YES in step S16), the dose calculation processing unit 16 outputs a calculation result (calculation result 130, detailed calculation result 140) (step S18).

  Thereafter, the CG processing unit 13 determines the dose distribution and decontamination before the decontamination in the three-dimensional shape model based on the information such as the dose distribution before and after the decontamination and the dose reduction ratio in the evaluation target area included in the calculation result 130. An image representing the subsequent dose distribution and the dose reduction ratio before and after decontamination is generated. The display control unit 11 outputs and displays the image generated by the CG processing unit 13 on the display device 2. Thereby, the operator can visually recognize a change in dose distribution before and after decontamination. Further, the display control unit 11 outputs the detailed calculation result 140 output from the dose calculation processing unit 16 to the display device 2 for display. Thereby, the operator can confirm the detailed calculation result by text data.

  As described above, in the first embodiment, the CG processing unit 13 that sets radiation source information indicating the intensity of the radiation source on the shape surface of the three-dimensional shape model, and the shape surface of the three-dimensional shape model are meshed. A first information setting unit 14 that sets a plurality of meshes by partitioning, sets a plurality of cells in each mesh, and sets a radiation source having a radiation intensity corresponding to the radiation source information in each cell, and a calculation point at a predetermined position And a dose calculation processing unit 16 for calculating a radiation dose at a calculation point from the radiation source set in each cell. According to such a configuration, the three-dimensional shape model to be evaluated can be simulated as faithfully as possible, and the calculation result (prediction) is not required even if the radiation source is distributed over a wide range. Result).

  In the first embodiment, since the subdivision processing unit 15 that subdivides the mesh by dividing a cell that is close to the calculation point is provided, an error in the calculation of the radiation dose at the calculation point can be reduced. In the first embodiment, the subdivision processing unit 15 includes a line connecting the center of the equivalent circle equal to the cell area and the calculation point, and a line connecting a predetermined position on the circumference of the equivalent circle and the calculation point. The cell is divided when the angle formed by is greater than a certain angle. According to such a configuration, it is possible to improve the accuracy of determining whether to subdivide the mesh (divide cells) or not, and to further reduce the error in calculating the radiation dose.

  In the first embodiment, the first information setting unit 14 sets a point source in a layered manner in the depth direction of each cell for each cell. According to such a configuration, a model of an actual radiation source in a contaminated environment where the radiation source exists not only on the surface of the ground but also in the soil can be simulated with high accuracy. As a result, the accuracy of the radiation dose calculation result (prediction result) can be improved.

  In the first embodiment, the first information setting unit 14 sets the intensity distribution in the depth direction of the dotted line source of each layer for each cell, and thus a model of an actual radiation source in a contaminated environment. Can be simulated with higher accuracy, and the accuracy of the calculation result (prediction result) of the radiation dose can be further improved.

  In the first embodiment, the CG processing unit 13 creates a three-dimensional shape model based on topographic data, altitude data, and shape data such as a building. Therefore, the three-dimensional shape of an arbitrary shape such as a natural topography or a structure is obtained. A shape model can be created. In the first embodiment, since the CG processing unit 13 sets the radiation source information with color information on the shape surface of the three-dimensional shape model, the three-dimensional shape model can be created as data in the CG common format, Usability for workers is improved. In the first embodiment, the CG processing unit 13 sets the radiation source information on the shape surface of the three-dimensional shape model based on the radiation source intensity distribution before and after the decontamination, and the decontamination calculated by the dose calculation processing unit. Generate images of radiation dose distribution before and after. According to such a configuration, the operator can visually confirm the decontamination effect.

  In the first embodiment, the dose calculation processing unit 16 calculates the radiation dose at the calculation point from the radiation source set in each cell based on the point attenuation kernel calculation method. Evaluation result) can be obtained.

Second Embodiment
In the first embodiment described above, radiation attenuation due to an object existing between the calculation point and each cell is not considered. On the other hand, in the second embodiment, the radiation dose is calculated in consideration of the radiation attenuation by the object existing between the calculation point and each cell.

  FIG. 10 is a block diagram illustrating an example of a dose prediction apparatus 1A according to the second embodiment. Unlike the calculation processing unit 10 of the dose prediction apparatus 1 illustrated in FIG. 2, the calculation processing unit 10A of the dose prediction apparatus 1A illustrated in FIG. 10 includes a line-of-sight determination unit 17 and a shielding calculation processing unit 18. The line-of-sight determination unit 17 is a processing unit that determines whether an object exists between a calculation point and each cell. The occlusion calculation processing unit 18 is a processing unit that calculates the attenuation of radiation from the radiation source of each cell by the object when the line-of-sight determination unit 17 determines that an object exists between the calculation point and each cell. The dose calculation processing unit 16 calculates the radiation dose at the calculation point in consideration of the radiation attenuation calculated by the shielding calculation processing unit 18.

  FIG. 11 is a diagram illustrating a three-dimensional shape model for explaining the line-of-sight determination process. It is assumed that a radiation transmittance (radiation transmission coefficient, shielding coefficient) is set by the CG processing unit 13 on the shape surface of the three-dimensional shape model 500 shown in FIG. That is, the distribution information of the radiation transmittance is included in the information 100 to be calculated. The CG processing unit 13 sets the radiation transmittance for each polygon mesh constituting the shape surface of the three-dimensional shape model 500 based on the distribution information of the radiation transmittance. For example, the CG processing unit 13 sets the radiation transmittance in a three-dimensional shape model different from the three-dimensional shape model in which the radiation source information is set. In this case, two three-dimensional shape models are created.

  As shown in FIG. 11, a three-dimensional shape model 500 is provided with a building (structure) 510. In the three-dimensional shape model 500, the calculation point 400 is set near the building 510. When the building 510 is viewed from the calculation point 400, the region 500a is hidden behind the building 510. An object (building 510) exists between the mesh (cell in the mesh) in the region 500a and the calculation point 400.

  For example, in the process of step S15 in FIG. 8, the line-of-sight determination unit 17 determines the position of the calculation point 400 (three-dimensional coordinates) and the position of each mesh (or cell in each mesh) (for example, the three-dimensional coordinates of the center position) It is determined whether or not the building 510 exists between the two. Then, the dose calculation processing unit 16 calculates the radiation dose from the radiation source of each cell. Next, when the line-of-sight determination unit 17 determines that the building 510 exists between the position of the calculation point 400 and the position of each mesh, the shielding calculation processing unit 18 uses the radiation source of the cells in each mesh by the building 510. Calculate the attenuation of radiation from.

  Specifically, the shielding calculation processing unit 18 recognizes the radiation transmittance of the building 510 based on the radiation transmittance set on the shape surface of the three-dimensional shape model 500 by the CG processing unit 13. Further, the shielding calculation processing unit 18 calculates the distance that the radiation from the radiation source of the cell passes through the building 510. Then, the shielding calculation processing unit 18 calculates how much radiation is attenuated by the building 510 (how much radiation is transmitted) based on the radiation transmittance of the building 510 and the distance that the radiation passes through the building 510. The shielding calculation processing unit 18 corrects the radiation dose at the calculation point 400 based on the calculation result.

  As described above, in the second embodiment, the line-of-sight determination unit 17 that determines whether or not the object 510 exists between the calculation point 400 and each cell, and the line-of-sight determination unit 17 calculates the calculation point 400 and each of the points. When it is determined that the object 510 exists between the cells, the shielding calculation processing unit 18 calculates attenuation of radiation from the radiation source of each cell by the object 510, and the dose calculation processing unit 16 includes the shielding calculation processing. The radiation dose at the calculation point is calculated in consideration of the radiation attenuation calculated by the unit 18. According to such a configuration, a more accurate calculation result (prediction result) can be obtained.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various modifications or improvements can be added to the above embodiment without departing from the spirit of the present invention. In addition, one or more of the requirements described in the above embodiments may be omitted. Such modifications, improvements, and omitted forms are also included in the technical scope of the present invention. In addition, the above-described embodiments can be applied in appropriate combination.

  For example, the intensity distribution of the dotted line source of each layer in the radiation source model is not limited to the uniform distribution or the linear decrease (ramp shape) distribution as shown in FIG. FIG. 12 is a diagram showing a modification of the intensity distribution of the radiation source. FIG. 12 (1) shows a distribution in which the intensity distribution of the point source of each layer in the radiation source model changes on a straight line, and FIG. 12 (2) shows the intensity distribution of the point source of each layer in the radiation source model on an exponential function. It is a distribution that decays. After the information setting unit 14 sets the intensity distribution of the radiation source as shown in FIG. 12, the dose calculation processing unit 16 may calculate the radiation intensity at the calculation point.

  Further, the information setting unit 14 may set a radiation source only in a predetermined layer in the radiation source model, and set the intensity distribution of the radiation source. Further, the approximate calculation method is not limited to that shown in the above equation (1), and for example, an equation obtained by simplifying the above equation (1) may be used. Further, the calculation method is not limited to the point attenuation kernel calculation method, and other calculation methods may be used. In this case, information indicating what calculation method is used in the calculation control information may be specified.

  Further, the cell dividing method is not limited to the method shown in FIG. 6, and other methods may be used. For example, a method may be used in which the cell is divided when the distance between the calculation point 400 and the center (center of gravity) of the cell is within a certain distance.

  Further, as shown in FIG. 1, the three-dimensional CG program 200 and the dose prediction program 210 are configured by different programs, but the processing of the three-dimensional CG program 200 and the processing of the dose prediction program 210 are performed by one control program. The structure to perform may be sufficient.

  Moreover, in each above-mentioned embodiment, it assumed that the dose prediction apparatus 1 was implement | achieved by one computer. However, the dose prediction apparatus 1 may be composed of a plurality of computers. For example, a first computer equipped with the three-dimensional CG program 200 creates a three-dimensional shape model and sets radiation source information in the three-dimensional shape model. The first computer transmits the three-dimensional shape model set with the radiation source information and the like created using the three-dimensional CG program 200 and the setting information to the second computer (for example, a server) via the network. The second computer includes a dose prediction program 210 and calculates the radiation dose using the dose prediction program 210. Then, the second computer transmits the calculation result to the first computer via the network.

DESCRIPTION OF SYMBOLS 1 Dose prediction apparatus 2 Display apparatus 10 Computation processing part 11 Display control part 12 Data input part 13 CG process part 14 Information setting part (1st information setting part, 2nd information setting part)
DESCRIPTION OF SYMBOLS 15 Subdivision processing part 16 Dose calculation processing part 17 Line-of-sight determination part 18 Occlusion calculation processing part 100 Information of calculation object 110 Analysis information 120 Setting information 130 Calculation result 140 Detailed calculation result 200 Three-dimensional CG program 210 Dose prediction program 300,500 3 Dimensional shape model 400 Calculation points M Mesh Sel cell

Claims (13)

A CG processing unit that sets radiation source information indicating the intensity of the radiation source on the shape surface of the three-dimensional shape model;
A plurality of meshes are set by dividing the shape surface of the three-dimensional shape model into meshes, a plurality of cells are set for each mesh, and a radiation source having a radiation intensity corresponding to the radiation source information is set for each cell. A first information setting unit;
A second information setting unit for setting a calculation point at a predetermined position;
A dose prediction apparatus comprising: a dose calculation processing unit that calculates a radiation dose at the calculation point from the radiation source set in each cell.   The dose prediction apparatus according to claim 1, further comprising a subdivision processing unit that subdivides the mesh by dividing a cell having a short distance from the calculation point.   The subdivision processing unit has a constant angle formed by a line connecting the center of the equivalent circle equal to the cell area and the calculation point and a line connecting a predetermined position on the circumference of the equivalent circle and the calculation point. The dose prediction apparatus according to claim 2, wherein the cell is divided when the angle is equal to or greater than an angle.   The dose prediction apparatus according to any one of claims 1 to 3, wherein the first information setting unit sets a point source in a layered manner in the depth direction of each cell for each cell.   The dose prediction apparatus according to claim 4, wherein the first information setting unit sets an intensity distribution in a depth direction of a point source of each layer for each cell. The dose prediction apparatus according to any one of claims 1 to 5, wherein the CG processing unit creates the three-dimensional shape model based on terrain data, altitude data, and shape data of a structure .   The dose prediction apparatus according to any one of claims 1 to 6, wherein the CG processing unit sets radiation source information with color information on a shape surface of the three-dimensional shape model.   The CG processing unit sets the radiation source information on the shape surface of the three-dimensional shape model based on the radiation source intensity distribution before and after the decontamination, and the radiation dose distribution before and after the decontamination calculated by the dose calculation processing unit. The dose prediction apparatus of any one of Claim 1 to 7 which produces | generates the image of.   9. The dose calculation processing unit according to claim 1, wherein the dose calculation processing unit calculates a radiation dose at the calculation point from the radiation source set in each cell based on a point attenuation kernel calculation method. 10. Dose prediction device. A line-of-sight determination unit that determines whether an object exists between the calculation point and each cell;
A shielding calculation processing unit that calculates attenuation of radiation from the radiation source of each cell by the object when the line-of-sight determination unit determines that the object is present between the calculation point and each cell;
The dose prediction unit according to any one of claims 1 to 9, wherein the dose calculation processing unit calculates a radiation dose at the calculation point in consideration of attenuation of the radiation calculated by the shielding calculation processing unit. apparatus. The CG processing unit sets a radiation transmittance on the shape surface of the three-dimensional shape model,
The dose prediction apparatus according to claim 10, wherein the shielding calculation processing unit calculates attenuation of radiation from a radiation source of each cell by the object based on the radiation transmittance and the thickness of the object. Setting radiation source information indicating the intensity of the radiation source on the shape surface of the three-dimensional shape model;
A plurality of meshes are set by dividing the shape surface of the three-dimensional shape model into meshes, a plurality of cells are set for each mesh, and a radiation source having a radiation intensity corresponding to the radiation source information is set for each cell. And
Setting a calculation point at a predetermined position;
Calculating a radiation dose at the calculation point from the radiation source set in each cell. On the computer,
CG processing for setting radiation source information indicating the intensity of the radiation source on the shape surface of the 3D shape model;
A plurality of meshes are set by dividing the shape surface of the three-dimensional shape model into meshes, a plurality of cells are set for each mesh, and a radiation source having a radiation intensity corresponding to the radiation source information is set for each cell. A first information setting process;
A second information setting process for setting a calculation point at a predetermined position;
A dose prediction program for executing a dose calculation process for calculating a radiation dose at the calculation point from the radiation source set in each cell.

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