JP2013113594A - Apparatus and method for evaluating spatial dose - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve calculation speed of evaluation and accuracy of results by automating input of measurement results and input of an evaluation area map.SOLUTION: An apparatus for evaluating spatial doses in a wide area includes: area setting means for dividing a monitoring area of a wide range into a plurality of places like a grid and setting evaluation areas; measurement means for inputting doses measured or estimated in the plurality of places divided like the grid; a processor for calculating doses of evaluation points of the plurality of places arranged like the grid by using information obtained from the area setting means and the measurement means; and an output device for outputting calculated results of the processor. The processor finds out environmental radiation doses on grid-like evaluation points of the plurality of places arranged like the grid from a radiation source to which doses of the plurality of places arranged like the grid are inputted by using an approximate expression indicating correlation between distances and doses, and finds out a sum of environmental radiation doses found in each of the plurality of divided grid-like evaluation points. The output device displays the environmental radiation doses of each evaluation area as a spatial dose map.

Description

  The present invention relates to an air dose evaluation apparatus and method for displaying radiation doses contributed from soil, buildings, forests, and other various structures contaminated with radioactive substances.

  As a technique for creating a dose map and grasping the contamination status from the viewpoint of reducing the exposure of workers in a limited area such as within a management area of a nuclear power plant, for example, a radiation dose map creating apparatus of Patent Document 1 is known. .

  The radiation dose map creation device disclosed in Patent Document 1 includes an evaluation position input device that inputs a position of a space in which a dose should be evaluated, and a structure such as a radioactive structure and a non-radioactive shield in the work space. A storage device that stores the arrangement data of the above, a mesh generation device that virtually divides a structure having radioactivity into small regions of arbitrary size, and a radiation source of the divided small regions gives to arbitrary spatial positions It is composed of a response matrix generation device that determines the influence of radiation, and a calculation device that determines the dose.

  This device is an evaluation device that mainly focuses on dose prediction in an unmeasured range when measurement results are not sufficiently obtained, and outputs the dose at the time of measurement as a two-dimensional map.

  A series of calculation methods of a typical dose evaluation apparatus in the prior art will be described with reference to FIGS. In an example of the evaluation method according to the prior art, first, an evaluation area Z having a total of 25 squares composed of 5 × 5 mesh as shown in FIG. 5 is assumed. Here, 25 squares are defined by Z1 to Z25 shown in the figure.

In the case of evaluating the radiation dose in the evaluation area Z of 25 squares by the conventional technique, first, as shown in FIG. 6, the unit contamination density (here, 1 Bq / cm ² ) is in the center Zc (Z13). The dose rate at each of the grid-like evaluation points of a total of 25 squares is calculated using a shielding calculation code that is open to the public, and a response matrix is created. In the response matrix of FIG. 6, the dose rate at the center position Zc (Z13) of the lattice evaluation point of 25 squares is 10, and the farther from this, the smaller the value (4 for left and right up and down, 3 for diagonal up and down, etc.). An example is shown.

Next, if the actual contamination density at the center position Zc (Z13) is 10 Bq / cm ^{2 as} a result of measurement, the response matrix is multiplied by 10 and the dose rate of 25 masses around the source is shown in FIG. 7 is calculated.

Next, if the actual contamination density in the lower right corner Z0 (Z5) of this area is ² Bq / cm ² , the response matrix is multiplied by 2 and the dose rate of 25 masses around this source is shown in FIG. Calculated as the value shown.

Next, if the actual contamination density of 23 squares other than the above two squares (Zc, Z0) is all zero, the radiation dose from those squares is zero. As a result, the contamination status of this evaluation area Z is as shown in FIG. 9, and this is input. Figure 9 is a Zc of the center of the evaluation area Z, measures the pollution density of each Z0 lower right ^{10Bq / cm 2, 2Bq / cm} 2, and in the other mass indicates that contamination density are all 0 ing.

  Next, the evaluation result of this area is obtained by superimposing the result of FIG. 7 and the result of FIG. 8 as the dose from 25 cells. However, the results other than the 9 cells in the upper left of the results in FIG. 8 are not used because they are outside the evaluation range. In FIG. 10, an area ZA of 25 squares centered on the evaluation area ZC is the result of FIG. 7, and an area ZB of 25 squares centered on the evaluation area Z0 is the result of FIG. The superposition in the figure is obtained as the sum of these two values because the contamination density of the other cells is all zero. Therefore, if there is a contamination density in other masses, multiple superpositions including that amount are performed.

  Finally, the calculation results in this evaluation range are as shown in FIG. By displaying this result as a contour map, it is also possible to display the radiation dose distribution in this evaluation range.

JP-A-6-186340

  According to the conventional dose evaluation apparatus described above, there is an advantage that the calculation process is very fast because the calculation is simple.

  However, when there is a shielding object or the like that affects the result of the response matrix in the evaluation area, it is necessary to prepare a separate response matrix that takes into account the effects of the presence of the shielding object. For this reason, there is a problem that it is necessary to provide an enormous amount of database in order to enable calculation when an optional shielding is installed. The response matrix is a discrete result prepared in two dimensions, and is determined like a grid-like evaluation point such as a three-dimensionally arranged radiation source, evaluation points, and evaluation points other than the lattice-like evaluation points. Another problem is that when a distance other than the calculated distance is calculated, the corresponding calculation cannot be performed.

  In addition, in the conventional technology, it was a general idea to add the dose from a grid-like source to a focused evaluation point and output it as an evaluation result. There was no idea to map each dose calculation result from the source as it was. Since there is no contribution map that visually shows the dose contribution, and a dose contribution map for determining the decontamination range could not be created, it is sufficient from the viewpoint of efficient decontamination. Another problem is that information was not available.

  In view of the above, an object of the present invention is to provide an air dose evaluation apparatus and method that enables three-dimensional display by a simple method and that can also cope with various influence factors.

  The purpose of the embodiment of the present application will be described in more detail as follows. First, the first purpose is to enable three-dimensional calculations and to easily evaluate the effects of shielding materials, etc., and to improve the generalization of the evaluation system and the evaluation accuracy. is there.

  The second purpose is the introduction of a shielding modeling method that prevents underestimation while shortening the calculation time when inputting the shielding, and the type of shielding (size, material, structure, position, etc.) that was required in the past. ), The number of response matrix databases required for the number of combinations, and the calculation accuracy can be improved.

  Third, when calculating the contribution from each source to the evaluation point focused on in creating the dose map, the calculation results from all sources at the evaluation point, which was only an intermediate result of the calculation process in the past, were added. Use the previous value as input for map creation as it is, and use it as a map showing the area where the dose contribution ratio at the evaluation point is large, thereby displaying the effective decontamination range in the evaluation target area and contributing to decontamination planning. It is.

  The fourth object is to improve the speed of evaluation calculation and improve the accuracy of the results by automating the input of measurement results and the evaluation area map.

  From the above, in the present invention, an area setting means for setting an evaluation area by dividing a wide monitoring area into a plurality of locations in a grid pattern, and a measurement for inputting doses measured or estimated at a plurality of grid grid locations. Means, a processing device that calculates doses of evaluation points at a plurality of locations arranged in a grid using information obtained from the area setting means and the measuring means, and an output device that outputs the calculation results of the processing device In the wide-area spatial dose evaluation system, the processing unit calculates the environmental radiation dose at the multiple grid-shaped evaluation points arranged in a grid from the radiation source that received multiple doses arranged in the grid, and the distance and dose. Using the approximate expression that shows the correlation between the two, the sum of the environmental radiation dose is obtained for each of the plurality of divided grid evaluation points, and the output device displays the environmental radiation dose for each evaluation area as an air dose map

  In addition, when there is a shield on the path from the grid source to the grid evaluation point and the path passes through two of the planes perpendicular to the ground surface of the shield, the shield is used to calculate the environmental radiation dose. Take into account the existence of

  Further, the scattering component when the shielding object is taken into account is added to the evaluation result using the approximate expression showing the correlation between the distance and the dose.

  In addition, the digital value of the calculation result is displayed as it is as a map without adding the calculation results at the target evaluation point from any source.

  The measuring means is a measuring instrument having position information, and obtains a measurement result together with the position information.

  The area setting means has a function of converting the map information into an evaluation area and creating an input format.

  From the above, in the present invention, a wide range of monitoring areas are divided into a plurality of locations in a grid pattern, and doses measured or estimated at a plurality of locations divided into a grid pattern are obtained. The ambient radiation dose at multiple grid-like evaluation points arranged in a grid from the input source is obtained using an approximate expression that shows the correlation between distance and dose, and multiple grid-like evaluation points divided The sum of the environmental radiation dose is obtained for each, and the environmental radiation dose for each evaluation area is obtained as an air dose map.

  In addition, when there is a shield on the path from the grid source to the grid evaluation point and the path passes through two of the planes perpendicular to the ground surface of the shield, the shield is used to calculate the environmental radiation dose. Take into account the existence of

  ADVANTAGE OF THE INVENTION According to this invention, the air dose evaluation apparatus and method which can perform a three-dimensional display with a simple method and can respond also to various influence factors can be provided.

The figure which described the structure of the wide area | region air dose evaluation apparatus of this invention with the processing function. The figure which shows the structure of the wide area | region dose evaluation apparatus of this invention. The figure which described the external data used for execution of each function of FIG. 1, or the setting from the outside. The figure for demonstrating the determination method of whether to consider a shield. The figure which shows the evaluation area of a total of 25 squares comprised by 5x5 mesh. The figure which shows the example of the dose rate in the grid | lattice-like evaluation point in case the unit contamination density was centered in the evaluation area of FIG. The figure which shows the dose calculation result in the lattice-like evaluation point when the actual contamination density at the center is 10 Bq / cm ² using the response matrix of FIG. 6 in the evaluation area of FIG. The figure which shows the dose calculation result in the grid | lattice-like evaluation point when the contamination density of the lower right corner of an evaluation area is ² Bq / cm < ² > using the response matrix of FIG. The figure which shows the contamination condition (input value) of an evaluation area. The figure which shows the image which overlapped the calculation result of FIG. 7, and the calculation result of FIG. The figure which shows the dose evaluation result of the grid | lattice-like evaluation area of 5 * 5 mesh finally output by adding the calculation result of FIG. 7 and the calculation result of FIG. The figure which shows the correlation of the distance shown by an approximate expression, and a dose. The figure which shows the model in the case of calculating a lattice-like evaluation point from the source point Z1 by an approximate expression. The figure which shows the model in the case of implementing calculation of a grid | lattice-like evaluation point from the source point Z2 by an approximate expression. The figure which shows the cross-sectional model of an evaluation area with the topography with an unevenness | corrugation in an evaluation area. The figure which shows an input state when there exists a shield in an evaluation area. The figure which shows the calculation model in case an obstruction exists in an evaluation area. The figure which shows the calculation model only of a scattered radiation when there exists a shielding object in an evaluation area. The figure which shows a dose contribution digital value at the time of paying attention to the evaluation score of the center of an evaluation area. The figure which shows the model in the case of calculating a dose contribution digital value by an approximate expression. The figure shown about the determination method of the conversion factor when a dose measurement height is 1 m. The figure which shows the grid | lattice-like radiation source input position which has the east longitude north latitude coordinate for automatic inputs. The figure which shows the contribution map by the calculation of the 700 * 700m mesh actually produced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  Even when an example of the evaluation method according to the present invention is described, an evaluation area Z of 25 squares composed of the 5 × 5 mesh of FIG. 5 described above is assumed. The method for evaluating the radiation dose in the evaluation area Z by the technique of the present invention is as follows.

First, the relationship between the distance and the dose when a planar radiation source with a unit contamination density (here 1 Bq / cm ² ) is present is described as a relational expression. An example of the relational expression is the “Harima formula” shown in the formula (1), which is expressed by the following generalized exponential function. This equation (1) is a well-known equation that is often used to express the radiation distance and attenuation by the shielding object (air in the present invention).

  Here, A, B, C, D, and E are arbitrary coefficients. Of these equations, coefficients B, C, D, and E are within ± 20% of the results obtained using the Monte Carlo calculation code MCNP5, which calculates in detail the relationship between the distance from the surface source of unit contamination density and the dose rate. It is a coefficient that is adjusted appropriately to fit with. In the fitting, an optimal combination of four numbers for the coefficients B, C, D, and E is found, and the approximate expression has evaluation accuracy equivalent to that of the calculation code. Arbitrary coefficient A is a coefficient for increasing or decreasing the absolute value of the result, and t is a coefficient indicating the distance from the radiation source.

  Here, fitting is a method in which the analysis result of the Monte Carlo calculation code MCNP5 and the curve drawn by f (x) are described on the same graph, and the coefficient is changed by searching for a value close to the analysis result while sequentially changing the coefficient. Thus, the value of f (x) is determined in the order of coefficients that vary greatly.

  Note that if t = 0 is substituted, f (t) = 0, so that the value when the distance is 0 is the reciprocal of the result calculated by the calculation code at an arbitrary height from the unit source to the source center position. Use as is.

  FIG. 12 shows the correlation between the distance and the dose indicated by the approximate expression determined by such a method. In FIG. 12, cesium 134 and cesium 137 are displayed using a distance on the horizontal axis and an arbitrary direct line on the vertical axis. Of these, the straight line is the one obtained from the “Harima's formula” shown in equation (1), and the “●” is the unit contamination density distance from the surface source and the dose rate. The result calculated | required using the Monte Carlo calculation code MCNP5 which calculates a relationship in detail is shown. From this result, it can be understood that the “Harima formula” shown in the formula (1) is a very accurate approximation formula.

  In addition to the Harima formula, the “Tayama formula” shown below can also be applied to the approximate formula. If the distance and radiation dose can be accurately indicated, the approximate formula format is used in the present invention. Not specified.

  Next, in order to calculate the absolute value of the calculation result, a conversion factor from dose to contamination density is determined according to the measurement height of the dose measurement result used as input. The method for determining the conversion coefficient when the dose measurement height as shown in FIG. 21 is 1 m will be described below.

  The coefficient must be selected according to the contamination status of the evaluation area. For example, if it is assumed that the dose in the evaluation area is almost the same at any position and there is no place where the dose is locally high, for example, a unit contamination density source of 1 km square is assumed and a shielding calculation code is used. The reciprocal of the result of calculating the dose at the source center position 1 m is built in the apparatus as a conversion coefficient. As a result, the contamination density on the ground surface can be calculated by multiplying this coefficient by the measured dose at a height of 1 m. Since this conversion factor also takes into account the contribution of radiation from a distance, which is naturally included when measuring at a height of 1 m, it prevents the evaluation result from being overestimated.

  On the other hand, if it is assumed that the contamination status in the evaluation area is not uniform and many hot spots are found, for example, a unit contamination density source of 10 m square is assumed, and the source calculation center code 1m The reciprocal of the result of calculating the dose is built into the device as a conversion coefficient. This conversion factor is naturally included when measuring at a height of 1 m, and does not take into account the contribution of radiation from a distance, and is based on the premise that all radiation measured by a dosimeter is incident only within the range of 10 m square. Prevent underestimation of evaluation results even when there are hot spots in the vicinity. However, since the actual measurement results used at the input include radiation incident from a distance, overestimation occurs when used in an evaluation area where contamination is uniform.

  In this way, the conversion factor from the dose measurement value to the contamination density is information that greatly affects the accuracy of the overall calculation result, so that the user can easily adjust the evaluation result against the reality, A method capable of preventing deterioration of evaluation accuracy was adopted.

  Next, the lattice-like evaluation points are calculated from the source on the lattice. In the calculation, an approximation formula based on the Harima formula is used to calculate the number of radiation sources x the number of evaluation points. As an example, using the evaluation area Z of a total of 25 squares composed of 5 × 5 meshes in FIG. 5, the calculation is performed for 25 lattice evaluation points from one point of the Z1 radiation source at the lower left of the evaluation area Z.

  FIG. 13 shows a calculation model diagram in this case. In the square of the evaluation area Z in FIG. 13, “◯” at the position Z1 is a radiation source, “▲” at other positions is an evaluation point, and a line segment connecting the radiation source and the evaluation point means an evaluation distance t. Yes.

  Similarly, FIG. 14 shows a model in the case where a lattice-like evaluation point is calculated from the source point Z2. In the square of the evaluation area Z in FIG. 14, “◯” at the position Z2 is the source, “▲” at the other position is the evaluation point, and the line segment connecting the source and the evaluation point means the evaluation distance t. Yes.

  FIGS. 13 and 14 show that other evaluation points are estimated from the positions Z1 and Z2. Similarly, by changing the source position to a lattice shape and repeating this operation one after another, a total of 25 points are estimated. A total of 625 calculations are performed from the source of the location.

  In each calculation, a calculation result reflecting the degree of contamination can be obtained by arbitrarily multiplying the coefficient A of the equation (1) determined by the unit contamination density according to the contamination density at the radiation source position. In this way, by calculating the distance from the source point to the evaluation point using the Pythagorean theorem and then calculating the dose with an approximate expression, it is possible to obtain the result of the lattice evaluation point as in the prior art.

  Next, let us consider a case where the evaluation areas in FIG. Here, as shown in the cross-sectional model of FIG. 15, a cross section when the evaluation area Z in FIG. Assume a positional relationship between a radiation source and an evaluation point in such a downward-sloping terrain. At this time, as shown in the lower part of FIG. 15, the distance between the source “◯” and the evaluation point “▲” may be calculated as a distance farther than when viewed on a plane due to the difference in the height direction.

  In the case of such an inclined land, the calculation by the response matrix used in the prior art cannot be easily handled. As a solution, it is necessary to calculate the step by modeling it in two dimensions, or to add a large amount of response matrix according to the height to the apparatus. However, the former method is not implemented because the calculation accuracy is lowered, and the latter method is not a realistic method due to the problem of calculation time and cost.

  In this respect, the calculation using the approximate expression employed in the present invention can be easily handled because an accurate calculation result can be obtained simply by calculating the distance based on the difference in height.

  Next, it is assumed that there is a shielding object X to be considered in the evaluation area Z of FIG. FIG. 16 shows an input state when there is a shielding object in the evaluation area of FIG. In the example of this figure, the shielding object X exists in the part of Z18, Z19 among the squares from Z1 to Z25.

  In this case, FIG. 17 shows a calculation model diagram in the case where the calculation is performed for 25 lattice-like evaluation points from the lower left source Z1. According to this figure, it can be seen that the presence of the shielding object X affects the estimation of the cells Z19, Z24, and Z25. In particular, it can be confirmed that the evaluation results need to be reduced by shielding the lattice evaluation points a and b of the squares Z24 and Z25.

  In this regard, in the calculation using the approximate expression employed in the present invention, the attenuation rate is set in consideration of the material and thickness of the shielding object, and the above-mentioned “Harima's formula” and “Tayama's formula” are set to count A , B, C, D, E can be handled easily.

However, in this case, the calculation using the response matrix used in the prior art cannot be easily handled. It is necessary to calculate that there is no shielding, or to add a large amount of response matrix according to the position of any shielding object in the device. In the former case, the calculation accuracy is lowered, and in the latter case, it is not implemented because it is not a realistic one due to problems of calculation time and cost.
On the other hand, a new problem arises in the present invention by enabling the three-dimensional calculation and considering the effect of the shielding object. The first is a method for determining whether or not to consider a shielding object.

  For example, when calculating with the shielding calculation code QAD, the vertical and horizontal height dimensions of the shielding object are input, and the evaluation point is connected by a line from the radiation source to calculate the distance passing through the shielding object. However, there are disadvantages such as the fact that the input is enormous and it is not possible to set many radiation sources, and when the numerical value of the grid-like radiation source intensity is changed in a case study, it is necessary to change complicated inputs each time. For this reason, it is not suitable for evaluating the radiation dose contributed by soil, buildings, forests, and other various structures contaminated by radioactive materials released in a wide range in the general environment. In other words, when the same method as the shielding calculation code is implemented, the same problem occurs and it cannot be adopted.

  Therefore, it was necessary to take measures to handle the shielding easily and prevent underestimation. In the present invention, a method for determining when shielding is considered has been developed. As shown in the picture on the left side of Fig. 4, the straight line from a certain source "○" to a certain evaluation point "▲" passes through two of the surfaces perpendicular to the ground surface of the shield X. It is only a judgment method that considers shielding. In other words, when the straight line from the source “◯” to the evaluation point “▲” moves horizontally to the ground surface as shown in the left of FIG. 4, the shielding is considered, and the source “○” as shown in the right of FIG. If the straight line from the point to the evaluation point “▲” does not move horizontally on the ground, the shielding is not considered. When it is determined that the shielding effect is taken into consideration in the determination, the result is obtained by multiplying the evaluation result by the attenuation factor corresponding to the thickness and material of the shielding object inputted in advance.

  In the case of this determination, the ceiling surface of the shielding object is not considered, but when evaluating a wide range (for example, 1 km square), there is an evaluation point from a certain source “○” that passes through the ceiling surface of a 10 m building, for example. The straight line up to “▲” will not occur unless there are sharp terrain changes such as steep cliffs and valleys around it. It can be considered that there is almost no calculation having an evaluation point at a position where the elevation angle exceeds 45 ° as in the arrangement relation on the right side of FIG. Even if there is an exceptional positional relationship between the radiation source and the evaluation point, the result is excessive and a conservative result can be obtained. Therefore, there is almost no effect on the accumulated results, and there is no extreme overestimation.

  This invention is a concept that can be applied to a wide range of evaluation areas in the general environment, and even when the inside of the shield is hollow, it can be corrected with the input thickness. Is possible. In this way, underestimation can be prevented in three-dimensional calculations, and the shielding calculation code can be obtained by setting the minimum thickness, material, and position and size of the surface perpendicular to the ground surface as input conditions. This simplifies the complicated input required by the system and shortens the calculation time.

  The second new problem is the consideration of the dose due to the scattered radiation that appears when the evaluation result of the direct line attenuated by the shield becomes small. Also for this problem, an approximate expression of only scattered rays, which is fitted to a correlation diagram of distance and dose based on the calculation of only scattered rays excluding the direct line calculated by the Monte Carlo calculation code MCNP5, is built in the apparatus. As shown in Fig. 5, the problem was solved by adding the calculated value of only the scattered radiation obtained by the approximate expression only to the calculation result of the direct line of the evaluation point that was determined to consider shielding.

  Next, an example of a dose contribution map developed to implement more effective decontamination is shown.

  When calculating the conventional dose, if there are many sources, calculate the dose from each source to the evaluation point individually, and add the individual values to output the dose at the evaluation point. That was the general idea.

  That is, among the evaluation results shown in FIG. 10, the individual calculation results before summing shown in the lower right 9 cells are only one element constituting the output as shown in FIG. It was not treated as. That is, 100 + 2 100 and 2 described in the center Zc of the grid-like evaluation point in FIG. 10 are calculation processes for obtaining the dose 102 shown in FIG. 11 in the evaluation area Z when there is contamination as shown in FIG. It was supposed to be only a result on the way.

  In the present invention, when viewed from the evaluation point of the grid center Zc, a numerical value 100 + 2 is a contribution from the grid source center Zc, and a numerical value 2 is a dominant dose indicating the contribution dose from the grid source lower right Z0. Focusing on the information, it is shown as in FIG. 19 and is displayed as a dose contribution when focusing on the evaluation point (shaded portion) at the center Zc of the evaluation area.

  Furthermore, by showing the values as they are in the contour map, it is possible to visually indicate where the radiation source that contributes predominantly at the evaluation point, and by decontaminating which part, the dose can be reduced efficiently. It has become possible to judge instantly.

  The results in FIGS. 10 and 11 are the calculation results using the response matrix which is the prior art. However, as shown in FIG. It is. FIG. 20 is a model diagram in the case of calculating each from the grid-like radiation source when focusing on the lower left evaluation point Z1 (shaded portion), and the result is described in the position of the radiation source.

Conventionally, based on this result, the accumulated dose 52 at the lower left evaluation point Z1 is output.
Although it was (3 + 2 + 1 + 1 + 5 + 4 + 5 + 6 + 2 + 5 + 1 + 1 + 10 + 1 + 4 + 0 + 0 + 0 + 1 + 1 + 0 + 0 + 0 + 0 + 0), each value is not added up, but individual values are displayed at the source position. It can be confirmed that this is a method for efficiently reducing the dose. FIG. 23 shows a contribution map by calculation of a 700 × 700 m mesh actually created using this developed product.

  Next, an example of the measurement result automatic input function will be described. For this automatic input, for example, a dosimeter with a GPS function is used which can simultaneously record the position information and measurement results of east longitude and latitude and output the data in CSV format.

  In the air dose evaluation apparatus, numbers of east longitude and north latitude are respectively assigned to grid-like radiation source input positions as shown in FIG. Based on this east longitude north latitude information, the dose at the corresponding position is extracted from the CSV format data output from the dosimeter when the measurement result is imported to the evaluation device, and used as the dose input.

  At that time, it is difficult for the portable dosimeter to obtain an accurate grid-like measurement position value due to the problem of the accuracy of position information by GPS etc., so that there are two measurement results per grid, A state in which a grid with a blank measurement result exists.

  Therefore, in the former case, underestimation is prevented by discriminating the maximum measured value from a plurality of measurement results and using it as an input, and in the latter case, an interpolated value obtained by averaging the surrounding values is used. use. Here, when using the interpolated value, there is a concern about underestimation when there is a place where the dose is accidentally high on the grid from which the measurement value was not obtained. Extreme underestimation does not occur because higher doses are measured that affect the surrounding measurement results.

  Contributing from soil, buildings, forests, and various other structures contaminated by radioactive materials released into the general environment by incorporating a method for correcting such errors in dosimeters with position information into the product of the present invention It is now possible to automatically input the radiation dose measurement results to the air dose evaluation system.

  Next, an embodiment of the evaluation area automatic setting function is shown. When actually evaluating the radiation environment in the environment with the product of the present invention, it is necessary to set the grid-like radiation source and the grid-like evaluation position according to the actual topography.

  At that time, it is necessary to assume that the radiation source has an arbitrarily large square surface shape, but dropping a wide range of accurate positions into a lattice shape is a work accompanied by a decrease in accuracy. Therefore, the newly developed product has built-in map information, and it is now possible to automatically create a grid according to the grid source input format of the device by specifying the range.

  This makes it possible to accurately indicate the input position of the grid line source having the coordinates of the east longitude and north latitude shown in FIG. 22, clearly showing the actual measurement position and accurately grasping the size of the entire evaluation area. In addition, the evaluation point position can be set accurately.

  Next, the configuration of the wide-area air dose evaluation apparatus of the present invention is shown in FIG. The wide area air dose evaluation apparatus 100 of FIG. 2 includes a wide area air dose calculation apparatus 50 configured by a computer and a wide area air dose rate evaluation apparatus 60. The wide area air dose calculation device 50 obtains input from the measuring device 10 with a position information storage device and the map information storage device evaluation area automatic setting device 20. In addition, a decontamination plan, an expected effect evaluation 30 and an exposure reduction measure 40 are separately input.

  FIG. 1 divides the configuration of the wide-area air dose evaluation apparatus of the present invention shown in FIG. 2 into an input device portion I, a processing device portion OP, and an output device portion O, and shows functions to be provided in each portion. . In such a function expression, the input device portion I is first provided with an evaluation area automatic setting function I1 and a measurement result automatic input function I2.

  Further, in the processing unit OP, a process for calculating the contamination density on the surface of the contaminant based on the measurement result of the dose (processing step S10), and a calculation process for reflecting the coefficient indicating the decontamination effect on the result of calculating the contamination density ( Obtained by the processing step S11), the processing for calculating the air dose at the evaluation point from the radiation source for which the contamination density is set, mainly calculating the direct line (processing step S12), and the approximation formula A process of inputting the effect of the shielding object into the result and correcting and calculating the result (processing step S13), and an equation for approximating the scattered radiation (skyshine line) that becomes dominant when the direct line is attenuated by the shielding object Processing for calculating scattered radiation (processing step S14), processing for adding calculation results for grid-like evaluation points from a radiation source set in a grid shape (processing step S15), and a certain evaluation Executing the summing does not result obtaining processing of all calculated values (process step S16) at the point.

  Further, the output device portion O includes portions O1 and O2, in which the calculation result is a digital value, a portion O3 that is contoured and output as an air dose rate map, a portion O4 that is contoured and output as a dose contribution map, and the like.

  FIG. 3 is a diagram in which external data used for the execution of each function or settings from the outside are shown in the function diagram of FIG. First, the evaluation area automatic setting function I1 of the input device portion I is connected to the built-in Geographical Survey Institute map D1. The map information of the evaluation target area is mechanically read from D1, and a grid-like source input format and grid-like evaluation points are automatically created. The measurement result automatic input device I2 is connected to a dosimeter D2 having a function of recording position information such as GPS. Radiation measurement results and measurement position information are automatically read and input from here.

  Similarly, the following external data and settings from the outside are referred to for each processing in the processing apparatus.

  In the process of calculating the contamination density on the contaminant surface based on the measurement result of the dose (processing step S10), the dose and the contamination density conversion coefficient D3 are obtained before the execution. In the calculation process (processing step S11) in which the coefficient indicating the decontamination effect is reflected in the result of calculating the contamination density, the decontamination coefficient and decontamination range D4 are referred to.

  In the process of calculating the air dose at the evaluation point from the radiation source set with the contamination density and mainly calculating the direct line (processing step S12), the direct line approximation formula D5 and shielding information (range, material, thickness, etc.) D6 Is used. In the process (processing step S14) of calculating the scattered radiation (skyshine line) that becomes dominant when the direct line is attenuated by the shielding object, the scattered radiation approximate expression D6 is used.

  According to the present invention described above and the embodiments thereof, the following effects can be obtained.

  In the embodiment of the present invention, the method for performing dose calculation based on the evaluation matrix is changed to an evaluation method based on an approximate expression using, for example, the Harima formula. When determining the approximate expression, based on the calculation result using the Monte Carlo calculation code that performs detailed shielding calculation in three dimensions, the difference from the calculation result is within ± 20% by performing parameter fitting of the approximate expression. I was able to fit in. It is easy to consider the influence of shielding, and since continuous results are obtained, the evaluation point position can be arbitrarily changed, and three-dimensional calculation is possible. In addition, the effect of the shielding and the ability to perform three-dimensional calculations have enabled more reality-based calculations, resulting in improved evaluation accuracy compared to the prior art.

  In addition, we developed a judgment method when considering the shielding effect in the modeling method of the shielding problem, which is a problem in calculating the shielding effect using an approximate expression. In this judgment method, it is judged that shielding needs to be considered only when passing through two surfaces perpendicular to the ground surface, and it is not judged as shielding when passing through a surface parallel to the ground even once, thereby preventing underestimation. Is achieved.

  This method is an optimal method that can ensure calculation accuracy when there is no sudden elevation change in the evaluation area. It is possible to easily and easily prevent underestimation of the judgment method when considering the effect of shielding, which is a problem when calculation is performed from the grid source to the grid evaluation point using an approximate expression. As a result, improvement of evaluation accuracy and reduction of calculation time were achieved.

  In addition, when calculating the shielding effect using an approximate expression, a function was added to enable the calculation using an approximate expression for the contribution of scattered radiation that must be newly considered. The improvement of evaluation accuracy was achieved by making it possible to consider the contribution of scattered radiation that surfaced after the contribution of the direct line attenuated by the shield disappeared.

  In addition, the calculation results before summation at any focused evaluation point from a grid-like source, which has not been used as output information when creating a dose map in the past, are used as input for the map. The function to do was given. Visually confirm the most contributing radiation source in the range where the dose rate is to be reduced by decontamination, taking into account the intensity of the radiation source itself, the effect of distance, the effect of shielding, and the contribution of scattered radiation It has become possible to create a dose contribution map that can be used, and to obtain useful information in determining an effective decontamination range.

  In addition, the CSV format is adopted for the interface with the radiation measuring instrument having the GPS function, and a measurement error correction method for position information is developed. In the field of air dose evaluation, data is automatically transferred and converted into input values. Carried out. It is possible to input measurement values automatically, and it is possible to reduce the input work and the confirmation work of input values, and it is possible to eliminate the error potential due to human intervention. It has become possible to achieve both evaluation accuracy and calculation speed improvement.

  In addition, a grid-like input format is created automatically when an evaluation range is arbitrarily selected from the Geographical Survey Institute map information built into the device, eliminating the need for scale adjustment and range confirmation. Even when an arbitrary evaluation area is selected, it is possible to determine the source point and the evaluation point position easily and accurately, and it is possible to eliminate the error potential due to human intervention. It has become possible to achieve both ensuring accuracy and improving calculation speed.

  There is currently a need for a reasonably efficient decontamination method that takes into account economic factors. The present invention is an apparatus that makes it possible to quickly, easily and accurately indicate the range where decontamination is necessary and the degree of decontamination.

10: Measuring device with position information storage device 20: Map information storage device evaluation area automatic setting device 30: Decontamination plan and expected effect evaluation 30
40: Radiation dose reduction measure 50: Wide area air dose calculation device 60: Wide space air dose rate evaluation device 100: Wide space air dose evaluation device OI: Input device portion OP: Processing device portion O: Output device portion I1: Evaluation area automatic setting function I2 : Automatic measurement result input function

Claims (8)

An area setting means for setting an evaluation area by dividing a wide monitoring area into a plurality of places in a grid, a measurement means for inputting doses measured or estimated at a plurality of places divided in a grid, the area setting means, In a wide-area spatial dose evaluation apparatus including a processing apparatus that calculates doses at evaluation points at a plurality of locations arranged in a grid using information obtained from measurement means, and an output apparatus that outputs a calculation result of the processing apparatus ,
The processing apparatus is configured to calculate an environmental radiation dose at a plurality of grid-like evaluation points arranged in a grid from an input source of a plurality of doses arranged in a grid, and an approximate expression indicating a correlation between distance and dose Is used to find the sum of the environmental radiation dose for each of the divided grid-like evaluation points,
The output device displays an environmental radiation dose for each evaluation area as an air dose map, and is a wide-area air dose evaluation device. In the wide area | region air dose evaluation apparatus of Claim 1,
When there is a shield on the path from the grid source to the grid evaluation point, and the path passes through two of the planes perpendicular to the ground surface of the shield, it is necessary to calculate the environmental radiation dose. Wide-area air dose evaluation device characterized by presence. In the wide area air dose evaluation apparatus according to claim 2,
A wide-area air dose evaluation apparatus characterized in that a scattering component when a shielding object is taken into account is added to an evaluation result using the approximate expression indicating a correlation between distance and dose. In the wide area | region air dose evaluation apparatus in any one of Claims 1-3,
A wide-area air dose evaluation apparatus that displays the digital values of the calculation results as a map as they are without adding the calculation results at the target evaluation point from any source. In the wide area | region air dose evaluation apparatus in any one of Claims 1-4,
The said measurement means is a measuring device which has position information, and acquires a measurement result with position information, The wide area | region air dose evaluation apparatus characterized by the above-mentioned. In the wide area air dose evaluation apparatus in any one of Claims 1-5,
The area setting means has a function of converting map information into an evaluation area to create an input format, and a wide area air dose evaluation apparatus.   Divide a wide monitoring area into multiple locations in a grid, obtain measured or estimated doses at multiple locations divided into a grid, and form a grid from a radiation source that has been input at multiple locations in a grid The environmental radiation dose at multiple grid-like evaluation points arranged in the area is obtained using an approximate expression indicating the correlation between distance and dose, and the sum of the environmental radiation doses is obtained for each of the divided grid-like evaluation points. A wide-area air dose evaluation method characterized in that an environmental radiation dose for each evaluation area is obtained as an air dose map. In the wide area air dose evaluation method of Claim 7,
When there is a shield on the path from the grid source to the grid evaluation point, and the path passes through two of the planes perpendicular to the ground surface of the shield, it is necessary to calculate the environmental radiation dose. Wide-area air dose evaluation method characterized by presence.

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