JP6061792B2 - Contamination status estimation device and contamination status estimation method - Google Patents

Description

  The present invention relates to a contamination state estimation apparatus and a contamination state estimation method for estimating a contamination state due to a radioactive substance.

  Conventionally, the pollution status is measured in an area where environmental pollution is caused by a radioactive substance. For example, Patent Document 1 discloses that the radiation dose is measured by remote control.

Japanese Patent Laid-Open No. Sho 63-151884

  The measured contamination status is used for the examination of the decontamination method and the evaluation of the decontamination effect. The values indicating the contamination status to be measured include an air dose rate (a dose rate at a height of 1 m), a surface dose rate (a dose rate at a height of 1 cm), a surface contamination density, and the like. However, among these measurements, the surface dose rate has been applied to the identification of hot spots, but has not been sufficiently reflected in more specific decontamination plans.

  The present invention has been made in view of the above, and an object of the present invention is to provide a contamination state estimation apparatus and a contamination state estimation method that can provide information indicating a contamination state that contributes by studying a decontamination method.

  In order to achieve the above object, a contamination status estimation apparatus according to the present invention includes input means for inputting radiation dose values at a plurality of different heights at a predetermined position, and a plurality of different heights stored in advance. Based on the relationship between the values indicating the radiation dose, the estimation means for estimating the contamination status around the predetermined position from the value indicating the radiation dose input by the input means, and the contamination status estimated by the estimation means Output means for outputting information indicating the above.

  In the contamination status estimation apparatus according to the present invention, the contamination status is estimated from values indicating radiation doses at a plurality of different heights based on the relationship between these values. Therefore, it is possible to estimate the detailed contamination status as compared with the case where the value indicating the radiation dose at each height is considered individually, and to provide information indicating the contamination status that contributes to the examination of the decontamination method. .

  The estimation means may estimate the contamination state around the predetermined position based on a comparison between a ratio of values indicating the radiation dose at two different heights input by the input means and a preset threshold value. Good. According to this configuration, for example, a specific contamination state can be estimated as to whether or not the ground is uniformly contaminated.

The estimation means estimates an expression for estimating a value indicating the radiation dose according to the height based on at least one of the values indicating the radiation dose input by the input means, and indicates the radiation dose based on the expression based on a comparison of the value indicating the amount of radiation entered by the value input means, you estimate the contamination situation around a predetermined position. According to this configuration, it is possible to estimate a more detailed contamination state.

  The input means inputs values indicating radiation doses at a plurality of different heights at a plurality of predetermined positions in the horizontal direction, and the estimation means calculates radiation doses at the plurality of predetermined positions input by the input means. It is good also as estimating the position of a contamination source based on the value shown. According to this configuration, it is possible to estimate a more detailed contamination state in the horizontal direction.

  The contamination status estimation apparatus may further include a detection unit that detects a value indicating the radiation dose. According to this structure, the value which shows the radiation dose in several different height can be input, and a contamination condition can be estimated reliably.

  By the way, the present invention can be described as an invention of a pollution status estimation apparatus as described above, and can also be described as an invention of a pollution status estimation method as follows. This is substantially the same invention only in different categories, and has the same operations and effects.

That is, the contamination state estimation method according to the present invention is a contamination state estimation method by the contamination state estimation device, and includes an input step of inputting values indicating radiation doses at a plurality of different heights at a predetermined position; An estimation step for estimating a contamination situation around a predetermined position from the value indicating the radiation dose input in the input step based on the relationship between the stored values indicating the radiation dose at different heights; an output step for outputting information indicating the estimated contamination conditions in step, seen including a in the estimation step, the radiation amount corresponding to the height based on at least one of a value that indicates the amount of radiation that is input in the input step Based on a comparison between a value indicating the radiation dose based on the formula and a value indicating the radiation dose input in the input step. Estimates the pollution around the predetermined position.

  In the present invention, the contamination status is estimated from values indicating radiation doses at a plurality of different heights based on the relationship between these values. Therefore, it is possible to estimate the detailed contamination status as compared with the case where the value indicating the radiation dose at each height is considered individually, and to provide information indicating the contamination status that contributes to the examination of the decontamination method. .

It is a figure which shows the structure of the contamination condition estimation apparatus which concerns on embodiment of this invention. It is a figure which shows a virtual disk radiation source. It is a graph which shows the ratio of the dose rate of the height with respect to the dose rate of 1 cm in height when the radius r of the disk radiation source is 1 m, 100 m and 10 km, respectively. It is a figure which shows the relationship between a surface dose rate and an air dose rate. It is a figure which shows the measurement result of a surface dose rate and an air dose rate. It is a flowchart which shows the process (contamination status estimation method) performed with the contamination status estimation apparatus which concerns on 1st Embodiment of this invention. It is a graph of the dose rate according to the height for every width of the ground source. It is a graph of the dose rate according to the height when there is a radiation source other than the ground. It is the graph which showed the formula for estimating a dose rate notionally. It is an example of the graph which shows the predicted value and measured value of a dose rate when there exists a radiation source other than the ground. It is another example of the graph which shows the predicted value and measured value of a dose rate when there exists a radiation source other than the ground. It is a flowchart which shows the process (contamination status estimation method) performed with the contamination status estimation apparatus which concerns on 2nd Embodiment of this invention.

  Hereinafter, embodiments of a contamination state estimation apparatus and a contamination state estimation method according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

<First Embodiment>
FIG. 1 shows a contamination status estimation apparatus 1 according to the first embodiment of the present invention. The contamination status estimation device 1 is a device that estimates a contamination status due to a radioactive substance. The contamination status estimated by the contamination status estimation device 1 is used for examination of a decontamination method (decontamination plan). Therefore, the area where the contamination state is estimated by the contamination state estimation device 1 is an area having a wide range such as outdoors.

  As shown in FIG. 1, the contamination status estimation apparatus 1 according to the present embodiment includes a dose rate meter 10 and an information processing apparatus 20. The dose rate meter 10 is detection means for detecting a value indicating the radiation dose. The dose rate meter 10 is, for example, a device that detects a dose rate (μSv / h) of beta rays (β rays) and gamma rays (γ rays). Specifically, the dose rate meter 10 corresponds to a NaI scintillation type survey meter (NaI dose rate meter). Alternatively, the dose rate meter 10 may be a CsI scintillation type survey meter (CsI dose rate meter). Or it is good also as a GM survey meter (GM contamination test meter), and it is good also as using them together.

  In addition, since the penetrating power of beta rays is much weaker than the penetrating power of gamma rays, the difference in the degree of contamination is more likely to appear clearly in the numerical value in the GM pollution tester that detects beta rays. Therefore, it is suitable for searching for a highly contaminated place such as a hot spot or grasping a change in the state of contamination before and after decontamination. On the other hand, it is not suitable for examining the average degree of pollution in large spaces. The reason for this is that although the contamination of a large space seems to be uniformly contaminated at first glance, it actually results in spatial variation. For this reason, it can be said that it is difficult to measure the degree of contamination over a wide range using a GM contamination inspection meter that detects beta rays that transmit only a few meters in air.

  On the other hand, the NaI dose rate meter detects gamma rays with strong penetrating power and is therefore suitable for grasping the degree of contamination in a wide range. However, since the amount of radiation that passes through the detector increases as it approaches the contamination source, the numerical value changes depending on the distance from the contamination source. That is, when the surface of the measurement point is significantly contaminated, the measured value at 1 cm from the ground surface is different from the measured value at 1 m from the ground surface. On the other hand, when there is little contamination of the ground surface and the influence from the periphery is strong, there is no big difference in the measurement results at 1 cm and 1 m. For example, even when there are roofs of houses, trees, tall grass, etc., even if the measurement point is raised from 1 cm to 1 m, the distance to other pollution sources other than the ground surface does not change greatly, so it is 1 cm. There is a tendency that changes are not seen much at 1 m.

  For example, as for the degree of contamination of a metal surface in a nuclear power plant, since contaminants are attached only to the surface, a GM survey meter (GM contamination inspection meter) is suitable as described above. However, in the decontamination work, since soil is included in the object, it cannot be said that the GM survey meter is generally suitable for evaluating the degree of contamination. That is, it stays between about 1 cm to 2 cm of cesium (Cs) in the soil, and it can be said that the GM survey meter alone is insufficient to grasp the degree of contamination below the surface layer. Therefore, in the present embodiment, the surface dose rate using a NaI scintillation type survey meter that is easy to evaluate the degree of contamination in the soil may be used in combination.

  The dose rate meter 10 detects a value indicating a radiation dose at a plurality of preset different heights (positions in different vertical directions) at a predetermined position (position in the same horizontal direction). Specifically, the dose rate meter 10 measures (detects) a surface dose rate that is a dose rate at a height of 1 cm from the ground surface and an air dose rate that is a dose rate at a height of 1 m from the ground surface. . In addition, in the above, the same position should just be a position in the range which can be considered the same in estimation of a contamination condition. The positioning of the dose rate meter 10 at the time of measurement may be performed, for example, by a user (measurer) of the contamination state estimation apparatus 1. In addition, a rod-shaped member is prepared, and the dose rate meter 10 is fixed at a position 1 cm from the ground surface and a position 1 m from the ground surface when the rod-shaped member is pushed to the ground surface so that its axial direction is vertical. It is good to keep it. According to this configuration, it is possible to reliably measure the dose rate at heights of 1 cm and 1 m.

  The dose rate meter 10 and the information processing apparatus 20 are connected by wire or wirelessly and can transmit and receive information to and from each other. The dose rate meter 10 outputs a value indicating the measured radiation dose to the information processing apparatus 20.

  The information processing apparatus 20 is an apparatus that estimates a contamination state due to a radioactive substance by performing information processing based on information received from the dose rate meter 10. Specifically, the information processing device 20 corresponds to a device such as a workstation or a PC (Personal Computer), and is configured by hardware such as a CPU (Central Processing Unit) and a memory. The information processing apparatus 20 exhibits the functions described below when these components operate according to a program or the like. In the present embodiment, the information processing device 20 is realized by a single device, but may be realized by an information processing system configured by connecting a plurality of information processing devices to each other via a network.

ここで、Φ_Ｐは点Ｐにおけるγ線密度［γ／（ｃｍ^２・ｓ）］であり、Ｑ_Ａは円盤線源３０の強度［γ／（ｃｍ^２・ｓ）］である。また、θは、点Ｐから円盤線源３０への垂線と点Ｐから円盤線源３０の端点（円盤線源３０における中心から距離ｒの位置の点）までの線とがなす角である。 Here, the relationship of the dose rate used for estimation of the contamination situation in this embodiment will be described. Radiation has the property of decaying with distance. Therefore, the air dose rate generally shows a lower value than the surface dose rate near the contaminated site on the ground. As shown in FIG. 2, a virtual disk source 30 in which the surface is uniformly contaminated in a circular range having a radius r of the ground surface (radiation material is uniformly distributed) Think. When there is no shielding body, the dose rate at the point P of the height d at the center of the disk source 30 can be expressed by the following equation (1).

Here, Φ _P is the γ-ray density [γ / (cm ² · s)] at the point P, and Q _A is the intensity [γ / (cm ² · s)] of the disk source 30. Θ is an angle formed by a perpendicular line from the point P to the disc source 30 and a line from the point P to the end point of the disc source 30 (a point at a distance r from the center of the disc source 30).

  In the graph of FIG. 3, the height of the point P with respect to the dose rate (γ-ray density at the point P having a height of 1 cm) when the radius r of the disk source 30 is 1 m, 100 m, and 10 km, respectively. The ratio of the dose rate for each length d is shown. In the graph of FIG. 3, the horizontal axis indicates the height d, and the vertical axis indicates the ratio. As shown in the graph of FIG. 3, when the radius r of the disk source 30 is 100 m, the dose when the height d is 1 m with respect to the surface dose rate, which is the dose rate when the height d is 1 cm. The value of the air dose rate, which is the rate, is 50%.

  Therefore, when an area having a radius of about 100 m is considered as a reference, the following determination can be performed as a rough index at the position (original position) where the dose rate is measured. FIG. 4 shows the relationship between the surface dose rate (horizontal axis) and the air dose rate (vertical axis).

  That is, when the air dose rate × 2> surface dose rate (in FIG. 4, the relationship between the air dose rate × 2 = the upper left region from the surface dose rate straight line L1), there are surrounding contamination sources other than the ground. Pollution sources other than the ground are, for example, trees and buildings. When the air dose rate × 2 = surface dose rate (in the case of the relationship on the straight line L1 in FIG. 4), there is no contamination source other than the ground, and the ground is surface-contaminated. When the air dose rate × 2 <the surface dose rate (in the case of the relationship in the lower right region from the straight line L1 in FIG. 4), the contamination of the ground is limited (the source is the disc source 30) The radius r is smaller than 100).

  FIG. 5 shows the measurement results of the dose rate implemented by the applicants of the present application who confirmed the validity of the relationship (theoretical formula) between the air dose rate and the surface dose rate. This is the result of measuring surface dose rate and air dose rate (5,241 points) at preset measurement points (mesh points) in Katsurao Village, Tamura City and Tomioka Town in Fukushima Prefecture. Measurements were taken both before and after decontamination (pre- and post-monitoring).

FIG. 5 is a plot of the surface dose rate and the air dose rate measured at the same point, with the horizontal axis being the surface dose rate (μSv / h) and the vertical axis being the air dose rate (μSv / h). A solid line L2 in the figure indicates an approximate line y (air dose rate) = 0.6509x (surface dose rate). The broken line L3 in the figure shows the relationship of air dose rate × 2 = surface dose rate. In addition, the following statistical data on surface dose rate and air dose rate were obtained.

  From FIG. 5, although there is data that does not fit well on the approximate line, such as data with a high surface dose rate (value of 20 μSv / h or more), other data are roughly on the approximate line. The approximate straight line equation shows that a value of 65% of the surface dose rate becomes the air dose rate. The reason why the slope (65%) of the relationship between the actual measurement values is slightly larger than the calculated value (50%) is as shown in the above outline index (air dose rate × 2> surface dose rate case). In the decontamination target area, there are trees and buildings, and there is a high possibility that there are many influences from pollution sources other than the ground in a circular area having a radius of 100 m. In addition, as other factors satisfying the air dose rate × 2> surface dose rate, the height of measurement of the surface dose rate and the influence of skyshine can be considered. As for the height of measurement of the surface dose rate, when the NaI scintillation type survey meter is measured while floating from the ground, it may be a small value when measured higher than 1 cm. In addition, the values of both air dose rate and surface dose rate may have been raised due to the effect of skyshine.

  As described above, it is effective to consider “air dose rate × 2” as one judgment criterion as a judgment index in judging the contamination status at the original position. The present embodiment uses the above-described determination criteria.

  As shown in FIG. 1, the information processing apparatus 20 includes an input unit 21, an estimation unit 22, and an output unit 23.

  The input unit 21 is an input unit that inputs values indicating radiation doses at a plurality of different heights at a predetermined position (the same position). Specifically, the input unit 21 inputs a value indicating the radiation dose by receiving information transmitted from the dose rate meter 10. The values indicating the radiation dose to be input are, for example, two values: the surface dose rate, which is a dose rate 1 cm above the ground surface, and the air dose rate, which is a dose rate 1 m above the ground surface. The input unit 21 outputs a value indicating the input radiation dose to the estimation unit 22.

  Based on the relationship between the values indicating the radiation dose at a plurality of different heights stored in advance, the estimation unit 22 determines the contamination status around the predetermined position from the value indicating the radiation dose input by the input unit 21. It is an estimation means to estimate. The estimation unit 22 estimates the contamination state around the predetermined position based on a comparison between a ratio of values indicating the radiation dose at two different heights input by the input unit and a preset threshold value. For example, the estimation unit 22 calculates the surface dose rate / air dose rate value, and estimates the contamination status by comparing the calculated value with a threshold value. Specifically, the threshold is 2. When the calculated value exceeds the threshold (that is, when “air dose rate × 2 <surface dose rate” is satisfied), the contamination status is estimated to be within a limited range of soil contamination as described above. . When the calculated value falls below the threshold (that is, when “air dose rate × 2> surface dose rate” is satisfied), it is estimated that there is a contamination source other than the ground. In addition, two threshold values are provided (for example, threshold values 2 + α and 2-α (α is a preset value)), and when the calculated value is a value between those threshold values, other than the ground It may be estimated that there is no pollution source and the ground is contaminated.

  In the above estimation, the ratio value is calculated. However, it is not always necessary to calculate the ratio value, and it is sufficient that the ratio value is substantially taken into consideration. For example, it is possible to estimate the contamination state around a predetermined position by determining whether or not the relationship of “air dose rate × threshold> surface dose rate” is satisfied. In addition, about said threshold value and judgment criteria, it is preset and memorize | stored by the estimation part 22 as a relationship between the value which shows the radiation dose in several different height.

  Moreover, the estimation part 22 is good also as inputting information other than the value which shows the radiation dose input by the input part 21, and using it for estimation of a contamination condition. For example, information indicating whether or not there is a contamination target other than the ground around the position to be estimated may be used to estimate the contamination status. Contamination targets other than the ground are, for example, structures such as buildings and trees. The input of this information is performed, for example, by an operation on the information processing apparatus 20 by a user (measurer) of the contamination state estimation apparatus 1.

  When information indicating that there is no contamination target other than the ground around the estimation target position, it is not appropriate to estimate that there is a contamination source other than the ground. Therefore, in that case, when the “air dose rate × 2 <surface dose rate” is not satisfied, the estimation unit 22 estimates that there is no contamination source other than the ground and the ground is surface-contaminated. . On the other hand, when information indicating that there is a contamination target other than the ground around the position to be estimated, it is reasonable to estimate that there is a contamination source other than the ground depending on the value of the dose rate . Therefore, in that case, when the “air dose rate × 2 <surface dose rate” is not satisfied, the estimation unit 22 estimates that there is a contamination source other than the ground. In any case, when the “air dose rate × 2 <surface dose rate” is satisfied, the estimation unit 22 estimates that the contamination state is within a limited range of soil contamination. The estimation unit 22 outputs information indicating the estimation result to the output unit 23.

  The output unit 23 is an output unit that outputs information indicating the contamination status estimated by the estimation unit 22. The output by the output unit 23 may be, for example, a display output to a display device or the like so that a user (measurer) of the contamination status estimation device 1 can check the estimation result of the contamination status, or information to other devices. It is good also as outputting. The above is the configuration of the contamination state estimation apparatus 1 according to the present embodiment.

  Subsequently, processing and operations (contamination status estimation method) executed by the contamination status estimation apparatus 1 according to the present embodiment will be described using the flowchart of FIG. In the contamination state estimation apparatus 1 according to the present embodiment, first, a dose rate meter 10 is used to measure a surface dose rate that is a dose rate at a height of 1 cm from the ground surface and 1 m from the ground surface at a predetermined position (the same position). The air dose rate, which is the dose rate at the height of, is measured (S01, detection step). The measured values of the surface dose rate and the air dose rate are transmitted from the dose rate meter 10 to the information processing device 20.

  In the information processing apparatus 20, values of the surface dose rate and the air dose rate are received and input by the input unit 21 (S02, input step). The values of the surface dose rate and the air dose rate are output from the input unit 21 to the estimation unit 22. Subsequently, the estimation unit 22 calculates the value of the ratio between the surface dose rate and the air dose rate, and based on the calculated value and the threshold value and judgment criterion stored in advance, the contamination status around the predetermined position is determined. It is estimated (S03, estimation step). Information indicating the estimation result is output from the estimation unit 22 to the output unit 23. Subsequently, the output unit 23 outputs information indicating the estimation result so that the user (measurer) of the contamination state estimation apparatus 1 can refer to the information (S04, output step). The above is a process and operation | movement performed with the contamination condition estimation apparatus 1 which concerns on this embodiment.

  As described above, in the present embodiment, the contamination status is estimated from the values indicating the radiation doses at a plurality of different heights based on the relationship between these values. Therefore, it is possible to estimate the detailed contamination status as compared with the case where the values indicating the radiation doses at the respective heights are individually considered. Specifically, for example, based on the value of the ratio between the surface dose rate and the air dose rate, whether or not the contamination of the ground is limited, or whether or not there is a contamination source other than the ground Estimation can be performed.

  The contamination status by the contamination status estimation device 1 can be used for a decontamination plan. For example, decontamination is performed from top to bottom. First, decontamination is performed on trees higher than the roof of the building (STEP 0). Subsequently, rooftop / roof (STEP1) of building, rain gutter (STEP2), wall / window / door (STEP3), and finally the ground (STEP4). In addition, when performing decontamination of the ground, decontamination is performed in a certain direction from the back to the front.

  For example, in the case where it is estimated that there is a pollution source other than the ground according to the present embodiment, a decontamination plan for a surrounding tree or building is made in front of the ground (ground). Alternatively, the estimated location where the ground is surface-contaminated is first decontaminated before the location where the soil contamination is estimated to be in a limited range.

  In the present embodiment, the contamination state estimation apparatus 1 includes the dose rate meter 10, but the dose rate meter 10 may not necessarily be included. In this case, the input unit 21 of the information processing apparatus 20 may input a value indicating the radiation dose by an input operation on the information processing apparatus 20 by the user of the contamination state estimation apparatus 1, for example. Or the input part 21 of the information processing apparatus 20 is good also as receiving the value which shows a radiation dose from the dose rate meter which is a structure different from the contamination condition estimation apparatus 1. FIG.

  In the present embodiment, the height at which the radiation dose is measured is 1 cm and 1 m from the ground surface, but is not necessarily limited to the above height. Further, although the threshold (judgment criterion) is based on the relationship of “air dose rate × 2 = surface dose rate”, it is not necessarily limited to the value described above. The height and threshold value (judgment criteria) can be set as appropriate according to the situation of the location to be estimated for the contamination status.

  In the above-described embodiment, the dose rate is used as the value indicating the radiation dose. However, other types of values may be used as long as the values indicate the radiation dose. The above is the description of the first embodiment of the present invention.

Second Embodiment
Subsequently, a second embodiment of the present invention will be described. In the first embodiment described above, a relatively rough contamination state is estimated. However, when more information can be acquired by the dose rate meter 10, a more detailed contamination state can be estimated. Become. Also in the present embodiment, the contamination state estimation device 1 includes a dose rate meter 10 and an information processing device 20 as shown in FIG. 1 (in the present embodiment, the reference numerals are the same as those in the first embodiment). Use the same). In addition, the point which does not have description in particular is the structure similar to 1st Embodiment.

  In the present embodiment, the dose rate meter 10 detects a value indicating the radiation dose at three or more different heights (positions in different vertical directions) at a predetermined position (position in the same horizontal direction). To do. The dose rate meter 10 may be the same as that in the first embodiment, but a device that measures the dose rate with an optical fiber sensor so that the radiation dose at three or more different heights can be easily measured. It may be used. An apparatus that measures a dose rate with an optical fiber sensor is, for example, an apparatus that detects a dose rate in a linear shape, and detects a value indicating a plurality of radiation doses at different heights when the detection direction is a vertical direction. Can do. Alternatively, the apparatus can detect a value (radiation dose distribution) indicating a continuous radiation dose in the vertical direction. A conventional apparatus can be used as the apparatus.

  The height for detecting the radiation dose preferably includes two fixed heights such as 1 cm height and 1 m, for example. In addition, it is preferable that a height between 1 cm and 1 m and a height exceeding 1 m are included. The dose rate meter 10 outputs a dose rate that is a value indicating the measured radiation dose to the information processing apparatus 20. At this time, it is possible to grasp the height of the dose rate.

  The information processing apparatus 20 includes an input unit 21, an estimation unit 22, and an output unit 23, as in the first embodiment. The input unit 21 receives the information transmitted from the dose rate meter 10 to input a value indicating the radiation dose, and outputs the input value indicating the radiation dose to the estimation unit 22.

  The estimation unit 22 estimates an expression for estimating a value indicating the radiation dose according to the height based on at least one of the values indicating the radiation dose input by the input unit 21, and the radiation dose based on the formula Based on the comparison of the value indicating the radiation dose and the value indicating the radiation dose input by the input unit 21, the contamination state around the predetermined position is estimated.

  As described above, when there are no trees or structures in the surrounding area, the dose rate in the height direction depends on the size of the ground radiation source. FIG. 7A and FIG. 7B are graphs of dose rates corresponding to the height of the ground source 40 for each width. In Fig.7 (a) and FIG.7 (b), a horizontal axis shows the dose rate and the vertical axis | shaft has shown height. If the radiation source 40 is wide, the dose rate at 1 m height will be different even if the dose rate at 1 cm height is almost the same. In the example shown in FIG. 7B, the dose rate at a height of 1 m is higher because the area of the ground radiation source 40 is wider than in the example shown in FIG.

  FIG. 8 shows a graph of the dose rate according to the height when there are trees and structures around and there is a radiation source 50 other than the ground where they are the radiation sources. In this case, the dose rate in the height direction includes a dose rate based on the ground source 40 (indicated by a line L4 in FIG. 8) and a dose rate based on a source 50 other than the ground (indicated by a line L5 in FIG. 8). And is the value added together. Therefore, for example, the dose rate at a height of 1 m is higher than the dose rate based on the ground radiation source 40. On the other hand, when the radiation source 50 other than the ground is at a relatively high position, the dose rate at the height of 1 cm may not be much different from the dose rate based on the ground radiation source 40. In this case, if the size of the ground source 40 is estimated from the dose rate at a height of 1 cm and the dose rate at a height of 1 m, it is erroneously estimated that the size of the ground source 40 is wide. There is a risk of it. The estimation of the contamination status by the estimation unit 22 in the present embodiment appropriately estimates the presence of the radiation source 50 other than the ground even in the above case.

  The estimation unit 22 calculates a dose rate (a dose rate in the vertical direction) according to the height based on the dose rate at two heights among the dose rates that are values indicating the radiation dose input by the input unit 21. Estimate formulas (dose rate curve, dose rate distribution) for estimation. The above two heights are set in advance, and are, for example, heights of 1 cm and 1 m from the ground surface. Further, this equation is, for example, the equation (1) when there are no trees or structures (shielding bodies) around as described above. Specifically, the estimation unit 22 stores the formula (1) in advance, and the formula (1) so that dose rates at 1 cm height and 1 m height are placed as conceptually shown in FIG. ) Is calculated. In Equation (1), since θ is a value obtained from the height from the ground surface and the radius r of the radiation source 40, the estimation unit 22 substantially determines the dose rate at 1 cm height and 1 m height. Based on this, the radius r of the radiation source 40 is determined.

  The estimation unit 22 estimates (calculates) the dose rate based on the estimated dose rate curve L6. The dose rate estimated here is, for example, the height at which the dose rate is measured other than the dose rate used for the estimation of the dose rate curve L6. If the dose rate is measured uniformly in the vertical direction, the estimated height may be set in advance. In addition, the estimation target may have a plurality of heights.

  The estimation unit 22 compares the estimated dose rate (predicted value) with the measured value of the dose rate registered from the dose rate meter 10. This comparison is performed for each dose rate at the same height. Based on this comparison, the estimation unit 22 estimates the contamination state around the predetermined position. Specifically, the estimation unit 22 calculates the difference by subtracting the predicted value from the measured value (calculation of the difference corresponds to the above comparison), and estimates the contamination status from the difference. For example, as shown in FIG. 10, when there is a value that exceeds 20% of the predicted value in the difference (the line L7 indicates the measured value in FIG. 10), the estimation unit 22 has a source 50 other than the ground. Estimate that Moreover, as shown in FIG. 11, when there is a value that falls below −20% of the predicted value among the differences (the line L7 indicates the measured value in FIG. 11), the estimating unit 22 determines that the source 50 other than the ground is Presume that it exists. The above threshold value of 20% is a value according to the calibration standard of the device.

  When it is estimated that the source 50 other than the ground exists, the estimation unit 22 estimates that the source 50 other than the ground exists at the height where the difference between the measurement value and the predicted value is the largest. To do. For example, in the case of FIG. 11, it is estimated that a radiation source 50 other than the ground exists at a position of 1 m height. Note that the threshold for estimating that the radiation source 50 other than the ground exists is not necessarily limited to the above 20%, and may be set as appropriate according to the purpose of the estimation.

  As a result of the above comparison, when the differences at all heights (calculated differences) are within the range of ± 20% of the predicted value (that is, when the predicted value ≒ the measured value), The estimation unit 22 estimates that there is no radiation source 50 other than the ground (contamination source is only the ground surface).

  The estimation unit 22 outputs information indicating the estimated contamination status (for example, information on the presence / absence of the radiation source 50 other than the ground and the height of the radiation source 50 other than the ground) to the output unit 23. The output part 23 outputs the information input from the estimation part 22 by the method similar to 1st Embodiment.

  Subsequently, processing and operations (contamination status estimation method) executed by the contamination status estimation apparatus 1 according to the present embodiment will be described using the flowchart of FIG. In the contamination status estimation apparatus 1 according to the present embodiment, first, dosimeters at different heights (at least three points) from different ground surfaces at a predetermined position (the same position) by a dose rate meter 10 using an optical fiber sensor. It is measured (S11, detection step). The measured dose rate value is transmitted from the dose rate meter 10 to the information processing device 20.

  In the information processing apparatus 20, the dose rate value is received and input by the input unit 21 (S12, input step). The value of the dose rate is output from the input unit 21 to the estimation unit 22. Subsequently, an equation (dose rate curve, dose) for estimating the dose rate according to the height based on the values of the dose rate of two heights (for example, 1 cm height and 1 m height) by the estimation unit 22. Rate distribution) is estimated (S13, estimation step).

  Subsequently, the estimation unit 22 estimates a predicted value that is a dose rate of a predetermined height based on the estimated expression. Subsequently, the estimation unit 22 calculates a difference for each height between the calculated predicted value and the measured dose rate input from the input unit 21 (S14, estimation step). That is, a value obtained by comparing the predicted value and the measured value is calculated. Subsequently, the contamination state is estimated from the difference by the estimation unit 22 (S15, estimation step). Information indicating the estimation result is output from the estimation unit 22 to the output unit 23. Subsequently, the output unit 23 outputs information indicating the estimation result so that the user (measurer) of the contamination state estimation apparatus 1 can refer to the information (S16, output step). The above is a process and operation | movement performed with the contamination condition estimation apparatus 1 which concerns on this embodiment.

  As described above, according to the present embodiment, if the dose rate measurement values can be obtained at three or more heights by the dose rate meter 10, a more detailed contamination state can be estimated. For example, information on the presence / absence of the radiation source 50 other than the ground and the height of the radiation source 50 other than the ground can be estimated with higher accuracy than in the first embodiment. Thereby, a decontamination plan can be made more appropriately.

  In the above-described embodiment, the contamination state is estimated based on the value indicating the radiation dose with different heights at the same position. However, more detailed estimation is possible by estimating the contamination status based on values indicating the radiation dose at different positions in the horizontal direction.

  For example, as described above, when the estimation unit 22 estimates that the radiation source 50 other than the ground exists, the estimation unit 22 performs further detailed estimation using the dose rate measured at the surrounding position. That is, the estimation unit 22 estimates the position of the contamination source (ray source) based on the values indicating the radiation doses at a plurality of predetermined positions input by the input unit 21. For example, the dose rate is measured at three or more points in different vertical directions at three points around the point where the radiation source 50 other than the ground is estimated to exist. Specifically, the dose rate of three measurement points is measured in 120 ° increments at a position with a radius of about 1 m around the point where the radiation source 50 other than the ground is estimated to exist.

  Note that this measurement may be performed when it is estimated that a radiation source 50 other than the ground exists at a certain point (for example, by prompting the user to measure a surrounding point), or in advance. The measurement point may be determined in a planned manner.

  In this case, the input unit 21 inputs values indicating radiation doses at a plurality of different heights at a plurality of predetermined positions in the horizontal direction. At this time, information that can grasp the positional relationship with each other in the horizontal direction is also input. For example, when inputting the dose rate at the position where the positional relationship is determined, the dose rate may be input by an operation on the information processing apparatus 20 by the user. Or it is good also as inputting the positional information on the latitude and the longitude which are the coordinates of the position where the radiation dose was measured, for example. In this case, for example, a positioning device such as a GPS (Global Positioning System) is provided in the dose rate meter 10, and the position information obtained by the positioning device is transmitted to the information processing device 20 together with the measurement value.

  As described above, the estimation unit 22 determines the dose rate according to the height (dose rate in the vertical direction) at the surrounding positions (three measurement points of 120 ° each at a radius of about 1 m) as in the above-described embodiment. Is set to calculate the difference between the predicted value and the measured value. Subsequently, the estimation unit 22 creates a three-dimensional contour indicating the difference in the three-dimensional space by linear interpolation between the points where the difference is calculated. The estimation unit 22 cuts three-dimensional contours created at the same height, and estimates a direction with a large contour (difference) as the direction of the radiation source.

  According to said structure, a more detailed contamination condition can be estimated in a horizontal direction. Specifically, the direction of the radiation source (contamination position) can be estimated.

  DESCRIPTION OF SYMBOLS 1 ... Contamination condition estimation apparatus, 10 ... Dose rate meter, 20 ... Information processing apparatus, 21 ... Input part, 22 ... Estimation part, 23 ... Output part.

Claims (5)

An input means for inputting values indicating radiation doses at a plurality of different heights at a predetermined position;
Estimating means for estimating a contamination situation around the predetermined position from a value indicating the radiation dose input by the input means based on a relationship between values indicating the radiation dose at a plurality of different heights stored in advance. When,
Output means for outputting information indicating the contamination status estimated by the estimation means;
Equipped with a,
The estimation means estimates an expression for estimating a value indicating the radiation dose according to the height based on at least one of the values indicating the radiation dose input by the input means, and the radiation dose based on the expression A contamination status estimation apparatus that estimates a contamination status around the predetermined position based on a comparison between a value indicating the radiation dose and a value indicating the radiation dose input by the input means .   The estimation unit estimates a contamination state around the predetermined position based on a comparison between a ratio of a value indicating the radiation dose at two different heights input by the input unit and a preset threshold value. The contamination state estimation apparatus according to claim 1. The input means inputs values indicating radiation doses at a plurality of different heights at a plurality of predetermined positions in the horizontal direction,
The contamination state estimation apparatus according to claim 1, wherein the estimation unit estimates a position of a contamination source based on a value input by the input unit and indicating a radiation dose at the plurality of predetermined positions. The contamination state estimation apparatus according to any one of claims 1 to 3 , further comprising detection means for detecting a value indicating the radiation dose. A pollution status estimation method using a pollution status estimation device,
An input step for inputting values indicating radiation doses at a plurality of different heights at a predetermined position;
An estimation step for estimating a contamination state around the predetermined position from a value indicating the radiation dose input in the input step based on a relationship between values indicating the radiation dose at a plurality of different heights stored in advance. When,
An output step of outputting information indicating the contamination status estimated in the estimation step;
Only including,
In the estimation step, an equation for estimating a value indicating the radiation dose according to height is estimated based on at least one of the values indicating the radiation dose input in the input step, and the radiation dose based on the equation A contamination status estimation method for estimating a contamination status around the predetermined position based on a comparison between a value indicating the radiation dose and a value indicating the radiation dose input in the input step .

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