JP6677568B2 - Radioactivity distribution analysis system and radioactivity distribution analysis method - Google Patents

Description

  The present invention relates to a radioactivity distribution analysis system and a radioactivity distribution analysis method for deriving a radioactivity distribution (distribution of radioactive substances).

  In Patent Literature 1, the gamma ray counting rate detected by a radiation detector mounted on an unmanned helicopter is used to increase the accuracy of measurement and to more accurately measure the amount of radioactive cesium deposited on the surface of the earth. The air dose rate conversion count for conversion into the value of the rate is calculated in advance, and the attenuation coefficient of the gamma ray count rate due to air is calculated in advance from the relationship between the plurality of ground altitudes and the gamma ray count rate at one point specified in advance. By using a radiation detector and GPS mounted on an unmanned helicopter, the gamma ray counting rate at a certain point while flying near a nuclear facility at a certain ground altitude and the position information at that point are obtained in advance. It describes that the air dose rate at 1 m above the ground surface at that position is calculated using the attenuation coefficient, and the amount of radioactive cesium deposited on the ground surface is calculated.

  Patent Literature 2 discloses a structure DB that stores structure information for each of a plurality of structures, and a structure DB for storing a structure information for each of a plurality of structures in order to provide a radioactivity three-dimensional measurement device capable of measuring an accurate radioactivity distribution in a radiation handling work environment. A visible camera that captures a two-dimensional visible image, a gamma camera that measures the distribution of radiation intensity incident from the capturing direction, a capturing position storage unit, and a three-dimensional structure that calculates the shape and position of a structure from a plurality of visible images Part, a plurality of visible images and a gamma camera image, a surface radiation distribution conversion unit for converting the radiation intensity at the position of the shape surface of the structure, and a radiation intensity on the shape surface of the structure and measured by a gamma camera A surface radiation distribution difference site extraction unit that compares the radiation distribution and extracts sites with different radiation intensities at the same surface position, and estimates the radiation generation position for the extracted sites. And has Radioactivity three-dimensional measuring apparatus and a radiation estimator be converted into the amount of radioactivity is described.

JP 2014-145700 A JP 2013-108815 A

  Facilities handling radioactive materials include a nuclear power plant, a waste treatment facility, an accelerator facility, and a facility having a radioactive material control area. If a radioactive material leaks in the control area of these facilities, it is necessary to immediately confirm the distribution of the radioactive material in order to quickly carry out decontamination.

  Examples of radioactive material leakage include leakage of activated cooling water in a containment vessel during operation of a nuclear power plant, for example. During the operation of the nuclear power plant, the dose rate inside the reactor containment vessel is high and workers cannot access it easily. For this reason, even if the above-mentioned leakage occurs, it is difficult to immediately observe the situation visually and confirm the radioactivity distribution. As the radiation source when the above-mentioned leakage occurs, activated cooling water or an activated metal such as a pipe or a structural material can be considered.

  Atmospheric dose rates are extremely high due to the large amount of fission products in the reactor building, reactor containment vessel, and reactor pressure vessel of the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company. It is difficult. As the radiation source in the reactor building, the containment vessel, and the reactor pressure vessel, molten fuel, diffused fission products, activated metal in the reactor, and the like can be considered.

  In a situation where the radiation source situation cannot be easily observed by visual inspection or the like and the ambient dose rate is high, the situation is observed by remote control using a mobile device equipped with a radiation detector and an optical camera. It is possible.

  However, since mobile devices that can be put into such facilities need to be small, it is difficult to secure a sufficient payload. Therefore, it is difficult to mount a radiation detector shield necessary for operating the radiation detector normally at a high dose rate and a collimator for grasping the position of the radioactivity distribution with high accuracy. For this reason, nuclide analysis is difficult with a radiation detector, and the only measurable parameter is the dose rate.

  Further, when the observation area is in a steam environment or in turbid water, it is difficult to visually observe the surroundings. In this case, the moving device must be moved within a range where mobility can be secured, only the radiation detector is moved from that position by using a method such as hanging or throwing, and the radioactivity distribution must be estimated from the output at any position. Must. Therefore, there is a need for a system and method capable of analyzing a radioactivity distribution from limited measurements of the dose rate output of a radiation detector and its position coordinates.

  The above-mentioned Patent Document 1 is based on the assumption that the measurement is performed under a dose rate environment at a level that a worker can enter. Although nuclide analysis is feasible even with a radiation detector, it is difficult to use the detection method described in Patent Literature 1 in the severe measurement environment described above. Further, Patent Document 1 does not describe a method for deriving a position of a radioactivity distribution to be measured. Therefore, in the configuration related to Patent Document 1, it is difficult to realize the analysis of the radioactivity distribution from limited measured values such as the dose rate output of the radiation detector and its position coordinates.

  In Patent Document 2 described above, since a gamma camera is used, a large two-dimensional radiation detector, a shield, and a pinhole collimator are required. This makes it difficult to mount it on a mobile device. Further, it is necessary to image a measurement target using a visible camera, but it is difficult to visually observe the object in the above-described severe measurement environment. Therefore, in the configuration related to Patent Document 2, it is difficult to realize the analysis of the radioactivity distribution from the limited measured values of the dose rate output of the radiation detector and its position coordinates.

  The present invention relates to a radioactivity distribution analysis system and a radioactivity distribution analysis capable of analyzing a radioactivity distribution even in an environment where it is difficult for a worker in a radioactive material handling facility to enter and difficult to see with an optical camera or the like. Provide a way.

In order to solve the above problem, for example, a configuration described in the claims is adopted.
The present invention includes a plurality of means for solving the above-mentioned problems. For example, a radioactivity distribution analysis system for analyzing radioactivity distribution in a radioactive material handling facility, which measures a γ-ray dose rate. A radiation detector, a dose rate meter that derives a dose rate from the output of the radiation detector, a moving device that moves the radiation detector, and a position calculator that calculates three-dimensional position coordinates of the radiation detector. An analysis unit that analyzes a radioactivity distribution using the dose rate derived by the dosimeter and the three-dimensional position coordinates calculated by the position calculation unit; and an activity distribution analyzed by the analysis unit. And a display device for displaying, the analysis unit calculates a dose rate distribution using the dose rate derived by the dose rate meter, calculates the attenuation rate of the calculated dose rate distribution, calculated The radioactivity using the decay rate Analyzing the main nuclides in the cloth, analyzing the distance between the radiation detector and the main nuclide using the waveform of the dose rate distribution, the three-dimensional position coordinates and the trigonometric function, and measuring a plurality of dose rate distributions The radioactivity distribution is analyzed using a result, the distance, the main nuclide, and the three-dimensional position coordinates.

  ADVANTAGE OF THE INVENTION According to this invention, a radioactivity distribution can be analyzed even in the environment where it is difficult for a worker in a radioactive material handling facility to enter and visual observation with an optical camera or the like is difficult. Problems, configurations, and effects other than those described above will be apparent from the following description of the embodiments.

It is a figure showing the outline of the composition of the radioactivity distribution analysis system of Example 1 of the present invention. FIG. 4 is a diagram illustrating an example of a dose rate distribution in the case where the radiation source and the extension line in the moving direction of the radiation detector are orthogonal to each other in the first embodiment. FIG. 4 is a diagram illustrating an example of a dose rate distribution in the case where the radiation source and the extension line in the moving direction of the radiation detector are not orthogonal to each other in the first embodiment. FIG. 3 is a diagram illustrating an example of a positional relationship between a radioactive substance and a radiation detector according to the first embodiment. FIG. 4 is a diagram illustrating a dose rate distribution when the γ-ray energy is different in the first embodiment. 4 is a flowchart illustrating a procedure of analyzing a radioactivity distribution according to the first embodiment. It is a figure showing an example of an application place of a radioactivity distribution analysis system of Example 1. It is a figure which shows the outline of a structure of the radioactivity distribution analysis system of Example 2. FIG. 10 is a diagram illustrating a dose rate distribution when a radioactivity distribution having a high-energy beta-ray source according to the second embodiment is measured. FIG. 9 is a diagram schematically illustrating a configuration of a radioactivity distribution analysis system according to a third embodiment. FIG. 10 is a diagram illustrating a change over time in a dose rate distribution in Example 3. FIG. 14 is a diagram schematically illustrating a configuration of a radioactivity distribution analysis system according to a fourth embodiment. It is a figure showing the outline of the composition of the radioactivity distribution analysis system of Example 5. FIG. 14 is a diagram showing a dose rate distribution based on a plurality of γ-ray energy bands in Example 5. It is a figure which shows the outline of a structure of the radioactivity distribution analysis system of Example 6. FIG. 21 is a diagram illustrating an example of a positional relationship between a radioactivity distribution and a radiation detector according to a sixth embodiment. FIG. 21 is a diagram illustrating another example of the positional relationship between the radioactivity distribution and the radiation detector according to the sixth embodiment. FIG. 21 is a diagram illustrating another example of the positional relationship between the radioactivity distribution and the radiation detector according to the sixth embodiment.

  As described above, in an environment where it is difficult for workers to enter a facility handling radioactive materials and visual observation with an optical camera or the like is difficult, from the limited measurement values of the dose rate output of the radiation detector and its position coordinates If the analysis of radioactivity distribution can be realized, it will be possible to immediately observe the radioactivity distribution generated in the reactor containment vessel during operation of the nuclear power plant and in the reactor building of the Fukushima Daiichi Nuclear Power Station.

  In the present invention, even in such a difficult environment, and in a situation where there is only a limited measured value of the dose rate output of the radiation detector and its position coordinate, the radioactivity distribution can be immediately adjusted with the optimum configuration for the environment of the actual device. It was made based on new findings obtained from the results of various studies on an analysis system that can analyze and analyze the major nuclides and positions in the radioactivity distribution with high accuracy.

  Hereinafter, preferred embodiments of a radioactivity distribution analysis system and a radioactivity distribution analysis method according to the present invention will be specifically described with reference to the drawings, with the content of new findings.

<Example 1>
First Embodiment A radioactivity distribution analysis system and a radioactivity distribution analysis method according to a first embodiment of the present invention will be described with reference to FIGS. First, the system configuration will be described with reference to FIG. FIG. 1 shows a configuration diagram of the radioactivity distribution analysis system.

  The radioactivity distribution analysis system 100 according to the first embodiment illustrated in FIG. 1 analyzes radioactivity distribution in a radioactive substance handling facility such as a nuclear power plant, a waste treatment facility, an accelerator facility, and a facility having a radioactive material management area. Radiation detector 101, dose rate meter 102, radioactivity distribution analyzer (analyzing unit) 103, radiation detector moving device (moving device) 104, position calculating device (position calculating unit) 105, display device 106 , A first database 140.

  The radiation detector 101 is a detector having a function of measuring an atmosphere γ-ray dose rate at an installed location. As the sensor used in the radiation detector 101, a general sensor such as an ionization chamber type gas sensor, a phosphor, and a semiconductor type solid state sensor can be used. The output obtained by the radiation detector 101 is transmitted to the dose rate meter 102 via an electric cable or an optical fiber cable.

  The dose rate meter 102 derives a dose rate from the output obtained by the radiation detector 101. The outputs from the dose rate meter 102 are the dose rate and the time at which the dose rate was collected.

  The radiation detector moving device 104 has the radiation detector 101 mounted thereon and is a device for moving the radiation detector 101 to an arbitrary position. The radiation detector moving device 104 is, for example, a small vehicle including a pair of crawlers. In addition, it is not limited to a small vehicle equipped with a crawler, but may be any moving device that can move the radiation detector 101, for example, a small moving object equipped with wheels, or a moving object imitating an animal or an insect. , A drone or the like.

  The position calculating device 105 is a device that calculates the three-dimensional position coordinates of the radiation detector 101 mounted on the radiation detector moving device 104, and is, for example, a device that calculates a moving distance of the radiation detector 101 with respect to a GPS or a reference point. is there. The output of the position calculation device 105 is three-dimensional position coordinates and the time at that position.

  The radioactivity distribution analyzer 103 collects the outputs of the dose rate meter 102 and the position calculator 105, and collects the output of the dose rate meter 102 and the three-dimensional radiation detector 101 calculated by the position calculator 105. This is a device that analyzes the distribution of radioactivity using the position coordinates. Hereinafter, the analysis method will be described in more detail with reference to FIGS.

  2 and 3 show an example of the dose rate distribution. FIG. 2 shows a dose rate distribution when the radioactivity distribution exists in the traveling direction of the radiation detector 101, and FIG. 3 shows a dose rate distribution when the radioactivity distribution does not exist, based on the surface on which the radioactivity distribution is deposited. The horizontal axis indicates the distance between the surface and the radiation detector, and the vertical axis indicates the dose rate at that distance.

  The radioactivity distribution analyzer 103 first calculates a dose rate distribution from the dose rates derived by the dose rate meter 102.

  Next, the radioactivity distribution analyzer 103 calculates the attenuation rate of the calculated dose rate distribution. The dose rate is attenuated mainly by the solid angle and the shielding effect of a substance existing between the radioactivity distribution and the radiation detector, for example, air in the air and water in the water. It is desired that a substance existing between the radioactivity distribution and the radiation detector be specified in advance by various means capable of specifying an atmospheric state.

  When the dose rate distribution as shown in FIG. 2 is obtained, for example, the dose rate is y, the distance between the radiation distribution deposition surface and the radiation detector is x, and the coefficient is α, the exponential function y = Fitting can be performed with αexp (−μx). In this case, the attenuation rate can be expressed by μ indicating the slope of the exponential function.

  On the other hand, when the radioactivity distribution does not exist in the traveling direction of the radiation detector 101, the dose rate distribution is as shown in FIG. FIG. 3 shows, in addition to the dose rate distribution 116 shown in FIG.

  When it is determined that the dose rate distribution has a shape like the dose rate distribution 117, the radioactivity distribution analyzer 103 converts a variable of the exponential function into a trigonometric function when fitting the exponential function to the dose rate distribution. To derive a coefficient for realizing the fitting. Then, the decay rate is calculated from the slope of the exponential function obtained by the fitting. At the time of this fitting, the radioactivity distribution analyzer 103 performs matching with an attenuation rate stored in a first database 140 described later to narrow down whether the attenuation rate derived in advance is within an assumed range. Thus, the time required for fitting is reduced.

  In the case of the dose rate distribution 117 as shown in FIG. 3, the attenuation rate μ becomes small in a region where the distance between the radioactivity distribution deposition surface and the radiation detector 101 is short due to the solid angle. In this case, the variable x of the exponential function is converted to a trigonometric function.

  FIG. 4 shows an example of the positional relationship between the collection 114 of radioactive substances and the radiation detector 101.

  As shown in FIG. 4, when the radioactivity distribution does not exist in the traveling direction of the radiation detector 101, a collection 114 of radioactive substances is deposited on the radioactivity distribution deposition surface 118, and the radioactivity distribution deposition surface and the radiation detector 101 And a distance 120 between the end of the radioactivity distribution and the radiation detector 101 on the radioactivity distribution deposition surface, and a distance 121 between the end of the radioactivity distribution and the radiation detector 101. it can. Here, the distance 119 between the radioactivity distribution deposition surface and the radiation detector 101 is assumed to be known by the position calculation device 105.

  In such a case, when the distance 121 between the end of the radioactivity distribution and the radiation detector 101 is a, and the angle between the radioactivity distribution deposition surface and the detector position is θ, the exponential function to be fitted is y = exp ( −μx), the variable x of the exponential function can be expressed as x = a · sin θ. Using this trigonometric function, fitting to the dose rate distribution is performed using θ of the trigonometric function as a parameter. In this fitting, the optimal θ is extracted, and the optimal θ is fitted by an exponential function to derive the attenuation rate μ.

  Next, the radioactivity distribution analyzer 103 analyzes the main nuclides in the radioactivity distribution using the calculated attenuation rate μ. At this time, the radioactivity distribution analyzer 103 calculates the main γ-ray energy band of the radiation source in the radioactivity distribution from the value of the attenuation factor μ, and uses the calculated γ-ray energy band to calculate the main nuclide in the radioactivity distribution. Is analyzed.

More specifically, the obtained attenuation rate μ is set to one of the ranges of the attenuation rate μ in the first database 140 (μ ₁ <μ ₂ <... Μ _n <... (N = 1, 2,...)). By performing the comparison, the γ-ray energy band corresponding to the attenuation rate μ is calculated.

  FIG. 5 shows the dose rate distribution when the γ-ray energy is different.

  As shown in FIG. 5, the magnitude of the attenuation rate depends on the γ-ray energy when the distance between the radiation source and the radiation detector 101 and the shielding material are the same. Accordingly, the dose rate distribution 122 of the high energy γ-ray has a lower attenuation rate than the dose rate distribution 123 of the medium energy γ-ray and the dose rate distribution 124 of the low energy γ-ray. Therefore, from the obtained attenuation rate, a radionuclide corresponding to the γ-ray energy band is extracted from the first database 140 and is regarded as a main nuclide in the radioactivity distribution.

  Next, the radioactivity distribution analyzer 103 uses the waveform of the dose rate distribution, the three-dimensional position coordinates, and the trigonometric function to connect the radiation detector 101 with the end of the radioactivity distribution on the surface where the radioactivity distribution is deposited. The distance is derived, and the distance between the radiation detector 101 and the radioactivity distribution is analyzed therefrom.

  Here, assuming that the distance 120 between the end of the radioactivity distribution on the radioactivity distribution deposition surface shown in FIG. 4 and the radiation detector is b, it can be expressed as b = a · cos θ.

  Therefore, the radioactivity distribution analyzer 103 sets θ = 90 ° when the waveform of the dose rate distribution is a waveform when the radioactivity distribution is present in the traveling direction of the radiation detector 101 as shown in FIG. And the distance b is zero. On the other hand, when the radioactivity distribution as shown in FIG. 3 does not exist in the traveling direction of the radiation detector 101, it is derived using the equation of b = a · cos θ as it is.

  From the analysis results so far, an output of a radionuclide that is a main nuclide in the radioactivity distribution and an output of a distance 120 between the radioactivity distribution and the radiation detector 101 are obtained. With the above, the radioactivity distribution analysis processing at one measurement point is performed.

  Next, the radioactivity distribution analyzer 103 analyzes the radioactivity distribution using the measurement results of the plurality of dose rate distributions and the analysis results of the distance, the main nuclide, and the three-dimensional position coordinates.

  Specifically, the radioactivity distribution analyzer 103 superimposes the output of the radionuclide at each measurement point and the output of the distance 120. Thus, the two-dimensional distribution of the radioactive material on the radioactivity distribution deposition surface and the main nuclides in the radioactivity distribution are calculated. The calculation result is output to the display device 106 and monitored.

  The display device 106 is a display device such as a monitor on which the analysis result of the radioactivity distribution analyzed by the radioactivity distribution analysis device 103 is displayed.

  The first database 140 is a radionuclide database in which the attenuation factors μ of a plurality of radionuclides are stored, and stores data in which main nuclides that may exist in the measurement environment are extracted in advance. Examples of the stored radionuclides include N-16, N-13, F-18, O-19, Co-60, Co-58, Cs-137, Cs-134, and Eu-154. . When classified into γ-ray energies, when N-16 is set as a nuclide that emits high-energy γ-rays, Co-60, O-19, and Eu-154 are listed as medium-energy γ-ray emitting nuclides. Examples of the low energy γ-ray emitting nuclide include N-13, F-18, Co-58, Cs-137 and Cs-134.

  Next, a radioactivity distribution analysis method according to the present embodiment will be described with reference to FIG.

  First, the radioactivity distribution analysis system 100 starts analysis (step S301).

  Next, the radiation detector 101 is moved to the measurement point by the radiation detector moving device 104 (step S302).

  Next, it is determined whether the radioactivity distribution analyzer 103 measures the dose rate distribution (step S303). If there are measurement points or if there are more measurement points, the process proceeds to step S304. If measurement at all measurement points has been completed, the process proceeds to step S317.

  Next, the γ-ray dose rate is measured by the radiation detector 101, and the dose rate is derived by the dose rate meter 102. Thereafter, the radiation detector 101 is moved by the radiation detector moving device 104 in the direction in which the radioactivity distribution is assumed to be deposited, the γ-ray dose rate is measured again by the radiation detector 101, and the dose rate meter 102 Deriving the dose rate is repeated a plurality of times to obtain the dose rate distribution (step S304).

  Next, the radiation distribution analyzer 103 performs fitting between the dose rate distribution derived in step S304 and an exponential function (here, y = αexp (−μx) is used) (step S305).

  Next, the radioactivity distribution analyzer 103 determines whether an exponential function can be fitted to the dose rate distribution by using an exponential function y = αexp (−μx) (step S306). If it is determined that the fitting is possible, the process proceeds to step S311. If it is determined that the fitting is not possible, the process proceeds to step S307.

  If it is determined in step S306 that fitting is not possible, the exponential function is changed in the radioactivity distribution analyzer 103 (y = exp (−μx)), and the variable of the exponential function is changed to a trigonometric function (x = a (Sin θ) (step S307).

  Next, the radiation distribution analyzer 103 performs fitting between the dose rate distribution and the exponential function using the coefficient θ of the trigonometric function as a parameter (step S308).

  Next, the optimum θ is selected in the radioactivity distribution analyzer 103 (step S309).

  Next, the radiation distribution analyzer 103 performs fitting with the dose rate distribution using an exponential function at the optimum θ (step S310).

  Next, the attenuation factor μ is derived in the radioactivity distribution analyzer 103 (step S311).

Next, in the radioactivity distribution analyzer 103, the attenuation rate μ derived in step S311 is stored in the first database 140 in the range of the attenuation rate for each radioactive element (μ ₁ , μ ₂ ,..., Μ _n ,. (Step S312).

  Next, the radioactivity distribution analyzer 103 determines whether or not the range of the attenuation rate in the first database 140 used in the comparison in step S312 is closest to the attenuation rate μ derived in step S311 (step S313). . If it is determined that it is the closest (closest), the process proceeds to step S314. If it is not the closest, the process returns to step S312, and comparison with the next range of the attenuation factor for each radioactive element is performed.

  Next, in order to identify a radioactive element that emits γ-rays of energy belonging to the γ-ray energy band in the range of the attenuation rate determined to be closest in step S313 in the radioactivity distribution analyzer 103 as a primary nuclide, The collation is performed using the data stored in the database 140 (step S314).

  Next, in the radioactivity distribution analyzer 103, it is determined whether or not the γ-ray energy band of the main nuclide in the first database 140 matches or is sufficiently close (step S315). If it is determined that they are coincident or sufficiently close, the nuclide emitting the coincident energy band is regarded as the main nuclide, and the process proceeds to step S316. On the other hand, if it is not determined that the distance is sufficiently close, the process returns to step S314, the comparison with the first database 140 is performed again, and the main nuclide is analyzed.

  Next, the radioactivity distribution analyzer 103 calculates the distance between the radioactivity distribution and the radiation detector 101 (step S316). Thereafter, the process returns to step S304.

  When the measurement at all the measurement points is completed and the process proceeds to step S317, the radioactivity distribution analyzer 103 superimposes the output at each measurement point (step S317).

  Next, the radioactivity distribution analyzer 103 calculates a three-dimensional position and a main nuclide of the radioactivity distribution (step S318).

  Next, the analysis result of the radioactivity distribution analyzer 103 is output to the display device 106 (step S319).

  Thereafter, the radioactivity distribution analysis system 100 ends the analysis (step S320).

  6, the measurement step and the dose rate distribution calculation step correspond to step S304, the main nuclide analysis step corresponds to steps S305 to S315, the distance analysis step corresponds to step S316, and the radioactivity distribution analysis step This corresponds to steps S302 to S318.

  FIG. 7 shows an example of a location to which the radioactivity distribution analysis system 100 is applied. Here, as an example, a configuration diagram for analyzing a collection 114 of radioactive materials in a nuclear power plant is shown.

  7, a reactor containment vessel 108, a reactor pressure vessel 109, a reactor recirculation system 110, a reactor pressure suppression chamber 111, a torus chamber 112, and a penetrating portion 113 are arranged in a reactor building 107.

  At each location, the radiation detector moving device 104 equipped with the radiation detector 101 is put in, and the radioactivity distribution is calculated via the cable 115 by using the functions of the dose rate meter 102, the position calculating device 105, and the like shown in FIG. To analyze.

  Next, effects of the present embodiment will be described.

  In the first embodiment of the radioactivity distribution analysis system and the radioactivity distribution analysis method of the present invention described above, the radiation detector 101, the dose rate meter 102, the radiation detector moving device 104, the position calculation device 105, and the radioactivity distribution analysis device 103 The radioactivity distribution analysis system 100 including the display device 106 can analyze a dose rate distribution, a radioactivity distribution, and its main nuclide. Therefore, it is possible to display the radioactivity distribution and which radioactive substance the main nuclide is. Due to these effects, the limited measurement of the dose rate output of the radiation detector and its position coordinates even in an environment where it is difficult for workers at facilities handling radioactive materials to enter and difficult to see with an optical camera etc. From the values, the radioactivity distribution and its major nuclides can be observed more quickly than before.

  Further, the radioactivity distribution analyzer 103 calculates an attenuation rate μ from a slope obtained by fitting an exponential function to the dose rate distribution, and calculates a main γ-ray energy of the radiation source in the radioactivity distribution from the value of the attenuation rate μ. By calculating the band and analyzing the main nuclides in the radioactivity distribution using the calculated γ-ray energy band, the decay rate can be easily derived, and the main nuclides in the radioactivity distribution can be analyzed. it can. As a result, the main nuclides in the distribution of radioactivity can be analyzed with higher accuracy, and it is possible to contribute to the reduction of exposure due to operations such as decontamination.

  Further, when fitting the exponential function to the dose rate distribution, the radioactivity distribution analyzer 103 converts the variable of the exponential function into a trigonometric function to derive a coefficient for implementing the fitting, and then fits the exponential function. By calculating the attenuation factor μ from the obtained slope, it is possible to calculate the main γ-ray energy band of the source with high accuracy and analyze the main nuclides in the radioactivity distribution. In this way, it is also possible to analyze the main nuclides in the radioactivity distribution with higher accuracy, and to contribute to the reduction of exposure due to operations such as decontamination.

  Further, the radioactivity distribution analyzer 103 derives, from the trigonometric function, the distance between the radiation detector 101 and the end of the radioactivity distribution on the surface where the radioactivity distribution is deposited, thereby obtaining the radiation on the radioactivity distribution deposition surface. It is possible to derive the distance b between the detector and the end of the radioactivity distribution, and even in a situation where it is difficult to visually confirm the radioactivity distribution with an optical camera or the like, the three-dimensional position of the radioactivity distribution can be obtained with higher accuracy. It becomes possible to analyze with.

  Further, by providing the first database 140 in which the attenuation factors μ of a plurality of radionuclides are stored and used for fitting with the measured dose rate distribution, it is possible to quickly analyze the radioactivity distribution. As a result, it is possible to contribute to quick drafting of a work plan such as decontamination.

<Example 2>
Second Embodiment A radioactivity distribution analysis system and a radioactivity distribution analysis method according to a second embodiment of the present invention will be described with reference to FIGS. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The same applies to the following embodiments. FIG. 8 is a diagram showing a configuration diagram of the radioactivity distribution analysis system of the present embodiment.

  As shown in FIG. 8, the radioactivity distribution analysis system 100A of the present embodiment is obtained by providing a beta detector 150 in the radiation detector 101 of the radioactivity distribution analysis system 100 of the first embodiment.

  FIG. 9 shows a dose rate distribution when the radioactivity distribution having a high-energy beta-ray source, which is exclusively targeted by the radioactivity distribution analysis system 100A of the present embodiment, is a measurement target.

  When a high energy beta ray source (for example, Sr-90 / Y-90) is included in the radioactivity distribution, the dose rate due to beta rays may not be negligible.

  In FIG. 9, as shown by the dose rate distribution 155, when the distance between the radioactivity distribution and the radiation detector 101 is short, the contribution of the high energy beta ray source cannot be ignored. Here, even though the beta ray has a high energy, its range is shorter than that of the gamma ray, so that the beta ray is sufficiently attenuated at a short distance. Therefore, in order to minimize the influence of the high energy beta ray source, the radiation detector 101 is provided with a beta ray shield 150. As a material of the beta ray shield 150, an organic substance such as acrylic, a metal such as SUS, copper, and aluminum, and a ceramic such as aluminum oxide are used. By covering the radiation detector 101 with the beta-ray shield 150 formed of these materials, it is possible to obtain the dose rate distribution 116 substantially free from the influence of beta rays.

  Other configurations and operations are substantially the same as the configurations and operations of the radioactivity distribution analysis system 100 according to the first embodiment described above, and the details are omitted.

  In the radioactivity distribution analysis system and the radioactivity distribution analysis method according to the second embodiment of the present invention, substantially the same effects as in the radioactivity distribution analysis system and the radioactivity distribution analysis method according to the first embodiment described above can be obtained.

  Also, by providing the radiation detector 101 with the beta ray shield 150, the dose rate of beta ray contribution can be removed, so even when measuring a radioactivity distribution including a high energy beta ray source, high accuracy can be achieved. The gamma-ray dose rate can be measured. This makes it possible to analyze the distribution of radioactivity with higher accuracy, thereby contributing to a reduction in exposure due to operations such as decontamination.

<Example 3>
Third Embodiment A radioactivity distribution analysis system and a radioactivity distribution analysis method according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 10 shows a configuration diagram of the radioactivity distribution analysis system of the present embodiment.

  The radioactivity distribution analysis system 100B of the present embodiment shown in FIG. 10 observes the time-dependent change of the dose rate and calculates the decay rate of the dose rate, so that the half-life of the radiation source emitting the gamma ray energy band to be measured can be calculated. It is an estimate.

  The radioactivity distribution analyzer 103A estimates the half-life of the radioactive substance in the radioactivity distribution based on the temporal change of the dose rate distribution measured by the radiation detector 101, and calculates the estimated half-life and the decay rate μ. To analyze major nuclides in radioactivity distribution.

  FIG. 11 shows the change over time in the dose rate distribution.

  As shown in FIG. 11, when the dose rate distribution is measured again after a certain period of time has elapsed after measuring the dose rate distribution 116, the dose rate according to the half-life of the source as shown in the dose rate distribution 125 shown in FIG. 11 is obtained. Attenuation is seen. The radioactivity distribution analyzer 103A estimates the half-life from the decay rate of the absolute value of the dose rate and the elapsed time obtained here. Then, in the analysis of the main nuclide obtained from the attenuation rate μ of the dose rate distribution, the estimated half-life information is added.

  Other configurations and operations are substantially the same as the configurations and operations of the radioactivity distribution analysis system 100 according to the first embodiment described above, and the details are omitted.

  In the third embodiment of the radioactivity distribution analysis system and the radioactivity distribution analysis method of the present invention, substantially the same effects as those of the above-described first embodiment of the radioactivity distribution analysis system and the radioactivity distribution analysis method can be obtained.

  In addition, the half-life of the radioactive substance in the radioactivity distribution is estimated based on the temporal change of the dose rate distribution measured by the radiation detector 101, and the radioactivity distribution is estimated using the estimated half-life and the decay rate μ. By analyzing the main nuclides, the accuracy of analysis of the main nuclides included in the radioactivity distribution can be further improved, which can contribute to a reduction in exposure due to operations such as decontamination.

<Example 4>
Fourth Embodiment A radioactivity distribution analysis system and a radioactivity distribution analysis method according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 12 shows a configuration diagram of the radioactivity distribution analysis system of the present embodiment.

  As shown in FIG. 12, the radioactivity distribution analysis system 100C of the present embodiment includes an emission device 126, a detector recovery device 127, and a moving distance correction device 128 in addition to the radioactivity distribution analysis system 100 shown in FIG. And a radioactivity distribution analyzer 103B in place of the radioactivity distribution analyzer 103.

  The radioactivity distribution analysis system 100C includes a radiation detector 101, a dose rate meter 102, a radioactivity distribution analyzer 103B, a radiation detector moving device 104, a position calculator 105, a display device 106, a first database 140, a release device 126, A detector recovery device 127 and a movement distance correction device 128 are provided.

  The emission device 126 is a device for further moving the radiation detector 101 mounted on the radiation detector moving device 104 from the radiation detector moving device 104. For example, the emission device 126 can radiate radiation to an area that cannot be accessed by the radiation detector moving device 104 by hanging the radiation detector 101 from the radiation detector moving device 104 or throwing the radiation detector 101 from the radiation detector moving device 104. The container 101 is turned on.

  The detector recovery device 127 winds the radiation detector 101 to the radiation detector moving device 104 by winding up a signal cable connecting the radiation detector 101 and the dose rate meter 102 or a pull-back cable provided in the radiation detector 101. It is a device for collecting.

  The moving distance correction device 128 is a device that measures the amount of cable sent out by the emission device 126 when the radiation detector 101 is emitted and the amount of unwinding of the cable when the cable is collected by the detector collection device 127. The corrected position information of the radiation detector 101 is corrected.

  The radioactivity distribution analyzer 103B has almost the same function as the radioactivity distribution analyzer 103 of the first embodiment. Furthermore, the three-dimensional position information of the radiation detector 101 is corrected using the moving distance at the time of collection of the radiation detector 101 measured by the moving distance correction device 128.

  Other configurations and operations are substantially the same as the configurations and operations of the radioactivity distribution analysis system 100 according to the first embodiment described above, and the details are omitted.

  In the fourth embodiment of the radioactivity distribution analysis system and the radioactivity distribution analysis method according to the present invention, substantially the same effects as those of the first embodiment of the radioactivity distribution analysis system and the radioactivity distribution analysis method described above can be obtained.

  An emission device 126 for emitting the radiation detector 101 from the radiation detector moving device 104 and a detector collection device 127 for collecting the radiation detector 101 emitted by the emission device 126 to the radiation detector moving device 104 are provided. With the provision, the radiation detector 101 can be arranged in an area that cannot be accessed by the radiation detector moving device 104, so that the dose rate can be measured over a wider range. Further, the radiation detector 101 can be collected up to the radiation detector moving device 104. By these effects, the measurement of the dose rate distribution in a narrow part, a low place, and a high place can be repeatedly performed, and a more accurate analysis of the radioactivity distribution in a wider range can be realized.

  Further, a movement distance correction device 128 for measuring the movement distance of the radiation detector 101 emitted by the emission device 126 is provided, and the radioactivity distribution analyzer 103B performs the movement of the radiation detector 101 measured by the movement distance correction device 128. By correcting the three-dimensional position information of the radiation detector 101 using the distance, the position information of the radiation detector can be corrected with high accuracy, and the three-dimensional position coordinates of the radiation detector 101 can be obtained with higher accuracy. be able to.

  Further, the emission device 126 puts the radiation detector 101 into an area that cannot be accessed by the radiation detector movement device 104 even by a simple mechanism by hanging or throwing the radiation detector 101 from the radiation detector movement device 104. I can do it.

  Further, the detector recovery device 127 connects the radiation detector 101 to the radiation detector moving device 104 using a signal cable for connecting the radiation detector 101 and the dose rate meter 102 or a pull-back cable provided in the radiation detector 101. By collecting, the radiation detector 101 can be easily collected, the size of the radiation detector moving device 104 can be reduced, and a narrower part can be accessed.

<Example 5>
Fifth Embodiment A radioactivity distribution analysis system and a radioactivity distribution analysis method according to a fifth embodiment of the present invention will be described with reference to FIGS. FIG. 13 shows a configuration diagram of the radioactivity distribution analysis system of the present embodiment.

  The radioactivity distribution analysis system 100D of the present embodiment shown in FIG. 13 uses a plurality of exponential functions to fit a dose rate distribution, and analyzes (specifies) two or more major nuclides from two or more attenuation rates. It is.

  The radioactivity distribution analyzer 103C fits the dose rate distribution using a plurality of exponential functions, and analyzes two or more major nuclides from two or more attenuation factors μ.

  FIG. 14 shows a dose rate distribution based on a plurality of γ-ray energy bands.

  As shown in FIG. 14, when radiation sources in different γ-ray energy bands are included in the radioactivity distribution, the dose rate distribution 156 shows the contribution of low-energy γ-rays near the radioactivity distribution (influence of the dose rate distribution 156A). In the distance, the contribution of high energy γ-rays (the effect of the dose rate distribution 156B) is seen. The low and high energies shown here are relative indices for the respective γ-ray energies.

  When a dose rate distribution having, for example, two attenuation rates is observed as shown in FIG. 14, fitting is performed with an exponential function to the dose rate distribution 156A, and similarly, the dose rate distribution 156B is used before. By performing fitting with an exponential function different from the above, two decay rates are derived. Two or more major nuclides are analyzed based on the obtained decay rates.

  Other configurations and operations are substantially the same as the configurations and operations of the radioactivity distribution analysis system 100 according to the first embodiment described above, and the details are omitted.

  In the fifth embodiment of the radioactivity distribution analysis system and the radioactivity distribution analysis method according to the present invention, substantially the same effects as those of the first embodiment of the radioactivity distribution analysis system and the radioactivity distribution analysis method described above can be obtained.

  Further, by fitting a dose rate distribution using a plurality of exponential functions and analyzing two or more major nuclides from two or more attenuation factors μ, highly accurate analysis of the major nuclides becomes possible. As a result, it is possible to further contribute to a reduction in exposure due to operations such as decontamination.

  Although two attenuation rates have been described here, when the dose rate distribution is more complicated, three or more attenuation rates can be used using three or more exponential functions.

<Example 6>
Sixth Embodiment A radioactivity distribution analysis system and a radioactivity distribution analysis method according to a sixth embodiment of the present invention will be described with reference to FIGS. FIG. 15 shows a configuration diagram of the radioactivity distribution analysis system of the present embodiment.

  The radioactivity distribution analysis system 100E of this embodiment shown in FIG. 15 includes a second database 145 storing the relationship between the shape of the radioactivity distribution and the dose rate distribution, and b = a · from the trigonometric function x = a · sin θ. By deriving cos θ, the distance between the radiation detector and the end of the radioactivity distribution on the radioactivity distribution deposition surface is derived.

  As shown in FIG. 15, the radioactivity distribution analysis system 100E of the present embodiment includes a radiation detector 101, a dose rate meter 102, a radioactivity distribution analyzer 103D, a radiation detector moving device 104, a position calculator 105, a display device. In addition to the first database 140 and the first database 140, a second database 145 that stores the relationship between the shape of the radioactivity distribution and the dose rate distribution is provided.

  The radioactivity distribution analyzer 103D has almost the same function as the radioactivity distribution analyzer 103 of the first embodiment. Further, the radioactivity distribution analyzer 103D analyzes the radioactivity distribution using the relationship between the shape of the radioactivity distribution stored in the second database 145 and the dose rate distribution.

  FIG. 16 shows an example of the positional relationship between the radioactivity distribution and the radiation detector. Here, the collection 132 of radioactive substances is formed in a block shape. In this case, the dose rate distribution shows a pattern peculiar to the block shape. Therefore, in the present embodiment, the radioactivity distribution analyzer 103D obtained the relationship between the various radioactivity distribution shapes stored in the second database 145 and the dose rate distribution in addition to the exponential function and the trigonometric function. The pattern is compared with the dose rate distribution, the pattern is identified as a pattern peculiar to the block shape, and the distance between the radiation detector 101 and the end of the radioactivity distribution is analyzed.

  FIG. 17 shows another example of the positional relationship between the radioactivity distribution and the radiation detector. Here, the collection 133 of radioactive substances is formed in a triangular shape. In this case, the dose rate distribution shows a pattern unique to a triangular shape. Therefore, similarly to the analysis method using the step-like shape shown in FIG. 16, the radioactivity distribution analyzer 103 </ b> D outputs various radioactivity distributions stored in the second database 145 in addition to the exponential function and the trigonometric function. The relationship between the shape and the dose rate distribution is compared with the obtained dose rate distribution, and a pattern specific to the triangular shape is specified, and then the radiation detector 101 and the end of the radioactivity distribution are identified. Analyze the distance.

  FIG. 18 shows still another example of the positional relationship between the radioactivity distribution and the radiation detector. Here, the collection of radioactive substances 134 is formed in a semi-elliptical shape. In this case, the dose rate distribution shows a pattern unique to a semi-elliptical shape. Therefore, as in the case of FIGS. 16 and 17, the radioactivity distribution analyzer 103 </ b> D calculates various radioactivity distribution shapes and dose rate distributions stored in the second database 145 in addition to the exponential function and the trigonometric function. Is compared with the obtained dose rate distribution, a pattern specific to the semi-elliptical shape is specified, and the distance between the radiation detector 101 and the end of the radioactivity distribution is analyzed.

  Other configurations and operations are substantially the same as the configurations and operations of the radioactivity distribution analysis system 100 according to the first embodiment described above, and the details are omitted.

  In the radioactivity distribution analysis system and the radioactivity distribution analysis method according to the sixth embodiment of the present invention, substantially the same effects as those of the radioactivity distribution analysis system and the radioactivity distribution analysis method according to the first embodiment can be obtained.

  In addition, by providing the second database 145 that stores in advance the relationship between the shape of a plurality of radioactivity distributions and the dose distribution, the radioactivity distribution can be analyzed more accurately and quickly.

<Others>
Note that the present invention is not limited to the above-described embodiment, and includes various modifications. The above embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described above. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of one embodiment can be added to the configuration of another embodiment. Further, for a part of the configuration of each embodiment, it is also possible to add / delete / replace another configuration.

100, 100A, 100B, 100C, 100D, 100E Radioactivity distribution analysis system 101 Radiation detector 102 Dose rate meter 103 Radioactivity distribution analyzer (analysis unit)
103A, 103B, 103C, 103D ... radioactivity distribution analyzer 104 ... radiation detector moving device (moving device)
105: Position calculation device (position calculation unit)
106 display device 107 reactor building 108 reactor containment vessel 109 reactor pressure vessel 110 reactor recirculation system 111 reactor pressure suppression chamber 112 torus chamber 113 penetration parts 114, 132, 133 and 134 ... a collection of radioactive substances 115 ... cables 116, 117, 122, 123, 124, 155, 156, 156A, 156B ... dose rate distribution 118 ... radioactivity distribution deposition surface 119 ... distance 120 between the radioactivity distribution deposition surface and the radiation detector ... Distance 121 between the end of the radioactivity distribution on the radioactivity distribution deposition surface and the radiation detector 121 ... Distance 125 between the end of the radioactivity distribution and the radiation detector 125 ... Dose rate distribution 126 after a certain period of time 126 ... Emission device 127 Detector recovery device 128 Moving distance correction device 140 First database 145 Second database 150 Beta ray shield

Claims (14)

A radioactivity distribution analysis system for analyzing radioactivity distribution in a radioactive material handling facility,
a radiation detector that measures a gamma-ray dose rate;
A dose rate meter that derives a dose rate from the output of the radiation detector,
A moving device for moving the radiation detector;
A position calculator for calculating three-dimensional position coordinates of the radiation detector;
Using the dose rate derived by the dose rate meter and the three-dimensional position coordinates calculated by the position calculation unit, an analysis unit that analyzes the radioactivity distribution,
A display device for displaying the radioactivity distribution analyzed by the analysis unit,
The analysis unit,
Calculate the dose rate distribution using the dose rate derived by the dose rate meter,
Calculate the calculated attenuation rate of the dose rate distribution, analyze the main nuclides in the radioactivity distribution using the calculated attenuation rate,
Analyzing the distance between the radiation detector and the main nuclide using the waveform of the dose rate distribution, the three-dimensional position coordinates and the trigonometric function,
A radioactivity distribution analysis system, wherein the radioactivity distribution is analyzed using a plurality of measurement results of dose rate distributions, the distance, the main nuclide, and the three-dimensional position coordinates. The radioactivity distribution analysis system according to claim 1,
The analysis unit,
The attenuation rate is calculated from a slope obtained by fitting an exponential function to the dose rate distribution,
Calculating a main γ-ray energy band of the radiation source in the radioactivity distribution from the value of the attenuation rate, and analyzing the main nuclides in the radioactivity distribution using the calculated γ-ray energy body; Distribution analysis system. The radioactivity distribution analysis system according to claim 2,
The analysis unit,
When fitting an exponential function to the dose rate distribution, after converting a variable of the exponential function to a trigonometric function to derive a coefficient for realizing the fitting, the attenuation is obtained from a slope obtained by fitting the exponential function. A radioactivity distribution analysis system characterized by calculating the rate. The radioactivity distribution analysis system according to claim 3,
The analysis unit,
A radioactivity distribution analysis system, wherein a distance between the radiation detector and an end of the radioactivity distribution on a surface on which the radioactivity distribution is deposited is derived using the trigonometric function. The radioactivity distribution analysis system according to claim 2,
A first database for storing attenuation rates of the plurality of radionuclides;
The said analysis part uses the attenuation rate stored in the said 1st database at the time of the said fitting, The radioactivity distribution analysis system characterized by the above-mentioned. The radioactivity distribution analysis system according to claim 1,
A radiation distribution analysis system, wherein the radiation detector has a beta-ray shield. The radioactivity distribution analysis system according to claim 1,
The analysis unit estimates the half-life of the radioactive material in the radioactivity distribution based on the temporal change of the dose rate distribution measured by the radiation detector, using the estimated half-life and the decay rate A radioactivity distribution analysis system, characterized in that main nuclides in the radioactivity distribution are analyzed. The radioactivity distribution analysis system according to claim 1,
An emission device for emitting the radiation detector from the mobile device;
A recovery device that recovers the radiation detector emitted by the emission device to the moving device. The radioactivity distribution analysis system according to claim 8,
The apparatus further includes a movement distance correction device that measures a movement distance of the radiation detector emitted by the emission device,
The radioactivity distribution analysis system, wherein the analysis unit corrects three-dimensional position information of the radiation detector using a moving distance of the radiation detector measured by the moving distance correction device. The radioactivity distribution analysis system according to claim 8,
The radiation distribution analysis system, wherein the emission device performs at least one of hanging and throwing the radiation detector from the moving device. The radioactivity distribution analysis system according to claim 8,
The recovery device recovers the radiation detector to the moving device using a signal cable for connecting the radiation detector and the dosimeter or a pull-back cable provided in the radiation detector. Radioactivity distribution analysis system. The radioactivity distribution analysis system according to claim 1,
The analysis section analyzes the dose rate distribution using a plurality of exponential functions and analyzes two or more major nuclides from two or more decay rates. The radioactivity distribution analysis system according to claim 1,
Further comprising a second database that stores the relationship between the shape of the radioactivity distribution and the dose rate distribution,
The said analysis part analyzes the said radioactivity distribution using also the relationship between the shape of the said radioactivity distribution stored in the said 2nd database, and the said dose rate distribution, The radioactivity distribution analysis system characterized by the above-mentioned. A method for analyzing a radioactivity distribution in a radioactive material handling facility,
A measurement step of measuring a γ-ray dose rate by a radiation detector,
This measurement step is performed by changing the position of the radiation detector, a dose rate distribution calculation step of calculating a dose rate distribution,
Calculating the attenuation rate of the calculated dose rate distribution, a main nuclide analysis step of analyzing the main nuclide in the radioactivity distribution using the calculated attenuation rate,
A distance analysis step of analyzing a distance between the radiation detector and the main nuclide using a waveform of the dose rate distribution, a three- dimensional position coordinate, and a trigonometric function;
Radioactivity distribution analysis in which the measurement process to the distance analysis process are performed a plurality of times, and the radioactivity distribution is analyzed using a plurality of dose rate distribution measurement results, the distance, the main nuclides, and the three-dimensional position coordinates. A method for analyzing the distribution of radioactivity, comprising:

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