Radioactive strontium measuring device, radioactive strontium measuring method, and program

Abstract

To provide a radioactive strontium measurement device, a radioactive strontium measurement method, and a program each of which enables reduction of error of detection of amount of Sr-89 included in a sample, thereby enabling reduction of the lower limit of detection thereof.SOLUTION: A radioactive strontium measurement device comprises: a measurement unit which counts the number of β rays emitted from a sample including Sr-90, Y-90 and Sr-89 being radioactive materials, and measures the spectrum of the β rays; and a calculation unit which calculates the number of radioactive rays from the sample on the basis of an output value of the measurement unit, performs spectrum analysis on β ray and separately calculate, on the basis of the analysis result, the amount of radioactivity of Sr-90 in the sample, calculates the amount of radioactivity of Y-90 on the basis of the calculation result, calculates a first number of β rays emitted from Sr-90 and Y-90 in the sample, calculates a second number of Sr-89 by subtracting the first number from the number of radioactive rays from the sample, and calculates, on the basis of the second number, the amount of radioactivity of Sr-89 included in the sample.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a radioactive strontium measuring device, a radioactive strontium measuring method, and a program that can accurately measure the radioactivity of strontium-89, which is a type of radioactive strontium. [Background technology]

[0002] At nuclear power plants and other nuclear facilities, various radioactive materials (waste, treated water, etc.) are discharged. These radioactive materials are managed according to the prescribed standards according to the radioactivity of the nuclide. Radioactive materials include, for example, radioactive strontium (Sr) such as strontium-90 (hereinafter referred to as Sr-90) derived from spent fuel, its radioisotope strontium-89 (hereinafter referred to as Sr-89), and yttrium-90 (hereinafter referred to as Y-90) generated by the decay of Sr-90, and it may be necessary to measure the radioactivity of each radioactive nuclide individually. Sr-90 has a half-life of about 29 years, while Sr-89 has a half-life of about 51 days.

[0003] The radioactivity of radioactive strontium is obtained by measuring the beta rays emitted from the sample. However, the measured value of this beta ray includes the radioactivity of Sr-89, Sr-90, and Y-90. Conventionally, the following methods have been proposed to individually measure the radioactivity of radioactive Sr, including Sr-90 and Sr-89.

[0004] For example, Non-Patent Document 1 proposes a method of measuring the radioactivity of the strontium fraction and the radioactivity of Y-90 separated from the fraction by milking using a GM counter or the like, determining the radioactivity of Sr-90 from the measured amount, and determining the radioactivity of Sr-89 by subtracting it from the radioactivity of the strontium fraction. According to this method, it is necessary to wait for Y-90 to be produced from Sr-90 in the strontium fraction and for it to reach a state of radioactive equilibrium, and it takes about three weeks from the occurrence of nuclear fission to the end of measurement in order to obtain a measured value.

[0005] Also, Non-Patent Document 2 proposes a method of measuring the radioactivity of a separated strontium fraction at two different times using a GM counter or the like, and calculating the radioactivity amounts of Sr-89 and Sr-90 from the decay or increase. According to this method, it is necessary to wait for a change in the decay curve due to the production of Y-90 from Sr-90 in the strontium fraction, and it takes about one week from the occurrence of nuclear fission to obtain a measured value.

[0006] In addition, Non-Patent Document 3 proposes a method of measuring the radioactivity of Sr-89 and Sr-90 directly by beta-ray spectrometry, a beta-ray spectrum analysis method, using a device capable of measuring the spectrum of beta rays, and then calculating the radioactivity of each by using the least squares method based on the measured values. With this method, it is possible to obtain the measured values ​​in about two days after the occurrence of nuclear fission. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Guidelines for the measurement of radioactive materials discharged from light water nuclear power reactor facilities (Nuclear Safety Commission, partially revised on March 29, 2001) [Non-Patent Document 2] Radioactive Strontium Analysis Method (Ministry of Education, Culture, Sports, Science and Technology, revised in 2003) [Non-Patent Document 3] Rapid determination of 89Sr and 90Sr in radioactive waste using Sr extraction disk and beta-ray spectrometer, JAEA Y. Kameo et al. Summary of the Invention [Problem to be solved by the invention]

[0008] When it is necessary to obtain the Sr radioactivity measurement results within a few days, the most effective method among the above methods is the measurement using β-ray spectrometry described in Non-Patent Document 3. However, with this method, when the amount of Sr-89 is, for example, about 1 / 5 (Sr-89 / Sr-90≦0.2) or less compared to the amount of Sr-90, the concentration error (2σ) of Sr-89 may become almost as large as the concentration of Sr-89, and the lower detection limit may become larger than that of Sr-90.

[0009] Therefore, while the amount of radioactivity of Sr-90 can be determined in a short period of time using beta ray spectrometry, there is a problem that the measurement of the amount of radioactivity of Sr-89 has a large error. Therefore, there is a need for a method of measuring radioactive strontium that is less affected by the amount of coexisting Sr-90 when it comes to the amount of radioactivity of Sr-89.

[0010] The present invention aims to provide a radioactive strontium measuring device, a radioactive strontium measuring method, and a program that, when measuring the amount of radioactive Sr contained in a sample, can reduce error in the amount of Sr-89 and lower the detection limit even when the amount of Sr-89 is lower than that of Sr-90. [Means for solving the problem]

[0011] One aspect of the present invention is a method for producing a radioactive material containing Sr-90, Y-90, and Sr-89. The Y-90 has been removed by a scavenging process. A measuring unit that measures the count of beta rays emitted from a sample and the spectrum of the beta rays, calculates the count of the sample based on the output value of the measuring unit, performs spectrum analysis of the beta rays, and individually calculates the amount of radioactivity of Sr-90 in the sample based on the analysis result, and and the time elapsed since the scavenging operation. a calculation unit that calculates the amount of radioactivity of the Y-90 based on a count of the Sr-90 in the sample and beta rays emitted from the Y-90, calculates a first count of Sr-90 in the sample and beta rays emitted from the Y-90, calculates a second count of the Sr-89 by subtracting the first count from the count of the sample, and calculates the amount of radioactivity of the Sr-89 contained in the sample based on the second count.

[0012] According to the present invention, the radioactivity of Sr-89 is calculated based on the calculated radioactivity of Sr-90, so that even if the amount of Sr-89 is lower than that of Sr-90, the error in the amount of Sr-89 can be reduced and the detection limit can be made smaller.

[0013] In another aspect of the present invention, the measurement unit has a GM counter tube capable of counting beta rays emitted from the sample, and the measurement unit includes a scintillator that emits light in response to the beta rays, and a photomultiplier tube that outputs an output value based on the emission of the scintillator, and the calculation unit calculates the count of the sample based on the output value of the GM counter tube and the output value from the photomultiplier tube, and performs the spectral analysis based on the output value from the photomultiplier tube.

[0014] According to the present invention, since it can be applied to existing coincidence type measuring devices, it is possible to reduce the cost of introducing the device.

[0015] In another aspect of the present invention, the measurement unit includes a first scintillator that emits light in response to the beta rays, a second scintillator that emits light in response to the beta rays, and a photomultiplier tube that outputs an output value based on the emission of the first scintillator and the second scintillator, and the calculation unit may calculate the count of the sample based on the output value of the photomultiplier tube and perform the spectral analysis.

[0016] According to the present invention, since it can be applied to existing anti-coincidence type measurement devices, it is possible to reduce the cost of introducing the device.

[0017] In one aspect of the present invention, the sample may be subjected to a scavenging operation in advance to remove the Y-90.

[0018] According to the present invention, the time required to accurately calculate the radioactivity of Sr-89 can be approximately simultaneous with the time required to calculate Sr-90 by β-ray spectrometry.

[0019] The amount of radioactivity of the Y-90 may be calculated based on the amount of radioactivity of the Y-90 and the time elapsed since the scavenging operation.

[0020] According to the present invention, the radioactivity of Y-90 can be calculated as a function of Sr-90.

[0021] Contains the radioactive materials Sr-90, Y-90, and Sr-89 The Y-90 has been removed by a scavenging process. The count of beta rays emitted from a sample and the spectrum of the beta rays are measured, the count of the sample is calculated based on the measurement of the beta rays, the spectrum of the beta rays is analyzed based on the measurement of the beta rays, and the amount of radioactivity of Sr-90 in the sample is calculated individually based on the analysis result, and the calculation result and the time elapsed since the scavenging operation. a first count of Sr-90 in the sample and beta rays emitted from the Y-90, a second count of Sr-89 by subtracting the first count from the count of the sample, and a second count of Sr-89 contained in the sample based on the second count, wherein a computer executes a process of calculating the radioactivity of the Sr-89 contained in the sample.

[0022] According to the present invention, the radioactivity of Sr-89 is calculated based on the calculated radioactivity of Sr-90, so that even if the amount of Sr-89 is lower than that of Sr-90, the error in the amount of Sr-89 can be reduced and the detection limit can be made smaller.

[0023] One aspect of the present invention is a method for producing a radioactive material containing Sr-90, Y-90, and Sr-89. The Y-90 has been removed by a scavenging process. Measure the count of beta rays emitted from a sample and the spectrum of the beta rays, calculate the count of the sample based on the measurement of the beta rays, analyze the spectrum of the beta rays based on the measurement of the beta rays, and calculate the amount of radioactivity of Sr-90 in the sample individually based on the analysis result, and and the time elapsed since the scavenging operation.the program causing a computer to execute the processes of: calculating the amount of radioactivity of the Y-90 based on a count of the Sr-90 in the sample and the beta rays emitted from the Y-90; calculating a first count of the Sr-90 in the sample and the beta rays emitted from the Y-90 by subtracting the first count from the count of the sample; and calculating the amount of radioactivity of the Sr-89 contained in the sample based on the second count.

[0024] According to the present invention, since the radioactivity of Sr-89 is calculated based on the calculated radioactivity of Sr-90, even if the amount of Sr-89 is lower than that of Sr-90, it is possible to realize a program that reduces the error in the amount of Sr-89 and lowers the detection limit. Effect of the Invention

[0025] According to the present invention, when measuring the amount of radioactive Sr contained in a sample, even if the amount of Sr-89 is lower than Sr-90 (for example, Sr-89 / Sr-90≦0.2), the error in the amount of Sr-89 can be reduced and the detection limit can be made smaller. [Brief description of the drawings]

[0026] [Figure 1] 1 is a block diagram showing a configuration of a radioactive strontium measuring device according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram showing the configuration of a coincidence type radioactive strontium measuring device. [Diagram 3] FIG. 1 is a diagram showing the configuration of an anti-coincidence type radioactive strontium measuring device. [Figure 4] FIG. 2 is a diagram showing the energy spectrum of β rays emitted from a sample. [Diagram 5] FIG. 1 is a diagram showing a conventional spectrum analysis process. [Figure 6] 1 is a flowchart showing the process of a conventional method for measuring radioactive strontium. [Figure 7] 1 is a flowchart showing the process of a radioactive strontium measuring method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, a radioactive strontium measuring device, a radioactive strontium measuring method, and a program according to an embodiment of the present invention will be described with reference to the drawings.

[0028] The radioactive strontium measuring device according to the embodiment of the present invention measures radiation emitted from a sample from which strontium is isolated, and calculates the amount of radioactivity for each nuclide contained in the sample based on the measurement results. In particular, the amount of radioactivity of Sr-89 is accurately calculated. A general radiation measuring device can be used to measure β rays emitted from the sample. The schematic configuration of the radioactive strontium measuring device will be described below.

[0029] As shown in Fig. 1, the radioactive strontium measuring device 1 includes, for example, a measuring unit 2 that measures β-rays from a sample S, and a computing device 10 connected to the measuring unit 2. The sample S is strontium (Sr), a radioactive nuclide that undergoes β-decay. The sample S is, for example, collected from spent nuclear fuel, and then Sr is isolated. The sample S is further subjected to a scavenging operation from the isolated Sr, and yttrium-90 (Y-90) is removed.

[0030] In sample S, after the scavenging operation, Sr-90 undergoes beta decay over time to produce Y-90. Therefore, sample S contains radioactive Sr-90 and the radioisotopes Sr-89 and Y-90. Sr-90, Y-90, and Sr-89 in sample S each emit beta rays.

[0031] The measurement unit 2, for example, individually calculates the amount of radioactivity of each nuclide contained in the sample S. The measurement unit 2 is composed of general measuring equipment as described below. The measurement unit 2 outputs a first output value related to the count of β rays emitted from the sample S and a second output value related to the energy spectrum of the β rays. The first output value and the second output value output by the measurement unit 2 are set in a data format according to the type of the measurement unit 2.

[0032] The calculation device 10 includes, for example, a calculation unit 12 that performs a predetermined calculation based on the output value output from the measurement unit 2, a memory unit 14 that stores data necessary for the calculation, and a display unit 16 that outputs the calculation results.

[0033] The calculation unit 12 calculates the count of β rays emitted from the sample S based on the output value output from the measurement unit 2, and also performs spectrum analysis. As described below, the calculation unit 12 calculates the amount of radioactivity of Sr-89 contained in the sample S based on the count of β rays emitted from the sample S and the results of the spectrum analysis.

[0034] The calculation unit 12 is realized, for example, by a processor such as a CPU executing a program (software) stored in the storage unit 14. In addition, some or all of the functions of these components may be realized by hardware (including circuitry) such as an LSI, ASIC, FPGA, or GPU, or may be realized by a combination of software and hardware. The program may be stored in a storage device such as an HDD or flash memory in advance, or may be stored in a removable storage medium such as a DVD or CD-ROM, and installed by mounting the storage medium in a drive device. The details of the calculation process of the calculation unit 12 will be described later.

[0035] The storage unit 14 stores programs and various data necessary for the calculations of the calculation unit 12. The storage unit 14 is realized by a storage medium such as a RAM, a ROM, a HDD, or a flash memory.

[0036] The display unit 16 is a display device to which the calculation results of the calculation unit 12 are output. The display unit 16 is a display device such as a liquid crystal display, an organic EL display, etc. The display unit 16 may be configured separately from a personal computer, a tablet terminal, a smartphone, etc.

[0037] Next, we will explain the specific configuration of the radioactive strontium measuring device 1. The radioactive strontium measuring device 1 is composed of a measuring section 2 that uses a general radiation measuring device.

[0038] 2 shows a schematic configuration of a coincidence-type radioactive strontium measuring device 1. The radioactive strontium measuring device 1 includes a measuring unit 2 that measures β-rays emitted from a sample S, and a calculation device 10 that calculates the amount of radioactivity of each nuclide contained in the sample S based on the measured value.

[0039] The measurement unit 2 is covered by a radiation-shielding housing 2A made of lead or the like. A measurement chamber 3 in which a sample S is placed is provided inside the measurement unit 2. A GM counter 4 is disposed above the measurement chamber 3. A scintillator 5 is disposed above the GM counter 4. A photomultiplier tube 6 is disposed above the scintillator 5.

[0040] The GM counter 4 counts the number of beta rays emitted from the sample S when they are input. When the GM counter 4 counts the number of rays, it outputs an output value. The scintillator 5 is, for example, a plastic scintillator made of an organic material such as plastic. The scintillator 5 is excited by the beta rays that are emitted from the sample S and pass through the GM counter 4, and emits light. The photomultiplier tube 6 detects the pulse height level of the light emitted from the scintillator 5. The photomultiplier tube 6 outputs a detection value based on the light emitted from the scintillator 5.

[0041] The calculation unit 12 calculates the number of coincidences by counting the number of times when the output value of the count counted in the GM counter 4 and the count output of the detection value of the light emission detected in the photomultiplier tube 6 are simultaneous. This makes it possible to eliminate the number of counts due to cosmic radiation and natural radiation. This number of coincidences is the number of counts of the sample S. The number of counts of the sample S includes the number of counts of multiple β rays emitted from multiple nuclides emitted from the sample S.

[0042] The calculation unit 12 also calculates the energy spectrum of β rays emitted from the sample S based on a detection value based on the pulse height level of the light emission detected by the photomultiplier tube 6 by β ray spectrometry.

[0043] 3 shows a schematic configuration of an anti-coincidence type radioactive strontium measuring device 1. The radioactive strontium measuring device 1 includes a measuring unit 2 that measures β-rays emitted from a sample S, and a calculation device 10 that calculates the amount of radioactivity of each nuclide contained in the sample S based on the measured value.

[0044] In the measurement unit 2, for example, the internal measurement chamber 3 is covered with an active shield 2B that shields radiation such as lead. The active shield 2B reduces background radiation such as cosmic radiation and natural radiation. A first scintillator 5A is disposed above the measurement chamber 3. A second scintillator 5B is disposed above the first scintillator. A photomultiplier tube 6 is disposed above the second scintillator 5B. The first scintillator 5A and the second scintillator 5B are plastic scintillators. The thickness of the second scintillator 5B in the vertical direction is formed to be thicker than the thickness of the first scintillator 5A in the vertical direction.

[0045] When cosmic radiation or natural radiation is detected, the active shield 2B outputs a detection value. The first scintillator 5A is excited by β rays emitted from the sample S and transmitted through the GM counter 4, and emits light. The second scintillator 5B is excited by β rays emitted from the sample S and transmitted through the first scintillator 5A, and emits light. The photomultiplier tube 6 detects the pulse height level of the light emitted from the first scintillator 5A and the second scintillator 5B. The photomultiplier tube 6 outputs a detection value based on the light emitted from the first scintillator 5A and the second scintillator 5B.

[0046] The calculation unit 12 counts the number of detection values ​​of light emission caused by the difference in wavelength of the spectra from the first scintillator 5A and the second scintillator 5B detected in the photomultiplier tube 6, and calculates the number of β rays emitted from the sample S. When the detection by the active shield 2B and the detection by the photomultiplier tube 6 are simultaneous, the calculation unit 12 regards this as anti-coincidence counting and does not count the number.

[0047] This makes it possible to eliminate counts due to cosmic radiation and natural radiation. The calculation unit 12 also calculates the energy spectrum of β rays emitted from the sample S by β ray spectrometry, based on the detection value based on the wave height level of the light emission detected by the photomultiplier tube 6.

[0048] Next, a method for measuring radioactive strontium in the radioactive strontium measuring device 1 will be described.

[0049] As shown in Figure 4, the energy spectrum of beta rays emitted from sample S is the sum of beta rays emitted from multiple nuclides Sr-90, Sr-89, and Y-90.

[0050] As shown in FIG. 5, in the radioactive strontium measurement method implemented in the conventional radioactive strontium measurement device, the β-ray spectrum is divided into five fractions, and the contributions of the three nuclides in each fraction are calculated by the least squares method based on the following formula (1).

number

number

[0051] FIG. 6 shows the process flow of a conventional radioactive strontium measurement method. The beta ray count of sample S is measured (step S100). Beta ray spectrometry is performed to analyze the energy spectrum of beta rays (step S102). The radioactivity amounts of Sr-89, Sr-90, and Y-90 contained in sample S are individually calculated using the least squares method (step S104). According to this method, when the amount of Sr-89 is, for example, about 1 / 5 or less of the amount of Sr-90 as described above, the detection limit may be higher than that of Sr-90.

[0052] 7 shows a process flow of the radioactive strontium measurement method of the embodiment. In the radioactive strontium measurement device 1, the sample S from which Y-90 has been removed after the scavenging operation is set in the measurement chamber 3 of the measurement unit 2. The measurement unit 2 measures β-rays emitted from the sample S containing the radioactive substances Sr-90, Y-90, and Sr-89 (step S200). The calculation unit 12 calculates the count of the sample S based on the output value of the measurement unit 2 (step S202).

[0053] At this time, in the case of a coincidence type radioactive strontium measuring device 1 (see FIG. 2), the output value of the counting of the sample S measured in the GM counter 4 is acquired by the calculation device 10 and taken in as counting data. In the coincidence type radioactive strontium measuring device 1, coincidence counting in which the influence of the background when the outputs of the GM counter 4 and the photomultiplier tube 6 are simultaneous is used as the counting of the sample S.

[0054] In the case of an anti-coincidence type radioactive strontium counter 1 (see FIG. 3), the count of the sample S is calculated in a calculation device 10 by utilizing the difference in wavelength of the β-ray spectrum between the first scintillator 5A and the second scintillator 5B based on the output value of the photomultiplier tube 6. In the anti-coincidence type radioactive strontium counter 1, the number of outputs from the photomultiplier tube 6 with reduced background effects is used as the count, without counting anti-coincidence counts when detection by the active shield 2B and detection by the photomultiplier tube 6 occur simultaneously.

[0055] The calculation unit 12 performs spectrum analysis of the energy of β rays based on the output value of the measurement unit 2 (step S204). At this time, in the coincidence type radioactive strontium measurement device 1, the calculation unit 12 calculates the energy spectrum of β rays based on the output value of the photomultiplier tube 6 that detects the emission of the scintillator 5. In the anti-coincidence type radioactive strontium measurement device 1, the calculation unit 12 calculates the energy spectrum of β rays based on the output value of the photomultiplier tube 6 that detects the emission of the first scintillator 5A and the second scintillator 5B.

[0056] The calculation unit 12 individually calculates the amount of radioactivity (concentration) of Sr-90 in the sample S based on the analysis result (step S206). At this time, the calculation unit 12 analyzes the spectrum of β-ray energy by least squares approximation based on the output value of the pulse height level output from the photomultiplier tube 6, resolves it into a single spectrum of Sr-90, and then calculates the amount of radioactivity of Sr-90 alone.

[0057] The calculation unit 12 calculates the radioactivity of Y-90 as a function of Sr-90 based on the calculation result and the elapsed time after purification of the sample S (step S208). The calculation unit 12 converts the total value of the calculated radioactivity of Sr-90 alone and the radioactivity of Y-90 alone calculated as a function of Sr-90 into a first count, which is the total value of the counts of β rays emitted from Sr-90 and Y-90 in the sample S (step S210).

[0058] The calculation unit 12 calculates a second count of Sr-89 by subtracting the first count from the count of the sample S calculated in step S202 (step S212). The calculation unit 12 converts the second count into the amount of radioactivity of Sr-89 contained in the sample S and calculates it (step S214).

[0059] In the conventional coincidence type radioactive strontium measuring device 1, the measurement value of the GM counter 4 was used to calculate coincidence counts with reduced background effects. Also, in the anti-coincidence type radioactive strontium measuring device 1, counts excluding anti-coincidence counts calculated based on the output of the photomultiplier tube 6 were used to reduce background effects.

[0060] In contrast, with the radioactive strontium measuring device 1, the second count is calculated by subtracting the first count, which is the total count of Sr-90 and Y-90 calculated by spectrum analysis of the energy of beta rays, from the count excluding the calculated coincidence counts and anti-coincidence counts, and the radioactivity of Sr-89 can be accurately calculated based on the second count.

[0061] The above-mentioned radioactive strontium measuring device 1 can be realized by changing the calculation method without changing the configuration of a conventional coincidence type radioactive strontium measuring device or anti-coincidence type radioactive strontium measuring device. The radioactive strontium measuring device 1 can calculate the radioactivity of Sr-89 based on the calculated value of the radioactivity of Sr-90, regardless of the detection limit of Sr-89. The radioactive strontium measuring device 1 can calculate the radioactivity of Sr-89 in a short period of time after the scavenging operation.

[0062] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention as well as the invention and its equivalents as described in the claims. For example, in the above embodiments, a plastic scintillator is used as an example, but this is not limiting and a liquid scintillator may be used.

[0063] When measuring the amount of Sr radioactivity using a liquid scintillator, a similar process may be performed by first determining the beta ray count due to Sr radioactivity, performing beta ray spectrometry using the output value of a photomultiplier tube based on Cherenkov light, and then subtracting the Sr-90 count determined based on the calculated amount of Sr-90 radioactivity from the beta ray count. [Explanation of symbols]

[0064] 1. Radioactive strontium measuring device 2. Measurement section 2A housing 2B Active Shield 3. Measurement Room 4 GM counter 5. Scintillator 5A First Scintillator 5B Second scintillator 6 Photomultiplier tube 10 Arithmetic unit 12 Arithmetic section 14 Storage section 16 Display S sample

Claims

1. A measuring unit that measures the number of beta rays emitted from a sample that contains radioactive materials Sr-90, Y-90, and Sr-89 and that has been previously subjected to a scavenging operation to remove the Y-90, and measures the spectrum of the beta rays; a calculation unit which calculates the count of the sample based on the output value of the measurement unit, performs spectrum analysis of the beta rays, calculates the amount of radioactivity of Sr-90 in the sample individually based on the analysis result, calculates the amount of radioactivity of the Y-90 based on the calculation result and the elapsed time from the scavenging operation, calculates a first count of Sr-90 in the sample and beta rays emitted from the Y-90, calculates a second count of Sr-89 by subtracting the first count from the count of the sample, and calculates the amount of radioactivity of the Sr-89 contained in the sample based on the second count. Radioactive strontium measuring device.

2. the measurement unit has a GM counter capable of counting β rays emitted from the sample, The measurement unit includes a scintillator that emits light by the β rays, a photomultiplier tube that outputs an output value based on the light emitted by the scintillator; The calculation unit calculates a count of the sample based on an output value of the GM counter and an output value from the photomultiplier tube, performing the spectral analysis based on an output value from the photomultiplier tube; 2. The radioactive strontium measuring device according to claim 1.

3. the measurement unit includes a first scintillator that emits light in response to the β rays, a second scintillator that emits light in response to the β rays, and a photomultiplier tube that outputs an output value based on the light emitted by the first scintillator and the second scintillator, The calculation unit calculates the count of the sample based on the output value of the photomultiplier tube and performs the spectrum analysis.

2. The radioactive strontium measuring device according to claim 1.

4. Counting the number of beta rays emitted from a sample containing radioactive materials Sr-90, Y-90, and Sr-89, from which a scavenging operation has been performed in advance to remove the Y-90, and measuring the spectrum of the beta rays; Calculating the count of the sample based on the measurement of the beta rays; Analyzing a spectrum of the beta rays based on the measurement of the beta rays; The amount of radioactivity of Sr-90 in each sample is calculated based on the analysis results. Calculate the amount of radioactivity of the Y-90 based on the calculation result and the elapsed time from the scavenging operation; Calculate the first count of beta rays emitted from Sr-90 and the Y-90 in the sample; calculating a second count of Sr-89 by subtracting the first count from the count of the sample; A radioactive strontium measuring method, comprising: a computer executing a process of calculating the amount of radioactivity of the Sr-89 contained in the sample based on the second count.

5. Counting the number of beta rays emitted from a sample containing radioactive materials Sr-90, Y-90, and Sr-89, from which a scavenging operation has been performed in advance to remove the Y-90, and measuring the spectrum of the beta rays; Calculating the count of the sample based on the measurement of the beta rays; analyzing a spectrum of the beta rays based on the measurement of the beta rays; The amount of radioactivity of Sr-90 in each sample is calculated based on the analysis results. Calculating the amount of radioactivity of the Y-90 based on the calculation result and the elapsed time from the scavenging operation; Calculating the first count of beta rays emitted from Sr-90 and the Y-90 in the sample; calculating a second Sr-89 count by subtracting the first count from the sample count; A program that causes a computer to execute a process of calculating the amount of radioactivity of the Sr-89 contained in the sample based on the second count.

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