Radiation analysis apparatus and radiation analysis method

Abstract

This radioactivity analysis device (1) has: a radiation detection unit (10) that detects radiation emitted from a measurement subject (70), and outputs a first signal (D1) based on the radiation; a radiation type determination unit (20) that determines a radiation type indicating the type of radiation on the basis of the first signal (D1), and outputs a second signal (D2) that includes information indicating the radiation type; an inverse problem calculation algorithm selection unit (30) that, on the basis of the radiation type, selects an inverse problem calculation algorithm from a plurality of inverse problem calculation algorithms saved in advance in a storage device; and an inverse problem calculation unit (50) that uses the selected inverse problem calculation algorithm and a response function for the radiation detection unit (10) saved in advance in the storage device to execute an inverse problem calculation, thereby identifying the radiation nuclide included in the measurement subject (70) and calculating the intensity of the radioactivity of the radiation nuclide from the first signal (D1) and the second signal (D2).

Description

[Technical Field]

[0001] The present disclosure relates to a radioactivity analysis device and a radioactivity analysis method. [Background technology]

[0002] Generally, in radioactivity analysis, which analyzes the radioactivity of a measurement object, a radiation detector measures the energy distribution of the radiation emitted from the measurement object, and based on the measurement results, the radioactive nuclide, which is the radioactive substance contained in the measurement object, is identified and the radioactivity strength of the radionuclide [Bq (Becquerel)] is calculated.

[0003] Thus, in radioactivity analysis, an inverse problem calculation is used to observe the results and estimate the cause. For example, Non-Patent Document 1 describes unfolding, which is a mathematical technique for determining the energy spectrum of incident radiation using the response function of a radiation detector based on the output pulse-height distribution (i.e., pulse-height distribution) of a pulse signal output from the radiation detector. Patent Document 1 also describes a method for improving the accuracy of the estimation result by increasing the number of response functions used in the inverse problem calculation. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Nuclear Regulation Authority Monitoring Information, Radioactivity Measurement Method Series No. 17, "Environmental Gamma-Ray Measurement Method Using a Continuous Monitor," Nuclear Regulation Authority, revised December 2017 [Patent documents]

[0005] [Patent Document 1] Patent No. 5832404 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above radioactivity analysis method has a problem in that the accuracy of the radioactivity analysis is low when the measurement object contains radioactive nuclides that emit multiple types of radiation.

[0007] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a radioactivity analysis device and a radioactivity analysis method that achieve high accuracy in radioactivity analysis. [Means for solving the problem]

[0008] The radioactivity analysis device of the present disclosure is characterized by comprising: a radiation detection unit that detects radiation emitted from a measurement object and outputs a first signal based on the radiation; a radiation ray type determination unit that determines a radiation ray type indicating a type of the radiation based on the first signal and outputs a second signal including information indicating the radiation ray type; an inverse problem calculation algorithm selection unit that selects an inverse problem calculation algorithm based on the radiation ray type from a plurality of inverse problem calculation algorithms pre-stored in a storage device; and an inverse problem calculation unit that identifies radioactive nuclides contained in the measurement object from the first signal and the second signal and calculates the radioactivity of the radioactive nuclides by performing inverse problem calculation using the selected inverse problem calculation algorithm and a response function of the radiation detection unit pre-stored in a storage device.

[0009] The radioactivity analysis method of the present disclosure is a method executed by a computer, comprising the steps of: detecting radiation emitted from a measurement object and receiving a first signal from a radiation detection unit that detects radiation emitted from the measurement object and outputs a first signal based on the radiation; determining a radiation ray type indicating a type of the radiation based on the first signal and outputting a second signal including information indicating the radiation ray type; selecting an inverse problem calculation algorithm based on the radiation ray type from a plurality of inverse problem calculation algorithms pre-stored in a storage device; and performing an inverse problem calculation using the selected inverse problem calculation algorithm and a response function of the radiation detection unit pre-stored in a storage device, thereby identifying a radionuclide contained in the measurement object from the first signal and the second signal and calculating the radioactivity intensity of the radionuclide. [Effects of the Invention]

[0010] According to the radioactivity analysis device and radioactivity analysis method of the present disclosure, highly accurate radioactivity analysis can be performed. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a schematic configuration of a radioactivity analysis device according to a first embodiment. [Figure 2] 1 is a diagram showing the pulse height (ie, energy) distribution of a pulse signal output from a detector of a radiation detection unit for each radiation ray type indicating the type of radiation. [Figure 3] 1 is a diagram showing a hardware configuration of a radioactivity analyzer according to a first embodiment. [Figure 4] 1 is a flowchart showing a radioactivity analysis method according to the first embodiment. [Figure 5] FIG. 10 is a block diagram showing a schematic configuration of a radioactivity analyzer according to a second embodiment. [Figure 6] FIG. 10 is a block diagram schematically showing the configuration of a radioactivity analyzer according to a third embodiment. [Figure 7]4 is a diagram showing the rise and decay characteristics of the amplitude of a pulse signal output from a detector of the radiation detection unit for each type of radiation; FIG. [Figure 8] FIG. 10 is a block diagram schematically showing the configuration of a radioactivity analyzer according to a fourth embodiment. [Figure 9] 10(A) to 10(C) are schematic diagrams showing the trajectory shapes of the detectors of the radiation detection unit for each type of radiation. [Figure 10] FIG. 10 is a block diagram schematically showing the configuration of a radioactivity analyzer according to a fifth embodiment. [Figure 11] 10 is a diagram showing the relationship between the luminance value and the spread of the locus shape in the position detection detector of the radiation detection unit. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, radioactivity analysis devices and radioactivity analysis methods according to embodiments will be described with reference to the drawings. The following embodiments are merely examples, and the embodiments can be appropriately combined and modified.

[0013] 1. First embodiment <Radioactivity analyzer 1> 1 is a block diagram showing a schematic configuration of a radioactivity analysis apparatus 1 according to the first embodiment. The radioactivity analysis apparatus 1 includes a radiation detection unit 10 that detects radiation emitted from a measurement target (also referred to as a "measurement sample" or "object to be measured") 70 and outputs a first signal D1 based on the detected radiation, and an information processing unit 1a that identifies radioactive substances (also referred to as "radionuclides" or "nuclides") contained in the measurement target 70 and calculates the radioactivity strength [Bq (Becquerel)] of the radionuclide. The information processing unit 1a is, for example, a computer serving as an information processing device, and is capable of implementing the radioactivity analysis method according to the first embodiment.

[0014] The information processing unit 1a of the radioactivity analysis device 1 has a radiation ray type determination unit 20, an inverse problem calculation algorithm selection unit 30, and an inverse problem calculation unit 50. The inverse problem calculation algorithm selection unit 30 selects an inverse problem calculation algorithm from a plurality of inverse problem calculation algorithms (e.g., stored as an inverse problem calculation algorithm database 31) pre-stored in a storage device based on the radiation ray type indicated by the second signal D2. The inverse problem calculation unit 50 performs inverse problem calculation using the selected inverse problem calculation algorithm and a response function of the radiation detection unit 10 pre-stored in the storage device (e.g., stored as a response function database 41), thereby identifying the radioactive nuclides contained in the measurement target 70 from the first signal D1 and the second signal D2 and calculating the radioactivity strength [Bq (Becquerel)] of each of the radioactive nuclides. When the measurement target 70 contains multiple radioactive nuclides, the inverse problem calculation unit 50 can identify each of the multiple radioactive nuclides and calculate the radioactivity strength [Bq (Becquerel)] of each of the multiple radioactive nuclides. Furthermore, the inverse problem calculation unit 50 performs an inverse problem calculation to calculate the radiation intensity (for example, the radiation fluence (flux) [1 / (cm 2 ·s)]) may be calculated.

[0015] The calculated radioactivity is expressed as the radioactivity concentration [Bq / g] (or [Bq / cm 3 ]). Furthermore, the storage device in which the inverse problem calculation algorithm database (also referred to as "inverse problem calculation algorithm DB") 31 is stored and the storage device in which the response function database (also referred to as "response function DB") 41 is stored may be the same device or different devices. The storage device in which the inverse problem calculation algorithm DB 31 is stored and the storage device in which the response function DB 41 is stored may be part of the radioactivity analysis device 1, or may be part of another device (for example, a computer on a network) that can communicate with the radioactivity analysis device 1.

[0016] The radioactivity analysis device 1 is also connected to a display unit 60 as an information output device that presents the calculation results of the inverse problem calculation unit 50 to the user. However, the display unit 60 may be a part of the radioactivity analysis device 1. The display unit 60 is, for example, a display device such as a liquid crystal display that displays images. Instead of or in addition to the display unit 60, another information output device (for example, a printer) may be provided.

[0017] <Radiation detection unit 10> The radiation detection unit 10 has a detector 11 that detects radiation emitted from the object 70 to be measured, an amplifier 12 that amplifies the output pulse output from the detector 11, a waveform shaper 13 that shapes the output pulse output from the amplifier 12, and a pulse-height analysis unit 14 that generates a pulse-height distribution of the output pulse output from the waveform shaper 13.

[0018] First, the detector 11 will be described. The detector 11 has the function of outputting a signal intensity (e.g., pulse amplitude) corresponding to the energy imparted to the detector by radiation. Widely used detectors 11 include scintillation detectors that combine a scintillator crystal and a photomultiplier tube, scintillation detectors that combine a scintillator crystal and a semiconductor photodetector, semiconductor detectors, and gas detectors. An example of a semiconductor detector is a germanium semiconductor detector. A gas detector measures the number of electrons generated by collisions between charged particles (radiation particles) passing through a gas in a container and electrons in the gas molecules (i.e., a value proportional to the amount of energy loss of the charged particles). Gas detectors include Geiger-Muller (GM) counters and detectors using a gas-filled ionization chamber.

[0019] Next, the amplifier 12 will be described. The amplifier 12 is a circuit having a function of amplifying the amplitude of the output pulse, which is the signal output from the detector 11. The amplifier 12 is used to amplify the output pulse to a signal strength (for example, a sufficiently large pulse amplitude) sufficient for detection in the pulse-height analysis unit 14 and the radiation ray type determination unit 20 at the subsequent stage. If the output of the detector 11 is sufficiently large, there is no need to provide the amplifier 12.

[0020] Next, the waveform shaper 13 will be described. The waveform shaper 13 is a circuit that has the function of removing noise from the signal output from the amplifier 12 or the detector 11 and adjusting the amplification factor. When the waveform shaper 13 is formed by an analog circuit, it is generally configured by combining an integrating circuit and a differentiating circuit. The waveform shaper 13 removes noise and adjusts the amplification factor, and shapes the output pulse into a waveform that makes it easy to detect the pulse height in the pulse height analysis unit 14. When the waveform shaper 13 is formed by a digital circuit, it digitally converts the signal output from the previous stage by analog-to-digital conversion, removes noise and adjusts the amplification factor using a digital filter, and processes the waveform-shaped digital pulse.

[0021] Next, the pulse-height analysis unit 14 will be described. The pulse-height analysis unit 14 creates a frequency distribution of the peak values ​​of the output pulses output from the waveform shaper 13 or a frequency distribution of the time widths of the output pulses. When the waveform shaper 13 performs the analog circuit processing described above, the pulse-height analysis unit 14 acquires the pulse heights of the output pulses by combining a circuit that holds the peak values ​​of the output pulses with analog-to-digital conversion, or by combining a circuit that converts the rise and fall times of the output pulses into voltages with analog-to-digital conversion. When the waveform shaper 13 performs the digital circuit processing described above, the pulse-height analysis unit 14 acquires the pulse heights of the output pulses from the amplitude or time width of the output pulses processed by a digital filter. The pulse-height analysis unit 14 creates a frequency distribution from the acquired pulse heights of the output pulses.

[0022] FIG. 2 is a diagram showing the pulse height (i.e., energy) distribution of the pulse signal output from the radiation detection unit 10 for each type of radiation. As shown in FIG. 2, the measured pulse height distribution may be converted into an energy distribution. There is a one-to-one correspondence between the pulse height distribution and the energy distribution. For example, the type of radiation is one or more of α rays, β rays, and γ rays.

[0023] <Radiation line type determination section 20> Next, we will explain the radiation ray type determination unit 20. The radiation ray type determination unit 20 has a function of detecting the type of radiation (i.e., the radiation ray type) emitted from the measurement object 70 from the pulse-height distribution or energy distribution obtained by the pulse-height analysis unit 14.

[0024] As shown in FIG. 2, alpha rays (α rays) detected by the radiation detection unit 10 are generally emitted from α-ray emitting nuclides and have an energy of 4 MeV or more. For example, plutonium 238 ( 238 Pu) emits alpha rays with an energy of 5.50 MeV and alpha rays with an energy of 5.46 MeV. 239 Pu) emits alpha rays with an energy of 5.16 MeV. Americium-241 ( 241 Am) emits alpha rays with an energy of 5.49 MeV. 244 Cm) emits alpha rays with an energy of 5.95 MeV. Alpha rays with high energy (generally, energy of 4 MeV or more) are detected by detector 11 so that a pulse-height distribution is formed in the high-energy region, as shown by the solid line in Figure 2. The energy of alpha rays emitted from the measurement object 70 has an asymmetric peak structure due to energy loss in the air, and is characterized by the peak structure appearing on the pulse-height distribution. By detecting the presence or absence of this peak structure, the radiation type determination unit 20 can determine whether or not the measurement object 70 contains an alpha-ray-emitting nuclide.

[0025] As shown by the dotted line in Figure 2, gamma rays (γ rays) emitted from radioactive nuclides generally have energy specific to the nuclide, and the pulse-height distribution of γ rays has a peak structure with a shape similar to a normal distribution and a continuous component that reflects the process of losing energy due to scattering inside or around the detector 11. The energy of γ rays from general radioactive nuclides is 3 MeV or less, which is lower than the peak in the pulse-height distribution of α rays. For example, thallium (Tl) emits γ rays with an energy of 2.6 MeV. Yttrium (Y) emits γ rays with an energy of 1.8 MeV. Cobalt 60 ( 60 Co) emits two gamma rays with energies of 1.3 MeV and 1.1 MeV. The energy of gamma rays emitted from gamma-ray-emitting nuclides is lower than the energy of alpha rays emitted from alpha-ray-emitting nuclides, and the shape of the peak structure is also different (having a steep peak structure and a continuous component). Therefore, the radiation type determination unit 20 can determine whether or not the measurement object 70 contains gamma-ray-emitting nuclides from the pulse-height distribution.

[0026] Beta rays (β rays) emitted from radioactive nuclei are emitted during the process of beta decay, a type of radioactive decay of atomic nuclei. In beta decay, electrons (i.e., β rays) and antineutrinos are emitted. Because the electrons and antineutrinos share energy during beta decay, the pulse-height distribution of β rays, which represents the energy of the emitted electrons (i.e., β rays), is a continuous distribution, as shown by the dashed-dotted line in Figure 2. The pulse-height distribution of β rays, depending on the structure of the detector 11, has a peak structure in the low-energy region, but does not have a peak structure in a specific energy region like α rays and γ rays. The pulse-height distribution of β rays, like that of γ rays, is a continuous distribution in the low-energy region. Furthermore, in the low-energy region, the pulse-height distribution of β rays is larger than that of γ rays. Because the shape of the pulse-height distribution of β rays differs from that of other radiation types, the radiation type determination unit 20 can determine whether the measurement target 70 contains a β-ray-emitting nuclide from the pulse-height distribution.

[0027] The detection of the characteristics of each radiation ray type in the pulse-height distribution can be realized by, for example, a method of analytically detecting the above characteristics, a method of detecting by verifying the degree of coincidence with a pre-assumed pulse-height distribution, a method of determining the radiation ray type by machine learning of a pre-assumed pulse-height distribution, or a method of learning to determine the radiation ray type by unsupervised machine learning. The pre-assumed pulse-height distribution can be created by calculating pulse-height distributions under various conditions. The pulse-height distribution can be calculated, for example, by radiation behavior analysis.

[0028] The function of performing detection using the pulse-height distribution of the pulse-height analysis unit 14 may be performed by the radiation ray type determination unit 20. In this case, it is possible to not provide the pulse-height analysis unit 14.

[0029] In conventional techniques, it has been proposed to improve the accuracy of radioactivity analysis by adjusting the response function, as in Patent Document 1. The method of the first embodiment assumes that only one type of radiation is emitted from the measurement target 70, and does not take into consideration that the shape of the response function will change if multiple radiation ray types are included in the measurement target 70. As a result, when the response function changes, a single inverse problem calculation algorithm cannot correctly perform the inverse problem calculation under conditions in which multiple radiation ray types are measured, and therefore it is not possible to correctly measure the radiation intensity and radioactivity strength.

[0030] In embodiment 1, by determining the type of radiation output from detector 11 and selecting an inverse problem calculation algorithm to be used depending on the type of radiation detected, it is possible to determine the radioactivity intensity of each type of radiation even when the measurement object 70 contains multiple types of radiation.

[0031] The detection of the characteristics of each radiation ray type in the pulse-height distribution can be realized, for example, by a method of analytically detecting the above characteristics, a method of detecting by verifying the degree of coincidence with a pre-assumed pulse-height distribution, a method of determining the radiation ray type by machine learning of a pre-assumed pulse-height distribution, or a method of learning to determine the radiation ray type by unsupervised machine learning. The pre-assumed pulse-height distribution can be created by calculating pulse-height distributions under various conditions. The pulse-height distribution can be calculated, for example, by radiation behavior analysis.

[0032] <Inverse problem calculation section 50> Next, the inverse problem calculation unit 50 will be described. The inverse problem calculation unit 50 identifies the nuclides of the radioactive nuclides contained in the measurement target 70 from the pulse-height distribution and calculates the radioactivity strength [Bq] of the radioactive nuclides. Note that the radioactivity strength [Bq] may be expressed as radioactivity concentration. In general measurements, the measurement is performed under conditions where the nuclides, radioactivity strength [Bq], and radioactivity concentration of the radioactive nuclides contained in the measurement target 70 are known, and the measurement is performed to obtain the pulse-height distribution, which is considered a forward problem. In radioactivity analysis, since information about the measurement target 70 is unknown and only the measurement result, the pulse-height distribution, is known, it is necessary to solve an inverse problem, which is a reverse solution of the forward problem. To perform inverse problem calculation in radioactivity analysis, a response function that relates the pulse-height distribution to the radioactivity strength or radioactivity concentration of the measurement target 70 is generally used. The pulse-height distribution M(E) obtained by measuring the frequency of pulse height E can be calculated using the following equation (1).

[0033]

number

[0034] Here, R(E) is the response function, and S(E) is the radioactivity strength (or radioactivity concentration) for each energy of the measurement target 70. In this case, algorithms for performing the inverse problem calculation include, for example, inverse matrix calculation, pseudo-inverse matrix calculation, deconvolution, deconvolution integral, and successive approximation. The response function can be prepared by using, for example, a calculation that can reflect the physical process of radiation, such as radiation behavior analysis. Furthermore, instead of analytical calculations such as Equation (1), calculations can also be realized by using machine learning that is trained to estimate S(E) from M(E) based on combinations of M(E) and S(E) under various conditions. M(E) and S(E) can be generated using radiation behavior analysis, as described above.

[0035] As described above, instead of an analytical relationship such as equation (1), it is also possible to solve the inverse problem calculation from the relationship between S(E) and M(E) based on the known relationship between S(E) and M(E) and the network structure used in machine learning.

[0036] <Inverse problem calculation algorithm selection unit 30> Next, the inverse problem calculation algorithm selection unit 30 will be described. As described above, a plurality of inverse problem calculation algorithms capable of performing the inverse problem calculation are prepared in advance. There are cases where the calculation cannot find a solution due to the properties of the matrix that is the response function R(E). The response function R(E) differs depending on the type of radiation.

[0037] The response function R(E) of gamma rays is shown below as equation (2). The response function R(E) below is expressed as a matrix whose diagonal elements have values ​​greater than 0.

[0038]

number

[0039] The response function R(E) of alpha rays is shown below as equation (3). The response function R(E) below is expressed as a matrix with diagonal elements of 0.

[0040]

number

[0041] The response function for radiation types that do not experience continuous energy attenuation in air, such as gamma rays, is a matrix with diagonal components (i.e., the diagonal components are not 0), as shown in equation (2). When performing inverse problem calculations for radiation types with such response functions, analytical calculation algorithms such as inverse matrix calculations, pseudo-inverse matrix calculations, or successive approximation methods can be used.

[0042] The response function for radiation types that decay in air, such as alpha rays, is a matrix without diagonal components, as shown in equation (3). For example, when a response function is expressed as a matrix without diagonal components, an inverse matrix operation cannot be used because an inverse matrix does not exist. Furthermore, pseudo-inverse matrix operations can have problems with calculation accuracy, such as the existence of solutions that are less than 0.

[0043] When performing inverse problem calculations for beta rays, a response function can be created using an estimated spectrum from the assumed radioactive nuclide. In this case, the response function is not a square matrix, and since an inverse matrix does not exist, inverse problem calculations using a machine learning network may be able to estimate more optimal results than analytical inverse problem calculations. The inverse problem calculation algorithm selection unit 30 optimally selects one or more calculation algorithms depending on the detected radiation ray type so as to converge the solution or increase the calculation speed based on the detected radiation ray type.

[0044] The inverse problem calculation algorithm DB 31 stores a plurality of calculation algorithms that can be used in the inverse problem calculation unit 50 as described above.

[0045] Response Function Database 41 Next, the response function database 41 will be described. The response function database 41 has parameters of a response matrix or a machine learning network structure used in the inverse problem calculation. When the inverse problem calculation is performed analytically, matrices such as those shown in formulas (2) and (3) are stored. The response function database 41 may also have information about a network for performing the inverse problem calculation using machine learning, which is a method other than analytical calculation.

[0046] <Display section 60> The radionuclide, radioactivity [Bq], radiation intensity, and radioactivity concentration contained in the measurement object 70 derived by the inverse problem calculation are displayed on the display unit 60.

[0047] FIG. 3 is a diagram showing an example of the hardware configuration of the radioactivity analysis apparatus 1 according to the first embodiment. The hardware configuration of FIG. 3 is also applied to the radioactivity analysis apparatuses according to the second to fifth embodiments. As shown in FIG. 3, the radioactivity analysis apparatus 1 has a radiation detection unit 10 and an information processing unit 1a. The information processing unit 1a has a processor 101 such as a CPU (Central Processing Unit), a memory 102 which is a volatile storage device, and a non-volatile storage device 103 such as a hard disk drive (HDD) or a solid state drive (SSD). The memory 102 is, for example, a semiconductor memory such as a RAM (Random Access Memory). The storage device 103 may store the database shown in FIG. 1.

[0048] Each function of the information processing unit 1a is realized by, for example, a processing circuit. The processing circuit may be dedicated hardware, or may be a processor 101 that executes a program stored in a memory 102. The processor 101 may be any of a processing device, an arithmetic device, a microprocessor, a microcomputer, and a DSP (Digital Signal Processor).

[0049] When the processing circuitry is dedicated hardware, the processing circuitry may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or any combination thereof.

[0050] When the processing circuit is the processor 101, the radioactivity analysis program executed by the information processing unit 1a is realized by software, firmware, or a combination of software and firmware. The radioactivity analysis program is installed in the information processing unit 1a via a network or from a recording medium. The software and firmware are written as programs and stored in the memory 102. The processor 101 can realize the functions of each unit shown in FIG. 1 by reading and executing the display control program stored in the memory 102.

[0051] The information processing unit 1a may be partially implemented by dedicated hardware and partially implemented by software or firmware. In this way, the processing circuit can realize each of the above-mentioned functions by hardware, software, firmware, or any combination of these.

[0052] 4 is a flowchart showing a radioactivity analysis method according to the first embodiment. This radioactivity analysis method is executed by a computer serving as an information processing unit 1a. This radioactivity analysis method includes the steps of: receiving a first signal D1 from a radiation detection unit 10 that detects radiation emitted from a measurement target 70 and outputs a first signal D1 based on the radiation; determining a radiation ray type based on the first signal and outputting a second signal D2 containing information indicating the radiation ray type; selecting an inverse problem calculation algorithm from a plurality of inverse problem calculation algorithms pre-stored in a storage device based on the radiation ray type; and performing an inverse problem calculation using the selected inverse problem calculation algorithm and a response function of the radiation detection unit 10 pre-stored in a storage device, thereby identifying a radionuclide contained in the measurement target 70 from the first signal D1 and the second signal D2 and calculating the radioactivity intensity of the radionuclide. Furthermore, in step S4, the radiation intensity (e.g., radiation fluence) may also be calculated.

[0053] <effect> As described above, according to the radioactivity analysis device 1 and the radioactivity analysis method of embodiment 1, the accuracy of the inverse problem calculation can be improved by selecting and using an appropriate inverse problem calculation algorithm from a plurality of inverse problem calculation algorithms.

[0054] 2. Second Embodiment Fig. 5 is a block diagram showing a schematic configuration of a radioactivity analysis apparatus 2 according to embodiment 2. In Fig. 5, components that are the same as or correspond to those shown in Fig. 1 are assigned the same reference numerals as those shown in Fig. 1. The radioactivity analysis apparatus 2 according to embodiment 2 differs from the radioactivity analysis apparatus 1 according to embodiment 1 in that an information processing unit 2a includes a response function selection unit 40.

[0055] The radioactivity analysis device 2 has a radiation detection unit 10 that detects radiation emitted from the measurement object 70 and outputs a first signal D1 based on the detected radiation, and an information processing unit 2a that identifies radionuclides that indicate radioactive substances contained in the measurement object 70 and calculates the radioactivity strength [Bq] of the radionuclides. The information processing unit 2a is, for example, a computer, and is capable of implementing the radioactivity analysis method according to the second embodiment.

[0056] In the second embodiment, a plurality of response functions are stored in advance as a response function DB 41 in a storage device (for example, the storage device 103 in FIG. 3 ). The response function selection unit 40 selects a response function to be used from the plurality of response functions stored in the response function DB 41 based on the second signal D2 indicating the radiation ray type determined by the radiation ray type determination unit 20. The inverse problem calculation unit 50 performs an inverse problem calculation using the inverse problem calculation algorithm selected by the inverse problem calculation algorithm selection unit 30 and the response function selected by the response function selection unit 40, thereby identifying the radionuclides contained in the measurement target 70 from the first signal D1 and the second signal D2 and calculating the radioactivity strength [Bq] of the radionuclides. The inverse problem calculation unit 50 may also perform an inverse problem calculation to calculate the radiation strength from the first signal D1 and the second signal D2.

[0057] As described above, according to the radioactivity analysis device 2 and the radioactivity analysis method of the second embodiment, an appropriate inverse problem calculation algorithm is selected from a plurality of inverse problem calculation algorithms, an appropriate response function is selected from a plurality of response functions, and by using these, the accuracy of the inverse problem calculation can be improved.

[0058] Other than the above, the second embodiment is the same as the first embodiment.

[0059] 3. Third Embodiment Fig. 6 is a block diagram showing a schematic configuration of a radioactivity analyzing apparatus 3 according to embodiment 3. In Fig. 6, components that are the same as or correspond to those shown in Fig. 1 are assigned the same reference numerals as those shown in Fig. 1. The radioactivity analyzing apparatus 3 according to embodiment 3 differs from the radioactivity analyzing apparatus 1 according to embodiment 1 in that the radiation detecting unit 10b includes a waveform discriminator 15 that discriminates detection signals for each type of radiation detected by the detector 11 and outputs a discrimination signal. The waveform discriminator 15 is a circuit that causes the pulse shapes of the output of the detector 11 and the output signal output from the amplifier 12 to differ depending on the type of radiation.

[0060] The radiation ray type determination unit 20b determines the radiation ray type based on the first signal D1 including the discrimination signal, and outputs a second signal D2 including information indicating the determined radiation ray type. The radioactivity analysis device 3 has a radiation detection unit 10b that detects radiation emitted from the measurement object 70 and outputs the first signal D1 including the discrimination signal indicating the pulse-height distribution of the radiation, and an information processing unit 3a that identifies the radioactive nuclides contained in the measurement object 70 and calculates the radioactivity strength [Bq] of the radioactive nuclides. The information processing unit 3a is, for example, a computer, and is capable of implementing the radioactivity analysis method according to the third embodiment.

[0061] FIG. 7 is a diagram showing the rise and decay characteristics of the amplitude of a pulse signal output from the detector 11 of the radiation detection unit 10b for each type of radiation. For example, if a semiconductor is used as the material of the detector 11 that interacts with radiation, electrons and holes are generated inside the semiconductor as radiation passes through it, but the mobility of the electrons and the mobility of the holes are different. For radiation types that react near the surface of the detector 11, such as α rays, the detector 11 is configured to increase the distance traveled by the holes, resulting in a gradual rise in the pulse (shown by the solid line in FIG. 7). For radiation types that react inside the detector 11 (deeper than the surface), such as γ rays and β rays, the rise is steep (shown by the dashed line in FIG. 7). The waveform discriminator 15 uses these differences in waveform shape to discriminate between radiation types, thereby enabling accurate detection of specific radiation types.

[0062] In the third embodiment, the inverse problem calculation unit 50 performs an inverse problem calculation using the inverse problem calculation algorithm selected by the inverse problem calculation algorithm selection unit 30 and a response function, thereby identifying the radioactive nuclides contained in the measurement object 70 from the first signal D1 and the second signal D2 and calculating the radioactivity strength [Bq] of the radioactive nuclides. The inverse problem calculation unit 50 may also perform an inverse problem calculation to calculate the radiation strength from the first signal D1 and the second signal D2.

[0063] As described above, according to the radioactivity analysis device 3 and the radioactivity analysis method of embodiment 3, the accuracy of the inverse problem calculation can be improved by selecting and using an appropriate inverse problem calculation algorithm from a plurality of inverse problem calculation algorithms.

[0064] Furthermore, the detection accuracy can be improved by determining a specific radiation type using the waveform discriminator 15 and combining the determination result with detection from pulse-height distribution by the radiation type determination unit 20. Furthermore, by correlating the detection result of a specific radiation type with the pulse-height distribution, the pulse-height distribution of the specific radiation type can be extracted, and the pulse-height distribution can be separated to solve the inverse problem.

[0065] Other than the above, the third embodiment is the same as the first or second embodiment.

[0066] 4. Fourth embodiment Figure 8 is a block diagram showing a schematic configuration of a radioactivity analyzing apparatus 4 according to embodiment 4. In Figure 8, components that are the same as or correspond to those shown in Figure 1 are assigned the same reference numerals as those shown in Figure 1. The radioactivity analyzing apparatus 4 according to embodiment 4 differs from the radioactivity analyzing apparatus 1 according to embodiment 1 in that the detector 11c of the radiation detecting unit 10c has a function of detecting a position to which energy has been imparted by radiation, and in that the radiation detecting unit 10c has a trajectory shape detecting unit 16.

[0067] The radioactivity analysis device 4 has a radiation detection unit 10c that detects radiation emitted from the measurement object 70 and outputs a first signal D1 based on the detected radiation and a trajectory signal that indicates the trajectory shape of the radiation, and an information processing unit 4a that identifies radioactive nuclides contained in the measurement object 70 and calculates the radioactivity strength [Bq] of the radioactive nuclides. The information processing unit 4a is, for example, a computer, and is capable of implementing the radioactivity analysis method according to the fourth embodiment.

[0068] The radiation detection unit 10c has a detector 11c having a substance that interacts with radiation, and a trajectory shape detection unit 16 which is a circuit that detects the position of a trajectory where energy is imparted by the radiation within the interacting substance and outputs a trajectory shape signal indicating the shape of the trajectory. The radiation type determination unit 20c determines the type of radiation based on a first signal D1 including the trajectory shape signal, and outputs a second signal D2 including information indicating the determined radiation type.

[0069] In the fourth embodiment, the detector 11c has a function of detecting a position where energy is imparted by radiation. For example, the detector 11c is a device in which a plurality of scintillation counter crystals are arranged in an array and a photodetector is disposed on each of the plurality of scintillation counter crystals arranged in the array (see, for example, Patent Document 2). The detector 11c may also be a device including a plurality of regularly arranged scintillation counter crystals and a camera (e.g., a CMOS (Complementary Metal Oxide Semiconductor) camera element, an SOI (Silicon-On-Insulator) imaging element, etc.) that captures light generated by the scintillation counter crystals. The detector 11c may also be a device having a semiconductor radiation detector (e.g., a Ge crystal) and a plurality of regularly spaced strip electrodes sandwiching the semiconductor radiation detector. The detector 11c may also be a device that detects a position where energy is imparted by radiation using a gas radiation detector having a plurality of wires or a plurality of regularly arranged gas radiation detectors.

[0070] [Patent Document 2] Special Publication No. 2016-514835

[0071] 9A to 9C are schematic diagrams showing the trajectory shapes in the detector 11c of the radiation detection unit 10c for each radiation ray type. FIGS. 9A to 9C show the trajectory shapes (side and top views) in the detector 11c for each radiation ray type. As shown in FIG. 9A, radiation with a short range and high imparted energy, such as α rays, has a trajectory shape that is a spread-out dot. As shown in FIG. 9B, β rays have a long range and pass through the detector in a linear fashion, resulting in an elongated shape. As shown in FIG. 9C, γ rays react at a single point and therefore have a dot-like shape that does not spread. By detecting this difference in shape with the radiation ray type determination unit 20c, the radiation ray type contained in the radiation emitted from the measurement target 70 can be determined and a second signal D2 can be generated.

[0072] As described above, according to the radioactivity analysis device 4 and the radioactivity analysis method of the fourth embodiment, the accuracy of the inverse problem calculation can be improved by selecting and using an appropriate inverse problem calculation algorithm from a plurality of inverse problem calculation algorithms.

[0073] Furthermore, the detection accuracy can be improved by determining a specific radiation ray type using the trajectory shape detection unit 16 and combining the determination result with detection from pulse-height distribution by the radiation ray type determination unit 20. Furthermore, by associating the detection result of a specific radiation ray type with the pulse-height distribution and extracting the pulse-height distribution of the specific radiation ray type, the pulse-height distribution can be separated and the inverse problem can be solved.

[0074] Other than the above, the fourth embodiment is the same as the first or second embodiment.

[0075] 5. Fifth embodiment Fig. 10 is a block diagram showing a schematic configuration of a radioactivity analyzing apparatus 5 according to embodiment 5. In Fig. 10, components that are the same as or correspond to those shown in Fig. 1 are assigned the same reference numerals as those shown in Fig. 1. The radioactivity analyzing apparatus 5 according to embodiment 5 differs from the radioactivity analyzing apparatus 1 according to embodiment 1 in that the radiation detecting unit 10d is configured as a position sensitive detector 11d.

[0076] The radioactivity analysis device 5 has a radiation detection unit 10d that detects radiation emitted from the measurement object 70 and outputs a signal D5 indicating a brightness value according to the type of radiation and the spread of the trajectory as a first signal based on the detected radiation, and an information processing unit 5a that identifies the radioactive nuclide contained in the measurement object 70 and calculates the radioactivity strength [Bq] of the radioactive nuclide. The information processing unit 5a is, for example, a computer, and is capable of implementing the radioactivity analysis method according to the fifth embodiment.

[0077] The radiation detection unit 10d includes a material that interacts with incident radiation, and a position-sensitive detector 11d that outputs a first signal D5 indicating the position within the interacting material at which the radiation imparts energy to the material and the amount of energy imparted to the material. The radiation type determination unit 20d determines the type of radiation based on the first signal D5, which includes a signal indicating the position at which energy is imparted to the material and the amount of energy imparted to the material, and outputs a second signal D2 including information indicating the determined type of radiation.

[0078] The position-sensitive detector 11d has a function of detecting a position where energy is imparted by incident radiation, and outputs a pulse having an amplitude corresponding to the imparted energy. Alternatively, the position-sensitive detector 11d has a function of detecting a position where energy is imparted by incident radiation, and outputs a luminance value of light generated at the energy-imparted position. The position-sensitive detector 11d outputs information on the energy-imparted position and pulse amplitude. Alternatively, the position-sensitive detector 11d outputs an image including information on the energy-imparted position and luminance value. The radiation ray type determination unit 20d determines the radiation ray type based on the image including the position information and pulse peak value or the position information and luminance value output from the position-sensitive detector 11d. The position-sensitive detector 11d can be realized in a similar manner to the detector 11c in embodiment 4.

[0079] FIG. 11 is a diagram showing the relationship between the luminance value and the spread of the trajectory shape in the position-sensitive detector 11d of the radiation detection unit 10d. As shown in FIG. 11, the relationship between the luminance value and the spread of the trajectory shape differs depending on the type of radiation. The luminance value of the light emission in the α-ray trajectory is higher than that of the other radiation types, and the spread of the luminance values ​​(width in the horizontal direction in FIG. 11) is larger than that of the other radiation types. The spread of the β-ray trajectory is higher than that of the other radiation types, and the luminance value of the light emission in the β-ray trajectory is lower than that of the other radiation types. The spread of the γ-ray trajectory is lower than that of the other radiation types, and the luminance value of the light emission in the γ-ray trajectory is lower than that of the α-ray trajectory. By detecting these differences, the radiation type determination unit 20d can determine the type of radiation contained in the radiation emitted from the measurement object 70 and generate a second signal D2.

[0080] As described above, according to the radioactivity analysis device 5 and the radioactivity analysis method of embodiment 5, the accuracy of the inverse problem calculation can be improved by selecting and using an appropriate inverse problem calculation algorithm from a plurality of inverse problem calculation algorithms.

[0081] In addition, the accuracy of determining the type of radiation can be improved, and by correlating the detection results of a specific radiation type with the pulse-height distribution, the pulse-height distribution of the specific radiation type can be extracted, and the pulse-height distribution can be separated to solve the inverse problem.

[0082] Other than the above, the fifth embodiment is the same as the first or second embodiment.

[0083] 6. Variations The response function selection unit 40 described in the second embodiment can be combined with any of the third, fourth, and fifth embodiments. [Explanation of symbols]

[0084] 1 to 5 radioactivity analysis device, 1a to 5a information processing unit, 10, 10b, 10c, 10d radiation detection unit, 11, 11b, 11c detector, 11d position detection detector, 12 amplifier, 13 waveform shaper, 14 pulse height analysis unit, 15 waveform discriminator, 16 trajectory shape detection unit, 20, 20b, 20c, 20d radiation ray type determination unit, 30 inverse problem calculation algorithm selection unit, 31 inverse problem calculation algorithm DB, 40 response function selection unit, 41 response function DB, 50 inverse problem calculation unit, 60 display unit, 70 measurement object.

Claims

1. a radiation detection unit that detects radiation emitted from the measurement object and outputs a first signal based on the radiation; a radiation type determination unit that determines a radiation type indicating a type of the radiation based on the first signal and outputs a second signal including information indicating the radiation type; an inverse problem calculation algorithm selection unit that selects an inverse problem calculation algorithm from a plurality of inverse problem calculation algorithms stored in advance in a storage device based on the radiation type; an inverse problem calculation unit that identifies radionuclides contained in the measurement object from the first signal and the second signal and calculates the intensity of radioactivity of the radionuclides by executing an inverse problem calculation using the selected inverse problem calculation algorithm and a response function of the radiation detection unit that is stored in advance in a storage device; A radioactivity analysis device comprising:

2. Further comprising a response function selection unit, a plurality of response functions are stored as the pre-stored response functions, the response function selection unit selects a response function from the plurality of response functions based on the type of radiation indicated by the second signal; The inverse problem calculation unit performs the inverse problem calculation using the selected inverse problem calculation algorithm and the selected response function, thereby identifying the radioactive nuclide contained in the measurement object from the first signal and the second signal and calculating the radioactivity of the radioactive nuclide.

2. The radioactivity analysis apparatus according to claim 1.

3. The inverse problem calculation unit calculates the intensity of the radiation from the first signal and the second signal by executing the inverse problem calculation.

2. The radioactivity analysis apparatus according to claim 1.

4. the radiation detection unit includes a detector that detects the radiation and outputs a detection signal, and a waveform discriminator that discriminates the detection signal for each type of radiation and outputs a discrimination signal; The radiation type determination unit determines the radiation type based on the first signal including the discrimination signal, and outputs the second signal including information indicating the radiation type.

4. The radioactivity analysis apparatus according to claim 1, wherein the radioactivity analysis apparatus is a radioactivity analysis apparatus.

5. the radiation detection unit includes a detector having a substance that interacts with the radiation, and a trajectory shape detection unit that detects the position of a trajectory where the radiation has imparted energy within the substance, and outputs a trajectory shape signal that indicates the shape of the trajectory; The radiation ray type determination unit determines the radiation ray type based on the first signal including the trajectory shape signal, and outputs the second signal including information indicating the radiation ray type.

4. The radioactivity analysis apparatus according to claim 1, wherein the radioactivity analysis apparatus is a radioactivity analysis apparatus.

6. the radiation detection unit includes a substance that interacts with the radiation, and a position-sensitive detector that outputs, as the first signal, a signal that indicates a position within the substance at which the radiation has imparted energy to the substance and an amount of the energy imparted to the substance; The radiation type determination unit determines the radiation type based on the first signal including a signal indicating a position where energy is applied to the material and an amount of the energy applied to the material, and outputs the second signal including information indicating the radiation type.

4. The radioactivity analysis apparatus according to claim 1, wherein the radioactivity analysis apparatus is a radioactivity analysis apparatus.

7. The radiation type is one or more of α-rays, β-rays, and γ-rays.

5. The radioactivity analysis apparatus according to claim 4.

8. The radiation type is one or more of alpha rays, beta rays, and gamma rays.

6. The radioactivity analysis apparatus according to claim 5.

9. The radiation type is one or more of alpha rays, beta rays, and gamma rays.

7. The radioactivity analysis apparatus according to claim 6.

10. 1. A computer-implemented method for radioactivity analysis, comprising: receiving a first signal from a radiation detection unit that detects radiation emitted from a measurement object and outputs a first signal based on the radiation; determining a radiation type indicating a type of the radiation based on the first signal, and outputting a second signal including information indicating the radiation type; selecting an inverse problem calculation algorithm from a plurality of inverse problem calculation algorithms stored in advance in a storage device based on the radiation type; a step of identifying radionuclides contained in the measurement object from the first signal and the second signal and calculating the intensity of radioactivity of the radionuclides by executing an inverse problem calculation using the selected inverse problem calculation algorithm and a response function of the radiation detection unit stored in advance in a storage device; A radioactivity analysis method comprising the steps of:

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