Method for measuring spatial distribution of radionuclides based on array detectors

Abstract

The present invention belongs to the field of radiation protection and environmental protection, and particularly relates to a method for measuring the spatial distribution of radioactive nuclides based on an array detector, wherein an array detector composed of a plurality of sub-detectors is set up in a measured space, and the space is divided into a plurality of sub-spaces equal to the number of sub-detectors. After the measurement is completed, the activity concentration of the radioactive nuclide of interest in each sub-space is calculated using formula (1) to obtain the three-dimensional distribution of the nuclide in space. The present invention establishes a method for measuring the spatial distribution of radioactive nuclides based on an array detector, which can be used for measuring the three-dimensional distribution of γ-radioactive nuclides of interest in any space without having the information on the distribution law of the nuclides in advance, and is of great significance to environmental radioactivity investigation, evaluation, and radiation protection.

Description

Technical Field

[0001] The invention belongs to the field of radiation protection and environmental protection, and in particular relates to a method for measuring the spatial distribution of radioactive nuclides based on an array detector. Background Art

[0002] The spatial distribution of γ-radioactive nuclides is an important parameter for environmental radioactive pollution assessment and radiation protection. It is usually assumed that the distribution obeys a certain law, and a single crystal detector is used to measure and obtain the γ spectrum. According to the net count rate of the full energy peak of interest in the γ spectrum and the assumed distribution law, the nuclide distribution state is calculated, which makes it difficult to achieve three-dimensional identification of the spatial distribution of nuclides. For example, when measuring the surface soil, the soil layer is often divided into multiple sub-plane layers, and it is assumed that the nuclides of interest are uniformly distributed in each layer. The γ spectrum corresponding to different heights is obtained by changing the height of the detector from the ground. The activity concentration of the nuclides of interest in each sub-plane layer is calculated based on the γ spectrum data to obtain the depth distribution state of the nuclides. Or for nuclides that emit γ rays of multiple energies, the measurement height is not changed, and the depth distribution state of the nuclides is obtained by analyzing the net count rate of different characteristic peaks of the same nuclide in the spectrum. There is only spatial recognition of distribution in the depth direction, and no recognition in the direction parallel to the surface. At present, no effective method has been found to solve this problem. Summary of the invention

[0003] The purpose of the present invention is to establish a method for analyzing and obtaining the three-dimensional distribution of unknown distribution regularity gamma radioactive nuclides in space by measuring gamma energy spectrum on site.

[0004] To achieve the above object, the present invention provides the following technical solution: a method for measuring the spatial distribution of radioactive nuclides based on an array detector, characterized in that: an array detector composed of a plurality of sub-detectors is set up in a measured space, and the space is divided into a plurality of sub-spaces equal to the number of sub-detectors. After the measurement is completed, the activity concentration of the radioactive nuclide of interest in each sub-space is calculated using formula (1) to obtain the three-dimensional distribution of the nuclide in the space:

[0005]

[0006] In formula (1), Ai is the activity of the nuclide of interest in the ith subspace, which is the value to be solved, Bq; Pr is the emission probability of the characteristic γ-ray of the nuclide of interest; ε ij is the detection efficiency of the j-th sub-detector for the γ-ray of the energy of interest emitted by the nuclide of interest in the i-th subspace, which can be obtained through simulation calculation or experiment; Nj is the net count rate of the characteristic peak of the γ-ray of the energy of interest measured by the j-th sub-detector, cps;

[0007] When using equation (1) to solve Ai, if the number of sub-detectors is large and the structural symmetry in the array is good, we usually encounter an ill-conditioned problem, that is, using εij The energy response matrix composed of the above equations is highly ill-conditioned and can be solved by using the ill-conditioned equation group solution method of equation (2):

[0008]

[0009] In formula (2), ε is the energy response matrix, ε′ ji =ε ij 3 ; K is the number of subspaces; P represents the Pth iteration. When P=0, Ai is the initial iteration value and can be set to any positive number.

[0010] Compared with the prior art related to the present invention, the beneficial effects of the present invention are as follows: as a method for on-site measurement of the spatial distribution of γ-radioactive nuclides based on array detectors, the present invention has established a method for measuring the spatial distribution of radioactive nuclides based on array detectors, which can be used for three-dimensional distribution measurement of γ-radioactive nuclides in any space without prior knowledge of the information on the distribution law of nuclides, and is of great significance to environmental radioactivity investigation, evaluation, and radiation protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic diagram of a three-dimensional conceptual model of the present invention, in which an array detector is set up in the measured space, and the number of subspaces is equal to the number of subdetectors; Figure 1 In the figure, 1-array detector; 2-measured space, the γ-radioactive nuclides are evenly distributed in each sub-interval, and the activity concentration of the nuclides in each interval is different. DETAILED DESCRIPTION

[0012] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0013] The model of the present invention is as follows Figure 1 As shown in the figure, an array detector composed of multiple sub-detectors is set up in the measured space, and the space is divided into multiple sub-spaces equal to the number of sub-detectors. After the measurement is completed, the activity concentration of the radioactive nuclide of interest in each sub-space is calculated using formula (1) to obtain the three-dimensional distribution of the nuclide in the space:

[0014]

[0015] In formula (1), Ai is the activity of the nuclide of interest in the ith subspace, which is the value to be solved, Bq; Pr is the emission probability of the characteristic γ-ray of the nuclide of interest; ε ijis the detection efficiency of the j-th sub-detector for the γ-ray of the energy of interest emitted by the nuclide of interest in the i-th subspace, which can be obtained through simulation calculation or experiment; Nj is the net count rate of the characteristic peak of the γ-ray of the energy of interest measured by the j-th sub-detector, cps;

[0016] When using equation (1) to solve Ai, if the number of sub-detectors is large and the structural symmetry in the array is good, we usually encounter an ill-conditioned problem, that is, using ε ij The energy response matrix composed of the above equations is highly ill-conditioned and can be solved by using the ill-conditioned equation group solution method of equation (2):

[0017]

[0018] In formula (2), ε is the energy response matrix, K is the number of subspaces; P represents the Pth iteration, and when P=0, Ai is the initial iteration value, which can be set to any positive number.

[0019] Notes of the present invention: Before measurement, the array detector structure needs to be flexibly designed, the sub-detector type selected, and the number of sub-detectors determined according to the size of the measured space, the gamma-ray energy of interest, and the three-dimensional recognition accuracy requirements of the space; each sub-detector needs to independently output the gamma energy spectrum; the higher the spatial recognition accuracy requirement, the smaller the volume of the divided subspace should be, and the more sub-detectors should be needed; the subspace can be arbitrarily divided according to needs; if the array detector is set up at the center of the measured space, the size of each subspace and its relative position to each subdetector should be as different as possible to reduce the pathological nature of the energy response matrix; after actual measurement, the energy spectrum data measured by each subdetector is substituted into formula (2) to calculate the activity of the nuclide of interest in each subspace, and the three-dimensional distribution of the nuclide in space can be obtained.

Claims

1. A method for measuring the spatial distribution of radionuclides based on an array detector, characterized in that: An array detector consisting of multiple sub-detectors is set up in the measured space, and the space is divided into multiple sub-spaces equal to the number of sub-detectors. After the measurement is completed, the activity concentration of the radioactive nuclide of interest in each sub-space is calculated using formula (1) to obtain the three-dimensional distribution of the nuclide in the space: In formula (1), Ai is the activity of the nuclide of interest in the ith subspace, which is the value to be solved, Bq; Pr is the emission probability of the characteristic γ-ray of the nuclide of interest; ε ij is the detection efficiency of the j-th sub-detector for the γ-ray of the energy of interest emitted by the nuclide of interest in the i-th subspace, obtained through simulation calculation or experiment; Nj is the net count rate of the characteristic peak of the γ-ray of the energy of interest measured by the j-th sub-detector, cps; When using equation (1) to solve Ai, if the number of sub-detectors is large and the structural symmetry in the array is good, the ill-conditioned equation group solution method of equation (2) can be used to solve it: In formula (2), ε is the energy response matrix, ε′ ji =ε ij 3 ; K is the number of subspaces; P represents the Pth iteration, when P=0, Ai is the initial iteration value, which can be set to any positive number.

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