CN-122017939-A - Neutron energy spectrum resolving method, system, equipment and medium of single-sphere neutron spectrometer

CN122017939ACN 122017939 ACN122017939 ACN 122017939ACN-122017939-A

Abstract

Compared with the prior art, the invention firstly obtains count values of a plurality of detectors positioned at different depths in a single-sphere neutron spectrometer through one-time measurement, averages the count values of the plurality of detectors positioned at the same depth to obtain count average values of all depths, obtains count values of a plurality of thermal neutron detectors positioned at different depths in the single-sphere neutron spectrometer, averages the count values of all depths to obtain count average values of all depths, establishes a response matrix of direction average through Monte Carlo simulation, and finally carries out fitting solving on the count average values by taking a preset energy spectrum as an initial value and adopting an iterative calculation method based on a least square criterion, thereby stably outputting neutron energy spectrum under the constraint of the count input and the response matrix, reducing the influence of random fluctuation of the count on a resolving result and improving the stability and reliability of energy spectrum resolving.

Inventors

SUN BOWEN
WANG HONGYU
LIU XINHAO
WANG ZHEN
LI YIN
FENG MEI
TANG ZHIHUI
FANG DENGFU
WEI YINGJING
LI KAILUN

Assignees

中国辐射防护研究院

Dates

Publication Date: 20260512
Application Date: 20251231

Claims (10)

1. The neutron spectrum resolving method of the single-sphere neutron spectrometer is characterized by comprising the following steps of: S1, obtaining count values of a plurality of detectors positioned at different depths in a single-sphere neutron spectrometer through one-time measurement, and averaging the count values of the plurality of detectors at the same depth to obtain a count average value of each depth; S2, obtaining response functions of the detector to neutrons with different energies in advance through Monte Carlo simulation, carrying out direction average on responses of different incidence directions, and establishing a response matrix with the direction average; S3, based on a least square criterion, taking a preset energy spectrum as an initial value, carrying out fitting solution on the counting average value of each depth by adopting an iterative calculation method, obtaining a neutron energy spectrum of the measured neutrons and outputting the neutron energy spectrum.
2. The neutron spectrum calculation method according to claim 1, further comprising a neutron incidence direction deriving step Sa4. The step Sa4 is used for deducing an included angle between a neutron incidence direction and a selected reference axis, the step Sa4 comprises the steps of Sa41, determining a counting input used for direction deduction based on a counting average value of each depth obtained in the step S1, sa42, calculating theoretical counts corresponding to different candidate incidence angles based on responses of detectors obtained through Monte Carlo calculation to different incidence angles and combining neutron energy spectrums obtained in the step S3, comparing the theoretical counts with the counting input to determine candidate incidence angles matched with the counting input, and Sa43, taking the determined candidate incidence angles as included angles between the neutron incidence direction and the reference axis and outputting the included angles.
3. The neutron spectrum calculation method according to claim 1 or 2, further comprising a neutron fluence orthogonal component inversion step Sb4 when the incidence direction is not single and a plurality of neutron source items exist, wherein the step Sb4 is used for neutron fluence orthogonal component inversion, the step Sb4 comprises the steps of sb41, taking three mutually orthogonal reference axes, representing the incidence neutrons as components in six directions of x, negative x, y, negative y, z and negative z, sb42, establishing a solution relation between the detector count value and the neutron energy spectrum in the six directions based on the response of the detector obtained by Monte Carlo calculation and combining the detector count value and a preset energy spectrum, and sb43, based on an iterative solution spectrum algorithm, simultaneously solving and outputting the neutron energy spectrum in the six directions in the same iterative solution process, wherein the neutron fluence orthogonal component inversion is suitable for the situation that the incidence direction is not single and a plurality of neutron source items exist.
4. The neutron spectrum resolving method of the single-sphere neutron spectrometer according to claim 1, wherein the response matrix of the direction average is obtained by selecting a plurality of representative incidence directions in a 4 pi solid angle range, respectively calculating responses of the detector to neutrons with different energies in each incidence direction based on Monte Carlo simulation, and calculating weights corresponding to each incidence direction, and calculating a weighted average of the responses corresponding to the plurality of incidence directions according to a given weight to obtain the response matrix of the direction average.
5. The method for resolving neutron spectrum of single-sphere neutron spectrometer according to claim 1, wherein the detectors are uniformly arranged along a plurality of depth positions inside the sphere-shaped moderating body, the detectors are respectively arranged at the positions 2cm, 4cm, 6cm and 8cm away from the sphere center, the same number of detectors are arranged at each of the depth layers of 2cm and 4cm, 6cm and 8cm, and the detectors are distributed along the directions of mutually orthogonal x, y and z axes.
6. The neutron spectrum calculation method of the single sphere neutron spectrometer according to claim 1, wherein the iterative calculation step is based on a least square criterion, iterates with a preset energy spectrum as an initial value, and updates a neutron energy spectrum estimated value according to the detector count and a response function thereof in each iteration until a preset iteration number or convergence condition is reached.
7. The neutron spectrum calculation method according to claim 6, wherein in the iterative calculation, a weight factor is calculated from the response value of each detector to neutrons of different energies and the measurement error of the detector count, and a weighted least square iterative calculation is performed based on the weight factor.
8. A neutron spectrum resolving system of a single sphere neutron spectrometer for implementing the neutron spectrum resolving method of any of claims 1-7, characterized in that the system comprises a detection system, an electronics system and a processing system; The detection system comprises a single spherical moderating body and thermal neutron detectors arranged at a plurality of depth positions in the moderating body and used for obtaining corresponding detector signals, the electronic system is used for converting the detector signals into counting data of the thermal neutron detectors, and the spectrum resolution system is used for receiving the counting data, calling the response matrix and the preset energy spectrum and executing iterative computation to output neutron energy spectrum.
9. An electronic device comprising a memory and at least one processor, the memory having stored therein a computer program which, when executed on the processor, is capable of performing the method of resolving neutron spectra in a single sphere neutron spectrometer according to any of claims 1-7.
10. A computer readable storage medium, characterized in that the storage medium has stored thereon a computer program comprising instructions for implementing the neutron spectrum resolution method according to any of claims 1-7 when the computer program is executed by a processor.

Description

Neutron energy spectrum resolving method, system, equipment and medium of single-sphere neutron spectrometer Technical Field The invention relates to the field of neutron spectrum measurement, in particular to a neutron spectrum resolving method of a single-sphere neutron spectrometer, a neutron spectrum resolving system of the single-sphere neutron spectrometer, electronic equipment and a computer readable storage medium. Background Neutron energy spectrum is an important physical quantity for representing neutron field energy distribution, and is widely used in the scenes of nuclear facility radiation protection evaluation, shielding design verification, source item identification, dose evaluation and the like. The single-sphere neutron spectrometer is characterized in that a plurality of thermal neutron detectors with different depths are arranged in a spherical moderating body, and the moderating body is utilized to produce different moderating and capturing characteristics for neutrons with different energies, so that the response of each depth detector to the incident neutrons is different, and the neutron energy spectrum can be obtained through inversion of multi-channel counting information. In the prior art, the measurement result of the single-sphere neutron spectrometer is usually represented as the count value or the count rate of a plurality of detectors, and further spectrum resolving operation is still needed to obtain neutron energy spectrum which can be used for engineering analysis, so that the spectrum resolving algorithm and software implementation are indispensable key links in the application link of the single-sphere neutron spectrometer. However, the existing single-sphere neutron spectrometer spectrum resolving technology still faces more unsolved problems in practical engineering application, and particularly has obvious defects in the aspects of stability, result reliability, characterization capability of a complex neutron field and the like of energy spectrum resolving. Firstly, in the inversion process of converting the counting information of different depth detectors into neutron energy spectrum in the prior art, the problems of unstable resolving and larger fluctuation of results are commonly existed. On the one hand, neutron spectrum inversion belongs to a typical system of underdetermined equations, and due to measurement error effects, the equations inevitably have ill-condition. The response of the detector counting to the energy distribution has a coupling relation, and counting statistical fluctuation and background interference are unavoidable in actual measurement, and the response is highly sensitive to input errors in the inversion process, so that the result errors are amplified. On the other hand, the prior art often fails to form a set of unified spectrum solving operation logic adapting to a single-sphere multi-depth structure, so that the counting data of different depth detectors lack a consistent constraint mode in the processes of input organization, response modeling and iterative solving, and the problems of obvious spectrum solving result difference and insufficient repeated measurement consistency under different measurement conditions are easy to occur. On the other hand, the response data of the detector is needed to be relied on in the spectrum decomposition process, but the acquisition modes of the response data, the incident condition assumption and the matching modes with the actual measurement count in different realization paths are not uniform, so that systematic deviation can exist between the response matrix and the measurement data, and the reliability and the stability of the neutron energy spectrum output result are influenced. The problems directly limit the usability of the single-sphere neutron spectrometer in the long-term monitoring or multi-scene rapid measurement of a nuclear facility, and the single-sphere neutron spectrometer belongs to core defects which need to be solved in the prior art. Secondly, the prior art has insufficient characterization dimension of the complex neutron field, and more abundant direction characteristic information is difficult to obtain from a single-sphere measurement result. Most of the existing single-sphere neutron spectrometers only pay attention to inversion of energy spectrum, neutron direction information is ignored, in an actual application scene, a neutron field is often not ideally incident in a single direction, for example, multiple source items, multi-directional superposition caused by reflection scattering, uneven spatial distribution and the like can exist, and only the neutron energy spectrum is output, so that the requirements of source item discrimination, field intensity spatial distribution analysis, environmental neutron field characteristic recognition and the like are difficult to meet. Because the personal dose is closely related to the neutron direction, if the neutron directio