Method and apparatus for measuring mass of plutonium in a container

Abstract

The present application relates to the technical field of nuclear radiation measurement, and discloses a kind of measurement method and device for the mass of plutonium in container, according to the gamma and neutron emission characteristics of plutonium, combined gamma spectrum and neutron measurement, realize the complementary advantages of two kinds of detection, avoid the defects of single gamma spectrum by spectrum peak overlap, sample self-absorption interference, single neutron method by particle induced neutron interference.No need to match the same physical standard source to calibrate detection efficiency, with the help of simulation fitting to complete quantitative calculation, reduce the risk of test and irradiation.Dual-path respectively accounts the mean value of isotope mass, effectively weakens systematic error, improves the measurement accuracy of whole component plutonium isotope, can complete the accurate detection of barrel-packed plutonium material under non-destructive condition without opening.

Description

Technical Field

[0001] This invention relates to the field of nuclear radiation measurement technology, specifically to a method and apparatus for measuring the mass of plutonium in a container. Background Technology

[0002] Plutonium oxalate and plutonium nitrate are important intermediate products in plutonium recovery during the closed nuclear fuel cycle, and accurate quality assessment is crucial for subsequent reprocessing procedures. Nuclear radiation detection technology is a key method for plutonium quality measurement, mainly divided into two categories: gamma spectroscopy and neutron measurement.

[0003] Gamma spectroscopy measurements utilize information from gamma peaks to invert the mass of nuclides. This method establishes a passive calibration curve by correlating the full-energy peak energy deposition count of gamma peaks with the mass of radioactive nuclides, thereby calculating the mass. However, gamma spectroscopy has three main challenges: First, selecting suitable gamma peaks is difficult: the gamma spectrum contains numerous overlapping gamma peaks, and interference from other radioactive nuclides further complicates peak selection. Second, it is unsuitable for nuclides with low gamma-ray emissivity: due to the limited detection efficiency of detectors, it is difficult to capture gamma rays with low emissivity. Third, the detection efficiency is difficult to calculate: many factors affect detection efficiency, including geometry, attenuation, and the detector itself. In actual measurements, the physical characteristics of the measured objects are rarely identical, thus requiring detection efficiency calibration before each measurement, which is extremely inconvenient.

[0004] The total neutron count method is more widely used in neutron measurement. This method utilizes the radioactive properties of the sample itself to statistically analyze the neutrons emitted by plutonium isotopes and establish a passive calibration curve between neutron count and mass. However, this method has two difficulties: first, even-numbered plutonium isotopes (such as Pu-238, Pu-240, and Pu-242) have high neutron emissivity, making it difficult for the total neutron count method to detect the contribution of odd-numbered isotopes such as Pu-239, which have lower neutron emissivity; second, ( α The neutron energy spectrum and yield of the n) reaction are difficult to calculate: the neutrons produced by the isotopic decay of plutonium α The particles react with light nuclides (O, N, etc.) α The reaction, n), the neutron yield and energy spectrum of this reaction are related to α The energy of a particle is related to the type of light nuclide.

[0005] Therefore, there is an urgent need to develop a plutonium mass calculation scheme that is compatible with different plutonium isotopes and avoids spectral interference and side reaction neutron interference. Summary of the Invention

[0006] This invention provides a method and apparatus for measuring the plutonium mass in a container, thereby addressing the shortcomings of existing plutonium mass calculation schemes.

[0007] In a first aspect, the present invention provides a method for measuring the mass of plutonium in a container, the method comprising: Based on gamma spectroscopy, the plutonium isotope mass ratio in the sample is calculated by using the area, branching ratio and relative detection efficiency of the gamma peak of the sample. Based on the mass ratio of the plutonium isotopes, multiple sets of gamma parameters of plutonium-239 were simulated and modeled to obtain fitting curves of gamma peak area and plutonium-239 mass. The mass of plutonium-239 was determined by combining the measured gamma peak area with the fitted curve. Based on the neutron energy spectrum and neutron emissivity of the sample to be tested, and in combination with the plutonium isotope mass ratio, a relationship between the equivalent mass of plutonium-240 and the neutron multiplication leakage coefficient is constructed. Substitute the measured total neutron count and neutron multiplication leakage coefficient of the sample to be tested into the relationship to calculate the equivalent mass of plutonium-240; The plutonium isotope mass ratios are combined with the plutonium-239 mass and the plutonium-240 equivalent mass to obtain two sets of initial plutonium isotope masses, which are then averaged to determine the target plutonium isotope mass.

[0008] This invention leverages the gamma and neutron emission characteristics of plutonium, combining gamma spectroscopy and neutron measurement to achieve complementary advantages between the two detection methods. It avoids the limitations of single gamma spectroscopy, which is affected by peak overlap and sample self-absorption interference, and single neutron methods, which are susceptible to interference from particle-induced neutrons. No standard source with similar properties is required to calibrate detection efficiency; quantitative calculations are performed using simulation fitting, reducing experimental and irradiation risks. The dual-path isotope mass calculation followed by averaging effectively reduces systematic errors and improves the accuracy of plutonium isotope metrology across all components. This allows for precise detection of drummed plutonium materials without opening or damaging the packaging.

[0009] In one optional implementation, the calculation of the plutonium isotope mass ratio in the sample based on gamma spectroscopy, using the area, branching ratio, and relative detection efficiency of the gamma peaks, includes: Input the gamma energy spectrum of the sample to be tested into the gamma spectroscopy analysis software to determine the energy scale and resolution; Based on the energy scale and the fitting function corresponding to the resolution, the peak shape of the gamma peak of the sample to be tested is fitted to generate a gamma peak shape function. The area of ​​the corresponding gamma peak is calculated using the gamma peak shape function; Using any gamma peak of the sample to be tested as a reference peak, the relative detection efficiency of the gamma peak to be tested is calculated based on the area and branching ratio of the reference peak, the area and branching ratio of the gamma peak to be tested, and the relative activity between the reference peak and the gamma peak to be tested. Based on the curves corresponding to the area, branching ratio, half-life, and relative detection efficiency of the gamma peak, the relative and absolute proportions of each nuclide in the sample to be tested are calculated, and the mass ratio of plutonium isotopes in the sample to be tested is determined.

[0010] This invention relies on energy spectrum calibration and peak shape fitting to accurately isolate overlapping peaks, and uses the characteristic peak of plutonium-241 as a benchmark to calculate the relative detection efficiency, eliminating the need for physical standard source calibration. It calculates isotope ratios based on efficiency curves combined with nuclear parameters, avoiding efficiency calibration errors caused by sample self-absorption and container attenuation, thus improving the accuracy of multi-plutonium isotope ratio calculations.

[0011] In one optional implementation, the step of using any gamma peak of the sample to be tested as a reference peak, and calculating the relative detection efficiency of the gamma peak to be tested based on the area and branching ratio of the reference peak, the area and branching ratio of the gamma peak to be tested, and the relative activity between the reference peak and the gamma peak to be tested, includes: Based on the gamma spectrum, the relative activity between the two nuclides is preset to a preset value; Using any gamma peak of plutonium in the sample to be tested as a reference peak, the detection efficiency of the remaining gamma rays relative to the reference peak is set as the initial relative detection efficiency. Based on preset fitting coefficients, fit the curve of the initial relative detection efficiency to determine the optimized relative detection efficiency; Based on the optimized relative detection efficiency, the relative activity of multiple gamma peaks of any nuclide is calculated, and all the relative activities are averaged to obtain the average relative activity of the corresponding nuclide. Based on the average relative activity, calculate the new initial relative detection efficiency of the gamma peak to be measured, and then proceed to the step of fitting the curve of the initial relative detection efficiency according to the preset fitting coefficient to determine the optimized relative detection efficiency, until the final relative detection efficiency of the gamma peak to be measured is obtained.

[0012] This invention employs iterative optimization of relative detection efficiency, using the plutonium-241 characteristic peak as a benchmark to iteratively correct efficiency and activity, thus eliminating dependence on physical standard sources. By averaging the activity of multiple characteristic peaks and iteratively converging parameters, it offsets calculation biases caused by energy spectrum overlap and sample self-absorption, improving the accuracy of detection efficiency calculation and ensuring the accuracy of subsequent plutonium isotope mass ratio determination.

[0013] In one optional implementation, the step of simulating and modeling multiple sets of gamma parameters of plutonium-239 based on the mass ratio of the plutonium isotopes to obtain a fitting curve of gamma peak area and plutonium-239 mass includes: Based on the mass ratio of the plutonium isotopes, a geometric model of the sample to be tested and the detector was constructed using the Monte Carlo method. The plutonium-239 gamma rays and corresponding gamma parameters are input into the geometric model to perform multiple sets of plutonium-239 mass simulation calculations, and the gamma peak area corresponding to each set of simulation conditions is obtained. Based on the plutonium-239 mass and the corresponding gamma peak area of ​​each group, a fitting curve of the gamma peak area and the plutonium-239 mass is obtained.

[0014] This invention utilizes a Monte Carlo geometric model constructed based on known isotopic ratios. Multi-gradient simulations yield the correlation curve between peak area and plutonium-239 mass, eliminating the need for preparing multiple sets of gradient standard samples. This method can offset measurement biases caused by sample matrix, container structure, and detector geometry. The plutonium-239 mass can be quickly calculated from the measured peak area, simplifying the calibration process and improving the reliability of quantitative results for single plutonium nuclides.

[0015] In one optional implementation, the step of constructing a relationship between the equivalent mass of plutonium-240 and the neutron multiplication leakage coefficient based on the neutron energy spectrum and neutron emissivity of the sample under test, combined with the plutonium isotope mass ratio, includes: Based on the Watt spectrum, the spontaneous fission energy spectrum of the plutonium sample was determined; Using a preset nuclide to a preset energy The particle's energy-stopping ability and the preset energy Cross section of particle-nuclide reaction producing high-energy neutrons, calculate neutron yield at each energy; By combining the neutron yield at each of the described energies, the energy spectrum of the particle-induced neutron reaction is determined; The neutron energy spectrum of the plutonium sample is determined based on the spontaneous fission energy spectrum and the energy spectrum of the particle-induced neutron reaction. According to the preset energy The particle and each of the aforementioned nuclides are used to determine the emission rate of the neutron-induced reaction of the particle; The emission rate of the spontaneous fission was extracted and combined with the emission rate of the particle-induced neutron reaction to determine the emission rate of the plutonium sample. Based on the Monte Carlo method, the neutron energy spectrum, emissivity and mass ratio of the plutonium isotopes of the plutonium sample were simulated, and the curves of the plutonium-240 equivalent mass and the neutron multiplication leakage coefficient were fitted and the relationship was constructed.

[0016] This invention separately calculates the energy spectrum and emissivity of neutrons from spontaneous fission and particle-induced neutrons, accurately solving for neutron yield based on stopping power and reaction cross-section, thus improving the fundamental parameters of neutron sources. By fitting the correlation between equivalent mass and leakage coefficient through Monte Carlo simulation, it takes into account the contributions of both types of neutrons, reduces interference from matrix components, improves the accuracy of plutonium-240 equivalent mass back-calculation, and refines the basis for quantitative calculations using the neutron method.

[0017] In one optional implementation, the step of combining the plutonium isotope mass ratio with the plutonium-239 mass and the plutonium-240 equivalent mass respectively to obtain two sets of initial plutonium isotope masses, averaging them, and determining the target plutonium isotope mass includes: The initial mass of each plutonium isotope is calculated using the plutonium isotope mass ratio and the plutonium-239 mass. The second initial mass of each plutonium isotope is calculated using the plutonium isotope mass ratio and the equivalent mass of plutonium-240. The target mass of each plutonium isotope is determined by averaging the first initial mass and the second initial mass of each plutonium isotope.

[0018] This invention obtains the initial masses of two sets of isotopes through gamma quantification and neutron quantification, respectively, and uses the average value to complete the final calculation. This can mutually cancel out the systematic errors of gamma measurement and neutron measurement. By combining the technical advantages of two detection methods, it avoids the inherent biases caused by a single measurement method, effectively improves the accuracy of the measurement of various plutonium isotope masses, and further ensures the reliability of the non-destructive quantitative results of the sample.

[0019] Secondly, the present invention provides a device for measuring the mass of plutonium in a container, the device comprising: The calculation module is used to calculate the plutonium isotope mass ratio in the sample to be tested based on the gamma spectroscopy method, using the area of ​​the gamma peak, the branching ratio, and the relative detection efficiency of the sample to be tested. The modeling module is used to simulate and model multiple sets of gamma parameters of plutonium-239 based on the mass ratio of the plutonium isotopes, and obtain the fitting curve of gamma peak area and plutonium-239 mass. The solution module is used to calculate the mass of plutonium-239 by combining the measured gamma peak area and the fitted curve. A construction module is used to construct a relationship between the equivalent mass of plutonium-240 and the neutron multiplication leakage coefficient based on the neutron energy spectrum and neutron emissivity of the sample to be tested, and in combination with the mass ratio of the plutonium isotopes. The substitution module is used to substitute the measured total neutron count and neutron multiplication leakage coefficient of the sample to be tested into the relationship to calculate the equivalent mass of plutonium-240; The module is used to combine the plutonium isotope mass ratio with the plutonium-239 mass and the plutonium-240 equivalent mass respectively to obtain two sets of initial plutonium isotope masses, and then perform averaging to determine the target plutonium isotope mass.

[0020] Thirdly, the present invention provides an electronic device comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to perform the method for measuring the plutonium mass in a container as described in the first aspect or any corresponding embodiment thereof.

[0021] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to perform a method for measuring the plutonium mass in a container according to the first aspect or any corresponding embodiment described above.

[0022] Fifthly, the present invention provides a computer program product, including computer instructions for causing a computer to execute the method for measuring the plutonium mass in a container according to the first aspect or any corresponding embodiment described above. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a method for calculating plutonium mass according to an embodiment of the present invention; Figure 2 This is a schematic flowchart of a first method for measuring the mass of plutonium in a container according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a second process for measuring the plutonium mass in a container according to an embodiment of the present invention; Figure 4 This is a Monte Carlo model schematic diagram of the detector and plutonium sample according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the gamma spectrum of the Pu material according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the relative detection efficiency curve according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the fitting curve of gamma peak area and Pu-239 mass according to an embodiment of the present invention; Figure 8 According to the embodiments of the present invention ( , n Schematic diagram of the reaction energy spectrum; Figure 9This is a schematic diagram of the fitting curves of the equivalent mass and multiplied leakage coefficient of Pu-240 according to an embodiment of the present invention; Figure 10 This is a schematic diagram showing the ratio of the calculated result of the measured sample to the reference result according to an embodiment of the present invention; Figure 11 This is a structural block diagram of a device for measuring the plutonium mass in a container according to an embodiment of the present invention; Figure 12 This is a schematic diagram of the hardware structure of an electronic device according to an embodiment of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It is understood that before using the technical solutions disclosed in the various embodiments of the present invention, users should be informed of the types, scope of use, and usage scenarios of the personal information involved in the present invention and their authorization should be obtained in accordance with relevant laws and regulations through appropriate means.

[0027] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0028] This invention addresses the shortcomings of gamma spectroscopy and neutron analysis by combining their advantages to provide a method for measuring plutonium isotope quality in a container. The technical solution adopted in this invention is as follows: Figure 1 As shown.

[0029] This invention provides a method for measuring the mass of plutonium in a container. Based on the gamma and neutron emission characteristics of plutonium, this invention combines gamma spectroscopy and neutron measurement to achieve complementary advantages of both methods, avoiding the drawbacks of single gamma spectroscopy (affected by peak overlap and sample self-absorption) and single neutron method (affected by particle-induced neutron interference). No standard source of similar properties is required to calibrate detection efficiency; quantitative calculation is achieved through simulation fitting, thus reducing experimental and irradiation risks. The method involves calculating the isotopic mass separately using two paths and then averaging the results, effectively reducing systematic errors and improving the accuracy of plutonium isotope measurement across all components. This allows for precise detection of plutonium materials in containers without opening or damaging the container.

[0030] According to an embodiment of the present invention, a method for measuring the mass of plutonium in a container is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0031] This embodiment provides a method for measuring the mass of plutonium in a container. Figure 2 This is a flowchart of a method for measuring the mass of plutonium in a container according to an embodiment of the present invention, as shown below. Figure 2 As shown, the process includes the following steps: Step S101: Based on gamma spectroscopy, the plutonium isotope mass ratio in the sample is calculated using the area, branching ratio, and relative detection efficiency of the gamma peaks in the sample.

[0032] It should be noted that gamma spectroscopy refers to a non-destructive detection and analysis method that collects radioactive gamma rays from a sample and inverts the internal nuclide composition and content based on the ray energy and count data; gamma peak area refers to the total pulse count integral value corresponding to the characteristic full-energy peak in the gamma energy spectrum, characterizing the ray activity of the corresponding nuclide; branching ratio refers to the proportion of decay branches that emit gamma rays of a specific energy to the total decay when a radioactive nuclide decays; relative detection efficiency refers to the ratio of the detection efficiency of other nuclides to the detection efficiency of a selected reference nuclide, eliminating the need for absolute detector efficiency calibration; plutonium isotope mass ratio refers to the proportion of the mass of various plutonium nuclides (plutonium-238, plutonium-239, plutonium-240, etc.) in the total mass of plutonium in the sample.

[0033] In this embodiment of the invention, radioactive gamma energy spectrum data of the sample to be tested are collected, and the area of ​​each characteristic gamma peak is obtained by energy spectrum calibration and peak shape fitting. Using the characteristic peak of plutonium-241 as a reference, the relative detection efficiency of each ray to be tested is obtained through iterative calculation. Combined with the branching ratio and half-life parameters of each nuclide, the proportion of each type of plutonium nuclide is calculated item by item, and finally the mass ratio of plutonium isotopes inside the sample to be tested is determined.

[0034] Step S102: Based on the mass ratio of plutonium isotopes, simulate and model multiple sets of gamma parameters of plutonium-239 to obtain the fitting curve of gamma peak area and plutonium-239 mass.

[0035] It should be noted that the fitted curve is a function curve obtained by fitting the plutonium-239 mass and the corresponding gamma peak area of ​​the simulation data as variables.

[0036] In this embodiment of the invention, the material composition is determined based on the calculated plutonium isotope mass ratio. A Monte Carlo algorithm is used to build an integrated geometric model of the sample and detector. The gamma characteristic parameters corresponding to Pu-239 are entered. Simulation calculations are carried out by setting multiple gradient Pu-239 masses. The characteristic gamma peak areas corresponding to each set of simulations are collected. Based on the multiple sets of corresponding data, a correlation fitting curve between the gamma peak area and the Pu-239 mass is generated.

[0037] Step S103: Combine the measured gamma peak area and the fitted curve to solve for the mass of plutonium-239.

[0038] In this embodiment of the invention, the mass of Pu-239 can be deduced by combining the actual measured gamma peak area with the fitted curve.

[0039] Step S104: Based on the neutron energy spectrum and neutron emissivity of the sample to be tested, and combined with the plutonium isotope mass ratio, construct the relationship between the equivalent mass of plutonium-240 and the neutron multiplication leakage coefficient.

[0040] It should be noted that the neutron energy spectrum refers to the distribution of the number of neutrons at different energies, distinguishing the energy characteristics of neutrons from two sources: spontaneous fission and particle-induced neutrons; the neutron emissivity refers to the total number of neutrons released from the sample per unit time, which is the basic parameter for quantitative neutron calculation; the neutron multiplication leakage coefficient characterizes the proportional coefficient of neutron multiplication within the sample and leakage through the material, and is correlated with the equivalent mass and the measured neutron count.

[0041] In this embodiment of the invention, based on the plutonium isotope mass ratio and combined with the neutron energy spectrum and neutron emissivity parameters of the sample to be tested, multiple sets of working conditions are set up through Monte Carlo neutron transport simulation to perform simulation calculations, obtain the corresponding Pu-240 equivalent mass and neutron multiplication leakage coefficient data under different working conditions, and construct the corresponding correlation formula between the two through data fitting processing.

[0042] Step S105: Substitute the measured total neutron count and neutron multiplication leakage coefficient of the sample to be tested into the relational formula to calculate the equivalent mass of plutonium-240.

[0043] It should be noted that the measured total neutron count refers to the cumulative count of neutrons actually emitted outward from the sample, as collected by the neutron detector; the neutron multiplication leakage coefficient describes the proportion of neutrons that leak outward after multiplying within the material; and the plutonium-240 equivalent mass is the equivalent mass of a single Pu-240 corresponding to the total neutron contribution of all even-numbered plutonium nuclides in the sample.

[0044] In this embodiment of the invention, the total neutron count of the sample under test is obtained by measurement. Combined with the neutron multiplication leakage coefficient corresponding to the constructed relation, the two types of measured and simulation parameters are substituted into the correlation relation for solution calculation, and the Pu-240 equivalent mass of the sample under test is accurately calculated.

[0045] Step S106: Combine the plutonium isotope mass ratio with the plutonium-239 mass and the plutonium-240 equivalent mass respectively to obtain two sets of initial plutonium isotope masses, and perform averaging to determine the target mass of plutonium isotopes.

[0046] It should be noted that averaging refers to calculating the arithmetic mean of the two initial masses corresponding to the same nuclide to offset the systematic errors of the two detection methods; the target mass of plutonium isotopes refers to the final quantitative mass value of various plutonium nuclides obtained after mean correction.

[0047] In this embodiment of the invention, using the plutonium isotope mass ratio, and combining the Pu-239 mass obtained by the gamma spectroscopy method and the Pu-240 equivalent mass obtained by the neutron method, two complete sets of initial plutonium isotope mass data are obtained. The two sets of initial mass data are then subjected to mean calibration to offset the systematic error of a single detection method, and finally, a high-precision plutonium isotope target mass is determined.

[0048] This embodiment provides a method for measuring the mass of plutonium in a container. Figure 3 This is a flowchart of a method for measuring the mass of plutonium in a container according to an embodiment of the present invention, as shown below. Figure 3 As shown, the process includes the following steps: Step S201: Based on gamma spectroscopy, the plutonium isotope mass ratio in the sample is calculated using the area, branching ratio, and relative detection efficiency of the gamma peaks in the sample.

[0049] In some optional implementations, step S201 above includes: Step S2011: Input the gamma energy spectrum of the sample to be tested into the gamma spectroscopy analysis software and determine the energy scale and resolution.

[0050] It should be noted that energy calibration refers to calibrating the correspondence between the energy spectrum channel address and the radiation energy using the characteristic radiation energy of a standard source, thereby achieving energy spectrum energy calibration.

[0051] In embodiments of the present invention, such as Figure 1 As shown, determining the mass ratio of plutonium isotopes is crucial for the final mass calculation. The analysis process includes: inputting the gamma spectrum and determining the energy scale and resolution; determining the gamma peak shape function and calculating the gamma peak area; calculating the relative detection efficiency and relative activity; and calculating the relative and absolute proportions of the nuclides. The specific calculation process for inputting the gamma spectrum and determining the energy scale and resolution is as follows: Energy calibration involves scaling the entire spectrum based on the known energies of the gamma peaks to facilitate subsequent peak area calculations. The calibration is performed using formula (1), which determines the energy of the entire spectrum using two known gamma peaks. a and b The entire energy spectrum can be calibrated; the resolution is determined for peak shape fitting. The resolution is expressed as the full width at half maximum (FWHM), as shown in formula (2). FWHM is a function of energy. The fitting coefficient can be determined by measuring the full width at half maximum of three or more gamma peaks.

[0052]

[0053] In the formula, E It represents the gamma-ray energy, and CH is the number of detector channels. a b are coefficients; This represents the fitting coefficient.

[0054] Step S2012: Based on the fitting function corresponding to the energy scale and resolution, fit the peak shape of the gamma peak of the sample to be tested to generate the gamma peak shape function.

[0055] It should be noted that the gamma peak shape function refers to a special function that is generated based on the fitting function and adapted to the measured peak shape, and is used to solve for the peak area by integration.

[0056] In this embodiment of the invention, the calculation process for determining the gamma peak shape function is as follows: The peak shape is fitted using a fitting function, usually using formulas (3), (4) and (5) to obtain the gamma peak shape function.

[0057] The peak shape is fitted using a fitting function, typically formulas (3), (4), and (5). After determining the peak shape function, the area of ​​the gamma peak can be calculated using integration.

[0058]

[0059] In formula (3), Y(E i ) Indicates energy as E i Net count, H It is the peak height. It is the peak width parameter. E m Indicates peak value. E i This represents the energy at any position within the peak. Tail(E i ) It is the fitting function of the low-energy tail end; in formula (4),T i These are the fitting coefficients.

[0060] Step S2013: Calculate the area of ​​the corresponding gamma peak using the gamma peak shape function.

[0061] In this embodiment of the invention, after determining the shape function of the gamma peak, the area of ​​the gamma peak can be calculated using integration.

[0062] Step S2014: Using any gamma peak of the sample to be tested as a reference peak, calculate the relative detection efficiency of the gamma peak to be tested based on the area and branching ratio of the reference peak, the area and branching ratio of the gamma peak to be tested, and the relative activity between the reference peak and the gamma peak to be tested.

[0063] In specific embodiments, many factors affect the detection efficiency, including self-absorption, attenuation, geometry, and the detector itself. The detection efficiency of a certain gamma peak is shown in formula (6), where E is the peak efficiency. j The detection efficiency is the peak area divided by the source strength. The source strength is calculated by formula (7).

[0064] Measuring detection efficiency requires the use of standard samples or numerical simulations. However, it is difficult to prepare standard samples for complex radioactive materials, and the uncertainty of numerical simulation results is relatively large. Introducing relative detection efficiency can avoid these problems, that is, using a reference peak, the detection efficiency of other peaks relative to the reference peak is calculated. The formula for calculating relative detection efficiency is shown in (8). The advantage of relative detection efficiency is that it does not require absolute measurement of detection efficiency; the relative proportion of different nuclides can be calculated simply by the relative ratio between different peaks.

[0065]

[0066] In formula (6), This indicates that for an energy of E j The detection efficiency of gamma rays. It is a nuclide i The energy emitted is E j The area of ​​gamma rays, It is a nuclide i The energy emitted is E j The intensity of gamma rays.

[0067] In formula (7), N i Indicates nuclide i The number of atoms, T 1 / 2 It is the half-life. It is a nuclide i The emission energy is E j The branching ratio of the peak.

[0068] In formula (8), The energy is represented by E. j The relative detection efficiency of the gamma peak. It is the area of ​​the reference peak. It is the branching ratio of the reference peak. It is relative activity.

[0069] The relative detection efficiency of plutonium conforms to a mathematical model, as shown in formula (9). There is an iterative relationship between relative detection efficiency and relative activity. This invention continuously approximates the relative detection efficiency through prediction, fitting, optimization, and iteration.

[0070] Specifically, step S2014 above includes (i.e., the specific calculation process for the relative detection efficiency of plutonium is as follows): Step a1: Based on the gamma spectrum, the relative activity between the two nuclides is preset to a predetermined value.

[0071] It should be noted that the preset value set in this invention is 1.

[0072] In this embodiment of the invention, based on the gamma spectrum, with the activity of a certain nuclide as a reference, it is assumed that the relative activity between other nuclides and the reference nuclide is 1, and a detection efficiency is estimated, that is, the peak area divided by the branching ratio.

[0073] Step a2: Take any gamma peak of plutonium in the sample to be tested as the reference peak, and set the detection efficiency of the remaining gamma rays relative to the reference peak as the initial relative detection efficiency.

[0074] It should be noted that the reference peak refers to the characteristic gamma peak of any plutonium sample that can be selected as the metrological benchmark; the initial relative detection efficiency refers to the initial value of the detection efficiency of the ray to be measured calculated based on the preset activity.

[0075] In this embodiment of the invention, for multiple gamma peaks of the same nuclide (taking Pu-241 as an example), the gamma peak with the highest energy is used as a reference. The detection efficiency of the lower-energy gamma rays relative to the reference peak is the estimated relative detection efficiency (i.e., the initial relative detection efficiency).

[0076] Step a3: Fit the curve of the initial relative detection efficiency according to the preset fitting coefficients, and determine the optimized relative detection efficiency.

[0077] It should be noted that the optimized relative detection efficiency refers to the detection efficiency after curve fitting correction, eliminating the system bias caused by the initial calculation.

[0078] In this embodiment of the invention, the relative detection efficiency curve is fitted according to formula (9) to obtain the optimized relative detection efficiency.

[0079]

[0080] In the formula, The fitting coefficients are denoted as .

[0081] Step a4: Based on the optimized relative detection efficiency, calculate the relative activity of multiple gamma peaks for any nuclide, and average all the relative activities to obtain the average relative activity of the corresponding nuclide.

[0082] It should be noted that the average relative activity refers to the arithmetic mean of the activities corresponding to multiple characteristic gamma peaks of the same nuclide, which reduces the random error in single-peak measurement.

[0083] In this embodiment of the invention, the relative activity is calculated based on the optimized relative detection efficiency. The peak area can be represented by formula (10), where the relative activity of the nuclide multiplied by the branching ratio and the relative detection efficiency equals the peak area. According to this formula, the relative activity of a nuclide is obtained for each peak. For the same nuclide, all relative activities are averaged to obtain the final relative activity.

[0084]

[0085] In the formula, C(E) j ) indicates that the energy is j The area of ​​Gamma Peak, Ract i Indicates nuclide i Relative activity, Indicates nuclide i The energy of the launch is j The branching ratio of gamma rays, Indicates energy as j The relative detection efficiency of gamma rays. Indicates the area of ​​the reference peak. This indicates the branching ratio of the reference gamma rays.

[0086] Step a5: Calculate the new initial relative detection efficiency of the gamma peak to be tested according to the average relative activity, and then proceed to the step of fitting the curve of the initial relative detection efficiency according to the preset fitting coefficient to determine the optimized relative detection efficiency, until the final relative detection efficiency of the gamma peak to be tested is obtained.

[0087] It should be noted that the final relative detection efficiency refers to the stable detection efficiency obtained after multiple rounds of iterative convergence, which serves as the benchmark for isotope ratio calculation.

[0088] In this embodiment of the invention, based on the averaged relative activity, a new relative detection efficiency is calculated using formula (10). The new relative detection efficiency is used as the input for the next fitting. Steps a3-a5 are repeated until the fitting curve coincides with the value of the relative detection efficiency. By using this method, a sufficiently accurate relative detection efficiency curve can be obtained.

[0089] Step S2015: Based on the curves corresponding to the area, branching ratio, half-life, and relative detection efficiency of the gamma peak, calculate the relative and absolute proportions of each nuclide in the sample to be tested, and determine the mass ratio of plutonium isotopes in the sample to be tested.

[0090] It should be noted that half-life refers to the time required for the number of radioactive nuclei to decay to half of their original value, and is used for activity conversion correction.

[0091] In this embodiment of the invention, the relationship between the area of ​​the gamma peak and the number of nucleons is shown in formulas (6) and (7). The ratio of the number of nuclei of different nuclides is shown in formula (11). Taking a certain gamma peak as a reference, the detection efficiency is converted into relative detection efficiency, as shown in formula (12). Combining formula (12) with the relative detection efficiency curve, the relative ratio of the number of nuclei between different nuclides can be obtained, and the relative mass ratio between different nuclides can be further obtained according to the molar formula.

[0092] The mass of Pu-242 is very small and can be ignored for now. Assuming the sum of the masses of Pu-238, Pu-239, Pu-240, Pu-241, and Am-241 is 1, the absolute mass ratio of the Pu isotopes can be obtained. Then, the mass of Pu-242 is calculated using the empirical formula (13). After calculating the mass of Pu-242, the mass ratio of the plutonium isotopes is normalized again to obtain the final absolute mass ratio of the plutonium isotopes. In formula (13), i Nu ( i =238, 239, 240, 241, 242; Nu = Pu, Am) represents the absolute mass ratio of nuclides.

[0093]

[0094] In specific embodiments, the case model adopted by the present invention is as follows: Figure 4 As shown, a high-purity germanium detector was used to detect plutonium in the sample.

[0095] Pu isotopic mass / atomic number ratio calculation: The gamma spectrum of the sample to be tested is as follows Figure 5 As shown in Table 1, the gamma peaks were first selected and their areas were calculated. The peak areas were calculated using gamma spectral analysis software, and the calculated areas are shown in Table 1.

[0096] Table 1. Major Gamma Peak Information for Plutonium

[0097] The calculation of relative detection efficiency and relative activity is iterative. This invention uses the 208 keV gamma peak of Pu-241 as a reference peak to calculate the relative detection efficiency of other peaks. First, assuming a relative activity of 1 between nuclides, the relative detection efficiency is estimated. Then, a relative detection efficiency curve is fitted according to a mathematical model of relative detection efficiency. Finally, the relative activity is updated based on the relative detection efficiency curve. This process is repeated continuously to make the relative detection efficiency approximate the true result. The final relative detection efficiency curve is shown below. Figure 6 As shown in Table 2, the calculated relative detection efficiency results are very close to the reference results, with minimal error.

[0098] Table 2. Comparison of relative detection efficiency and reference results for gamma peaks

[0099] The mass ratio of nuclides can be calculated based on the area, relative detection efficiency curve, branching ratio, and average lifetime, as shown in Table 3. In the table, the nuclide with the largest relative error is Pu-242, at 7.109%. This is because Pu-242 emits almost no gamma rays, and the calculation was performed using only empirical formulas, leading to a larger error. Nuclides that emit more gamma rays have smaller relative errors.

[0100] Table 3. Comparison of plutonium isotope mass ratios and reference results

[0101] Step S202: Based on the mass ratio of plutonium isotopes, simulate and model multiple sets of gamma parameters of plutonium-239 to obtain the fitting curve of gamma peak area and plutonium-239 mass.

[0102] In a specific embodiment, Pu-239 has the largest mass and the highest gamma-ray intensity in the plutonium sample. The relationship between the mass of Pu-239 and the area of ​​a certain gamma peak is usually shown in formula (14), where the specific activity, detection efficiency, solid angle, self-absorption coefficient, and correction coefficient of the gamma rays are usually known. If the relationship curve between the gamma peak area and the mass can be obtained, it can guide the measurement.

[0103]

[0104] In the formula, C It refers to the gamma-ray count, i.e., the area of ​​the gamma peak. I It is the mass of Pu-239. Г It is the specific activity of gamma rays. ε It's about detection efficiency. Ω It is a solid angle. μ It is the self-absorption coefficient of gamma rays. F It is a correction factor.

[0105] This relationship curve can be established through numerical simulation. This invention uses the Monte Carlo particle transport method for simulation.

[0106] In some alternative implementations, step S202 above includes (i.e., the simulation process of the Monte Carlo particle transport method is as follows): Step S2021: Based on the mass ratio of plutonium isotopes, a geometric model of the sample to be tested and the detector is constructed using the Monte Carlo method.

[0107] It should be noted that the Monte Carlo method refers to a numerical simulation algorithm that simulates the gamma photon transport process based on the principle of random sampling; the geometric model refers to a digital simulation model that replicates the spatial arrangement of the sample under test and the detection device according to the actual size and material structure.

[0108] In this embodiment of the invention, the plutonium nuclide composition structure inside the sample is determined according to the plutonium isotope mass ratio of the sample to be tested. Then, the Monte Carlo simulation method is used to accurately build an integrated geometric simulation model that fits the real detection scenario according to the actual size, spatial position and structural parameters of the sample to be tested and the neutron detector.

[0109] Step S2022: Input the plutonium-239 gamma rays and the corresponding multiple gamma parameters into the geometric model to perform multiple sets of plutonium-239 mass simulation calculations, and obtain the gamma peak area corresponding to each set of simulation conditions.

[0110] It should be noted that gamma parameters refer to fundamental nuclear physics parameters used in simulation calculations, including gamma ray energy, decay branching ratio, and nuclide half-life.

[0111] In this embodiment of the invention, core gamma parameters such as Pu-239 characteristic gamma ray energy and decay branching ratio are imported into the constructed geometric model. By setting multiple sets of gradient Pu-239 mass parameters, batch simulation calculations are carried out to simulate the entire process of gamma ray generation, transport and detection. The characteristic gamma peak area data corresponding to each set of mass parameters are statistically analyzed and output.

[0112] Step S2023: Based on the plutonium-239 mass of each group and the corresponding gamma peak area, a fitting curve of gamma peak area and plutonium-239 mass is obtained.

[0113] In this embodiment of the invention, a suitable gamma peak is selected, the intensity of which needs to be sufficiently large to avoid being submerged by the Compton plateau. A point source is established, and Monte Carlo particle transport is performed, including: the simulation of the point source requires knowledge of the gamma rays and their intensity. The emitted gamma rays are an inherent property of plutonium isotopes, and their intensity is related to both the proportion and mass. The mass proportion of plutonium isotopes is obtained in step S201, but the mass is unknown. This method simulates multiple plutonium masses, calculates the area of ​​the gamma peak, and obtains a fitting curve between the gamma peak area and the Pu-239 mass.

[0114] Step S203: Combine the measured gamma peak area and the fitted curve to solve for the mass of plutonium-239.

[0115] In a specific embodiment, the mass calculation of Pu-239 is as follows: Before use, the detector's resolution for gamma rays needs to be determined. The detector's resolution is related to the full width at half maximum (FWHM) of the gamma rays and is calculated using formula (3). When performing numerical simulations using the Monte Carlo method, Gaussian broadening is used to simulate the detector's resolution.

[0116] Then, the gamma rays to be detected are determined; this invention uses 129 keV gamma rays emitted by Pu-239. Next, the Monte Carlo method is used for calculations. A simple case model used in this invention is as follows: Figure 4 As shown. The reaction cross-sections of the nuclides were obtained from the ENDF database. The activities of the radioactive materials in the source setup and the emissivity of each gamma ray were calculated according to Table 1.

[0117] Based on the nuclide mass ratio obtained in step S201, assuming multiple samples with different masses, a relationship is established between the mass of Pu-239 and the area of ​​the 129 keV gamma peak, as follows: Figure 7 As shown. According to Figure 7 The slope of the curve can be calculated, and the mass of the unknown sample Pu-239 can be deduced from the relationship between the slope and the area of ​​the gamma peak.

[0118] Step S204: Based on the neutron energy spectrum and neutron emissivity of the sample to be tested, and combined with the plutonium isotope mass ratio, construct the relationship between the equivalent mass of plutonium-240 and the neutron multiplication leakage coefficient.

[0119] This invention uses the total neutron count method to calculate the equivalent mass of Pu-240. The relationship between the total neutron count and the mass is shown in formula (15), where the total neutron count is the product of the neutron intensity, the leakage multiplication factor, and the detection efficiency. In the plutonium sample, Pu-240 has the highest neutron emissivity. Assuming that all neutrons are contributed by Pu-240, the corresponding mass is the equivalent mass of Pu-240.

[0120]

[0121] The calculation of the equivalent mass of Pu-240 involves three steps: first, determining the neutron energy spectrum and emissivity; then, fitting a curve of the equivalent mass of Pu-240 and the neutron multiplication leakage coefficient; and finally, calculating the equivalent mass of Pu-240 based on the fitted curve and the total neutron count of the sample.

[0122] In some optional implementations, step S204 above includes: Step S2041: Based on the Watt spectrum, determine the spontaneous fission energy spectrum of the plutonium sample.

[0123] It should be noted that the Watt spectrum is a classical empirical energy spectrum model that characterizes the energy distribution of neutrons produced by spontaneous fission; the spontaneous fission energy spectrum refers to the distribution of the number of neutrons with different energies generated when a plutonium sample undergoes spontaneous fission.

[0124] In this embodiment of the invention, the calculation of the neutron energy spectrum and emissivity is as follows: the neutron energy spectrum includes the fission energy spectrum (i.e., the spontaneous fission energy spectrum) and ( , n The energy spectrum of the fission reaction (i.e., particle-induced neutron reaction). Among them, the fission energy spectrum adopts the Watt spectrum.

[0125] Step S2042: Using the energy stopping power of a preset nuclide against an alpha particle of a preset energy and the cross section of the reaction between the preset energy alpha particle and the nuclide to produce energy neutrons, calculate the neutron yield at each energy.

[0126] It should be noted that alpha particles refer to the helium nuclei released during the decay of plutonium-based nuclides, which can react with the light nuclei of the matrix to produce neutrons; energy stopping power refers to the ability of the medium to deplete the energy of alpha particles per unit path, used to calculate the remaining energy of alpha particles; neutron yield refers to the average number of neutrons produced by a single alpha particle participating in the reaction.

[0127] In this embodiment of the invention, the invention is based on (α, n The reaction calculation program calculates the neutron yield at various energies, and the calculation formula is shown in (16):

[0128] In the formula, nuclide i neutron yield, Let Avogadro's constant be 1. It is the quality score. The mass number of the nuclide. nuclide i For energy The energy-suppressing ability of alpha particles. For energy The energy-suppressing ability of alpha particles. It is energy alpha particles and i Nuclear reactions produce energy of The cross-section of a neutron.

[0129] Step S2043: Combine the neutron yield at each energy level to determine the energy spectrum of the particle-induced neutron reaction.

[0130] It should be noted that the particle-induced neutron energy spectrum refers to the energy distribution curve of neutrons generated by alpha particles bombarding matrix nuclides.

[0131] In this embodiment of the invention, the combination of neutron yields at various energies can constitute (α, n The energy spectrum of the reaction.

[0132] Step S2044: Determine the neutron energy spectrum of the plutonium sample based on the spontaneous fission energy spectrum and the energy spectrum of the particle-induced neutron reaction.

[0133] In this embodiment of the invention, the neutron energy spectrum includes the fission energy spectrum (i.e., the spontaneous fission energy spectrum) and ( , n The energy spectrum of the reaction (i.e., particle-induced neutron reaction) is combined with the fission energy spectrum determined in the above steps and ( , n The energy spectra of the reaction are combined to obtain the neutron energy spectrum of Pu.

[0134] Step S2045: Determine the emission rate of the particle-induced neutron reaction based on the preset energy of the alpha particle and each nuclide.

[0135] It should be noted that the emission rate of particle-induced neutrons refers to the total number of neutrons generated by the alpha-induced reaction per unit time. The preset energy is the energy of the alpha particle.

[0136] In this embodiment of the invention, (α, n The energy spectrum and emissivity of the reaction are related to the energy of the alpha particle and the type of nuclide in the target nucleus. Therefore, based on the energy of the alpha particle and the type of nuclide in the target nucleus, we can know (α, n The emissivity of the reaction.

[0137] Step S2046: Extract the emission rate of spontaneous fission and combine it with the emission rate of particle-induced neutron reaction to determine the emission rate of the plutonium sample.

[0138] It should be noted that spontaneous fission emission rate refers to the number of neutrons released by spontaneous fission of nuclei per unit time.

[0139] In this embodiment of the invention, the emissivity of spontaneous fission is calculated based on the data in Table 4.

[0140] Table 4. Neutron Yield of Plutonium

[0141] The emissivity of spontaneous fission and (α, n The emissivity of Pu was determined by combining the emissivity of the reaction.

[0142] Step S2047: Based on the Monte Carlo method, the neutron energy spectrum, emissivity and plutonium isotope mass ratio of the plutonium sample are simulated, the curves of plutonium-240 equivalent mass and neutron multiplication leakage coefficient are fitted and the relationship is constructed.

[0143] In this embodiment of the invention, after determining the neutron energy spectrum and emissivity, Monte Carlo neutron transport simulation can be performed according to the mass ratio of the nuclides obtained from step S201. This invention intends to simulate samples of multiple densities, fit the curve of Pu-240 equivalent mass versus neutron multiplication leakage coefficient, and construct the relationship, as shown in formula (17).

[0144]

[0145] Step S205: Substitute the measured total neutron count and neutron multiplication leakage coefficient of the sample to be tested into the relational formula to calculate the equivalent mass of plutonium-240.

[0146] In this embodiment of the invention, after obtaining the curve of the neutron multiplication leakage coefficient, the equivalent mass of Pu-240 is calculated according to formula (18).

[0147]

[0148] In the formula, S It is the total neutron count rate. ε It is the detection efficiency, M L It is a multiplier leakage coefficient. G It is 1g 240 The number of fission cycles in the mass of Pu, where ν is the number of neutrons released in each fission. N α It is the ratio of (α,n) neutron emissivity to fission neutron emissivity. 240 Pu eff It is the Pu-240 equivalent mass. Where ε, G, ν, and a Since it is known, formula (18) becomes about 240 Pu eff The two linear equations in two variables can be obtained by solving them.

[0149] In a specific embodiment, the equivalent mass of Pu-240 is calculated as follows: First, it is necessary to determine the neutron energy spectrum and emissivity of the material. The main neutron sources for the plutonium sample include spontaneous fission and (α,n The spontaneous fission energy spectrum is usually simulated using the Watt spectrum, and the neutron emissivity of spontaneous fission is shown in Table 4. (α, n The neutron energy spectrum of the reaction is relatively complex. It consists of neutrons emitted from the reaction of alpha particles with light nuclei (including H, O, and C). The neutron energy spectrum is related to the energy and yield of the alpha particles and the nuclide of the light nuclei. The alpha particle yields of Pu isotopes are shown in Table 4. This invention uses (α, n Reaction simulation software calculates (α, n The neutron energy spectrum and emissivity of the reaction were obtained. (α, n The neutron energy spectrum of the reaction is as follows: Figure 8 As shown, each α decay produces approximately 4.20E-10 neutrons per unit time.

[0150] Next, based on the plutonium isotope composition, assuming the masses of multiple samples, Monte Carlo transport calculations were performed, and the fitted curves of the Pu-240 equivalent mass and the multiplication leakage coefficient were obtained, as shown below. Figure 9 As shown, there is a linear relationship between the multiplication leakage coefficient and the equivalent mass of Pu-240.

[0151] Finally, by using the total neutron count of the reference sample, the total neutron count of the unknown sample, and the multiplication leakage coefficient curve, the Pu-240 equivalent mass of the unknown sample can be deduced.

[0152] Step S206: Combine the plutonium isotope mass ratio with the plutonium-239 mass and the plutonium-240 equivalent mass respectively to obtain two sets of initial plutonium isotope masses, and perform averaging to determine the target mass of plutonium isotopes.

[0153] In some optional implementations, step S206 above includes: Step S2061: Calculate the first initial mass of each plutonium isotope using the plutonium isotope mass ratio and the mass of plutonium-239.

[0154] It should be noted that the first initial mass refers to the plutonium isotope mass of the entire composition calculated based on the plutonium-239 mass obtained from gamma measurements and the isotope ratio conversion, which is the quantitative result of gamma measurement.

[0155] In this embodiment of the invention, the masses of Pu-238, Pu-240, Pu-241, and Pu-242 can be calculated according to formula (19) based on the mass of Pu-239 calculated in step S203 and the plutonium isotope mass ratio calculated in step S201.

[0156]

[0157] In the formula, m( i Pu () indicates the mass of a Pu isotope.i Pu This indicates the mass ratio of Pu isotopes.

[0158] Step S2062: Calculate the second initial mass of each plutonium isotope using the plutonium isotope mass ratio and the equivalent mass of plutonium-240.

[0159] It should be noted that the second initial mass refers to the plutonium isotope mass of the entire composition calculated based on the plutonium-240 equivalent mass obtained by neutron measurement and the isotope ratio conversion, which is a quantitative result of neutron measurement.

[0160] In this embodiment of the invention, there is an empirical relationship between the equivalent mass of Pu-240 calculated according to step S205 and the masses of Pu-238, Pu-240 and Pu-242, as shown in formula (20). Combining the plutonium isotope mass ratio calculated in step S201, formula (20) can be converted into formula (21). k This represents the coefficient between mass and mass ratio. Solving for it... k The masses of Pu-238, Pu-240, and Pu-242 can then be calculated.

[0161]

[0162] In formula (20), m( i Pu ) represents the mass of the isotopes of Pu (i=238, 240, 242).

[0163] In formula (21), i Pu Indicates the mass ratio of Pu isotopes (i=238, 240, 242).

[0164] Step S2063: Average the first initial mass and the second initial mass of each plutonium isotope to determine the target mass of each plutonium isotope.

[0165] In this embodiment of the invention, the average mass of the two sets of masses in steps S2061 and S2062 is calculated to obtain the final mass of each isotope of plutonium.

[0166] In a specific embodiment, the Pu mass is calculated as follows: Once the isotopic ratios of plutonium, the mass of Pu-239, and the equivalent mass of Pu-240 are known, the mass of plutonium can be calculated. The calculation results are shown in Table 5 and... Figure 10 As shown, the largest error, at 7.70495%, comes from Pu-238, which is related to the relatively small mass of Pu-238. However, for nuclides with larger masses, the errors are all small and basically consistent with the reference results, meeting the accuracy requirements for nuclide measurement.

[0167] Table 5. Comparison of plutonium isotope masses and reference results

[0168] This embodiment also provides a device for measuring the plutonium mass in a container, which is used to implement the above embodiments and preferred embodiments; details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0169] This embodiment provides a device for measuring the mass of plutonium in a container, such as... Figure 11 As shown, it includes: The calculation module 301 is used to calculate the plutonium isotope mass ratio in the sample based on the gamma spectroscopy method, using the area of ​​the gamma peak, the branching ratio and the relative detection efficiency of the sample. Modeling module 302 is used to simulate and model multiple sets of gamma parameters of plutonium-239 based on the mass ratio of plutonium isotopes, and obtain the fitting curve of gamma peak area and plutonium-239 mass; Solver module 303 is used to solve for the mass of plutonium-239 by combining the measured gamma peak area and the fitted curve; Module 304 is used to construct a relationship between the equivalent mass of plutonium-240 and the neutron multiplication leakage coefficient based on the neutron energy spectrum and neutron emissivity of the sample under test, and in combination with the plutonium isotope mass ratio. Substitute module 305, which is used to substitute the measured total neutron count and neutron multiplication leakage coefficient of the sample to be tested into the relational formula to calculate the equivalent mass of plutonium-240; Module 306 is used to combine the plutonium isotope mass ratio with the plutonium-239 mass and the plutonium-240 equivalent mass, respectively, to obtain two sets of initial plutonium isotope masses, and then perform averaging to determine the target plutonium isotope mass.

[0170] In some alternative implementations, the computing module 301 includes: The input unit is used to input the gamma energy spectrum of the sample to be tested into the gamma spectroscopy analysis software to determine the energy scale and resolution; The fitting unit is used to fit the peak shape of the gamma peak of the sample under test based on the fitting function corresponding to the energy scale and resolution, and generate the gamma peak shape function. The area calculation unit is used to calculate the area of ​​the corresponding gamma peak using the gamma peak shape function; The detection efficiency calculation unit is used to calculate the relative detection efficiency of the gamma peak to be tested, taking any gamma peak of the sample to be tested as a reference peak, based on the area and branching ratio of the reference peak, the area and branching ratio of the gamma peak to be tested, and the relative activity between the reference peak and the gamma peak to be tested. The calculation ratio unit is used to calculate the relative and absolute proportions of each nuclide in the sample to be tested based on the curves corresponding to the area, branching ratio, half-life, and relative detection efficiency of the gamma peak, and to determine the mass ratio of plutonium isotopes in the sample to be tested.

[0171] In some alternative implementations, the detection efficiency calculation unit includes: A subunit is set up to pre-set the relative activity between two nuclides to a preset value based on the gamma energy spectrum. The reference sub-unit is used to take any gamma peak of plutonium in the sample to be tested as the reference peak, and the detection efficiency of the remaining gamma rays relative to the reference peak is set as the initial relative detection efficiency. The optimization subunit is used to fit the curve of the initial relative detection efficiency according to the preset fitting coefficients, and to determine the optimized relative detection efficiency. The averaging subunit is used to calculate the relative activity of multiple gamma peaks of any nuclide based on the optimized relative detection efficiency, and to average all the relative activities to obtain the average relative activity of the corresponding nuclide. The jump rotor unit is used to calculate the new initial relative detection efficiency of the gamma peak to be measured according to the average relative activity, and jump to execute the step of fitting the curve of the initial relative detection efficiency according to the preset fitting coefficient to determine the optimized relative detection efficiency, until the final relative detection efficiency of the gamma peak to be measured is obtained.

[0172] In some alternative implementations, the modeling module 302 includes: The building unit is used to build the geometric model of the sample to be tested and the detector based on the mass ratio of plutonium isotopes using the Monte Carlo method; The simulation unit is used to input plutonium-239 gamma rays and corresponding gamma parameters into the geometric model to perform multiple sets of plutonium-239 mass simulation calculations, and obtain the gamma peak area corresponding to each set of simulation conditions. The curve fitting unit is used to fit a curve between the gamma peak area and the plutonium-239 mass based on the mass of each group of plutonium-239 and the corresponding gamma peak area.

[0173] In some alternative implementations, construction module 304 includes: The energy spectrum determination unit is used to determine the spontaneous fission energy spectrum of a plutonium sample based on the Watt spectrum. The neutron yield calculation unit is used to calculate the neutron yield of a preset nuclide at a preset energy. The particle's energy-based stopping power and its preset energy Cross section of particle-nuclide reaction producing high-energy neutrons, calculate neutron yield at each energy; The combination unit is used to combine the neutron yield at various energies to determine the energy spectrum of particle-induced neutron reactions; The neutron energy spectrum determination unit is used to determine the neutron energy spectrum of plutonium samples based on the energy spectrum of spontaneous fission and the energy spectrum of particle-induced neutron reactions. Emissivity determination unit, used to determine the emissivity based on a preset energy. The emission rate of particle-induced neutron reactions was determined by the interaction of particles and nuclides. An extraction unit is used to extract the emissivity of spontaneous fission and, in combination with the emissivity of particle-induced neutron reactions, determine the emissivity of the plutonium sample. The simulation unit is used to simulate the neutron energy spectrum, emissivity, and plutonium isotope mass ratio of plutonium samples based on the Monte Carlo method, fit the curves of plutonium-240 equivalent mass and neutron multiplication leakage coefficient, and construct the relationship.

[0174] In some alternative implementations, the incorporation module 306 includes: The first calculation unit is used to calculate the first initial mass of each plutonium isotope using the plutonium isotope mass ratio and the mass of plutonium-239; The second calculation unit is used to calculate the second initial mass of each plutonium isotope using the plutonium isotope mass ratio and the equivalent mass of plutonium-240; The processing unit is used to average the first initial mass and the second initial mass of each plutonium isotope to determine the target mass of each plutonium isotope.

[0175] The plutonium mass measuring device in a container provided in this embodiment of the invention can execute the plutonium mass measuring method in a container provided in any embodiment of the invention, and has the corresponding functional modules and beneficial effects for executing the method. Further functional descriptions of the various modules and units described above are the same as in the corresponding embodiments described above, and will not be repeated here.

[0176] Figure 12 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention.

[0177] The following is a detailed reference. Figure 12This diagram illustrates a structural schematic suitable for implementing an electronic device according to embodiments of the present invention. The electronic device may include a processor (e.g., a central processing unit, graphics processor, etc.) 401, which can perform various appropriate actions and processes according to a program stored in read-only memory (ROM) 402 or a program loaded from memory 408 into random access memory (RAM) 403. The RAM 403 also stores various programs and data required for the operation of the electronic device. The processor 401, ROM 402, and RAM 403 are interconnected via a bus 404. An input / output (I / O) interface 405 is also connected to the bus 404.

[0178] Typically, the following devices can be connected to I / O interface 405: input devices 406 including, for example, touchscreens, touchpads, keyboards, mice, cameras, microphones, accelerometers, gyroscopes, etc.; output devices 407 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; memory devices 408 including, for example, magnetic tapes, hard disks, etc.; and communication devices 409. Communication device 409 allows electronic devices to communicate wirelessly or wiredly with other devices to exchange data. Although Figure 12 Electronic devices with various devices are shown, but it should be understood that it is not required to implement or have all of the devices shown, and more or fewer devices may be implemented or have instead.

[0179] In particular, according to embodiments of the present invention, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of the present invention include a computer program product comprising a computer program carried on a non-transitory computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via a communication device 409, or installed from a memory 408, or installed from a ROM 402. When the computer program is executed by the processor 401, it performs the functions defined in the method for measuring the plutonium mass in a container according to embodiments of the present invention.

[0180] Figure 12 The electronic device shown is merely an example and should not be construed as limiting the functionality and scope of use of the embodiments of the present invention.

[0181] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as recordable on a storage medium, or implemented as computer code originally stored on a remote storage medium or a non-transitory machine-readable storage medium and subsequently stored on a local storage medium after being downloaded via a network. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code. When the software or computer code is accessed and executed by the computer, processor, or hardware, the method for measuring the plutonium mass in a container shown in the above embodiments is implemented.

[0182] A portion of this invention can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to the invention through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0183] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for measuring the mass of plutonium in a container, characterized in that, The method includes: Based on gamma spectroscopy, the plutonium isotope mass ratio in the sample is calculated by using the area, branching ratio and relative detection efficiency of the gamma peak of the sample. Based on the mass ratio of the plutonium isotopes, multiple sets of gamma parameters of plutonium-239 were simulated and modeled to obtain fitting curves of gamma peak area and plutonium-239 mass. The mass of plutonium-239 was determined by combining the measured gamma peak area with the fitted curve. Based on the neutron energy spectrum and neutron emissivity of the sample to be tested, and in combination with the plutonium isotope mass ratio, a relationship between the equivalent mass of plutonium-240 and the neutron multiplication leakage coefficient is constructed. Substitute the measured total neutron count and neutron multiplication leakage coefficient of the sample to be tested into the relationship to calculate the equivalent mass of plutonium-240; The plutonium isotope mass ratios are combined with the plutonium-239 mass and the plutonium-240 equivalent mass to obtain two sets of initial plutonium isotope masses, which are then averaged to determine the target plutonium isotope mass.

2. The method according to claim 1, characterized in that, The method based on gamma spectroscopy calculates the plutonium isotope mass ratio in the sample by using the area, branching ratio, and relative detection efficiency of the gamma peaks. This includes: Input the gamma energy spectrum of the sample to be tested into the gamma spectroscopy analysis software to determine the energy scale and resolution; Based on the energy scale and the fitting function corresponding to the resolution, the peak shape of the gamma peak of the sample to be tested is fitted to generate a gamma peak shape function. The area of ​​the corresponding gamma peak is calculated using the gamma peak shape function; Using any gamma peak of the sample to be tested as a reference peak, the relative detection efficiency of the gamma peak to be tested is calculated based on the area and branching ratio of the reference peak, the area and branching ratio of the gamma peak to be tested, and the relative activity between the reference peak and the gamma peak to be tested. Based on the curves corresponding to the area, branching ratio, half-life, and relative detection efficiency of the gamma peak, the relative and absolute proportions of each nuclide in the sample to be tested are calculated, and the mass ratio of plutonium isotopes in the sample to be tested is determined.

3. The method according to claim 2, characterized in that, The step of using any gamma peak of the sample to be tested as a reference peak, and calculating the relative detection efficiency of the gamma peak to be tested based on the area and branching ratio of the reference peak, the area and branching ratio of the gamma peak to be tested, and the relative activity between the reference peak and the gamma peak to be tested, includes: Based on the gamma spectrum, the relative activity between the two nuclides is preset to a preset value; Using any gamma peak of plutonium in the sample to be tested as a reference peak, the detection efficiency of the remaining gamma rays relative to the reference peak is set as the initial relative detection efficiency. Based on preset fitting coefficients, fit the curve of the initial relative detection efficiency to determine the optimized relative detection efficiency; Based on the optimized relative detection efficiency, the relative activity of multiple gamma peaks of any nuclide is calculated, and all the relative activities are averaged to obtain the average relative activity of the corresponding nuclide. Based on the average relative activity, calculate the new initial relative detection efficiency of the gamma peak to be measured, and then proceed to the step of fitting the curve of the initial relative detection efficiency according to the preset fitting coefficient to determine the optimized relative detection efficiency, until the final relative detection efficiency of the gamma peak to be measured is obtained.

4. The method according to claim 1, characterized in that, The simulation modeling of multiple sets of gamma parameters of plutonium-239 based on the mass ratio of the plutonium isotopes, to obtain the fitting curve of gamma peak area and plutonium-239 mass, includes: Based on the mass ratio of the plutonium isotopes, a geometric model of the sample to be tested and the detector was constructed using the Monte Carlo method. The plutonium-239 gamma rays and corresponding gamma parameters are input into the geometric model to perform multiple sets of plutonium-239 mass simulation calculations, and the gamma peak area corresponding to each set of simulation conditions is obtained. Based on the plutonium-239 mass and the corresponding gamma peak area of ​​each group, a fitting curve of the gamma peak area and the plutonium-239 mass is obtained.

5. The method according to claim 1, characterized in that, The relationship between the equivalent mass of plutonium-240 and the neutron multiplication leakage coefficient is constructed based on the neutron energy spectrum and neutron emissivity of the sample under test, and in conjunction with the plutonium isotope mass ratio, including: Based on the Watt spectrum, the spontaneous fission energy spectrum of the plutonium sample was determined; Using a preset nuclide to a preset energy The particle's energy-stopping ability and the preset energy Cross section of particle-nuclide reaction producing high-energy neutrons, calculate neutron yield at each energy; By combining the neutron yield at each of the described energies, the energy spectrum of the particle-induced neutron reaction is determined; The neutron energy spectrum of the plutonium sample is determined based on the spontaneous fission energy spectrum and the energy spectrum of the particle-induced neutron reaction. According to the preset energy The particle and each of the aforementioned nuclides are used to determine the emission rate of the neutron-induced reaction of the particle; The emission rate of the spontaneous fission was extracted and combined with the emission rate of the particle-induced neutron reaction to determine the emission rate of the plutonium sample. Based on the Monte Carlo method, the neutron energy spectrum, emissivity and mass ratio of the plutonium isotopes of the plutonium sample were simulated, and the curves of the plutonium-240 equivalent mass and the neutron multiplication leakage coefficient were fitted and the relationship was constructed.

6. The method according to claim 1, characterized in that, The step of combining the plutonium isotope mass ratio with the plutonium-239 mass and the plutonium-240 equivalent mass respectively to obtain two sets of initial plutonium isotope masses, averaging them, and determining the target plutonium isotope mass includes: The initial mass of each plutonium isotope is calculated using the plutonium isotope mass ratio and the plutonium-239 mass. The second initial mass of each plutonium isotope is calculated using the plutonium isotope mass ratio and the equivalent mass of plutonium-240. The target mass of each plutonium isotope is determined by averaging the first initial mass and the second initial mass of each plutonium isotope.

7. A device for measuring the mass of plutonium in a container, characterized in that, The device includes: The calculation module is used to calculate the plutonium isotope mass ratio in the sample to be tested based on the gamma spectroscopy method, using the area of ​​the gamma peak, the branching ratio, and the relative detection efficiency of the sample to be tested. The modeling module is used to simulate and model multiple sets of gamma parameters of plutonium-239 based on the mass ratio of the plutonium isotopes, and obtain the fitting curve of gamma peak area and plutonium-239 mass. The solution module is used to calculate the mass of plutonium-239 by combining the measured gamma peak area and the fitted curve. A construction module is used to construct a relationship between the equivalent mass of plutonium-240 and the neutron multiplication leakage coefficient based on the neutron energy spectrum and neutron emissivity of the sample to be tested, and in combination with the mass ratio of the plutonium isotopes. The substitution module is used to substitute the measured total neutron count and neutron multiplication leakage coefficient of the sample to be tested into the relationship to calculate the equivalent mass of plutonium-240; The module is used to combine the plutonium isotope mass ratio with the plutonium-239 mass and the plutonium-240 equivalent mass respectively to obtain two sets of initial plutonium isotope masses, and then perform averaging to determine the target plutonium isotope mass.

8. An electronic device, characterized in that, include: A memory and a processor are communicatively connected, the memory storing computer instructions, and the processor executing the computer instructions to perform the method for measuring the plutonium mass in a container as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing a computer to perform the method for measuring the plutonium mass in the container according to any one of claims 1 to 6.

10. A computer program product, characterized in that, Includes computer instructions for causing a computer to perform a method for measuring the mass of plutonium in a container as described in any one of claims 1 to 6.

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