Neutron energy spectrum optimization method and system for improving reactor radioisotope production efficiency

Abstract

The invention relates to a neutron energy spectrum optimization method and system for improving reactor radioisotope production efficiency, and the method comprises the following steps: randomly generating an initial population of a genetic algorithm, the population individuals being neutron energy spectrums divided into n energy groups, and calculating the volume average neutron energy spectrum in the target when the neutron energy spectrum of each individual is used as the incident energy spectrum of the irradiation pore channel, calculating the radioactive isotope yield under the volume average neutron energy spectrum in the target corresponding to each individual, realizing population evolution through variation and crossover operation of a genetic algorithm, and repeatedly executing the process until iterative convergence to obtain the radioactive isotope yield of the target. And a neutron energy spectrum regulation and control scheme for maximizing the yield of radioactive isotopes is obtained. Compared with the prior art, accurate regulation and control of the neutron energy spectrum of the reactor are efficiently realized, and technical support can be provided for the energy spectrum regulation and control process of irradiation production of radioactive isotopes in the reactor.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear reactor design, and in particular to a neutron spectrum optimization method and system for improving the production efficiency of reactor radioactive isotopes. Background Art

[0002] The neutron spectrum has a significant impact on the production efficiency of radioisotopes produced by irradiation in the reactor. Regulating the neutron spectrum in the irradiation channel can effectively improve the efficiency of the reactor in producing radioisotopes. Traditional reactor neutron spectrum regulation methods face the defects of narrow controllable energy range, low spectrum resolution, low regulation accuracy and poor universality of the method, making it difficult to effectively improve the efficiency of radioisotope production by irradiation in the reactor. Summary of the invention

[0003] The purpose of the present invention is to provide a neutron spectrum optimization method and system for improving the production efficiency of reactor radioisotopes, thereby improving the production efficiency of reactor radioisotopes.

[0004] The object of the present invention can be achieved by the following technical scheme: A neutron spectrum optimization method for improving the production efficiency of reactor radioisotopes comprises the following steps:

[0005] The initial population of the genetic algorithm is randomly generated. The individuals in these populations are all neutron energy spectra divided into n energy groups. The neutron energy spectrum of each individual is calculated as the volume average neutron energy spectrum in the target when the neutron energy spectrum of the irradiation channel is used. The radioactive isotope yield under the volume average neutron energy spectrum in the target corresponding to each individual is calculated. The evolution of the population is achieved through the mutation and crossover operations of the genetic algorithm. The above process is repeated until the iteration converges to obtain a neutron energy spectrum control scheme that maximizes the radioactive isotope yield.

[0006] Preferably, the full energy region is divided into n energy groups, and the Monte Carlo method is used to calculate the probability of energy transfer between energy groups after a nuclear reaction between neutrons and m nuclides, thereby constructing m n×n matrices, which are called energy spectrum response matrices;

[0007] Based on the energy spectrum response matrix, the volume average neutron energy spectrum in the target corresponding to each volume neutron energy spectrum is obtained as the incident energy spectrum of the irradiation channel.

[0008] Further preferably, the volume average neutron energy spectrum in the target is calculated by the following formula:

[0009] φ1=R·φ2;

[0010] Where: φ1 is the volume average neutron energy spectrum in the target, φ2 is the incident energy spectrum of the irradiation channel, and R is the weighted energy spectrum response matrix of multiple nuclides in the target;

[0011] in,

[0012] Where: K is the number of nuclides contained in the target, R i is the energy spectrum response matrix of the i-th nuclide in the target, F i is the nuclear reaction proportion of the i-th nuclide in the target, that is, the ratio of the total cross section of the nuclide to the total cross section of the target.

[0013] Preferably, the radioactive isotope yield under the volume average neutron energy spectrum in the target corresponding to each body is obtained by performing the ignition consumption calculation.

[0014] Further preferably, the ignition consumption calculation refers to solving the ignition consumption equation:

[0015]

[0016] Where: n i is the density of the ith nuclide; λ i eff is the effective attenuation coefficient of the ith nuclide; λ j eff is the effective attenuation coefficient of the jth nuclide; b i,j eff is the branching ratio of the i-th nuclide into the j-th nuclide;

[0017] Among them, the λ i eff and b i,j eff Calculated by the following formula:

[0018]

[0019] Where: i is the decay constant of the ith nuclide; Ψ is the neutron flux density; σ i,j is the single group microscopic cross section of the nuclear reaction of the i-th nuclide to produce the j-th nuclide; b i,j is the branching ratio of the i-th nuclide after decaying to the j-th nuclide; λ i is the decay constant of the ith nuclide;

[0020] Based on σ i,j According to the neutron energy spectrum compression and grouping, the single group macroscopic cross section Σ required for ignition consumption calculation is obtained r :

[0021]

[0022] Where: subscript p represents the number of the energy group, σ r,p is the microscopic cross section of reaction type r in the pth energy group, φ prepresents the normalized neutron energy spectrum, that is, the neutron flux density of the pth energy group after normalization.

[0023] In the present invention, n i Represents the radioactive isotope yield, Ψ corresponds to the volume average neutron energy spectrum φ1 in the target, and the volume average neutron energy spectrum φ1 in the target can be obtained after Ψ is normalized.

[0024] Preferably, the neutron energy spectrum optimization method for improving the production efficiency of reactor radioactive isotopes also includes dispersing a plurality of nuclides in the target to obtain different energy spectrum response matrices.

[0025] Further preferably, multiple nuclides are diffused in the target to obtain a weighted energy spectrum response matrix R of multiple nuclides in different targets.

[0026] Preferably, the iteration convergence condition is that the relative deviation of the isotope yields of the previous and next generations is less than 0.0001.

[0027] Preferably, based on a neutron spectrum control scheme that can maximize the yield of radioactive isotopes, nuclides are diffused in the target to be optimized to improve the efficiency of reactor radioactive isotope production.

[0028] Preferably, the neutron spectrum optimization method for improving the efficiency of reactor radioisotope production comprises the following steps:

[0029] Step 1: Construct a neutron energy spectrum fast response module, divide the full energy region into n energy groups, and use the Monte Carlo method to count the probability of energy transfer between energy groups after a nuclear reaction between neutrons and m nuclides, thereby constructing m n×n matrices, called energy spectrum response matrices, which describe the energy transfer relationship when a nuclear reaction occurs between various nuclides and neutrons. For a large number of neutron nuclear reaction processes, the response relationship between neutron energy spectra is macroscopically manifested, so that the neutron energy spectrum can be quickly calculated by iteratively solving the formula φ1=R·φ2.

[0030] Where: φ1 is the volume average neutron energy spectrum in the target, φ2 is the incident energy spectrum of the irradiation channel, and R is the weighted energy spectrum response matrix of multiple nuclides in the target, which is given by Calculated.

[0031] Where: K is the number of nuclides contained in the target, R i is the energy spectrum response matrix of the i-th nuclide in the target, F i is the nuclear reaction proportion of the i-th nuclide in the target, that is, the ratio of the total cross section of the nuclide to the total cross section of the target.

[0032] Step 2: Construct a neutron spectrum control module. In order to convert the incident neutron spectrum of the irradiation channel into a neutron spectrum that is beneficial to the production of radioactive isotopes, thereby placing the target in an optimal neutron spectrum environment, the present invention achieves neutron spectrum control by diffusing various nuclides in the target to obtain different spectrum response matrices.

[0033] Step 3: Construct a radioactive isotope yield calculation module. Based on the neutron energy spectrum control module, a variety of neutron energy spectra can be obtained. At this time, by performing the ignition consumption calculation, the radioactive isotope yield under the neutron energy spectrum can be obtained, and the efficiency of the neutron energy spectrum for radioactive isotope production can be evaluated.

[0034] The ignition consumption calculation is to solve the ignition consumption equation:

[0035]

[0036] In the above formula, n i is the density of the ith nuclide; λ i eff is the effective attenuation coefficient of the ith nuclide; b i,j eff is the branching ratio of the i-th nuclide to the j-th nuclide; where λ i eff and b i,j eff Calculated by the following formula:

[0037]

[0038] λ i is the decay constant of the ith nuclide; Ψ is the neutron flux density; σ i,j is the single-group microscopic cross section for the nuclear reaction of the ith nuclide to produce the jth nuclide, based on σ i,j According to the neutron energy spectrum compression and grouping, the single group macroscopic cross section Σ required for ignition consumption calculation can be obtained. r :

[0039]

[0040] Where: subscript p represents the number of the energy group, σ r,p is the microscopic cross section of reaction type r in the pth energy group, φ p represents the normalized neutron energy spectrum, that is, the neutron flux density of the pth energy group after normalization.

[0041] Step 4: Construct an intelligent optimization module. First, randomly generate the initial population of the genetic algorithm. The individuals in these populations are all neutron energy spectra divided into n energy groups. Then, use the neutron energy spectrum rapid response module to calculate these neutron energy spectra as the volume average neutron energy spectra in the target when the neutron energy spectra are used as the incident energy spectra of the irradiation channel. Then, use the radioactive isotope yield calculation module to evaluate the efficiency of the neutron energy spectrum for radioactive isotope production. Finally, through the mutation and crossover operations of the genetic algorithm, the evolution of the population is realized. Repeat the above process until the iteration converges to obtain the neutron energy spectrum control scheme that maximizes the radioactive isotope yield.

[0042] A system for implementing the above neutron spectrum optimization method, comprising:

[0043] A neutron energy spectrum rapid response module for calculating the volume average neutron energy spectrum in the target when each volume neutron energy spectrum is used as the incident energy spectrum of the irradiation channel;

[0044] A radioisotope yield calculation module for calculating the radioisotope yield under the volume average neutron energy spectrum in the target corresponding to each body;

[0045] A neutron energy spectrum control module for obtaining different energy spectrum response matrices;

[0046] And a genetic algorithm optimization module (intelligent optimization module) for obtaining a neutron spectrum control scheme for maximizing radioactive isotope production.

[0047] The present invention aims at the defects of the traditional reactor neutron spectrum control method, such as narrow controllable energy range, low spectrum resolution, low control accuracy and poor universality of the method, and proposes a method for precise control of the neutron spectrum in the full energy domain. The method first constructs a neutron spectrum rapid response module to realize the rapid calculation of the neutron spectrum; then constructs a neutron spectrum control module to obtain various neutron spectra by diffusing various spectrum-shifted nuclides in the target; then constructs a radioactive isotope yield calculation module to calculate the yield of radioactive isotopes under various neutron energy spectra using an ignition consumption algorithm; finally, constructs an intelligent optimization module and uses a genetic algorithm to connect the above modules in series to obtain a neutron spectrum control scheme that maximizes the yield of radioactive isotopes. The present invention can provide technical support for the spectrum control process of producing radioactive isotopes by irradiation in a reactor.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. The present invention provides a method for improving the efficiency of producing radioactive isotopes by irradiation in a reactor by regulating the neutron energy spectrum in the full energy range.

[0050] 2. The present invention solves the problems of narrow controllable energy range, low energy spectrum resolution, low control accuracy and poor universality of the traditional reactor neutron energy spectrum control method.

[0051] 3. Compared with the traditional method, the present invention can realize neutron spectrum control in the whole energy range, and there is no restriction on the energy group division in the control process, and a very high energy spectrum resolution can be achieved. The genetic algorithm is used to achieve optimization, and the accuracy of neutron spectrum control is improved. At the same time, the method does not introduce theoretical assumptions and approximations, and has universal applicability. The present invention efficiently realizes the precise control of the reactor neutron spectrum, and can provide technical support for the spectrum control process of producing radioactive isotopes by irradiation in the reactor.

[0052] 4. The present invention proposes a reactor neutron spectrum control technology, which improves the production efficiency of reactor radioactive isotopes by constructing a neutron spectrum rapid response module, a neutron spectrum control module, a radioactive isotope production calculation module and an intelligent optimization module. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a flow chart of Embodiment 1 of the present invention;

[0054] Figure 2 A simplified geometric diagram of the High Flux Isotope Reactor (HFIR). DETAILED DESCRIPTION

[0055] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0056] A neutron spectrum optimization method for improving the efficiency of reactor radioisotope production, such as Figure 1 As shown, the following steps are included:

[0057] S1: Randomly add various nuclides to the target;

[0058] S2: Initialize / update the genetic algorithm population;

[0059] S3: Determine the energy spectrum response matrix corresponding to each individual;

[0060] S4: Calculate the volume average neutron flux of each target corresponding to each individual;

[0061] S5: Calculate the single group cross section required for ignition consumption calculation;

[0062] S6: Calculate the radioisotope yield corresponding to each individual;

[0063] S7: Determine whether the evolution is finished. When the iterative convergence condition is met, output the best energy spectrum control scheme. When the iterative convergence condition is not met, return to step S2 and repeat the above process.

[0064] Example 1

[0065] by Figure 2 The production of transuranic isotopes in the high flux isotope reactor shown in FIG. The reactor and the transuranic isotope production scheme based on the reactor are currently the best schemes in the world.

[0066] The target nuclide composition of the reactor to produce californium-252 is shown in Table 1. The target produced californium-252 after 25 days of HFIR irradiation, with a yield of 1.33×10 18 Atom / cm 3 .

[0067] Table 1. Target nuclide composition for producing californium-252 in HFIR reactor

[0068]

[0069] This embodiment uses the present invention to optimize the local neutron spectrum of producing californium-252 in the HFIR reactor. The specific implementation process is shown in Figure 1 .

[0070] This embodiment constructs energy transfer matrices of 423 nuclides for spectrum control, wherein the size of each energy transfer matrix is ​​238 × 238. Therefore, the neutron spectrum rapid response module can realize rapid calculation of neutron spectrum of 238 energy groups under 423 nuclide ratios.

[0071] When using the genetic algorithm to search for the best neutron spectrum control scheme, the population size in each generation is 400, and the population evolves for a total of 400 generations. During the evolution process, the crossover rate of the population is 20% and the mutation rate is 20%.

[0072] The target nuclide composition in Table 1 is the nuclide ratio of the initial population, and the total density of the initial nuclides is 5.52×10 22 Atom / cm 3 In the subsequent genetic algorithm optimization process, the target volume average neutron energy spectrum was changed by diffusing these 423 nuclides (excluding nuclides with atomic mass > 350) in the target, and the total density of the diffused nuclides was 5.52×10 20 Atom / cm 3 Therefore, the genetic algorithm needs to search and determine the nuclide ratio for adding these 423 nuclides.

[0073] This embodiment uses the Reactor Monte Carlo program RMC to perform the ignition consumption calculation. The program was developed by Tsinghua University and is currently a well-known reactor physics calculation program in the world.

[0074] The spectrum optimization scheme is achieved by dispersing the nuclide ratio shown in Table 2 in the target. At this time, the yield of californium-252 is 1.49×10 18 Atom / cm 3 , the production of californium-252 increased by 12.16%.

[0075] Table 2. Target nuclide ratios required for the spectrum optimization scheme for producing californium-252 in HFIR reactor

[0076]

[0077] It can be seen that the present invention can improve the production efficiency of californium-252 by optimizing the neutron energy spectrum, and the neutron energy spectrum regulation process only requires dispersing some nuclides in the target, without modifying the design parameters of the reactor or the irradiation channel, and has the advantages of being simple and feasible.

[0078] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for optimizing neutron energy spectrum for improving the production efficiency of radioactive isotopes in a reactor, characterized in that: The following steps are involved: The initial population of the genetic algorithm is randomly generated. The individuals in these populations are all neutron energy spectra divided into n energy groups. The neutron energy spectrum of each individual is calculated as the volume average neutron energy spectrum in the target when the neutron energy spectrum of the irradiation channel is used. The radioactive isotope yield under the volume average neutron energy spectrum in the target corresponding to each individual is calculated. The evolution of the population is achieved through the mutation and crossover operations of the genetic algorithm. The above process is repeated until the iteration converges to obtain a neutron energy spectrum control scheme that maximizes the radioactive isotope yield.

2. The neutron spectrum optimization method for improving the production efficiency of reactor radioisotopes according to claim 1, characterized in that: The full energy region is divided into n energy groups, and the Monte Carlo method is used to calculate the probability of energy transfer between energy groups after a nuclear reaction between neutrons and m nuclides, thereby constructing m n×n matrices, called energy spectrum response matrices; Based on the energy spectrum response matrix, the volume average neutron energy spectrum in the target corresponding to each volume neutron energy spectrum is obtained as the incident energy spectrum of the irradiation channel.

3. The neutron spectrum optimization method for improving the production efficiency of reactor radioisotopes according to claim 2, characterized in that: The volume average neutron energy spectrum in the target is calculated by the following formula: φ1=R·φ2; Where: φ1 is the volume average neutron energy spectrum in the target, φ2 is the incident energy spectrum of the irradiation channel, and R is the weighted energy spectrum response matrix of multiple nuclides in the target; in, Where: K is the number of nuclides contained in the target, R i is the energy spectrum response matrix of the i-th nuclide in the target, F i is the nuclear reaction proportion of the i-th nuclide in the target, that is, the ratio of the total cross section of the nuclide to the total cross section of the target.

4. The neutron spectrum optimization method for improving the production efficiency of reactor radioisotopes according to claim 1, characterized in that: The radioactive isotope yield under the volume average neutron energy spectrum in the target corresponding to each body is obtained by performing the ignition consumption calculation.

5. The neutron spectrum optimization method for improving the production efficiency of reactor radioactive isotopes according to claim 4, characterized in that: The ignition consumption calculation refers to solving the ignition consumption equation: Where: n i is the density of the ith nuclide; is the effective attenuation coefficient of the ith nuclide; is the effective attenuation coefficient of the jth nuclide; is the branching ratio of the i-th nuclide into the j-th nuclide; Among them, the and Calculated by the following formula: Where: i is the decay constant of the ith nuclide; Ψ is the neutron flux density; σ i,j is the single group microscopic cross section of the nuclear reaction of the i-th nuclide to produce the j-th nuclide; b i,j is the branching ratio of the i-th nuclide after decaying to the j-th nuclide; λ i is the decay constant of the ith nuclide; Based on σ i,j According to the neutron energy spectrum compression and grouping, the single group macroscopic cross section Σ required for ignition consumption calculation is obtained r : Where: subscript p represents the number of the energy group, σ r,p is the microscopic cross section of reaction type r in the pth energy group, φ p represents the normalized neutron energy spectrum, that is, the neutron flux density of the pth energy group after normalization.

6. The neutron spectrum optimization method for improving the production efficiency of reactor radioisotopes according to claim 1, characterized in that: The method also includes diffusing a variety of nuclides in the target to obtain different energy spectrum response matrices.

7. The neutron spectrum optimization method for improving the production efficiency of reactor radioactive isotopes according to claim 6, characterized in that: A variety of nuclides are diffused in the target, and a weighted energy spectrum response matrix R of the multiple nuclides in different targets is obtained.

8. The neutron spectrum optimization method for improving reactor radioisotope production efficiency according to claim 1, characterized in that: The iteration convergence condition is that the relative deviation of the isotope yields of the previous and next generations is less than 0.0001.

9. The neutron spectrum optimization method for improving the production efficiency of reactor radioisotopes according to claim 1, characterized in that: Based on a neutron spectrum control scheme that can maximize the yield of radioactive isotopes, nuclides are diffused in the target to be optimized.

10. A system for implementing the neutron spectrum optimization method according to any one of claims 1 to 9, characterized in that: include: A neutron energy spectrum rapid response module for calculating the volume average neutron energy spectrum in the target when each volume neutron energy spectrum is used as the incident energy spectrum of the irradiation channel; A radioactive isotope yield calculation module for calculating the radioactive isotope yield under the volume average neutron energy spectrum in the target corresponding to each body; A neutron energy spectrum control module for obtaining different energy spectrum response matrices; and a genetic algorithm optimization module for obtaining a neutron spectrum control scheme that maximizes radioisotope production.

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