A spectrum optimization method for efficient irradiation production of plutonium-238 based on extreme burnup analysis

Abstract

The present invention relates to a plutonium-238 efficient irradiation production method based on an extreme value burnup analysis method, comprising the following steps: S1: modeling a reactor, an irradiation channel and a target to obtain a high-flux reactor model; S2: dividing a full energy zone into a plurality of energy intervals based on the high-flux reactor model; S3: using an extreme value burnup analysis method to calculate the energy zone efficiency factor of each energy zone, thereby determining the optimal neutron energy spectrum for irradiating and producing plutonium-238 in a reactor; S4: using an efficiency factor curve calculated by the extreme value burnup analysis method to guide energy spectrum optimization, thereby improving the production efficiency of plutonium-238. Compared with the prior art, the present invention quantifies the irradiation production efficiency of plutonium-238 in different energy zones based on the extreme value burnup analysis method, and optimizes the neutron energy spectrum by dispersing specific nuclides in the target, thereby significantly improving the irradiation production efficiency of plutonium-238.

Description

Technical Field

[0001] The invention relates to the technical field of plutonium-238 irradiation production, and in particular to an energy spectrum optimization method for plutonium-238 efficient irradiation production based on an extreme burnup analysis method. Background Art

[0002] Pu-238 is an ideal heat source isotope, widely used in industry, agriculture, medicine and other fields. However, the production of Pu-238 by irradiation in a reactor faces the problems of low production efficiency and high production cost. It is necessary to carry out relevant research to improve the production efficiency of Pu-238. Summary of the invention

[0003] Aiming at the low efficiency of the existing irradiation production of plutonium-238 in reactors, a spectrum optimization method for efficient irradiation production of plutonium-238 based on extreme burnup analysis is proposed. This method quantifies the irradiation production efficiency of plutonium-238 in different energy regions based on the extreme burnup analysis method, and optimizes the neutron spectrum by diffusing specific nuclides in the target, thereby significantly improving the irradiation production efficiency of plutonium-238.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] The present invention provides an energy spectrum optimization method for plutonium-238 efficient irradiation production based on an extreme burnup analysis method, comprising the following steps:

[0006] S1: Model the reactor, irradiation channel and target to obtain a high-flux reactor model;

[0007] S2: Based on the high flux reactor model, the omnipotent region is divided into several energy intervals;

[0008] S3: Use the extreme burnup analysis method to calculate the energy efficiency factor of each energy region, so as to determine the optimal neutron energy spectrum for irradiation production of plutonium-238 in the reactor;

[0009] S4: Use the efficiency factor curve calculated using the extreme burnup analysis method to guide energy spectrum optimization, thereby improving the production efficiency of Pu-238.

[0010] Furthermore, in S1, the reactor, irradiation channel and target are modeled using the Monte Carlo program RMC.

[0011] Further, in S3, the extreme value burnup analysis method is specifically:

[0012] The perturbation burnup method or the single energy burnup method is used to establish the relationship between the plutonium-238 yield and the irradiation time, denoted as Y i (x), in order to eliminate the influence of irradiation time on yield, the yield Yi The derivative of (x) with respect to x The maximum value of i , to quantify the plutonium-238 production efficiency in the i-th energy region.

[0013] Furthermore, in S3, the perturbation burnup method is: divide the full energy area into several energy intervals, reduce the neutron flux in each energy area one by one, observe the effect of the reduction of the neutron flux in each energy area on the plutonium-238 yield, and record it as the importance Among them I i represents the importance of the i-th energy region, Y and Y i are the plutonium-238 production before and after the neutron flux reduction in the i-th energy group, ΔY i is the change in the plutonium-238 yield before and after the neutron flux is reduced in the i-th energy group, φ i and φ i ′ are the neutron fluxes in the energy zone before and after the flux reduction, respectively, and the subscript i is the serial number of the energy zone.

[0014] Further, in S3, the importance of irradiation time x days is calculated by the perturbation burnup method, so as to establish the relationship between plutonium-238 yield and irradiation time, that is, Y i (x).

[0015] Furthermore, in S3, the single energy burnup method is: divide the full energy area into several energy intervals, ensure that the total neutron flux remains unchanged in the burnup calculation, assume that a single energy neutron source with energy in the i-th energy zone is arranged in the irradiation channel one by one, and calculate and determine the plutonium-238 yield of the target after x days of irradiation by the single energy neutron source, that is, Yi(x).

[0016] Furthermore, in S3, the energy efficiency factor E i It is calculated in the following way: Determine the plutonium-238 production efficiency E in the i-th energy zone based on the extreme burnup analysis method i , E i The value is the energy zone efficiency factor of the i-th energy zone.

[0017] Furthermore, S3 also includes maximizing the total efficiency of the energy spectrum. The specific process is: searching for the target nuclide in the nuclear database, the total cross section of the nuclide with the energy distribution is inversely proportional to the optimal neutron energy spectrum, arranging the nuclide around the irradiation channel or dispersing it in the target. At this time, the nuclide is in E i The smaller energy range has a larger total cross section, which increases the macroscopic total cross section in the energy range, thereby reducing the neutron flux in the energy range. iA smaller total cross-section is provided in a larger energy zone, which reduces the macroscopic total cross-section of the energy zone, thereby increasing the neutron flux in the energy zone, thereby maximizing the total efficiency of the energy spectrum, optimizing the energy spectrum at the irradiation channel, and significantly improving the production efficiency of plutonium-238.

[0018] Furthermore, in S3, the distribution of the total nuclide cross section with energy is inversely proportional to the optimal neutron energy spectrum and is approximated by the following method:

[0019] calculate Among them, T i is the total energy-related cross section of a nuclide, E i is the energy zone efficiency factor of the i-th energy zone, N is the total number of divided energy zones, and if a nuclide can achieve T maximization, it is considered to be the optimal nuclide required for energy spectrum optimization.

[0020] Furthermore, in S3, the total energy spectrum efficiency and the corresponding plutonium-238 yield are obtained as follows:

[0021] Based on the formula The total energy spectrum efficiency E of each irradiation scheme is calculated, and the Monte Carlo burnup method is used to calculate the actual yield of plutonium-238 of each irradiation scheme.

[0022] Compared with the prior art, the present invention has the following technical advantages:

[0023] The present invention can quantify the plutonium-238 production efficiency in each energy range when plutonium-238 is produced by irradiation in a reactor based on the extreme burnup analysis method, thereby effectively supporting the optimization of plutonium-238 irradiation production. At the same time, based on the energy spectrum optimization technology, the "total energy spectrum efficiency" is maximized, thereby significantly improving the production efficiency of plutonium-238 produced by irradiation in the reactor, solving the problem of low production efficiency of traditional methods, and establishing a refined neutronics model for the production of plutonium-238 by reactor irradiation, providing technical support for achieving efficient plutonium-238 production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic flow chart of the plutonium-238 high-efficiency irradiation production method based on the extreme burnup analysis method in the present invention;

[0025] Figure 2 A schematic diagram of modeling the reactor and irradiation channel of an embodiment;

[0026] Figure 3 The energy zone importance curves of different irradiation durations calculated based on the “perturbation burnup method”;

[0027] Figure 4 It is the energy zone yield curve of different irradiation times calculated based on the “single energy burnup method”;

[0028] Figure 5 It is the energy zone efficiency factor curve determined based on the “extreme burnup analysis method”;

[0029] Figure 6 This is the relationship curve between the total energy spectrum efficiency and the actual plutonium-238 production. DETAILED DESCRIPTION

[0030] The invention discloses a plutonium-238 high-efficiency irradiation production method based on an extreme value burnup analysis method. The method divides the total energy area into several energy intervals, defines an "energy zone efficiency factor" to quantify the plutonium-238 irradiation production efficiency in different energy zones, and uses an extreme value burnup analysis method to calculate the "energy zone efficiency factor" of each energy zone, thereby determining the optimal neutron energy spectrum for irradiating and producing plutonium-238 in a reactor. Then, the "energy spectrum total efficiency" is defined to quantify the production efficiency of a certain irradiation scheme, and the energy spectrum optimization technology is used to maximize the "energy spectrum total efficiency", thereby significantly improving the production efficiency of plutonium-238.

[0031] The "extreme value burnup analysis method" means that in order to quantify the plutonium-238 production efficiency in the i-th energy zone, the perturbation burnup method or the single energy burnup method is used to establish the relationship between the plutonium-238 production and the irradiation time, which is denoted as Y i (x), in order to eliminate the influence of irradiation time on yield, the yield Y i The derivative of (x) with respect to x The maximum value of i , to quantify the plutonium-238 production efficiency in the i-th energy region.

[0032] The "perturbation burnup method" mentioned above means: dividing the total energy area into several energy intervals, reducing the neutron flux in each energy interval one by one, observing the effect of the reduction of neutron flux in each energy interval on the plutonium-238 production, and recording the importance Among them I i represents the importance of the i-th energy region, Y and Y i are the plutonium-238 production before and after the neutron flux reduction in the i-th energy group, ΔY i is the change in the plutonium-238 yield before and after the neutron flux is reduced in the i-th energy group, φ i and φ i ′ are the neutron fluxes of the energy zone before and after the flux reduction, respectively, and the subscript i is the serial number of the energy zone. Obviously, the irradiation time will affect the importance. The "perturbation burnup method" can calculate the importance when the irradiation time is x days, thereby establishing the relationship between the plutonium-238 yield and the irradiation time, that is, Y i (x).

[0033] The "single energy burnup method" is to divide the full energy area into several energy intervals, ensure that the total neutron flux remains unchanged in the burnup calculation, assume that a single energy neutron source with energy in the ith energy zone is arranged in the irradiation channel one by one, and calculate and determine the plutonium-238 yield of the target after x days of irradiation by the single energy neutron source, that is, Y i (x).

[0034] The "energy efficiency factor E i ” It is calculated in the following way: Determine the plutonium-238 production efficiency E in the i-th energy zone based on the extreme burnup analysis method i , this value is the “energy zone efficiency factor” of the i-th energy zone.

[0035] The "spectrum optimization technology" mentioned above refers to: searching for a certain nuclide in the nuclear database, the total cross section of which is inversely proportional to the optimal neutron spectrum with the energy distribution, arranging the nuclide around the irradiation channel or dispersing it in the target. i The smaller energy range has a larger total cross section, which increases the macroscopic total cross section in the energy range, thereby reducing the neutron flux in the energy range. i The larger energy zone has a smaller total cross-section, which reduces the macroscopic total cross-section of the energy zone, thereby increasing the neutron flux in the energy zone, thereby maximizing the "total energy spectrum efficiency", optimizing the energy spectrum at the irradiation channel and significantly improving the production efficiency of plutonium-238.

[0036] The above-mentioned “the distribution of total nuclide cross section with energy is inversely proportional to the optimal neutron energy spectrum” cannot be realized in actual production. The following strategy is used to approximate it: Calculate Among them, T i is the total energy-related cross section of a nuclide, E i is the energy zone efficiency factor of the ith energy zone, and N is the total number of divided energy zones. If a nuclide can achieve T maximization, it is considered to be the optimal nuclide required for the “energy spectrum optimization technology”.

[0037] The “total energy spectrum efficiency E” is specifically calculated by the following formula: Where N is the total number of energy zones, φ i is the neutron flux in the ith energy region, E i is the energy zone efficiency factor of the i-th energy zone.

[0038] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms and other features not clearly described in this technical solution are all considered to be common technical features disclosed in the prior art.

[0039] Example 1

[0040] like Figure 1 As shown, a plutonium-238 efficient irradiation production method based on an extreme burnup analysis method according to this embodiment includes the following steps:

[0041] Step 1): The reactor, irradiation channel and target are modeled using the Monte Carlo program RMC. Figure 2 The typical high flux reactor model shown is implemented in FIG.

[0042] Step 2): Based on this model, perturbation burnup calculation and single energy burnup calculation are carried out, in which the full energy region is divided into 238 energy regions in total to ensure high resolution of energy spectrum analysis.

[0043] In order to investigate the effect of irradiation time on the perturbation burnup calculation and the single energy burnup calculation, the irradiation durations were selected to be 5, 10, and 90 days. The energy zone importance curves of different irradiation durations based on the perturbation burnup method were calculated (see Figure 3 ) and the energy zone yield curves for different irradiation times based on the single energy burnup method (see Figure 4 ).

[0044] from Figure 3 and Figure 4 It can be seen that the irradiation duration has a great influence on the energy zone importance curve and the energy zone yield curve, and the energy zone importance calculated when the irradiation duration is 90 days is significantly lower than the energy zone importance obtained when the irradiation duration is 5 days and 10 days. Therefore, when the irradiation duration is 90 days, there is an over-irradiation problem, that is, after the yield of plutonium-238 in the target reaches its peak, continued irradiation will lead to a decrease in the yield of plutonium-238.

[0045] In order to compare the perturbation burnup method with the single energy burnup method, Table 1 shows the top 10 maximum and top 10 minimum values ​​in the energy zone importance curve and the energy zone yield curve, as well as their corresponding energy zones.

[0046] Table 1. The top 10 maximum and top 10 minimum values ​​in the energy zone importance curve and energy zone yield curve.

[0047]

[0048]

[0049] As can be seen from Table 1, the overall trend of the energy zone importance curve and the energy zone yield curve is in good agreement. Among the 10 energy zones corresponding to the maximum values, 8 are corresponding, indicating that the two methods play a similar role in searching for positive energy zones (energy zones that are beneficial to production). However, only 3 of the 10 energy zones corresponding to the minimum values ​​are corresponding, indicating that the two methods are different in searching for negative energy zones (energy zones that are harmful to production). This is because the physical assumptions of the perturbation burnup method and the single energy burnup method are different. The calculation results of the perturbation burnup method are based on a specific energy spectrum environment, while the single energy burnup method does not depend on a specific energy spectrum environment. Moreover, the perturbation burnup method calculates the importance, and its calculation results can take negative values, while the single energy burnup method calculates the output, and its calculation results can only be positive.

[0050] Step 3): In order to eliminate the influence of irradiation time on the energy zone importance curve and energy zone yield curve, extreme value burnup analysis was carried out based on the data obtained from the perturbation burnup calculation with an irradiation time of 90 days and the data obtained from the single energy burnup calculation, and two sets of energy zone efficiency factor curves were calculated, see Figure 5 .

[0051] from Figure 5 It can be seen that the two sets of energy zone efficiency factors are in good agreement, that is, no matter whether the perturbation burnup method or the single energy burnup method is used to calculate the plutonium-238 production efficiency in each energy zone, the extreme value burnup analysis method can obtain energy zone efficiency factors with actual physical significance.

[0052] Step 4): Use the efficiency factor curve calculated by the extreme burnup analysis method to guide the energy spectrum optimization, thereby improving the production efficiency of plutonium-238. Different energy spectrum environments are constructed by arranging a certain nuclide around the irradiation channel or dispersing the nuclide in the target, and the total energy spectrum efficiency and corresponding plutonium-238 production under these different energy spectrum environments are calculated.

[0053] The nuclides selected in this embodiment include: Ag107, Ar40, Ba140, Dy161, Eu151, Eu152, Eu153, Gd157, H1, He4, La138, Li7, Ni64, Pd108, Sm147, Sm151, Ti49, Tm170, W186. The amount of nuclides added can be 1.0×10 1 , 1.0×10 0 , 1.0×10 -1 , 1.0×10 -2 , 1.0×10 -3 , 1.0×10 -4 and 1.0×10 -5 , the unit is (10 24 # / cm3 ).

[0054] Based on the formula The total energy spectrum efficiency E of each irradiation scheme is calculated by using the Monte Carlo burnup method to calculate the actual plutonium-238 production of each irradiation scheme. The specific layout schemes, the changes in the total energy spectrum efficiency of these schemes, and the corresponding changes in the plutonium-238 production are shown in Table 2. The relationship curve between the change in the total energy spectrum efficiency and the change in the actual plutonium-238 production is constructed, see Figure 6 .

[0055] from Figure 6 It can be seen that the change in total energy spectrum efficiency is positively correlated with the actual change in plutonium-238 production. The correlation coefficient between total energy spectrum efficiency and actual plutonium-238 production is 0.949. This proves the correctness and feasibility of the plutonium-238 high-efficiency irradiation production method based on extreme burnup analysis method.

[0056] Table 2. Arrangement schemes in energy spectrum optimization.

[0057]

[0058] 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 the energy spectrum of plutonium-238 high-efficiency irradiation production based on extreme burnup analysis method, characterized in that: The following steps are involved: S1: Model the reactor, irradiation channel and target to obtain a high-flux reactor model; S2: Based on the high flux reactor model, the omnipotent region is divided into several energy intervals; S3: Use the extreme burnup analysis method to calculate the energy efficiency factor of each energy region, so as to determine the optimal neutron energy spectrum for irradiation production of plutonium-238 in the reactor; S4: Use the efficiency factor curve calculated by the extreme burnup analysis method to guide energy spectrum optimization, thereby improving the production efficiency of Pu-238; In S1, the Monte Carlo code RMC was used to model the reactor, irradiation channel, and target; In S3, the energy efficiency factor E i It is calculated in the following way: Determine the plutonium-238 production efficiency E in the i-th energy zone based on the extreme burnup analysis method i , E i The value is the energy zone efficiency factor of the i-th energy zone; S3 also includes maximizing the total efficiency of the energy spectrum. The specific process is: search for the target nuclide in the nuclear database. The total cross section of the nuclide is inversely proportional to the optimal neutron energy spectrum with the energy distribution. The nuclide is arranged around the irradiation channel or dispersed in the target. At this time, the nuclide is in E i The smaller energy range has a larger total cross section, which increases the macroscopic total cross section in the energy range, thereby reducing the neutron flux in the energy range. i The larger energy range has a smaller total cross section, which reduces the macroscopic total cross section of the energy range, thereby increasing the neutron flux in the energy range, thereby maximizing the total efficiency of the energy spectrum, optimizing the energy spectrum at the irradiation channel, and significantly improving the production efficiency of plutonium-238; In S3, the extreme value burnup analysis method is specifically as follows: The perturbation burnup method or the single energy burnup method is used to establish the relationship between the plutonium-238 yield and the irradiation time, denoted as Y i (x), in order to eliminate the influence of irradiation time on yield, the yield Y i The derivative of (x) with respect to x The maximum value of i , to quantify the plutonium-238 production efficiency in the i-th energy region; In S3, the distribution of the total nuclide cross section with energy is inversely proportional to the optimal neutron energy spectrum and is approximated by the following method: calculate , where T i is the total energy-related cross section of a nuclide, E i is the energy zone efficiency factor of the i-th energy zone, N is the total number of divided energy zones, if a nuclide can achieve T maximization, then it is considered to be the best nuclide required for energy spectrum optimization; The perturbation burnup method is: divide the whole energy area into several energy intervals, reduce the neutron flux in each energy area one by one, observe the effect of the reduction of neutron flux in each energy area on the plutonium-238 production, and record it as importance , where I i represents the importance of the i-th energy region, Y and Y i are the plutonium-238 production before and after the neutron flux is reduced in the i-th energy group, is the change in the plutonium-238 yield before and after the neutron flux is reduced in the i-th energy group, and are the neutron fluxes in the energy zone before and after the flux reduction, respectively, and the subscript i is the serial number of the energy zone; In S3, the single energy burnup method is: divide the full energy area into several energy intervals, ensure that the total neutron flux remains unchanged in the burnup calculation, assume that a single energy neutron source with energy in the i-th energy zone is arranged in the irradiation channel one by one, and calculate and determine the plutonium-238 yield of the target after x days of irradiation by the single energy neutron source, that is, Yi(x).

2. The energy spectrum optimization method for efficient irradiation production of plutonium-238 based on extreme burnup analysis method according to claim 1 is characterized in that: In S3, the importance of irradiation time x days is calculated by the perturbation burnup method, so as to establish the relationship between plutonium-238 production and irradiation time, that is, Y i (x).

3. The energy spectrum optimization method for efficient irradiation production of plutonium-238 based on extreme burnup analysis method according to claim 1 is characterized in that: In S3, the total energy spectrum efficiency and the corresponding plutonium-238 production are obtained as follows: Based on the formula The total energy spectrum efficiency E of each irradiation scheme is calculated, and the Monte Carlo burnup method is used to calculate the actual yield of plutonium-238 of each irradiation scheme.

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