Spent fuel assembly arrangement method and device and dry storage container

Abstract

The embodiment of the invention provides an arrangement method and device for spent fuel assemblies and a dry-process storage container, and the arrangement method comprises the following steps: carrying out radial partitioning on the dry-process storage container to obtain a plurality of storage areas, and pre-arranging each spent fuel assembly on the plurality of storage areas; arranging all the pre-arranged spent fuel assemblies for the first time according to a preset rule on the basis of the weight factors; and adjusting and arranging the corresponding spent fuel assemblies for the second time based on the burnup distribution of the fuel rods in different directions in the spent fuel assemblies. According to the embodiment of the invention, through two-time optimized arrangement, on the premise that the dry-method storage container meets the critical safety and thermotechnical safety limits, the burnup of each storage area of the spent fuel assembly in the dry-method storage process is more uniform; the problems that in the dry-method storage process of a dry-method storage container, burnup of a peripheral local area is excessively concentrated, and the radiation source item is too large are solved.

Description

Technical Field

[0001] This invention relates to the field of dry storage of spent fuel assemblies, and more particularly to a method, apparatus and container for arranging spent fuel assemblies. Background Technology

[0002] In the field of nuclear energy utilization, the safe storage of spent fuel assemblies is a crucial aspect of ensuring the safe operation of nuclear facilities. Dry storage containers, with their high efficiency, flexibility, and safety, have become the industry's primary choice for long-term spent fuel storage. Within dry storage containers, the arrangement of spent fuel assemblies directly affects the container's safety, space utilization, and radiation protection effectiveness.

[0003] Currently, existing methods for arranging spent fuel assemblies typically involve first dividing the storage container into zones, and then using the lumped parameter method to calculate the decay heat and radiation source intensity of the spent fuel assemblies based on their initial enrichment, average burnup, and cooling time. The corresponding spent fuel assemblies are then arranged according to their decay heat and radiation source intensity.

[0004] However, the burnup, decay heat, and radiation source intensity of spent fuel assemblies determined by the lumped parameter method do not have a spatial (gradient) distribution. This cannot reflect the differences in burnup, decay heat, and radiation source terms of each fuel rod in the spent fuel assembly with respect to location. This can easily lead to the problem of excessive burnup concentration in local areas, which reduces the overall service life of the storage container and increases the risk of safety accidents caused by excessive burnup concentration in the spent fuel assembly. Summary of the Invention

[0005] This invention provides a method, apparatus, and dry storage container for arranging spent fuel assemblies, aiming to solve the problem that existing arrangement schemes are prone to excessive concentration of fuel consumption in local areas.

[0006] In a first aspect, embodiments of the present invention provide a method for arranging spent fuel assemblies, applied to a dry storage container, comprising:

[0007] The dry storage container is radially partitioned to obtain multiple storage areas, and each spent fuel assembly is pre-arranged in each of the multiple storage areas;

[0008] Based on all pre-arranged spent fuel assemblies, obtain the surface dose rate contribution of the dry storage container and confirm the weighting factor of the spent fuel assemblies located at the preset storage positions in each of the storage areas.

[0009] Based on the weighting factor, all pre-arranged spent fuel assemblies are arranged for the first time according to predetermined rules.

[0010] The radial burnup distribution of each spent fuel assembly in one of the storage areas after pre-arrangement is obtained, and the radial burnup distribution of each spent fuel assembly located at a preset arrangement position in each of the storage areas after the first arrangement is obtained. Based on each radial burnup distribution, the corresponding spent fuel assembly is arranged a second time.

[0011] Secondly, embodiments of the present invention provide an arrangement apparatus for spent fuel assemblies, applied to a dry storage container, comprising:

[0012] A pre-arrangement unit is used to radially partition the dry storage container to obtain multiple storage areas, and to pre-arrange each spent fuel assembly in each of the multiple storage areas;

[0013] The weighting factor confirmation unit is used to obtain the surface dose rate contribution of the dry storage container based on all pre-arranged spent fuel assemblies, and to confirm the weighting factor of the spent fuel assembly located at the preset storage position in each of the storage areas.

[0014] The first arrangement unit is used to arrange all the pre-arranged spent fuel assemblies for the first time according to the weighting factor and a predetermined rule.

[0015] The second arrangement unit is used to obtain the radial burnout distribution of each spent fuel assembly in one of the storage areas after pre-arrangement and to obtain the radial burnout distribution of each spent fuel assembly located at a preset arrangement position in each of the storage areas after the first arrangement, and to perform a second arrangement of the corresponding spent fuel assembly according to each radial burnout distribution.

[0016] Thirdly, embodiments of the present invention provide a dry storage container, including the arrangement of spent fuel assemblies as described above.

[0017] This invention provides a method, apparatus, and dry storage container for arranging spent fuel assemblies. The method includes radially partitioning the dry storage container to obtain multiple storage areas, and pre-arranging each spent fuel assembly in each of the multiple storage areas; performing a first arrangement of all pre-arranged spent fuel assemblies according to predetermined rules based on a weighting factor; and performing a second arrangement of the corresponding spent fuel assemblies based on the burnup distribution of fuel rods in different orientations within the spent fuel assemblies. Through these two optimized arrangements, this invention ensures that the dry storage container, while meeting critical safety and thermal safety limits, achieves more uniform burnup across storage areas during dry storage, thus solving the problems of excessive burnup concentration and excessively large radiation source terms in peripheral local areas during dry storage. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the pre-arranged layout;

[0020] Figure 2 A schematic flowchart illustrating a method for arranging spent fuel assemblies according to an embodiment of the present invention;

[0021] Figure 3 This is a comparative schematic diagram of the prior art and embodiments of the present invention after arrangement;

[0022] Figure 4 The axial power distribution curve of the spent fuel assembly;

[0023] Figure 5 The radial power distribution of the spent fuel assembly;

[0024] Figure 6 This is a schematic diagram illustrating the classification of dry storage containers in practical applications.

[0025] Figure 7 This is a schematic diagram of a sub-process of a method for arranging spent fuel assemblies according to an embodiment of the present invention;

[0026] Figure 8 This is a schematic block diagram of a spent fuel assembly arrangement device provided in an embodiment of the present invention. Detailed Implementation

[0027] 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, not all, of the embodiments of the present invention. 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.

[0028] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0029] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0030] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0031] The core equipment for dry storage of spent fuel assemblies in pressurized water reactor nuclear power plants (PWRs) mainly consists of a storage container (DSC), a transfer container (TC), and a concrete storage unit module (HSM). The storage container provides structural support, criticality control, sealing constraints, and an inert environment for the spent fuel assemblies; the transfer container moves the storage container containing the spent fuel assemblies to the storage area; and the concrete module provides heat dissipation, shielding, and environmental protection during storage.

[0032] The AFA series fuel assemblies for pressurized water reactor nuclear power plants are 17×17 array structures (reference). Figure 5 The AFA series spent fuel assemblies consist of 264 fuel rods, 24 guide tubes, and 1 instrument tube, all assembled within a supporting structure. During dry storage of AFA series spent fuel assemblies, critical safety, thermal safety requirements, and radiation protection optimization must be met under normal, transient, and accident conditions. The loading arrangement of the storage containers varies depending on the source term characteristics of the spent fuel assemblies. These source term characteristics are primarily determined by initial enrichment, burnup, and cooling time. Even with the same initial enrichment, differences in burnup and cooling time affect the heat and radiation sources of the spent fuel assemblies. Thermal safety and radiation shielding are related to the fission products and derivative decays of the fission reaction, and are mainly determined by the burnup and cooling time of the spent fuel.

[0033] Depending on the initial enrichment, average burnup, and cooling time of the spent fuel assemblies, existing technologies typically use the lumped parameter method to calculate the decay heat and radiation source intensity of the AFA series spent fuel assemblies, as detailed in Table 1:

[0034] Table 1. List of spent fuel assemblies to be loaded into dry storage containers

[0035]

[0036]

[0037] As shown in Table 1, the burnup, decay heat, and radiation source intensity of the spent fuel assembly determined by the lumped parameter method do not have a spatial (gradient) distribution and do not reflect the differences in burnup, decay heat, and radiation source terms of the 264 fuel rods in the spent fuel assembly with respect to their location.

[0038] Furthermore, the loading and arrangement scheme for the AFA series spent fuel assemblies in the dry off-site storage of pressurized water reactor nuclear power plants mainly considers the constraints of critical safety, thermal safety, and radiation protection optimization. The functional requirements, technical indicators, and design limits for the spent fuel assemblies loaded in the dry storage containers are shown in Table 2. Among them, the radiation shielding performance must meet the design limits while also following the principle of reasonable, feasible, and as low as possible (ALARA).

[0039] Table 2 Technical Specifications of Dry Storage Arrangement Scheme for Spent Fuel Assemblies

[0040]

[0041]

[0042] The layout of AFA spent fuel dry storage containers generally includes two schemes: uniform layout and zoned layout. Specific examples are as follows: Figure 1 When the dry-process spent fuel storage containers are arranged uniformly, the total heat load limit of the storage containers is 35.2 kW, corresponding to a maximum decay heat of 1.1 kW for each spent fuel assembly; when a zoned arrangement is adopted, the storage containers are divided into three zones from the inside out (i.e., Figure 1 The light blue (Zone I), reddish brown (Zone II), and yellow (Zone III) areas represent the three zones. The maximum decay heat of spent fuel assemblies arranged in the middle area - reddish brown (Zone II) is 1.3 kW, and the maximum decay heat of spent fuel assemblies arranged in other areas - light blue (Zone I) and yellow (Zone III) is 1.1 kW. The total heat load limit of the storage container is 37.6 kW.

[0043] Based on existing technology, this invention optimizes the arrangement of spent fuel assemblies. For details, please refer to [link / reference needed]. Figure 2 This invention provides a method for arranging spent fuel assemblies, applied to a dry storage container, including steps S10-S40:

[0044] S10. The dry storage container is radially partitioned to obtain multiple storage areas, and each spent fuel assembly is pre-arranged in multiple storage areas respectively;

[0045] In this step, because dry storage containers are typically large and complex in structure, it is necessary to radially partition the container during the arrangement of spent fuel assemblies. Without partitioning, directly arranging the spent fuel assemblies would make it difficult to consider factors such as radiation distribution and heat dissipation conditions at different locations within the storage container. By radially partitioning the dry storage container into multiple storage areas, the space within the container can be managed more precisely. This allows each storage area to be tailored to its location characteristics (such as distance from the container surface), enabling the targeted arrangement of spent fuel assemblies with different properties.

[0046] The pre-arrangement of each spent fuel assembly across multiple storage areas serves as a preliminary planning process for their placement. This allows for subsequent optimization based on the initial locations. Furthermore, the pre-arrangement enables preliminary observation of the distribution of each spent fuel assembly across different storage areas, assessing their impact on the overall performance of the storage container (such as surface dose rate and burnup distribution). This provides data support for the subsequent first arrangement based on weighting factors and the second arrangement based on burnup distribution, allowing for further adjustments to the spent fuel assembly locations and achieving a safer and more efficient placement of spent fuel assemblies within the dry storage container.

[0047] Since the embodiments of the present invention are optimized based on existing technology, the radial partitioning in this step is the same as the partitioning method used in the prior art, and the pre-layout process is the same as the prior art's lumped parameter method. Specifically, S10 includes:

[0048] Obtain the number of storage chambers in the dry storage container;

[0049] Based on the number of storage chambers and the critical safety and thermal safety conditions during the storage process of the dry storage container, all storage chambers are divided into at least three storage areas arranged from the inside out: a first storage area, a second storage area, and a third storage area. The number of storage chambers in the first storage area is less than the number of storage chambers in the second storage area, and the number of storage chambers in the second storage area is less than the number of storage chambers in the third storage area.

[0050] The characteristic parameters of all spent fuel assemblies to be stored are obtained, and the assemblies are screened according to the characteristic parameters. The screened spent fuel assemblies are then pre-arranged in multiple storage areas.

[0051] In this embodiment, based on the safety requirements (criticality, thermal, and radiation protection) of spent fuel assemblies during dry storage, the characteristic parameters of the spent fuel assemblies are determined: initial enrichment, burnup, and cooling time. A spent fuel assembly can be represented by a pair of numbers: (initial enrichment, burnup, cooling time). For example, the spent fuel assembly with serial number 1 in Table 1 can be represented as YQ0191 (4.45%, 44443, 11.2), where YQ0174 represents the assembly number. Next, the number of storage compartments in the dry storage container is obtained (32 in this embodiment). Based on the number of storage compartments in the dry storage container and the critical safety and thermal safety limits of the spent fuel assemblies during dry storage, the radial partitioning of the storage compartments in the dry storage container is determined. The radial partitioning of the dry storage container is as follows: Figure 1 The system is divided into at least three radial zones: the first storage zone, the second storage zone, and the third storage zone (also known as Zone I, Zone II, and Zone III), which are represented by light blue (Zone I), reddish-brown (Zone II), and yellow (Zone III) from the inside out. The number of storage cells in each zone is 4 in light blue (Zone I), 12 in reddish-brown (Zone II), and 16 in yellow (Zone III).

[0052] Obtain the characteristic parameters (initial enrichment, burnup and cooling time) of all spent fuel assemblies to be stored, determine the range of spent fuel assemblies to be screened based on the characteristic parameters, select the appropriate number and storage conditions of spent fuel assemblies, and place them in storage chambers of multiple storage areas in a pre-arranged manner for storage.

[0053] In one embodiment, characteristic parameters of all spent fuel assemblies to be stored are obtained, and the assemblies are screened according to the characteristic parameters. The screened spent fuel assemblies are then pre-arranged in multiple storage areas, including:

[0054] If all spent fuel assemblies to be stored have the same initial enrichment, then the spent fuel assemblies that meet the safety conditions and parameter limits are selected.

[0055] Obtain the maximum decay heat of all screened spent fuel assemblies. If the maximum decay heat is less than a first predetermined value, then directly arrange them in the first storage area, the second storage area, and the third storage area.

[0056] If the maximum decay heat is greater than a first predetermined value and less than a second predetermined value, then the spent fuel assembly with the first burnup and first cooling time is arranged in the first storage area, the spent fuel assembly with the second burnup and second cooling time is arranged in the second storage area, and the spent fuel assembly with the third burnup and third cooling time is arranged in the third storage area, wherein the number of storage cells in the first storage area is less than the number of storage cells in the second storage area, and the number of storage cells in the second storage area is less than the number of storage cells in the third storage area.

[0057] In this embodiment, all spent fuel assemblies to be stored are screened and each spent fuel assembly is compared. If all spent fuel assemblies to be stored have the same initial enrichment, then spent fuel assemblies that meet the safety conditions and parameter limits are screened. The safety conditions can refer to the critical safety and thermal safety in Table 2, and the parameter limits can refer to the design limits in Table 2. The radial partitioning of the screened spent fuel assemblies and each storage cell in the dry storage container is used to further determine the range of initial enrichment, burnup and cooling time of the spent fuel assemblies in each of the three radial zones (zone I, zone II and zone III). The determined method is as follows: if the 32 selected spent fuel assemblies have the same initial enrichment, the spent fuel assemblies are divided into three groups based on burnup and cooling time. Specifically, the division can be as follows: if the burnup of all spent fuel assemblies does not exceed a predetermined burnup, then they are divided into three groups based on cooling time; or, if the cooling time of all spent fuel assemblies does not exceed a predetermined cooling time, then they are divided into three groups based on burnup; or, if only some of the burnup or cooling time of all spent fuel assemblies does not exceed a predetermined burnup or cooling time, then they are divided into three groups based on burnup or cooling time from smallest to largest. There are 3 groups, and the number of spent fuel assemblies in each group is the same as the number of storage cells in each storage area of ​​the radial partition, that is, 4, 12 and 16 respectively. If the 32 spent fuel assemblies arranged in the same storage container have different initial enrichment, the spent fuel assemblies are divided into 3 groups according to initial enrichment, burnup and cooling time. Specifically, they can be divided into 3 groups according to the initial enrichment or burnup or cooling time from small to large. The number of spent fuel assemblies in each group is the same as the number of storage cells in each area of ​​the radial partition, that is, 4, 12 and 16 respectively.

[0058] Then, the maximum decay heat of the screened spent fuel assemblies is obtained. If the maximum decay heat of all spent fuel assemblies is less than a first predetermined value (e.g., 1.1 kW), then... Figure 1 Scheme (a) – the uniform loading scheme – involves pre-arranging the corresponding number of spent fuel assemblies directly in the first, second, and third storage areas. If the maximum decay heat of all spent fuel assemblies is greater than a first predetermined value (e.g., 1.1 kW) but less than a second predetermined value (e.g., 1.3 kW), then [the scheme is adopted]. Figure 1Scheme (b) – the zoned loading scheme – is pre-arranged as follows: Spent fuel assemblies with a first burnup and a first cooling time are arranged in storage compartment I; spent fuel assemblies with a second burnup and a second cooling time are arranged in storage compartment II; and spent fuel assemblies with a third burnup and a third cooling time are arranged in storage compartment III. Here, the first burnup is the minimum burnup, the second burnup is the maximum burnup, the third burnup is the intermediate burnup, the first cooling time is the maximum cooling time, the second cooling time is the minimum cooling time, and the third cooling time is the intermediate cooling time.

[0059] The arrangement scheme described above is the lumped parameter method. See the diagram for the specific layout determined by the lumped parameter method. Figure 3 (a) It should be noted that the burnup, decay heat, and source strength of spent fuel assemblies determined by the lumped parameter method do not have a spatial (gradient) distribution, and do not reflect the differences in burnup, decay heat, and source terms of each fuel rod in the spent fuel assembly with respect to its location.

[0060] Furthermore, the power of the spent fuel assembly during reactor operation is represented by burnup. In this embodiment, the burnup of the spent fuel assembly is the average burnup of 264 fuel rods. Based on the power history of the spent fuel assembly during reactor operation, the lumped parameter method is typically used to calculate the burnup of the spent fuel assembly during source term calculations. The actual power (burnup) history of the spent fuel assembly during reactor operation is a three-dimensional spatial distribution. The three-dimensional power of the spent fuel assembly during reactor operation is reconstructed using a reactor physics calculation program, and the resulting axial power distribution is shown in [the figure]. Figure 4 The shape of the axial power distribution curve typically changes during reactor operation. Figure 4 The three curves represent the power curves of spent fuel assemblies irradiated three times in the reactor (that is, spent fuel assemblies are typically used three times in the reactor, with different start times and durations for each use). Among them, EQ_L has a longer irradiation time, while EQ_S1 has a shorter irradiation time. Figure 4 The single red straight (or broken) line in the diagram corresponds to the envelope limit line of the power distribution, which is... Figure 4 It is known that the power (burnup) of spent fuel assemblies exhibits a higher characteristic in the lower half and a lower characteristic in the upper half along the axial direction. Based on the distance function relationship between the radiation source intensity of the spent fuel assembly, the surface dose of the storage container, and the source intensity, the burnup and decay heat of the spent fuel assembly in the radial three zones (Zone I, Zone II, and Zone III) using the lumped parameter method do not achieve the optimal radiation protection principle of ALARA and have the following problems:

[0061] First, the varying distances between the 16 storage cells in Zone III and the outer surface of the dry storage container were not considered, nor were their contributions to the dose rate on the outer surface of the dry storage container taken into account, thus failing to follow the ALARA (Optimization of Radiation Protection) principle. Second, the radiation source intensities (i.e., neutron and gamma source intensities in Table 1) of the spent fuel assemblies arranged in the 16 storage cells in Zone III are zero-dimensional, failing to consider the radial distribution of the radiation source terms of the spent fuel assemblies, resulting in varying contributions to the dose rate on the outer surface of the dry storage container, again failing to follow the ALARA principle. To address the aforementioned problems with the lumped parameter method, S20 implemented an optimized arrangement based on the lumped parameter method to achieve optimal radiation protection for the dry storage container—an engineering practice.

[0062] S20. Based on all the pre-arranged spent fuel assemblies, obtain the surface dose rate contribution of the dry storage container, and confirm the weighting factor of the spent fuel assembly located at the preset storage position in each of the storage areas.

[0063] In this step, after the pre-arrangement of spent fuel assemblies in multiple storage areas of the dry storage container is completed, the surface dose rate contribution of the storage container is obtained. The surface dose rate directly reflects the radiation safety risk of the dry storage container to the surrounding environment and personnel. By calculating the contribution of all spent fuel assemblies to the surface dose rate of the container after pre-arrangement, the radiation safety under the current arrangement scheme can be clearly understood. The arrangement scheme can be adjusted according to the radiation safety to reduce the radiation risk.

[0064] The spent fuel assemblies located in pre-defined storage positions within each storage area have varying degrees of impact on the overall performance of the storage container due to their specific locations (e.g., proximity to the storage container surface, placement within a critical heat dissipation path, etc.). Identifying the weighting factors for these assemblies essentially assigns different levels of importance to the spent fuel assemblies in different locations. A higher weighting factor indicates a greater impact of the spent fuel assembly on key indicators such as the surface dose rate and overall burnup distribution of the storage container. By determining the weighting factors, subsequent adjustments to these pre-defined storage positions can be prioritized during the initial deployment, based on predetermined rules, to ensure the deployment scheme better meets safety and efficiency requirements.

[0065] In one embodiment, S20 includes:

[0066] Calculate the dispersion of the average burnup share of all spent fuel assemblies after pre-arrangement, calculate the distance between the location of each storage area and the surface of the dry storage container, and calculate the area ratio of the area of ​​each storage cell in the third storage area to the surface area of ​​the dry storage container.

[0067] Based on the dispersion, distance, and area ratio, the weighting factors for spent fuel assemblies located at the corners of the second and third storage areas are determined.

[0068] In this embodiment, the average burnup share represents the average burnup (or power share) of all spent fuel assemblies within a certain radial zone, reflecting the overall burnup level or power distribution characteristics of the storage area. Dispersion describes the degree of dispersion of the average burnup share of spent fuel assemblies in each storage area; the smaller the dispersion, the more concentrated the average burnup share; the larger the dispersion, the more dispersed the average burnup share distribution. The dispersion of the average burnup share of all pre-arranged spent fuel assemblies (represented by "θ1") can be calculated using the dispersion function in an Excel spreadsheet. The burnup of each spent fuel assembly can be obtained from Table 1. The distance between the location of each storage area in the dry storage container and the surface of the dry storage container is fixed and can be directly measured. Similarly, the area of ​​each storage cell in the third storage area is fixed to the surface area of ​​the dry storage container. Therefore, the area ratio of each storage cell in the third storage area to the surface area of ​​the dry storage container is also fixed and can be obtained directly or calculated by measuring the two areas.

[0069] Among them, the corner positions are Figure 1 Example (a) illustrates this, where each grid cell is a storage cell, specifically 2B / 2E and 5B / 5E in the second storage area, and 1B / 1E, 2A / 2F, 5A / 5F, and 6B / 6E in the third storage area, totaling 12 storage cells. Based on the dispersion, distance, and area ratio obtained above, the weighting factors for these 12 storage cells are shown in Table 3.

[0070] Table 3 Weighting factors for corner positions in dry storage containers

[0071]

[0072] The predetermined dispersion can be 0.26. The weighting factor of the spent fuel assemblies located at the corners of the second and third storage areas can be determined according to Table 3.

[0073] S30. According to the weighting factor, arrange all the pre-arranged spent fuel assemblies for the first time according to the predetermined rules.

[0074] In this step, after determining the weight factors of spent fuel assemblies located at preset storage locations in each storage area, the first arrangement of all pre-arranged spent fuel assemblies is carried out according to a predetermined rule. By carrying out the first arrangement of all pre-arranged spent fuel assemblies according to this rule, the positions of the corresponding spent fuel assemblies can be adjusted in a targeted manner, and the spent fuel assemblies that have a greater impact on the performance of the storage container can be improved first, so that the pre-arrangement scheme can be initially optimized.

[0075] Specifically, S30 includes:

[0076] Obtain the characteristic parameters of all spent fuel assemblies in each storage area;

[0077] If the spent fuel assemblies in the same storage area have the same initial enrichment, then the spent fuel assembly with the first burnup and the first cooling time is selected and arranged in the storage compartment located at the corner of the third storage area;

[0078] If the spent fuel assemblies in different storage areas have the same initial enrichment, then the spent fuel assembly with the second burnup and the second cooling time is selected and arranged in the storage compartment located at the corner of the second storage area.

[0079] This embodiment is a specific rule of the predetermined rules. First, the initial enrichment of all spent fuel assemblies in the same storage area is compared. When the spent fuel assemblies in the same storage area have the same initial enrichment, the spent fuel assembly with the smaller source term (with the first burnup and the first cooling time) is selected and arranged in the storage cell (1B / 1E / 2A / 2F / 5A / 5F / 6B / 6E) located at the corner of the third storage area. When the spent fuel assemblies in different storage areas have the same initial enrichment, the spent fuel assembly with the larger source term (with the second burnup and the second cooling time) is selected and arranged in the storage cell (2B / 2E / 5B / 5E) located at the corner of the second storage area, thus completing the first arrangement.

[0080] S40. Obtain the radial burnup distribution of each spent fuel assembly in one of the storage areas after pre-arrangement and obtain the radial burnup distribution of each spent fuel assembly located at a preset arrangement position in each of the storage areas after the first arrangement. Based on each radial burnup distribution, perform a second arrangement of the corresponding spent fuel assembly.

[0081] In this step, the radial burnout distribution reflects the radial differences in nuclear fuel consumption of spent fuel assemblies during storage. The radial burnout distribution of a single storage area can reveal the radial burnout balance of spent fuel assemblies within that storage area, avoiding safety risks caused by excessive burnout in local areas. Then, based on the radial burnout distribution, the corresponding spent fuel assemblies are arranged a second time, and the positions of the corresponding spent fuel assemblies can be adjusted in a targeted manner.

[0082] In one embodiment, S40 includes:

[0083] Obtain the radial burnup distribution of each spent fuel assembly in the pre-arranged third storage area and each spent fuel assembly located at the corner position in the second and third storage areas after the first arrangement;

[0084] The side of the spent fuel assembly with the lowest radial burnup is positioned towards the inner wall of the dry storage container.

[0085] In this embodiment, since the third storage area is located on the outermost layer of the dry storage container and is closest to the dry storage container, it is preferable to obtain one of the pre-arranged storage areas as the third storage area. That is, it is necessary to obtain the radial burnout distribution of all spent fuel assemblies (16 spent fuel assemblies) in the pre-arranged third storage area. After the first arrangement in S30, the spent fuel assemblies located at the corners of the third storage area change, and their corresponding radial burnout distribution also changes. Therefore, it is necessary to re-obtain the radial burnout distribution of the spent fuel assemblies located at the corners of the third storage area. Moreover, the storage chambers at the corners of the second storage area are also close to the surface of the dry storage container. Therefore, it is also necessary to obtain the four spent fuel assemblies located at the corners of the second storage area.

[0086] During the arrangement, following the ALARA principle of radiation protection, the 20 spent fuel assemblies with the smaller radial power are arranged towards the inner wall of the dry storage container. This ensures that the side of the spent fuel assembly with the smaller radiation source term is closer to the dry storage container, while the side of the spent fuel assembly with the larger radiation source term is farther away from the dry storage container, thereby reducing the surface dose rate of the dry storage container by approximately 30%.

[0087] In one embodiment, S40 further includes:

[0088] The burnup spatial distribution of each spent fuel assembly is calculated and reconstructed using reactor physics procedures to obtain the radial burnup distribution of each spent fuel assembly.

[0089] Based on the radial burnout distribution, the burnout deviation of the first and last columns in each spent fuel assembly is confirmed;

[0090] If the fuel consumption deviation is less than the predetermined deviation, the corresponding spent fuel assembly is arranged in the storage compartment located at the corner of the second storage area and in the storage compartment located in the middle of the third storage area.

[0091] If the fuel consumption deviation is greater than or equal to the predetermined deviation, the corresponding spent fuel assembly will be arranged in the storage compartment located at the corner of the third storage area.

[0092] In this embodiment, the burnup spatial distribution of each spent fuel assembly is calculated and reconstructed using reactor physics procedures to obtain the radial burnup distribution of each spent fuel assembly. Each spent fuel assembly includes 264 fuel rods; therefore, the radial burnup distribution of each spent fuel assembly is the radial power distribution of the 264 fuel rods (see [link to relevant documentation]). Figure 5 ),Depend on Figure 5It can be seen that the fuel rods exhibit a characteristic of higher fuel consumption (power) in the first row (i.e., higher in arrays 1-2) and lower fuel consumption in the last row (i.e., lower in arrays 16-17) in the radial direction, and the average fuel consumption deviation between the first and last rows is about 30%, with a maximum fuel consumption deviation of about 50%.

[0093] according to Figure 5 Determine the burnup deviation of the first row (arrays 1-2) and the last row (arrays 16-17) of these 20 spent fuel assemblies. If the burnup deviation is less than the predetermined deviation (1.1), the corresponding spent fuel assembly is arranged in the storage cell (2B / 2E / 5B / 5E) located at the corner of Zone II and the storage cell (1C / 1D / 3F / 4F / 6C / 6D) located in the middle of Zone III; if the burnup deviation is greater than or equal to the predetermined deviation (1.1), the corresponding spent fuel assembly is arranged in the storage cell (1B / 1E / 2A / 2F / 5A / 5F / 6B / 6E) located at the corner of Zone III, thus completing the second arrangement.

[0094] In practical engineering applications, radial partitioning of the dry storage container is unnecessary. A simplified partitioning approach is sufficient: divide the core and storage container's storage compartments into quadrants (see...). Figure 6 Locate the quadrant position of the spent fuel assembly in the reactor core, and place it in the same quadrant position when arranging the dry storage container.

[0095] like Figure 7 As shown, the arrangement method described in this embodiment of the invention further includes:

[0096] S51. Obtain the decay heat of all spent fuel assemblies after the first and second arrangements;

[0097] S52. If all decay heats are less than the predetermined decay heat, calculate the total decay of all spent fuel assemblies in the dry storage container.

[0098] S53. Determine whether the total decay variable is less than the predetermined decay variable. If the total decay variable is less than the predetermined decay variable, the deployment is confirmed to be successful.

[0099] In this embodiment, after the secondary arrangement optimization of the spent fuel assemblies in the dry storage container, it is confirmed whether the decay heat of each spent fuel assembly is less than a predetermined decay heat (e.g., 1.1 kW). If all decay heats are less than the predetermined decay heat, the total decay variable of the spent fuel assemblies arranged in all storage compartments (32) in the entire dry storage container is calculated to see if it is less than a predetermined decay variable (e.g., 35.2 kW). If the total decay variable is less than the predetermined decay variable, the final spent fuel arrangement scheme is obtained. See details below. Figure 3(b) The optimized spent fuel arrangement scheme achieves the best radiation protection during the processes of dry storage container surface decontamination and sealing operations, and minimizes the collective dose to workers, making a significant contribution to worker health and environmental protection.

[0100] Compared with the original lumped parameter method, the arrangement method of this invention is mainly based on the optimization and improvement of the power (burnup) spatial distribution of spent fuel assemblies. It solves the problem of how to optimize radiation protection and minimize the collective dose to workers when arranging spent fuel assemblies in dry storage containers. This arrangement method can also be applied to determining the loading arrangement scheme of spent fuel assemblies in transport containers, playing an important role in optimizing radiation protection and minimizing the collective dose to workers during spent fuel loading and transportation.

[0101] This invention also provides an apparatus for arranging spent fuel assemblies, which is used to perform any of the aforementioned embodiments of the spent fuel assembly arrangement method. Specifically, please refer to... Figure 8 , Figure 8 This is a schematic block diagram of a spent fuel assembly arrangement apparatus provided in an embodiment of the present invention. The spent fuel assembly arrangement apparatus 600 includes:

[0102] The pre-arrangement unit 610 is used to radially partition the dry storage container to obtain multiple storage areas, and to pre-arrange each spent fuel assembly on the multiple storage areas respectively;

[0103] The weighting factor confirmation unit 620 is used to obtain the surface dose rate contribution of the dry storage container based on all pre-arranged spent fuel assemblies, and to confirm the weighting factor of the spent fuel assembly located at the preset storage position in each of the storage areas.

[0104] The first arrangement unit 630 is used to arrange all the pre-arranged spent fuel assemblies for the first time according to the weighting factor and a predetermined rule.

[0105] The second arrangement unit 640 is used to obtain the radial burnout distribution of each spent fuel assembly in one of the storage areas after pre-arrangement and to obtain the radial burnout distribution of each spent fuel assembly located at a preset arrangement position in each of the storage areas after the first arrangement, and to perform a second arrangement of the corresponding spent fuel assemblies according to each radial burnout distribution.

[0106] This invention provides a dry storage container, including the arrangement of spent fuel assemblies as described above.

[0107] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the dry storage containers, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0108] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for arranging spent fuel assemblies, applied to a dry storage container, characterized in that, include: The dry storage container is radially partitioned to obtain multiple storage areas, and each spent fuel assembly is pre-arranged in each of the multiple storage areas; Based on all pre-arranged spent fuel assemblies, obtain the surface dose rate contribution of the dry storage container and confirm the weighting factor of the spent fuel assemblies located at the preset storage positions in each of the storage areas. Based on the weighting factor, all pre-arranged spent fuel assemblies are arranged for the first time according to predetermined rules. The radial burnup distribution of each spent fuel assembly in one of the storage areas after pre-arrangement is obtained, and the radial burnup distribution of each spent fuel assembly located at a preset arrangement position in each of the storage areas after the first arrangement is obtained. Based on each radial burnup distribution, the corresponding spent fuel assembly is arranged a second time.

2. The arrangement method according to claim 1, characterized in that, The step of radially partitioning the dry storage container to obtain multiple storage areas, and pre-arranging each spent fuel assembly in multiple storage areas, includes: Obtain the number of storage chambers in the dry storage container; Based on the number of storage chambers and the critical safety and thermal safety conditions during the storage process of the dry storage container, all storage chambers are divided into at least three storage areas arranged from the inside out: a first storage area, a second storage area, and a third storage area. The number of storage chambers in the first storage area is less than the number of storage chambers in the second storage area, and the number of storage chambers in the second storage area is less than the number of storage chambers in the third storage area. The characteristic parameters of all spent fuel assemblies to be stored are obtained, and the assemblies are screened according to the characteristic parameters. The screened spent fuel assemblies are then pre-arranged in multiple storage areas.

3. The arrangement method according to claim 2, characterized in that, The characteristic parameters include initial enrichment, fuel consumption, and cooling time; The process of acquiring characteristic parameters of all spent fuel assemblies to be stored, filtering them based on these parameters, and pre-arranging the filtered spent fuel assemblies in multiple storage areas includes: If all spent fuel assemblies to be stored have the same initial enrichment, then the spent fuel assemblies that meet the safety conditions and parameter limits are selected. Obtain the maximum decay heat of all screened spent fuel assemblies. If the maximum decay heat is less than a first predetermined value, then directly arrange them in the first storage area, the second storage area, and the third storage area. If the maximum decay heat is greater than a first predetermined value and less than a second predetermined value, then the spent fuel assembly with the first burnup and first cooling time is arranged in the first storage area, the spent fuel assembly with the second burnup and second cooling time is arranged in the second storage area, and the spent fuel assembly with the third burnup and third cooling time is arranged in the third storage area, wherein the number of storage cells in the first storage area is less than the number of storage cells in the second storage area, and the number of storage cells in the second storage area is less than the number of storage cells in the third storage area.

4. The arrangement method according to claim 3, characterized in that, The step of obtaining the surface dose rate contribution of the dry storage container based on all pre-arranged spent fuel assemblies, and determining the weighting factor of spent fuel assemblies located at preset storage positions in each storage area, includes: Calculate the dispersion of the average burnup share of all spent fuel assemblies after pre-arrangement, calculate the distance between the location of each storage area and the surface of the dry storage container, and calculate the area ratio of the area of ​​each storage cell in the third storage area to the surface area of ​​the dry storage container. Based on the dispersion, distance, and area ratio, the weighting factors for spent fuel assemblies located at the corners of the second and third storage areas are determined.

5. The arrangement method according to claim 3, characterized in that, The predetermined rules include: Obtain the characteristic parameters of all spent fuel assemblies in each storage area; If the spent fuel assemblies in the same storage area have the same initial enrichment, then the spent fuel assembly with the first burnup and the first cooling time is selected and arranged in the storage compartment located at the corner of the third storage area; If the spent fuel assemblies in different storage areas have the same initial enrichment, then the spent fuel assembly with the second burnup and the second cooling time is selected and arranged in the storage compartment located at the corner of the second storage area.

6. The arrangement method according to claim 4, characterized in that, The process of obtaining the radial burnup distribution of each spent fuel assembly in one of the storage areas after pre-arrangement and obtaining the radial burnup distribution of each spent fuel assembly located at a preset arrangement position in each of the storage areas after the first arrangement, and performing a second arrangement of the corresponding spent fuel assemblies based on each radial burnup distribution, includes: Obtain the radial burnup distribution of each spent fuel assembly in the pre-arranged third storage area and obtain the radial burnup distribution of each spent fuel assembly located at the corner position in the second and third storage areas after the first arrangement; The side of the spent fuel assembly with the lowest radial burnup is positioned towards the inner wall of the dry storage container.

7. The arrangement method according to claim 6, characterized in that, The process of obtaining the radial burnup distribution of each spent fuel assembly in one of the storage areas after pre-arrangement and obtaining the radial burnup distribution of each spent fuel assembly located at a preset arrangement position in each of the storage areas after the first arrangement, and performing a second arrangement of the corresponding spent fuel assemblies based on each radial burnup distribution, further includes: The burnup spatial distribution of each spent fuel assembly is calculated and reconstructed using reactor physics procedures to obtain the radial burnup distribution of each spent fuel assembly. Based on the radial burnout distribution, the burnout deviation of the first and last columns in each spent fuel assembly is confirmed; If the fuel consumption deviation is less than the predetermined deviation, the corresponding spent fuel assembly is arranged in the storage compartment located at the corner of the second storage area and in the storage compartment located in the middle of the third storage area. If the fuel consumption deviation is greater than or equal to the predetermined deviation, the corresponding spent fuel assembly will be arranged in the storage compartment located at the corner of the third storage area.

8. The arrangement method according to claim 1, characterized in that, Also includes: Obtain the decay heat of all spent fuel assemblies after the first and second arrangements; If all decay heats are less than the predetermined decay heat, then calculate the total decay of all spent fuel assemblies in the dry storage container; Determine whether the total decay variable is less than the predetermined decay variable. If the total decay variable is less than the predetermined decay variable, the deployment is confirmed to be successful.

9. A device for arranging spent fuel assemblies, applied to a dry storage container, characterized in that, include: A pre-arrangement unit is used to radially partition the dry storage container to obtain multiple storage areas, and to pre-arrange each spent fuel assembly in each of the multiple storage areas; The weighting factor confirmation unit is used to obtain the surface dose rate contribution of the dry storage container based on all pre-arranged spent fuel assemblies, and to confirm the weighting factor of the spent fuel assembly located at the preset storage position in each of the storage areas. The first arrangement unit is used to arrange all the pre-arranged spent fuel assemblies for the first time according to the weighting factor and a predetermined rule. The second arrangement unit is used to obtain the radial burnout distribution of each spent fuel assembly in one of the storage areas after pre-arrangement and to obtain the radial burnout distribution of each spent fuel assembly located at a preset arrangement position in each of the storage areas after the first arrangement, and to perform a second arrangement of the corresponding spent fuel assembly according to each radial burnout distribution.

10. A dry storage container, characterized in that, Includes the arrangement of spent fuel assemblies as described in claim 9.

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