Multi-physical coupling calculation method for fuel irradiation test based on Monte Carlo and CFD (Computational Fluid Dynamics)

Abstract

The invention provides a fuel irradiation test multi-physics coupling calculation method based on Monte Carlo and CFD, relates to the technical field of irradiation coupling calculation, and aims to realize rapid processing and facilitate interface development and data processing of a subsequent multi-physics field program, and comprises the following steps: carrying out irradiation device modeling based on reactor internals and a fuel irradiation test object; lattice cell grid mapping is carried out, and intersections of different partition spaces of the CSG geometric structure of the fuel irradiation test object and the CFD geometric model are obtained; establishing a coupling model to obtain an external interface module; and carrying out key parameter iteration. The method has the advantages of high processing efficiency, high applicability and convenience in interface development and data processing of subsequent multi-physical field programs.

Description

Technical Field

[0001] The invention relates to the technical field of radiation coupling calculation, and in particular to a multi-physics coupling calculation method for fuel radiation test based on Monte Carlo and CFD. Background Art

[0002] With the development of computer technology and computational fluid dynamics methods, the thermal calculation and analysis of the fuel irradiation test in the research reactor has gradually adopted the three-dimensional scale refined thermal hydraulic method based on CFD for fine calculation and analysis. The three-dimensional computational fluid dynamics program (CFD) directly solves the basic equations of fluid mechanics and can perform fine three-dimensional calculations inside the reactor. Therefore, it has received widespread attention and application in the reactor fuel irradiation test.

[0003] Among the current physical-thermal coupling methods, there are six groups of delayed neutron kinetic models (PKM) or multi-group neutron diffusion equations established based on the built-in UDF interface of the CFD program or the user program, and there are also external coupling interfaces with mature Monte Carlo programs such as MCNP5 established through the UDF interface or user program to achieve physical-thermal coupling. However, the existing methods have limited processing efficiency and are difficult to develop and process interfaces for multi-physics programs.

[0004] Therefore, it is necessary to optimize the multi-physics coupling calculation of fuel irradiation test to achieve fast processing and facilitate the interface development and data processing of subsequent multi-physics field programs. Summary of the invention

[0005] The object of the present invention is to provide a multi-physics coupling calculation method for fuel irradiation test based on Monte Carlo and CFD, which can realize rapid processing and facilitate the interface development and data processing of subsequent multi-physics field programs.

[0006] The present invention is achieved through the following technical solutions:

[0007] The multi-physics coupling calculation method for fuel irradiation test based on Monte Carlo and CFD includes the following steps:

[0008] Modeling of irradiation device based on reactor internals and fuel irradiation test objects;

[0009] Perform grid mapping to obtain the intersection of different partition spaces of the CSG geometric structure of the fuel irradiation test object and the CFD geometric model;

[0010] Establish a coupling model and obtain an external interface module;

[0011] Iterate on key parameters.

[0012] Preferably, the method for modeling the irradiation device is:

[0013] Performing Monte Carlo modeling on the reactor internals and the fuel irradiation test object;

[0014] The reactor internal components are divided into an area providing irradiation environment and a coupling calculation area;

[0015] Axially dividing the geometric structure of the fuel irradiation test object in the coupled calculation region, assigning new grid element numbers, and establishing punctuation marks based on the CSG geometric structure, material composition and counter type of the fuel irradiation test object;

[0016] The geometric structure and mesh model of the fuel irradiation test object are established based on the CFD method.

[0017] Preferably, the method for performing cell grid mapping is:

[0018] Establishing a mapping relationship between the numbers of different partition spaces of the CSG geometric structure of the fuel irradiation test object and the spatial attributes, wherein the spatial attributes include center coordinates, partition volume, material composition, material density and counter;

[0019] The intersections of different partition spaces under the grid model of the fuel irradiation test object and the geometric structure are established to achieve mapping between different partition spaces of the fuel irradiation test object and the geometric structure granularity.

[0020] Preferably, when establishing the intersection of different partitioned spaces of the CSG geometric structure of the fuel irradiation test object and the CFD geometric model, a certain number of representative grids are sampled from each of the partitioned spaces for establishment.

[0021] Preferably, the method for establishing the coupling model is:

[0022] Establish external interface module based on Python;

[0023] The external interface module is used to read and parse data.

[0024] Preferably, the format of the external interface module adopts a data exchange format.

[0025] Preferably, the method for performing key parameter iteration is:

[0026] Performing example calculations through the external interface module, traversing an input file, sorting and mapping the geometric structure, material information and statistical information in the fuel irradiation device, and forming two pairs of tuple sets indexed by number information and material information respectively;

[0027] Traverse the two output files, extract the neutron and photon energies of different partition spaces, obtain the corresponding specific heat release, and add them into the fuel irradiation device tuple set in the external interface module, store the geometric information and specific heat release information of different partition spaces in different tuples in the set indexed by material information, obtain the volume heat release rate of the corresponding material through the corresponding density, and form a CSV data file with the three-dimensional coordinates of different materials and the corresponding axial / radial distribution information of the volume heat release rate in the Z-axis direction, update and save;

[0028] The axial and radial distribution information of the volume heat release rate of each material is transmitted to the CFD program as heat source input;

[0029] obtaining a comprehensive value of the physical feature based on the intersection;

[0030] Different tuples in the tuple set indexed by the number information store the structural information, coordinate information and material information of different partition spaces, and the density and temperature cross section of the material are updated through the temperature scalar field of each partition space;

[0031] Repeat the above steps until the volume heat release rate change is less than the preset value.

[0032] Preferably, the method for obtaining the comprehensive value of the physical feature based on the intersection is:

[0033] Obtaining physical characteristics of the partitioned space of each intersection respectively;

[0034] Get the average value of the physical characteristics of all the partitioned spaces.

[0035] The technical solution of the present invention has at least the following advantages and beneficial effects:

[0036] The present invention simulates the irradiation process by using the Monte Carlo method, thereby improving the accuracy of irradiation analysis. At the same time, combined with CFD, it can effectively consider various influences of the actual irradiation process and provide a more comprehensive physical understanding.

[0037] Based on the intersection processing of grid cell mapping and CSG geometric structure, the present invention can realize flexible modeling and data statistics of complex geometric shapes, and realize subsequent more efficient and convenient data processing;

[0038] The present invention can optimize the calculation efficiency and improve the reliability of the calculation results by iterating key parameters;

[0039] The calculation design and interface design of the present invention are applicable to various types of fuel irradiation tests, thus improving the versatility and application scope of the method and facilitating its promotion and implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1A flow chart of a multi-physics coupling calculation method for fuel irradiation test based on Monte Carlo and CFD provided in Example 1 of the present invention;

[0041] Figure 2 A schematic diagram of the principles of an implementation case provided for Example 1 of the present invention. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0043] Example 1

[0044] This embodiment provides a multi-physics coupling calculation method for fuel irradiation test based on Monte Carlo and CFD, see Figure 1 , including the following steps:

[0045] Modeling of irradiation device based on reactor internals and fuel irradiation test objects;

[0046] Perform grid mapping to obtain the intersection of different partition spaces of the CSG geometric structure of the fuel irradiation test object and the CFD geometric model;

[0047] Establish a coupling model and obtain an external interface module;

[0048] Iterate on key parameters.

[0049] In this embodiment, the method for modeling the irradiation device is:

[0050] Performing Monte Carlo modeling on the reactor internals and the fuel irradiation test object;

[0051] The reactor internals are divided into the area providing irradiation environment and the coupling calculation area. The reactor internals generally include fuel elements with different burnup depths, combustible poisons, beryllium blocks, aluminum blocks, stainless steel blocks, control rods, etc.

[0052] Axially dividing the geometric structure of the fuel irradiation test object in the coupling calculation region, assigning new grid element numbers, and establishing punctuation marks based on the CSG geometric structure, material composition and counter type of the fuel irradiation test object, where the fuel irradiation test object is usually established as a CAD model;

[0053] The geometric structure and mesh model of the fuel irradiation test object are established based on the CFD method.

[0054] Furthermore, the method for performing cell grid mapping is:

[0055] Establishing a mapping relationship between the numbers of different partition spaces of the CSG geometric structure of the fuel irradiation test object and the spatial attributes, wherein the spatial attributes include center coordinates, partition volume, material composition, material density and counter;

[0056] The intersections of different partition spaces under the grid model of the fuel irradiation test object and the geometric structure are established to achieve mapping between different partition spaces of the fuel irradiation test object and the geometric structure granularity.

[0057] As a preferred solution, when establishing the intersection of different partitioned spaces of the CSG geometric structure of the fuel irradiation test object and the CFD geometric model, a certain number of representative grids are sampled from each of the partitioned spaces for establishment.

[0058] On the other hand, the method for establishing the coupling model is:

[0059] Establish external interface module based on Python;

[0060] The external interface module is used to read and parse data.

[0061] Specifically, the format of the external interface module adopts the data exchange format (CSV), thereby ensuring compatibility with different simulation tools.

[0062] Finally, the method for iterating key parameters is preferably:

[0063] Performing example calculations through the external interface module, traversing an input file, sorting and mapping the geometric structure, material information and statistical information in the fuel irradiation device, and forming two pairs of tuple sets indexed by number information and material information respectively;

[0064] Traverse the two output files, extract the neutron and photon energies of different partition spaces, obtain the corresponding specific heat release, and add them into the fuel irradiation device tuple set in the external interface module, store the geometric information and specific heat release information of different partition spaces in different tuples in the set indexed by material information, obtain the volume heat release rate of the corresponding material through the corresponding density, and form a CSV data file with the three-dimensional coordinates of different materials and the corresponding axial / radial distribution information of the volume heat release rate in the Z-axis direction, update and save;

[0065] The axial and radial distribution information of the volume heat release rate of each material is transmitted to the CFD program as heat source input;

[0066] obtaining a comprehensive value of the physical feature based on the intersection;

[0067] Different tuples in the tuple set indexed by the number information store the structural information, coordinate information and material information of different partition spaces, and the density and temperature cross section of the material are updated through the temperature scalar field of each partition space;

[0068] Repeat the above steps until the volume heat release rate change is less than the preset value.

[0069] During execution, the method for obtaining the comprehensive value of the physical feature based on the intersection is preferably:

[0070] Obtaining physical characteristics of the partitioned space of each intersection respectively;

[0071] Get the average value of the physical characteristics of all the partitioned spaces.

[0072] Based on the technical solution of this embodiment, refer to Figure 2 After basic irradiation device modeling, an external interface module used as an external coupling interface program is established based on Python. By identifying the punctuation marks of the fuel irradiation device in the Monte Carlo model, the information of the irradiation device grid cell description card, surface description card, material card and counting card is obtained. The interface program can automatically obtain the surface coordinate information of the surface description card according to the different surface numbers in the grid cell description card in the input card, and obtain the center coordinates of the grid cell and the volume of the grid cell according to the surface coordinates of the grid cell. The mass of the grid cell is obtained through the density information in the grid cell description card, and a tuple is established to store the grid cell number, coordinates, material and other information. Through the information of the counting cards such as F6 and F7, the energy of neutrons, fission fragments, gamma rays and beta rays generated by the fuel fission process in the output file and deposited in the fuel, structural materials and water is automatically extracted and processed, and the specific heat release rate information is stored in the tuple. According to the mass, specific heat release rate and volume information of each grid cell in the tuple, the volume heat release rate of the grid cell is obtained. For the same CAD model of the fuel irradiation test object, a CFD geometric model of the fuel irradiation test object is established. After preprocessing steps, including geometry cleaning (such as removing small features and simplifying complex areas), mesh generation (converting the geometric model into a computational mesh) and boundary condition setting, a prismatic layer mesh generator is used for the coolant boundary layer inside the fuel irradiation test object, and a polyhedron mesh generator is used for the rest to generate meshes of different structural sizes.

[0073] When establishing the intersection, due to the large number of grids, the time cost of directly calculating the intersection of all grids is too high, so this embodiment chooses to sample a certain number of representative grids from each partition space. When sampling, the density of the grid can be used to capture the main features of the partition space, but the sample size should not be too large to avoid unnecessary computational burden. When obtaining physical features later, given that the CFD surface grid design usually has a small growth rate, and the modeling process does not use different encryption treatments in the same partition space, the resolution of the grid remains relatively stable in the entire simulation domain. When processing the scalar field information of different partition spaces (CFD scalar field information is carried and transmitted through the grid), a simplified weighted average strategy can be adopted, in which the weight of each partition space is set to 1. This weighted average method is based on the principle of equal weight, that is, the contribution of the scalar field in different partition spaces to its global characteristics is equivalent, so by directly accumulating the scalar values ​​of each partition space and dividing it by the number of samples in the partition space, a weighted average reflecting the overall physical characteristics can be obtained. It is particularly noted that after accumulating a certain amount of data experience in actual operation, the following geometric features and parameters that have less impact on the results can be identified based on experience, and these features can be further simplified and approximated to reduce the amount of calculation.

[0074] The final iteration process is simply implemented by the external interface module in the parameter transmission stage. Through the different partition information of CSG, the volume heat release rate information of different grid elements is first integrated to generate accurate three-dimensional volume heat release rate distribution information under the same material information. Then, in combination with different regions in the CFD geometric model, the three-dimensional volume heat release rate distribution in different regions is updated according to the material information. Finally, it is converted into an input format that can be recognized by the CFD geometric model and updated to the CFD geometric model. In the parameter feedback stage, through the scalar field information of the CFD geometric model (the temperature of different materials), the grid elements with the material information in the CSG model of the irradiation device are traversed, and the material density of the grid element is updated. Through the material number of the grid element, the temperature of the corresponding material is updated, and then converted into an input format that can be recognized by the Monte Carlo simulation to complete an iteration. Table 1 is a comparison table of calculated values ​​and measured values ​​before and after coupling of a practical case. Specifically, a multi-physics coupling calculation based on Monte Carlo and CFD methods was performed on a fuel irradiation test device in the HFETR reactor. The temperature values ​​of the measurement points before and after coupling were compared and analyzed. The deviation between the measured value and the measured value before coupling was 6.1%, and the deviation after coupling was reduced to 4.6%.

[0075] Table 1 Comparison of calculated and measured values ​​before and after coupling

[0076]

[0077] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-physics coupling calculation method for fuel irradiation test based on Monte Carlo and CFD, characterized by: The following steps are involved: Modeling of irradiation device based on reactor internals and fuel irradiation test objects; Perform grid mapping to obtain the intersection of different partition spaces of the CSG geometric structure of the fuel irradiation test object and the CFD geometric model; Establish a coupling model and obtain an external interface module; Iterate on key parameters.

2. The multi-physics coupling calculation method for fuel irradiation test based on Monte Carlo and CFD according to claim 1 is characterized in that: The method for modeling the irradiation device is: Performing Monte Carlo modeling on the reactor internals and the fuel irradiation test object; The reactor internal components are divided into an area providing irradiation environment and a coupling calculation area; Axially dividing the geometric structure of the fuel irradiation test object in the coupled calculation region, assigning new grid element numbers, and establishing punctuation marks based on the CSG geometric structure, material composition and counter type of the fuel irradiation test object; The geometric structure and mesh model of the fuel irradiation test object are established based on the CFD method.

3. The multi-physics coupling calculation method for fuel irradiation test based on Monte Carlo and CFD according to claim 2 is characterized in that: The method for performing cell grid mapping is: Establishing a mapping relationship between the numbers of different partition spaces of the CSG geometric structure of the fuel irradiation test object and the spatial attributes, wherein the spatial attributes include center coordinates, partition volume, material composition, material density and counter; The intersections of different partition spaces under the grid model of the fuel irradiation test object and the geometric structure are established to achieve mapping between different partition spaces of the fuel irradiation test object and the geometric structure granularity.

4. The multi-physics coupling calculation method for fuel irradiation test based on Monte Carlo and CFD according to claim 3 is characterized in that: When establishing the intersection of different partitioned spaces of the CSG geometric structure of the fuel irradiation test object and the CFD geometric model, a certain number of representative grids are sampled from each of the partitioned spaces for establishment.

5. The multi-physics coupling calculation method for fuel irradiation test based on Monte Carlo and CFD according to claim 1 is characterized in that: The method for establishing the coupling model is: Establish external interface module based on Python; The external interface module is used to read and parse data.

6. The multi-physics coupling calculation method for fuel irradiation test based on Monte Carlo and CFD according to claim 5 is characterized in that: The format of the external interface module adopts a data exchange format.

7. The multi-physics coupling calculation method for fuel irradiation test based on Monte Carlo and CFD according to claim 1 is characterized in that: The method for iterating key parameters is: Performing example calculations through the external interface module, traversing an input file, sorting and mapping the geometric structure, material information and statistical information in the fuel irradiation device, and forming two pairs of tuple sets indexed by number information and material information respectively; Traverse the two output files, extract the neutron and photon energies of different partition spaces, obtain the corresponding specific heat release, and add them into the fuel irradiation device tuple set in the external interface module, store the geometric information and specific heat release information of different partition spaces in different tuples in the set indexed by material information, obtain the volume heat release rate of the corresponding material through the corresponding density, and form a CSV data file with the three-dimensional coordinates of different materials and the corresponding axial / radial distribution information of the volume heat release rate in the Z-axis direction, update and save; The axial and radial distribution information of the volume heat release rate of each material is transmitted to the CFD program as heat source input; obtaining a comprehensive value of the physical feature based on the intersection; Different tuples in the tuple set indexed by the number information store the structural information, coordinate information and material information of different partition spaces, and the density and temperature cross section of the material are updated through the temperature scalar field of each partition space; Repeat the above steps until the volume heat release rate change is less than the preset value.

8. The multi-physics coupling calculation method for fuel irradiation test based on Monte Carlo and CFD according to claim 7 is characterized in that: The method for obtaining the comprehensive value of the physical feature based on the intersection is: Obtaining physical characteristics of the partitioned space of each intersection respectively; Get the average value of the physical characteristics of all the partitioned spaces.

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