Monte carlo and cfd based multi-physics coupled calculation method for fuel irradiation test

Abstract

The application provides a Monte Carlo and CFD-based fuel irradiation test multi-physical coupling calculation method, relates to the irradiation coupling calculation technical field, and aims to realize fast processing and convenient subsequent interface development and data processing of a multi-physical field program, and comprises the following steps: irradiation device modeling based on in-pile components and fuel irradiation test objects; grid mapping of a cell, so as to obtain the intersection of different partition spaces of a CSG geometry structure of the fuel irradiation test object and a CFD geometry model; coupling model establishment, so as to obtain an external interface module; and key parameter iteration. The application has the advantages of efficient processing, applicability, and convenience in subsequent interface development and data processing of a multi-physical field program.

Description

Technical Field

[0001] This invention relates to the field of irradiation coupling calculation technology, and more specifically, to a multiphysics coupling calculation method for fuel irradiation tests based on Monte Carlo and CFD. Background Technology

[0002] With the development of computer technology and computational fluid dynamics (CFD) methods, the thermal calculation and analysis of reactor fuel irradiation tests are increasingly adopting refined three-dimensional CFD-based methods for detailed calculation and analysis. Three-dimensional computational fluid dynamics (CFD) programs directly solve the fundamental equations of fluid dynamics, enabling precise three-dimensional calculations of the reactor interior. Therefore, they have received widespread attention and application in reactor fuel irradiation tests.

[0003] Currently, physical-thermal-engineering coupling methods include establishing six sets of delayed neutron dynamics models (PKM) or multi-group neutron diffusion equations based on the UDF interface built into CFD programs or user programs, and establishing external coupling interfaces with mature Monte Carlo programs such as MCNP5 through UDF interfaces or user programs to achieve physical-thermal-engineering coupling. However, existing methods have limited processing efficiency and are difficult to develop and process for interfaces of multiphysics programs.

[0004] Therefore, it is necessary to optimize the multiphysics coupling calculation for fuel irradiation testing to achieve rapid processing and facilitate the interface development and data processing of subsequent multiphysics programs. Summary of the Invention

[0005] The purpose of this invention is to provide a multiphysics coupled calculation method for fuel irradiation tests based on Monte Carlo and CFD, which can achieve rapid processing and facilitate the interface development and data processing of subsequent multiphysics programs.

[0006] This invention is achieved through the following technical solution:

[0007] Testing of multiphysics coupled computational methods for fuel irradiation based on Monte Carlo and CFD methods includes the following steps:

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

[0009] By performing grid mesh mapping, the intersection of different partition spaces of the CSG geometry of the fuel irradiation test object and the CFD geometric model is obtained;

[0010] A coupling model is established to obtain the external interface module;

[0011] Perform key parameter iterations.

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

[0013] Monte Carlo modeling is performed on the in-core component and the fuel irradiation test object;

[0014] The in-core component is divided into a radiation environment area and a coupling calculation area;

[0015] The fuel irradiation test object geometry is axially divided in the coupling calculation area, and a new cell number is assigned, and a point mark is established based on the CSG geometry, material composition and counter type of the fuel irradiation test object;

[0016] The geometry and grid 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] A mapping relationship is established between the numbers of different partition spaces of the CSG geometry of the fuel irradiation test object and spatial attributes, including center coordinates, partition volume, material composition, material density and counter;

[0019] The intersection of different partition spaces in the grid model of the fuel irradiation test object and the geometry is established, realizing the mapping of different partition spaces of the fuel irradiation test object and the granularity of the geometry.

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

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

[0022] An external interface module is established based on Python;

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

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

[0025] Preferably, the method for iterating key parameters is:

[0026] An example calculation is performed through the external interface module, an input file is traversed, the geometry, material information and statistical information in the fuel irradiation device are sorted and mapped, and two pairs of tuple sets are formed with number information and material information as indexes;

[0027] Traverse two output files, extract the neutron and photon energy of different partition space, get the corresponding specific heat, and add it to the external interface module fuel irradiation device element tuple set, the set indexed by material information stores different tuples of different partition space geometry information and specific heat information, the corresponding density gets the volume heat release rate of the corresponding material, the axial / radial distribution information of the three-dimensional coordinates of different materials and the corresponding volume heat release rate form a CSV data file 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 a heat source input;

[0029] Based on the intersection, the comprehensive value of the physical characteristics is obtained;

[0030] The structure information, coordinate information and material information of different partition spaces are stored in the tuple set indexed by the number information, and the density and temperature cross section of the material are updated by the temperature scalar field of each partition space;

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

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

[0033] The physical characteristics of the partition space of each intersection are obtained respectively;

[0034] The average value of the physical characteristics of all the partition spaces is obtained.

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

[0036] The present application simulates the irradiation process by Monte Carlo method, improves the accuracy of irradiation analysis, and combines CFD to effectively consider various influences of the actual irradiation process, and provides more comprehensive physical understanding;

[0037] The present application can realize flexible modeling and data statistics of complex geometric shapes based on the intersection processing of grid mapping and CSG geometric structure, and realize more efficient and convenient data processing subsequently;

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

[0039] The calculation design and interface design of the present application are suitable for various types of fuel irradiation tests, improve the universality and application range of the method, and are convenient for popularization and implementation. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1A flowchart of a Monte Carlo and CFD-based fuel irradiation test multi-physics coupling calculation method for embodiment 1 of the present application is provided.

[0041] Figure 2 A principle diagram of an implementation case provided for embodiment 1 of the present application. DETAILED DESCRIPTION

[0042] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in connection with the drawings of the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0043] Embodiment 1

[0044] The present embodiment provides a Monte Carlo and CFD-based fuel irradiation test multi-physics coupling calculation method, referring to Figure 1 , comprising the following steps:

[0045] Modeling the irradiation device based on the in-core components and the fuel irradiation test object;

[0046] Mapping the cell grid to obtain the intersection of different partition spaces of the CSG geometry structure of the fuel irradiation test object and the CFD geometry model;

[0047] Establishing the coupling model to obtain the external interface module;

[0048] Iterating the key parameters.

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

[0050] Monte Carlo modeling the in-core components and the fuel irradiation test object;

[0051] Dividing the in-core components into a radiation environment area and a coupling calculation area, the in-core components generally include fuel elements of different burnup depths, burnable poisons, beryllium blocks, aluminum blocks, stainless steel blocks, control rods, etc.;

[0052] Axially dividing the geometry structure of the fuel irradiation test object in the coupling calculation area and assigning a new cell number, establishing a point identifier based on the CSG geometry structure, material composition and counter type of the fuel irradiation test object, the fuel irradiation test object is generally established as a CAD model here;

[0053] Establishing the geometry structure and grid model of the fuel irradiation test object based on the CFD method.

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

[0055] The mapping relationship is established between the number of different partition spaces of the CSG geometry of the fuel irradiation test object and the spatial attributes, including the center coordinates, partition volume, material composition, material density, and counter;

[0056] The intersection of different partition spaces under the grid model of the fuel irradiation test object and the geometry is established, realizing the mapping of different partition spaces of the fuel irradiation test object and the granularity of the geometry.

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

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

[0059] An external interface module is established based on Python;

[0060] The external interface module is used to read and analyze 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 performing key parameter iteration is preferably:

[0063] An example calculation is performed through the external interface module, an input file is traversed, and the geometry, material information, and statistical information in the fuel irradiation device are sorted and mapped uniformly to form two pairs of tuple sets indexed by number information and material information, respectively;

[0064] Two output files are traversed, the neutron and photon energy of different partition spaces is extracted, the corresponding specific heat is obtained, and the fuel irradiation device tuple set in the external interface module is added, the different tuples in the set indexed by material information store the geometry information and specific heat information of different partition spaces, the volume heat release rate of the corresponding material is obtained through the corresponding density, the three-dimensional coordinates of different materials and the axial / radial distribution information of the volume heat release rate are formed into a CSV data file in the Z-axis direction, and the update and saving are performed;

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

[0066] Based on the intersection, the comprehensive value of the physical characteristics is obtained;

[0067] The structure information, coordinate information and material information of different partitions in the tuple set indexed by the number information are stored in different tuples, and the density and temperature section of the material are updated by the temperature scalar field of each partition space;

[0068] The above steps are repeated until the volume heat release rate changes less than a preset value.

[0069] When executed, the method for obtaining a comprehensive value of a physical feature based on the intersection is preferably:

[0070] The physical feature of each partition space of each intersection is obtained respectively;

[0071] An average value of the physical features of all the partition spaces is obtained.

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

[0073] In the intersection, due to the large number of grids, the direct intersection calculation of all grids is too time-consuming, so this embodiment selects a certain number of representative grids from each partition space. When sampling, the density of the grid can be based on to capture the main characteristics of the partition space, but the sample size should not be too large to avoid unnecessary computational burden. When obtaining the physical characteristics later, considering that the CFD surface grid design usually has a small growth rate, and the modeling process does not use different encryption processing in the same partition space, the resolution of the grid remains relatively stable throughout the simulation domain. When processing 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 used, where the weight of each partition space is set to 1. This weighted average method is based on the equal weight principle, that is, the scalar field in different partition spaces contributes equally to its global characteristics, so by directly adding the scalar values of each partition space and dividing by the number of samples in the partition space, a weighted average value reflecting the overall physical characteristics can be obtained. It is particularly pointed out that after accumulating certain data experience in actual operation, the following geometric characteristics and parameters that have less impact on the result can be identified according to experience, and further simplified and approximated to reduce the amount of calculation.

[0074] The final iteration process is simply implemented as follows. In the parameter transmission stage, the external interface module first integrates the volume heat release rate information of different cells based on the CSG partition information, generates accurate three-dimensional volume heat release rate distribution information under the same material information, and then updates the three-dimensional volume heat release rate distribution in different regions of the CFD geometric model according to the material information. Finally, it is converted into an input format that can be recognized by the CFD geometric model and updated into the CFD geometric model. In the parameter feedback stage, the scalar field information (temperature of different materials) of the CFD geometric model is used to traverse the cells in the CSG model of the irradiation device that have the material information, update the material density of the cells, and update the temperature of the corresponding material through the cell material number. Then it is converted into an input format that can be recognized by the Monte Carlo simulation to complete one iteration. Table 1 is a comparison table of calculated values before and after coupling with measured values for an actual operation case. Specifically, the temperature values at the measurement points before and after coupling are compared and analyzed based on the Monte Carlo and CFD methods for multi-physical coupling calculation of a fuel irradiation test device in the HFETR reactor. The deviation between the measured value before coupling and the measured value is 6.1%, and the deviation between the measured value after coupling and the measured value is reduced to 4.6%.

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

[0076]

[0077] The above merely describes the preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for multi-physics coupling calculation of fuel irradiation test based on Monte Carlo and CFD, characterized in that, The method comprises the following steps: performing irradiation device modeling based on in-pile components and fuel irradiation test objects; performing grid mapping of cells to obtain intersections of different partition spaces of CSG geometry of the fuel irradiation test objects and a CFD geometric model; performing coupling model establishment to obtain an external interface module; performing key parameter iteration; the method for performing coupling model establishment is: establishing the external interface module based on Python; the external interface module is used for reading and analyzing data; the format of the external interface module adopts a data exchange format; the method for performing key parameter iteration is: performing calculation of an example through the external interface module, traversing an input file, and arranging and mapping geometry, material information and statistical information in the fuel irradiation device to form two sets of tuples indexed by number information and material information respectively; traversing two output files, extracting neutron and photon energy of different partition spaces, obtaining corresponding specific heat, and adding the specific heat into the fuel irradiation device tuple set in the external interface module, so that different tuples in the set indexed by material information store geometry information and specific heat information of different partition spaces, and the volume heat release rate of the corresponding material is obtained through the corresponding density, and the axial / radial distribution information of the three-dimensional coordinates of different materials and the volume heat release rate is formed into a CSV data file to be updated and saved; the axial and radial distribution information of the volume heat release rate of each material is transmitted to a CFD program as a heat source input; obtaining a comprehensive value of a physical feature based on the intersections; different tuples in the tuple set indexed by the number information store structure 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; the above steps are repeated until the volume heat release rate changes by less than a preset value; the method for obtaining a comprehensive value of a physical feature based on the intersections is: obtaining the physical feature of each intersection; obtaining the average value of the physical features of all the partition spaces.

2. The Monte Carlo and CFD based fuel irradiation proving multiphysics coupled calculation method of claim 1, wherein, the method for performing irradiation device modeling is: performing Monte Carlo modeling on the in-pile components and the fuel irradiation test objects; dividing the in-pile components into a radiation environment area and a coupling calculation area; performing axial division on the geometry of the fuel irradiation test objects in the coupling calculation area, assigning new cell numbers, and establishing point identifiers based on the CSG geometry, material composition and counter type of the fuel irradiation test objects; establishing the geometry and grid model of the fuel irradiation test objects based on the CFD method.

3. The Monte Carlo and CFD based fuel irradiation proving multiphysics coupled calculation method of claim 2, wherein, the method for performing grid mapping of cells is: establishing a mapping relationship between the numbers and spatial attributes of different partition spaces of the CSG geometry of the fuel irradiation test objects, the spatial attributes including center coordinates, partition volumes, material compositions, material densities and counters; establishing intersections of different partition spaces under the grid model of the fuel irradiation test objects and the geometry, and realizing mapping of different partition spaces of the fuel irradiation test objects and the geometry granularity.

4. The Monte Carlo and CFD based fuel irradiation proving multiphysics coupled calculation method of claim 3, wherein, When establishing the intersection of different partition spaces of the CSG geometry of the fuel irradiation test object and the CFD geometry model, a certain number of representative grids are sampled from each of the partition spaces for establishment.

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