Neutron transport node coarse net generation method based on fine net combination

Abstract

The invention discloses a neutron transport node coarse net generation method based on fine net combination, which comprises the following steps of: 1, firstly traversing all radial fine grid boundary lines, and reading the length of the boundary lines, the areas of grids on two sides, material information and the like; 2, assuming that grids on two sides of the boundary line are merged, respectively calculating vector included angles between end points at two ends of the boundary line and adjacent boundary points on the grids, judging whether concave boundaries appear at the end points, and deleting the grids with the concave boundaries from the boundary line list; 3, calculating the combination weight of each boundary line based on the length of the boundary line, the area of the grids on the two sides and the material information; 4, screening the boundary line with the maximum merging weight in the boundary line list; 5, merging the grids on the two sides, deleting boundary line information, and updating a boundary line list; and 6, if residual elements exist in the boundary line list, returning to the step 2. According to the method, the convex boundary attribute of the coarse mesh is obtained, the method is suitable for any radial mesh, material information on the two sides of the mesh is considered, the method can be used for coarse mesh generation of a coarse mesh acceleration method of a neutron transport node method, and the quality of the coarse mesh is improved.

Description

Technical Field

[0001] The present invention relates to the technical fields of nuclear reactor core design and safety, and particularly relates to a method for generating a coarse mesh of neutron transport nodal based on fine mesh merging. Background Art

[0002] All along, the nodal method has the advantages of high solution efficiency and less computing resource occupation compared with methods such as the Monte Carlo method and the finite element method in the neutron transport solution method, and occupies an important position in core physics calculations.

[0003] With the continuous development of the nuclear power industry, the geometric structures of advanced reactors are becoming increasingly complex. To achieve accurate modeling using the nodal method, the number of computational grids required is increasing, and the shapes are becoming increasingly irregular.

[0004] The coarse mesh acceleration method is a type of neutron transport acceleration method with mature methods and wide applications. However, it requires a set of coarse meshes with a larger grid size than the transport calculation grids in space to cooperate with it to achieve the best acceleration effect. Traditional coarse meshes with regular geometric shapes are suitable for regular structured geometries and are not applicable to complex non-structured geometries. Summary of the Invention

[0005] In order to overcome the problems existing in the above-mentioned prior art, the present invention provides a method for generating a coarse mesh of neutron transport nodal based on fine mesh merging. This method avoids the traditional form of dividing the coarse mesh from top to bottom according to a regular structured geometry, but adopts the idea from bottom to top. Starting from any transport calculation grid at the bottom layer, through an iterative process, grids are continuously merged to increase the grid size, and finally a coarse mesh is obtained. Compared with the traditional method, it can be applied to grids under any complex geometry, can adapt to the irregular grid shapes generated by the spatial domain decomposition for parallel computing, and improves the generality of coarse mesh generation.

[0006] In order to achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0007] A method for generating a coarse mesh of neutron transport nodal based on fine mesh merging, characterized by comprising the following steps:

[0008] Step 1: Read information such as the lengths of all radial boundary lines, the areas of the grids on both sides, and the filling materials of the existing fine grids to obtain a boundary line list;

[0009] Step 2: Assume the merging of the grids on both sides of the boundary line, calculate the vector angles between the two end points of all boundary lines and the adjacent boundary points on the large merged grid, and determine whether a concave boundary is generated at the end points. For the boundary lines with concave boundaries generated, delete them from the boundary line list; if the boundary line list is empty at this time, end;

[0010] Step 3: Based on the boundary line lengths, the grid areas on both sides, and the filling material information obtained in Step 1, calculate the merging weights of the remaining boundary lines in the boundary line list, as shown in formula (3.1);

[0011] wt 合并 =LS1S2wt 材料 (3.1)

[0012] where,

[0013] wt 合并 —— Merging weight of the boundary line;

[0014] L —— Length of the boundary line;

[0015] S1, S2 —— Grid areas on both sides of the boundary line;

[0016] wt 材料 —— Material consistency coefficient on both sides of the boundary line;

[0017] Step 4: Select the boundary line with the largest merging weight in the boundary line list;

[0018] Step 5: Perform a merging operation on the grids on both sides of the selected boundary line, delete the boundary line, and update the boundary line list;

[0019] Step 6: Determine whether there are still remaining elements in the boundary line list at this time. If so, repeat Steps 2 to 5.

[0020] Compared with the prior art, the present invention avoids using the traditional form of dividing the coarse grid from top to bottom according to the regular structure geometry, but adopts the idea from bottom to top. The underlying arbitrary transport calculation grids are continuously merged through an iterative process to increase the grid size, and finally a coarse grid is obtained. Compared with the traditional method, it ensures the convex boundary property of the obtained coarse grid, can be applied to grids under any complex geometry, and takes into account the material information on both sides of the grid, can adapt to the irregular grid shapes generated by the spatial domain decomposition for parallel computing, and improves the generality of coarse grid generation and the quality of the coarse grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a flowchart of the method of the present invention.

[0022] Figure 2 is a schematic diagram of the coarse grid generated by applying the method of the present invention to the structural geometric triangular grid under domain decomposition parallelism.

[0023] Figure 3 is a partial schematic diagram of the coarse grid generated by applying the method of the present invention to the unstructured geometric triangular grid under domain decomposition parallelism. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0025] Step 1: Traverse all the radial fine grid boundary lines, read the lengths of all the radial boundary lines of the existing fine grid, the grid areas on both sides, and the information of the filling materials, etc., to obtain a boundary line list.

[0026] Step 2: Assume that the grids on both sides of the boundary line are merged, calculate the vector angles between the two end points of all the boundary lines and the adjacent two boundary points on the merged large grid. If the vector angle of a certain end point to the adjacent two boundary points on the merged large grid is greater than 180 degrees, it is determined that a concave boundary is generated at this end point. For the boundary line with a concave boundary generated, delete it from the boundary line list; if the boundary line list is empty at this time, the method ends.

[0027] Step 3: Based on the boundary line lengths, the grid areas on both sides, and the information of the filling materials, etc., obtained in Step 1, calculate the merging weights of the remaining boundary lines in the boundary line list, as shown in formula (3.1).

[0028] wt 合并 =LS1S2wt 材料 (3.1)

[0029] Wherein,

[0030] wt 合并 ——The merging weight of the boundary line;

[0031] L——The length of the boundary line;

[0032] S1, S2——The grid areas on both sides of the boundary line;

[0033] wt 材料 ——The material consistency coefficient on both sides of the boundary line;

[0034] For Figure 2 the hexagonal component geometry shown, the material consistency coefficients of the adjacent triangular grids belonging to different components are relatively low, so that the merging weight of their boundary lines is lower than that of the internal boundary lines of the component, resulting in the final grid being mainly hexagonal grids; for Figure 3 the unstructured grid geometry shown, since the circular arc shown on the left in the figure is the material of the drum absorber, and the material consistency coefficient of the grid adjacent to other materials is also relatively low, the merging weight of the boundary line between the absorber and the external structural material is lower than that of the internal boundary lines of the absorber material, and the final coarse grid shape is a quadrilateral formed by combining two adjacent triangles in the absorber area.

[0035] Step 4: Select the one with the largest merging weight in the boundary line list.

[0036] Step 5: Perform a merging operation on the grids on both sides of the selected boundary line, delete the boundary line, and update the boundary line list.

[0037] Step 6: Determine whether there are any remaining elements in the boundary line list at this time. If there are, repeat Steps 2 to 5.

Claims

1. A method for generating a coarse mesh of neutron transport nodalization based on fine mesh merging, characterized in that: The method includes the following steps: Step 1: Read the lengths of all radial boundary lines, the grid areas on both sides, and the information of the filling material in the fine grid to obtain a boundary line list; Step 2: Assume that the grids on both sides of the boundary line are merged, calculate the vector angles between the two end points of all boundary lines and the adjacent boundary points on the large merged grid, and determine whether a concave boundary is generated at the end point. For the boundary line with a concave boundary generated, delete it from the boundary line list; if the boundary line list is empty at this time, the method ends; Step 3: Based on the boundary line lengths, the grid areas on both sides, and the filling material information obtained in Step 1, calculate the merging weights of the remaining boundary lines in the boundary line list, as shown in formula (3.1); wt 合并 = LS1S2wt 材料 (3.1) where wt 合并 —— Boundary line merging weight; L — the length of the boundary line; S1, S2 — the grid areas on both sides of the boundary line; wt 材料 —— Coefficient of material consistency on both sides of the boundary line; Step 4: Select the boundary line with the largest merging weight in the boundary line list; Step 5: Perform a merging operation on the grids on both sides of the selected boundary line, delete the boundary line, and update the boundary line list; Step 6: Determine whether there are still remaining elements in the boundary line list at this time. If so, repeat Steps 2 to 5.

2. The method for generating a coarse mesh of neutron transport nodal cells based on thin mesh merging according to claim 1, wherein: In Step 2, if the vector angle between a certain end point and the adjacent boundary points on the large merged grid is greater than 180 degrees, it is determined that a concave boundary is generated at that end point.

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