Automatic modeling method for finite element analysis of nuclear fuel assembly

Abstract

The invention provides an automatic modeling method for finite element analysis of a nuclear fuel assembly, which belongs to the technical field of digital model processing, and comprises the following steps: after acquiring an initial geometric model, carrying out preprocessing and shelling operations, and identifying contact features and welding spot features; and according to the contact features and the welding spot features, automatically creating the contact features and the welding spot features of the finite element model of the nuclear fuel assembly. Based on the scheme, the initial geometric model is preprocessed, a complex structure, a curved surface structure and an overlapped surface in the model can be simplified, a missing surface can be filled, and then surface stitching is completed. And the problem of inaccurate connection relation caused by incorrect contact surface selection and wrong contact direction can be avoided. And then, finite element modeling is performed on the nuclear fuel assembly by using the pre-extracted contact features and welding spot features, so that software can automatically complete the modeling process, and the model can be ensured to have enough precision by combining with the correction of the preprocessing process on the model.

Description

Technical Field

[0001] The present invention generally relates to the technical field of digital model processing, and in particular to an automatic modeling method for finite element analysis of nuclear fuel components. Background Art

[0002] Nuclear fuel assemblies, core components of nuclear reactors, consist of the fuel skeleton, grid assembly, fuel rods, upper and lower tube sockets, and other components. Their complex structure and harsh operating environment place them at the heart of safety. Therefore, accurate finite element modeling and mechanical property analysis of nuclear fuel assemblies are crucial for ensuring their design rationality and operational reliability. In finite element modeling of nuclear fuel assemblies, the contact relationship and weld joint connections of the grid assembly are crucial for ensuring model accuracy.

[0003] During the modeling process, the fuel rods are clamped using rigid and elastic protrusions, resulting in a large number of contact relationships in the model, with the number of contacts reaching tens of thousands. Current common simulation methods rely on manual operations, including manually creating contact elements, assigning contact properties, and creating weld connection elements.

[0004] However, when modeling and analyzing grid components, significant issues exist with the way contacts and welds are applied. While some software supports automatic contact generation, this often results in inaccurate contact relationships due to issues like incorrect contact surface selection and incorrect contact direction. Manually applying contacts is cumbersome, time-consuming, and prone to errors. Manual addition of welds is often necessary, but with thousands of welds, this is not only a massive workload but also prone to omission or duplication, impacting model accuracy. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide an automatic modeling method for finite element analysis of nuclear fuel assemblies.

[0006] The present invention provides a method for automatic modeling of a nuclear fuel assembly by finite element analysis, comprising: S1: Obtain the initial geometric model of the nuclear fuel assembly; S2: Preprocessing the initial geometric model to obtain a first geometric model; S3: performing a shell extraction operation on the first geometric model to obtain a shell element model; S4: Identifying contact features and solder joint features of the shell element model; the shell element model includes a plurality of grid cells, each grid cell includes a rigid protrusion and an elastic protrusion; the contact features include a rigid protrusion feature and an elastic protrusion feature; S5: According to the contact features and the weld features, the contact features and the weld features are automatically created for the finite element model of the nuclear fuel assembly.

[0007] According to the technical solution provided by the present invention, S2: preprocessing the initial geometric model to obtain a first geometric model, including: The initial geometric model is sequentially subjected to model simplification, missing surface repair, surface cutting, overlapping surface processing, and gap stitching to obtain the first geometric model; The surface cutting comprises: dividing the surface into a plurality of geometric shapes; The overlapping surface processing includes: merging the overlapping surfaces into a single surface; The gap stitching includes: extending two adjacent surfaces whose gap is within a set gap range until the two surfaces intersect.

[0008] According to the technical solution provided by the present invention, the model simplification includes: Replacing the rounded corner structure and chamfered corner structure of the initial geometric model with a right-angle structure; Filling the defect holes of the initial geometric model.

[0009] According to the technical solution provided by the present invention, filling the defect holes of the initial geometric model includes: detecting all holes with an area smaller than a set area in the initial geometric model to obtain a plurality of defective holes; Selecting a plurality of first sampling points at the edge of the defect hole; Use straight lines to connect adjacent first sampling points to obtain multiple reference straight lines; Polygons formed by a plurality of adjacent and coplanar reference straight lines are filled into planes.

[0010] According to the technical solution provided by the present invention, along a direction perpendicular to the reference straight line, the maximum distance between the reference straight line and the edge of the defective hole is within the set gap range.

[0011] According to the technical solution provided by the present invention, the missing surface repair includes: Obtaining the surface to be repaired; The surface to be repaired is extended until the gap between the surface to be repaired and the adjacent surface is within the set gap range.

[0012] According to the technical solution provided by the present invention, the surface is divided into multiple geometric shapes, including: Select multiple second sampling points on the entire surface; Connecting a plurality of adjacent second sampling points to form a plurality of non-overlapping triangles; Merge multiple adjacent and coplanar triangles into the same face to obtain multiple polygonal shapes; The plurality of polygonal shapes and the remaining triangle shapes are collectively regarded as a plurality of geometric shapes.

[0013] According to the technical solution provided by the present invention, the shell element model includes: the mid-surfaces of the grid assembly, the fuel rods, and the rigid protrusions and elastic protrusions on the grid assembly obtained by shell extraction operations; S4: Identifying contact features and weld features of the shell element model, including: Establish a global coordinate system; Obtaining a cell length and a cell height in the shell unit model; the cell length is perpendicular to the extension direction of the fuel rod; and the cell height is parallel to the extension direction of the fuel rod; Calculating the first coordinates of the rigid protrusion and the elastic protrusion in the global coordinate according to the cell length; Calculating a second coordinate of the welding point in the global coordinate according to the cell length and the cell height; Numbering each rigid protrusion and elastic protrusion, and combining the number with the corresponding first coordinate to form a contact feature; Each welding point is numbered, and the number is combined with the corresponding second coordinate to form the welding point feature.

[0014] According to the technical solution provided by the present invention, S5: automatically creating contact features and weld point features for the finite element model of the nuclear fuel assembly based on the contact features and the weld point features, including: Importing the shell element model into finite element software; Assigning material properties to the shell element model; Automatically identifying the coordinates of the contact points and the weld points in the shell element model according to the contact features and the weld point features, and automatically creating the contact points and the weld points; the contact points include rigid protrusions and elastic protrusions; Connect adjacent contact points and solder joints; Set contact properties for contact points; contact properties include: friction coefficient, contact stiffness; Finally, the finite element model of the nuclear fuel assembly is obtained.

[0015] The beneficial effects of the present invention are: After obtaining the initial geometric model of the nuclear fuel assembly, preprocessing and shell extraction are performed, and contact features and weld point features are identified. During the modeling process of the nuclear fuel assembly in the finite element software, contact features and weld point features are automatically created for the finite element model of the nuclear fuel assembly based on these features. Based on this solution, preprocessing the initial geometric model can simplify complex structures (including fillets and chamfers), curved surfaces, and overlapping surfaces in the model, fill in missing surfaces, and complete surface stitching. This can avoid inaccurate connection relationships caused by incorrect contact surface selection and contact direction. Finite element modeling of the nuclear fuel assembly using the pre-extracted contact features and weld point features allows the software to automatically complete the modeling process. Combined with model corrections during the preprocessing process, the constructed model has sufficient accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other features, objects and advantages of the present invention will become more apparent from a reading of the following detailed description of non-limiting embodiments made with reference to the accompanying drawings.

[0017] Figure 1 The figure is a flow chart of an automatic modeling method for finite element analysis of nuclear fuel assemblies; Figure 2 is a schematic diagram of a grid assembly; Figure 3 is a schematic diagram of a gate element; Figure 4 Schematic diagram of uneven defective hole; Among them: 1. Grid assembly; 2. Rigid protrusion; 3. Elastic protrusion; 4. Fuel rod; 5. Grid element; 6. Defect hole; 7. Filling surface. DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the invention are shown in the accompanying drawings.

[0019] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0020] Please refer to Figure 1 The present invention provides a method for automatic modeling of finite element analysis of nuclear fuel assemblies, comprising: S1: Obtain the initial geometric model of the nuclear fuel assembly; Import the nuclear fuel assembly geometry model into geometry processing software (such as SolidWorks, UG, SpaceClaim, DesignModeler, etc.) for preprocessing. The main purpose of preprocessing is to clean and optimize the geometry model to ensure smooth progress in subsequent steps.

[0021] A global coordinate system is established; the coordinate origin is the center point of the grid component, the X-axis and Y-axis directions are the length and width directions of the grid component, and the Z-axis is the height direction.

[0022] S2: Preprocessing the initial geometric model to obtain a first geometric model, including: The initial geometric model is sequentially subjected to model simplification, missing surface repair, surface cutting, overlapping surface processing, and gap stitching to obtain the first geometric model; The imported initial geometry model may contain some unnecessary features, such as small fillets, chamfers, small holes, etc. These features can be simplified to reduce the difficulty and computational complexity of meshing without affecting the analysis results.

[0023] The model simplification includes: Replacing the rounded corner structure and chamfered corner structure of the initial geometric model with a right-angle structure; Filling the defect holes of the initial geometric model, including: detecting all holes with an area smaller than a set area in the initial geometric model to obtain a plurality of defective holes; Specifically, the area is set to be less than or equal to the smallest designed hole area on the grid assembly. For example, the smallest designed hole area on the grid assembly is 1mm 2 , then the setting area can be set to 1mm 2 It should be noted that the designed holes are necessary structures required in the process of designing the structure, rather than unnecessary defective holes.

[0024] Selecting multiple first sampling points at the edge of the defect hole; that is, selecting multiple points on the edge of the defect hole, and obtaining the coordinates of each point in the global coordinate system; Use straight lines to connect adjacent first sampling points to obtain multiple reference straight lines; if the coordinates of two points are known, a straight line passing through the two points can be calculated; Polygons formed by a plurality of adjacent and coplanar reference straight lines are filled into planes.

[0025] Specifically, two adjacent reference straight lines have a common first sampling point.

[0026] If two adjacent first sampling points are traversed by a total of three reference lines, and if these three reference lines are coplanar, then the quadrilateral region enclosed by the four points through which these three reference lines pass can be considered a single plane (ignoring any minor bumps or depressions). If multiple reference lines are coplanar, then the polygon enclosed by the multiple first sampling points through which these reference lines pass can also be roughly considered a single plane.

[0027] If all reference lines are coplanar, it means that the defect hole is relatively flat, so a plane can be used to preliminarily fill the defect hole (only the gaps between the sides of the polygon and the edge of the defect hole remain, and the final filling is completed through the gap stitching step).

[0028] If the polygons formed by the first sampling points are not all coplanar, it indicates that the defect hole is uneven, and the polygons are then filled separately. The gaps between the surfaces formed by the polygons are made to fall within a set gap range; and then, in the gap closure step, the gaps between the polygons are closure-closed.

[0029] The above method can fill the defect hole into a flat surface. Figure 4 Schematic diagram of an uneven defect hole 6, wherein the filling surface 7 is a polygon formed by multiple reference straight lines.

[0030] When the defect hole is uneven, that is, the edges of the defect hole are not coplanar, the above solution can be used to divide the uneven defect hole into multiple polygonal planes, thereby avoiding the situation where the defect hole is incompletely filled when it is uneven.

[0031] In some embodiments, along a direction perpendicular to the reference straight line, the maximum distance between the reference straight line and the edge of the defective hole is within the set gap range (0.01 mm to 0.02 mm, with the upper and lower limits of the interval being closed intervals).

[0032] Based on such a design, the polygonal filling surface 7 and the edge of the defect hole 6 can meet the gap suture conditions, and then can be completed into multiple closed planes through subsequent gap suture steps.

[0033] Wherein, the missing surface repair includes: Obtain the surface to be repaired; generally through manual input or selection; The surface to be repaired is extended until the gap between the surface to be repaired and the adjacent surface is within the set gap range.

[0034] Missing Face Repair is a software feature that checks for missing faces in a geometry model. If missing faces are found, they are repaired using the software's repair tool to ensure the integrity of the geometry model.

[0035] The surface cutting includes dividing the surface into multiple geometric shapes; this not only reduces the difficulty of meshing, but also improves the accuracy of contact area identification.

[0036] Specific steps: uniformly selecting multiple second sampling points on the entire surface; Multiple adjacent second sampling points are connected to form multiple non-overlapping triangles. In this case, the plane area will form multiple coplanar regular triangles, and the area corresponding to the adjacent and coplanar triangles is a plane, otherwise it is a curved surface.

[0037] The entire curved surface is thus roughly divided into a flat part and a curved part; the curved part is then divided into multiple geometric shapes according to triangles; and the flat part is treated as a whole plane.

[0038] Merge multiple adjacent and coplanar triangles into the same face to obtain multiple polygonal shapes; The plurality of polygonal shapes and the remaining triangle shapes are collectively regarded as a plurality of geometric shapes.

[0039] Specifically, surface cutting can cut complex surfaces in geometric models and decompose them into simpler geometric shapes. This not only reduces the difficulty of meshing, but also improves the accuracy of contact point identification.

[0040] The overlapping surface processing includes: merging the overlapping surfaces into a single surface; When there are overlapping faces in the model, it will affect the accuracy of meshing and analysis results. You can eliminate geometric conflicts by deleting the overlapping parts or merging the overlapping faces using the software's "Boolean operation" function.

[0041] The gap stitching includes: extending two adjacent surfaces whose gap is within a set gap range until the two surfaces intersect.

[0042] In this embodiment, the "stitching" operation of the software is used to connect the surfaces on both sides of the gap to form a continuous whole, thereby avoiding discontinuity or errors in mesh division.

[0043] In this embodiment, the gap stitching operation is combined with the previous processing methods to perform preliminary processing on various structures in the model so that the gaps between adjacent surfaces are small enough, and then the gap stitching is used to stitch more adjacent surfaces. Compared with the method of processing each surface independently, the model preprocessing effect is better.

[0044] S3: performing a shell extraction operation on the first geometric model to obtain a shell element model; The shell extraction operation belongs to the existing technology, and the steps include: Set the shell parameters and select the retained faces: Based on the design requirements, select the faces that need to be retained. These faces are usually parts that are connected to the outside or need to maintain a complete structure, such as the installation surface and mating surface of the part; Specify shell thickness: Determine the shell thickness value, which will be applied to the entire model or a specific area. Consider factors such as part strength, stiffness, and manufacturing process to ensure that the shell thickness is reasonable and uniform. Set extraction direction: Determine the direction from which material extraction starts, which will affect the shape and internal structure of the shell. Usually, the direction that is consistent with the main symmetry axis or key feature direction of the model is selected; Generate Shell Features Click the OK or Generate button, the software will automatically perform the shell operation according to the set parameters and generate the corresponding shell features on the model. At this time, the model will be transformed from a solid into a shell with a hollow structure.

[0045] The advantages of the shelling operation include significantly reducing the number of elements and node degrees of freedom, lowering the computational effort, and accurately describing the mechanical behavior of thin-walled structures, ensuring simulation accuracy. The shelling operation provides an efficient and accurate foundation for subsequent meshing and finite element analysis.

[0046] It should be noted that: Reference Figure 2-3 The shell unit model includes: a grid assembly 1, a fuel rod 4, a rigid protrusion 2 in a grid element 5 on the grid assembly 1, and a mid-surface obtained by a shell extraction operation.

[0047] Through the contact features and their coordinates, it is possible to determine whether each component is in the contact area, thereby completing the accurate determination of the contact features.

[0048] S4: Identifying contact features and weld features of the shell element model, including: When performing coordinate positioning and feature recognition on grid components, establishing a unified global coordinate system is a key prerequisite. Grid components generally use a 17×17 format. Based on this, the center of the grid component is established as the origin of the global coordinate system. The three coordinate axes of the global coordinate system are parallel to the length, width, and height of the grid component.

[0049] Assuming the cell length is L, under the global coordinate system, each cell has a unique corresponding coordinate value. For example, the center coordinates of a cell are (-8L, -8L, 0); and the center coordinates of its four adjacent cells are (-8L, -7L, 0), (-8L, -9L, 0), (-7L, -8L, 0), and (-9L, -8L, 0). It can be seen that the distance between the center points of adjacent cells is L. Taking the coordinates (-8L, -7L, 0) as an example, -8L is the coordinate along the length direction, -7L is the coordinate along the width direction, and 0 is the coordinate along the height direction. The global coordinate system constructed in this way can provide a unified benchmark for subsequent coordinate positioning and feature recognition.

[0050] S4-1: Obtaining a cell length and a cell height in the shell unit model; the cell length is perpendicular to the extension direction of the fuel rod; and the cell height is parallel to the extension direction of the fuel rod; Calculating the first coordinates of the rigid protrusion and the elastic protrusion in the global coordinate according to the cell length; S4-2: Calculating a second coordinate of the welding point in the global coordinate according to the cell length and the cell height; S4-3: Number each rigid protrusion and elastic protrusion, and combine the number with the corresponding first coordinate to form a contact feature; Each welding point is numbered, and the number is combined with the corresponding second coordinate to form the welding point feature.

[0051] Specifically, in the grid assembly structure, rigid protrusions and elastic protrusions of the same shape and size but different positions are arranged in each grid cell, and their main function is to firmly clamp the fuel rods.

[0052] Based on this structural characteristic, the rigid protrusions and elastic protrusions in each grid cell that are in contact with the fuel rods can be accurately identified through the precise position coordinates of each component and assigned unique numbers.

[0053] For example, the contact features within the C11 cell are numbered C11_1, C11_2, C11_3, and C11_4 in a counterclockwise direction, starting from the bottom of the cell, and the fuel rod surface within the cell is numbered R11.

[0054] Since the grid cells of the grid assembly are of equal size, a traversal loop program is written to sequentially identify the features of the rigid and elastic protrusions in each cell. Once the traversal is completed, all contact features of the entire grid assembly can be obtained.

[0055] This method lays the foundation for quickly establishing the correspondence between each contact feature and the fuel rod surface in subsequent operations.

[0056] Specifically, the grid strips are inserted and assembled together through mounting slots defined within them to form a grid assembly. These are connected by welds at the intersections, with a 17×17 grid assembly having up to 512 welds. For example, let's identify one of these intersection welds. Assuming the cell height is H, the cell length is L, and the distance between the mounting slots is d, the coordinates of one weld are (L / 2, L / 2, H). The coordinates of the two points in the mounting slot directly opposite the weld are (L / 2, L / 2 + d / 2, H) and (L / 2, L / 2 - d / 2, H).

[0057] In this way, the position of the welding point can be accurately identified. In the subsequent finite element modeling process, a beam connection is established between the welding point and the assembly slot opposite the welding point to accurately establish the welding point.

[0058] Furthermore, S5: automatically creating contact features and weld point features for a finite element model of a nuclear fuel assembly based on the contact features and the weld point features, including: Importing the shell element model into finite element software; Assigning material properties to the shell element model; Automatically identifying the coordinates of the contact points and the weld points in the shell element model according to the contact features and the weld point features, and automatically creating the contact points and the weld points; the contact points include rigid protrusions and elastic protrusions; Connect adjacent contact points and solder joints; Set contact properties for contact points; contact properties include: friction coefficient, contact stiffness; Finally, the finite element model of the nuclear fuel assembly is obtained.

[0059] Specifically, in the finite element analysis workflow, for shell element models that have completed feature processing, it is very necessary to use the secondary development function of the finite element software to realize the automatic identification and creation of key features (such as contact points and welds).

[0060] This process can effectively reduce the complexity and errors of manual operations and improve analysis efficiency and accuracy. The detailed steps include: Choosing development tools: Different finite element software packages come with different secondary development tools and interfaces. For example, Abaqus provides a Python scripting interface, and ANSYS supports secondary development using APDL (ANSYS Parametric Design Language) or Python. You need to choose the appropriate development tool based on the finite element software you are using.

[0061] Import geometric model: Import the processed and feature-recognized geometric model into the finite element software.

[0062] Assign material properties: Assign different material properties to different components. For example, the cladding material of the grid strips and fuel rods is Zr4, and the material property of the elastic protrusions is Inconel718.

[0063] Contact point creation: For the identified contact points, according to the corresponding numbers and coordinates, use the secondary development interface of the finite element software to call the corresponding contact definition function, establish contact pairs for them, and define contact properties for them (such as friction coefficient, contact stiffness, etc.).

[0064] Weld point creation: For the identified weld points, beam connections are established between adjacent weld points to simulate actual weld points.

[0065] Based on the above scheme, a more accurate finite element model of the nuclear fuel assembly can be obtained, and then when analyzing the structural weaknesses of the actual nuclear fuel assembly, more accurate analysis conclusions can be obtained, so as to improve the actual structural design of the nuclear fuel assembly.

[0066] The above description is merely a preferred embodiment of the present invention and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in the present invention.

Claims

1. A method for automatic modeling of nuclear fuel assembly finite element analysis, characterized in that: include: S1: Obtain the initial geometric model of the nuclear fuel assembly; S2: Preprocessing the initial geometric model to obtain a first geometric model; S3: performing a shell extraction operation on the first geometric model to obtain a shell element model; S4: Identifying contact features and solder joint features of the shell element model; the shell element model includes a plurality of grid cells, each grid cell includes a rigid protrusion and an elastic protrusion; the contact features include a rigid protrusion feature and an elastic protrusion feature; S5: According to the contact features and the weld features, the contact features and the weld features are automatically created for the finite element model of the nuclear fuel assembly.

2. The method for automatic finite element analysis modeling of a nuclear fuel assembly according to claim 1, characterized in that: S2: Preprocessing the initial geometric model to obtain a first geometric model, including: The initial geometric model is sequentially subjected to model simplification, missing surface repair, surface cutting, overlapping surface processing, and gap stitching to obtain the first geometric model; The surface cutting comprises: dividing the surface into a plurality of geometric shapes; The overlapping surface processing includes: merging the overlapping surfaces into a single surface; The gap stitching includes: extending two adjacent surfaces whose gap is within a set gap range until the two surfaces intersect.

3. The method for automatic finite element analysis modeling of a nuclear fuel assembly according to claim 2, characterized in that: The model simplification includes: Replacing the rounded corner structure and chamfered corner structure of the initial geometric model with a right-angle structure; Filling the defect holes of the initial geometric model.

4. The method for automatic finite element analysis modeling of a nuclear fuel assembly according to claim 3, characterized in that: Filling the defect holes of the initial geometric model, including: detecting all holes with an area smaller than a set area in the initial geometric model to obtain a plurality of defective holes; Selecting a plurality of first sampling points at the edge of the defect hole; Use straight lines to connect adjacent first sampling points to obtain multiple reference straight lines; Polygons formed by a plurality of adjacent and coplanar reference straight lines are filled into planes.

5. The method for automatic finite element analysis modeling of a nuclear fuel assembly according to claim 4, characterized in that: Along a direction perpendicular to the reference straight line, a maximum distance between the reference straight line and the edge of the defective hole is within the set gap range.

6. The method for automatic finite element analysis modeling of a nuclear fuel assembly according to claim 2, characterized in that: The missing surface repair comprises: Obtaining the surface to be repaired; The surface to be repaired is extended until the gap between the surface to be repaired and the adjacent surface is within the set gap range.

7. The method for automatic finite element analysis modeling of a nuclear fuel assembly according to claim 2, characterized in that: Split a surface into multiple geometric shapes, including: Select multiple second sampling points on the entire surface; Connecting a plurality of adjacent second sampling points to form a plurality of non-overlapping triangles; Merge multiple adjacent and coplanar triangles into the same face to obtain multiple polygonal shapes; The plurality of polygonal shapes and the remaining triangle shapes are collectively regarded as a plurality of geometric shapes.

8. The method for automatic finite element analysis modeling of a nuclear fuel assembly according to claim 1, characterized in that: The shell element model includes: a grid assembly, a fuel rod, and a mid-surface of a rigid protrusion and an elastic protrusion on the grid assembly obtained by shell extraction operation; S4: Identifying contact features and weld features of the shell element model, including: Establish a global coordinate system; Obtaining a cell length and a cell height in the shell unit model; the cell length is perpendicular to the extension direction of the fuel rod; and the cell height is parallel to the extension direction of the fuel rod; Calculating the first coordinates of the rigid protrusion and the elastic protrusion in the global coordinate according to the cell length; Calculating a second coordinate of the welding point in the global coordinate according to the cell length and the cell height; Numbering each rigid protrusion and elastic protrusion, and combining the number with the corresponding first coordinate to form a contact feature; Each welding point is numbered, and the number is combined with the corresponding second coordinate to form the welding point feature.

9. The method for automatic finite element analysis modeling of a nuclear fuel assembly according to claim 1, characterized in that: S5: Automatically creating contact features and weld point features for the finite element model of the nuclear fuel assembly based on the contact features and the weld point features, including: Importing the shell element model into finite element software; Assigning material properties to the shell element model; Automatically identifying the coordinates of the contact points and the weld points in the shell element model according to the contact features and the weld point features, and automatically creating the contact points and the weld points; the contact points include rigid protrusions and elastic protrusions; Connect adjacent contact points and solder joints; Set contact properties for contact points; contact properties include: friction coefficient, contact stiffness; Finally, the finite element model of the nuclear fuel assembly is obtained.

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