A method for assessing the criticality safety of a fuel transport container drop incident
By converting shell elements into solid elements for Monte Carlo particle transport simulation, the problem of low computational efficiency of nuclear force coupling in nuclear fuel transport container drop accidents was solved, and high-precision critical safety assessment was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2026-04-03
- Publication Date
- 2026-07-03
AI Technical Summary
In nuclear fuel transport container drop accidents, the Monte Carlo method cannot directly handle shell element geometry, resulting in low efficiency of nuclear force coupling calculations and making it impossible to achieve high-precision modeling at a reasonable cost.
The shell elements after drop simulation are converted into solid elements, and Monte Carlo particle transport simulation calculations are performed. The geometry of the solid elements is reconstructed through a CAD/CAE platform to achieve geometric compatibility and reduce the simulation burden.
It achieves improved efficiency in nuclear force coupling calculations while maintaining computational accuracy, ensuring critical safety assessment of fuel transport containers after drop accidents.
Smart Images
Figure CN122333757A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of critical safety analysis technology for fuel transport containers, and specifically to a method for assessing the critical safety of fuel transport containers in a drop accident. Background Technology
[0002] During nuclear fuel transportation, fuel transport containers must ensure critical safety even under extreme accidents (such as drops), i.e., to prevent nuclear chain reactions. The Monte Carlo method, due to its high-precision simulation capabilities of complex geometries and physical processes, is one of the preferred methods for critical safety calculations. However, in problems involving "nuclear-force coupling"—that is, when it is necessary to first analyze the deformation of the container structure caused by an accident (such as a drop) through mechanical simulation, and then use the deformed geometry for criticality calculations—a key technical obstacle exists: shell elements are commonly used in mechanical simulations to simulate thin-walled structures to save computational resources, but mainstream Monte Carlo particle transport programs typically cannot directly identify and process this type of shell element geometry, which only has area and no volume. Using solid elements exclusively in mechanical simulations would result in enormous computational scale and low efficiency.
[0003] To address the shortcomings of current nuclear force coupling calculation methods in achieving high-precision modeling and calculation at a reasonable computational cost, a method for assessing the critical safety of fuel transport container drop accidents is invented, which is of great importance. Summary of the Invention
[0004] To address the problems existing in the prior art, the present invention aims to provide a method for evaluating the critical safety of a fuel transport container drop accident. The method converts shell elements in the unstructured mesh model obtained after drop simulation into solid elements, and then performs Monte Carlo particle transport simulation calculations. This effectively solves the geometric compatibility problem in nuclear force coupling calculations, and reduces the simulation burden while ensuring calculation accuracy.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: Step 1: Using a CAD or CAE platform, establish a CAD geometric model of the fuel transport container based on its actual structural dimensions; Step 2: Using a mesh generation tool, the CAD model of the fuel transport container established in Step 1 is discretized to generate an unstructured mesh model, in preparation for subsequent mechanical simulation. Step 3: Import the unstructured mesh model obtained in Step 2 into the mechanical simulation platform, set the accident parameters such as drop height, angle, and ground conditions, and perform drop simulation calculations to obtain the unstructured mesh model of the fuel transport container after simulation. Step 4: From the unstructured mesh model simulated in Step 3, identify and extract the position coordinates, dimensions (such as side length and area), and normal direction information of all shell elements; Step 5: Based on the shell element information extracted in Step 4, each shell element is "reconstructed" into a solid element with a small thickness in the CAD / CAE platform. Subsequently, unstructured meshing is performed on the geometry of these newly established solid elements. Step 6: Using a CAD or CAE platform, merge the unstructured mesh model of all solid elements generated in Step 5 with the mesh of the undeformed parts (such as solid element parts) in the original model to form a complete unstructured mesh model describing the state of the deformed container. Import this model into Monte Carlo particle transport simulation software to perform neutron transport simulation and criticality calculation, and output the effective multiplication factor; Step 7: Based on the methods and limits specified in the national mandatory standard "Regulations for the Safe Transportation of Radioactive Materials", the calculated effective multiplication factor is converted into a critical safety index to quantitatively assess whether the fuel transport container still meets the critical safety requirements after experiencing a drop accident.
[0006] Compared with the prior art, the present invention has the following outstanding advantages: This invention, through the process of "shell element information extraction → solid element geometric reconstruction", converts shell elements that frequently appear in mechanical simulation into solid elements that can be processed by Monte Carlo particle transport simulation software, realizing the reliable transfer of mechanical deformation results to particle transport simulation and avoiding the inefficiency problem caused by using solid elements in mechanical simulation. Attached Figure Description
[0007] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation
[0008] The present invention will be further described in detail below through specific embodiments.
[0009] like Figure 1 As shown, this invention is a method for assessing the critical safety of a fuel transport container in a drop accident, and is implemented using the following technical solution: Step 1: Using a CAE software preprocessor (such as SolidWorks or ANSYS), strictly follow the design drawings of the fuel transport container to create its three-dimensional solid geometric model; Step 2: Use the built-in mesh generation module of the CAE software or a dedicated mesh generation tool to perform unstructured mesh generation on the 3D solid geometry model to generate an unstructured mesh model; Step 3: Import the unstructured mesh model into explicit dynamic analysis software (such as ANSYS / LS-DYNA), set parameters such as drop height, angle, gravity, drop speed, and contact conditions, simulate the entire process of the fuel transport container falling from a specified height onto a rigid plane, calculate the structural deformation and stress distribution, and output the deformed unstructured mesh model file. Step 4: Read the deformed unstructured mesh model file using a script, filter out all data with shell element type, and extract the position coordinates, dimensions (such as side length and area) and normal direction information of all shell elements; Step 5: Based on the information extracted from each shell element, recreate the corresponding 3D solid in the CAD software. Repeat this operation for all shell elements that need to be converted. Next, perform unstructured mesh generation on these newly generated solid groups; Step 6: Using CAE software, integrate all the solid element meshes generated in Step 5 with the solid element meshes in the original model that have not undergone element type changes into a complete unstructured mesh model. Input the material, density, and other information defined in this unstructured mesh model into the Monte Carlo particle transport simulation software. Define physical parameters such as fuel composition and boundary properties in the software, perform neutron transport simulation and criticality calculations, and obtain the effective multiplication factor. Step 7: According to the "Regulations for the Safe Transportation of Radioactive Materials," the calculated effective multiplication factor is compared and converted with the limit specified in the standard to obtain the critical safety index. By determining whether this index meets the safety requirements, the critical safety assessment of the fuel transport container under this drop accident scenario is finally completed.
Claims
1. A method of assessing the criticality safety of a fuel transport container drop incident, characterized by: Includes the following steps: Step 1: Using a CAD or CAE platform, establish a three-dimensional solid geometric model of the fuel transport container based on its structure; Step 2: Use a CAD or CAE platform to perform unstructured mesh generation on the established 3D solid geometric model of the fuel transport container to form an unstructured mesh model; Step 3: Use explicit dynamic analysis software to simulate a drop accident on the unstructured mesh model to obtain the simulated unstructured mesh model; Step 4: Extract the position and size information of shell elements in the simulated unstructured mesh model; Step 5: Using a CAD or CAE platform, based on the extracted position and size information of the shell elements, establish CAD models of the corresponding solid elements of the shell elements and mesh them with unstructured meshes to obtain the unstructured mesh models of the corresponding solid elements of the shell elements. Step 6: Use a CAD or CAE platform to merge the unstructured mesh models of all solid elements obtained in Step 5 to form a complete unstructured mesh model for critical calculation. Use Monte Carlo particle transport simulation software to perform critical calculation and obtain the effective proliferation factor. Step 7: In accordance with the requirements of the "Regulations for the Safe Transportation of Radioactive Materials", the effective multiplication factor obtained in Step 6 is converted into a critical safety index, and the critical safety status of the fuel transport container under a drop accident is assessed based on this index.