A multi-material composite nuclear fuel element design method based on heat transfer topology optimization
Patent Information
- Application Number
- CN202611343721.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-01
- Publication Date
- 2026-11-03
AI Technical Summary
Existing technologies make it difficult to achieve an efficient and uniform distribution of thermally conductive materials in composite nuclear fuels, resulting in insufficient heat transfer performance and affecting fuel service life and safety.
By employing a heat transfer topology optimization method, and through the establishment of a heat conduction model and finite element calculations, combined with a two-way progressive structural optimization method or a variable density method, the material distribution of composite nuclear fuel elements is optimized to achieve global heat transfer performance optimization.
This achieves a better distribution of materials in composite nuclear fuel elements, improves thermal conductivity, reduces the temperature gradient at the fuel center, and enhances safety margin and service performance.
Smart Images
Figure CN123033629A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of nuclear reactor fuel element design technology, specifically relating to a multi-material composite nuclear fuel element design method based on heat transfer topology optimization. Background Technology
[0002] Uranium dioxide (UO2), a typical nuclear fuel, has long been widely used in light water reactors due to its good chemical stability and irradiation properties. However, a significant drawback of UO2 is its low thermal conductivity, which decreases further under high burnup and high temperatures, resulting in a large internal temperature gradient and high core temperature. This not only exacerbates thermal stress and cracking risk in the fuel but may also accelerate the accumulation and release of fission gases, thereby affecting the fuel's service life and safety margin.
[0003] To overcome the insufficient thermal conductivity of UO2, a high thermal conductivity metal (typically with a thermal conductivity greater than 100 W·m) can be used. -1 ·K -1 The introduction of materials into nuclear fuel systems forms metal-ceramic composite fuels. Composite fuels exhibit superior thermal conductivity compared to single UO2, effectively reducing the center temperature of fuel rods, minimizing temperature gradients, and enhancing safety margins under accident conditions. Currently, experimental and numerical simulation studies on composite nuclear fuel design are increasing, demonstrating its potential application in next-generation advanced nuclear fuels. However, the rational distribution of the metallic phase within the composite fuel remains a key scientific issue. If the distribution of the heat-conducting phase is uneven or ineffective heat conduction channels are not formed, its advantages cannot be fully realized. Current designs primarily rely on experience or simple geometric distributions, making it difficult to achieve global optimization of thermal conductivity based on actual operating conditions and design requirements.
[0004] Therefore, in order to fully utilize the improved heat transfer performance of enhanced thermal conductivity materials, it is crucial to adopt topology optimization methods to set different heat transfer objective functions and constraints for different heat transfer requirements, and obtain the optimal distribution law of each material in composite fuel. This is also of a positive effect on improving the long-term service performance of nuclear fuel elements and the safety requirements under accident conditions. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a design method for multi-material composite nuclear fuel elements based on heat transfer topology optimization. This method transforms the heat transfer design of composite fuel from an engineering problem into a mathematical problem, enabling composite fuel design schemes under different thermal design requirements.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: A design method for multi-material composite nuclear fuel elements based on heat transfer topology optimization includes the following steps: S1: Establish an initial two-dimensional or three-dimensional thermal conduction model for the composite nuclear fuel element structure, select a thermal conduction topology optimization design objective, and determine the input parameters for the initial two-dimensional or three-dimensional thermal conduction model. The initial two-dimensional or three-dimensional thermal conduction model includes: a design region for calculating thermal conduction, a topology optimization region for arranging nuclear materials and enhanced thermal conductivity materials within the design region, and a non-topology optimization region. The input parameters include design condition influence parameters and nuclear fuel element self-influence parameters. Design condition influence parameters include: coolant boundary conditions, burnup conditions, heat source power and distribution conditions. Nuclear fuel element self-influence parameters include: material thermal property parameters and fuel element structural parameters. By constructing a basic thermal conduction model and comprehensively defining the design region and input parameters, a precise mathematical and physical basis is provided for subsequent topology optimization. The purpose is to transform the complex design problem into a boundary value problem with clear boundary conditions, ensuring that the optimization process is carried out under real physical constraints.
[0007] S2: Based on the initial two-dimensional or three-dimensional heat conduction model and input parameters, establish a finite element calculation model for heat conduction of the composite nuclear fuel element; according to different design conditions and design objectives, perform heat transfer performance analysis on the finite element calculation model for heat conduction of the composite nuclear fuel element and obtain the objective function value; the purpose of obtaining the objective function value through finite element calculation is to provide a quantitative performance evaluation benchmark for topology optimization iteration; its advantage is that it can perform high-fidelity numerical simulation of heat transfer behavior under various complex conditions, overcome the technical obstacles of traditional analytical methods in handling complex boundaries and nonlinear material properties, and provide a data foundation for subsequent accurate sensitivity calculation.
[0008] S3: Based on the topology optimization objective of the composite nuclear fuel element under the heat transfer design requirements, the heat conduction calculation model of the composite nuclear fuel element is solved by topology optimization based on the two-way progressive structure optimization method or the variable density method. The material distribution structure in the heat conduction calculation model of the composite nuclear fuel element is obtained, and the topology model of the heat transfer structure of the composite nuclear fuel element after optimization is established. By introducing the topology optimization algorithm, the sensitivity of the objective function with respect to the material distribution is calculated and the material distribution is updated. It can automatically seek a better heat transfer structure topology model of the composite nuclear fuel element within the design space, effectively overcoming the technical obstacles of multi-material collaborative layout optimization in traditional design methods, thereby improving the utilization efficiency of enhanced heat-conducting materials and the overall heat conduction performance. S4: Based on the topological model of the heat transfer structure of the optimized composite nuclear fuel element, a new finite element calculation model for heat conduction of the composite nuclear fuel element is re-established. This involves setting corresponding material properties for different elements within the design region according to the topological model, followed by finite element calculations to obtain the design objective function value. The theoretical model obtained from topology optimization is then precisely reconstructed and numerically verified to evaluate its actual heat transfer performance. The aim is to establish a connection between the theoretical topological configuration and quantifiable performance indicators, verify the optimization results, and ensure that the design after each iteration has feasibility and performance feedback.
[0009] S5: Determine whether the topology model and design objective function value of the composite nuclear fuel element heat transfer structure after optimization in S4 meet the preset conditions. If not, repeat steps S3 and S4 until the preset conditions are met. If yes, output the topology model of the composite nuclear fuel element heat transfer structure. By establishing a convergence judgment mechanism, ensure that the optimization results reach the predetermined design indicators. The iterative process is used to realize the gradual evolution of the design scheme, which can effectively overcome the technical obstacle of being trapped in local optima in a single optimization and ensure that the final output topology model achieves better heat transfer performance in the global range.
[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes topology optimization technology to design composite nuclear fuel element structures under different heat transfer requirements, achieving a better spatial configuration of nuclear fuel materials and high thermal conductivity materials to meet different design requirements and objectives; 2. The composite nuclear fuel element heat transfer design method of the present invention is not limited to specific geometric structures, materials, operating conditions and design objectives. Therefore, it has strong versatility and scalability and can be applied to the design of different fuel systems, different heat-conducting materials and different types of fuel elements. 3. The topology optimization technology of this invention establishes a mathematical mapping relationship between material distribution and structural performance, and uses physical field response to iteratively adjust the material layout. Therefore, it can achieve a better distribution of heat transfer materials and structure under the objective function, and optimize heat transfer performance with the same amount of material, thus saving costs for engineering practice. Attached Figure Description
[0011] Figure 1 This is a flowchart of the design method for multi-material composite nuclear fuel elements based on heat transfer topology optimization according to the present invention; Figure 2 This describes the heat transfer model and boundary conditions for nuclear fuel elements in this embodiment of the invention. Figure 3 A schematic diagram illustrating the distribution structure of nuclear fuel and enhanced thermal conductivity material to represent the two-dimensional topology optimization results of this invention; Figure 4The diagram illustrates the distribution structure of nuclear fuel and enhanced thermal conductivity material to represent the three-dimensional topology optimization results of this invention. Detailed Implementation
[0012] The present invention will now be described in further detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present disclosure.
[0013] A design method and system for multi-material composite nuclear fuel elements based on heat transfer topology optimization is described in the overall flowchart below. Figure 1 .
[0014] This invention relates to a design method for multi-material composite nuclear fuel elements based on heat transfer topology optimization, comprising the following steps: S1: Establish initial two-dimensional and three-dimensional thermal conduction models for the composite nuclear fuel element structure, select the thermal conduction topology optimization design objective, and determine the input parameters used for the initial two-dimensional or three-dimensional thermal conduction model. The thermal conduction model and boundary conditions are as follows: Figure 2 As shown, the design region is a typical cylindrical nuclear fuel pellet region. The internal fuel material region has an internal heat source, while the reinforcing thermal conductivity material has no heat source. Heat is conducted from the inside of the pellet to the surface, and the outer surface can be subjected to temperature or convection boundary conditions. The nuclear fuel material and the reinforcing thermal conductivity material are uranium dioxide and metallic molybdenum, respectively, and their thermal properties are set separately in the finite element calculation. S2: Based on the initial two-dimensional or three-dimensional heat conduction model and input parameters, establish a finite element calculation model for the heat conduction of the composite nuclear fuel element; according to different design conditions and design objectives, analyze the heat transfer performance of the finite element calculation model for the heat conduction of the composite nuclear fuel element and obtain the objective function value. Specifically, the design condition for the finite element calculation model for the heat conduction of the composite nuclear fuel element is the normal operation steady-state heat transfer condition, the design objective is to minimize the overall heat dissipation weakness, the design variable is the material distribution, and the constraint condition is the volume fraction of high thermal conductivity material. For the steady-state heat conduction finite element equilibrium equation: in Q This is the global thermal load vector; K This represents the total thermal conductivity stiffness matrix; T This is the node temperature vector.
[0015] The objective function expression is: in C For structural heat dissipation weakness; and V i These are the element heat vector and the element volume, respectively. x i Design variables for the unit; i Number the units; V0 represents the total volume of the design area; f This represents the volume fraction of material 0 (indicating high thermal conductivity materials). n This represents the total number of units; This is the unit heat conduction matrix.
[0016] S3: Based on the topology optimization objective of the composite nuclear fuel element under the heat transfer design requirements, the topology optimization solution is performed on the heat conduction finite element model of the composite nuclear fuel element based on the two-way progressive structural optimization method or the variable density method. The material distribution structure in the heat conduction calculation model of the composite nuclear fuel element is obtained, and the topology model of the heat transfer structure of the composite nuclear fuel element after optimization is established. First, the sensitivity of the design objective of each unit to the design variables is calculated, and the topology structure is updated according to the topology optimization method, changing some units from nuclear materials to enhanced thermal conductivity materials or vice versa.
[0017] S4: Establish a finite element model based on the topology model of the heat transfer structure of the composite nuclear fuel element. That is, set the corresponding material properties of different elements in the design area according to the topology, and then perform finite element simulation calculation to obtain the design objective function value. For the above example, calculate the heat dissipation weakness value of the current topology model based on the temperature field and element heat conduction matrix obtained by finite element calculation, and use the current model as the topology before optimization in the next S3 step.
[0018] S5: Determine whether the topology model and design objectives of the composite nuclear fuel element heat transfer structure in S4 meet the preset conditions. If not, repeat steps S3 and S4 until the preset conditions are met; if yes, output the topology model of the composite nuclear fuel element heat transfer structure to obtain a composite nuclear fuel element design scheme with better heat extraction capability. After topology optimization iterative calculation, the two-dimensional and three-dimensional topology optimization results are illustrated as follows: Figure 3 and Figure 4 As shown (the black area in the figure represents high thermal conductivity material), the optimized heat transfer topology improves the overall thermal conductivity of the fuel through the arrangement of high thermal conductivity material structures that are connected to the boundary and include branches.
[0019] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of patent protection determined by the submitted claims.
Claims
1. A design method for multi-material composite nuclear fuel elements based on heat transfer topology optimization, characterized in that, Includes the following steps: S1: Establish an initial two-dimensional or three-dimensional thermal conduction model of the composite nuclear fuel element structure, select a thermal conduction topology optimization design objective, and determine the input parameters for the initial two-dimensional or three-dimensional thermal conduction model; wherein, the initial two-dimensional or three-dimensional thermal conduction model includes: a design region for calculating thermal conduction, a topology optimization region for arranging nuclear materials and enhanced thermal conductivity materials on the design region, and a non-topology optimization region; the input parameters include design condition influence parameters and nuclear fuel element self-influence parameters, the design condition influence parameters include: coolant boundary conditions, burnup conditions, heat source power and distribution conditions; the nuclear fuel element self-influence parameters include: material thermal property parameters and fuel element structural parameters; S2: Based on the initial two-dimensional or three-dimensional heat conduction model and input parameters, establish a finite element calculation model for heat conduction of composite nuclear fuel elements; according to different design conditions and design objectives, perform heat transfer performance analysis on the finite element calculation model for heat conduction of composite nuclear fuel elements, and obtain the objective function value; S3: Based on the topology optimization objective of the composite nuclear fuel element under the heat transfer design requirements, the heat conduction calculation model of the composite nuclear fuel element is solved by topology optimization based on the two-way progressive structure optimization method or the variable density method. The material distribution structure in the heat conduction calculation model of the composite nuclear fuel element is obtained, and the topology model of the heat transfer structure of the composite nuclear fuel element after optimization is established. S4: Based on the topology model of the heat transfer structure of the composite nuclear fuel element after optimization, a new finite element calculation model for heat conduction of the composite nuclear fuel element is re-established. That is, by setting the corresponding material properties of different elements in the design area according to the topology model, and then performing finite element calculations to obtain the design objective function value. S5: Determine whether the topology model and design objective function value of the composite nuclear fuel element heat transfer structure after optimization in S4 meet the preset conditions. If not, repeat steps S3 and S4 until the preset conditions are met. If yes, output the topology model of the composite nuclear fuel element heat transfer structure.
2. The design method for multi-material composite nuclear fuel elements based on heat transfer topology optimization as described in claim 1, characterized in that: Composite nuclear fuel materials include nuclear fuel materials, thermally conductive reinforcing materials, and structural materials. The thermophysical parameters of composite nuclear fuel materials include thermal conductivity, specific heat capacity, and density. The structural characteristics of nuclear fuel elements are the geometric dimensions of fuel pellets and cladding. The constraint parameters are the volume fraction of nuclear fuel materials or thermally conductive reinforcing materials and the structural dimensions of nuclear fuel elements.
3. The multi-material composite nuclear fuel design method based on heat transfer topology optimization as described in claim 2, characterized in that: The nuclear fuel material is uranium dioxide, and the heat-conducting material is molybdenum or a molybdenum alloy.
4. The design method for multi-material composite nuclear fuel elements based on heat transfer topology optimization as described in claim 1, characterized in that: The topology optimization design objectives are determined based on heat transfer requirements, including one or more of the following: minimum peak fuel temperature, minimum average fuel temperature, minimum internal fuel temperature gradient, minimum fuel temperature rise under emergency conditions, and minimum internal fuel heat storage.