基于广义微扰理论的蒙特卡罗输运-燃耗耦合计算方法研究

Advanced nuclear energy system presents higher accuracy requirements and geometric applicability for neutron transport coupled burnup calculation. The traditional deterministic transport coupled burnup calculation method presents great challenges of the geometric applicability and the multi-spectrum applicability of the multi-group cross section libraries in the advanced nuclear energy system. Monte Carlo (MC) transport coupled burnup calculation method is a powerful tool to cope with the challenge. It has the advantages of good geometry adaption and the application of continuous energy cross section libraries, but the balance between calculation accuracy and efficiency is the current urgent problem. This fund intends to adopt the generalized perturbation theory to obtain the mutual influence relationship between transport and burnup calculation from basic model, and then accurately simulates the change of the neutron parameters within the time step in burnup calculation. Through the mutual influence relationship, the time step size is adaptively divided, and the calculation accuracy and efficiency are ultimately improved. The work consists of three parts: 1) Study a general MC sensitivity analysis method based on generalized perturbation theory. 2) Study a calculation method of the burnup sensitivity coefficient in MC burnup calculation. 3) Study an adaptive method of step size in MC burnup calculation. This project is aiming to research and develop an accurate and efficient MC burnup coupling scheme for physical design of nuclear energy systems, and it is promising in the academic research and engineering applications.

新型核能系统对中子输运-燃耗耦合计算提出了更高的计算精度和几何适用性的要求。传统的确定论输运-燃耗耦合计算方法在几何处理能力和多群常数库的适用性上存在着巨大的挑战。蒙卡输运-燃耗耦合计算是应对该挑战的有力工具，其在几何和能谱适用性方面具有显著的优势，但精度和效率间的平衡是目前急需解决的问题。本项目拟从输运-燃耗计算的基本模型出发，采用广义微扰理论获取耦合计算过程中输运计算和燃耗计算的相互影响关系，从而精确模拟燃耗步长内中子学参数的变化情况，并对燃耗步长进行自适应划分，最终提高计算精度和效率。拟开展的工作主要包括三个方面：1）研究基于广义微扰理论的蒙卡灵敏度分析方法。2）研究蒙卡燃耗灵敏度系数的计算方法。3）研究蒙卡燃耗计算中燃耗步长的自适应划分方法。本项目旨在研发可用于新型核能系统堆芯设计的精确高效的蒙卡输运-燃耗耦合计算方法，在学术研究和工程应用上都颇具前景。

新型核能系统对中子输运-燃耗耦合计算提出了更高的计算精度和几何适用性的要求。蒙卡输运-燃耗耦合计算是应对该挑战的有力工具，其在几何和能谱适用性方面具有显著的优势，但计算精度和效率间的平衡是目前急需解决的问题。本项目从输运-燃耗计算的物理模型出发，开展了蒙卡输运-燃耗耦合计算方法的研究。首先，研究了基于碰撞历史法的蒙卡灵敏度计算方法，能够准确计算输运计算中的广义响应函数对核数据的灵敏度系数。其次，重点研究了不同形式CRAM方法的步长包容性、材料辐射特性的计算方法，并通过一阶广义微扰理论实现了不同响应函数对核数据灵敏度系数的精确计算。最后，建立了基于广义微扰理论的输运-燃耗耦合策略，能够有效的减少输运计算次数，提高计算效率，同时保持良好的计算精度。通过本项目的研究，旨在解决新型核能系统中蒙卡输运-燃耗耦合计算中的效率困境，提升蒙卡输运-燃耗耦合计算方法的工程实用性，同时为发展新一代堆芯的输运-燃耗耦合计算方法奠定一定的理论基础。