函数展开计数在CLUTCH方法中的初步应用  

Preliminary Application of Function Expansion Tally in CLUTCH Method

作　　者：黄金龙 曹良志[1] 贺清明[1] 秦帅 吴宏春[1] HUANG Jinlong;CAO Liangzhi;HE Qingming;QIN Shuai;WU Hongchun(School of Nuclear Science and Technology,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学核科学与技术学院,陕西西安710049

出　　处：《原子能科学技术》2024年第3期563-572,共10页Atomic Energy Science and Technology

基　　金：中核集团领创科研项目;中核集团“青年英才”项目;中国科协青年人才托举工程项目(2019QNRC001)。

摘　　要：反复裂变几率(IFP)方法广泛应用于求解k特征值对连续能量核数据的灵敏度系数,然而IFP方法存在内存占用大的问题,因此CLUTCH方法被提出以解决该问题。但对于大规模问题,如压水堆全堆问题,基于网格的CLUTCH(CLUTCH-Mesh)方法存在权重函数不易收敛的问题。本文采用函数展开计数(FET)方法对CLUTCH方法中的权重函数进行统计(CLUTCH-FET)以解决该问题,函数展开计数选取的基函数是勒让德多项式。本文在蒙特卡罗粒子输运计算程序NECP-MCX中实现了IFP、CLUTCH-Mesh和CLUTCH-FET 3种方法,以IFP方法的计算结果作为参考解,对CLUTCH-Mesh和CLUTCH-FET方法的精度和效率进行了验证。数值结果表明:对于小规模问题,如Godiva和Flattop问题,CLUTCH-Mesh和CLUTCH-FET方法具有与IFP方法相当的精度,且计算效率较IFP方法更高;对于大规模问题,如AP1000全堆问题,CLUTCH-Mesh方法的计算精度下降,而CLUTCH-FET方法可保持较高的精度和计算效率,CLUTCH-FET方法的品质因子较IFP方法和CLUTCH-Mesh方法分别最多提高了5.2和6.0倍。The iterated fission probability(IFP)method and Contributon-linked eigenvalue sensitivity/uncertainty estimation via track-length importance characterization(CLUTCH)method are commonly used by many Monte Carlo codes for the sensitivity analysis of k-eigenvalue to continuous-energy nuclear data.The memory consumption of the IFP method is huge and the CLUTCH method is proposed to reduce the memory usage of the IFP method.However,it’s hard to tally sufficiently-converged importance weighting functions for the mesh-based CLUTCH(CLUTCH-Mesh)method for large-scale problems,such as AP1000 whole core problem,subsequently reducing the accuracy of sensitivity coefficients calculated by the CLUTCH method.Therefore,the function expansion tally(FET)was used to tally importance weighting functions in the CLUTCH(CLUTCH-FET)method in this paper.Legendre polynomial was selected as the basic function of FETs and both segmented FETs with low orders and the global FET with the high order were implemented.During the tally process of FETs,the spatial locations of particles should be projected into domains of definition firstly,and then the tally scores of function expansion coefficients were obtained and accumulated.By averaging function expansion coefficients among inactive cycles,the FET was finished.The FETs were used for both ancestor fission neutrons distribution in original generations and the averaged progenies of the ancestor fission neutron in asymptotic generations.Based on the method mentioned above,the IFP,CLUTCH-Mesh and CLUTCH-FET methods were implemented in Monte Carlo code NECP-MCX.The verifications were conducted among Godiva,Flattop and AP1000 whole core problems by comparing the sensitivity results of CLUTCH-Mesh method,CLUTCH-FET method and the IFP method,whose results were selected as the reference.The numerical results indicate that for small-scale problems,such as Godiva and Flattop problems,the CLUTCH-Mesh and CLUTCH-FET methods are able to calculate the sensitivity results with the same high precision as the

关 键 词：敏感性分析 CLUTCH方法 权重函数 函数展开计数 勒让德多项式 蒙特卡罗 

分 类 号：TL329[核科学技术—核技术及应用]