蒙特卡罗模拟CFETR中子输运计算中的全局减方差方法应用及对比  

Application and comparison of global variance reduction methods employed in Monte Carlo neutron transport for CFETR

作　　者：聂星辰[1] 李佳[1] 赵平辉[1] 祝庆军[2] 

机构地区：[1]中国科学技术大学核科学技术学院,合肥230027 [2]中国科学院等离子体物理研究所,合肥230031

出　　处：《核技术》2016年第3期38-43,共6页Nuclear Techniques

基　　金：磁约束核聚变国家特殊项目(No.2013GB108004;No.2015GB108002);国家自然科学基金(No.11175207)资助~~

摘　　要：在具有全局特性的蒙特卡罗输运精细计算的问题中,传统的MCNP(Monte Carlo N Particle Transport Code)局部减方差方法很难得到理想的计算结果,全局减方差方法(Global Variance Reduction,GVR)则是一种有效的解决方法。针对中国聚变工程试验反应堆(Chinese Fusion Engineering Testing Reactor,CFETR)的中子输运过程中减小全局方差的问题,将多种形式的GVR方法应用到柱状CFETR中子学模型的计算中。依据不同的中子分布信息,在算例中应用和对比了6种不同形式的GVR权窗,并对不同GVR方法的品质因子(FOMG)、标准差(σ)和有效计数率(Scoring)进行了分析。与AN(MCNPanalog method)相比,GVR方法的FOMG有很大的增长,误差在空间的分布也更加平缓,且具有更高的Scoring。在前人提出的全局减方差的基础上,在计算中应用一些新的GVR形式(能量、径迹数等),计算结果表明,基于中子通量的GVR方法的全局计算效率较AN提高了6.43倍。此外,基于中子能量的全局减方差方法也是一种可行的GVR应用形式,其与AN比较,计算效率提高了5.11倍。综上,基于中子通量的GVR方法具有最佳的全局减方差效果。Background： For the detailed Monte Carlo radiation transport, which possesses global characteristics, traditional MCNP Localized Variance Reduction （LVR） methods can hardly perform well. Global Variance Reduction （GVR） method is an effective way. Purpose： This study aims to decrease the global variance of Monte Carlo radiation transport calculations for Chinese Fusion Engineering Testing Reactor （CFETR）. Methods： According to different information of neutron distribution, six kinds of GVR methods were implied and compared in a cylinder CFETR neutronics model. Global figure of merit （FOM6）, standard deviation （a） and the percentage of scoring were analyzed. Based on predecessors＇ research, other kinds of new GVR methods （energy, tracks） were applied in this calculation. Results： In the point of GVR methods, FOMc increased dramatically, spatial variation inrelative errors was more gradual, and the scoring was higher, compared with AN. The GVR method based on neutron flux achieved the global calculation efficiency of 6.43 times that of AN. Apart from that, the GVR method based on neutron energy can also be a practical GVR kind, achieving the global calculation efficiency of 5.11 times that of AN. Conclusion： The GVR method based on neutron flux can performed best that has a well function of global variance reduction, achieving the global calculation efficiency.

关 键 词：全局减方差 权窗 蒙特卡罗 MCNP 中子学 

分 类 号：TL62[核科学技术—核技术及应用]