基于求积组局部细化技术的SN屏蔽计算方法

摘要

辐射屏蔽设计是保证核装置安全性的重要组成部分,离散纵标法是屏蔽计算的主要方法之一.在具有狭长孔道的屏蔽问题中,由于中子角通量密度呈强各向异性分布,特别在孔道内其分布存在极大峰值,传统求积组难以实现计算精度与效率之间的平衡.为此,本文基于勒让德-切比雪夫求积组的离散特点,研究局部范围内多层极角细化技术,提高求积组积分角通量密度的精度.在极角细化的基础上,进一步研究偏倚求积组以提高计算效率,并开展相关收敛分析.对国际权威基准题Kobayashi的测试分析表明,极角细化技术可有效提高带有孔道屏蔽问题的计算精度.%The radiation shielding design is an important part to ensure the safety of nuclear installations and the discrete ordinates method is one of main methods for shielding calculation.For shielding problems with long narrow gaps,the neutron angular flux distribution is highly anisotropic,especially highly forward-peaked in gaps.It is difficult to balance computational accuracy and efficiency for traditional discrete quadrature sets.A multi-level angular refinement technique for polar angle was developed based on Legendre-Chebyshev quadrature sets.The accuracy of low-order quadrature sets was enhanced on integrating angular flux by the refinement technique.Biased sets were also constructed to improve efficiency and asymptotic analyses about these sets were discussed.Seen from the results on the Kobayashi benchmark problem 2 of half scattering case,this technique can improve scalar flux accuracy in the gap.