基于多次碰撞源的屏蔽计算方法研究

离散纵标（SN）方法在求解过程中将空间变量和角度变量进行离散，空间变量和角度变量的离散误差控制对保证计算精度至关重要。本文基于射线追踪研究了多次碰撞源方法，通过计算在选定区域内粒子发生多次碰撞的通量密度，将孤立源等效为计算模型内的分布源进行离散纵标输运计算。选取自设屏蔽问题及Kobayashi基准题进行测试验证并对结果进行分析。数值结果表明，自设屏蔽问题中多次碰撞源方法较首次碰撞源方法能有效缓解二次射线效应问题；Kobayashi基准题计算结果与基准值相对误差的均方根小于3%。多次碰撞源方法有效地减弱了离散误差，提高了屏蔽计算的准确性与可靠性。

Shielding Calculation Method Based on n’th Collision Source

The discrete ordinates (SN) method discretizes directly spatial and angular variables, which results in angular and spatial discretization errors. How to effectively control discretization errors is essential to assure calculation accuracy. An n’th collision source method based on the ray tracing method was developed by calculating the flux density of particle collisions in a selected region. The isolated source was equivalent to the fixed source distributed throughout the computational model for discrete ordinates transport calculation. Self-designed shielding problem and Kobayashi benchmark problem were used to verify and analyze the adaptability of n’th collision source method. The results show that the n’th collision source method can effectively alleviate the secondary ray effect problem compared with the first collision source method in the self-designed shielding problem. As for the Kobayashi benchmark problem, the root mean square (RMS) of the relative error between the calculation result and the reference value is less than 3%. The n’th collision source method effectively reduces the discretization errors and provides better accuracy and reliability for the shielding calculation.