基于CSG和OpenMP的复杂几何输运计算程序开发及验证

Development and Verification of Transport Code for Complicated Geometry Based on CSG Formula and OpenMP

为了适应材料几何布置越来越复杂的小型研究堆计算需求,基于构建实体几何理论和矩阵特征线方法,开发了具有复杂几何输运计算能力的2维特征线程序MOCAGE,并采用OpenMP并行编程模型对几何前处理中的特征线追踪进行并行化设计。通过不规则几何问题以及3种不同控制棒布置形式的HTTR基准题对程序的特征线追踪能力与计算精度进行评估,给出了计算结果与MCNP5多群计算参考值的相对误差。结果表明:所开发的程序能够正确实现对复杂对象的几何建模并进行特征线追踪,计算结果与参考值符合较好,精度满足程序验证要求,采用OpenMP并行编程能显著减少几何预处理时间。

The small research reactor which exhibits the features of high heterogeneity, strong absorption regions and complicated geometry challenges the numerical computation capabilities of existing neutronics codes. To overcome the restriction of geometry, the transport code MOCAGE, based on the constructive solid geometry formulation（CSG） and matrix method of characteristics, has been developed in the present study, and the track tracing has been parallelized applying the OpenMP programming model. The irregular geometry problem and HTTR benchmark problem with three configurations of control rods has been used to verify the capability of characteristic line tracing and to evaluate the code＇s numerical accuracy for complicated geometry. The system effective multiplication factor, the normalized fission densities of fuel pins, and the normalized neutron absorption densities of burnable poison rods and control rods have been calculated by the developed code. Meanwhile the comparison with MCNP5 reference solutions has been performed, and the results demonstrated that the developed code can model the complicated geometry and trace the characteristic lines correctly, and excellent agreements were achieved with respect to the aforementioned parameters. The time consumption of tracing procedure has been reduced significantly using the OpenMP.