针对球床的三维特征线方法几何建模研究

Geometry Modeling of 3D Method of Characteristics for Pebble-bed

特征线方法通过在计算区域密置特征线来计算角通量,对于计算区域的材料分布和几何结构没有要求,因此特征线方法的几何处理能力受制于几何描述模块对于各种几何区域的描述能力。基于体素构造(CSG)方法,开发了三维特征线程序MOCP的几何描述模块。该几何描述模块可描述随机分布的球床。针对球形燃料的网格划分方式进行了研究,临界球的计算结果表明,当径向网格超过30层时,keff的相对误差小于0.1%。通过对几何描述方式的改进大幅提高了三维特征线追踪的效率,并且实现了在各种形状边界上的特征线布置。

In MOC(method of characteristics),angular flux is calculated by sweeping over all the tracks densely arranged in the district.The sweeping process is independent of material distribution and geometry.As a result,the capability of treating different kinds of geometry structures of MOC is limited by the capability of geometry modeling modular.The geometry modular of the code MOCP(method of characteristics for high temperature pebble-bed reactor)was developed based on CSG(constructive solid geometry)method.The geometry modular of MOCP is capable of describing the stochastic distributed pebble-bed.The meshing method of spherical fuel was studied.The result shows that relative error of k eff of a critical sphere is less than 0.1%when the critical sphere is divided into more than 30 layers.Furthermore,the 3D ray tracing efficiency is greatly improved by optimizing the geometry tree and MOCP is able to arrange track on the different shapes of the geometries including cube,cylinder and sphere.