节块内嵌离散纵标(SN)方法的算法研究及程序开发

Algorithm and Code Development of NEM Embedded with NDOM for 3D Core Transport/Diffusion Equations

介绍节块内嵌离散纵标(SN)方法求解三维堆芯中子输运/扩散方程的算法框架.在基于扩散理论的三维粗网节块展开方法(NEM)的算法体系中,用基于输运理论的径向二维细网节块离散纵标方法(NDOM)的内迭代过程,替代节块展开方法(NEM)内迭代的径向求解过程.该算法充分考虑了核电厂反应堆堆芯的三维结构特点,另一方面,也充分利用了已经成熟的三维粗网节块展开方法(NEM)和二维离散纵标方法(SN)的研究成果,同时有效避免了利用离散纵标方法(SN)求解三维中子输运方程所面临的计算内存和计算时间的瓶颈问题.编制开发二维多群节块离散纵标方法(NDOM)模块程序NSNM和三维多群节块展开方法(NEM)模块程序MGNEM,并以此为基础编制开发节块内嵌SN方法的模块程序HANWIND;其中,NSNM为HANWIND求解两维问题的功能模块.针对OECD/NEA-2D C5G7MOX基准问题以及两环路核电厂三维堆芯的数值验算结果表明,节块内嵌SN方法的算法开发及程序编制有效、切实可行.

An algorithm of 3D coarse mesh nodal expansion method （NEM） embedded with 2D fine mesh nodal discrete ordinate method （NDOM） is described. The main idea is to substitute radial part of NEM inner iteration, which is based on coarse mesh diffusion theory, with inner iteration of NDOM, which is based on fine mesh transport theory. Taking advantages of NEM and NDOM, the algorithm models efficiently heterogeneous features in radial planes of an NPP reactor core and takes less computer memory and computation time. Two prototype codes, NSNM and MGNEM, for the algorithm based on 2D multi-group NDOM and 3D multi-group NEM are developed. A computer code named HANWIND is integrated based on former codes. Numerical experiments on benchmark problem OECD/NEA-2D C5GTMOX and a self-estab- lished benchmark problem based on 3D core of 2-loop NPP reactor are shown.