组件计算程序PANDA研发及初步验证

PANDA是上海核工程研究设计院研发的压水堆组件计算程序。该程序采用基于特征线方法（MOC）的一步化计算流程,即在不引入能群压缩和栅元均匀化的情况下直接进行组件层面的两维非均匀输运计算。多群数据库采用基于ENDF/B-VI制作的70群结构中子数据库,基于ENDF/B-VII的新版数据库也正在开发中。共振自屏计算采用了空间相关丹可夫方法（SDDM）,既具备燃料芯块分区计算的能力,又保留了传统Stammler方法的计算效率。多群非均匀输运计算采用二维模块化MOC方法,并辅以双重粗网有限差分(CMFD)加速技术,具有良好的计算精度和效率。对传统线性子链解析（TTA）方法以及多种矩阵指数方法进行了研究,选取了适合PANDA程序燃耗链的燃耗方程求解技术。基于以上基本模型开发了PANDA程序,并从程序模块、总体集成和核设计程序系统确认等三个层面,初步验证了PANDA程序的计算性能,表明了PANDA程序的工程设计计算能力。

Development and verification for the lattice code PANDA

The lattice code is an important component of the nuclear design code system. It generates tabulated cross section sets for reactor neutronics calculations. The development and improvement of lattice codes are always significant topics in reactor physics. The PANDA code is a PWR lattice code developed by Shanghai Nuclear Engineering Research and Design Institute (SNERDI). In PANDA, the one-step calculation flow based on Method of Characteristics(MOC) is utilized, which means the 2D heterogeneous transport calculation is performed without any group collapse and cell homogenization. The multi-group library is processed from the evaluated nuclear data library ENDF/B-VI under a 70-group energy structure, and an improved version based on the ENDF/B-VII library is under development. The Spatially Dependent Dancoff Method (SDDM) is applied to treat the resonance self-shielding phenomena. It supports concentric sub-ring mesh divisions in a fuel pellet, but still preserves the same level of efficiency as the conventional Stammler method. Modular 2D MOC with two-level Coarse Mesh Finite Difference (CMFD) acceleration is used as the heterogeneous transport solver, which has favorable accuracy and efficiency. Various matrix exponential methods are studied to solve the Bateman burnup equation. The PANDA code is developed on the basis of these methodologies. The numerical results preliminarily demonstrate that the PANDA code has the basic ability for engineering computations.