非线性节块展开法

Nonlinear nodal expansion method

非线性节块展开法是一种快速计算反应堆物理参数的节块方法。与有限差分法相比，它具有速度快、精度高的特点；与另一种节块法—Ｇｒｅｅｎ函数展开法相比，它又保留了有限差分法的优点：不但可以得到有效倍增因子、功率分布等参数，还可以得到差分方程的系数矩阵，因而十分适合与广义微扰理论（ＧＰＴ）相结合以获得更快的计算速度，应用于堆芯燃料管理优化中。通过两个二维基准问题的检验计算，比较了非线性节块展开法和Ｇｒｅｅｎ函数展开法程序的速度与精度，结果表明两个程序基本相当，非线性节块展开法可以满足实际应用的需要。

Nonlinear nodal expansion method (NNEM) is a rapid nodal method caculating reactor physics parameters. Compared with finite difference method, it is of characters of fast speed and high precision; compared with nodal Green function method (NGFM), however, it retains good points of the finite difference method, that is, not only parameters of effective multiplier factor and power distribution but also element matrices of difference equations can be acquired. Because of these characters, NNEM is easy to be combined with Generalized Perturbation Theory (GPT), forming a fast method applicable in reactor fuel management optimization. Calculations of two benchmark problems show that speed and precision of the NNEM and NGFM are comparable and NNEM can satisfy requirement of real engineering application.