摘要
蒙特卡罗方法或离散纵标法模拟多群中子输运方程,散射角分布通常按Legendre级数展开,取L阶截断近似。当L较小时,近似角分布在[-1,1]定义域的多处出负,面积不归一,进而导致非物理解。文章针对这一问题,利用矩和Legendre系数等价关系,给出离散广义Gauss求积组,并用该求积组作节点构造等概率阶梯函数,逼近实际角分布,从而消除非物理解。计算取得了与实验和连续截面蒙特卡罗MCNP程序一致的结果。
The scattering angular distribution of the multigroup neutron transport equation, which is simulated by MonteCarlo method or discrete ordinate method, is usually expanded by Legendre series. Due to the Lorder truncated approximation, especial for L not enough large, the approximate angular distribution is negative over the range interval and nonunity by area. It leads to the nonphysics solution. In the paper, a generalized Gaussian quadrature discrete angle group is obtained by means of the equivalence of moment and Legendre coefficient. They are used as nodes of equally probable step function to approach real angular distribution, and then the nonphysics solution is avoided. The calculation results are the same as experiments and results of MCNP MonteCarlo code with continuous crosssection.
出处
《原子能科学技术》
EI
CAS
CSCD
2003年第5期405-410,共6页
Atomic Energy Science and Technology
基金
中国工程物理研究院基金资助项目(YF15)
关键词
中子
散射角
分布
Legendre级数
出负
阶梯函数
scattering angular distribution
L-order truncated approximation
gen-eralized Gaussian quadrature
step function to approach
