用多群蒙特卡罗方法计算快中子核临界Keff和通量密度

摘要

用多群蒙特卡罗方法对快中子核裂变系统进行了临界计算。有效增殖因子keff的计算值与实验结果符合。计算所得中子通量密度的空间分布在球形裂变系统中随半径增大单调下降。中子通量密度的能量分布在由高浓缩铀组成的活性区内呈单一能量极大值，其对应能量对于裸球核裂变系统和具有反射层裂变系统分别为0．35MeV和0．25MeV，而在由天然铀组成的反射层中在0．1MeV附近出现能量双峰。由通量密度所得中子能谱在无反射层球形裂变系统中随半径增加变硬，在有反射层球形裂变系统中随半径增加变软。%The fast neutron spherical critical assemblies are analyzed bymeans of the Monte-Carlo method with multi-group section data. The calculated keff are consistent with the experimental results. The neutron flux density versus energy distribution presents a single maximum in the core made up of high enriched uranium and the distribution presents two maximums in the reflecting layer made up of natural uranium. The neutron spectrum hardens as the radius increases in the bare spherical assembly and softens as radius increases in the assembly with reflecting layer.