典型屏蔽材料的中子反射、透射及吸收特性模拟

Simulation of Neutron Reflection,Transmission and Absorption Performance of Typical Shielding Materials

为系统分析典型材料的中子屏蔽性能,指导射线屏蔽防护设计,采用蒙特卡罗方法计算了不同厚度的聚乙烯、含硼聚乙烯、铁及普通混凝土对不同能量中子的反射因数、透射因数及吸收因数。结果表明,中子反射因数和吸收因数均随屏蔽体厚度的增大而增大,当屏蔽体厚度增加到一定值时,中子反射因数和吸收因数均趋于饱和。中子饱和反射因数主要受中子截面随能量的变化规律影响,中子总截面随能量减小而增大的屏蔽材料,其饱和反射因数较小,聚乙烯、普通混凝土和铁对1 MeV中子的饱和反射因数分别为41.0%,71.3%和84.3%;屏蔽材料的中子饱和反射厚度与中子在屏蔽材料中自由程的比值,随中子饱和吸收因数的增大而减小。

To analyse neutron shielding performance of typical shielding materials and guide the shielding design,this paper calculated the neutron reflection,transmission and absorption factors of polyethylene,boron containing polyethylene,iron and ordinary concrete with various thickness shielding for neutrons with different energy by using Monte Carlo method.The results show that,both the neutron reflection factor and the absorption factor increase with the increase of shielding material thickness,and when the thickness increases to a certain degree,both tend to saturation.Neutron saturated absorption factor is mainly affected by the rules of neutron cross section varying with neutron energy.For neutron shielding materials,when their total neutron cross sections increase with the decrease of neutron energy,their neutron saturated reflection factors are relatively small. The saturated reflection factor of polyethylene,ordinary concrete and iron for 1 MeV neutron are 41.0%,71.3% and 84.3%,respectively.The ratio of saturated reflection factor to neutron mean free path decreases with the increase of thickness of shielding materials.