快中子多重性计数器测量Pu样品质量的模拟计算

Simulation of Pu Sample Mass Measurement Based onFast Neutron Multiplicity Counter

依据Pu材料自发裂变和诱发裂变原理,推导了钚材料的快中子多重性测量方程。采用蒙特卡罗方法和Geant4程序,对含有24个探头的3×8液闪探测系统在有效测量空间范围内的快中子探测效率进行了模拟计算,分析了该系统探测效率的均匀性;在此基础上,针对5种不同丰度、不同密度的钚样品,利用本文建立的钚材料快中子多重性测量方程,计算得到了样品质量修正因子随增殖系数M及(α,n)中子与自发裂变中子之比α变化的拟合方程,并用这些拟合方程对质量小于5 kg的Pu材料的计算质量进行了修正。结果表明,修正后,计算质量与样品质量之间的相对偏差小于6%。

Based on the principle of spontaneous fission and induced fission of Pu material,a fast neutron multiplicity measurement equation of Pu material is derived.The fast neutron detection efficiency of a 3×8 liquid scintillation detection system with 24 liquid scintillations in an effective measurement space is simulated and calculated by using Monte Carlo method and Geant4 program,and the uniformity of the detection efficiency of the system is analyzed.The fast neutron multiplicity measurement equation of Pu materials is used for five Pu samples with different abundances and densities.The fitting equations of the sample mass correction factor with the self-multiplication factor M,and the ratio of(α,n)neutrons to spontaneous fission neutronsαare obtained.The calculated mass of Pu materials with a mass of less than 5 kg is modified by the fitting equations.The results show that the deviation between the calculated mass and the real mass is less than 6%.