柱形金属铀次临界系统瞬发中子衰减常数测量  

Determination of Prompt Neutron Decay Constant of Cylindrical Metal Uranium Subcritical Assembly

作　　者：宋凌莉[1,2] 金宇[1,2] 李建胜[1,2] 周浩军[1,2] 

机构地区：[1]中国工程物理研究院中子物理学重点实验室,四川绵阳621900 [2]中国工程物理研究院核物理与化学研究所,四川绵阳621900

出　　处：《原子能科学技术》2012年第B09期383-386,共4页Atomic Energy Science and Technology

基　　金：国家自然科学基金资助项目(11175164);中国工程物理研究院科技发展基金资助项目(2011B0103015)

摘　　要：次临界核系统的瞬发中子衰减常数α与反应性有着重要联系。采用252 Cf随机脉冲源法测量了一柱形金属次临界系统的瞬发中子衰减常数。为对源中子的影响进行分析,借助蒙特卡罗模拟方法建立模型进行了模拟,对源直穿中子和核系统瞬发中子时间分布特性进行了比较,分析了源中子对瞬发中子衰减曲线的影响。模拟结果表明,对该柱形金属铀系统,源中子注入100ns后源直穿中子对核系统瞬发中子的影响可忽略。根据分析结果选取了合理起始道,对实验数据进行单指数最小二乘拟合,得到该次临界系统的α为15.5μs-1。Prompt neutron decay constant α is an important parameter to determine the reactivity of subcritical assemblies.Randomly pulsed neutron measurements were performed to obtain α of a subcritical assembly composed of cylindrical uranium.Monte Carlo simulations,with its flexibility of recording neutrons of different origins and different energy,were used to analyze the influence of directly transmitted source neutrons on the prompt neutron decay.The simulation results show that the influence of directly transmitted source neutrons to the prompt neutron decay can be neglected after 100 ns for the cylindrical assembly.According to the simulation results,the initial channel of the experimental prompt neutron decay curves was selected as 100 ns and the data were fitted to a single exponential decay.The experimental results of α for the uranium metal subcritical assembly is 15.5 μs-1.

关 键 词：瞬发中子衰减常数 次临界 源中子 拟合起始道 

分 类 号：O571.1[理学—粒子物理与原子核物理]