铀材料快中子多重性测量方程推导

Derivation of fast neutron multiplicity measurement equation of uranium material

随着国际核裁军的深入推进,针对核材料的属性认证愈发受到关注.快中子多重性测量技术作为一种无损检测技术,采用闪烁体探测器进行测量,在军控核查体系中发挥着越来越重要的作用.目前对于钚材料的快中子多重性测量方法发展较为成熟,对于铀材料的快中子多重性分析模型和测量方程还处于发展中.为建立铀材料的有源快中子多重性测量方程,本文在中子多重性分析方程推导过程的基础上,根据铀钚材料二者物理过程的区别,不考虑(α,n)反应,考虑快中子散射串扰的影响,利用概率母函数完成铀材料快中子多重性测量方程的推导.在此基础上,为检验测量方程的有效性,利用Geant4搭建一套3×8的井型探测系统进行模拟测量.通过分析对比耦合系数与增殖系数的拟合函数关系、多重计数率、质量求解偏差,证实了测量方程的可靠性和准确性,对快中子多重性技术的发展具有重要意义.

With the deepening of international nuclear disarmament,attribute certification for nuclear material has attracted more and more attention.The fast neutron multiplicity measurement technology—a non-destructive testing method—uses scintillator detector for measurement,which plays a more and more important role in the military control verification system.At present,the fast neutron multiplicity measurement methods for plutonium materials are relatively mature,but the fast neutron multiplicity analysis model and measurement equations of uranium materials are still under development.In order to establish the active fast neutron multiplicity measurement equation for uranium materials,based on the derivation process of neutron multiplicity counting analysis equation,in this paper uses the probability generating function is used to derive the fast neutron multiplicity measurement equation of uranium materials according to the difference between the physical processes of uranium and plutonium materials,without considering the reaction of(α,n)or the influence of fast neutron scattering crosstalk.On this basis,in order to verify the validity of the measurement equation,Geant4 is used to build a 3×8 well-type detection system for simulation measurement.The fitting function relationship between the coupling coefficient and the value-added coefficient,the multiplicity counting rate,and the solution deviation of the quality are analyzed,thereby confirming the reliability and the accuracy of the measurement equation,which is of great significance in developing the fast neutron multiplicity technology.