基于中国散裂中子源反角白光中子束线的天然锂中子全截面测量

锂是熔盐堆燃料载体盐的主要材料之一,其中子核反应截面数据是熔盐堆芯中子物理设计及堆芯长期安全运行中的重要基础数据.本工作基于中国散裂中子源反角白光中子束线(CSNS Back-n)飞行时间谱仪,利用中子全截面测量谱仪(NTOX),采用透射法测量了天然锂中子全截面.实验中,中子飞行距离约为76.0 m,采用15.0 mm和8.00 mm两种厚度的天然锂金属样品,在0.4 e V—20 Me V中子能量范围内测得了统计计数较好的中子全截面.特别是在ke V及以下能区增补了实验数据,为锂的核数据评价工作提供了更加丰富和可靠的实验数据.在此基础上,采用1/v律和R矩阵理论对Me V以下能区的新测量数据进行了理论分析,获得了7Li和6Li在260 ke V能量附近的中子共振参数.

Measurement of total neutron cross section of natural lithium at China Spallation Neutron Source Back-n facility

Lithium is one of the main materials of fuel carrier salt in molten salt reactors.Its neutron cross section provides an important basic datum for physical design of molten salt reactor core and for evaluating the safety of the core during operation.The total neutron cross sections of natural lithium samples with thickness values of 8.00 mm and 15.0 mm are measured,respectively,in an energy range from 0.4 eV to 20 MeV by using a neutron total cross section spectrometer(NTOX)with the transmission method at the Back-n white neutron source of China Spallation Neutron Source(CSNS Back-n)with a 76.0 m time-of-flight path.High quality experimental data are obtained,especially in the energy region of keV and below,which supply a significative supplement of the data,thereby providing more abundant and reliable experimental data for nuclear data evaluation of lithium.Additionally,a theoretical analysis is carried out under the guidance of 1/v law and the multilevel R-matrix theory.And the resonance parameters of n+6,7Li reaction around the energy of 260 keV are extracted from the measured data.