基于蒙特卡罗抽样的活化中子能谱测量不确定度分析

摘要

The uncertainty analysis is a key link in activation neutron spectrum measure‐ment .According to SAND‐Ⅱ activation neutron spectrum unfolding process ,an uncer‐tainty analysis Monte‐Carlo method of neutron spectrum measurement based on cross‐section covariance ,activation rate and prior spectrum information was presented .First , the sampling method of cross‐section covariance based on linear transformation was built . Then , the error was computed with MCNP , and the uncertainty of prior spectrum was obtained using iteration method .Finally ,combining uncertainty of activa‐tion rate measurement ,the neutron spectrum uncertainty using Monte‐Carlo sampling algorithm was calculated . In the verification of this method with 252 Cf spontaneous fission spectrum ,its uncertainty analysis result was more comprehensive than that of traditional method .The uncertainty analysis of a neutron spectrum measurement for Xi’an Pulsed Reactor was analyzed .The analysis result shows that the method is more conservative .%不确定度分析是活化法测量中子能谱的关键环节。本文针对SAND‐Ⅱ活化中子解谱过程，给出了一种基于先验谱、活化率和截面协方差的中子能谱测量不确定度蒙特卡罗分析方法。首先，建立了基于线性变换的截面协方差抽样方法；然后，利用MCNP计算了误差，使用迭代方法估计了先验谱不确定度；最后，结合活化率的测量不确定度，利用蒙特卡罗抽样算法计算了中子能谱的不确定度。利用锎源自发裂变谱对该方法进行了验证，与传统方法相比，不确定度分析结果更为准确。对西安脉冲堆某次中子能谱测量结果进行了测量不确定度分析，结果表明该方法更具保守性。