基于蒙卡模拟的分段γ扫描无源效率刻度方法  

A passive efficiency calibration method with Monte Carlo simulation in segmented gamma scanning

作　　者：郑洪龙 庹先国[2] 苟家元[1] 吴耀 左伟[1] 郭雨非 何琳[1] 刘艳芳[1] 黄聪 阳林锋[1] 刘伟[1] Zheng Honglong;Tuo Xianguo;Gou Jiayuan;Wu Yao;Zuo Wei;Guo Yufei;He Lin;Liu Yanfang;Huang Cong;Yang Linfeng;Liu Wei(Sichuan Engineering Laboratory for Nuclear Facilities Decommissioning and Radwaste Management,Sub-institute of Nuclear Power Institute of China,Chengdu 610005,China;Fundamental Science on Nuclear Wastes and Environmental Safety Laboratory,Southwest University of Science and Technology,Mianyang 621010,China)

机构地区：[1]中国核动力研究设计院第一研究所,成都610005 [2]西南科技大学核废物与环境安全国防重点学科实验室,四川绵阳621010

出　　处：《强激光与粒子束》2020年第4期128-134,共7页High Power Laser and Particle Beams

基　　金：国家自然科学基金项目(41874213,41604154)

摘　　要：针对200 L核废物桶分段γ扫描(SGS)过程中的效率刻度问题,提出了一种效率刻度函数模型,采用MCNP程序计算不同基质密度和γ射线能量条件下的离散断层效率,经过多元非线性回归获取函数参数,从而建立效率刻度函数,实现核废物桶SGS断层效率刻度。对核废物桶样品进行实验分析,结果表明:对于桶内基质分别为密度0.310 g·cm^-3的硅酸铝、密度0.595 g·cm^-3的木质纤维,桶内核素分别为活度3.110×10^5 Bq的点源137Cs、活度1.371×10^5 Bq的点源60Co,在桶内仅有单个点源存在的核素分布极端不均匀情况下,桶内核素活度重建误差在-37.68%~31.52%范围内。本文的方法能够准确有效实现核废物桶SGS断层效率矩阵计算,并确定核废物桶内放射性核素活度,满足实际检测要求。In this work, an efficiency calibration function model is presented to calculate the efficiency of segment in segmented gamma scanning(SGS) for 200 L nuclear waste drum. Discrete SGS efficiencies are simulated with MCNP for different densities and gamma ray energies. Parameters of function are determined by using multivariate nonlinear regression method with the efficiencies. The SGS efficiency calibration function is constructed to calculate the efficiency matrix. Aluminum silicate with density of 0.310 g·cm^-3, wood fiber of 0.595 g·cm^-3, point sources 137Cs with activity of 3.110×10^5 Bq and 60Co of 1.371×10^5 Bq are used to construct samples of drum for SGS analysis. Result shows: for the extremely heterogeneous radioisotope distribution of only a point source placed at 8 different positions in the drum, errors of reconstructed activities are-37.68%~31.52%. Overall, the reconstructed activity is in agreement with the true activity. This method effectively and accurately achieves SGS efficiency calculation and reconstruction of activity.

关 键 词：核废物桶 分段γ扫描 蒙特卡罗 效率刻度 函数 MLEM算法 

分 类 号：TL814[核科学技术—核技术及应用]