γ能谱固体样品的自吸收修正研究  

Study on self-absorption corrections of γ spectrum for volume samples

作　　者：张磊 ZHANG Lei(Shanghai Radiation Environmental Safety Technology Center,Shanghai 200065,China)

机构地区：[1]上海市辐射环境安全技术中心,上海200065

出　　处：《核技术》2021年第9期45-50,共6页Nuclear Techniques

基　　金：上海市生态环境局青年科研项目(No.2021-013)资助。

摘　　要：在辐射环境质量测量或者应急测量中,不同样品的介质组成差别很大,而实验室标准源是有限的,为了提高待测样品的分析准确性,对样品进行自吸收修正是十分必要的。采用4种不同的自吸收修正方法对含有不同核素的土壤样品进行实验测试分析,结果表明:蒙特卡罗抽样自吸收修正方法最接近样品内射线近距离入射探测器的实际情况,所以该方法可作为低能核素自吸收的精确修正;如果样品内介质组成未知,可用平均有效长度修正法对中高能段的待测核素进行自吸收修正,但低能核素的相对偏差较大;垂直入射修正法和点探测器修正法也适用于中高能段的自吸收修正,这两种方法对低能核素的自吸收修正结果优于平均有效长度法,与真值的相对偏差在±8%以内。[Background]In radiation environmental quality measurement or emergency measurement,most samples have different media composition,and the laboratory standard sources are limited.[Purpose]This study aims to improve the analysis accuracy of different samples by self-absorption correction of the samples.[Methods]Four different self-absorption correction methods,were used to test and analyze soil samples containing different nuclides to calculate the self-absorption correction of volume samples.The geometric dimension of samples was the same as the standard solid point sourceø75 mm×70 mm.The point detector correction method,the mean effective length correction method and the vertical incident correction method were employed to simplify the detector,the sample box and the incident angle,respectively,whilst the Monte Carlo correction method was closest to the actual situation of the γ-ray near-incidence detector in the sample.[Results]The Monte Carlo correction method has the least deviation for low energy nuclides which is within±8%between the correction results and true values,better than that of mean effective length method.The point detector correction method,the vertical incidence correction method,and the mean effective length correction method have small deviation for middle and high energy nuclides,but the deviations of these three methods for low-energy nuclides are large.[Conclusions]The Monte Carlo self absorption correction method can be used as an accurate correction for the self-absorption of low-energy nuclides.If the composition of the medium in the sample is unknown,the mean effective length method can be used to calibrate the self-absorption of the measured nuclides in the middle and high energy parts.The vertical incidence method and point detector method are also suitable for self-absorption correction of the middle and high energy parts.The relative deviation between the correction results and true values is within±8%in the low-energy part,which is better than the mean effective length method.

关 键 词：γ 能谱 质量减弱系数 自吸收修正 

分 类 号：TL817.2[核科学技术—核技术及应用]