分层γ扫描(SGS)测量分析是一种无损检测技术, 是桶装核废物定性、定量分析的重要手段。实际分析过程中, 随着放射性核素所在的位置变化, 对应每层不同的位置HPGe探测器的探测效率也随之变化, 导致对样品不同位置需分别进行效率刻度。本工作用均匀聚乙烯样品填充废物桶, 采用SGS 装置的测量方法估计放射核素活度。将放射性点源置于桶内, 按距离桶的中心距离依均匀分布规律选取7个点, 分别对其进行效率刻度。并建立SGS 测量系统几何模型, 通过两种方法将1~7号位置的几何因子对探测效率计算结果进行加权平均,后给出每层的探测效率标准值, 此标准值可充分估计每层不同位置对核素的探测效率。结果表明: 在测量和计算误差存在的条件下, 可以快速准确估计出放射性废物桶内不同位置的核素放射性活度, 提高检测精度。

The segmented gamma-scanning (SGS) measurement is a non-destructive analysis technology. It is an important method of qualitative and quantitative analyse for nuclear waste drums. However, the HPGe detector’s detection efficiency is related with the location of the radionuclide in the actual measuring process, so it is necessary to do efficiency calibration for different locations. This paper presents the study based on SGS measurement method. The waste drum was filled with uniform polyethylene samples. The radionuclides were approximated as point sources. Seven points were selected in each of the three uniform segments of the drum for efficiency calibration. Shell-source method and geometrical factor method were used to calculate the weighted detection efficiency for calibration of each point. The results show that this method can estimate the nuclide activity at different positions in the drum quickly and accurately with acceptable errors.