辐射防护 ›› 2022, Vol. 42 ›› Issue (6): 556-562.

• 辐射防护监测 • 上一篇    下一篇

高纯锗能谱仪125I核素点源和体源绝对活度测量方法研究

张磊   

  1. 上海市辐射环境安全技术中心,上海 200065
  • 收稿日期:2022-03-16 出版日期:2022-11-20 发布日期:2023-01-05
  • 作者简介:张磊(1985—),男,2006年毕业于兰州大学核物理专业,获学士学位,2011年毕业于复旦大学粒子物理与原子核物理专业,获博士学位。E-mail: zhangla02@163.com
  • 基金资助:
    上海市生态环境局青年科研项目(No.2021-013)。

Study on the absolute activity measurement method of 125I nuclide point source and volume source by HPGe spectrometer

ZHANG Lei   

  1. Shanghai Technology Center of Radiation Environment Safety,Shanghai 200065
  • Received:2022-03-16 Online:2022-11-20 Published:2023-01-05

摘要: 通过125I核素X射线和γ射线的符合相加特性,推导出了仅包含全能峰(27.3、35.5、31.2 keV)净计数率、符合峰(58.5、66.7 keV)净计数率和总谱净计数率的125I活度计算公式,并通过宽能型和N型高纯锗谱仪分别对点源、活性炭盒源和液体源进行了验证。点源到探测器距离不大于5 cm测量时,绝对活度公式计算结果和参考值的相对偏差在±1.2%以内;活性炭盒对125I核素的自吸收效应可以忽略,绝对活度计算公式不受 125I核素分布形式的影响,活性炭盒源正反面测量的相对偏差均在±1.4%以内;体积小于40 mL液体源的测量结果和参考值的相对偏差在±2.6%以内,液体源在测量时,样品高度不宜过高,以减少自吸收效应对符合相加峰的减弱效果。实验结果表明在不依赖标准物质和核素参数的情况下,推导的绝对活度计算公式可用于125I核素放射性活度的精确测量。

关键词: 125I核素, 符合相加, 绝对活度, 高纯锗能谱仪

Abstract: This paper derived the 125I activity calculation formula based on the coincidence summing characteristics of 125I nuclide X-ray and γ ray. The formula only included the net counting rate of the full-energy peaks (27.3, 35.5, 31.2 keV), the net counting rate of the sum-peaks (58.5, 66.7 keV) and the net counting rate of the total spectrum. The point source, activated carbon cartridge source and liquid source were verified by Broad-energy and N-type germanium spectrometer. When the distance from point source to detector was less than 5cm, the relative deviation between the calculated results of the absolute activity and the reference values was within ±1.2%. The self-absorption effect of 125I nuclide in activated carbon cartridge could be ignored, and the absolute activity calculation formula was not affected by the distribution form of 125I nuclide. The relative deviation of front and rear measurements for activated carbon cartridge source was within ±1.4%. The relative deviation between the measurement results and reference values of liquid source with volume less than 40mL was within ±2.6%. The sample height should not be too high during the measurement of liquid source, so as to reduce the weakening effect of self-absorption on sum-peaks. The experimental results show that the absolute activity calculation formula derived in this paper can be used to accurately measure the activity of 125I nuclide without relying on standard substances and nuclide parameters.

Key words: 125I nuclide, coincidence summing, absolute activity, HPGe spectrometer

中图分类号: 

  • X830.2