基于α能谱法的钍射气子体水平连续测量方法研究及应用

Thoron and radon are all natural radioactivity inert gases, but mainly the danger for human comes from their decay progeny. Environmental thoron / radon and its daughters are almost in everywhere, but because people do not pay enough attention to thoron and its progeny induced hazards, coupled with shorter half-life of thoron, and longer half-life of its progeny,it is not easy to establish different measurement methods to meet diverse needs. In fact,since there are some situations such as thorium-based nuclear fuel production processes, rare earth production processes, as well as environmental monitoring and evaluation and so on, the continuous measurement method of thoron progeny is needed, so it is necessary to research a new method that is suitable for measuring the concentration of thoron progeny continuously and reliably.This project plans to introduce a cumulative activity function to eliminate effects caused by accumulation of thoron progeny on the filter surface,these progeny came from previous sampling.Based on the alpha spectroscopy ,then a new method which measures the concentration of thoron progeny continuously is established,and lasts about a week not need to replace the filter,and its reliability is tested.The new method will be applied to measure the concentration of radon daughters continuously,and research the law of thoron/radon daughters variation in typical places. Certainly,the project can provide a theoretical basis and technical means for these fields, such as the monitoring and dosimetry evaluation of radon/thoron and their daughters, radon/thoron tracer applications and radiation protection for special environments with high radon/thoron concentrations. In conclusion, this study has important scientific significance and application value.

钍射气同氡一样是天然产生的放射性惰性气体，而对人体的危害主要来自于它们的衰变子体。环境中钍射气/氡及其子体几乎无处不在，但由于人们对钍射气及其子体所致危害认识不足，加之钍射气半衰期较短，其子体半衰期又较长，不易建立起象氡及其子体那样满足各种需要的测量方法。我国核能钍基燃料生产、稀土生产和环境监测评价等都需要进行钍射气子体连续可靠的测量，所以有必要研究环境中钍射气子体的连续测量方法。本项目拟引入累积活度函数消除滤膜上累积的钍射气子体对当次测量影响，基于α能谱法建立在不更换滤膜的条件下一周左右的连续测量钍射气子体的方法并进行可靠性检验，同时将方法应用于氡子体连续测量和典型场所钍射气/氡子体变化规律研究。研究方便、实用、可靠的钍射气/氡子体连续测量方法，可为研制钍射气/氡子体连续测量仪提供理论基础，进而为提高环境钍射气/氡污染调查与危害评价的水平提供技术支撑，具有重要的科学意义与应用价值。

钍射气同氡一样是天然产生的放射性惰性气体，而对人体的危害主要来自于它们的衰变子体。环境中钍射气/氡及其子体几乎无处不在，但由于人们对钍射气及其子体所致危害认识不足，加之钍射气半衰期较短，其子体半衰期又较长，不易建立起象氡及其子体那样满足各种需要的测量方法。我国核能钍基燃料生产、稀土生产和环境监测评价等都需要进行钍射气子体连续可靠的测量，所以有必要研究环境中钍射气子体的连续测量方法。主要研究内容包括：（1）引入子体的累积活度函数，根据描述222Rn/220Rn子体富集、衰变过程的贝特曼衰变方程。建立了基于α能谱方法的222Rn/220Rn子体连续测量方法（一张滤膜工作7天左右）；（2）在解决关键技术问题的基础上，完成了仪器总体设计、机械设计加工、电路测控系统研制、软件设计与编译、仪器各项性能测试与探测效率刻度六项工作。研制了222Rn/220Rn子体连续测量仪；（3）开展了纯222Rn子体与室内两种测量环境连续测量仪的初步应用研究。连续测量仪在两种测量环境下的应用测试结果符合222Rn室内222Rn子体以及室内222Rn/220Rn子体的分布特征与变化规律。检验了连续测量仪的长期工作的稳定性与可靠性，达到了预期效果。.总之，本文建立的220Rn子体连续测量方法在80-3000Bq/m3测量环境中的准确度与可靠性较好，当220Rn子体水平低至100 Bq/m3左右时，方法的不确定度控制在5%以内，并能消除基于迭代扣除算法方法误差。在解决影响方法测量准确度与可靠性的关键技术问题的基础上研制的222Rn/220Rn子体连续测量仪不需抽真空、结构简单、操作维护方便、不需频繁更换滤膜。完全满足在稀土生产场所及高钍本底地区等环境与场所222Rn/220Rn子体水平的连续监测的要求。

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