低浓度85Kr的内充气叠层反符合探测技术研究

85Kr是半衰期最长的放射性惰性气体裂变产物，在防止核材料扩散、监测核电站气体流出物水平等领域有重要应用。对于空气本底级低浓度85Kr测量，以液闪谱仪（LSC）、内充气正比技术管（IGPC）为代表的β计数法被长期采用，然而这些方法对分离制样流程要求较高，一定程度限制了大范围推广。本课题提出了基于内充气叠层反符合探测器测量低浓度85Kr的新想法，并详细论述了叠层探测器结构设计与优化、脉冲信号读出与甄别、85Kr探测性能标定实验等关键技术及解决方案。通过本研究拟建立一种闪烁体测量低浓度85Kr的新技术，既充分发挥闪烁体探测器对样品杂质成分变化不敏感的优势，又解决了传统构型探测效率低、本底高的问题，有望显著降低环境中85Kr监测的实施难度。

Krypton-85 is a radioactive fissiogenic noble gas with the longest half-life of 10.76 years, which play an important role in the preventing of weapon grade plutonium diffusion and the monitoring of gas effluent in nuclear power plants. Liquid scintillation spectrometer (LSC) and internal gas proportional technology tube (IGPC) has been used for a long time to measure low-level 85Kr in air sample. However, the requirements of these methods to the front-end separation and sample preparation process are very stringent, which limits the application in some fields. In this project, we proposed a new method for low concentration 85Kr measurement with the development of an internal gas phoswich detector, and discussed the solutions of the detector structure optimization, the pulse shape analysis and the calibration experiment in this application. It is expected to establish a new low-level 85Kr measurement method with scintillator detector in this study, which not only take the advantage of insensitive to the stable impurities, but also solve the problems of low efficiency and high background of traditional internal gas scintillator detector. Therefore, the difficulty to monitor low-level 85Kr in environmental samples can be significantly reduced.