摘要
作为放射性惰性气体,^(85)Kr是大气环境监测和禁核试核查中重点关注的核素。利用内充气正比计数管直接测量是目前^(85)Kr的主流测量方法之一,而基于内充气正比计数管的反符合测量方法研究多集中在37Ar的测量中,鲜有关于^(85)Kr的报道。本文建立了一套低本底内充气正比计数管测量系统用于^(85)Kr的高灵敏度测量,采用准4π阱型塑料闪烁体作为反符合探测器,以主动屏蔽来自宇宙射线的本底,相比原始能谱,反符合能谱的全谱本底计数率由3.64 s^(−1)降低至0.182 s^(−1)。利用长度补偿法绝对测量了^(85)Kr的活度浓度,并标定了系统的探测效率,结果为95.8%。测量24 h情况下系统的最小可探测活度约7 mBq,有效提高了^(85)Kr的测量灵敏度。
^(85)Kr is a noble gas radioactive nuclide with a half-life of 10.75 years,and it decays by emission of beta rays associated with weak gamma rays.Most of the^(85)Kr released into the atmosphere is artificially produced by neutron induced fission reactions,and it plays an important role in atmospheric environmental monitoring,detection of clandestine production of fissile materials,and verification of atmospheric transport model.Low-level detection of^(85)Kr is therefore required.Internal gas proportional counter(IGPC)is one of the primary techniques to measure^(85)Kr.However,studies about anti-coincidence measurement based on IGPC mostly focused on the measurement of 37Ar,and few studies about^(85)Kr were reported.In this paper,an anti-cosmic ray IGPC system was established to improve the detection sensitivity of^(85)Kr.A quasi-4πwell-type plastic scintillator surrounding the inner IGPC was used as an anti-coincidence detector to actively shield the background arising from cosmic rays.Compared with the non-anticoincidence spectrum,the background count rate of the anticoincidence spectrum decreases from 3.64 s^(−1) to 0.182 s^(−1).The activity concentration of^(85)Kr was measured using length compensation method,and the detection efficiency of the system was calibrated to be 95.8%.The minimum detectable activity of^(85)Kr of about 7 mBq was achieved within 24 hours,which effectively improves the measurement sensitivity of^(85)Kr.
作者
梁建峰
解峰
代义华
师全林
王春杰
李雪松
关清帝
姜文刚
余功硕
刘志超
LIANG Jianfeng;XIE Feng;DAI Yihua;SHI Quanlin;WANG Chunjie;LI Xuesong;GUAN Qingdi;JIANG Wengang;YU Gongshuo;LIU Zhichao(Northwest Institute of Nuclear Technology,Xi’an 710024,China)
出处
《原子能科学技术》
北大核心
2025年第5期1120-1125,共6页
Atomic Energy Science and Technology
作者简介
通信作者:解峰。
