基于能谱拖尾及探测效率测试的最优α放射性气溶胶取样滤膜选择研究  

Optimal selection of sampling filter membranes for alpha radioactive aerosols based on spectrum tailing and detection efficiency tests

作　　者：张俊新 谷懿[1] 万前银 刘秋实 林文钊 ZHANG Junxin;GU Yi;WAN Qianyin;LIU Qiushi;LIN Wenzhao(College of Nuclear Technology and Automation Engineering,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]成都理工大学核技术与自动化工程学院,成都610059

出　　处：《核技术》2021年第10期30-36,共7页Nuclear Techniques

基　　金：国家重点研发计划课题(No.2017YFC0602105);基础性军工科研院所稳定支持经费科研任务(No.A132007W06);国家自然科学基金(No.41774190)资助。

摘　　要：取样滤膜是放射性气溶胶连续监测系统中的重要组成部分,其过滤性能会直接影响系统的探测效率;此外,α能谱拖尾会增大核素识别难度,降低气溶胶核素的测量精度和升高最小可探测活度。针对现在最常用的混合纤维素(Mixed Cellulose Ester Membrane,MCEM)滤膜、疏水性聚四氟乙烯(Polytetrafluoroethylene,PTFE)滤膜和聚丙烯(Polypropylene,PP)滤膜,以探测效率和α能谱拖尾为指标,开展了不同浓度和多种孔径下滤膜吸附性能实验,完成了在不同滤膜孔径、氡浓度下滤膜吸附性能的综合评价。结果表明:在天然放射性气溶胶测量时,选用MCEM滤膜作为取样滤膜时探测效率最高,选用疏水性PTFE滤膜作为取样滤膜对α能谱测量拖尾影响最小。不同氡浓度下,同种滤膜(MCEM滤膜和疏水性PTFE滤膜)孔径选用和天然放射性气溶胶最大值粒径接近的0.45μm时探测效率最高,滤膜孔径大小对α能谱拖尾的影响不明显。另外,同种滤膜相同孔径下,探测效率随着气溶胶浓度的升高而降低。本研究为不同条件下天然放射性气溶胶监测中取样滤膜的最优选取提供参考。[Background]Sampling filter membrane is an important part of the continuous monitoring system for radioactive aerosols.The performance of the sampling filter membrane directly affects detection efficiency of the system.In addition,tailing effect in α spectra increases the difficulty of identifying nuclides,reduces the accuracy of aerosol measurement,and elevates the minimum detectable activity.[Purpose]This study aims to find a sampling filter membrane with high detection efficiency,small α spectrum tailing and the pore size suitable for actual environmental measurement.[Methods]The detection efficiency and spectrum tailing performance of the three most commonly used filter membranes at present,i.e.,mixed cellulose ester membrane(MCEM),hydrophobic polytetrafluoroethylene(PTFE)and polypropylene(PP)filter membranes,were tested under different radon concentrations and various pore sizes.Then,based on obtained data of the tests,the comprehensive evaluation was performed on their adsorption performances to determine the optimal sampling filter membrane.[Results]The results show that the MCEM filter membrane has the highest detection efficiency and the hydrophobic PTFE filter membrane has the least tailing effect in the three kinds of filter membranes.In comparison of other pore sizes under different radon concentrations,the MCEM filter membrane or hydrophobic PTFE filter membrane has the highest detection efficiency when its pore size is 0.45μm,which is close to the maximum particle size of natural radioactive aerosols.No obvious effect of the pore size of the filter membrane is observed on theαspectrum tailing.In addition,for one filter membrane with the same pore size,the detection efficiency decreases with the increase of aerosol concentration and vice versa.[Conclusions]This study provides a useful reference for the optimal selection of filter membranes for natural radioactive aerosols under various conditions.

关 键 词：放射性气溶胶 α 能谱拖尾 滤膜 探测效率 

分 类 号：TL99[核科学技术—核技术及应用]