放射性惰性气体实时测量装置的设计与模拟研究
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摘要
核反应堆在运行过程中或核应急情况下会产生~(85)Kr、~(133)Xe、~(135)Xe和~(41)Ar等放射性惰性气体,准确测量不同惰性气体的放射性活度对了解反应堆的运行状况和核应急预警均有重要意义。根据各种核素衰变发射的β、γ射线,设计并优化了可用于放射性惰性气体活度实时测量的4π双叠层闪烁体探测器。探测器的内层塑料闪烁体用于测量β射线,外层碘化铯闪烁体(CsI)用于测量γ射线,并通过β-γ的符合测量实现不同放射性核素的分辨及活度测量。针对核电放出的4种主要放射性惰性气体,基于GEANT4(GEometry ANd Tracking 4)模拟库包,研究了塑料闪烁体、CsI厚度及气体采样腔尺寸对不同核素发射的β、γ探测效率的影响;并给出该4π型双叠层闪烁体探测器的优化几何尺寸和相应探测器性能,为后续探测器的制作与测试提供参考。
[Background] In normal operation or emergency, nuclear reactor can produce radioactive noble gases,the main components are85 Kr,133 Xe,135 Xe and41 Ar. It is of great significance to monitor the radioactivity of these mixed noble gases accurately for the operation of nuclear power plant. [Purpose] This study aims to develop a 4πphoswich scintillator detector to measure the radioactivity of noble gases in online model. [Methods] The 4πphoswich scintillator detector consists of a sampling chamber, an inner plastic scintillator chamber for βmeasurement, and a CsI scintillator chamber for γ measurement. The pulse shaping discrimination(PSD) method is developed to distinguish the events between β, γ and β-γ coincidence events. Based on GEANT4 simulation toolkit,the performance of the detector, including the detection efficiency is investigated. [Results] The simulation results show that both 0.3 mm plastic scintillator layer and a 20 mm CsI layer are necessary for measuring the radioactivity of noble gases. The size of sampling chamber should not be larger than ?50 mm×50 mm. Under these conditions, the detection efficiency for the above nuclides can be up to 90%. [Conclusions] According to the simulation results, a composed 2-layer scintillation detector is designed, and its detection and recognition capability for different inert gases is studied. The comparison of these characteristics with actual calibration is the crucial step for this device.
[Background] In normal operation or emergency, nuclear reactor can produce radioactive noble gases,the main components are85 Kr,133 Xe,135 Xe and41 Ar. It is of great significance to monitor the radioactivity of these mixed noble gases accurately for the operation of nuclear power plant. [Purpose] This study aims to develop a 4πphoswich scintillator detector to measure the radioactivity of noble gases in online model. [Methods] The 4πphoswich scintillator detector consists of a sampling chamber, an inner plastic scintillator chamber for βmeasurement, and a CsI scintillator chamber for γ measurement. The pulse shaping discrimination(PSD) method is developed to distinguish the events between β, γ and β-γ coincidence events. Based on GEANT4 simulation toolkit,the performance of the detector, including the detection efficiency is investigated. [Results] The simulation results show that both 0.3 mm plastic scintillator layer and a 20 mm CsI layer are necessary for measuring the radioactivity of noble gases. The size of sampling chamber should not be larger than ?50 mm×50 mm. Under these conditions, the detection efficiency for the above nuclides can be up to 90%. [Conclusions] According to the simulation results, a composed 2-layer scintillation detector is designed, and its detection and recognition capability for different inert gases is studied. The comparison of these characteristics with actual calibration is the crucial step for this device.
引文
1袁之伦,李宏宇,唐丽丽,等.我国核电厂气态流出物中惰性气体监测现状[J].同位素,2013,26(4):244-248.DOI:10.7538/tws.2013.26.04.0244.YUAN Zhilun,LI Hongyu,TANG Lili,et al.Study on monitoring capacity of noble gas for nuclear power plant effluent[J].Journal of Isotopes,2013,26(4):244-248.DOI:10.7538/tws.2013.26.04.0244.
2 Schell W R,Tobin M J,Marsan D J,et al.Measurement of fission product gases in the atmosphere[J].Nuclear Instruments and Methods in Physics Research A,1997,385(2):277-284.DOI:10.1016/S0168-9002(96)00787-5.
3张利兴.禁核试核查中放射性惰性气体的监测[J].核技术,2004,27(10):770-777.ZHANG Lixing.Radioactive noble gases monitoring for the verification of the Comprehensive Nuclear Test-Ban Treaty[J].Nuclear Techniques,2004,27(10):770-777.
4王世联,王军,李奇,等.HPGeγ能谱法测量惰性气体氙活度[J].核电子学与探测技术,2009,29(3):521-524.DOI:10.3969/j.issn.0258-0934.2009.03.008.WANG Shilian,WANG Jun,LI Qi,et al.HPGeγspectrum method for activity measurement of xenon gas[J].Nuclear Electronics&Detection Technology,2009,29(3):521-524.DOI:10.3969/j.issn.0258-0934.2009.03.008.
5 Ringbom A,Larson T,Axelsson A,et al.SAUNA-a system for automatic sampling,processing,and analysis of radioactive xenon[J].Nuclear Instruments and Methods in Physics Research A,2003,508(3):542-553.DOI:10.1016/S0168-9002(03)01657-7.
6 Zhang W,Mekarski P,Lam J,et al.Geant4 Monte Carlo radioxenon beta-gamma coincidence efficiency simulation for a phoswich detector[J].Journal of Radioanalytical and Nuclear Chemistry,2010,285(3):475-482.DOI:10.1007/s10967-010-0596-3.
7 Ely J H,Aalseth C E,Mcintyre J I.Novel beta-gamma coincidence measurements using phoswich detectors[J].Journal of Radioanalytical and Nuclear Chemistry,2005,263(1):245-250.DOI:10.1007/s10967-005-0044-y.
8 Knoll G F.Radiation detection and measurement[M].4th Ed.New York:Wiley,2010:142-149.
9 Petit G Le,Cagniant A,Gross P,et al.SpalaxTMnew generation:a sensitive and selective noble gas system for nuclear explosion monitoring[J].Applied Radiation and Isotopes,2015,103(2):102-144.DOI:10.1016/j.apradiso.2015.05.019.
10刘运祚.常用放射性核素衰变纲图[M].北京:原子能出版社,1982.LIU Yunzuo.Decay scheme of commonly used radionuclides[M].Beijing:Atomic Energy Press,1982.
11 Farsoni A T,Hamby D M.A system for simultaneous beta and gamma spectroscopy[J].Nuclear Instruments and Methods in Physics Research A,2007,578(3):528-536.DOI:10.1016/j.nima.2007.06.020.
12 Mekarski P,Zhang W,Ungar K,et al.Monte Carlo simulation of a PhosWatch detector using Geant4 for xenon isotope beta-gamma coincidence spectrum profile and detection efficiency calculations[J].Applied Radiation and Isotopes,2009,67(10):1957-1963.DOI:10.1016/j.apradiso.2009.07.005.
13 Agostinelli S,Allison J,Amako K,et al.GEANT4-a simulation toolkit[J].Nuclear Instruments and Methods in Physics Research Section A,2003,506(3):250-303.DOI:10.1016/S0168-9002(03)01368-8.
14 Becker R,Wittich K P,Koslowsky D.ROOT-an object oriented data analysis framework[J].Nuclear Instruments and Methods in Physics Research A,1997,389(1-2):81-86.DOI:10.1016/S0168-9002(97)00048-X.
15卢希庭.原子核物理[M].北京:原子能出版社,2000:140-142.LU Xiting.Nuclear physics[M].Beijing:Atomic Energy Press,2000:140-142.
2 Schell W R,Tobin M J,Marsan D J,et al.Measurement of fission product gases in the atmosphere[J].Nuclear Instruments and Methods in Physics Research A,1997,385(2):277-284.DOI:10.1016/S0168-9002(96)00787-5.
3张利兴.禁核试核查中放射性惰性气体的监测[J].核技术,2004,27(10):770-777.ZHANG Lixing.Radioactive noble gases monitoring for the verification of the Comprehensive Nuclear Test-Ban Treaty[J].Nuclear Techniques,2004,27(10):770-777.
4王世联,王军,李奇,等.HPGeγ能谱法测量惰性气体氙活度[J].核电子学与探测技术,2009,29(3):521-524.DOI:10.3969/j.issn.0258-0934.2009.03.008.WANG Shilian,WANG Jun,LI Qi,et al.HPGeγspectrum method for activity measurement of xenon gas[J].Nuclear Electronics&Detection Technology,2009,29(3):521-524.DOI:10.3969/j.issn.0258-0934.2009.03.008.
5 Ringbom A,Larson T,Axelsson A,et al.SAUNA-a system for automatic sampling,processing,and analysis of radioactive xenon[J].Nuclear Instruments and Methods in Physics Research A,2003,508(3):542-553.DOI:10.1016/S0168-9002(03)01657-7.
6 Zhang W,Mekarski P,Lam J,et al.Geant4 Monte Carlo radioxenon beta-gamma coincidence efficiency simulation for a phoswich detector[J].Journal of Radioanalytical and Nuclear Chemistry,2010,285(3):475-482.DOI:10.1007/s10967-010-0596-3.
7 Ely J H,Aalseth C E,Mcintyre J I.Novel beta-gamma coincidence measurements using phoswich detectors[J].Journal of Radioanalytical and Nuclear Chemistry,2005,263(1):245-250.DOI:10.1007/s10967-005-0044-y.
8 Knoll G F.Radiation detection and measurement[M].4th Ed.New York:Wiley,2010:142-149.
9 Petit G Le,Cagniant A,Gross P,et al.SpalaxTMnew generation:a sensitive and selective noble gas system for nuclear explosion monitoring[J].Applied Radiation and Isotopes,2015,103(2):102-144.DOI:10.1016/j.apradiso.2015.05.019.
10刘运祚.常用放射性核素衰变纲图[M].北京:原子能出版社,1982.LIU Yunzuo.Decay scheme of commonly used radionuclides[M].Beijing:Atomic Energy Press,1982.
11 Farsoni A T,Hamby D M.A system for simultaneous beta and gamma spectroscopy[J].Nuclear Instruments and Methods in Physics Research A,2007,578(3):528-536.DOI:10.1016/j.nima.2007.06.020.
12 Mekarski P,Zhang W,Ungar K,et al.Monte Carlo simulation of a PhosWatch detector using Geant4 for xenon isotope beta-gamma coincidence spectrum profile and detection efficiency calculations[J].Applied Radiation and Isotopes,2009,67(10):1957-1963.DOI:10.1016/j.apradiso.2009.07.005.
13 Agostinelli S,Allison J,Amako K,et al.GEANT4-a simulation toolkit[J].Nuclear Instruments and Methods in Physics Research Section A,2003,506(3):250-303.DOI:10.1016/S0168-9002(03)01368-8.
14 Becker R,Wittich K P,Koslowsky D.ROOT-an object oriented data analysis framework[J].Nuclear Instruments and Methods in Physics Research A,1997,389(1-2):81-86.DOI:10.1016/S0168-9002(97)00048-X.
15卢希庭.原子核物理[M].北京:原子能出版社,2000:140-142.LU Xiting.Nuclear physics[M].Beijing:Atomic Energy Press,2000:140-142.