2005 Fiscal Year Final Research Report Summary
Development of determination system for radon concentration using air luminescence
| Project/Area Number |
16510044
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Risk sciences of radiation/Chemicals
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| Research Institution | Kyoritsu University of Pharmacy |
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Principal Investigator |
MORITA Yuko Kyoritsu University of Pharmacy, Pharmaceutical Chemistry, Assistant Professor, 薬学部, 講師 (80245448)
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| Co-Investigator(Kenkyū-buntansha) |
MURAKAMI Isao Kyoritsu University of Pharmacy, Pharmaceutical Chemistry, Instructor, 薬学部, 助手 (50286407)
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| Project Period (FY) |
2004 – 2005
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| Keywords | air luminescence / radon / nitrogen |
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| Research Abstract |
Air luminescence method has been applied for the determination of ^<222>Rn and the daughter nuclides. In order to improve light collection, the two photo-multiplier tubes (PMTs) were enclosed in a light-tight chamber and covered with reflectors. The pulses from the PMTs were fed into an amplifier, a coincidence circuit, a 1024-channel pulse height analyzer. Discrimination between noise pulses and pulses from real luminescence events was satisfactory.
The counting efficiency of this system using a standard alpha-emitting nuclide (^<241>Am) and known amounts of ^<222>Rn was found to be 2.4 and 7.38%, respectively. This difference in counting efficiencies may be attributed to the fact that ^<222>Rn is accompanied by two short-lived alpha-emitting daughter nuclides (^<218>Po, ^<214>Po).
Luminescence observed in this study is attributed to the ionization and excitation of nitrogen and oxygen caused by the passage of alpha-particles in air. Therefore, the counting efficiency for nitrogen luminescence and oxygen luminescence was also measured using a liquid scintillation system and found to be 60.2 and 28.2%, respectively.
Based on the relatively high counting efficiency of nitrogen luminescence, an effective method for sampling environmental ^<222>Rn in air was developed : After removal of CO_2 and O_2 from air, ^<222>Rn and nitrogen gas in air was cooled to ca.-195.82℃ using an apparatus for liquefaction of nitrogen gas. Thus, concentrated environmental ^<222>Rn was collected together with nitrogen and easily measured by this method.
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