Study of radon emanation with a focus on internal properties

Research Project

Project/Area Number	18K05209
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Review Section	Basic Section 34030:Green sustainable chemistry and environmental chemistry-related
Research Institution	Japan Atomic Energy Agency
Principal Investigator	Sakoda Akihiro 国立研究開発法人日本原子力研究開発機構, 核燃料・バックエンド研究開発部門人形峠環境技術センター, 研究職 (50603221)
Project Period (FY)	2018-04-01 – 2021-03-31
Project Status	Completed (Fiscal Year 2020)
Budget Amount *help	¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000) Fiscal Year 2020: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000) Fiscal Year 2019: ¥520,000 (Direct Cost: ¥400,000、Indirect Cost: ¥120,000) Fiscal Year 2018: ¥3,120,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥720,000)
Keywords	ラドン / トロン / 散逸 / 鉱物
Outline of Final Research Achievements	Radon (Rn-222) and thoron (Rn-220) are natural radioactive inert gases, originating from radium in solids such as minerals. Since they exist everywhere, various research efforts have been made from the viewpoint of health effects and tracer use. To better understand radon and thoron emanation phenomenon, which is the first process of their environmental dynamics, the present study discussed it experimentally and numerically in light of the effects of properties of mineral particles. The heating treatment of powdered mineral samples (400 to 800°C for 6 hours) suppressed the emanation power of both radon and thoron due to the annealing effect. The model calculation also found that the contribution of solid diffusion to the emanation was much smaller than that of alpha recoil.
Academic Significance and Societal Importance of the Research Achievements	ラドン・トロン散逸の理解の深化によって、環境動態の最初のプロセスである「発生」の特徴が明らかになり、環境影響評価の向上による放射線防護分野への貢献が考えられる。また、ラドンを境界とした鉱物中の放射非平衡の理解にも貢献し、年代測定の精度向上など地球科学分野への貢献も考えられる。