Differences of natural radioactivity and radon emanation fraction among constituent minerals of rock or soil |
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| Authors: | Akihiro Sakoda Yuichi Nishiyama Katsumi Hanamoto Yuu Ishimori Yuki Yamamoto Takahiro Kataoka Atsushi Kawabe Kiyonori Yamaoka |
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| Institution: | 1. Graduate School of Health Sciences, Okayama University, 5-1 Shikata-cho, 2-chome, Kita-ku, Okayama 700-8558, Japan;2. Ningyo-toge Environmental Engineering Center, Japan Atomic Energy Agency, 1550 Kamisaibara, Kagamino-cho, Tomata-gun, Okayama 708-0698, Japan;1. CEMUC, Department of Geology, University of Trás-os-Montes e Alto Douro, Quinta de Prados, 5000-801 Vila Real, Portugal;2. CEMUC, Department of Earth Sciences, University of Coimbra, 3000-272 Coimbra, Portugal;1. Radiation and Nuclear Safety Authority (STUK), 00881 Helsinki, Finland;2. Laboratory of Radiochemistry, University of Helsinki, 00014 Helsingin Yliopisto, Finland;3. Geological Survey of Finland, 02151 Espoo, Finland;4. IC2MP, HYDRASA, University of Poitiers, 86022 Poitiers, France;1. Radiological Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu, India;2. Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Mumbai 400085, India;3. Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India;1. Nuclear Technique Laboratory, University of Science, VNU-HCM, Linh Trung Campus Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Viet Nam;2. Department of Nuclear Physics and Nuclear Engineering, Faculty of Physics and Engineering Physics, University of Science, VNU-HCM, 227 Nguyen Van Cu Street, District 5, Ho Chi Minh City, Viet Nam;3. Department of Analytical Chemistry, Faculty of Chemistry, University of Science, VNU-HCM, 227 Nguyen Van Cu Street, District 5, Ho Chi Minh City, Viet Nam;1. British Geological Survey, Keyworth, Nottingham NG12 5GG, UK;2. Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton, Didcot, Oxon OX11 0RQ, UK;3. Geological Survey of Northern Ireland, Department of Enterprise, Trade and Investment, Colby House, Stranmillis Court, Stranmillis Road, Belfast BT9 5BF, Northern Ireland, UK |
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| Abstract: | We examined differences in the radioactive characteristics among the main minerals forming granite materials. Using a non-toxic high-density agent, minerals were separated from rock (granite–gneiss) and soil (weathered granite) samples. The natural radioactivity (238U and 226Ra) and radon emanation fraction of the minerals were then studied by gamma-ray spectrometry. The radon emanation fractions (27–43%) of the minerals from the soil were much higher than those (0.6–4.6%) of the rock minerals. Additionally, the emanation fractions differed greatly among the minerals separated from both the bulk rock and soil. These results were discussed in terms of the differences of surface area and radium distribution in the mineral grains. It was noticeable that a higher emanation fraction than expected for quartz was commonly observed in the rock and soil samples. We then estimated the contribution of each constituent mineral to the total radon exhalation from the bulk samples. The result depended not only on the radon emanation fraction, but also on the 226Ra activity and the mineral content. Furthermore, using the obtained data, we also discussed the effect of grain size on radon emanation and why this has been reported to vary markedly in previous studies. |
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