Anomalously high 234U/238U activity ratios of Tatsunokuchi hot spring waters, Ishikawa Prefecture, Japan |
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| Authors: | M Yamamoto T Sato K Sasaki K Hama T Nakamura K Komura |
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| Institution: | (1) Low Level Radioactivity Laboratory, Kanazawa University, Tatsunokuchi, Ishikawa, 923-1224, Japan;(2) Department of Applied Chemistry, Faculty of Engineering, Kanagawa University Division of Global Environmental Science and Engineering, Graduate School of Natural Science and Technology, Rokkakubashi, Kanagawa-ku, Yokohama, 221-8686, Japan;(3) Department of Cultural Properties and Heritage, Kanazawa Gakuin University, Sue-machi, Kanazawa, Ishikawa, 920-1392, Japan;(4) Tono Geoscience Center, Japan Nuclear Cycle Development Institute, Jyorinji, Izumi-cho, Tokai, Gifu, 509-5102, Japan;(5) Center for Chronological Research, Nagoya University, Chikusa, Nagoya, 464-8602, Japan |
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| Abstract: | Uranium concentration and the 234U/238U activity ratio have been measured for the Tatsunokuchi hot spring waters of Ishikawa Prefecture in Japan, collected periodically over a long period (1977-2000). The concentration of 238U varied drastically between 0.045 and 1.02 mBq/l (a factor of about 20), while the 234U concentration was almost unchanged, ranging from 2.30 to 3.07 mBq/l. Resultant 234U/238U activity ratios showed a wide range from 2.7 to 51. Equilibrium calculation by using the geochemical code showed that U for one end-member representing low uranium contents and very high 234U/238U ratios was expected to exist as UO2(CO3)2
2-. By using the U isotopic and 14C dating methods, the age of this water was roughly estimated to be in the range of 104-105 years. |
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