TERRAPUB Geochemical Journal

Geochemical Journal, Vol. 51 (No. 5), pp. 449-455, 2017

Tritium and iodine-129 concentrations in precipitation at Tsukuba, Japan, after the Fukushima Daiichi Nuclear Power Plant accident

Teruyuki Maruoka,1* Takamasa Kawamuto,2 Takeshi Ohno,2 Yasuyuki Muramatsu,2 Hiroyuki Matsuzaki,3 Takuya Matsumoto4 and Pradeep Aggarwal4

1Faculty of Life and Environmental Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan
2Department of Chemistry, Faculty of Science, Gakushuin University, Mejiro 1-5-1, Toshima-ku, Tokyo 171-8588, Japan
3Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, Yayoi 2-11-16, Bunkyo-ku, Tokyo 113-0032, Japan
4Isotope Hydrology Section, International Atomic Energy Agency, Vienna, International Centre, PO Box 100, 1400 Vienna, Austria

(Received November 11, 2015; Accepted April 21, 2016)

Abstract: The earthquake off the Pacific coast of Japan and the subsequent tsunami on March 11, 2011, triggered a series of accidents in the Fukushima Daiichi Nuclear Power Plant (FNPP1). The accidents caused the release of a mixture of radioactive substances into the environment. This study measured the concentration of tritium (3H) and iodine-129 (129I) in rainwater samples collected at Tsukuba, 170 km southwest of the plant, during the year following the accident. High 3H concentrations were observed in the rainwater samples collected within one month after the FNPP1 accident. 3H concentrations decreased steadily over time and returned to the levels before the accident. Concentrations of 129I also decreased over time. However, pulses of high 129I concentrations were observed at several other times following the accident. The 129I concentrations were found to be correlated with iron concentrations in rainwater. It is likely that iron oxide, which can absorb iodate ions (IO3-), was the carrier of radiogenic iodine. This study concludes that 129I and also 131I, which is one of the most harmful radionuclides produced in nuclear reactors, can be redistributed to the atmosphere in the months following the deposition of radiogenic iodine on the ground.
Key words: Fukushima Daiichi Nuclear Power Plant accident, volatile radionuclides, tritium, radioactive iodine, accelerator mass spectrometry

*Corresponding author E-mail: maruoka.teruyuki.fu@u.tsukuba.ac.jp

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