Japan Geoscience Union Meeting 2014

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Symbol M (Multidisciplinary and Interdisciplinary) » M-AG Applied Geosciences

[M-AG38_2AM2] Dynamics of radionuclides emitted from Fukuchima Dai-ichi Nuclear Power Plant in the environment

Fri. May 2, 2014 11:00 AM - 12:45 PM 501 (5F)

Convener:*Kazuyuki Kita(Faculty of Science, Ibaraki University), Yuichi Onda(Center for Research on Isotopes and Environmental Dynamics, University of Tsukuba), Teruyuki Nakajima(Atmosphere and Ocean Research Institute), Yasuhito Igarashi(Atmospheric Environment and Applied Meteorology Research Department, Meteorological Research Institute), Jun Matsumoto(Deaprtment of Geography, Tokyo Metropolitan University), Masatoshi Yamada(Institute of Radiation Emergency Medicine, Hirosaki University), Chisato Takenaka(Graduate School of Bioagricultural Sciences, Nagoya University), masayoshi yamamoto(Low Level Radioactivity Laboratory, Kanazawa University), jota kanda(Tokyo University of Marine Science and Technology), atsushi shinohara(Osaka university), Chair:Kimikazu Sasa(Faculty of Pure and Applied Sciences, University of Tsukuba)

12:15 PM - 12:30 PM

[MAG38-13] Distribution of 129I in the environment released from the FDNPP accident and estimation of 131I/129I ratio

*Kimikazu SASA1, Masumi MATSUMURA1, Keisuke SUEKI1, Tsutomu TAKAHASHI1, Tetsuya MATSUNAKA1, Yukihiko SATOU1, Nao SHIBAYAMA1, Norikazu KINOSHITA2, Kenji NISHIHARA3, Hiroyuki MATSUZAKI4 (1.University of Tsukuba, 2.Shimizu Corp., 3.Japan Atomic Energy Agency, 4.The University of Tokyo)

Keywords:FDNPP accident, Radioiodine, 131I/129I, AMS

Radioiodine is one of the most important radionuclides released from the Fukushima-Daiichi Nuclear Power Plant (FDNPP) accident. 131I (half-life: 8 d) has a short half life time. Because of the difficulty of measuring 131I at this time, it is expected to estimate 131I precipitation from 129I (half-life: 1.57 × 107 y) with the long half-life in the surface soil. We have measured 129I concentrations in the surface soil at Fukushima. 129I/127I ratios were measured by accelerator mass spectrometry (AMS) at the MALT, the University of Tokyo (Matsuzaki et al., 2007). Stable iodine of 127I was determined by inductively coupled plasma mass spectrometry (ICP-MS). We already got a result that the average 129I concentration was (2.74 ± 1.35) × 108 atoms/g prior to the FDNPP accident as 129I background at Fukushima. After the accident, average isotopic ratio of 131I/129I at Fukushima is estimated to (4.02 ± 0.81) × 10-2 as at March 11, 2011. The results of calculation about 131I/129I ratio made by the ORIGEN2 code are 3.18 × 10-2 for the Unit 1, 4.57 × 10-2 for the Unit 2 and 4.81 × 10-2 for the Unit 3 (Nishihara et al., 2012). In this presentation, we report the distribution of 129I in terrestrial environment at Fukushima and 131I/129I ratios by region.