Japan Geoscience Union Meeting 2014

Presentation information

Print

Oral

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

[M-AG38_2PM1] Dynamics of radionuclides emitted from Fukuchima Dai-ichi Nuclear Power Plant in the environment

Fri. May 2, 2014 2:15 PM - 4:00 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:Seiya Nagao(Institute of Nature and Environmental Technology, Kanazawa University)

3:45 PM - 4:00 PM

[MAG38-21] Distribution of radionuclides in the surface seawater developed by aerial radiological survey

*Yayoi INOMATA1, Michio AOYAMA2, Katsumi HIROSE3, Yukihisa SANADA4, Tatsuo TORII4, Takaki TSUBONO5, Daisuke TSUMUNE5, Masatoshi YAMADA6 (1.Asia Center for Air Pollution Research, 2.Fukushima University, 3.Sophia University, 4.Japan Atomic Energy Agency, 5.Central Research Institute of Electric Power Industry, 6.Hirosaki University)

Keywords:Airborne surveys, Ocean, Anthropogenic radionuclide, Gamma-ray peak count, Regional Ocean Modeling System, Fukushima Daiichi Nuclear Power Plant

This study investigated the distribution of anthropogenic radionuclide in the surface seawater derived from the Fukushima Daiichi Nuclear Power Plant (FNPP1) observed by aerial radiological survey as an initial attempt. The aerial radiological survey over the coastal region was performed by the U.S. Department of Energy National Nuclear Security Administration (DOE/NNSA) within a 30 km radius of the FNPP1 on 18 April 2011. We found good correlations between the in-situ activities of radionuclide (131I, 134Cs, 137Cs) in the surface seawater and gamma-ray peak count rates by aerial radiological surveys (correlation coefficients for 131I, 0.89; 134Cs, 0.96; 137Cs, 0.92). Based on these relations, we find that the area with high concentrations extend south-southeast from the FNPP1. The maximum concentrations of 131I, 134Cs, and 137Cs reached 329, 650, and 599 Bq L-1, respectively. The131I/134Cs ratios in surface waters of the high activities area on 18 April were about 0.6-0.7. Considering the radioactive decay of 131I (half-life: 8.02 d), we determine that the radionuclides in this area are due to direct release from FNPP1 to the ocean. These also confirm that the aerial radiological survey might be very effective to investigate the surface distribution of anthropogenic radionuclides in the surface seawater. Furthermore, the model reproduced the distribution pattern of the FNPP1 derived radionuclides, although simulated results by regional ocean model are underestimated.