JpGU-AGU Joint Meeting 2017

Presentation information

[EJ] Oral

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

[M-AG34] [EJ] Dynamics of radionuclides emitted from Fukuchima Dai-ichi Nuclear Power Plant in the environment

Thu. May 25, 2017 10:45 AM - 12:15 PM Convention Hall A (International Conference Hall 2F)

convener:Kazuyuki Kita(Faculty of Science, Ibaraki University), Yuichi Onda(Center for Research on Isotopes and Environmental Dynamics, University of Tsukuba), Yasuhito Igarashi(Atmospheric Environment and Applied Meteorology Research Department, Meteorological Research Institute), Masatoshi Yamada(Institute of Radiation Emergency Medicine, Hirosaki University), Chairperson:Haruka Minowa(The Jikei University School of Medicine), Chairperson:Hiroaki Kato(Tsukuba University)

11:00 AM - 11:15 AM

[MAG34-08] Radioactivity in soil from near the Fukushima Dai-ichi Nuclear Power Plant at five years after the accident

*Haruka Minowa1, Kazuyuki Kita2, Atsushi Shinohara3, Kencho Kawatsu4, Kazuhiko Ninomiya3, Yuki Inai3, Tsutomu Ohtsuki5, Yasushi Kino6, Kazuma Koarai6, Takashi Saito7, Yukihiko Satou8, Keisuke Sueki9, Koichi Takamiya5, Yukio Takeuchi10, Taeko Doi10, Masaki Uesugi11, Satoru Endo12, Shingo Okumura13, Takahiro Ono14, Seika Onozaki14, Naoya Katsumi15, Akimitsu Kanda3, Nguyen Tat Thanh 12, Kenya Kubo16, Shuntaro Kinno15, Anna Suzuki3, Masatoshi Suzuki6, Kenji Suzuki4, Masaomi Takahashi3, Sota Takenaka11, Zi Jian Zhang3, Izumi Nakai14, Shunsuke Nakamura12, Akihiro Nambu3, Yudai Nishiyama5, Junpei Nishiyama6, Daisuke Fukuda13, Kengo Fujii13, Nobufumi Fujita3, Naoki Miyazawa11, Tomo Muranoi6, Yuichi Moriguchi17, Akiyo Yatagai18, Kouhei Yamamori11, Akihiko Yokoyama11, Go Yoshida3, Takashi Yoshimura3 (1.The Jikei University School of Medicine, 2.Ibaraki University, 3.Osaka University, 4.Fukushima University, 5.Kyoto University, 6.Tohoku University, 7.Shokei Gakuin University, 8.Japan Atomic Energy Agency, 9.Tsukuba University, 10.National Institute for Environmental Studies, 11.Kanazawa University, 12.Hiroshima University, 13.Meiji University, 14.Tokyo University of Science, 15.Waseda University, 16.International Christian University, 17.Tokyo University, 18.Hirosaki University)

Keywords:Fukushima Dai-ichi Nuclear Power Plant, radiocesium, Cs-134, Cs-137, soil deposition density

[Introduction] A large-scale soil sampling project for radionuclides from the Fukushima Daiichi Nuclear Power Plant accident was conducted in June 2011 by a research group on the Japan Geoscience Union and the Japan Society of Nuclear and Radiochemical Sciences. New research project followed by was implemented with the objective to know the transition process of radioactivity and the current contamination in 2016 when five years passed since the accident.
Between June and September 2016, 176 researcher of total were work to measure the air dose rate and collect soil samples at 105 locations near the Fukushima Dai-ichi nuclear power plant, mainly on the difficult-to-return zone, for 9 days in total. The outline of the project will be reported in another presentation. In this report, we will present the results of the inventory of 134Cs and 137Cs in the soil, the degree of destribution, the ratio of 134Cs/137Cs concentration, and the correlation with the air dose rate.
[Sample and Measurement] Surface soil of 5 samples per one location was collected from 36 public facilities in the difficult-to-return area of Futaba-machi or Okuma-machi in Fukushima Prefecture in June and July 2016. The sample from depths of 5 cm was divided into two parts of 0 - 2.5 cm depth and 2.5 - 5 cm depth, filled in a U-8 container after drying. Radiocesium was quantified using gamma ray spectrometry with Ge detectors.
[Results and Discussion] The results are shown in Fig.1 The maximum 137Cs concentration was 68400 kBq/m2 in inventory and 1180 kBq/kg(dry) in specific activity. The inventory clearly correlated with the air dose rate. There was large difference in soil distribution degree (the ratio of radioactivity of 2.5 - 5.0 cm and 0 - 2.5 cm in depth) for each sample, and the values were almost less than 1. Moreover, it was found that there are points where the concentration ratio of 134Cs /137Cs clearly has a low value of 0.87 - 0.93 in the north-north-west direction from the nuclear power plant.