Japan Geoscience Union Meeting 2016

Presentation information


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

[M-AG24] Dynamics of radionuclides emitted from Fukuchima Dai-ichi Nuclear Power Plant in the environment

Mon. May 23, 2016 10:45 AM - 12:15 PM A03 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Kazuyuki Kita(Faculty of Science, Ibaraki University), Yuichi Onda(Center for Research on Isotopes and Environmental Dynamics, University of Tsukuba), Teruyuki Nakajima(Japan Aerospace Exploration Agency), Yasuhito Igarashi(Atmospheric Environment and Applied Meteorology Research Department, Meteorological Research Institute), 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(Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology), Atsushi Shinohara(Osaka university), Chair:Yuko Hatano(Graduate School of Systems and Information Engineering, University of Tsukuba)

11:45 AM - 12:00 PM

[MAG24-11] Uranium isotope ratio in Fukushima soil samples

*Asako Takamasa1, Sarata Kumar Sahoo1, Shun'ichi Nakai2, Hideki Arae1 (1.National Institute of Radiological Sciences, 2.Earthquake Research Institute)

Keywords:Fukushima soil sample, Uranium isotope, TIMS, 236U

There were huge amounts of radionuclides such as fission products released into atmosphere due to accident of Fukushima Daiichi nuclear power plant (FDNPP). A few studies have been reported about actinide elements released from FDNPP accident as fingerprint of isotope ratio using accelerator mass spectrometry (AMS). Levels of actinides were at much less concentration than 134Cs, 137Cs and 90Sr. However, we need to consider the influence of alpha ray particles on a long-term contamination in environment. We have focused on 236U isotope, and its measurement using a thermal ionization mass spectrometry (TIMS), which may be used as an index of a nuclear accident. We measured highly precise uranium isotope ratios in the soil samples from Fukushima prefecture with high Cs concentration using Isotopx Ltd. Phoenix TIMS.
We also measured Kobe and Okinawa soil samples before the accident as Global Fallout and geological standard sample as JSd-2 and NIST 4350b. Chernobyl and Kosovo samples were measured to notice artificial radioactive materials.
Soil samples were decomposed by a microwave (ETHOS one) digestion method with mixed acids after ashing. Uranium fraction from the dissolved sample was chemically separated by UTEVA-UTEVA resin chromatography to minimize interferences of Fe and Pb prior to isotope ratio measurement using TIMS and MC-ICP-MS.
Results of 235U/238U and 234U/238U ratio by TIMS and MC-ICP-MS couldn't reveal any significant difference between Fukushima soil samples and Global Fallout samples.
236U/238U detection limit of TIMS were considered by a standard solution from U ore and could be considered that was not under the influence of Global Fallout. We could measure 236U/238U ratio in U ore samples from 10-10~1.5×10-9 range. The yield for JSd-2 and NIST 4350b were noticed to be 4.2-7.8×10-8 and Kobe and Okinawa as an index of global atomic fallout were 6.5-9.8×10-9. The detailed results will be presented.