Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5477423 | Journal of Environmental Radioactivity | 2017 | 11 Pages |
Abstract
A low 134Cs/137Cs ratio anomaly in the north-northwest (NNW) direction from the Fukushima Dai-ichi Nuclear Power Station (FDNPS) is identified by a new analysis of the 134Cs/137Cs ratio dataset which we had obtained in 2011-2015 by a series of car-borne surveys that employed a germanium gamma-ray spectrometer. We found that the 134Cs/137Cs ratio is slightly lower (0.95, decay-corrected to March 11, 2011) in an area with a length of about 15Â km and a width of about 3Â km in the NNW direction from the FDNPS than in other directions from the station. Furthermore, the area of this lower 134Cs/137Cs ratio anomaly corresponds to a narrow contamination band that runs NNW from the FDNPS and it is nearly parallel with the major and heaviest contamination band in the west-northwest. The plume trace with a low 134Cs/137Cs ratio previously found by other researchers within the 3-km radius of the FDNPS is in a part of the area with the lower 134Cs/137Cs ratio anomaly that we found. Our result suggests that this lower 134Cs/137Cs ratio anomaly is the area which was contaminated before March 13, 2011 (UTC) in association with the hydrogen explosion of Unit 1 on March 12, 2011Â at 06:36 (UTC) and it was less influenced by later subsequent plumes.
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Authors
Shingo Kobayashi, Takayuki Shinomiya, Takahiro Ishikawa, Hitoshi Imaseki, Kazuki Iwaoka, Hisashi Kitamura, Satoshi Kodaira, Keisuke Kobayashi, Masakazu Oikawa, Norihiro Miyaushiro, Yoshio Takashima, Yukio Uchihori,