Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10686612 | Journal of Environmental Radioactivity | 2016 | 9 Pages |
Abstract
To evaluate the deposition density and extent of subsurface infiltration of 129I and 137Cs in the restricted area that was highly contaminated by the accident of Fukushima Dai-ichi Nuclear Power Plant, cumulative inventories of 129I and 137Cs, concentrations of 129I and 137Cs, and 129I/137Cs ratio in 30-cm-long soil columns were compared with pre-accident levels from the same area. The cores were collected before and after the accident from locations of S-1 (4 km west of FDNPP) and S-2 (8 km west of FDNPP). Deposition densities of 129I and 137Cs in the soil following the accident were 0.90-2.33 Bq mâ2 and 0.80-4.04 MBq mâ2, respectively, which were 14-39 and 320-510 times larger than the pre-accident levels of 129I (59.3-63.3 mBq mâ2) and 137Cs (2.51-7.88 kBq mâ2), respectively. Approximately 90% of accident-derived 129I and 137Cs deposited in the 30-cm soil cores was concentrated in the surface layer from 0 to 44-95 kg mâ2 of mass depth (0-4.3-6.2 cm depth) and from 0 to 16-25 kg mâ2 of mass depth (0-1.0-3.1 cm depth), respectively. The relaxation mass depths (h0) of 10.8-11.2 kg mâ2 for 129I estimated in the previous study were larger than those of 8.1-10.6 kg mâ2 for 137Cs at both sites, owing to the larger infiltration depth of radioiodine mainly by the gravitational water penetration in the surface soil in our study sites. Approximately 7-9% of the accident-derived 129I was present in the lower layer from 44 to 100 kg mâ2 (4.3-8.6 cm depth) at S-1, and from 95 to 160 kg mâ2 (6.2-10.2 cm depth) at S-2. Approximately 1% of 137Cs seems to infiltrate deeper than 129I in the lower layer at each site in contrast to the surface layer.
Keywords
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Physical Sciences and Engineering
Energy
Nuclear Energy and Engineering
Authors
Tetsuya Matsunaka, Kimikazu Sasa, Keisuke Sueki, Tsutomu Takahashi, Yukihiko Satou, Masumi Matsumura, Norikazu Kinoshita, Jun-ichi Kitagawa, Hiroyuki Matsuzaki,