Estimation of β-ray dose in air and soil from Fukushima Daiichi Power Plant accident

• Published in: Journal of radiation research Vol. 55; no. 3; pp. 476 - 483
• Main Authors: Endo, Satoru, Tanaka, Kenichi, Kajimoto, Tsuyoshi, Thanh, Nguyen Tat, Otaki, Joji M., Imanaka, Tetsuji
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01-05-2014
• Subjects: Accidents; Animals; Beta Particles; Biology; Deposition; Dosage; Environmental Exposure - analysis; Environmental Exposure - statistics & numerical data; Estimates; Fukushima Nuclear Accident; Grounds; Humans; Insecta - physiology; Mathematical analysis; Models, Biological; Models, Statistical; Nuclear accidents; Radioactive Fallout - analysis; Radioactive Fallout - statistics & numerical data; Skin Physiological Phenomena; Soil (material); Soil Pollutants, Radioactive - analysis; Fukushima Daiichi Nuclear Power Plant accident; radiocesium; radioiodine; β-ray dose; radiotellurium
• ISSN: 0449-3060; 1349-9157
• DOI: 10.1093/jrr/rrt209

Following the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident of 2011, which deposited radionuclides across Tohoku and northern Kanto, β-ray dose evaluation has been performed to estimate radiation exposure for small creatures like insects as well as human skin. Using the Monte Carlo radiation transport code MCNP-4C, we calculated the β-ray dose for 129mTe, 129Te, 131I, 132Te, 132I, 134Cs and 137Cs in air as a function of altitude and in soil. These calculations of β-dose rate for each radionuclide were conducted for the conditions following the FDNPP accident, with 137Cs deposition assumed to be 1000 kBq/m2. Beta-ray dose rate was found to be ∼10-fold (resp. 5-fold) higher than the γ-ray dose rate in the soil (resp. on the ground surface) at ∼20 days after deposition, and ∼4-fold (resp. 1.7-fold) higher after 6 months or more. For convenience, the height dependence of the ratio for 0, 10, 30, 90, 180 and 365 days after deposition was obtained by a fitting function. The cumulative 70 µm β-ray dose at 30, 60 and 90 days after deposition was estimated to be 35, 45 and 53 mGy for the ground surface, and 61, 79 and 92 mGy in the soil, respectively. These results can be used to estimate the external β-ray exposure for small creatures as well as for human skin.