title: Assessment of residual doses to population after decontamination in Fukushima Prefecture.
abstract: Large quantities of radioactive materials were released into the environment as a result of the Fukushima Daiichi Nuclear Power Station accident. Many inhabitants residing in the affected areas are now exposed to radiation in their daily lives. In an attempt to manage this radiation dose, an additional radiation dose of 1 mSv/y was adopted as a long-term dosimetric target. An activity level reading of 0.23 μSv/h was then determined as a guidance value to achieve the target by implementing decontamination measures. The objectives of this study are to assess the effects of decontamination based on this guidance value and to predict any possible future problems with the decontamination strategy. Using a probabilistic approach, we assessed the annual effective dose of indoor workers, outdoor workers, and pensioners in the Fukushima Prefecture. Our probabilistic model considers the variabilities in behavioral patterns and Cs-137 surface-activity levels. Five years after the initial contamination, the 95th percentiles of indoor workers and pensioners in 53 of the 59 municipalities were found to receive annual effective doses of below 1 mSv/y (0.026-0.73 mSv/y). However, for outdoor workers in 25 municipalities, the annual doses were over 1 mSv/y (1.0-35 mSv/y). Therefore, the guidance value is effective for indoor workers and pensioners; to determine whether additional countermeasures for outdoor workers should be implemented, a detailed assessment that uses more realistic assumptions is required.
authors.affiliation: Nuclear Safety Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki, 319-1195, Japan. Electronic address: mori.airi@jaea.go.jp.
authors.forename: Airi
authors.initials: A
authors.lastname: Mori
authors.affiliation: Nuclear Safety Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki, 319-1195, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Takahara
authors.affiliation: Nuclear Safety Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki, 319-1195, Japan.
authors.forename: Azusa
authors.initials: A
authors.lastname: Ishizaki
authors.affiliation: Nuclear Safety Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki, 319-1195, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Iijima
authors.affiliation: Nuclear Safety Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki, 319-1195, Japan; Fukushima Environmental Safety Center, Japan Atomic Energy Agency, Sakae-machi, Fukushima-shi, Fukushima, 960-8031, Japan.
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Sanada
authors.affiliation: Nuclear Safety Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki, 319-1195, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Munakata
mesh_terms: D003666:Decontamination; D062406:Fukushima Nuclear Accident; D006801:Humans; D007564:Japan; D011829:Radiation Dosage; D000069079:Radiation Exposure / Q000706:statistics & numerical data*; D011834:Radiation Monitoring
keywords: Decontamination; Fukushima Daiichi Nuclear Power Station accident; Inter-populational variability; Probabilistic approach; Residual dose; Spatial variability