Evaluation of averted doses to members of the public by tap water restrictions after the Fukushima Daiichi Nuclear Power Plant Accident

Kinase, Sakae   ; Kimura, Masanori ; Hato, Shinji*

After the Fukushima Daiichi Nuclear Power Plant Accident, temporal changes in the concentration of the iodine 131 in tap water were studied using published data from several authorities in Fukushima, Ibaraki and Tokyo. Averted doses to members of the public due to intake of iodine 131 through tap water restrictions were also evaluated using an internal dose calculation code, DSYS-chronic. Consequently, it was found that the apparent half-life of iodine 131 in tap water was 2.8 days. The averted equivalent doses to the thyroids of members of the public-1-year-old children- were found to be a maximum value of 13.0 mSv in a local area of Fukushima. In comparison with Fukushima, the bottled water supplies might be a large sum of money regardless of the low doses in Tokyo. In conclusion, apart from the bottled water supplies, the tap water restrictions implemented by the authorities would be effective in the early phase of the emergency exposure situation.