Evaluation of averted doses to infants by tap water restrictions after the Fukushima Daiichi Nuclear Power Plant accident

Kinase, Sakae   ; Kimura, Masanori ; Takahara, Shogo  ; Homma, Toshimitsu

There has been some concern in reviewing the effectiveness of making decisions on the implementation of protective measures in the emergency exposure situations. After the Fukushima Daiichi Nuclear Power Plant accident, characterization of the concentration of radioiodine-131 in tap water has been studied using the validated measurements from some authorities in Fukushima, Ibaraki and Tokyo. Levels of averted doses to infants -1-year-old children- due to intakes of radioiodine-131 by tap water restrictions were calculated using the measurements. Consequently, it was found that the concentration of radioiodine-131 in tap water provided by the authorities had an apparent half-life 2.8 days. The averted equivalent doses to the thyroids of 1-year-old children were found to be a maximum value of 8.3 mSv in a local area of Fukushima. Hence the tap water restrictions implemented by the authorities would be acceptable in the early phase of the emergency exposure situation.