Features of Exposure Doses to the Public due to the Fukushima Accident

摘要

Many attempts to evaluate exposure doses to the public have been made since the Fukushima accident. Doses to the public from external exposures have been found to be more significant than those from internal exposures. Initiating restrictions on consumption of contaminated foods and drinks fairly promptly after the accident is thought to have helped. Fukushima Prefecture estimated the maximum external effective dose for the first four months after the accident at 25 mSv. Additional external effective doses of Fukushima residents in recent years have all been evaluated at within several mSv per year. Residents are not expected to receive large additional external doses after returning to the evacuated areas after the evacuation orders are lifted. NIRS has estimated the maximum thyroid dose due to inhalation of I-131 in the early phase of the accident at around 30 mSv, which corresponds to an effective dose of 1.2 mSv. Committed effective doses due to internal exposure from radiocesium intake have been estimated to be notably smaller than 1 mSv as a whole. Estimated exposure doses during the early stages of the accident have certain inevitable uncertainties for both internal and external exposures, and further investigation to reduce these uncertainties is urgent.