Estimating annual individual doses for evacuees returning home to areas affected by the Fukushima nuclear accident

To contribute to the reconstruction and revitalization of Fukushima Prefecture following the 2011 nuclear power disaster, annual individual doses were estimated for evacuees who will re- turn home to Tamura City, Kawauchi Village, and Iitate Village in Fukushima. Ambient external dose rates and individual doses obtained with personal dosimeters were measured at many residen- tial and occupational sites throughout the study areas to obtain fun- damental data needed for the estimation. The measurement results indicated that the ratio of individual dose based on a personal dosimeter to the ambient external dose measurement was 0.7 with 10% uncertainty. Multiplying the ambient external dose by 0.7 may be an appropriate measure of the effective dose to an individ- ual in the investigated area. Annual individual doses were estimated for representative lifestyles and occupations based on the ambi- ent external dose rates at the measurement sites, taking into ac- count the relationship between the ambient external dose andindividual dose. The results were as follows: 0.6–2.3 mSv y−1in Tamura, 1.1–5.5 mSv y−1 in Kawauchi, and 3.8–17 mSv y−1 in Iitate. For all areas investigated, the estimated dose to out- door workers was higher than that to indoor workers. Identifying ways to reduce the amount of time that an outdoor worker spends outdoors would provide an effective measure to reduce dose