Assessment of averted doses for the verification of seafood distribution/consumption restrictions imposed after the FDNPP accident

森 愛理; 飯本 武志*; 高原 省五 

Mori, Airi; Iimoto, Takeshi*; Takahara, Shogo

Radionuclides released due to the Fukushima Daiichi NPP accident were deposited from the atmosphere onto land and into the sea, contaminating foods in the areas affected by the accident. To reduce internal exposures, the Government of Japan imposed restrictions of distribution of food. The current standard was introduced to ensure safety and security during the high social anxiety after the accident, and it was exceptionally strict in comparison with other countries and regions. More than 14 years after the accident, radionuclide concentrations in food have decreased significantly, and fewer foods exceed the standard. At the same time, a large number of costs are still required to maintain the restrictions and to provide financial support to farmers and fishermen. It is necessary to review whether the current standard was reasonable in terms of the radiation protection and of economic and social impacts. This study aims to validate current restrictions by assessments of averted doses due to restrictions, evaluations of costs for restrictions, and assessment of the reasonableness of restrictions based on the above. This presentation focuses on the first step. Previous studies have revealed that even with conservative assumptions, the ingestion dose does not exceed the target annual additional dose of 1 mSv. This study assesses how much ingestion dose was reduced by restrictions. It requires more realistic assessments that accurately reproduce the restrictions actually applied. This study first focused on seafood, which has been most affected by restrictions in terms of the domestic distribution volume. The 95th percentile value of the annual committed effective dose to a general Japanese adult was 19 Sv. In contrast, when assuming that restrictions were not imposed, the 95th percentile dose was 25 Sv, and the averted dose was 5.5 Sv. This study will provide important information for optimizing radiological protection measures for ingestion doses.