Regional Case Studies: Environmental Radioactivity Levels and Estimated Radiation Exposure Doses of Residents and Workers in Areas Affected by the Fukushima Daiichi Nuclear Power Plant Accident

Abstract

Nagasaki University established four satellite offices within a 30-km radius of the Fukushima Daiichi Nuclear Power Plant (FDNPP) in Japanʼs Fukushima Prefecture: in Kawauchi Village, Tomioka Town, Okuma Town, and Futaba Town. To evaluate the external and internal exposures attributable to the FDNPP accident, environmental radioactivity levels continue to be investigated at these sites. Our previous studies examined specific and regional case studies based on in-situ environmental radioactivity monitoring activities. Their findings suggested that current external and internal exposure doses of radiocesium have been controlled at the lower limit of the current “exposure situation” (1–20 mSv/y, International Commission on Radiological Protection) in the evacuation order-lifted areas of Kawauchi Village and Tomioka Town. However, conducting long-term follow-up studies, such as environmental radioactivity monitoring, developing countermeasures for further decontamination in the difficult-to-return zone, and implementing restrictions on the consumption of local foods, are all needed to reduce unnecessary radiation exposure to residents and workers, particularly since radiocesium derived from the FDNPP accident remains in some areas around the site. These case studies have clarified scientifically the temporal dose levels and aided in the development of environmental remediation measures that consider radiation exposure in the recovery and reconstruction process following the accident.