Temporal variation in environmental radioactivity and radiation exposure doses in the restricted areas around the Fukushima Daiichi Nuclear Power Plant

Abstract

Temporal variation and fluctuation in environmental contamination in Futaba town and Okuma town, the location of the Fukushima Daiichi Nuclear Power Plant (FDNPP), were evaluated based on a car-borne survey conducted from October 2021 to November 2022. Although the environmental radioactivity levels in the interim storage facility area (ISF) were higher than those in open areas (i.e., the evacuation-order-lifted areas in Futaba town and the specific reconstruction and regeneration base area [SRRB] in Okuma town), only minor changes were seen in the ambient dose and radiocesium detection rates in the ISF and SRRB, respectively. These findings suggest that such differences may be the result of multiple factors such as physical decay (decreasing factor) and radiocesium resuspension (non-decreasing factor) accompanied by human activity such as traffic and decontamination construction in these areas, in addition to weather conditions such as wind direction. However, the higher radiation exposure doses in the ISF and SRRB were estimated to be at a limited level (lower than the public dose). Therefore, to help ensure the safety and future prosperity of residents and communities in the affected areas around the FDNPP, long-term follow-up monitoring of temporal dose levels during the recovery and reconstruction phases is extremely important.