Probabilistic Assessment of Doses to the Public Living in Areas Contaminated by the Fukushima Daiichi Nuclear Power Plant Accident

Shogo Takahara, Masashi Iijima, Kazumasa Shimada, Masanori Kimura, and Toshimitsu Homma

Abstract Many residents are exposed to radiation in their daily lives in the areas contaminated by radioactive materials by the Fukushima Daiichi Nuclear Power Plant accident. To protect the people from radiation exposures adequately, dose assessment is necessary. The aim of this study is to provide the scientifically based quantitative information about a range of received doses to the people from the evacuation areas and the deliberate evacuation areas. To achieve this aim, we adopted a probabilistic approach that can provide the information about a range of doses and their likelihood of occurrence taking into account uncertainty and variability of input data. The dose assessment was performed based on the measurement data of the surface activity concentrations of 137Cs and the results of actual survey on behavioral patterns of the population groups living in Fukushima Prefecture. As the result of assessment, the 95th percentile of the annual effective dose received by the inhabitants evacuated was mainly in the 1–10 mSv dose band in the first year after the contamination. However, the 95th percentile of the dose received by some outdoor workers and inhabitants evacuated from highly contaminated areas was in the 10–50 mSv dose band.

Keywords Behavioral pattern • Dose assessment • Exposure pathways • Fukushima Daiichi Nuclear Power Plant Accident • Measurement data • Probabilistic approach

• Public exposure

Introduction

After the Tohoku District Pacific Ocean Earthquake, large tsunamis struck the Fukushima Daiichi Nuclear Power Plant (1F Plant), which led to a nuclear accident that released a large amount of radioactive materials into the environment [1]. In the areas contaminated by the accident, many residents are now being exposed to radiation through various exposure pathways in their daily lives. To protect people from radiation exposures and manage the exposure situation appropriately, a suitable dose assessment is necessary [2]. The aim of this study is to provide preliminary results of the assessment of radiation doses received by the inhabitants of Fukushima Prefecture. This assessment is intended to be realistic and comprehensive. For this purpose, the doses are assessed by a probabilistic approach based on environmental monitoring data and realistic lifestyle habits in Fukushima prefecture.

 
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