A GIS-based evaluation of the effect of decontamination on effective doses due to long-term external exposures in Fukushima.

Despite the enormous cost of radiation decontamination, there has been almost no quantitative discussion on how much it would reduce the long-term external radiation exposure in the Evacuation Zone and Planned Evacuation Zone (restricted zone) in Fukushima. The aim of this study is to assess the effectiveness of decontamination and return options and to identify important parameters for estimating the long-term cumulated effective dose (CED) during 15, 30 and 70 year period using data on land-use, population and decontamination in the restricted zone (about 1100 km(2)) in Fukushima. Decontamination of the land is assumed to have a certain efficacy in terms of the reduction of CED. The EeCC (external exposure conversion coefficient) is the parameter having the greatest effect on the percentage of area having CED during the 30 years above 100 m Sv after decontamination, ranging from 13% (EeCC=0.2) to 55% (EeCC=0.6). Therefore, we recommend a detailed investigation of the EeCC in Japan.