Study on urban environmental radioactivity around Fukushima Daiichi Nuclear Power Plant

吉村 和也  

Yoshimura, Kazuya

Air dose rate and Cs inventories were investigated using in-situ measurement methods in residential areas located in an evacuation zone in Fukushima. The air dose rate distribution was investigated through a walking survey, which was conducted by operators carrying a -ray detector on their backs. The Cs inventories on paved and permeable grounds were measured by a portable -ray detector equipped with a collimator. The air dose rate decreased faster in residential areas than in agricultural fields. The Cs inventory on paved surfaces decreased with time owing to the horizontal wash-off, while the horizontal wash-off of Cs were not confirmed on permeable surfaces. These findings suggest that the horizontal wash-off of Cs on paved surfaces facilitated the air dose rate decrease in residential areas to a greater extent compared with agricultural fields. As shown above, the in-situ measurement methods used in this study are useful tool to evaluate time dependency of environmental radiation.