External dose assessment for inhabitants in Iitate village until evacuation after the Fukushima-1 NPP accident

The maximum contamination due to the nuclear accident at Fukushima Daiichi Nuclear Power Plant occurred in March 15, 2011 over thin and long area including Namie Town, Iidate Village, Fukushima City. The maximum dose rate recorded at the monitoring post situated near Iidate Village Office was 44.7 microSv/h. Unfortunately the rain and snow fall coincided with the arrival of the radioactive plume and resulted the stick of radioactive materials on the ground. Highly contaminated area located outside 20 km from the Plant, including Iidate Village, was assigned as 'evacuation-prepared area' on April 22, and the evacuation was planned to be executed within one month. Through this process, some inhabitants of Iidate Village spent a few months in highly contaminated area, and radiation dose of these inhabitants exceeded the doses of inhabitants within 20 km from the Plant who had been evacuated on March 12. Average personal radiation dose of the inhabitants of Iidate Village as of July 31 is estimated to be 7.0 mSv. Details of the estimation are described. (J.P.N.)