The aerial radiation monitoring in Japan after the Fukushima Daiichi nuclear power plant accident

The ambient dose-rate and the deposition of radioactive cesium was measured by using helicopters in the whole area of Japan to investigate the influence of the radioactivity that discharged into the atmosphere due to the disaster of the Fukushima Daiichi NPP (Nuclear Power Plant), Tokyo Electric Power Company (TEPCO), occurred by the East Japan earthquake and tsunami on March 11, 2011. As a result, the deposition of radioactive cesium on the ground was obtained, and it was clarified that range of Cs spread had been almost limited from the southern part of Iwate Prefecture to Kanto areas. The variation distribution of the dose-rate in Japan was also revealed in this measurement.