Distribution of dose-rates and deposition of radioactive cesium by the airborne monitoring surveys

To survey the impact of radioactive cesium emitted into the atmosphere and deposited into the ground surface as a result of the accident at the Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Plant, wide-range radiation monitoring via aircraft (hereinafter, airborne monitoring) was conducted in eastern Japan. An advantage of airborne monitoring is that it provides a "surface"-based understanding of air dose rates and deposition amount distributions of radioactive cesium by rapidly measuring gamma rays across a wide range, from urban areas to mountain forests, and the data are visually easy to understand. Through this airborne monitoring, in addition to the spatial dose rates and distribution of deposition amounts of radioactive cesium in each area of eastern Japan, we also gained an understanding of the air dose rate distribution of natural nuclides in eastern Japan, for which there have been no detailed measurement results until now. An overview of the wide range of airborne monitoring results in eastern Japan and the issues faced moving forward are explained herein. (author)