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Development of analysis method for airborne radiation monitoring using the inverse problem solutions

Following the accident at the Fukushima Daiichi Nuclear Power Plant, some kind of unmanned aerial vehicles (UAVs) have been used to collect environmental radiation data. The Japan Atomic Energy Agency has been developed methods for analyzing radiation measurements taken by a small multirotor UAV. In the conventional method, count rate was converted to the air dose rate using a simple parameter. Therefore, such a conversion of the air dose rate using the conventional method is difficult in an area where the distribution of air dose rate is heterogeneous, or the terrain is complex. The goal of this study was to apply the inverse radiation method, which is used in medical applications such as positron emission tomography, for environmental radiation measurement. Basic algorithm was established for conversion from count rate to air dose rate in considering of topographic data. The algorithm was applied to real radiation data obtained by a UAV, and its accuracy was evaluated by comparing that data with ground measurement data. As compared with conventional methods, our algorithm was demonstrated to achieve a more accurate estimation of the air dose rate on the ground.