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Torii (2020) Remote detection of radioactive hotspot using a Compton camera mounted on a moving multi-copter drone above a contaminated area in Fukushima,

At the Fukushima Daiichi Nuclear Power Station (FDNPS) where an accident occurred due to a large tsunami caused by the Great East Japan Earthquake, understanding the distribution of radioactive substances is important to reduce the exposure dose to workers and establish decontamination plans. We focused on the importance of visualizing beta-emitting radiation sources in addition to gamma-emitting ones and proposed a method for three-dimensionally (3D) visualizing the location of beta-emitting radiation sources, which is important in discussing the effective dose for the crystalline lens of the eye. In this report, we have developed a technique to visualize the location of beta-emitting radiation sources in 3D by combining a directional Geiger-Mueller counter (G-M counter) with Structure from Motion (SfM). An image of 90Sr beta-ray source reconstructed using a beta-ray detector was projected onto a 3D model of the measurement area created using SfM, and the source location is identified in 3D. Additionally, we estimated the radioactivity of the visualized source. Then, by combining the beta-ray detector with a Compton camera, distinguishing between beta- and gamma-emitting radiation sources was possible. This study was based on the concept of integrated radiation imaging system (iRIS), which integrates multiple radiation detectors and environmental recognition devices.

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Identifying and visualizing the radiation source location are important in reducing the radiation exposure of workers at the decommissioning site of the Fukushima Daiichi Nuclear Power Station and in improving the radiation protection functions in other sites where radiation sources are handled. In this paper, we developed the COMpton camera for Radiation Imaging System (COMRIS) to identify and visualize the radiation source location in 3D using output data from a Compton camera and a simultaneous localization and mapping (SLAM) device as input data. Here, we presented COMRIS to visualize a 137Cs-radiation source in a dark environment using data acquired by a commercial Compton camera and a LiDAR-based SLAM device mounted on a robot as input data. The radiation source image obtained using the Compton camera was drawn on the 3D work environment model acquired by the SLAM device, and the radiation source location was visible in 3D.