Gamma-ray imaging in Hamadori, Fukushima Prefecture

Kawahara, Rika*; Ochi, Kotaro   ; Yamaguchi, Katsuhiko*; Torii, Tatsuo*  

Currently, the difficult-to-return zones are being lifted, and it is important to determine the radiation distribution. However, Compton cameras can only provide two-dimensional radiation information, and it is impossible to determine the distance to hot spots. Therefore, in order to obtain a more detailed distribution of radiation sources, we combined a Compton camera and an optical camera to create a three-dimensional distribution map of source locations and their intensities. Two locations in the difficult-to-return zone (Okuma Town) were surveyed: a park parking lot and the vicinity of a private home. The distribution of air dose rates was determined by measurement with a survey meter with a wand-type GPS (Gamma Plotter H manufactured by Japan Radiation Engineering Co). Measurements were taken with a Compton camera (H420, H3D, USA) at several different positions and angles toward the hot spots. An optical camera (GoPro) was used to create three-dimensional images of the measurement site. The relationship between the air dose rate readable from the radiation source distribution map taken by the Compton camera and the distance from the hotspot was obtained.