Estimating source location and spread using Compton cameras

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

Radiation distribution maps based on Compton cameras make it possible to identify hotspots where radioactive material has accumulated locally. However, the radiation distribution obtained is two-dimensional and the distance to the hotspot cannot be confirmed. In this study, a combination of a Compton camera and an optical camera was used to integrate the radiation distribution with optical images and to confirm the radiation source position and its spread, aiming at a detailed understanding of the radiation distribution. Field tests using a Compton camera (H3D, H420, USA) with a CZT (CdZnTe) semiconductor and an optical camera (GoPro) were carried out in the difficult-to-return zone, approximately 3.6 km away from the Fukushima Daiichi NPP. By taking images of the hotspot at different positions and angles, the location of the radiation source and its three-dimensional extent could be confirmed.