Radiation imaging using a compact Compton camera inside the Fukushima Daiichi Nuclear Power Station building

Sato, Yuki  ; Tanifuji, Yuta ; Terasaka, Yuta   ; Usami, Hiroshi; Kaburagi, Masaaki   ; Kawabata, Kuniaki   ; Utsugi, Wataru*; Kikuchi, Hiroyuki*; Takahira, Shiro*; Torii, Tatsuo  

The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., went into meltdown after the occurrence of a large tsunami caused by the Great East Japan Earthquake of March 11, 2011. The radiation distribution measurements inside the FDNPS buildings are indispensable to execute decommissioning tasks in the reactor buildings. We conducted the radiation imaging experiment inside the turbine building of Unit 3 of the FDNPS using a compact Compton camera, and succeeded in visualizing the high-dose contamination (up to 3.5 mSv/h). We also drew a three-dimensional radiation distribution map inside the turbine building by integrating the radiation image resulting from the Compton camera into the point cloud data of the experimental environment acquired using the scanning laser range finder. The radiation distribution map shows the position of these contaminations on the real space image of the turbine building. The radiation distribution map helps workers to easily recognize the radioactive contamination and to decrease the radiation exposure; the contamination cannot be observed with the naked eye, naturally.