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

ABSTRACT

The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., went into meltdown in the aftermath of a large tsunami caused by the Great East Japan Earthquake of 11 March 2011. The measurement of radiation distribution inside the FDNPS buildings is indispensable to execute decommissioning tasks in the reactor buildings. We conducted a radiation imaging experiment inside the turbine building of Unit 3 of the FDNPS by using a compact Compton camera and succeeded in visualizing high-dose contamination (up to 3.5 mSv/h). In addition, we 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 a scanning LRF. The radiation distribution map shows the positions of these contaminations on a real space image of the turbine building. The radiation distribution map helps workers to easily recognize radioactive contamination and to decrease their own exposure to radiation because the contamination cannot be observed with the naked eye.

KEYWORDS:

• Radiation imaging
• radiation distribution map
• Fukushima Daiichi Nuclear Power Station
• decommissioning

Acknowledgments

The authors wish to acknowledge engineers of Tokyo Electric Power Company Holdings, Inc., for supporting the experiment inside the turbine building of Unit 3 of the FDNPS. The authors also wish to acknowledge K. Minemoto of Visible Information Center, Inc. for supporting the development of the 3D reconstruction of the radiation image and Prof. J. Kataoka and A. Kishimoto of Waseda University, S. Nakamura and M. Hirayanagi of Hamamatsu Photonics K.K. for development of base technologies of the compact Compton camera. This research was partly supported by a grant-in-aid under the Fukushima innovation coast initiative.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was partly supported by the Fukushima innovation coast initiative.