Survey in Fukushima Daiichi NPS by combination of human and remotely-controlled robot

Abstract

Highly contaminated puddles were found outside the apparatus hatch in No.3 reactor building in Fukushima Daiichi NPS. These puddles indicated a possibility of cooling water leakage from Primary Containment Vessel (PCV). Therefore, it was necessary to survey whether there was a leakage or not. However surveying was impossible for human because of two main reasons, the narrow access route of 100mm width and the high ambient radiation level. Accordingly, to realize the survey, a small remotely-controlled robot and an overlook camera device were developed by TEPCO Research Institute (TRI). This robot system was deployed in Fukushima Daiichi, going through several tests and a risk assessment for confirming its reliability. The survey was executed successfully by the combination of human and the robot system in November 2015, and finally traces of water leakage were found on the edge of the apparatus hatch.