The Asahi Shimbun | Hiromi Kumai | January 29, 2016
The Fukushima No.1 nuclear power plant in Okuma, Fukushima Prefecture (Asahi Shimbun file photo)
Tokyo Electric Power Co. has postponed inspections by robots to finally confirm the location and state of melted fuel at two damaged reactors of the Fukushima No. 1 nuclear plant.
The camera-equipped robots were scheduled to enter the containment vessels of the No. 1 and No. 2 reactors within fiscal 2015, which ends in March. But TEPCO said Jan. 28 that a series of unexpected circumstances, such as poor visibility caused by murky radioactive water, have ruined that plan.
The robot for the No. 1 containment vessel will be redesigned, and the remote-controlled survey will be conducted in fiscal 2016, the utility said, without offering a more specific timetable.
Nuclear fuel assemblies in the No. 1 to No. 3 reactors are believed to have melted and fallen to the bottom of the containment vessels following the March 2011 earthquake and tsunami.
Radiation levels inside the containment vessels remain extremely high, making them too dangerous to be approached by workers.
The remote-controlled robotic probe was seen as crucial in determining conditions inside the containment vessels for the eventual decommissioning of the nuclear plant.
TEPCO conducted a preliminary survey using an industrial endoscope in the containment vessel of the No. 1 reactor. It found accumulated waste turned the water murky and blocked the view.
For the No. 2 reactor, TEPCO had planned to locate the melted nuclear fuel using a robot last summer. But decontamination and cleanup work near the entrance to the containment vessel proved difficult. That prevented TEPCO from carrying out robotic survey as planned.