A renewed attempt to survey reactor 2 at the damaged Fukushima No. 1 nuclear power plant failed Thursday when the latest robot probe became obstructed.
The robot was inserted into the primary containment vessel at around 7:50 a.m. to approach the metal grating directly underneath the pressure vessel, where a black mass has been found.
Tokyo Electric Power Company Holdings Inc. had hoped to take a closer look at what could be melted nuclear fuel, but it was forced to abandon the operation shortly after 3 p.m.
The robot didn’t reach its objective, Tepco said, and the utility eventually severed its controller cable.
Having detected an extraordinarily high radiation level —estimated at 650 sieverts per hour — in a preparatory survey, Tepco had hoped to obtain more precise readings, images and data needed to remove fuel and other debris to decommission the plant.
In previous surveys, the utility found deposits on the grating believed to be nuclear debris and a 1-sq.-meter hole believed to have been created by molten fuel escaping from the pressure vessel.
Challenges dogged the latest attempt from the start. There was little clear surface for the robot to move around, and the radiation could kill the unit as with the preliminary surveys.
Next month, Tepco plans to survey the No. 1 reactor.