High radiation levels cause robot failure in damaged Fukushima reactor

Extremely high radiation levels in the Fukushima Daiichi nuclear power plant may have aborted an attempt by Tokyo Electric Power Company Holdings Inc (TEPCO) to retrieve data from a robot inside the No 2 reactor. 

The company said yesterday that the robot was sent into the damaged reactor to gather information about highly radioactive residue from melted fuel inside the reactor.

The company believed that fuel in the reactor is likely to have melted through its core during the 2011 Fukushima disaster at the bottom of the plant's containment vessel.

According to TEPCO, before it failed, the robot sent back data that revealed the level of radiation in the air three meters from the entrance to the pressure vessel was at a lethal 210 sieverts per hour, a level that could kill a person exposed for even a brief period of time.

An earlier survey had found radiation levels as high as 650 sieverts per hour in the No 2 reactor, which had alarmed Japan's nuclear watchdog and the local and international public.

The company had been trying to determine if the high radiation levels had caused the robot to malfunction even as it planned to collect and acquire data on the current situation in the battered reactor.

TEPCO needed to know the exact location and condition of the melted fuel as also the structural damage in each of the three wrecked reactors to determine the best and safest ways to remove the fuel.

TEPCO officials claim that despite the dangerously high figures, radiation had not leaked outside of the reactor.

Images captured from inside the chamber had revealed damage and structures covered with molten material, which could also contain melted nuclear fuel, and part of a disc platform hanging below the melted core.