High radiation levels may have caused robot to stop working in damaged Fukushima reactor

The operator of the Fukushima Daiichi nuclear power plant said Thursday its attempt to retrieve data from a robot from inside the No. 2 reactor had failed possibly due to extremely high levels of radiation.

Tokyo Electric Power Company Holdings Inc. (TEPCO) said the robot was sent into the damaged reactor to gather information about highly radioactive residue from melted fuel inside the reactor.

The utility believes that fuel in the reactor has likely melted through its core during the 2011 Fukushima disaster at the bottom of the plant's containment vessel.

Before the technical failure, TEPCO said the robot sent back data that reveled the level of radiation in the air three meters from the entrance to the pressure vessel was at a lethal 210 sieverts per hour.

The amount of radiation measured at that location is enough to kill a person, even after being exposed for just a brief period of time.

TEPCO added that the temperature measured at the same point was 16.5 degrees Celsius.

In an earlier survey, levels of radiation as high as 650 sieverts per hour were detected in the No. 2 reactor, much to the consternation of Japan's nuclear watchdog and the local and international public.

TEPCO on Thursday planned to collect acquire data on the current situation in the battered reactor that is pertinent to the plant's eventual decommissioning and is currently trying to determine if incredibly high radiation levels caused the self-propelled robot to malfunction.

The robot, developed by TEPCO in conjunction with Toshiba Corp. and the International Research Institute for Nuclear Decommissioning, failed to navigate its way over obstacles, the utility said, and stopped moving along a metal rail before it could reach the center of the reactor's core.

The robot was supposed to travel to where a black mass, thought to be nuclear debris, had been detected previously underneath the pressure vessel.

The robot was also supposed to reveal further information about a 1-square meter hole on the grating of the vessel caused by melted nuclear fuel.

TEPCO gave up trying to retrieve the robot and opted to cut its remote control cables, officials said.

The failed operation by TEPCO to retrieve the necessary data on the high levels of radiation, the temperature, and the amount and locations of melted fuel and nuclear debris from the damaged reactor will further complicate the decommissioning of the ravaged plant.

TEPCO, known for a number of gaffes and communication blunders over the years, however, said in a press briefing on the matter that despite the failure they had "received great hints for the next step."

Critics however have been quick to point out that potentially high levels of radiation may have also been responsible for similarly damaging a robot's electronics used in a previous survey of the reactor.

The utility said a survey will now be conducted on its No. 1 reactor next month, which also underwent a meltdown in the disaster.

TEPCO was the embattled owner and operator of the Daiichi facility in Fukushima Prefecture at the time of the worst commercial nuclear disaster in history there in 2011.

The disaster involved a massive quake-triggered tsunami knocking out the plant's key cooling functions leading to multiple meltdowns of the facility's reactors.

The crisis has yet to be fully brought under control half a decade since the incident, with no precise timeline for the full decommissioning of the notorious plant, or precise blueprint for the technological processes necessary.

The government-supported utility, to a certain extent, has also dodged local and media scrutiny of late, owing to the Tokyo 2020 Olympic Games garnering increasing coverage.

The Japanese government has said it will likely continue its effective state ownership of TEPCO because the expected costs for the increasingly complicated decommissioning of the plant and paying compensation to the victims continue to escalate. Endit