The operator of Japan's disaster-hit Fukushima Daiichi nuclear power plant on Tuesday failed again to retrieve vital information by sending a robot into one of its reactors.
Tokyo Electric Power Company Holdings Inc. (TEPCO) was preparing Tuesday to send a self-propelled robot to explore the inside of the No. 1 reactor and capture, then send information about the melted nuclear fuel debris so that the utility can decide how to remove it.
The deposits of fuel are believed by TEPCO to have penetrated the reactor pressure vessel and melted through the containment vessel which holds the nuclear fuel.
But Tuesday's operation to launch the shape-shifting, camera-equipped robot into the reactor was cancelled, as camera images outside the containment vessel used to monitor the robot could not be seen on the control room's screen, the utility said.
TEPCO said it will investigate the latest failure and try to deploy the robot again later this week.
The latest mishap follows a similar failed attempt on Feb. 17 to retrieve data from inside the damaged No. 2 reactor at the same facility, due to the robot malfunctioning, possibly due to extremely high levels of radiation.
TEPCO sent the robot into the damaged reactor to gather information about highly radioactive residue from melted fuel inside the reactor, believing that the fuel 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, revealing the level of radiation in air three meters from the entrance to the pressure vessel 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 planned to acquire data on the situation in the battered No. 2 reactor that is pertinent to the plant's eventual decommissioning, and is trying to determine if incredibly high radiation levels caused the self-propelled robot to malfunction.
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-meter square 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.
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 further complicated the decommissioning of the ravaged plant. Tuesday's failure has done little to help the embattled utility.
TEPCO was the owner and operator of the Daiichi facility in Fukushima Prefecture at the time of the nuclear disaster which has been unfolding since March 11, 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 more than half a decade since the incident, with no precise timeline for the full decommissioning of the plant, or a clear blueprint for the technological processes necessary.
The Japanese government has said it will likely continue its effective state ownership of TEPCO, as the expected costs for the increasingly complicated decommissioning of the plant and paying compensation to the victims continue to escalate. As many as 40,000 people fled Fukushima after the meltdowns at the Daiichi plant and 123,168 remain displaced, according to the latest figures for the National Police Agency.
The ongoing disaster, the sixth anniversary of which was observed last Sunday, remains the world's worst nuclear crisis since the 1986 Chernobyl accident.
