TOKYO, July 19 (Xinhua) -- Tokyo Electric Power Company Holdings Inc. (TEPCO), the operator of the crippled Fukushima Daiichi nuclear power plant, deployed an underwater robot on Wednesday to survey a reactor containment vessel at one of the plant's units that is full of radioactive water.
The exact location of a large amount of melted nuclear fuel debris inside the No. 3 reactor, one of three which underwent core meltdowns in the 2011 earthquake and tsunami-triggered disaster, which knocked out the plant's key cooling and backup systems, remains unknown.
Following multiple failed attempts, TEPCO is hoping the remote controlled robot will be able to capture images below the reactor pressure vessel and thereafter at the the bottom of the containment vessel, where the deposits of melted fuel debris have likely accumulated.
TEPCO believes that more than 6 meters of contaminated water has accumulated at the bottom of the containment vessel and that radiation levels inside the reactors still remain exceedingly high, six years after the worst nuclear catastrophe since the 1986 Chernobyl disaster.
An underwater camera-equipped robot is necessary, TEPCO said, as the water levels inside the No. 3 reactor are higher than other reactors.
The utility said it deployed the robot earlier in the day through a pipe that links to the containment vessel.
In February and March, attempts by TEPCO to conduct similar surveys at the No. 1 and No. 2 reactors failed, as initially, camera images outside the containment vessel that are used to monitor the robot could not be seen on the control room's screen, and a subsequent attempt saw the robot malfunction, possibly due to extremely high levels of radiation.
The information needed to be collected by the robots from inside the damaged reactors includes the necessary data on the high levels of radiation, the temperature, and the amount and locations of melted fuel and nuclear debris, as this data is essential for the eventual decommissioning plans of the tsunami-ravaged plant.
The crisis has yet to be fully brought under control more than five years since the disaster unfolded, 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 because the expected costs for the increasingly complicated decommissioning of the plant and the paying of compensation to the victims of the disaster 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.
