This frame grab provided by Japan's International Research Institute for Nuclear Decommissioning on July 19, 2017, shows the lower part of a control rod drive inside reactor No. 3 at Fukushima Dai-ichi nuclear power plant .
TOKYO – The operator of Japan's stricken Fukushima nuclear plant said on Friday it was using an underwater robot in a renewed attempt to inspect damage suffered in a tsunami-induced meltdown.
A massive undersea earthquake on March 11, 2011 sent a huge wave barreling into Japan's north-east coast, killing more than 18,500 people, and sending three reactors into meltdown at the plant in the worst such accident since Chernobyl in 1986.
Tokyo Electric Power Co (TEPCO) in February sent a remote-controlled robot into one of three damaged reactors where radiation levels hit record highs.
But the mission was aborted at the Number Two reactor after the robot could not reach its target destination beneath a pressure vessel, through which nuclear fuel is believed to have melted as the robot had difficulty moving.
Locating the fuel debris is part of the decommissioning process for the plant, expected to take decades.
On Wednesday, TEPCO sent a robot measuring 13 centimetres wide and 30 centimetres long to the Number Three reactor and conducted another inspection on Friday, a spokesman said.
But the company has yet to find the fuel debris.
"Today, the robot went deeper inside the containment vessel" of the reactor, he said, referring to the Friday probe, adding that TEPCO will analyse the images.
The Japanese government said in December that it expected total costs including compensation, decommissioning and decontamination to reach 21.5 trillion yen (R2.49-trillion) in a process likely to take at least four decades as high radiation levels slowed operations.