The operator of the Fukushima Daiichi nuclear power plant says a robotic survey in one of its damaged reactors found what is likely to be fuel debris piling up at the bottom of its containment vessel.
The survey on Saturday examined the bottom of the containment vessel in the No.3 reactor. This followed another probe one day earlier that explored immediately below the reactor's pressure vessel.
Tokyo Electric Power Company, or TEPCO, says Saturday's probe found lumps that are highly likely to be fuel debris piling up at the bottom of the containment vessel, along with fallen reactor parts. Fuel debris is created when molten fuel mixes with structural components of a reactor. The deposits are estimated to be one to two meters thick.
Images released on Saturday show black, rock-like lumps and what appear to be pebbles and sand accumulating at the bottom. They also show what are likely to be fallen work platforms and damaged pipes.
TEPCO officials say they were able to confirm that the containment vessel of the No.3 reactor sustained substantial damage and what is believed to be structural components and other material is piling up at its bottom.
TEPCO and the government are going to determine the condition of the containment vessel based on information obtained through the surveys and then work out how to remove the fuel debris.
Removal of highly radioactive fuel debris is the biggest challenge in decommissioning the damaged reactors.