Tokyo Electric Wednesday sent a submersible robot into the primary containment vessel of the No. 3 reactor at the Fukushima No. 1 nuclear plant to probe for the exact location of melted fuel debris.
The the first day of the operation, which lasted for about three hours, failed to find the fuel. Still, engineers and technicians learned the inside of the structure was quite damaged, Tokyo Electric Power Company Holdings Inc. said in an evening news conference.
"This was the first time that a robot has entered the containment vessel of reactor 3," said Takahiro Kimoto, a Tepco spokesman. "We think this is a big step."