Feb 11 (NHK) - The operator of the damaged Fukushima Daiichi nuclear plant released on Thursday new images of possible fuel debris under the water inside the facility's No.1 reactor.
Tokyo Electric Power Company, or TEPCO, began a robot probe inside the reactor's containment vessel on Tuesday.
The newly-released images taken inside the containment vessel show matter accumulated inside the opening of a structure called a pedestal that supports the reactor.
TEPCO said the deposit could be fuel debris as it was found right below the reactor.
Fuel debris is a mixture of molten nuclear fuel and surrounding parts.
The company also released radiation data measured by a device inside the robot. The device detected radiation levels of one to two Sieverts per hour when it passed through the containment vessel.
The utility plans to put a second robot in to measure the thickness and distribution pattern of the deposit using ultrasonic waves. It also plans to collect a small portion of the sediment as a sample for detailed analysis.
The Fukushima Daiichi plant suffered a triple meltdown in the March 2011 earthquake and tsunami.
Previous surveys confirmed the presence of deposits believed to be fuel debris in the No. 2 and No. 3 reactors, but not in the No. 1 unit.
Removing the extremely radioactive debris is thought to be the biggest challenge in decommissioning the plant.
