Probing Fukushima reactor wreckage
Robot continues search for melted nuclear fuel
TOKYO — An underwater robot entered a badly damaged reactor at Japan’s crippled Fukushima nuclear plant Wednesday, capturing images of the harsh impact of its meltdown.
Plant operator Tokyo Electric Power Co. said the robot, nicknamed “the Little Sunfish,” successfully completed the day’s work inside the primary containment vessel of the Unit 3 reactor at Fukushima, which was destroyed by a massive March 2011 earthquake and tsunami.
TEPCO spokesman Takahiro Kimoto praised the work, saying the robot captured views of the damage that had not been previously seen. However, the images contained no obvious sign of the melted nuclear fuel that researchers hope to locate, he said.
The robot is expected to go deeper inside for a fuller investigation Friday in hopes of finding the melted fuel.
“The damage to the structures was caused by the melted fuel or its heat,” Kimoto told a news conference held nine hours after the probe ended its exploration.
The robot, about the size of a loaf of bread, is equipped with lights, maneuvers with five propellers and collects data with two cameras and a dosimeter. It is controlled remotely.
The robot was co-developed by Toshiba Corp., the company charged with helping clean up the plant, and the International Research Institute for Nuclear Decommissioning, a government-funded consortium.
It was on a mission to study the damage and find the fuel that experts say has breached the core and mostly fallen to the bottom of the primary containment chamber, where it has been submerged by highly radioactive water as deep as 20 feet.
The robot discovered that a grate platform that is supposed to be below the reactor core apparently was knocked down by melted fuel and other materials, and that parts of a safety system called a control rod drive were missing.
Japanese officials say they want to determine preliminary methods for removing the melted nuclear fuel this summer and start work in 2021.
Scientists need to know the fuel’s exact location and understand the structural damage in each of the three wrecked reactors to work out the safest way to remove the fuel.