Melted Fuel Has Been Found In One Of Fukushima's Reactors For The First Time


Jonathan O'Callaghan

Senior Staff Writer

Footage from the Little Sunfish robot. KyodoNews/YouTube

In a major breakthrough, engineers have said they may have found some of the melted radioactive fuel from one of Fukushima’s reactors. This is a vital step towards cleaning up and decommissioning the plant.

The discovery was made by a robot called Little Sunfish, which entered the flooded reactor 3 on Friday and ended its mission on Saturday. This was one of three reactors (there are six in total) that went into meltdown at the Fukushima Daiichi nuclear plant after a deadly tsunami in March 2011.


At the bottom of the primary containment vessel, the robot returned images of what looked like fuel debris. These black, lava-like objects are likely nuclear fuel that dripped out through the damaged reactor. The announcement was made by the Tokyo Electric Power Company (TEPCO), who are handling the clean-up operation.

“It’s natural to assume that the debris melted and dropped,” a TEPCO official told reporters, said the Japan Times.

They also quoted Tadashi Narabayashi, a specially appointed professor of nuclear engineering working at Hokkaido University. “The images that appear to be melted fuel debris match those found in the (1986) Chernobyl crisis,” he said. “It’s definitely fuel debris.”

If confirmed, this will be the first time fuel has been found at reactor 3 (also called Unit 3). Some of the fuel is hanging like icicles around the reactor’s control rods, while other lumps may have melted and re-solidified near a wall that supports the pressure vessel, called the pedestal.


This location explored by Little Sunfish is beneath the core, where fuel is thought to have gathered into a puddle and melted through.

It’s a long, arduous road from here though. Engineers do not expect to find all of the melted fuel from the reactors until 2021. Not until then can the clean-up and decommissioning process begin, which is expected to take four decades at a cost of $188 billion.

Little Sunfish will be vital in speeding this along. The small robot, just 30 centimeters (12 inches) long and 13 centimeters (5 inches) wide, swam into reactor 3 through a specially drilled hole. It’s unclear when or if it will go back into this reactor, but for now vital progress has been made.


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