A robot retrieves the first melted fuel from Fukushima nuclear reactor

TOKYO — A remote-controlled robot has safely returned with a tiny piece of melted fuel it collected from inside one of three damaged reactors at the tsunami-hit Fukushima Daiichi nuclear power plant for the first time since the 2011 meltdown.

The Tokyo Electric Power Company Holdings, which manages the plant, said Saturday that the extendable fishing rod-like robot successfully clipped a gravel as big as 5 millimeters (2 inches), the size of a tiny granola bit, from the top surface of a mound of molten fuel debris that sits on the bottom of the No. 2 reactor’s primary containment vessel.

The “telesco” robot, with its frontal tongs still holding the melted fuel bit, returned to the enclosed container for safe storage after workers in full hazmat gear pulled it out of the containment vessel earlier Saturday.

The sample return marks the first time the melted fuel is retrieved out of the containment vessel. But the mission is not over until it’s certain that the sample’s radioactivity is below a set standard and safely placed into a container.

If the radioactivity exceeds the limit, the robot must go back inside the reactor to find another piece. TEPCO officials said they expect the piece is small enough to meet the requirement.

The mission initially started in August for what was supposed to be a two-week round trip but had been suspended twice due to mishaps.

First one was the procedural mistake at the beginning that held up the work for nearly three weeks, then the robot’s two cameras designed to transmit views of the target areas for its operators in the remote control room failed. The camera problem required the robot to be pulled out all the way for replacement before the mission resumed Monday.

Fukushima Daiichi lost its key cooling systems during the 2011 earthquake and tsunami, causing meltdowns in its three reactors. An estimated 880 tons of fatally radioactive molten fuel remains in them, and TEPCO has carried out a number of robotic probes to figure out how to decommission the plant.

Telesco on Wednesday successfully clipped a piece presumably measuring less than 3 grams (0.1 ounce) from the planned area right underneath the Unit 2 reactor core, from which large amounts of melted fuel fell during the meltdown 13 years ago, TEPCO said.

Plant chief Akira Ono said only the tiny spec can provide key data to plan decommissioning strategy, develop necessary technology and robots and retroactively learn how the accident had developed.

The government and TEPCO have set a 30-to-40-year target for the cleanup, which experts say is overly optimistic and should be updated.

No specific plans for the full removal of the fuel debris or its final disposal have been decided.