Remote-Controlled Robot to Retrieve Melted Fuel Debris From Japan's Damaged Fukushima Reactor

Japan will use robots to retrieve the melted fuel debris from one of Fukushima's reactors over a decade after the nuclear accident.

Japan's To Deploy Robots Into Fukushima Daiichi No. 2 Reactor

For the first time since the 2011 meltdown, the operator of Japan's demolished Fukushima Daiichi nuclear power plant demonstrated on Tuesday how a remote-controlled robot might eventually remove small fragments of melted fuel debris from one of three damaged reactors.

Tokyo Electric Power Company (TEPCO) intends to test the removal of debris from the primary containment vessel of the Fukushima Daiichi No. 2 reactor using an extensible pipe robot in the "telesco-style" by October.

"We believe the upcoming test removal of fuel debris from Unit 2 is a crucial step to steadily carry out future decommissioning work," said Yusuke Nakagawa, a TEPCO group manager for the fuel debris retrieval program. "It is important to proceed with the test removal safely and steadily."

That work has been delayed by more than two years. The delays highlight how difficult it would be to recover from the magnitude 9.0 earthquake and tsunami in 2011. The removal of melted fuel was originally scheduled to start in late 2021.

At the robot's development site, the Mitsubishi Heavy Industries shipyard in Kobe, western Japan, a device fitted with tongs was seen slowly descending from the telescopic pipe to a pile of gravel, where it grasped a granule.

TEPCO will remove less than 3 grams (0.1 ounce) of debris during the test at the Fukushima plant.

Almost 880 tons of highly hazardous melted nuclear fuel are still present in the three damaged reactors. The government and TEPCO's 30-—to 40-year cleanup timetable for Fukushima Daiichi has drawn criticism for being unduly optimistic. Every reactor has a varied level of damage, so plans must take that into account.

A deeper comprehension of the melted fuel debris inside the reactors is essential for their decommissioning. Earlier this year, TEPCO sent four tiny drones into the main containment vessel of the No. 1 reactor to take pictures in places that robots had not yet reached.

Fukushima Nuclear Accident In 2011

The 2011 Fukushima accident involving the Fukushima Daiichi ("Number One") nuclear power facility in northern Japan is regarded as the second-worst nuclear accident in nuclear power generation history, behind the 1986 Chernobyl disaster. The location is in northeastern Fukushima Prefecture, on the Pacific coast of Japan, roughly 60 miles (100 km) south of Sendai.

The plant, comprised of six boiling-water reactors built between 1971 and 1979, was run by the Tokyo Electric and Power Company (TEPCO). Only reactors 1 through 3 were in operation during the disaster, and reactor four was used to store spent fuel rods temporarily. The backup generators at the Fukushima Daiichi facility were reportedly damaged by tsunami waves caused by an earthquake on March 11, 2011. Within the first several days following the accident, cooling systems in all three of the operational reactors failed despite the reactors' successful shutdown due to power outages.

Reactors 1, 2, and 3's fuel rods overheated and partially melted due to rising residual heat within each reactor's core, occasionally resulting in the emission of radiation. In late May, it was discovered that melted material had seeped into reactors 1 and 2, sinking to the bottom and boring large holes in each vessel's floor.

Such perforations partially exposed the nuclear material in the cores. On March 12 and March 14, respectively, explosions caused by a buildup of pressurized hydrogen gas occurred in the outer containment buildings of reactors 1 and 3.

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