Robot begins removal of melted fuel from the Fukushima nuclear plant, could take a century

Robot enters Fukushima reactor to retrieve melted fuel debris, marking crucial step in long, challenging cleanup process.

A long robot entered a damaged reactor at Japan's Fukushima nuclear power plant on Tuesday (September 10, 2024), beginning a two-week, high-stakes mission to retrieve for the first time a tiny amount of melted fuel debris from the bottom.

The robot's trip into the Unit 2 reactor is a crucial initial step for what comes next — a daunting, decades-long process to decommission the plant and deal with large amounts of highly radioactive melted fuel inside three reactors that were damaged by a massive earthquake and tsunami in 2011. Specialists hope the robot will help them learn more about the status of the cores and the fuel debris.

Here is an explanation of how the robot works, its mission, significance and what lies ahead as the most challenging phase of the reactor cleanup begins.

Nuclear fuel in the reactor cores melted after the magnitude 9.0 earthquake and tsunami in March 2011 caused the Fukushima Daiichi nuclear plant's cooling systems to fail. The melted fuel dripped down from the cores and mixed with internal reactor materials such as zirconium, stainless steel, electrical cables, broken grates and concrete around the supporting structure and at the bottom of the primary containment vessels.

The reactor meltdowns caused the highly radioactive, lava-like material to spatter in all directions, greatly complicating the cleanup. The condition of the debris also differs in each reactor.

Tokyo Electric Power Company Holdings (TEPCO) which manages the plant, says an estimated 880 tons of molten fuel debris remains in the three reactors, but some experts say the amount could be larger.

Workers will use five 1.5-meter-long pipes connected in sequence to manoeuvre the robot through an entry point in the Unit 2 reactor's primary containment vessel. The robot itself can extend about 6 meters inside the vessel. Once inside, it will be manoeuvred remotely by operators at another building at the plant because of the fatally high radiation emitted by the melted debris.