This week, workers at the Fukushima nuclear power plant stood silent for one minute to commemorate the 10th anniversary of the natural disaster that caused the worst nuclear accident since Chernobyl.
They then went back to work dismantling the melted reactors in the days following a tsunami on March 11, 2011.
The job is considered the most expensive and dangerous nuclear cleanup ever attempted. A decade later, an army of engineers, scientists and 5,000 workers are still plotting a project that many predict will not be completed in their lifetime.
Naoaki Okuzumi, head of research at Japan’s leading decommissioning research institute, likens the work ahead to climbing a mountain range, without a map.
“The feeling we get is that you think the top is right there, but then you reach it and you can see another peak, beyond,” Okuzumi said.
Okuzumi and others have to find a way to safely remove and store 880 tons of highly radioactive uranium fuel along with a larger mass of concrete and metal where the fuel melted a decade ago during the accident.
The robotic tools to do the job do not yet exist. Nor is there any plan for where to place the radioactive material when it is removed.
The Japanese government says the job could take 40 years. Outside experts say it could take twice that long, leading to completion by the end of the century.
Tepco’s Fukushima Daiichi nuclear power plant, which once had six reactors, was plunged into crisis by the tsunami that followed a magnitude 9.0 earthquake off the coast of northern Japan on March 11, 2011.
The earthquake and tsunami flooded Fukushima’s backup power generators, knocking cooling systems out of service. The reactors quickly overheated, causing explosions as uranium cores melted. The radioactive plumes that formed forced the evacuation of some 160,000 people.
It wasn’t until 2017 that engineers realized how complicated the cleanup would be. By then, five specially designed robots had been sent through the dark, contaminated pumped water to cool the uranium. However, the radiation has knocked out their electronics.
A robot developed by Toshiba Corp, dubbed the “little sunfish,” a device the size of a loaf of bread, provided a first glimpse of the chaotic damage around the cores.
Kenji Matsuzaki, a Toshiba robotics technician who led the development of the “little sunfish,” had assumed they would find molten fuel at the bottom of the reactors.
But early video footage from the “sunfish” showed a tumult of destruction, with overturned structures inside the reactor, clumps of unrecognizable brown debris and dangerously radioactive metal.
“I expected it to be broken, but I didn’t expect it to be this bad,” Matsuzaki said.
Delivery of a robotic arm to begin removing the fuel, developed in a $16 million program with the U.K. Nuclear Decommissioning Authority, has been delayed until 2022. Tepco plans to use it to grab some debris from inside reactor 2 for testing and to help plan the main operation.
Radiation has been reduced at most of the Fukushima site, the size of New York’s Central Park. In most areas of the plant, the 5,000 workers no longer need special protective gear that had slowed work during Japan’s hot, humid summers.
But cleanup has been delayed by the buildup of contaminated water in the tanks that crowd the site. Molten cores are kept cool by pumping water into the damaged reactor vessels.
The water is pumped out and treated. The storage tanks now contain enough radioactive water to fill more than 500 Olympic-size swimming pools. Tepco expects to run out of storage space next year.
Most analysts expect the government to release the water into the ocean after additional treatment. Fishing communities have opposed this, and South Korea and China have opposed the move.
There is still no plan on where to place the radioactive remains of the reactors.
“It’s no good just moving the highly radioactive waste from inside the nuclear reactor to another location in the power plant,” said Hiroshi Miyano, head of the decommissioning committee at the Japan Atomic Energy Society. “Where will the waste go, will it be pulverized? These are the questions to ask.”
