Seven years ago, on the afternoon of March 11, 2011, one of the biggest earthquakes ever measured sent a wall of water rolling toward Japan’s northeastern coastline and into the six reactors of the Fukushima nuclear power plant.

In the seven years since, the name of the plant has become synonymous with Chernobyl for connoting disaster, radioactive contamination, massive human migration and other calamities of biblical proportion – a name that requires no further description to understand the scale of the disaster it connotes.

It’s become another point on the compass at which the world can contemplate its own end – a catastrophe that still casts more shadows than light, continues to beg confounding questions, and which will continue to press the limits of understanding for decades to come.

On Sunday, Japan marked the anniversary with a nationwide moment of silence at 2:46 pm, the moment when, on that Friday in 2011, the waters breached the Fukushima plant and triggered a triple nuclear meltdown.

In the days that followed the quake, uranium fuel melted down inside three of the six reactors. Hydrogen explosions burst through the roofs of three of the reactor buildings, sending radioactive iodine, cesium and other fission by-products belching into the environment. Millions of liters of water were pumped from the ocean to cool the overheating reactors, cascading contamination into the sea.

A clock, found in debris on a beach in Fukushima, stopped at the exact time the March 11, 2011 tsunami hit. Photo: - Credit: Nils Bøhmer/Bellona

The meltdowns forced the evacuation of 160,000 people from the rural and agrarian prefecture, 73,000 of whom have yet to come anywhere near home again. Food and livestock were poisoned. In the aftermath, Japan shut down its 42 remaining nuclear reactors, only three of which have come back online under the country’s stringent new safety codes, which were rewritten nearly from scratch in the disaster’s aftermath, severing a source of 30 percent of Japan’s power.

Seven years on, troubling questions about the plant’s condition remain, and addressing them will mean decontaminating an area almost as big as Hawaii without unleashing yet more radiation into the environment.

As this year’s anniversary approached, Tokyo Electric Power Co, or Tepco, which owns the plant, reported that that the reactors at Fukushima are now stable, but many are having trouble believing that. Since the beginning of the disaster, Tepco delayed and obfuscated reports on the state the plant, costing critical evacuation days, and the company is now struggling to overcome a lack of public trust as it forges forth in the cleanup. And while Tepco

The sheer vastness of the cleanup operation seems nearly impossible to bring to heel. At the plant alone, it’s estimated to take another 50 years before decontamination and clean up is complete. Tepco, estimates it will finish the job by 2050. Others in the government admit the cleanup could go on far beyond that.

Decontamination workers returning from the Fukushima plant, March 2013. Credit: Nils Bøhmer

Meanwhile the extent of the toll on human health remains unknown. Of the 20,000 workers who were exposed to radiation in the immediate aftermath of the catastrophe, only about 7,000 have received any sort of ongoing health testing and observation.

And people are reluctant to return to homes that fell within the evacuation zone. Japanese broadcasters report that some 70,000 continue to live in government supported evacuation housing, leery of retiring to areas where radiation levels are only debatably safe.

While the Japanese government said last year that decontamination costs would reach $75.7 billion, think tanks in Japan have said the final bill could be more than eight times that – closer to $470 billion to $660 billion, according to Japan’s Center for Economic Research,

Whatever the amount,  Japan is paying for daring engineering to handle thousands of damaged and melted nuclear fuel rods and tons of mangled reactor debris.

Tanks of contaminated water at Fukushima, Credit: Tepco

One of the main problems is what to do with millions of tons of water, which is coursing through the reactors to keep them cool. This water, once contaminated, collects in tanks Tepco has built at the site to hold it. There are 1,000 of these tanks, but the volume of irradiated water they have to handle grows by 100 tons daily.

What will become of that water, Tepco has not yet decided, and efforts to clean it of radioactive isotopes have been only partially successful. While Tepco says it can scrub it of cesium, strontium and 50 other radionuclides, its can’t remove its tritium, a radioactive isotope of hydrogen.

Other issues are posed by rain water seeping into the ground at the stricken plant. It is feared this water could drain contamination into the sea, and Tepco last year built a wall of frozen soil to contain it. But this year they reported it wasn’t working as hoped, and that because of this failure, some 500 tons of water is being contaminated daily at the site.

Tsunami swept houses on Japan's Northeast coast. Photo: - Credit: Nils Bøhmer/Bellona

Yet the biggest challenges remain with the stricken reactors themselves.
During the disaster, uranium fuel overheated and dripped through the bottoms of the No 1, 2 and 3 reactors, forming molten pockets beneath them. Radiation levels inside the reactors are searing.  Inside reactor No 2, for instance, levels still reach reach 7 to 42 sieverts per hour – enough to kill humans after just a short period of exposure. Only robots can reach the fuel.

The robots are trying to map the location of the melted fuel, sending out 3-D imaging allowing workers to discern the location of pebbly deposits thought to be molten uranium. Yet even when the fuel is found, operations to remove it won’t come before 2021 – when engineers will devise a way to get out.

When that begins, it will add to the 200,000 tons of nuclear waste that is in in storage at the disaster site. Japan has not yet agreed on where all of this will finally be buried, and popular resistance to hosting the waste fuels that uncertainty.

While Tepco did manage to remove all 1,533 fuel bundles from the plant’s unit No. 4 reactor before December 2014, it still has to do the same for the hundreds of rods stored at the other three units.

This will mean clearing rubble, installing shields, dismantling the building roofs, and setting up platforms equipment to remove the rods. In February a 55-ton dome roof was installed on unit No. 3 to facilitate the safe removal of the 533 fuel bundles that remain in a storage pool there.  And while removal of fuel at reactor No 3 may being before April of 2019, the fuel at units No. 1 and 2 will not be ready for transfer before 2023.

What Fukushima may look like decades from now, Tepco will not venture to guess. In some reports, the company is quick to say it won’t go the same route as Chernobyl, where an enormous containment structure now covers the remains of its exploded No. 4 reactor. But the road to totally rehabilitating Fukushima, and making it inhabitable again, still appears to be longer than anyone might have guessed.