Five days.

That's how long it will take for what is being described as “the largest moveable land-based structure ever built” to slide into place over Chernobyl’s reactor 4, scene of the world’s worst nuclear accident some 30 years ago, in an effort to prevent radiation from leaking out for another 100 years.

The Soviet-era power plant, situated in Ukraine’s northern reaches, close to the border with Belarus, suffered a meltdown and explosion in 1986, since which time the reactor at the heart of the disaster has been encased in a tomb of steel and concrete. But because of persisting levels of radiation, maintenance has been impossible, and building a replacement housing structure on site has been equally inadvisable.

Hence the new shield, christened the New Safe Confinement (NSC), whose construction began in 2010. At 108 meters (354 feet), it is tall enough to house London’s St. Paul’s cathedral or Paris’s Notre Dame. Consisting largely of steel and concrete, like its predecessor, the colossus weighs in at 36,000 tons and cost €1.5 billion ($1.6 billion).

Describing it as “the end of a 30-year long fight with the consequences of the 1986 accident,” Ostap Semerak, Minister of Ecology and Natural Resources of Ukraine, said in a statement that this “one-of-a-kind technological structure” was possible only because of committed international support, with more than 40 countries involved.

Strong enough to withstand a tornado, and boasting an advanced ventilation system, the NSC will allow the reactor to finally be dismantled and the radioactive material to be secured.

The disaster itself sent a plume of radioactive material into the skies, which proceeded to drift over parts of what was then the Soviet Union, as well as areas of northern Europe.

Though the original shielding put in place has contained an estimated 80 percent of the radioactive material originally left after the meltdown, the risk of structural failure increases with each passing year without the possibility of maintenance. Once the NCS has slid into place, with the aid of rail tracks fitted with custom Teflon bearings, the plan is to dismantle the reactor and thereby remove the risk of further radiation leakage when the new shielding does eventually fail, 100 years or more into the future.

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The task of deconstructing the remains of reactor 4 and the original shield will fall to a heavy-duty crane, operated remotely, as well as robotic tools suspended from the roof of the NCS. The risk remains that the high radiation levels may damage this equipment, just as robots entering Japan’s Fukushima nuclear plant, after the 2011 tsunami-induced disaster, were defeated by radioactivity.

Yet, at the very least, the sparkling new structure lumbering into place will buy time. It is, as Claire Corkhill of the University of Sheffield described it in The Conversation, “an enforced lesson in patience.”