OLKILUOTO ISLAND, Finland From the outside, it looks like any other modern Nordic building rising several stories from a cleared swath of pine forest on this quiet, rural island off this countrys verdant southwest coast.

But inside, hard-hatted workers are busy completing a feat of engineering that has never existed. It involves a robotic system and a basement network of switchbacking tunnels carved more than 1,300 feet into the Earths crust. Once finished, the project, called Onkalo, will turn the page to a new chapter of nuclear energys turbulent 80-year story and make history for the power plant just a two-minute drive down the road.

In a matter of months, the machines inside this boxy gray building will begin a weekly routine that will continue for a century: placing highly radioactive gray cuboid rods into copper cylinders the length of a Lincoln Town Car. From there, the canisters will travel roughly two hours underground to crypts meant to keep the spent-fuel rods undisturbed for millennia in bedrock that geologists say hasnt shifted in almost 2 billion years. Sealed twice over in bentonite clay which expands when wet, preventing water from seeping in and corroding the capsules, and offers stability in case of an earthquake this site is meant to entomb nuclear waste for as close to eternity as any human endeavor can guarantee.

The project will store waste from the decades-old nuclear power complex next door. Last month, Finland switched on Olkiluoto-3, the third and biggest generator at the power station here. The reactor, one of the largest ever built and the first to open in Western Europe in at least 15 years, will produce about 14% of Finlands electricity. Combined with the plants other two reactors, this speck of an island will provide 36% of the countrys power.

On its own, the new reactor would be notable as a rare bullish bet on atomic power at a time when, despite the worlds attempts to slash climate-changing emissions and wean Europe off the fossil fuels financing Russias war machine, more countries have closed nuclear plants than have opened new ones. But Onkalo makes this the worlds first nuclear power plant that solves the problem of the toxic waste that has for years rendered humanitys most reliable and efficient energy source politically radioactive across much of the globe.