How Finland's 100,000-year nuclear tomb taught me to love our lethal radioactive sludge

I am standing 450 metres below the pine forests of Eurajoki, shivering slightly in my custom-tailored parka, running my hand along the raw gneiss walls of the Onkalo spent nuclear fuel repository. The sheer ambition of it catches in my throat. We are about to begin lowering tonnes of highly radioactive copper canisters into this permanent subterranean tomb, designed to remain utterly undisturbed for 100,000 years. It is the first engineered structure meant to outlast modern civilisation, and looking down the tunnel, I am struck by a profound realisation: this is the most beautiful thing humanity has ever built.

When I mentioned this over a plate of smoked reindeer last night to the head of a prestigious MIT geophysics lab, she seemed hesitant to embrace my vision. We were in town for an exclusive preview of the facility, just the two of us and a few energy ministers, and she kept using words like containment and lethal radiological hazard. But scientists are often too close to their own equations to see the poetry. They see a desperate, billion-euro scramble to hide the deadly detritus of our energy consumption from the water table. I see a time capsule.

The craftsmanship alone is breathtaking. Each cast-iron insert is wrapped in pure copper, welded shut with a precision that rivals the mirrors on the James Webb Space Telescope, and then swaddled in bentonite clay that expands as groundwater trickles in. It is a geological hug for our most toxic blunders. When I discussed this structural elegance during a panel I hosted at Davos last year, the sheer ingenuity of it brought a tear to my eye. We are taking the most hostile, biologically incompatible substance on Earth and tucking it into bed for a hundred millennia.

Think of the pyramids of Giza. Think of Stonehenge. Our ancestors left us monuments of stone to say that they were here. We are leaving our descendants a perfectly sealed labyrinth of irradiated uranium 235 that will instantly liquefy their internal organs if they ever figure out how to open it. In a very real sense, we are gifting the distant future a puzzle box, wrapped in lead, nestled in bedrock. We are reaching across the eons to the post-human inhabitants of Earth, trusting them with the ultimate cosmic riddle: how to ignore a glowing rock.

The engineers at Posiva, the company managing Onkalo, are focused entirely on the mundane mechanics of keeping the biosphere safe from our glowing garbage. But even they occasionally let slip the deep spiritual resonance of their work, provided you listen closely enough to what they aren't saying.

Jukka's modesty is touching, but it misses the grandeur of the human project. Critics of nuclear power often point to the unsolvable waste problem, framing the production of centuries-lethal sludge as some sort of moral failure. This is such a small, pessimistic way to look at the universe. If we never produced anything that required a 100,000-year burial, we would never be forced to build a 100,000-year tomb. By generating catastrophic amounts of toxic waste, we have forced ourselves to become architects of deep time. We are stretching the human imagination by giving ourselves no other choice but to dig.

As I took the industrial elevator back up to the surface, leaving the silent, deadly copper pillars behind in the dark, I felt a deep sense of peace. We are a flawed species, yes. We split the atom, we boiled the oceans, and we created byproducts so hostile to biological life that we must bury them deeper than the fossil record. But we also cared enough to put a really nice manhole cover over it. That, to me, is the essence of wonder.