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The nuclear waste repository in Finland designed to outlast modern civilisation – how exactly have the engineers future-proofed their facility?

The first engineered structure built to last for 100,000 years is about to begin operations. The hope is that Onkalo, deep below ground in Finland, will offer a safe place for the country to store nuclear waste?

By George Bass and Jacklin Kwan,, New Scientist 3rd Nov 2026

There’s a timeless quality to the tunnels at Onkalo. And that’s the point. Carved into the rock more than 400 metres below ground, these passageways are part of a facility built for the long term. The extreme long term.

In fact, facilities such as Onkalo “should exist intact for at least 100,000, if not a million years”, says Allison Macfarlane at the University of British Columbia in Canada, who previously served as chair of the Nuclear Regulatory Commission in the US. “Those are geologic timescales.”

Onkalo is Finland’s answer to one of the more tricky questions posed by nuclear power: what do you do with the waste? We are going to have to get much better at answering it, given nuclear power is expanding again, driven partly by the hunt for low-carbon energy.

There’s broad consensus that burying the waste is the best option. But there is a catch. Radioactive elements can remain dangerous on timescales that make normal engineering look absurdly short-term. Egypt’s Great Pyramid of Giza is around 4500 years old. Some nuclear repositories will have to contain their contents for more than 20 times longer. Before the waste becomes harmless, civilisations may rise and fall, and ice sheets may come and go.

An earlier attempt to store waste on geological timescales failed spectacularly after just a few decades. The engineers at Onkalo, and at a handful of similar sites now being planned or built around the world, think they can do much better. So, as Onkalo prepares to accept its first waste shipments in the coming months, how exactly have the engineers future-proofed their facility?………………………………………. (Subscribers only) https://www.newscientist.com/article/2595321-the-nuclear-repository-in-finland-designed-to-outlast-modern-civilisation/

November 9, 2026 - Posted by Christina Macpherson | Finland, wastes