Finland’s Underground Nuclear Vault Targets Centuries of Containment

Finland is preparing to activate Onkalo, a 430‑meter‑deep underground repository carved into ancient bedrock to store about 6,500 tonnes of spent nuclear fuel. Projected to operate into the 2120s and then be sealed, it reflects a landmark approach to permanent domestic disposal—unmatched globally so far. While engineered to keep waste isolated for millennia, uncertainties remain, notably copper canister corrosion and how future generations will understand the hazard, prompting ideas like durable warnings through nuclear semiotics.