Overview
- The Finnish Radiation and Nuclear Safety Authority (STUK) is scheduled to publish its final assessment in June 2026, a decision that could lead to an operating licence for Onkalo.
- Posiva and operator TVO say major commissioning and encapsulation tests are complete and they expect the first spent‑fuel emplacement in late 2026 or early 2027 if regulators approve.
- Onkalo uses the KBS‑3 multi‑barrier method: fuel sealed in corrosion‑resistant copper canisters, placed in holes in 430‑metre‑deep bedrock, surrounded by bentonite clay, and sealed with concrete plugs.
- Regulators and independent experts continue to flag long‑term uncertainties such as copper corrosion and seismic effects during future ice ages that could threaten canister integrity over millennia.
- Built since 2004 at an estimated cost of about €1 billion with room for roughly 6,500 tonnes of fuel, Onkalo implements Finland’s law requiring domestic disposal and will be watched internationally as a practical test of permanent waste storage.