Finland’s Onkalo repository at Olkiluoto is the world’s first operational deep geological repository for spent nuclear fuel (operations began approximately 2025). It uses the same KBS-3 concept as Sweden:
- Located at approximately 400—450 metres depth in crystalline bedrock
- Spent fuel encapsulated in copper canisters with cast iron inserts
- Bentonite clay buffer surrounding canisters
- Operated by Posiva Oy