Answer: Finland
Notes: Finland has built the world’s first permanent deep geological repository for nuclear waste at Olkiluoto. The facility, called Onkalo repository, is located about 400–450 metres underground in stable bedrock. It is designed to safely store highly radioactive spent nuclear fuel for tens of thousands of years. The system uses a multi-barrier approach: waste sealed in metal canisters, enclosed in copper capsules, surrounded by bentonite clay, and embedded in rock. The deep underground location protects it from environmental risks and human interference.
