Finland's Onkalo nuclear repository, blasted 433 meters below ground into 1.9 billion-year-old bedrock, is nearly ready to become the world's first permanent repository for radioactive spent nuclear fuel.

The Onkalo repository in Eurajoki, southwestern Finland, is a geological repository for spent nuclear waste located 433 meters below ground, carved into stable bedrock that is 1.9 billion years old. The name Onkalo means 'cave' in Finnish.

Most radioactive spent nuclear fuel from nuclear plants built since the 1950s has been held in temporary storage; Onkalo is expected to be the world's first permanent repository for this dangerous nuclear by-product.

The repository is nearly ready to start operations, according to Philippe Bordarier, chief executive of nuclear operator Teollisuuden Voima Oyj (TVO).