Finland’s deep nuclear waste vault in 1.9 billion-year-old bedrock nears launch

Finland's Onkalo repository is nearing approval as the world's first permanent underground spent fuel site.

The facility was built more than 400 meters underground in 1.9 billion-year-old bedrock.

Spent fuel will be sealed in copper canisters, packed with bentonite clay, and buried in tunnels.

Posiva estimates the site can hold up to 6,500 tons of spent fuel for up to 100,000 years.

Engineers chose the site for low seismic activity and long-term radiation containment, and the tunnels will be sealed permanently once filled.