After three decades of study, TVO and Fortum have completed their application to build a geologic repository for nuclear waste in Finland.

Posiva, which is owned jointly by the two companies, submitted the application Friday, according to a release. It seeks government approval for the facility to eventually dispose of nearly 10,000 tons of spent fuel from Finland's four existing power reactors, plus the Areva EPR unit under construction at Olkiluoto and another reactor planned for that site.

"The construction license application is based on more than 30 years of research and development work, carried out ever since the commissioning of the existing nuclear power plants. The data gathered over the decades has confirmed our views of the safety of geologic disposal," Posiva President Reijo Sundell said in the release.

If approved, the repository will be built at Olkiluoto, about 160 miles northwest of Helsinki. The plans envision a network of tunnels built in stages at a depth of 1,300 feet to 1,500 feet. Its design incorporates corrosion-resistant containers, bentonite clay separating them from the bedrock, and a tunnel backfill system. The facility will also include an above-ground encapsulation plant.