Finland's government issued an operating licence for the planet's inaugural permanent repository for radioactive spent nuclear fuel, Posiva announced on Thursday, 22 years after construction began.
Located in Eurajoki in southwestern Finland, the repository is blasted into 1.9 billion-year-old stable bedrock and will keep spent fuel in drilled holes where it stays highly radioactive for millennia.
"This is a great and historic day for both Posiva and Finland," said Posiva chief executive Ilkka Poikolainen in a statement.
The facility, named Onkalo - Finnish for "cave" - is expected to start operating soon, though Posiva has not set a precise date.
Prior to beginning final disposal, Posiva will complete the commissioning phase, performing required tests and inspections that must also be validated and approved by the Finnish Radiation and Nuclear Safety Authority (STUK).
Onkalo can accommodate 6,500 tonnes of uranium, providing permanent storage for spent fuel from Finland's five nuclear reactors.
Fuel will be sealed in corrosion-resistant copper canisters, lowered into tunnels drilled into the rock, surrounded by bentonite clay, and finally capped with a steel-reinforced concrete plug.
According to Posiva, the material will stay highly radioactive for tens of thousands of years and after roughly 100,000 years its radioactivity will match that of the original uranium ore.
Since the 1950s, nations have struggled with disposal of hazardous nuclear by-products, most of which remains in temporary storage.
While neighboring Sweden and France are constructing final repositories, Finland is expected to be the first to open an underground storage site.
The estimated cost of the Onkalo project is $1.16 billion.
