Finland has the world’s first commercial underground nuclear waste repository, and construction of the access works, infrastructure, and the first five disposal tunnels is essentially complete. I haven’t seen a timeline of when they will start accepting nuclear waste but apparently they are waiting for approval from the Finnish Government, but it’s supposed to be sometime this decade. BusinessInsider.com has a fascinating article where the author toured the facility and there are a series of photos and videos so you can really see the various aspects of the facility and the disposal plan. The site is called Onkalo, located adjacent to the Olkiluoto Nuclear plant near the Baltic Sea. The private company that operates it is Posiva. The facility is over 1,300 feet below ground with 31 miles of tunnels.
When the spent fuel is received, it will be encased in an iron container to resist pressure, and an outer copper container to resist corrosion as shown in the video below. A robotic device lowers the canisters into vertical drilled holes in each drift that are pre-lined with bentonite rings. Then additional bentonite is backfilled above the canister, also robotically. After all of the vertical holes in the drift have received their canisters, the drift is sealed with a plug of concrete.
The facility has been in progress for almost 20 years and is said to have an operational life of 100 years at a cost of approximately $3.7 billion US once it is full. The article estimates that Finland is 20 to 30 years ahead of the US and UK since neither country has even selected a site yet.