Finland spent over $1 billion to build an underground bunker 1,500 feet deep inside the bedrock of an island in order to store nuclear waste for the next 100,000 years.
The bunker is named Onkalo. Here’s how it works.
The bunker consists a series of storage tunnels off-shooting from a few main tunnels like the teeth of a comb. Each storage tunnel has a series of individual pits cut into the granite bedrock.
Each pit is lined with bentonite clay which will absorb any water that makes it through the surrounding granite over the millennia.
Spent nuclear fuel rods are placed into a cast iron canister which gets sealed into a 2-inch thick corrosion-resistant copper cask and then lowered into the bentonite tomb.
As the storage pits are used, the tunnels to access them are gradually backfilled with more bentonite clay and rock. Once Onkalo has been filled to capacity (which is estimated to be in about 100-200 years), the site will be completely backfilled and sealed off forever.
Operating and then monitoring the waste site is going to provide some pretty long-term revenue for the company that built the bunker, Posiva Solutions. Although, by the time 100,000 years is up, the Earth will probably have passed into another ice age, wiping Finland off the map by covering the entire country with over a mile of ice. That’s what “geologic time” means.
References
[1] BBC: Finland’s plan to bury spent nuclear fuel for 100,000 years