Here's one option, which has been seen as viable solution for long term storage. https://en.wikipedia.org/wiki/Onkalo_spent_nuclear_fuel_repository https://en.

Here's one option, which has been seen as viable solution for long term storage. https://en.wikipedia.org/wiki/Onkalo_spent_nuclear_fuel_repository https://en.wikipedia.org/wiki/Onkalo_spent_nuclear_fuel_repo...