The reality is that it's a hypothetical problem. Even the simple real problem of storing spent fuel is not that of a problem, because there's not that much of it. And while it's hot it needs water then moving air anyway.
Long term storage is a nice idea, but in reality it's easy (dump anywhere down enough that it doesn't matter) and the later we solve it the more certain we can be that we did it right (more data, more time spent on finding the right solution).
It doesn't really help with costs, so there's no hurry, and it's a political quagmire. So it just did not happen. (WIPP kind of happened, and is happening, but it's for non-commercial nuclear waste.)
https://en.wikipedia.org/wiki/Onkalo_spent_nuclear_fuel_repo...
