re: Storage
In my opinion, the ideal storage site for fully processed waste should be such that if it is forgotten about by the authorities, of if the authorities collapse, the material will likely remain safely hidden and out of site. OTOH, it should also be located so if the authorities change their minds about how it is stored, it can be quickly retrieved.
Deep, abandoned mines in geologically stable areas with no ground water seem the ideal place. If civilization collapses, we won't have any way of finding or retrieving it. But if we suddenly should learn, for any reason, that it is not a good place for it, then we would be able to move it.