We could also drop it to the bottom of the ocean, as we did for decades. Any spillage will dilute heavily (there's already plenty of radioisotopes in seawater),

We could also drop it to the bottom of the ocean, as we did for decades. Any spillage will dilute heavily (there's already plenty of radioisotopes in seawater), and it will take quite a while until geological processes get the bottom of the ocean to surface. Of course, we don't do that anymore, because it's stupid: nuclear waste is too valuable to just dispose of it like that.