90,000 metric tonnes in the US of high-level waste (incredibly low given that it's produced ~20% of our electricity carbon free for 40 years). You'd have to also launch a bunch of heavy shielding with that just for handling purposes, so be conservative and multiply by 10.

You'd need a really reliable launch process like a space elevator to do this without worrying about dispersing it around in the atmosphere. It's worth talking about but it's hard to imagine a socially-acceptable pathway at the moment. Deep geologic repositories are safe and known. We should just use them.