> In all of those cases, you need to have enough shielding to avoid spreading nuclear waste over a very large area -- that adds a lot of mass.

Conservatively it might add an order of magnitude, and likely less. This still renders future reusable launchers much cheaper per kg of spent fuel than reprocessing would be, unless you are projecting very large improvements in the cost of reprocessing.

You might object current launchers aren't cheap enough, but I wasn't proposing doing this right now with current launchers, so that would be a strawman objection.