I would say that the good answer is "mox" (not sure of its english name, but it is likely similar. Used uranium is extremly dangerous for a very long time (millions of years). Yet it could be recycled and used again, and the result would be extremly dangerous for about 500 years (which is still far too much, but less crazily impossible to manage).

We already have enough used uranium to cover the next 200 years of needs, at least... And so it would be a lesser harm for future generation if we use mox than new uranium...

(But the true answer is we need new bombs, so new uranium...)