No reason to launch anything significantly radioactive. It's the waste you have to worry about, the fission fuel itself is (comparatively) safe. It has to be, if it were seriously radioactive it wouldn't still exist after almost 5 billion years in the ground.

Still not exactly *safe*, but so long as you stay well away from critical mass the heavy metal poisoning will probably do more damage than the radiation.

And I think I recall hearing that NASA is moving strongly away from using legacy pre-physics units for anything, in large part because it opens the door to stupid conversion errors like that, and someone inevitably walks through.