"worker safety much less of a concern but the danger was also less well understood"

Another important point is to people who don't understand the physics, something not understood "must" be feared, therefore the most dangerous part must have been the physics. However I understand at least some of the chemistry and industrial processes using bulk hydrofluoric scare me more than the physics. Aside from the mechanical / explosive hazards, of course (machine plastic explosives to precise shapes on a milling machine for the implosion weapons, are you insane? You're hooking up a zillion blasting caps to .. what?)