A couple of questions in the context of constructing nuclear weapons: Would it be feasible to refine uranium nanotechnologically? It seems to me that a large number of nano-scale robots or other machines could directly, mechanically sort the atoms of uranium ore (or any other source) - the way that macro-scale machinery sorts postal mail, for example - to produce enriched uranium. Does this seem like something that could become possible within the next century? I ask because I would think that nanotechnology and other technological developments will continuously lower the industrial barriers to producing nukes. I'm wondering if at some point it simply won't be possible to prevent most nations from becoming nuclear-armed.