Unfortunately, it's very possible. Separate out the Pa233 (can be done chemically), wait for it to decay, and you have pure U233 usable for a bomb. Particularly

Unfortunately, it's very possible. Separate out the Pa233 (can be done chemically), wait for it to decay, and you have pure U233 usable for a bomb. Particularly easy if you have a reactor allowing you to siphon out Pa233 while the thing is running, such as a molten salt reactor. All in all, is this easier than going the traditional path of natural U + graphite piles to produce weapons grade Pu? Perhaps not, considering apparently all actual nuclear weapon states have gone the U-Pu way. But nothing to dismiss out of hand either.