As far as producing materials that could be stolen and used for nuclear weapons manufacture, that at least is a little bit better with a Thorium fuel cycle. Presumably the U-233 would simply be left to burn up in the reactor, rather than being separated out and kept in storage. If someone happened to obtain some used fuel they could potentially separate out the U-233 and use it to make weapons, although it would require substantial engineering. Also, since U-233 is very much more radioactive than U-235 or Pu-239 it requires handling with remote manipulators. Any organization that had the ability to separate U-233, engineer the appropriate modified bomb design, then process and machine the U-233 using only remote manipulation is extremely likely to have a sufficient level of technology and industry to build reactors or separators on their own (meaning, able to build nuclear weapons independent of having access to used Thorium fuel).