writes "Thorium has attracted interest as a potentially safer fuel for nuclear power generation. In part, this has been because of the absence of a route to nuclear weapons, but a group of British scientists have identified a path that leads to uranium-233 via protactinium-233 from irradiated thorium. The protactinium separation could possibly be done with standard lab equipment, which would allow it to be done covertly, and deliver the minimum of U233 required for a weapon in less than a year.
The full article is in Nature, paywalled."Link to Original Source