An analysis of misconceptions about thorium-based fuel cycles as a technical fix to the nuclear proliferation problem

This paper analyzes several prevalent misconceptions about nuclear fuel cycles that breed fissile uranium-233 from thorium. Its main conclusions are: a Uranium-233, despite the gamma radioactivity of associated isotopes, is a rather attractive material for making fission bombs, and is a credible material for subnational as well as national groups to use for this purpose. e "Pure" thorium cycles, which in effect merely substitute uranium-233 for plutonium, would take many decades and much uranium to establish, and offer no significant safeguards advantage over plutonium cycles. e "Denatured" thorium-uranium cycles, which dilute the uranium-233 with inert uranium-238 to a level not directly usable in bombs, are not an effective safeguard even against subnational bomb-making. This is because three factors-higher initial fissile content , larger mass difference between isotopes, and smaller amount of material needed fo r a bomb-make such "denatured" uranium-233/238 fuel one or two hundred times easier to enrich to bomb-usable levels than natural uranium. Such enrichment can be done at a modest scale with readily available centrifuges. L