Thorium power has a protactinium problem. In 1980, the International Atomic Energy Agency (IAEA) observed that protactinium, a chemical element generated in thorium reactors, could be separated and allowed to decay to isotopically pure uranium 233—suitable material for making nuclear weapons. The IAEA report, titled “Advanced Fuel Cycle and Reactor Concepts,” concluded that the proliferation resistance of thorium fuel cycles “would be equivalent to” the uranium/plutonium fuel cycles of conventional civilian nuclear reactors, assuming both included spent fuel reprocessing to isolate fissile material.
Bulletin of Atomic Scientists 6th Aug 2018 read more »