Accelerator-driven sub-critical reactor

An accelerator-driven subcritical reactor is a nuclear reactor design formed by coupling a substantially subcritical nuclear reactor core with a high-energy proton accelerator. It would use thorium as a fuel, which is more abundant than the uranium and plutonium in the Earth's crust. The extra neutrons needed for achieving criticality would be provided by an external source – a particle accelerator. One benefit of such reactors is the relatively short life of its waste products, which would be in the hundreds of years as opposed to millions of years for existing nuclear reactors. The high energy proton beam impacts a molten lead target inside the core, chipping or “spallating” neutrons from the lead nuclei. These spallation neutrons convert fertile thorium to fissile uranium-233 and drive the fission reaction in the uranium.