Traveling wave reactor...

TerraPower is a technology company headquartered in Washington, United States that does research on traveling wave reactors (TWRs). Its principal owner is Bill Gates. Although light water reactors such as PWRs or BWRs running worldwide use enriched uranium as fuel and need fuel handling every a few years, TWRs use depleted uranium instead and are considered to be able to operate continuously for 100 years without fuel handlings. TWRs TerraPower is currently reserching is considered to generate 100,000~1,000,000 kilo-watts.

Papers and presentations on the TerraPower TWR describe a pool-type reactor cooled by liquid sodium. The reactor is fueled primarily by depleted uranium, but requires a small amount of enriched uranium or other fissile fuel to initiate fission. Some of the fast-spectrum neutrons produced by fission are absorbed by neutron capture in adjacent fertile fuel (i.e. the non-fissile depleted uranium), converting it into plutonium by the nuclear reaction:


Initially, the core is charged with fertile material. A small amount of fissile fuel is added to one end of the core. Once the reactor is started, four zones form in the core: the depleted zone, which contains mostly fission products and leftover fuel; the fission zone, where fission of bred fuel takes place; the breeding zone, where fissile material is created by neutron capture; and the fresh zone, which contains unreacted fertile material. The energy-generating fission zone advances through the core over time, effectively consuming fertile material in front of it and leaving spent fuel behind. Heat from fission is converted into electricity using conventional steam turbines.