http://www.intellectualventures.com/docs/terrappower/IV_Introducing TWR_3_6_09.pdf The Future of Nuclear Energy Intellectual Ventures has launched an effort to design nuclear energy reactors that improve on those in operation today. Known as TerraPower, the project has produced preliminary designs for a new class of nuclear reactor, called a Traveling-Wave Reactor (TWR). The TWR can run for 50 to 100 years without refueling or removing any used fuel from the reactor. By greatly simplifying the nuclear fuel cycle, TWRs could improve the cost, safety, social acceptability, and long-term sustainability of nuclear energy as a source of emissions-free electricity. The Science Nuclear power plants produce electricity from the heat generated when big and unstable atoms, such as plutonium and the rare form of uraniumcalled U-235, split apart into smaller atoms. Each time a big atom splits (or “fissions”), it releases fast-moving neutrons and other subatomic particles that leads to a chain reaction. A nuclear reactor produces and controls the release of energy from splitting atoms of certain elements. Nuclear electricity plants today use fuel made from natural uranium that has been enriched. The TWR, in contrast, initially contains only a small igniter of fissile fuel, which is used to kick off the chain reaction. The wave of fission would move slowly through the core, splitting many more of the fuel atoms than a conventional reactor would.A TWR reactor core would be filled with fuel that is made out of atoms that are big but not unstable enough to cause a chain reaction on their own. The fuel could be depleted uranium, for example, which is the common U-238 form of the element that is currently set aside as waste when U-235 is taken out of natural uranium at enrichment plants. A Simpler, Safer Fuel Cycle Unlike light water reactors, the TWR can theoretically run forever without ever needing any additional enriched uranium after its startup period. This fleet could supply the world’s needs for energy for thousands of years without any need for chemical reprocessing of the used fuel. This ability is a major advance in reducing the inherent risks of weapons material proliferation. Many Shapes and Sizes TerraPower’s scientists and engineers are investigating a wide range of designs for TWRs. Small, modular units that generate 100 megawatts of electricity may be feasible and could fit the needs of emerging markets. Conceptual designs for gigawatt-scale reactors, big enough to power a city and similar in outward appearance to existing plants, are well underway. And TerraPower is studying and simulating many other varieties. At Intellectual Ventures, the process of invention continues every day.