New York Times BELLEVUE (WASHINGTON): In a drab one-storey building here, set between an indoor tennis club and a home appliance showroom, dozens of engineers, physicists and nuclear experts are chasing a radical dream of Bill Gates. The quest is for a new kind of nuclear reactor that would be fuelled by today's nuclear waste, supply all the electricity in the US for the next 800 years and, possibly, cut the risk of nuclear weapons proliferation around the world. The people developing the reactor work for a start-up, TerraPower, led by Bill Gates and a fellow Microsoft billionaire, Nathan Myhrvold. So far, it has raised tens of millions of dollars for the project, but building a prototype reactor could cost $5 billion â€” a reason Gates is looking for a home for the demonstration plant in rich and energy-hungry China. "The hope is that we'll find a country, with China being the most likely, that would be able to build the demo plant," Gates said last year to energy expert Daniel Yergin. "If that happens, then the economics of this are better than the plants we have today." Today's nuclear reactors run on concentrations of 3 to 5% uranium 235, an enriched fuel that leaves behind a pure, mostly natural waste, uranium 238. In today's reactors, some uranium 238 is converted to plutonium that is used as a small, supplemental fuel, but most of the plutonium is left behind as waste. In contrast, the TerraPower reactor makes more plutonium from the uranium 238 for use as fuel, and so would run almost entirely on uranium 238. It would need only a small amount of uranium 235, which would act like lighter fluid getting a charcoal barbecue started. The result, TerraPower's supporters hope, is that countries would not need to enrich uranium in the quantities they do now, undercutting arguments that they have to have vast stores on hand for a civilian programme. TerraPower's concept would also blunt the logic behind a second route to a bomb: recovering plutonium from spent reactor fuel, which is how most nuclear weapons are built. Since so much uranium 238 is available, there would be no reason to use that plutonium, TerraPower says. But no one disputes that this is a long-term bet. Even optimists say it would take until 2030 to commercialize the technology.