Note: This article is a sidebar to one of this issue's feature stories, "The Fourth Wave," in a special issue about the West's resurgent uranium economy.
THE NUCLEAR FUEL CYCLE
MINING AND MILLING
In 1983, mining ceased at Kennecott Energy’s Sweetwater open-pit uranium mine (at right) near Rawlins, Wyo.
Uranium ore from traditional open-pit or underground mines is shipped to a mill to be processed into uranium oxide ("yellowcake"). Radioactive mill tailings threaten public health.
In-situ leach mining of uranium is more economical and safer than traditional mining methods. Miners inject water underground and use chemicals to leach out the ore. The resulting sludge is processed into yellowcake. On an energy-equivalent basis, one pound of yellowcake equals 10 tons of coal or 31 barrels of fuel oil.
The yellowcake is sent to a conversion facility in Illinois, where it’s chemically converted to uranium hexafluoride, or UF6. The UF6 is shipped in steel cylinders to an enrichment plant.
To use uranium as a fuel in nuclear reactors, it must be enriched to increase the amount of uranium-235 isotopes. As a byproduct, the enrichment process creates depleted uranium, an extremely dense and slightly radioactive substance used for armor plate and warheads.
The country’s only operating enrichment plant is in Kentucky; Louisiana Energy Services broke ground on another in Eunice, N.M., in August.
The enriched UF6 is processed into ceramic fuel pellets, which are then loaded into fuel rods and combined into fuel assemblies. An assembly can contain up to 264 fuel rods and is usually 5 to 9 inches square by about 12 feet long. One plant in the West fabricates uranium fuel, Areva NP Inc. in Richland, Wash.; the above photo shows a worker handling the pellets.
The nuclear reactors used to generate electricity in the United States are light water reactors, which use ordinary water ("light water") to control the fissioning (splitting) of uranium atoms. The energy released is harnessed to make steam, which turns the turbines of the electric generators.
Nuclear power plants have produced tens of thousands of tons of both low-level and high-level radioactive waste. Low-level waste includes trash, tools and clothing contaminated with small amounts of radioactive particles. It’s stored in facilities in Washington and Utah.
Spent uranium fuel is high-level radioactive waste. It’s thermally hot and highly radioactive; direct exposure is quickly fatal. Spent fuel takes hundreds of thousands of years to decay and become harmless. It’s currently stored in large water-cooled pools and dry storage casks at nuclear power plants and at the Idaho National Engineering and Environmental Laboratory. The Department of Energy plans to permanently store this waste at Yucca Mountain, now almost 20 years overdue.