Abstract

High-level radioactive wastes, spent nuclear fuel, and transuranic wastes have been accumulating at nuclear power plants and military installations for over 40 years. Safe, permanent storage of these wastes is needed for as long as the radioactive elements present a significant hazard. Since the 1950s, the recommended disposal method for radioactive waste has been deep burial in an acceptable geologic medium. Until the 1980s, the preferred host rock was salt. (National Academy of Sciences, 1957; 1970) In 1983, sites in five geohydrologic regions (in Utah, Louisiana, Mississippi, Nevada, Texas, and Washington) were identified by the Department of Energy as potentially acceptable for a high-level nuclear waste repository. The proposed host rock environments included bedded salt, dome salt, tuff, and basalt. In 1987, the tuff site in Nevada was selected by Congress for site characterization. To be effective in containing waste a repository system needs multiple, independent barriers consisting of engineered barriers and natural, geologic barriers, with primary reliance placed on the geologic barriers.