Hydrothermal ore deposit and geothermal analogs of nuclear waste repositories

Hydrothermal ore deposits and active geothermal systems can provide important information on the response of a rock/ground water system to the emplacement of hot, radioactive nuclear waste. Congress has mandated that the first deep geologic repository be licensed by 1998, so that scientific investigation must be completed in a relatively short time. Laboratory studies are sometimes too short and on too small a scale to adequately simulate the geologic environment over thousands of years. Computer models are often highly simplified. Fortunately, data from the field of economic geology can help scientist anticipate future nuclear waste repository behaviors in a complex environment over long periods of time. Some phenomena in ore deposits are direct parallels to possible repository phenomena. Some ore and gangue minerals show colloidal textures, indicating that colloids may contribute to radionuclide redistribution in a repository. Wall rock alteration in ore deposits indicates the types of alteration to be expected in a repository. In addition to individual analogous phenomena, hydrothermal convection may develop in the ground water after emplacement of waste. Primary dispersion halos, paragenetic relationships, and fluid inclusion data from ore deposits can help to predict the size, shape, and duration of convection cells which might be expectedmore » around a repository. Such studies might also identify the significant effects of complex coupling between thermal, hydrological, chemical, and mechanical factors.« less