Dissolution of evaporites and its possible impact on the integrity of the Waste Isolation Pilot Plant (WIPP) New Mexico, USA

The radiological consequences of a breach of the WIPP TRU waste repository, as a result of dissolution processes were shown to be in two broad classes. Most of the possible scenarieos that could happen as a result of the deep dissolution processes were shown to be addressed by the scenarios already presented elsewhere or are being investigated at the present. The remaining possible scenarios, except one, showed that the possible release of radionuclides through the geosphere to the biosphere would take periods of time orders-of-magnitude longer than the half-life of Plutonium-239. The one not specifically addressed, a postulated hydralogic pathway with the characteristics of the Salado/Castile interface aquifer, appears unlikely. However, it should be quantified when more data become available. To obtain a better understanding of the radiological health effects of the deep dissolution-caused breach of the repository, emphasis must be placed on better evaluation and refinement of the existing mathematical models and associated parameters. In the majority of the existing scenarios the most significant pathway of the radionuclide through the geosphere to the biosphere is the dolomitic Magenta and Culebra aquifers. Because these formations are fractured, mathematical modeling of radionuclide transport is subject to a large degree of uncertainty. Other uncertainties that relate to this pathway which need further study are: (a) the possibility of having more permeable abandoned mined potash tunnels as a part of the radionuclide flow path and (b) the outcrops of the Magenta and Culebra formations in Nash Draw, 11 km (7 mi) before the outlet to the Pecos River at Malaga Bend. The problems associated with the quantifications of these uncertainties as well as the effects of long-term climatic and hydrologic changes and hydrogeological data requirements of the models should be further addressed