An Integrated Approach Toward Characterization of Radionuclide Transport at Yucca Mountain, Nevada

A major effort of site characterization activities at Yucca Mountain, Nevada, a site being studied by the U.S. Department of Energy (DOE) as a potential repository of high-level radioactive waste, is directed toward understanding the efficacy of the natural barrier to isolate waste. Characterization of potential aqueous radionuclide migration from waste containers to the accessible environment, a distance of 5 km, is a key step in that determination because of regulations which stipulate that the site must be able to isolate waste for 10,000 years. The Yucca Mountain Site Characterization Project (YMP) has an integrated radionuclide migration program that combines investigations to characterize processes that affect radionuclide transport, including solubility, speciation, sorption, diffusion, and dispersion, and studies to investigate aspects of the natural system affecting those processes, such as mineralogy, mineral stability, and water chemistry. The program also includes studies to understand the behavior of the natural system under disturbed conditions of the thermal pulse, which would potentially alter the chemistry of both heated water and rock hundreds of meters away from the potential repository. This paper focuses on the integration of results from numerous geochemical investigations into models for understanding transport processes.