Survey and review of near-field performance assessment

The rate of radionuclide transport relative to that of the bulk groundwater is discussed. This includes interactions with both near-field engineered materials and far-field host rock. These retardation interactions are complex, and depend on the chemistry of the solute and the rock phase, as well as the hydrologic characteristics of the system. Retardation mechanisms considered in evaluating radionuclide migration from geologic repositories include diffusion into dead-end pore spaces, ion exclusion, filtration, precipitation and sorption. (R.P.) 2 figs