Methods and data for predicting nuclide migration in geologic media

Methods developed to predict nuclide migration from geologic isolation repositories should groundwater invade the disposal site have culminated in a geosphere transport model, applicable to both particulate and faulted monolithic media with barriers to migration-containment, leach resistance, and nuclide retention. The geosphere model has been combined with a biosphere model to produce an integrated computation of nuclide transport from the respository to man. The geosphere transport model requires data on sorption for the geologic medium under investigation. To date, all sorption measurements have been made on surface or near-surface soils and rocks, and no sorption measurements have been made on deep geologic media. The applicability of surface and near-surface sorption data to deep geologic disposal has not been assessed. However, the application of near-surface data to geologic isolation under a desert in the western United States has been evaluated, and these data were modified and used to examine the incentives for partitioning nuclear wastes. To date, most sorption measurements have been made in the laboratory. However, it may become practical or necessary to augment or replace the laboratory measurements by in situ measurements. Present methods of measuring sorption may be inadequate for application to geologic isolation, and these uncertainties need to be resolved