Some results from the second iteration of total-system performance assessment for Yucca Mountain

The second preliminary total-system performance assessment for the potential radioactive-waste-repository site at Yucca Mountain has recently been completed. This paper summarizes results for nominal aqueous and gaseous releases using the composite-porosity flow model. The results are found to be sensitive to the type of unsaturated-zone flow, to percolation flux and climate change, to saturated-zone dilution, to container-wetting processes and container-corrosion processes, to fuel-matrix alteration rate and radionuclide solubilities (especially for 237Np), and to bulk permeability and retardation of gases 14C. There are areas that should be given priority in the site-characterization program. Specific recommendations are given in the full report of the study