Publications Details

Comparison of two risk assessment methodologies for high-level waste disposal in unsaturated media

Davis, P.A.; Gallegos, D.P.; Hake, T.M.; Olague, N.E.; Price, L.L.; Piepho, M.G.; Goodrich, M.T.; Lee, C.E.

The US Department of Energy (DOE) is responsible for designing, obtaining a license for, and constructing a geologic repository for the disposal of commercial high-level radioactive waste. The candidate repository site is currently at Yucca Mountain in Nevada. Part of DOE`s responsibility is to assess compliance with the appropriate environmental regulations, including the Environmental Protection Agency`s containment requirements in 40 CFR Part 191. Sandia National Laboratories (SNL) and Pacific Northwest Laboratories (PNL) have been contracted to aid DOE in the assessment of total systems performance. SNL has been tasked with evaluating and comparing the performance assessment methodologies developed by PNL and SNL, as applied to one conceptual model. In this report, SNL has attempted to reproduce, by way of a benchmark exercise, the results of PNL`s preliminary risk assessment of the proposed repository at Yucca Mountain. In general, the results of the PNL analysis and the SNL benchmark of that analysis agreed quite well, in terms of both ground-water flow and transport of unretarded radionuclides. The largest discrepancy between the analyses was noted for transport of retarded radionuclides, and was the result of different techniques for calculating retardation factors. 27 refs., 28 figs., 17 tabs.