Uncertainty and sensitivity analysis in performance assessment for the Waste Isolation Pilot Plant

The Waste Isolation Pilot Plant (WIPP) is underdevelopment by the U.S. Depa rtment of Energy (DOE) for the geologic (deep underground) disposal of tran suranic (TRU) waste. This development has been supported by a sequence of p erformance assessments (PAs) carried out by Sandia National Laboratories (S NL) to assess what is known about the WIPP and to provide guidance for futu re DOE research and development activities Uncertainty and sensitivity anal ysis procedures based on Latin hypercube sampling and regression techniques ply a major role in these PAs by providing an assessment of the uncertaint y in important :analysis outcomes and identifying the sources of this uncer tainty. Performance assessments for the WIPP are conceptually and computati onally interesting due to regulatory requirements to assess:and display the effects of both stochastic (i.e., aleatory) and subjective (i.e., epistemi c) uncertainty, where stochastic uncertainty arises from the possible disru ptions that could occur over the 10000 yr regulatory period associated with the WIPP and subjective uncertainty arises from an inability to unambiguou sly characterize the many models and associated parameters required in a PA for the WIPP. The interplay between uncertainty analysis, sensitivity anal ysis, stochastic uncertainty and subjective uncertainty is discussed and il lustrated in the context of a recent PA carried out by SNL to support an ap plication by the DOE to the U.S. Environmental Protection Agency for the ce rtification of the WIPP for the disposal of TRU waste. (C) 1999 Elsevier Sc ience B.V.