OVERVIEW OF THE YUCCA MOUNTAIN SCIENTIFIC INVESTIGATION PROGRAM

More than thirty years of effort and billions of dollars were invested in the scientific investigations to determine if a high-level nuclear waste disposal facility could be constructed and operated at Yucca Mountain, Nye County, Nevada, with an acceptable level of confidence that the combined system of natural and man-made barriers would safely perform over an unprecedented regulatory performance period. Topics of investigation spanned most of the breadth of earth science and geotechnical fields. Some studies were narrowly focused on specific regulatory issues, while other studies were intended to develop information regarding overall system performance over time. Critical questions addressed early on included: (1) what’s important; and (2) how much is enough. Key to answering these questions was a hierarchy of models, starting with detailed process-level models and culminating in a time-dependent top-level model, which incorporated all important performance elements of the natural and man-made systems. Explicit and complete treatment of uncertainty allowed decisions to be regarding “how much is enough”. Similarly, sensitivity studies allowed decisions to be made regarding “what’s important”. Where necessary, field and laboratory investigations were complemented by expert elicitations to provide estimates of sub-system parameters over millennia. All of this work was conducted under a rigorous quality assurance program, and exhaustively documented.