Site characterization at Yucca Mountain

The Yucca Mountain site, located in south-central Nevada, has recently gained a central position in the US geologic repository program. The goal of the repository is to protect the safety and health of the public for a period of 10,000 yr. The data-base and confidence levels must be developed in a manner consistent with this goal. However, there are no standard criteria that can be used to determine the confidence level required for a given parameter in order to ensure public health and safety. This is in part due to the interdependence of many of the site parameters important to repository performance. The process for refining confidence levels must be iterative in that performance and design analyses can initially be used as a screening tool to eliminate parameters from consideration if they can be shown to have little or no potential impact on repository performance. The parameters required to predict the range of variation in geologic conditions that is likely over the next 10,000 yr and the information necessary to estimate the probabilities of catastrophic geologic events must be obtained and utilized in continued performance and design analyses. Further sensitivity studies utilizing the improved data base can then be conducted and confidence levels for key geotechnical parameters can be refined