Performance Assessment in Early Phases of the Repository Design Process

Assessments of post-closure performance are an integral part of the design process for a repository for high-level nuclear waste. They provide input to the establishment of design requirements and to the evaluation of designs against these requirements. During early design phases, the assessments are limited by capabilities of analytical models, uncertainties about conceptual models, and a lack of site data. The use of performance assessment in recent design activities for the Yucca Mountain Site Characterization Project, including a study of alternatives for an exploratory shaft facility (ESF), demonstrates the necessity of significant engineering judgment in the interpretation and application of early analyses. Maintaining flexibility for some aspects of repository design is prudent.