Performance Assessment

Performance assessment (PA) is defined in the United States by the Environmental Protection Agency (EPA) and the Nuclear Regulatory Commission (NRC) regulations as a process to be used in estimating the long-term performance of deep geologic disposal sites for high-level and transuranic radioactive waste. Although specific regulatory requirements differ for individual projects (e.g., the Waste Isolation Pilot Plant and the potential repository at Yucca Mountain), the overall approach to PA is similar in repository programs both within the U.S. and internationally. PAs provide a quantitative estimate of the overall performance of the disposal concept, taking into account the uncertainty associated with the behavior of engineered and natural systems over very long periods of time. Results are compared to regulatory limits, in terms of annual radiation doses to hypothetical future humans or cumulative radionuclide releases from the site, and uncertainty in those results is evaluated as part of the decision-making process before the site is approved for operation.