By December 2004, the U.S. Department of Energy (DOE) plans to submit a license application for a proposed high-level radioactive waste repository at Yucca Mountain, Nevada. The U.S. Nuclear Regulatory Commission (NRC) would review DOE's application and decide whether to authorize repository construction. That application would include a performance confirmation plan for the proposed site. Performance confirmation (PC) refers to the tests, experiments,and analyses that will be done to evaluate the adequacy of information used to show compliance with performance objectives in NRC's regulation 10 CFR Part 63. The program must provide data that indicate, where practical, whether subsurface conditions encountered and changes in those conditions during construction and waste emplacement are within limits assumed in the licensing review; and whether natural and engineered systems and components required for repository operation that are designed or assumed to operate as barriers after permanent closure are functioning as intended and anticipated. The PC program must begin during site characterization and continue until permanent closure of a repository.