Yucca Mountain, NV, is being characterized for disposal of U.S. high level nuclear waste, which consists predominantly of spent fuel from nuclear reactors and radioactive waste from reprocessing. In this paper, the program is presented in the context of global and U.S. nuclear energy systems and of international plans for high-level waste disposal. The potential impact of the proposed repository is discussed in the context of the U.S. Department of Energy＇s Total System Performance Assessment-Viability Assessment, the primary tool for assessing how the repository might operate.