Summary: The Department of Energy (DOE) has been investigating Yucca Mountain, Nevada, as a possible repository for highly radioactive nuclear waste. In February, the Secretary of Energy endorsed the Yucca Mountain site, and the President recommended that Congress approve the site. If the site is approved, DOE must apply to the Nuclear Regulatory Commission (NRC) for authorization to build a repository. If the site is not approved for a license application, or if NRC denies a construction license, the administration and Congress will have to consider other options. GAO concludes that DOE is unprepared to submit an acceptable license application to NRC within the statutory deadlines if the site is approved. On the basis of a reassessment done by DOE's managing contractor in September 2001, GAO believes that DOE would not have enough time to obtain a license from NRC and build and open the repository by 2010. DOE lacks a reliable estimate of when, and at what cost, a license application can be submitted or a repository can be opened.