Summary: GAO discussed the Department of Energy's (DOE) use of appropriated funds for completing a scientific investigation needed to obtain a Nuclear Regulatory Commission (NRC) license to construct and operate a nuclear waste repository site at Yucca Mountain, Nevada. GAO noted that: (1) DOE was not ready to begin on-site investigations, originally scheduled for 1987, until 1991 because it took longer than it expected to complete its site investigation plan and NRC compliance program; (2) Nevada did not issue essential environmental permits that DOE needed before it could start the investigation; (3) prior to 1987, DOE spent about $48 million on drilling holes and obtaining core samples, but due to technical and management problems, the samples' usefulness was unclear; (4) from 1989 to 1990, DOE spent $12 million on developing a new drilling technology and core management facility to use in on-site investigation; (5) DOE spent over $36 million in 1988 and 1989 on the design of an exploratory shaft facility before selecting a new facility design and construction plan due to external criticism of its original plan; (6) it was unclear as to how much of the original design work DOE will have to redo or the additional costs that it will incur due to the new plan; and (7) DOE and its contractors spent about $122 million, or 25 percent of total project costs, on general management of the Yucca Mountain project over a 3-year period.