FILE - This March 30, 1979, file photo shows an aerial view of the Three Mile Island nuclear power plant near Harrisburg, Pa. The small dome at center is where the "incident" occured. A presidential commission later said the TMI accident was "the result of a series of human, institutional and mechanical failures'' that had implications throughout the U.S. nuclear industry as it operated at that time. (AP Photo/Barry Thumma, File)