The S6W reactor is a naval reactor used by the United States Navy to provide electricity generation and propulsion on warships. The S6W designation stands for: * S = Submarine platform * 6 = Sixth generation core designed by the contractor * W = Westinghouse was the contracted designer The S6W's reactor core was prototyped in the land-based S8G plant at Knolls Atomic Power Laboratory's Kesselring Site in West Milton, NY starting in March 1994. The three ships of the Seawolf class submarine were built with S6W reactors.