S3W reactor

The S3W reactor is a naval reactor used by the United States Navy to provide electricity generation and propulsion on warships. The S3W designation stands for:

• S – Submarine platform
• 3 – Third generation core designed by the contractor
• W – Westinghouse was the contracted designer

This nuclear reactor was a variant of the Submarine Fleet Reactor (SFR), an advance on the pressurized water reactor (PWR) plant design employed on USS Nautilus.^[1] The S3W plant utilized horizontal U-tube steam generators. This concept developed into vertical U-tube steam generators in the S5W reactor plant, and is in common use today on commercial PWR power plants.

USS Halibut and the four Skate-class boats were built with S3W reactors: USS Skate, USS Swordfish, USS Sargo, and USS Seadragon.^[2][3] USS Swordfish and USS Seadragon had the S3W reactor installed in the S4W reactor plant, which was an alternate arrangement of the same components.