S1W reactor

The S1W reactor was the first prototype naval reactor used by the United States Navy to prove that the technology could be used for electricity generation and propulsion on submarines. The S1W designation stands for

The land-based nuclear reactor was built at the National Reactor Testing Station, later called Idaho National Engineering Laboratory near Arco, Idaho. The plant was the prototype for the USS Nautilus (SSN-571), the world's first nuclear-powered submarine. The specific location within the vast Idaho National Laboratory where the S1W prototype was located was the Naval Reactors Facility.

Under the leadership of Admiral Hyman G. Rickover, Naval Reactors followed a concurrent design strategy, with the design and construction of the S1W reactor taking place ahead of the design and construction of the Nautilus. This enabled problems to be identified and resolved before they appeared in the shipboard plant. To better support this design process, the S1W power plant was built inside of a submarine hull. While the cramped spaces prevented engineers from obtaining information on some plant components, it provided a much more realistic example of how the shipboard plant would have to be constructed.

The S1W was a pressurized water reactor that utilized water as the coolant and neutron moderator in its primary system, and enriched Uranium-235 in its fuel elements. The S1W reactor reached criticality on March 30, 1953. In May of that year, it began power operations, performing a 100-hour run that simulated a submerged voyage from the east coast of the United States to Ireland. This test run clearly demonstrated the revolutionary impact that nuclear propulsion would have upon the submarine, which prior to that time was greatly limited in its ability to conduct continuous underwater operations by battery life and by the oxygen requirement of diesel propulsion systems.

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