S1C reactor, Nuclear prototype reactor in Windsor, Connecticut, US

The S1C reactor was a naval prototype located in Windsor, Connecticut, built to test submarine propulsion using steam turbines connected to generators rather than mechanical reduction gears. The facility also served as a training ground for Navy personnel learning to operate nuclear-powered vessels.

The S1C reactor was built in the 1950s and began operating in 1959, a period when the Navy was actively developing nuclear propulsion for submarines. It stayed in service through the Cold War and was shut down in 1993.

The site was one of the few military nuclear facilities to be fully released for civilian use after the Cold War ended. That outcome changed how other countries approached the decommissioning of military reactors.

The site in Windsor is not open to the public, as it was a restricted military facility. Anyone interested in the history of the area may find relevant information at nearby educational or historical centers.

After it was shut down, the S1C became the first reactor site anywhere to be released without any radiological or chemical restrictions. This was considered a milestone in the field and influenced how decontamination was approached at nuclear sites around the world.