Nuclear Submarines Fleet Strength by Country 2022 || in 3DA nuclear submarine is a submarine powered by a nuclear reactor, but not necessarily nuclear-armed.The idea for a nuclear-powered submarine was first proposed in the United States Navy by the Naval Research Laboratory’s physicist Ross Gunn[4] in 1939. The Royal Navy began researching designs for nuclear propulsion plants in 1946.This is official data. But that doesn’t mean they are true. Many countries hide their development of military weapons.