U.S. and Soviet navies are retiring or denuclearizing large numbers of ships and submarines in the transition from Cold War footing. In addition, many weapon systems have been retired or modified for conventional missions and others reassessed as non-nuclear. The U.S. Navy has been shifting nonstrategic nuclear delivery platforms from surface ships to attack submarines, reflecting the increased role of nuclear-armed cruise missiles, a trend being repeated in the Soviet Navy. About 513 nuclear power reactors are at sea. The Soviet Union uses 324 reactors to run its fleet of nuclear-powered submarines, cruisers, and icebreakers.
Most Soviet submarines have two reactors, as do all Soviet nuclear-powered cruisers and icebreakers.
The United States has 155 nuclear reactors in its nuclear-powered submarines, aircraft carriers, cruisers, and a single submersible research vehicle. All U.S. submarines have one reactor each and U.S. cruisers have two. Four aircraft carriers have two reactors each and one aircraft carrier has eight. British, French, and Chinese vessels operate on single reactors. The impending retirement of dozens of nuclear-powered vessels portends a decline in the number of reactors in the 1990s and a considerable number to be disposed of.