United States naval reactors United States Naval reactors are nuclear reactors used by the United States Navy aboard certain ships to produce power for propulsion , electric power , catapulting airplanes in aircraft carrier s , and a few more minor uses . Such Naval nuclear reactors have a complete power plant associated with them . All U . S . Navy submarine s and supercarrier s built for the past couple of decades are nuclear - powered by such reactors . There are no commissioned conventional ( non - nuclear ) submarines or aircraft carriers left in the U . S . Navy , since the last conventional carrier , , was decommissioned in May 2009 . The U . S . Navy had nine nuclear - powered cruiser s with such reactors also , but they have since been decommissioned . Reactors are designed by a variety of contractors , then developed and tested at one of several government ( Department of Energy ) - owned and prime contractor - operated facilities . These facilities include Bettis Atomic Power Laboratory in West Mifflin , PA and its associated Naval Reactors Facility in Idaho , and Knolls Atomic Power Laboratory in Niskayuna , NY and its associated Kesselring site in West Milton , NY , all under the management of the office of Naval Reactors . Sometimes there were full - scale nuclear - powered prototype plants built at the Naval Reactors Facility , Kesselring , and Windsor Locks ( in CT ) to test the nuclear plants , which were operated for years to train nuclear - qualified sailors . Reactor designations . Each reactor design is given a three - character designation consisting of : For example , a S9G reactor represents a submarine ( S ) , ninth - generation ( 9 ) , General Electric designed reactor ( G ) . History . Conceptual analysis of nuclear marine propulsion started in the 1940s . Research on developing nuclear reactors for the Navy was done at Bettis Atomic Power Laboratory in West Mifflin , Pennsylvania starting in 1948 . Under the long - term leadership of Admiral Hyman G . Rickover , the first test reactor plant , a prototype referred to as S1W , started up in U . S . in 1953 at the Naval Reactors Facility in Idaho . Bettis Laboratory and Naval Reactors Facility were operated initially and for many decades afterwards by Westinghouse . The first nuclear - powered vessel , the submarine , put to sea in 1955 . USS " Nautilus " marked the beginning of the transition of submarines from relatively slow and short - ranged conventional submarine s to ones capable of sustaining 20 – 25 knots ( 35 – 45 km / h ) submerged for weeks on end . Much of the early development work on naval reactors was done at the Naval Reactor Facility on the campus of the Idaho National Laboratory ( INL , previously INEL ) . USS " Nautilus " was powered by the S2W reactor , and crew were trained on the land - based S1W reactor at INL . The second nuclear submarine was , which was initially powered by a sodium - cooled S2G reactor , and supported by the land - based S1G reactor at the Kesselring site under Knolls Atomic Power Laboratory operated by General Electric . A spare S2G was also built but never used . USS " Seawolf " was plagued by superheater problems , with the result that USS " Nautilus " delivered far superior performance . This and the risks posed by liquid sodium in the event of an accident at sea led Admiral Rickover to select the PWR ( pressurized water reactor ) as the standard U . S . naval reactor type . The S2G was removed from USS " Seawolf " and replaced by the S2Wa reactor , using components from the spare S2W that was part of the USS " Nautilus " program . All subsequent U . S . naval reactors have been PWRs , while the Soviet Navy used mainly PWRs , but also used lead - bismuth cooled LMFRs of three types in eight submarines : " K - 27 " and the seven - member . Experience with the USS " Nautilus " led to the parallel development of further ( ) submarines , powered by single reactors , and an aircraft carrier , , powered by eight A2W reactor units in 1960 . A cruiser , , followed in 1961 and was powered by two C1W reactor units . The USS " Enterprise " remained in service for over 50 years . It was just recently decommissioned on 12 / 1 / 2012 . Full - scale land - based prototype plants in Idaho , New York , and Connecticut preceded development of several types ( generations ) of U . S . naval nuclear reactors , although not all of them . After initial construction , some engineering testing was done and the prototypes were used to train nuclear - qualified sailors for many years afterwards . For example , the A1W prototype at Naval Reactors Facility led to development of A2W reactors used in USS " Enterprise " . By 1962 , the US Navy had 26 nuclear submarines operational and 30 under construction . Nuclear power had revolutionized the U . S . Navy . The technology was shared with the United Kingdom , while technological development in France , China and the Soviet Union proceeded separately . After the " Skate " - class vessels , reactor development proceeded and in the U . S . a single series of standardized designs was built by both Westinghouse and General Electric , with one reactor powering each vessel . Rolls Royce built similar units for Royal Navy submarines and then developed the design further to the PWR - 2 . Numerous submarines with an S5W reactor plant were built . At the end of the Cold War in 1989 , there were over 400 nuclear - powered submarines operational or being built . Some 250 of these submarines have now been scrapped and some on order canceled , due to weapons reduction programs . The Russian Navy and United States Navy had over one hundred each , with the United Kingdom and France less than twenty each and China six . The total today is about 160 . The United States is the main navy with nuclear - powered aircraft carriers ( 10 ) , while Russia has nuclear - powered cruisers . Russia has eight nuclear icebreakers in service or building . Since its inception in 1948 , the U . S . Navy nuclear program has developed 27 different plant designs , installed them in 210 nuclear - powered ships , taken 500 reactor cores into operation , and accumulated over 5 , 400 reactor years of operation and 128 , 000 , 000 miles safely steamed . Additionally , 98 nuclear submarines and six nuclear cruisers have been recycled . The U . S . Navy has never experienced a reactor accident . Note that all nine of the U . S . Navy nuclear - powered cruisers ( CGN ) have now been stricken from the Naval Vessel Register , and those not already scrapped by recycling are scheduled to be recycled . While reactor accidents have not sunk any U . S . Navy ships or submarines , two nuclear - powered submarines , and were lost at sea . The condition of these reactors has not been publicly released , although both wrecks have been investigated by Dr . Robert Ballard on behalf of the Navy using remotely operated vehicles ( ROV s ) . Congress has mandated that the U . S . Navy consider nuclear power as an option on all large surface combatants ( cruisers , destroyers ) and amphibious assault ships . If proven cost - effective in a life cycle cost analysis during the Analysis of Alternatives ( AoA ) phase of preliminary ship design , new ship classes ( e . g . CG ( X ) ) could proceed with nuclear propulsion . Power plants . U . S . naval reactors are pressurized water reactors , which differ from commercial reactors producing electricity in that : Long core life is enabled by high uranium enrichment and by incorporating a " burnable neutron poison " , which is progressively depleted as non - burnable poison s like fission product s and actinide s accumulate . The loss of burnable poison counterbalances the creation of non - burnable poisons and result in stable long term fuel efficiency . Long - term integrity of the compact reactor pressure vessel is maintained by providing an internal neutron shield . ( This is in contrast to early Soviet civil PWR designs where embrittlement occurs due to neutron bombardment of a very narrow pressure vessel . ) Reactor sizes range up to ~ 500 MWt ( about 165 MWe ) in the larger submarines and surface ships . The French s have a 48 MW reactor that needs no refueling for 30 years . The navies of the Russian Federation , the United States , and the United Kingdom rely on steam turbine propulsion . Those of the French and Chinese use the turbine to generate electricity for propulsion . Most Russian submarines as well as all U . S . surface ships since " Enterprise " are powered by two or more reactors . U . S . , British , French and Chinese submarines are powered by one . Decommissioning nuclear - powered submarines has become a major task for American and Russian navies . After defuelling , U . S . practice is to cut the reactor section from the vessel for disposal in shallow land burial as low - level waste ( see the Ship - Submarine recycling program ) . In Russia the whole vessels , or the sealed reactor sections , remain stored afloat indefinitely . Other small , easily field - deployed reactor designs have been developed but have no connection to the U . S . Naval Reactor program . A small reactor was used to supply power ( 1 . 5 MWe ) and heating to McMurdo Station , a U . S . Antarctic base , for ten years to 1972 , testing the feasibility of such air - portable units for remote locations . Two others were installed in Arctic locations , all constructed as part of the U . S . Army Nuclear Power Program . A fourth mounted on a barge provided power and fresh water in the Panama Canal Zone . The Russian Federation is well advanced with plans to build a floating power plant for their far eastern territories . The design has two 35 MWe units based on the KLT - 40 reactor used in icebreakers ( with refueling every 4 years ) .