46°33′54.8″N119°31′09.7″W / 46.565222°N 119.519361°W /46.565222; -119.519361
United States naval reactors arenuclear reactors used by theUnited States Navy aboard certain ships to generate thesteam used to producepower forpropulsion,electric power, catapulting airplanes inaircraft carriers, and a few minor uses. Such naval nuclear reactors have a completepower plant associated with them. All commissioned U.S. Navysubmarines andsupercarriers built since 1975 arenuclear powered, with the last conventional carrier,USS Kitty Hawk, being decommissioned in May 2009. The U.S. Navy also had nine nuclear-poweredcruisers with such reactors, but they have since been decommissioned also.
Reactors are designed by a number of contractors,[who?] then developed and tested at one of severalDepartment of Energy-owned and prime contractor-operated facilities:Bettis Atomic Power Laboratory inWest Mifflin, Pennsylvania and its associatedNaval Reactors Facility inIdaho, andKnolls Atomic Power Laboratory inNiskayuna, New York and its associated Kesselring site inWest Milton, New York, all under the management of the office ofNaval Reactors. Sometimes there were full-scale nuclear-poweredprototype plants built at the Naval Reactors Facility, Kesselring, and Windsor (inConnecticut) to test the nuclear plants, which were operated for years to train nuclear-qualified sailors.
Each reactor design is given a three-character designation consisting of:
For example, aS9G reactor represents a submarine (S), ninth-generation (9), General Electric designed reactor (G).
Conceptual analysis ofnuclear marine propulsion started in the 1940s. Research on developing nuclear reactors for the Navy was done atBettis Atomic Power Laboratory inWest Mifflin, Pennsylvania starting in 1948. Under the long-term leadership of AdmiralHyman G. Rickover, the first test reactor plant, aprototype referred to asS1W, started up in U.S. in 1953 at theNaval Reactors Facility inIdaho. Bettis Laboratory and Naval Reactors Facility were operated initially and for many decades afterwards byWestinghouse. The first nuclear-powered vessel, thesubmarineUSS Nautilus, put to sea in 1955. USSNautilus marked the beginning of the transition of submarines from relatively slow and short-ranged conventional submarines to ones capable of sustaining 20–25knots (37–46 km/h; 23–29 mph) submerged for weeks on end.
Much of the early development work on naval reactors was done at the Naval Reactors Facility on the campus of theIdaho National Laboratory (INL, previously INEL). USSNautilus was powered by theS2W reactor, and crew were trained on the land-basedS1W reactor at INL.
The secondnuclear submarine wasUSS Seawolf, which was initially powered by asodium-cooledS2G reactor, and supported by the land-basedS1G reactor at the Kesselring site underKnolls Atomic Power Laboratory operated byGeneral Electric. A spare S2G was also built but never used.
USSSeawolf was plagued by superheater problems, with the result that USSNautilus 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 thepressurized water reactor (PWR) as the standard U.S. naval reactor type. The S2G was removed from USSSeawolf and replaced by theS2Wa reactor, using components from the spare S2W that was part of the USSNautilus program. All subsequent U.S. naval reactors have been PWRs, while theSoviet Navy used mainly PWRs, but also used lead-bismuth cooledliquid metal cooled reactors (LMFR) of three types in eight submarines:K-27 and the seven-memberAlfa class.
Experience with USSNautilus led to the parallel development of further (Skate-class) submarines, powered by single reactors, and anaircraft carrier,USS Enterprise, powered by eightA2W reactor units in 1960. A cruiser,USS Long Beach, followed in 1961 and was powered by twoC1W reactor units. USSEnterprise remained in service for over 50 years, and was inactivated in 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, theA1W prototype at Naval Reactors Facility led to development ofA2W reactors used in USSEnterprise. 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 theSoviet Union proceeded separately.
After theSkate-class vessels, reactor development proceeded and in the U.S. a single series of standardized designs was built by bothWestinghouse and General Electric, with one reactor powering each vessel.Rolls-Royce built similar units as thePWR1 forRoyal Navy submarines and then developed the design further to the PWR2. Numerous submarines with anS5W reactor plant were built.
At the end of theCold 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. TheRussian 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 eightnuclear 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 disclosed a reactor accident,[1][2] but has suffered at least one coolant loss accident, on theUSS Guardfish.[3]
All nine of the U.S. Navy nuclear-powered cruisers (CGN) have now been stricken from theNaval 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,USS Thresher andUSS Scorpion were lost at sea. The condition of these reactors has not been publicly released, although both wrecks have been investigated byRobert Ballard on behalf of the Navy usingremotely operated vehicles (ROVs).[citation needed]
Congress has mandated that the U.S. Navy consider nuclear power as an option on all large surface combatants (cruisers,destroyers) andamphibious assault ships. If proven cost-effective in alife cycle cost analysis during theAnalysis of Alternatives (AoA) phase of preliminary ship design, new ship classes (e.g. CG(X)) could proceed with nuclear propulsion.
Current U.S. naval reactors are all pressurized water reactors,[4] which are identical to PWR commercial reactors producing electricity, except that:
Long core life is enabled by high uranium enrichment and by incorporating a "burnable neutron poison", which is progressively depleted asnon-burnable poisons likefission products andactinides accumulate. The loss of burnable poison counterbalances the creation of non-burnable poisons and result in stable long termfuel 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 FrenchRubis-class submarines have a 48 MW reactor that needs no refueling for 30 years.
The nuclear navies of the United States, the United Kingdom, and the Russian Federation 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 sinceEnterprise are powered by two or more reactors. U.S., British, French, Chinese and Indian submarines are powered by one.
Decommissioning nuclear-powered submarines has become a major task for American and Russian navies.[6] 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 theShip-Submarine Recycling Program).
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