A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. When a fissile nucleus like uranium-235 or plutonium-239 absorbs a neutron, it splits into lighter nuclei, releasing energy, gamma radiation, and free neutrons, which can induce further fission in a self-sustaining chain reaction. The process is carefully controlled using control rods and neutron moderators to regulate the number of neutrons that continue the reaction, ensuring the reactor operates safely, although inherent control by means of delayed neutrons also plays an important role in reactor output control. The efficiency of nuclear fuel is much higher than fossil fuels; the 5% enriched uranium used in the newest reactors has an energy density 120,000 times higher than coal.
United States naval reactors are nuclear reactors used by the United States Navy aboard certain ships to generate the steam used to produce power for propulsion, electric power, catapulting airplanes in aircraft carriers, and a few minor uses. Such naval nuclear reactors have a complete power plant associated with them. All commissioned U.S. Navy submarines and supercarriers built since 1975 are nuclear powered, with the last conventional carrier, USS Kitty Hawk, being decommissioned in May 2009. The U.S. Navy also had nine nuclear-powered cruisers with such reactors, but they have since been decommissioned also.
The D1G reactor was a prototype naval reactor designed for the United States Navy to provide electricity generation and propulsion on warships. The D1G designation stands for:
The D2G reactor was a naval reactor used by the United States Navy from 1962 to provide propulsion and electricity generation on warships. Ships powered by the reactor were decommissioned at around the end of the 20th century. The D2G designation stands for:
USS Long Beach (CLGN-160/CGN-160/CGN-9) was a nuclear-powered guided missile cruiser in the United States Navy and the world's first nuclear-powered surface combatant. She was the third Navy ship named after the city of Long Beach, California.
The S5G reactor was a prototype naval reactor designed for the United States Navy to provide electricity generation and propulsion on submarines. The S5G designation stands for:
The A3W reactor was a naval reactor used by the United States Navy to provide electricity generation and propulsion on warships. Like all operational U.S. naval reactors it was a pressurized water reactor (PWR) design. The A3W designation stands for:
A nuclear-powered icebreaker is an icebreaker with an onboard nuclear power plant that produces power for the vessel's propulsion system. Although more expensive to operate, nuclear-powered icebreakers provide a number of advantages over their diesel-powered counterparts, especially along the Northern Sea Route where heavy power demand associated with icebreaking, limited refueling infrastructure along the Siberian coast, and endurance required make diesel-powered icebreaker operations challenging. As of 2023, Russia is the only country that builds and operates nuclear-powered icebreakers, having built a number of such vessels to aid shipping along the Northern Sea Route and Russian arctic outposts since the Soviet era.
The S6G reactor is a naval reactor used by the United States Navy to provide electricity generation and propulsion on Los Angeles-class attack submarines. The S6G designation stands for:
A nuclear submarine is a submarine powered by a nuclear reactor, but not necessarily nuclear-armed. In the US classification, nuclear-powered submarines are designated as SSxN, where the SS denotes submarine, x=G means that the submarine is equipped with guided missiles, x=B means that the submarine is equipped with ballistic missiles and the N means that the submarine is nuclear-powered. SSN refers to nuclear-powered attack submarines, which do not carry missiles.
Nuclear marine propulsion is propulsion of a ship or submarine with heat provided by a nuclear reactor. The power plant heats water to produce steam for a turbine used to turn the ship's propeller through a gearbox or through an electric generator and motor. Nuclear propulsion is used primarily within naval warships such as nuclear submarines and supercarriers. A small number of experimental civil nuclear ships have been built.
A nuclear navy, or nuclear-powered navy, refers to the portion of a navy consisting of naval ships powered by nuclear marine propulsion. The concept was revolutionary for naval warfare when first proposed. Prior to nuclear power, submarines were powered by diesel engines and could only submerge through the use of batteries. In order for these submarines to run their diesel engines and charge their batteries they would have to surface or snorkel. The use of nuclear power allowed these submarines to become true submersibles and unlike their conventional counterparts, they became limited only by crew endurance and supplies.
Air-independent propulsion (AIP), or air-independent power, is any marine propulsion technology that allows a non-nuclear submarine to operate without access to atmospheric oxygen. AIP can augment or replace the diesel-electric propulsion system of non-nuclear vessels.
The A1B reactor is developed by the United States Navy for the Gerald R. Ford-class nuclear-powered aircraft carriers. Each ship will be powered by two A1B reactors. The new reactor was named A1B, following the Navy's reactor-designation scheme of type, generation, and manufacturer: A for aircraft carrier, 1 for the maker's first reactor plant design, and B for Bechtel, the company making the reactor.
The California class was a pair of nuclear-powered guided-missile cruisers operated by the United States Navy between 1974 and 1998. Other than their nuclear power supply and lack of helicopter hangars, ships of the California class were comparable to other guided-missile cruisers of their era, such as the Belknap class. The class was built as a follow-up to the nuclear-powered Long Beach, Bainbridge, and Truxtun classes. Like all of the nuclear cruisers, which could steam for years between refuelings, the California class was designed in part to provide high endurance escort for the navy's nuclear aircraft carriers, which were often limited in range due to their conventionally powered escorts continuously needing to be refueled.
The S5W reactor is a nuclear reactor used by the United States Navy to provide electricity generation and propulsion on warships. The S5W designation stands for:
Leahy-class cruisers were a class of guided-missile cruisers built for the United States Navy. They were originally designated as Destroyer Leaders (DLG), but in the 1975 cruiser realignment they were reclassified as guided-missile cruisers (CG).
The United States Navy Nuclear Propulsion community consists of Naval Officers and Enlisted members who are specially trained to run and maintain the nuclear reactors that power the submarines and aircraft carriers of the United States Navy. Operating more than 80 nuclear-powered ships, the United States Navy is currently the largest naval force in the world.
In the early 1960s, the United States Navy was the world's first to have nuclear-powered cruisers as part of its fleet. The first such ship was USS Long Beach (CGN-9). Commissioned in late summer 1961, she was the world's first nuclear-powered surface combatant. She was followed a year later by USS Bainbridge (DLGN-25). While Long Beach was a 'true cruiser', meaning she was designed and built as a cruiser, Bainbridge began life as a frigate, though at that time the Navy was using the hull code "DLGN" for "destroyer leader, guided missile, nuclear". This was prior to the enactment of the 1975 ship reclassification plan, in which frigates (DLG/DLGN), which were essentially large destroyers, were reclassified as cruisers, so that the US Navy's numbers would compete with those of the Soviet Navy. Long Beach, the largest of all the nuclear cruisers, was equipped with a C1W cruiser reactor, while all the others were equipped with D2G destroyer reactors.
