Nuclear marine propulsion

Nuclear marine propulsion is propulsion of a ship or submarine with heat provided by a nuclear power plant. The power plant heats water to produce steam and it is this steam that powers the steam turbines and turbo generators. The power is then transferred to a gearbox that reduces the ratio by around 50 to 1 and this powers the propulsor. Naval nuclear propulsion is used specifically within naval warships (see Nuclear navy). Very few experimental civil nuclear ships have been built.

The ship or submarine will be fitted with one nuclear power plant. The plant is divided into two sides, port and starboard. This division of the plant provides a safety net should one side fail to function. Water is used to transfer heat generated by the power plant to steam generators (pressure vessels whose temperature is raised to approximately 250 to 300 °C (482 to 572 °F) by the heating element of the power plant's primary circuit). Since water vaporizes at 100 °C (212 °F) at normal pressure the system is pressurized, increasing the boiling temperature of the water. To transfer the heated water there are two sets of pumps on each side.

The steam is provided by water commonly referred to as feed water. This feed water is sea water pumped into the boat and desalinated. The desalinated water is then fed to the steam generators.

The primary circuit then heats the feed water turning it to steam. The steam passes through several driers and onto the main steam stop valve (port and starboard) as super heated dry steam.

The Russian, US and British navies rely on steam turbine propulsion, while the French and Chinese ships use the turbine to generate electricity for propulsion (turbo-electric transmission). Most nuclear submarines have a single reactor, but Russian submarines and USS Triton had two. Most American aircraft carriers are powered by two reactors, but USS Enterprise had eight. The majority of marine reactors are of the pressurized water type, although the US and Soviet navies have designed warships powered with liquid metal cooled reactors.

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