The S6G reactor is a naval reactor

United States Naval reactor

United States Naval reactor refers to nuclear reactors used by the United States Navy aboard certain ships to produce power for propulsion, electric power, catapulting airplanes in aircraft carriers, and a few more minor uses. Such Naval nuclear reactors have a complete power plant associated with...

 used by the United States Navy

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

 to provide electricity generation

Electricity generation

Electricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...

 and propulsion

Nuclear marine propulsion

Nuclear marine propulsion is propulsion of a ship by a nuclear reactor. Naval nuclear propulsion is propulsion that specifically refers to naval warships...

 on warship

Warship

A warship is a ship that is built and primarily intended for combat. Warships are usually built in a completely different way from merchant ships. As well as being armed, warships are designed to withstand damage and are usually faster and more maneuvrable than merchant ships...

s. The S6G designation stands for:

• S = Submarine
  Submarine
  A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...
  
   platform
• 6 = Sixth generation core
  Nuclear reactor core
  A nuclear reactor core is the portion of a nuclear reactor containing the nuclear fuel components where the nuclear reactions take place.- Description :...
  
   designed by the contractor
• G = General Electric
  General Electric
  General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
  
   was the contracted designer

This nuclear reactor

Nuclear reactor

A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...

 was designed by General Electric for use on the Los Angeles class

Los Angeles class submarine

The Los Angeles class, sometimes called the LA class or the 688 class, is a class of nuclear-powered fast attack submarines that forms the backbone of the United States submarine fleet. With 43 submarines on active duty and 19 retired, the Los Angeles class is the most numerous nuclear powered...

 attack submarines. The S6G reactor plant consists of the reactor coolant

Coolant

A coolant is a fluid which flows through a device to prevent its overheating, transferring the heat produced by the device to other devices that use or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor...

, steam generation

Steam generator (nuclear power)

Steam generators are heat exchangers used to convert water into steam from heat produced in a nuclear reactor core. They are used in pressurized water reactors between the primary and secondary coolant loops....

, and other support systems that supply steam to the engine room. The 688-class engine room also contains the steam turbine

Steam turbine

A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....

s that generate electricity and drive the propeller shaft. While exact specifications are classified, the S6G reactor can propel a Los Angeles class submarine at over 15 knots (29.4 km/h) when surfaced and over 25 knots (49 km/h) while submerged.

Design and operational support for the S6G is provided by Knolls Atomic Power Laboratory

Knolls Atomic Power Laboratory

Knolls Atomic Power Laboratory is a research and development facility dedicated to the support of the US Naval Nuclear Propulsion Program. KAPL is a government-owned, contractor operated laboratory run by Bechtel Marine Propulsion Corporation for the United States Department of Energy. KAPL is...

 (KAPL). The S6G reactor plant was originally designed to use the D1G-2 core

D1G reactor

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:* D = Destroyer platform* 1 = First generation core designed by the contractor...

, similar to the D2G reactor

D2G reactor

The D2G reactor was a naval reactor used by the United States Navy to provide electricity generation and propulsion on warships. The D2G designation stands for:* D = Destroyer platform* 2 = Second generation core designed by the contractor...

 used on the Bainbridge class

Bainbridge class cruiser

' was a nuclear-powered version of the double-ended guided missile frigate. Originally a guided missile destroyer leader, the class was re-designated guided missile cruiser in 1975...

 guided missile cruiser, which is rated at 148 MW. All Los Angeles class submarines from on were built with a D2W core rated at 165 MW, as opposed to the older 150 MW cores found on older ships. The D1G-2 cores are being replaced with D2W cores when the ships are refueled.