The S6G reactor is a naval reactor used by the United States Navy to provide electricity generation and propulsion on Los Angeles-class submarine attack submarines. The S6G designation stands for:

Design

This nuclear reactor was designed by General Electric for use on the Los Angeles-class submarine attack submarines. The S6G reactor plant consists of the reactor coolant, steam generation, and other support systems that supply steam to the engine room. The S6G is a 165 megawatt (MW) reactor driving two 26 MW steam turbines. The Los Angeles-class engine room also contains the steam turbines 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 kn when surfaced and over 25 kn while submerged. Design and operational support for the S6G is provided by Knolls Atomic Power Laboratory (KAPL). The S6G reactor plant was originally designed to use the D1G-2 core, similar to the D2G reactor used on the Bainbridge-class cruiser guided missile cruiser. All Los Angeles-class submarines from USS Providence (SSN-719) on were built with a D2W core. The D1G-2 cores are being replaced with D2W cores when the boats are refueled.