S5G reactor

The S5G designation stands for: The S5G was a pressurized water reactor[1] plant with two coolant loops and two steam generators.

It had to be designed with the reactor vessel situated low in the boat and the steam generators high in order for natural circulation of the primary coolant to be developed and maintained.

This massive size was necessary to allow it to turn slowly enough to directly drive the screw and be fairly efficient in doing so.

The prototype plant in Idaho was therefore given quite a rigorous performance shakedown to determine if such a design would work for the US Navy.

The prototype testing included the simulation of essentially the entire engine room of an attack submarine.