S5G reactor

Design

The S5G was a pressurized water reactor 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.

Reactor primary coolant pumps are one of the primary sources of noise from submarines, and the elimination of coolant pumps and associated equipment would also reduce mechanical complexity and the space required by propulsion equipment.

The S5G had primary coolant pumps, but they were only needed for very high speeds. And since the reactor core was designed with very smooth paths for the coolant, the coolant pumps were smaller and quieter than the ones used by the competing S5W core. They were also fewer in number. In most cases the submarine could be operated without using coolant pumps at all. The quiet design resulted in a larger hull diameter but required larger primary coolant piping than the competing S5W reactor. Due to the larger size, the S5G was not used in subsequent attack submarines, but was a precursor to the S8G reactor design used in the larger s.

To further reduce engine plant noise, the normal propulsion setup of two steam turbines driving the screw through a reduction gear unit was changed instead to one large propulsion turbine with no reduction gears. This eliminated the noise from the main reduction gears, but the cost was to have a huge main propulsion turbine. The turbine was cylindrical, about 12 feet in diameter, and about 30 feet long. 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 same propulsion setup was used on both USS Narwhal and the land-based prototype.

History

This nuclear reactor was installed both at a land-based prototype—initially used for testing the concept and, later, for training thousands of Navy operators—at the Naval Reactor Facility, Idaho National Laboratory near Arco, Idaho, and in the USS Narwhal (SSN-671); both have been decommissioned. It was intended to test the potential contribution of natural circulation technology to submarine quieting.

Built in the early 1960s, the S5G prototype was permanently shut down in May 1995.

References

References

1. M. Ragheb. (2006-01-15). "NUCLEAR MARINE PROPULSION".
2. (18 August 2000). "US Nuclear Propulsion".
3. "Technical Innovations of the Submarine Force". Chief of Naval Operations Submarine Warfare Division.
4. "Appendix C, Attachment to NR:IBO-05/023, Evaluation of Naval Reactors Facility Radioactive Waste Disposed of at the Radioactive Waste Management Complex".
5. (4 November 2014). "Submarine Torpedo Tactics: An American History". McFarland.
6. [https://interestingengineering.com/photo-story/us-decommissioning-of-s5g-submarine-reactor Photos: US’ submarine reactor heads for demolition after decades of service]
7. [https://www.energy.gov/em/articles/em-set-demolish-second-submarine-reactor-prototype-idaho EM Set to Demolish Second Submarine Reactor Prototype in Idaho]
8. [https://www.dvidshub.net/news/484295/naval-reactors-facility-turns-over-defueled-s5g-prototype-demolition Naval Reactors Facility Turns Over Defueled S5G Prototype for Demolition]