S5G reactor
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The S5G reactor was a prototype naval reactor designed for the United States Navy to provide electricity generation and propulsion on warships. The S5G designation stands for:
- S = Submarine platform
- 5 = Fifth generation core designed by the contractor
- G = General Electric was the contracted designer
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 coolant to be developed and maintained.
This nuclear reactor was installed both as a land-based prototype at the Nuclear Power Training Unit, Idaho National Engineering Laboratory near Idaho Falls, Idaho, and on board the USS Narwhal (SSN-671) (both have been decommissioned). It was intended to test the potential contribution of natural circulation technology to submarine quieting.[2][3][4] 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. Its design was the direct ancestor of the S8G reactor used on the Ohio class ballistic missile submarines, another very quiet submarine.
The S5G had 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 reduction in electrical requirements enabled this design to use only a single electrical turbine generator plant.
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 the USS Narwhal and the land-based prototype.
The concept of a natural circulation plant was relatively new when the Navy requested this design. 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. It was largely a success, although the design never became the basis for any more fast-attack submarines besides the Narwhal. The prototype testing included the simulation of essentially the entire engine room of an attack submarine. Floating the plant in a large pool of water allowed the prototype to be rotated along its long axis to simulate a hard turn. This was necessary to determine whether natural circulation would continue even during hard maneuvers, since natural circulation is dependent on gravity.
[edit] References
- ^ M. Ragheb (2006-01-15). "NUCLEAR MARINE PROPULSION". Retrieved on 2007-02-22.
- ^ Technical Innovations of the Submarine Force. Chief of Naval Operations Submarine Warfare Division. Retrieved on 2006-03-12.
- ^ Appendix C, Attachment to NR:IBO-05/023, Evaluation of Naval Reactors Facility Radioactive Waste Disposed of at the Radioactive Waste Management Complex (PDF). Retrieved on 2006-03-12.
- ^ SSN-671 Narwhal. GlobalSecurity.org. Retrieved on 2006-03-12.
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