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S5G
The S5G nuclear propulsion plant, installed only on the SSN-671 Narwhal, was a natural-circulation reactor intended to test the potential contribution of this technology to submarine quieting. Reactor primary coolant pumps are one of the primary sources of noise from submarines, second only to steam turbines, and the elimination of coolant pumps and associated equipment also results in the reduction of mechanical complexity and the volume required by propulsion equipment.
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S6W Advanced Fleet Reactor
The S6W Advanced Fleet Reactor that powers the SEAWOLF Class is revolutionary in the military sense -- quietness and more efficient performance. It is not a radical design from a safety standpoint. The reactor is a typical Naval pressurized water reactor. The advanced fleet reactor has been installed in the S8G prototype plant for testing, and the S8G prototype plant with the Advanced Fleet Reactor will operate exactly as it has for the past 12 years. That reactor went critical in March 1994 and operated well. Putting the new reactor in a prototype affords the opportunity to operate it before introduction into the fleet, run it harder than in the fleet to determine its peak performance, and test its long-term properties. For the shipboard plant, the reactor core was loaded March 1995 and the ship's pre-commissioning crew began operating reactor plant systems.
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S9G Next Generation Reactor
The Navy now is well into designing the New Attack Submarine -- a technologically robust ship that provides the best balance between cost and capability. This new submarine will cost about the same as a new improved LOS ANGELES Class ship while retaining SEAWOLF quieting -- an essential military feature in a submarine. The ship will achieve the lowest cost possible commensurate with required military capability. For example, reduced speed allows lower acquisition and life cycle costs through simplification, producibility improvements, and new technology (e.g.,fewer components, enhanced modular construction, new electric plant design, and life-of-the-ship reactor core).
The S9G Next Generation Reactor and associated components which will have increased energy density. The core that is under development for the New Attack Submarine is expected to last the life of the ship. Eliminating the need for a refueling will reduce life cycle costs, cut down the radiation exposure of shipyard workers, and lessen the amount of radioactive waste generated. This is possible because of many developments such as use of advanced computers to perform three-dimensional nuclear, thermal, and structural calculations; further exploitation of the modified fuel process; and better understanding of various reactor technologies which permits more highly optimized designs. Performance improvements are gained through advances in such areas as thermal-hydraulics and structural mechanics, and by optimizing reactor-to-systems interfaces.
The new reactor which will have increased energy density, and new plant components, such as the new concept steam generator, with improved corrosion resistance and reduced life-cycle costs. The new steam generators will also allow greater plant design flexibility and decreased construction costs due to smaller size, spatial orientation, and improved heat transfer efficiency which reduces coolant flow requirements. A new concept steam generator will alleviate the corrosion concerns encountered in existing designs of steam generators, while reducing component size and weight and providing greater flexibility in overall arrangement.