S9G Next Generation Reactor
High Energy Density Core

The Navy New Attack Submarine is a technologically robust ship that provides the best balance between cost and capability. This new submarine costs about the same as a new improved LOS ANGELES Class ship while retaining SEAWOLF quieting -- an essential military feature in a submarine. The ship would 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 reactor plant was designed for the Virginia-class SSN, which has a 33 ft (10.1 m) diameter hull, the same as USS Narwhal (SSN-671) and all Los Angeles-class SSNs. It is believed that S9G is designed for natural circulation core cooling and is capable of operating at a significant fraction of full power without reactor coolant pumps.

There was no S9G prototype. S9G is used operationally on all Virginia-class SSNs. 1st-in-class USS Virginia (SSN-774) was commissioned in October 2004. The propulsion system consists of 1 x S9G reactor rated @ 210 MWt (est); secondary steam plant delivering a combined 40,000 shaft horsepower (29.8 MW) to a single pump-jet propulsor. Expected service life is 33 years without refueling.

The S9G Next Generation Reactor and associated components are expected to last the life of the ship. The core for the New Attack Submarine has increased energy density. This eliminates the need for a refueling, reduces life cycle costs, cut down the radiation exposure of shipyard workers, and lessen the amount of radioactive waste generated. The new reactor has increased energy density, and new plant components, such as the new concept steam generator, with improved corrosion resistance and reduced life-cycle costs.

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 higher power density decreases not only the size of the core, but also enhances quiet operation through the elimination of bulky control and pumping equipment. It would be superior to any Russian design from the perspective of noise reduction capability. The core for the New Attack Submarine was expected to last for the operational life of the ship. The design goals included eliminating the need for a refueling, will reduce life cycle costs, cut down the radiation exposure of shipyard staff, and lessen the amount of radioactive waste generated. The new reactor with increased energy density had new plant components, such as a new concept steam generator, with improved corrosion resistance and reduced life-cycle costs. This is possible because of many developments such as the use of advanced computers to perform three-dimensional nuclear, thermal, and structural calculations; further exploitation of a modified fuel process; and better understanding of various reactor technologies which permits more highly optimized designs. Performance improvements were gained through advances in such areas as thermal hydraulics and structural mechanics, and by optimizing reactor-to-systems interfaces.

A new concept steam generator alleviated the corrosion concerns encountered in existing designs of steam generators, while reducing component size and weight and providing greater flexibility in overall arrangement. The new steam generators 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.

The new steam generators allow greater plant design flexibility and decreased construction costs due to a smaller size, spatial orientation, and improved heat transfer efficiency which reduces coolant flow requirements. They alleviate the corrosion concerns encountered in existing designs of steam generators, while reducing component size and weight andproviding greater flexibility in the overall arrangement.