S5W Advanced Submarine Fleet Reactor (ASFR)
The S5W was a two-loop PWR rated at 78 MWt, with two vertical U-tube steam generators. The reactor compartment weighted about 650 tons. The reactor core life was improved significantly. The early S5W reactor on the HMS Dreadnought was reported to have a core life of about 5,500 equivalent full power hours. Later S5W cores had increased life; about 10,000 EFPH. The S5W plants often were refueled with the S3G core 3, with the same 78 MWt power rating and a core life of about 18,000 EFPH. The propulsion plant consisted of 1 x S5W reactor rated @ 78 MWt; 2 x main steam turbines delivering a combined 15,000 shaft horsepower (11.19 MW) to a single propeller. There was no separate S5W prototype. The S5W was used on 98 U.S. nuclear submarines of 8 classes and on the first British nuclear submarine, HMS Dreadnought, making it the most used Navy reactor design to date.
The first United States Navy submarine to be powered with the Westinghouse S5W design reactor was commissioned in 1959. USS Skipjack was the lead ship of the first class of nuclear-powered submarines built with the Albacore hull design, and also unique in that it was the first nuclear submarine with a single shaft. Placement of the bow planes on the sail greatly reduced flow noise at the bow-mounted sonar. Deep-diving and high speed capabilities were the result of HY-80 construction and a new reactor design, the S5W. This reactor became the US Navy's standard until the Los Angeles class joined the fleet in the mid-1970's.
Fuel life spans depend on how much the ship is operatee, and how accurately one can predict reactor performance. Current cores for the NIMITZ Class aircraft carrier, LOS ANGELES Class SSN, and OHIO Class SSBN last on average about 20 years.
The S5W reactor was used in the the SSBN 598, the first submarine that was to fire ballistic missiles from underwater was an extremely fast track project. When Perry C. Cooper, reviewed the previous assembly of that reactor design, in the SSN585, it occurred to him that time could saved if most of the reactor head assembly could be accomplished onshore rather than inside the submarine. The suggestion was accepted. Jigs were designed and the work accomplished. After explaining the technique to other shipyards, it became standard practice in the submarine industry. The procedures he wrote became a chapter in the NavShips manual for that reactor. The technique reduced the delivery time for that ship by four weeks, others delays excluded. The Project Manager later stated that the technique cut in half the cost of the reactor assembly.
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