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The AlW plant at the Naval Reactors Facility in Idaho, the land-basd prototype for the A2W used on the CVN-65 Enterprise, the first nuclear-powered aircraft carrier, was placed in standby in 1994. The A1W (Aircraft carrier, 1st prototype, Westinghouse) plant consisted of a pair of prototype reactors for the USS Enterprise nuclear-powered aircraft carrier. The PWRs designated A and B, were built within a portion of a steel hull. The plant simulated the Enterprises engine room, which would have four such pairs. The A1W plant was the first in which two reactors powered one ship propeller shaft through a single geared turbine propulsion unit. A1W was the first nuclear powered surface ship prototype. The plant was built as a prototype for the aircraft carrier USS ENTERPRISE (CVN 65), which was .

By September of 1954, the Navy and AEC officials (prodded relentlessly by then-Captain Hyman G. Rickover) were convinced that nuclear propulsion was feasible, and authorized design of an engine room section of a large surface ship [LSR]. Powered by two of the largest reactors then in development (but still unproven), a single shaft output of some 70,000 SHP was specified. This arrangement was obviously intended to represent the nuclear powered equivalent of the enormous energy generated by one-fourth of a conventional FORRESTAL-Class carriers propulsion plant complex.

The STR was redesigned as the first generation submarine reactor S1W, which reached criticality on March 30, 1953, was the prototype of the USS Nautilus (SSN 571) reactor and was followed in the middle to late 1950s by the Aircraft carrier reactor A1W, the prototype for the aircraft carrier USS Enterprise plant. Westinghouse's Bettis Atomic Power Laboratory was assigned the responsibility for operating the reactor it had designed and built, hence the W in the name.

Like the NAUTILUS Prototype (S1W) and numerous AEC experimental reactors, the LSR Project was built at the NRTS on the high desert plains of Idaho. LSR was also officially known as prototype-ship-on-land and technically designated as A1W (denoting the first model of aircraft carrier reactor, of Westinghouse design). A1W was the official title most frequently used in correspondence.

Design studies by Westinghouse and Newport News Shipbuilding progressed quickly, and by October of 1955, construction of A1W was authorized at an estimated cost of $26 million. Repeating the very successful practice pioneered during submarine reactor development, the much larger, dual reactor prototype was required to faithfully replicate actual shipboard conditions.

These stringent criteria offered three significant advantages: (1) no major changes for ship application would be necessary following successful prototype operation, (2) construction of the first nuclear powered aircraft carrier could be initiated well in advance of prototype completion, and (3) the prototype could then be utilized for the practical training and qualification of personnel.

Prefabricated under controlled shipyard conditions, the largest units that could be shipped by rail were transported over two thousand miles for field installation. The keel section for A1W (a double bottom sub-assembly prefabricated at NNS) was put into place with scant ceremony in June 1956.

Power operation of the A1W plant started in October 1958. The prototype provided realistic training for the students in an environment nearly identical to what they would encounter within an actual carrier. A1W was the first nuclear propulsion plant to have two reactors powering one ship propeller shaft through a single-geared turbine propulsion unit. Over the life of the plant, new cores and equipment replaced many of the original A1W components.

In the A1W and A2W designs, the coolant was kept at a temperature between 525-545 F or 274-285 C. In the steam generators, the water from the feed system is converted to steam at 535 F or 279 C and a pressure of about 600 psi or 4 MPa. The reactor coolant water was circulated by four large electric pumps for each reactor. The steam was directed from each steam generator to a common header, where the steam is then sent to the main engine, electrical generators, aircraft catapult system, and various auxiliaries. The main propulsion turbines are double ended, with the steam entering at the center and divides into two opposing streams. The main shaft was coupled to a reduction gear where the high rotational speed of the turbine shaft is stepped down to a lower rate rotational usable for ship propulsion.

Lessons learned in design and construction, and later in testing and initial operations were quickly applied to the ENTERPRISE reactor plants; designated as A2W and already under construction at Newport News. Big Es keel was laid well before the first A1W initial criticality, and the ship was christened just one year after prototype full power operation commenced. The practice of providing barely enough time between schedules to physically factor in desired design changes. As a result, ENTERPRISE was completed in 1961; years sooner than would have been possible if a more conventional series-style sequence had been applied.

As the Navy program evolved, new reactor cores and equipment replaced many of the original components. The Navy trained naval personnel at the A1W plant and continued a test program to improve and further develop its operational flexibility. The Ship in the Desert then became primarily a training facility, providing a hands-on shipboard machinery space environment for thousands of aspiring Navy Nucs. Despite very high standards and the challenging conditions at A1W, approximately 80% of all trainees at A1W became nuclear qualified. The remaining 20% suffered the ignoble and career-restricting stigma of becoming disenrolled from the navys nuclear program. On January 26, 1994, the A1W prototype plant was shut down after more than 35 years of successful testing and training activities. More than 14,500 Navy and civilian students were trained at A1W during the 35 years of operation.

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