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The S1W reactor was the first
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naval reactor used by the
United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...
to prove that the technology could be used for
electricity generation Electricity generation is the process of generating electric power from sources of primary energy. For electric utility, utilities in the electric power industry, it is the stage prior to its Electricity delivery, delivery (Electric power transm ...
and
propulsion Propulsion is the generation of force by any combination of pushing or pulling to modify the translational motion of an object, which is typically a rigid body (or an articulated rigid body) but may also concern a fluid. The term is derived from ...
on
submarine A submarine (often shortened to sub) is a watercraft capable of independent operation underwater. (It differs from a submersible, which has more limited underwater capability.) The term "submarine" is also sometimes used historically or infor ...
s. The designation of "S1W" stands for * S = Submarine platform * 1 = First generation
core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (laboratory), a highly specialized shared research resource * Core (manufacturing), used in casting and molding * Core (optical fiber ...
designed by the contractor * W = Westinghouse was the contracted designer and is a later Navy designation. During the plant's early years the project name was "Submarine Thermal Reactor" (STR) The land-based
nuclear reactor A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...
was built at the National Reactor Testing Station, later called Idaho National Engineering Laboratory near Arco, Idaho. The plant was the prototype for the power system of USS ''Nautilus'' (SSN-571), the world's first nuclear-powered submarine, which used the improved S2W reactor. The specific location within the vast Idaho National Laboratory where the S1W prototype was located was the Naval Reactors Facility.


Design

Under the leadership of Captain (later Admiral) Hyman G. Rickover, Naval Reactors followed a concurrent design strategy, with the design and construction of the S1W reactor taking place ahead of the design and construction of the ''Nautilus''. This enabled problems to be identified and resolved before they appeared in the shipboard plant. To better support this design process, the S1W power plant was built inside of a submarine hull. While the cramped spaces prevented engineers from obtaining information on some plant components, it provided a much more realistic example of how the shipboard plant would have to be constructed.


Operation

The S1W was a
pressurized water reactor A pressurized water reactor (PWR) is a type of light-water nuclear reactor. PWRs constitute the large majority of the world's nuclear power plants (with notable exceptions being the UK, Japan, India and Canada). In a PWR, water is used both as ...
that utilized water as the
coolant A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corr ...
and
neutron moderator In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, ideally without capturing any, leaving them as thermal neutrons with only minimal (thermal) kinetic energy. These thermal neutrons are immensely ...
in its primary system, and enriched
Uranium-235 Uranium-235 ( or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exists in nat ...
in its fuel elements. The S1W reactor reached criticality on March 30, 1953. In May of that year, it began power operations, performing a 100-hour run that simulated a submerged voyage from the east coast of the
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to
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. This test run clearly demonstrated the revolutionary impact that nuclear propulsion would have upon the submarine, which prior to that time was greatly limited in its ability to conduct continuous underwater operations by battery life and by the
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
requirement of diesel propulsion systems. The heated, pressurized water of the S1W reactor power plant was circulated through heat exchangers in order to generate high pressure
saturated steam Steam is water vapor, often mixed with air or an aerosol of liquid water droplets. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization. Saturated or superheated steam is ...
in a separate water loop. This saturated steam powered steam turbines for propulsion and generation of electricity. These facilities were constructed inside an elevated hull simulating the engineering portion of the ''Nautilus'' hull. A single propeller was simulated through use of a water brake. Large, exterior water
spray pond A spray pond is a reservoir in which warmed water (e.g. from a Power station, power plant) is cooled before reuse by spraying the warm water with nozzles into the cooler air. Cooling takes place by exchange of heat with the ambient air, involving ...
s were used to dissipate the heat energy created in the facility into the air. Following the commissioning of the USS ''Nautilus'', the S1W plant was operated to support plant testing and training of operators. Trainees were graduates of the
Naval Nuclear Power School The Nuclear Power School (NPS) is a technical training institution operated by the United States Navy in Goose Creek, South Carolina. It serves as a core component of the Navy’s program to prepare enlisted sailors, officers, and civilians emplo ...
in Bainbridge, MD, Mare Island, CA or Orlando, FL (all locations now closed). The course of study lasted six months and consisted of a combination of classroom and closely supervised practical training. In the mid-1960s, the S1W core was removed. An extension was bolted to the top of the reactor vessel so that a larger S5W reactor core could be installed. After that time the prototype was called S1W/S5W core 4. The new core was first taken
critical Critical or Critically may refer to: *Critical, or critical but stable, medical states **Critical, or intensive care medicine * Critical juncture, a discontinuous change studied in the social sciences. *Critical Software, a company specializing i ...
in late summer of 1967. In order to use the additional power generated by the S5W reactor, additional facilities were added in order to dump the excess steam when the plant was operated at higher power levels. These steam dumps were constructed in the same building, but outside the mock submarine hull. The S1W/S5W plant was shut down permanently in 1989 (October 17).Bettis Atomic Power Laboratory
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References

* Hewlett, Richard G. and Francis Duncan. ''Nuclear Navy: 1946-1962''. Chicago: The University of Chicago Press, 1974.
''Nuclear Propulsion''
by the Federation of American Scientists, Retrieved: 18 March 2005.


External links

* Stacy, Susan M (2000). "Proving the Principle, A History of The Idaho National Engineering and Environmental Laboratory, 1949-1999", (Chapter 10


S1W-related items in the Naval Reactors History Database
{{United States Naval reactor United States naval reactors Pressurized water reactors