Technical Specifications for Marad Design 

P2-N1-MA40a

NS Savannah

Pioneer in Commercial Nuclear Ship

From Marine Engineering / Log, August 1962

In undertaking the pioneering NS Savannah project, the naval archi­tects, George G. Sharp, Inc., confronted many new and interesting problems in addition to the large number of complexities usually involved in ship design. The Savannah was to lead the way in nuclear pro­pulsion for commercial ships and she was also to carry the image of peace and progress throughout the world. Safety was paramount and first consideration was given to the location and protection of the reactor. This involved studies of weight distribution and special structural design including a new protective anticollision barrier, and suitably locating and designing the superstructure. All of the design features were carefully coordinated to produce the unique and distinctive profile which has now become the identifying feature of the Savannah.

Basic Design Considerations

In developing the basic arrangement of a passenger-cargo ship, it is normal practice to locate the super­structure and passenger accommodations over the machinery spaces and stores hold, so that the cargo holds may be fitted with overhead cargo gear. However, the nuclear powered ship includes one blind hold, served by sideports and elevators, which resulted from the space requirements for the machinery and considerations of refueling. The total machinery compartment's length is greater for this nuclear powered ship than for a conventionally powered ship due to the length of the containment vessel housing the reactor, steam gen­erators, and associated equipment. However, stores spaces are provided outboard of the containment vessel in the reactor compartment, whereas in a conventional ship, a separate hold would be provided for this purpose, that there is little difference in total length of machinery space plus stores space. Refueling the reactor requires access suitable for handling heavy weights, resulting in the selection of an overhead system. It was also desirable to keep this access as low as possible because of the same weight and size considerations; therefore, placing the superstructure over the reactor access was avoided. This resulted in the superstructure being aft of the reactor hatch, and extending over a cargo hold aft. From an arrangement standpoint, it was necessary to place the reactor and containment vessel forward of the engine space because of size and stability considerations. It was too big to go above the propeller shafting without protruding through the main deck, and the increase in vertical center could not be tolerated. The containment vessel has its long dimen­sion fore and aft because of safety considerations, and because it resulted in better utilization of space. The location of the machinery and reactor with relation to midship was selected after considerable studv. For this design, the nuclear machinery plus shielding is roughly equivalent in weight to conventional machinery plus fuel. Therefore, a variable and movable weight (fuel) is replaced bv a constant fixed weight, so that it was desirable to locate the machinery so that the ship in the fully loaded condition would have essentially even-keel trim, and in the empty condition would trim by the stern. The results of these studies indicated some flexibility in the location was permissible if some attention was paid to cargo stowage in full-load condition and ballast distribution in light condition. It is considered that satisfactory operating conditions would be achieved with the machinery from 55-ft further forward to 40-ft further aft; however, the location selected pro­vides good trim with minimum bal­lasting, and a good cargo hold ar­rangement. Seven cargo holds were selected on the basis of hold size and cargo gear arrangement, although a six hold ar­rangement is possible from a flood-able length and damaged stability standpoint.

The Savannah is a single-screw, passenger-cargo ship with an over-all length of 595 ft 6 in. She has a molded beam of 78 ft and her design draft is 29-ft 6 in. when fully loaded. Total displacement at this draft is approximately 22,000 tons. She was built by New York Shipbuilding Corp. Her cruising speed is 21 knots, developed with a normal output of 20,-000 shp. She is essentially a shelterdeck vessel of advanced design, with a raked stem and a modified cruiser stern. The ship will carry 60 passengers, a crew of 110, and about 10,000 tons of dry cargo. The vessel is fitted with three complete decks. Ten main transverse, watertight bulkheads divide the ship into 11 thwart-ship compartments. The hull is built on a transverse fram­ing system except for the inner-bot­tom, which is a combination of transverse and longitudinal framing especially stiffened in the reactor area to provide positive protection to the nuclear steam plant in case of ship collision. The vessel meets a two-compartment standard of subdivision at a draft of 29 ft 6 in. With its modern sweeping lines, the Savannah presents a most at­tractive profile. Her teardrop-shaped superstructure is set sufficiently aft to enhance the vessel's foresection, which tapers to its well-raked bow. This expanse of deck accommodates hatch openings for Nos. 1, 2, 3 and 4 cargo holds, which will be served by two sets of cargo gear support trusses and their eight attendant 10-ton booms and cargo-handling gear. The cargo gear has been specially de­signed for the Savannah. It is the lightest yet developed for the modified Ebel rig and fitted for extremely rapid handling of cargo. Immediately aft of No. 4 cargo hold and forward of the wheel house, another hatch is located to provide access to the reactor space. Aft, the superstructure step down to a generous expanse of deck at the Promenade and A Deck levels. One set of support trusses equipped with four 10-ton booms serves No. 6 and No. 7 cargo holds. Cargo hatch covers are set in coamings on A Deck and are of the flush closing type on B and C Decks. All hatch covers, ex­cept for two non-tight, lift-off pontoon covers on the cargo deep tanks in No. 6 hold, are hydraulically operated from local stations at each hatch. The vessel has one additional   cargo hold, No. 5, which is served by side ports exclusively. The Navigating Bridge Deck, the uppermost deck serves a dual pur­pose. The forward end is given over to the pilot house with tbe radio room on the starboard side and chartroom on the port side outboard of the gyrocompass housing. The balance of this deck includes living quarters for three radio operators and two cadets as well as space for the fan rooms, a battery room and the emergency generator room. The pilot house is completely outfitted with the latest navigation and communication equipment. Dominating the area is the control console, housing all conventional wheelhouse instrumentation. It is situated well forward and on the centerline. The magnetic compass is of the reflecting type, the first to be manufactured in this country. On either side of the steering stand there is installed the latest type of RCA navigational radars, utilizing "true-motion" presentation of data. Another important unit in the wheel house is the control console for the Sperry anti-roll stabilizers, which will be located on the port and starboard sides amidship. The fins are operated hydraulically by a gyro system capable of sensing sea conditions and providing the counter-measure for reduction of the roll. Each fin has a lift of approximately 70 tons at 20 knots. Melerological instruments for recording sea-water temperature, atmospheric pressure, wind direction and velocity, humidity, and air temperature are incorporated into the vessel making her a veritable floating weather station. A special radio facsimile receiver will make it possible to receive worldwide weather-map transmissions at sea from the U.S. Weather Bureau in Washington, D.C. The Boat Deck, the next uppermost deck, is devoted entirely to officer's accommodations. A spacious officer's lounge aft affords observation on either side of the ship as well as overlooking the passenger recreation area. The Promenade Deck is devoted exclusively to public rooms and spaces. A "walk-around," connecting port and starboard promenades, features a series of Kearfott windows made of Polaroid glass permitting an unobstructed yet sheltered forward view of the sea. Just behind this walkway is the Main Lounge, which can be closed off from the adjacent writing and card rooms by folding screens. The Lounge is equipped with projection equipment for motion pictures, as well as with closed-circuit television viewing of the reactor spaces. The after end of the Promenade deck structure in­cludes the Veranda and Cocktail Bar. Sliding glass doors open onto the swimming pool. The remaining deck space on this level is utilized as ship­board game area. A Deck contains the Main Lobby, 30 spacious passenger staterooms and accommodations for the purser, stew­ard, doctor and nurse. The ship's hospital and dispensary are also located on this level, as is the health-physics laboratory. In keeping with the modernity of its nuclear propul­sion system, a modern decor is car­ried out in all of the passenger staterooms and public areas, utilizing materials which are functional as well as decorative. All of the public areas on the ship, the passenger staterooms and the passenger's dining room are completely air conditioned. B Deck is devoted to the Main Dining Room and galley spaces. Quarters for crew are located on the starboard side, outboard. Crew lounges and mess facilities are on the port side, outboard. C Deck contains additional crew quarters, mainly laundry and butcher shop. Also located on this deck is a glassed-in viewing gallery around the engine room casing to permit passengers and visitors to observe the main engine room and reactor-control room. The vessel is equipped with five Otis elevators. One 2,000-lb passenger elevator from the Boat Deck to C Deck with all stops; two 2,000-lb cargo elevators; and two 2,000-lb stores elevators.

Heavy  Hull  Structure

The hull is built on a conventional transverse framing system except for the inner-bottom. The inner-bottom, below the reactor space, is "egg crated" with transverse floors at every frame, and a deep vertical keel and many keelsons in the fore-and-aft di­rection. In addition to this great streng.h in the inner-bottom, there are two heavy longitudinal collision bulk­heads (21 ft-9 in. off centerline on the pert and starboard sides) adjoin­ing the reactor space. Outboard of the collision bulkheads, B, C and D Decks have heavier-than-normal plat­ing, continuously welded to the beams. Inboard of these bulkheads are collision mats, extending between C Deck and the 14 ft flat for a length of 35 ft adjacent to the central por­tion of the containment vessel.

Hatch Covers

The cargo hatches on A Deck are fitted with MacGregor hydraulic cov­ers of several types. Hold No. 1 has a 3-panel cover and Holds 2, 3 and 4 have 4-panel covers. All are actuated by direct-connected hydraulic cylin­ders, trunion-mounted at center hinges external to the hatch openings. The hydraulic actuator for each pair of panels is housed in a small enclosure off the hatch end, and is made water­tight by the cover sealing arrange­ment. Hold No. 6, Promenade Deck, is fitted with a flush, watertight 4-panel cover, mastic-surfaced to fulfill its function as part of the promenade area. Hold 7, A Deck, is fitted with a 6-panel watertight cover on a raised coaming. The covers on Holds 6 and 7 are actuated by hydraulic cylinders and linkages integrally mounted with­in the cover. All hatch covers on B Deck are flush, watertight design—a require­ment occasioned by the Savannah's classification as a shelter-deck vessel. Covers on C and D Decks are flush, non-tight construction, of 4-panel and 6-panel arrangements. All 'tween deck covers are actuated by hydraulic cyl­inders and linkages integrally mounted within the covers. Hatch-cover control stations are located adjacent to each opening at each deck level. These are in such position that the operator at each sta­tion can observe the movement of the cover being actuated. The Savannah has some of the most modern cargo-handling gear available. In lieu of the normal king­posts, she has a tubular rigid frame structure for the 10-ton booms. This is the lightest structure yet designed for Ebel-rigged booms. The rig makes it possible for one or two deckhands to unstow and position all booms on the ship for cargo operations in less than an hour. The shifting of booms from inshore to offshore operation during loading can be accomplished in one or two minutes by the winch operator without moving from his station. An inherent safety condition in this system makes the rig refuse to lift a load if tension in the falls tends to exceed a safe limit. Four Welin aluminum lifeboats hung from steel gravity davits. One boat is hand-propelled, another is motor-propelled and two are oar-pro­pelled. They have a total capacity of 190 persons. The ship is equipped with two 12,000-pound Baldt "Snug Stowing" steel bower anchors, and one 12,000-pound spare anchor. Each bower an­chor is furnished with 165 fathoms of 2.5 in. Baldt cast-steel stud link chain. The American Engineering steering gear is a four-cyl, electro-hydraulic ram type driving the crosshead through a Rapson slide. Two indepen­dent power plants are capable of handling the rudder with a maximum torque requirement of about 7,000,-000-in-lb. The rudder is a balanced, streamline spade type capable of turn­ing hard over 38 deg port and star­board.

Air Conditioning

Typical of the way in which the Savannah has served as a chal­lenge for simplified construction and maintenance is the air conditioning installation. Standard refrigeration equipment a Carrier 17M centrifugal machine with open-type compressor, condenser, motor and gear—forms the heart of the air conditioning system. Carrier 36N Conduit Weathermasters are installed in passenger and crew cabins as part of the high-velocity system. More than 1,300 ft of spiral con­duit pipe for air distribution are in­stalled. The total weight of 4,140 lb for the high-pressure ductwork sys­tem is about one eighth of what would be required for a conventional-type, low-pressure installation. Of this weight, the Carrier Spira-Pipe ac­counts for 2,900 lb and the balance is for connectors and fittings. The Spira-Pipe, produced by a new machine developed by Carrier, re­quires only one-quarter of the space used by conventional ducts. It is more flexible for installation, particularly where elbow bends and other fittings are required. Installation was speeded by supplying the spiral conduit in 12-ft prefabricated sections. These were cut to required lengths on the job. The Carrier Weathermaster units, which provide individual room tem­perature control, are concealed above the hung ceiling. For this type of in­stallation, without diffusers the air is distributed into the room through perforations in the ceiling New York Shipbuilding engineers designed spe­cial casings of galvanized steel. The Spiratube flexible tubing has a high-carbon spring steel wire helix covered with overlapping plies of a nylon fabric coated with du Pont neo-prene synthetic rubber. This makes the ducts highly resistant to wear, corrosion and mildew. To protect personnel and passengers from noise and to protect the ship itself from deleterious wear-and-tear caused by vibration, the 18 one-to 50-hp fan motors, designed and provided by the Buffalo Forge Com­pany for the ventilation and air con­ditioning system, had to be mounted on the most modern type of vibration and noise isolation devices. To minimize the centrifugal fan noise and motor vibration, Buffalo Forge used steel spring vibration iso­lators, manufactured by the Korfund Dynamics Corporation. Korfund, which specialized in designing and manufacturing devices for the control and measurement of vibration, shock and noise, makes the only steel spring isolators that have been approved by the Maritime Commission.

Marine Hazards

The usual marine hazards of storm, fire, grounding, flooding, and sinking have been considered in relation to the nuclear plant. The fire hazard in the engine room is less for the nuclear ship due to general reduction in oil piping and hot surfaces, and the normal absence of oil fires in boilers. It is considered that grounding in way of the reactor hold, and possible flooding of this space will not cause penetration and flooding of the con­tainment vessel. The principal design problems have concerned collision and sinking. It is obvious that a first consideration was to locate the reactor in the ship at the spot least subject to collision damage. In order to obtain information such as this, an extensive study of marine accidents was undertaken. In particu­lar, ship collisions were carefully re­viewed and methods developed to predict structural damage to vessels struck in collision as a function of speed and displacement of the vessels involved. On the basis of the data obtained from these studies, the Savannah was designed to withstand, without damage to the nuclear reactor compartment, any collision with all but about one per cent of the world's merchant fleet. The probability of collision with a ship of this remaining one percent group is extremely low. Considering that the Savannah, as the first nu­clear-powered merchant ship will be handled with extreme care, the proba­bility of a dangerous release of radio­activity through collision is considered negligible. In particular, because large ships proceed at relatively low speeds in harbors, no collision of sufficient severity to damage the reactor compartment can take place in a harbor. Surrounding the reactor compart­ment are heavier-than-normal structural members. The inner-bottom, be­low the reactor space, is "egg crated" with transverse floors at every frame; and a deep vertical keel with more than the usual number of keelsons in the fore and aft direction add to this strengthening. Outboard of the reactor compartment there are two heavy longitudinal collision bulk­heads, and outboard of these bulk­heads there is heavier-than normal deck plating continuously welded to the beams. Inboard of the collision bulkheads are collision mats made up of alternate layers on one-inch steel and three-inch redwood lumber to a total thickness of 24 in. In the event of a collision broad­side to the reactor compartment, the ramming ship would have to pene­trate 17 ft of stiffened ship structure, two ft of collision mat, two ft of con­crete, and the reactor containment vessel, before actually reaching  the reactor plant. In case of sinking, provision has been made to allow for automatic flooding of the containment shell to prevent its collapse in deep waters. The flooding valves are designed to close upon pressure equalization so that containment integrity will be maintained even after sinking. Salvage connections have been installed to allow containment purging of filling with concrete in case of sinking in shallow water where recovery or im­mobilization of the reactor plant seems advisable.

Todd Will Service Ship

The Galveston, Tex., plant of Todd Shipyards Corporation has been des­ignated by the Maritime Administra­tion, U.S. Department of Commerce, as the central servicing site for the Savannah. Under a five-year contract with the Maritime Administration, Todd will handle the drydocking, repair, maintenance and refueling of the Savannah, as well as the operation and maintenance of the nuclear serv­ice vessel, the Atomic Servant. In addition to providing a servicing and maintenance base for the Savan­nah at the Galveston yard, Todd nu­clear engineers and technicians will have the same responsibilities and will be subject to call for servicing the ship anywhere in the world.

Power Plant Blends Radically New with the Tried and True

Prime contractor for the design and manufacture of the Savannah's nuclear power plant was the Babcock and Wilcox Company. B&W also supervised the installation and participated in the testing of the entire power plant. The steam turbines, reduction gear and main components of engineroom machinery were subcontracted to the De Laval Turbine Inc. The Savannah has been referred to as a floating laboratory because 6f the valuable operational data and experience she will furnish. Although the basic design and operating cri­teria for the nuclear propulsion sys­tem were fixed at the beginning, a number of significant improvements were incorporated in the plant as it was built. And further improvements may be incorporated as the ship gains operational experience. The reactor system is located amidships, between the bulkheads forming the reactor compartment. The major portion of this system, including the reactor with its primary loops, pres-surizer, steam generators, primary circulating pumps, air conditioning system and other auxiliary systems, will be enclosed in this compartment. Certain low-pressure reactor-system auxiliaries, such as the primary water demineralizers, charge pumps, drain tanks and a few other components are located just outside the containment vessel for reasons of better access and maintenance.

General Description

The Savannah's power plant con­sists of a reactor system and a propulsion system which are an integrated unit, different from conventional ships only in that the reactor replaces the ordinary oil-fired boiler. The pro­pulsion system is comprised of the main turbines and reduction gears, the main condensers, the feed water system, and the turbine generators. Auxiliary diesel generators and a package boiler will supply power when the reactor is shut down. The propulsion system is located in the machinery compartment just aft of the 66 reactor compartment and below the superstructure. The power plant control room is located at the rear of the machinery compartment on the D Deck level. The reactor system is composed of a pressurized-water reactor, a pres-surizer vessel, and two primary cool­ant loops. Each loop contains two canned motor pumps, one heat exchanger, two check valves, and two stop valves. The heat added to the primary coolant as it flows through the reactor is given up in the heat exchanger. Here the primary water generates low-quality steam that is led through risers to a steam drum directly above the heat exchanger. The moisture is removed in the steam drum and dry saturated steam led to the steam main.

Containment Vessel

All of the equipment in the reactor system is housed within a steel con­tainment vessel in the reactor space. Because of the weight of the reactor vessel and the various components associated with the reactor system, including approximately 2,000 tons of lead and concrete shielding, the reactor space has been located amidship, just forward of the machinery compartment. The containment vessel serves to prevent the escape of radioactive particles to the atmosphere in the event of an accident. The vessel is made up of a 35-ft-diam cylindrical section, with two hemispherical ends, and has an over-all length of 50 ft. A 14-ft-diam cupola is located on top of the cylindrical section. The control rod drives, which are mounted on the reactor vessel head, are housed within the cupola. The vessel has been designed to withstand a pressure of 186 psig. The wall thickness of the containment vessel varies from 2 in to almost 4 in. of carbon steel. The 186 psig is the pressure that would result from the rupture of a primary coolant pipe and the instantaneous release and expansion of the entire contents of the primary system, which is the maximum credible accident to the reactor plant. A total of 82 penetrations for piping, electrical cables, pneumatic lines, and access, are provided in the containment vessel shell. The largest penetration is the 14-ft-diam opening at the top of the cupola. This open­ing was used for initial installation of equipment within the containment vessel. In addition, it will be utilized for refueling the reactor core. Two 24 by 18-in. manholes in the lower portion of the vessel and two 42-in-diam manholes in the upper portion provide means of access to the containment vessel. Should the ship sink, the two lower manholes have been designed to open inwardly under an external head pressure of 100 ft of water. This feature allows flooding and prevents the collapse of the containment vessel in the event of sinking. The bottom half of the vessel rests in a cradle of steel surrounded by a Wall of reinforced concrete 4 ft thick, which forms the lower portion of the secondary shield. The top half of the containment vessel is encased in a 6-in. layer of lead plus a six-in. layer of polyethylene, which forms the up­per portion of the secondary shield. In addition, both sides of the vessel are protected by a thick collision mat, constructed of alternate layers of steel and redwood. Except when entry is required, the vessel will be sealed. If entry is required, it can be done 30 min after reactor shutdown. Entry into the containment vessel will be kept to a minimum, since the internal equipment that could be expected to require normal maintenance is installed in duplicate. In addition, certain segments of the reactor system can be isolated and bypassed without affecting plant operation. The containment air conditioning system continuously circulates and cools all of the air in the containment vessel, maintaining an average ambient temperature of 130 F and humidity of 72 percent. The design of the containment vessel follows the highest engineering standards, and was approved by the Coast Guard and the American Bureau of Ships.

Shielding

The main sources of radiation dur­ing operation of the Savannah's power plant are the reactor itself and the primary loop coolant water. This water, which passes through the re­actor core, is irradiated in the process and becomes a source of radiation. There are also radiation sources of lesser magnitude including process piping, hold-up tanks, pumps and demineralizers. By and large, these need not be considered in the design of the main shield, but must be considered during access and maintenance studies. The shield on the Savannah serves the dual purpose cf: (1) limiting the radiation dose  outside the containment to prescribed safe levels (2)  permitting, access to the interior of the containment vessel within 30 min after shutdown. In order to accomplish these functions the shield has been divided into a primary shield which surrounds the reactor itself, and the secondary shield, which surrounds the containment vessel. The primary shield consists of a water-filled tank surrounding the reactor, augmented by an outer lead annulus varying in thickness from 2 to 4 in. The tank is 17 ft high, with an annular water space of 33 in. The lead annulus is bonded to the outer wall of the tank. The primary shield is more than sufficient to limit the dose rate within the containment ves sel from core gamma sources and activated nuclei to 200 mrem/hr, ¹/₂ hr after the reactor has been shut down. This level will permit limited access of personnel to the containment vessel for maintenance and repair purposes. The secondary shield consists of lead, polyethylene, concrete and wa­ter of sufficient thickness to reduce reactor and coolant doses to allowable levels. The total weight of this sec­ondary shield is approximately 2,000 tons.

Reactor System

The Savannah's reactor is mod­erated and cooled by light water at 1,750 psia. It is fueled with uranium oxide (U0₂) of about 4.4 percent enrichment in uranium 235, clad in stainless steel rods. The reactor de­sign was aimed, primarily, at a long core lifetime; the design target was approximately 52,000 megawatt days, or 1,230 days at the average operating power. The active core is approximately a right circular cylinder with an equivalent diam of 62 in. and a height of 66 in. The core is made up of 32 fuel elements, each consisting of 164 fuel rods. Reactivity control is provided by 21 cruciform control rods. Each rod is a composite of a boron-stain­less steel jacketed with stainless steel plates. A multipass arrangement was se­lected because it possessed several advantages in thermal performance over a single-pass core. There are three passes. The first flow path is upward in the annuli between the vessel and the inner thermal shield; the second and third passes are through the core. In order to attain the long core life­time, a large, low power density core is used. The inclusion of uranium 238 as a fertile material extends the core life through its conversion to plutonium. A pressurized-water reactor system operates on the principle that water under high pressure can be treated to high temperature without boiling (primary loop). This heat is then transferred to water under much low­er pressure, causing it to turn to steam (secondary loop) to operate the turbines and produce power. In steady operation, the Savannah's reactor system will respond automatically to slight variations in steam demand at the turbine throttle by virtue of its negative temperature coefficient. For changes of power de­manded from the bridge, automatic control-rod operation will cause the reactor to respond without serious lag or deviation in its average coolant temperature. A graphic, color-coded display of the operation of the reac­tor system is provided on the main control panel.

Reactor Core and Fuel

Each of the core's 32 fuel elements is 8.5-in. square. The elements are confined within a stainless steel "egg-crate" type lattice. This lattice the equivalent of a pressure can around each element serves to withstand the pressure differentials that arise as a result of the multipass flow pattern. Each fuel element contains 164 rods. Each rod is 0.5-in. in diameter. The wall is 0.035-in-thick stainless steel. The fuel in the rod is uranium oxide pellets, enriched to an average of 4.4 percent of uranium 235. The uranium oxide pellets, 0.4255-in. in diameter, are made from pressed and sintered U0₂ powder. The space between the pellets and the inner tube wall contains helium gas under pressure to assure good heat transfer across the fuel rod. The gas is sealed in at the time the tube is loaded and the ends plugged. The initial core loading includes 6,788 kg. of U-238; the U-235 content, at the enrichments of 4.2 and 4.6 percent, is 312.4 kg. The conver­sion ratio is about 0.4; that is, for each gram of U-235 that is burned up, 0.4 grams of Pu-239 will be produced from the fertile material (U-238). The control rods will control reactivity in the range of 14 to 18 percent from cold starting to full power. This value includes an allowance for resonance capture of neutrons by the rods. This data would therefore indicate a margin of 2.8 percent for the cold clean core. Many factors are involved in estimating the core life, but all calculations to date conservatively indicate that at normal power, corresponding to 63.5 mw of heat, the core should have a life of over 700 normal power operating days. Based on operating 60 percent of the time at normal pow­er, and 40 percent at port power, it should not be necessary to reload the core for 3/2 years.

Control Rods and Drive

There are 21 control rods. The amount of heat generated by atomic fission in the reactor depends upon how far from the full down position the control rods are raised. The principle of operation is simple. When the rods are in the full down position, they absorb the neutrons emitted by the nuclear fuel. Raising the rods, in effect, is like raising a curtain from between the neutrons, thus permitting them to bombard surrounding fissionable uranium atoms and sustain the chain reaction necessary to pro­duce heat continuously. The higher the rods are raised, the greater the heat that is generated. Inversely, lowering the rods restricts the fissioning action and reduces the heat, and in the full down position shuts off the chain reaction entirely. Dropping all rods quickly and simultaneously to the full down position is called "scramming." Each rod is in the shape of a cru­ciform, and each is equipped with an electro-mechanical control, plus a hydraulic cylinder for reactor scram. All drive rods are buffer-sealed where they pass through the reactor head, and each seal is charged with purified water at 1,800 psi pressure. In the event of failure, a seal can be iso­ated from the system. Each control-rod drive assembly can be disconnected from its control rod and removed. Each rod measures 8 in. across, tip to tip, and is 0.375-in-thick. The effective length of each rod is 66-in. Construction consists of a 3/16-in-thick plate of boron stainless steel sandwiched between two 3/32-in-thick stainless steel plates. It is the boron that restricts the atomic-fission process, and provides control. Positioning and motion of the rod is accomplished by the combined use of an electromechanical drive unit and hydraulic pressure. The hydraulic pressure necessary for a scram is maintained continuously in a scram accumulator. Each rod has its own accumulator, and each of these acts independently of the others. The scram pressure is held in check by a pilot-operated scram valve. By release of the pilot pressure, the full scram accumulator pressure is applied to the piston. This results in a net downward force on the rod drive line sufficient to accelerate the rod into the core at the required rate for scram shutdown.

Engine-Room Machinery

De Laval Turbine Inc. supplied the main components of the engineroom machinery under a subcontract from The Babcock and Wilcox Company, the prime contractor for the complete nuclear propulsion plant. The engineroom equipment consists of the main propulsion turbines, main reduction gears, turbine-generators, main and auxiliary condensers, feedwater heaters and pumps, and associated accessories. Certain components of this equip­ment were subcontracted by De Laval. The main propulsion unit, designed and manufactured by De Laval, is essentially the same type as used in normal steam-turbine-driven ships. However, the design for the Savannah presented unique problems because of the special conditions surrounding the requirements for the first nuclear surface vessel. The main propulsion unit is a cross-compound turbine, double-reduction gear unit of nearly conventional design developing a normal horsepower of 20,000 at 107 rpm, with a maximum continuous-duty rating of 22,000 hp at 110 rpm. The high-pressure turbine consists of nine stages, all single-row wheels, and is of the impulse type. The casing is split on the horizontal plane and' the bucket wheels are integral with the rotor. Diaphragms 2 to 5 are mounted in an inner wheel case. At normal power, the high-pressure turbine will operate at approximately 4,500 rpm. The low-pressure turbine contains both the ahead and the astern turbine. The ahead turbine comprises seven single rows of impulse-type blading. The astern turbine consists of two impulse stages, the first stage being a two-row and the second stage a single-row wheel. The casing also is split on the horizontal plane and the ahead steam inlet and exhaust outlet are in the lower half of the casing, while the astern steam inlet is on top of the exhaust belt with an internal expansion joint. The last two ahead stages and the last astern stage are integral with the rotor, the other stages are of the built-up type. At normal power the low-pressure turbine will operate at approximately 3,000 rpm. The main reduction gear is a double-helical, double-reduction, articulated type, with the first reduction forward of the second. The low-speed pinions are driven by quill shafts from the high-speed gears. The turn­ing gear is located at the after end of the low-pressure high-speed pinion. The bull-gear diam at the pitch circle is approximately 176.6 in. and the overall ratios are 42.3:1 on the high-pressure side and 28:1 on the low-pressure side. The bull gear is located axially by a 45-in. Kingsbury thrust bearing at the after end of the gear case, with a separate thrust shaft between the main gear shaft and the line shaft. The steam conditions for this unit can vary from approximately 430 psia to over 700 psia, with the higher pressure for the lower loads. The design steam conditions at normal power are 465 psig and 463 F; at maximum load 445 psig and 475 F, with a condenser vacuum of 28/2 in. The steam conditions for the Savannah necessitate certain deviations from what might be called a conventional design of a turbine of this size: At a design full-power condition, the mois­ture content at the high-pressure tur­bine exhaust is approximately 11-12 percent. In the H-P turbine from the sixth stage  on,  therefore,  moisture-collecting provisions which drain the mois­ture to the exhaust belt have been included in the diaphragm design. After the steam leaves the moisture separator, it is essentially in the sat­urated condition and then enters the L-P turbine. Moisture-collecting pro­visions are included on all but the first stage of the ahead low-pressure turbine. Drain nozzles are fitted to all diaphragms to allow the moisture to go to the drain connection or to the exhaust. The condenser design also provides a method of isolating the tube-end sections, if excessive saline contami­nation of condensate results from im­proper attachment of tube to tube sheet, and/or tube-end failure. Under normal conditions of operation, all of the surface is effective. When con­tamination is indicated by a detecting device, it is possible, by means of the use of close support plates and a col­lecting well, to effectively isolate the ends of the condenser and through a contaminated drain system, prevent the contaminated water from entering the feedwater system. The main con­denser is single-pass with scoop in­jection for normal operation and a cir­culating pump for stand-by and ma­neuvering. The auxiliary condensers, however, are of the two-pass type. The Savannah contains two 1,500-kw De Laval turbine-generator sets. The driving turbine is of the impulse type with eight stages and is designed for steam ranging from 430 psia to over 700 psia, dry and saturated. A De Laval-Stoeckicht size 16 planetary gear with an input speed of 5,600 rpm and an output rpm of 1,200 is connected rigidly to the tur­bine and generator shafts. The use of planetary gears allows considerable space saving, which was quite impor­tant to the engine-room arrangement. The generators, manufactured by General Electric Company, are 440-volt, 60-cycle, 3-phase, totally en­closed, self-ventilated with a direct-connected amplidyne exciter. There were very few deviations from standard practice in the remain­ing equipment, apart from those ne­cessitated by the varying steam con­ditions, which influence the feed­pump turbine design and control. Also, no cast iron was used in the construction of the machinery. Prime objective in the basic design of the Savannah power plant was a reliable installation, rather than one which would give the utmost in fuel economy. For the future, progress will be made in the design of reactors, as well as the more conventional equipment still necessary as an impor­tant part of the complete propulsion plant of a nuclear vessel.

Electric Plant

The electric system that supplies power to the reactor and its auxiliaries is designed to provide a high degree of reliability to assure reactor safety during all phases of operation, includ­ing periods of shutdown. The system consists of the protective devices, con­tainment wiring, and all metering, in­terlocking and alarms associated with electric loads for the reactor system. Power for the system normally is sup­plied by two DeLaval/GE turbine-generators, each rated at 1,500 kw, 450 volts, 3 phase,  60 cycles. In addition, two auxiliary 750-kw diesel-driven generator sets are in­stalled in the engine room. These pro­vide power to the main bus for operating those loads required in supply­ing decay heat cooling to the reactor after a scram shutdown. They also provide emergency "take home" power in the event of failure of the nuclear power plant, provide power for reactor start-up and provide spare generating capacity for normal operation in case of failure of a main turbine-generator. During normal operation, the two auxiliary diesel generators will be on standby. In the event of a reactor scram or emergency, these diesel generators will be started automatically and synchronized on the main bus, which, in turn, will supply and distribute power to the components required for reactor cooling. Since the capacity of each diesel generator is adequate to furnish power for decay heat removal and an additional limited amount of lighting and ship services, an emergency condition will not arise if either diesel fails in starting. A 300-kw emergency diesel generator also is provided. It is installed top­side and will suply power to the 450-volt emergency switchboard. This source will provide power during an emergency in which both the main turbine-generators and the auxiliary diesel generators are inoperable. Loads such as emergency lighting, the low-speed windings of the primary coolant pumps, and the emergency cooling system will be connected to the emergency switchboard. This generator can be started from the main control room. The main switchboard is divided into two separate sections interconnected by a bus tie with a circuit breaker that normally is closed. The generator units of each section, one turbo and one diesel, are arranged so that they are next to each other at the center of the switchboard to facilitate paralleling and general operation.

Interior Decor Epitomizes Advanced Design

The Savannah's several roles as pioneer ship of the atomic age, trav­eling exhibit of industry, art and cul­ture and world-circling ambassador of good will, posed new problems and her interiors, designed by Jack Heaney & Associates, differ significantly from other ships afloat. She accommodates 60 passengers, but her public rooms are scaled to the grander job of re­ceiving the large groups who will visit her as she proceeds on her mission around the world. In general appearance and in detail, the interior of the Savannah epito­mize her advanced design. Yet, for the sake of the timorous passenger, reminders of the ship's atomic plant were expressed with restraint. The main entrance lobby will present an exposition contributed by United States industry, indicative of further horizcns in science, medicine and pro­duction. This impression is reiterated in the vessel's own fittings and furnish­ings that help to tell America's story. A wide variety of materials and products have been incorporated into the interiors, sometimes in unusual ways. Metals are given new jobs, new faces, new form. Large sheets of tex­tured aluminum are color-anodized in blues, greens and golden beige to pan­el the bulkheads of the main stairwell. Stainless steel turns decorative and is formed into stateroom furniture. Plas­tics find ever-increasing uses, range from soft "poly" foams to fill uphol­stered chairs and vinyls to cover them, to porcelain-hard epoxy for color coatings on walls and ceilings. Products of industry's genius are evident. Entire table tops, around the dance floor, are actually lamps that light up with the color glow of electro­luminescence. A closed-circuit televi­sion projector will show large audi­ences the nuclear reactor in operation. Those who inspect the Savannah in foreign ports will be aware of her, however, not only as a scientific achievement, but also as a traveling showcase of American creative talent. Spacious lounge areas with ceilings higher than common to ships of this size flow fore and aft along the Prom­enade Deck, uninterrupted by doors. Particularly unusual aboard ship is the art exhibit, a representative collection of American painting and sculpture borrowed from galleries and the artists themselves. A new show will be pre­sented on each trip. In lounges, dining rooms and stairways, the ship will dis­play her own varied examples of art and design, sculpture and a three dimensional mural. Original prints, woodcuts, etchings, abstract color pho­tography and ceramics hang in the passenger and officers' staterooms. The Main Lounge, surrounded with floor-to-ceiling windows on three sides, will be used for formal receptions, passenger recreation and relaxation and a movie and TV auditorium. It also will double as art gallery and its decor is cued to this use. Adjacent Writing and Card Rooms extend the space devoted to showing the borrowed paintings. A strong piece of abstract sculp­ture in steel and concrete, "Atomic Freedom", is part of the ship's perma­nent collection. Secured to the aft wall of the library, it forms a focal point at the end if a long corridor leading to the Veranda. A combined cabana, cocktail lounge and night club, the Veranda overlooks the swimming pool and recreation deck through a sloping window wall. The room is carefree, open and light in feeling to suit daytime gatherings as well as evening festivity. Its walls are patterned with circles, excised from the morinite panels in one area and appliqued on the bulkheads in another. Over the back bar, a stainless s^eel honey-comb for wine bottles has been given a free form outline, in­spired by a chart of the nuclides. In another corner a gay novelty shop will purvey U.S. wares, luxuries and necessities to the passengers and souvenirs to the ship's guests. Amidships, the main stair and passenger elevator provide access to the Dining Room and staterooms on the decks below. Centered in the well of the stairs, a tall monel and nickel-silver sculpture by Jean Woodham reaches upward, to express the spirit of progress in which the Savannah was conceived. The passenger Dining Room is fo­cused around Pierre Bourdelle's all-white sculptured mural, "Fission", which forms a hyperboloid at the aft end of the room behind the captain's table. A glass screen at the room's en­trance supports a gold-plated model of the original Savannah, the first to use steam power in crossing the Atlantic. The Dining Room color scheme is red, white and blue. On A Deck, the Main Lobby is the business and reception center of the ship. Here are the purser's counter and office. Here, too, are the exhibits provided by business and industry to introduce to the public scientific de­velopments. On the walls of the ship's entrances, port and starboard, Koda-chrome transparencies are set in box frames with concealed illumination. Eastman Kodak has presented the Savannah with a library of photos offering a broad selection of United States scenics and assorted Americana for a revolving display. Adjacent to the lobby are 30 state­rooms arranged for single, double or three-passenger accommodations. Four rooms convert to suites. With the com­fort and peace of mind of the occu­pants as prime consideration, the de­cor is muted and relaxing, but not lacking in interesting detail. The four basic schemes have been varied in ar­rangement, furnishings and decoration so that there is almost no side-by-side duplication. Fine original prints, the work of nine different American ar­tists, stimulate interest in many of the rooms. All living spaces aboard the Savan­nah are fully air conditioned. Indi­vidually controlled systems for heating and cool air are mounted in the ceil­ings of each stateroom. Room thermo­stats will permit passengers to adjust the temperatures to personal prefer­ences. Every stateroom also has pri­vate toilet and shower or bath tub. Crane's Criterion sanitary fixtures were selected in color to enliven the pas­senger bathrooms. Furniture encompasses a range of materials limited only by the require­ments of incombustibility in its con­struction. Basic frames are either of steel or aluminum and both metals are used for decorative effect. Dressers and other case furniture are formed in rigidized stainless steel, paint-filled for color and rubbed to highlight the strong character of the metal. Many of the steel cases are surfaced on all sides with melamine plastic laminates. Several Veranda tables are topped with metal mosaic combined with plastic; others are of colored alumi­num with natural etched motifs. Card tables   are   polished resin and green marble chip. An 8-ft oval of Vermont white statuary marble is used for one table in the  Lounge. This same room also boasts two 30-in-diam coffee tables sliced from petrified wood. Through the Petrified Forest National Monument in Arizona, which owns and is responsible for the conservation of all petrified wood, it was arranged that the Savannah might have among her appointments a fine specimen of this fascinating and beautiful material. A particularly promising and colorful "log" was selected and shipped to a marble-cutter in New York. Here it was divided into two slabs and its ex­tremely hard surface given a high polish, but the natural contours of the perimeter preserved. During this process all trimmings and scrap had to be reclaimed and returned to the National Park Service, U.S. Depart­ment of the Interior, to whom the actual tables always will belong. The marine joiner bulkheading, was given added dimension at every opportunity with applied texture in metal embossed vinyls and custom-cut geometric motifs in bas relief. The Savannah's decks were treated with no less care than other interior elements. Inlaid patterns in vinyl tile accent the Main Lobby's lay­out and tesselate the floors of stair landings and Veranda. Polished brass circumscribes the white translucent vinyl dance floor. In a departure from tradition, non-skid ceramic tile is used as weatherproof surfacing for the en­closed promenade, usually teak plank­ing or molded rubber. Exterior recrea­tion decks are coated with a soft green "Neotex," easy on the eyes and blended with the ceramic tile around the swimming pool. Carpet was custom-woven for this ship. All-wool, it is one of the few traditional natural materials which still best satisfies the stringent fire-proofing requirements for the Savannah, as well as those of fine service and appearance. The Lounge carpet is noteworthy in concept and in­tricacy of execution. Concentric ovals in two heights of pile and two dif­ferent yarns conform to the oval out­line of the 32 by 50 ft room. It was woven in three pieces, principally for ease of handling and installation, by A. & M. Karagheusian. In the Main Dining Room, the desire for elegance outweighed practicality and a lux­uriant carpet  was  specified  and  designed, rich in color and deep of pile to please the eye and cushion the step. Like other facets of the ship's out­fit, all lighting for the interior spaces was developed for a specific purpose and location. Coves, trough down-lighting and individual ceiling fixtures are controlled by dimmers in all public rooms. General illumination is modi­fied freely with local lighting which capitalizes on the softening contrast of light and shadow. Table lamps have unusual ornamental bases of carved lucite, and variously cast and formed metals, sculptural in quality and diverse, in colors and finishes. In the Veranda, a group of six 24-hr electric clocks tell time in certain cities around the world in relation to the ship's own time. Their dials are illuminated by electro-lumi­nescence, with A.M. and P.M. halves in  contrasting blue  and  green  light. A myriad of smaller things were assembled to compose the whole. The napery, china, silver and glass­ware were styled, produced and em­blazoned with crests and Savannah symbols, to compliment and enrich the tone of the dining service. The grace­ful heavy-footed goblets of fine American crystal by Bryce are worthy of special note. To demonstrate and explain her­self best for visiting engineers, scien­tists and the just plain curious, the Savannah has unique facilities. Below the passenger decks, an enclosed Gallery surrounds her engine room, al­lowing groups who tour the vessel to view the machinery. The Gallery looks down through sloped glass windows on the control center a deck below. Closed-circuit television will allow visitors to look in on the workings of the nuclear reactor, just forward of this area but separated from it by many feet of dense shielding. Cut­away drawings of the entire plant and flow diagrams describing the systems' operation have been laminated and formed to become permanent wall panels in forward corners of the Gallery. Among the abundance of metal and plastic aboard ship, some items not already described are worthy of mention. An interesting effect has been achieved on the swimming pool. The monel metal has been striped with contrasting high- and low-luster finishes to relieve, with the additional help of colored underwater lighting, the greyness of this otherwise marvelously practical metal. Tropical screens, translucent sand­wiches of fiberglas-reinforced poly­ester filled with freeform cellular patterns, are used as room dividers in staterooms, individually color-coordinated to each room. Incombustible Saran, both spun and filament, is used. Among the complexities of the Savannah's development, the execution of the interiors alone involved the talents, services and production of literally hundreds of individuals and groups. From the individual craftsman, from corporations large and small, the infinite separate facets of her outfit evolved into a homogeneous whole. The degrees of design success achieved is due in large measure to the smooth working relationship be­tween the interior designers and the naval architects, George G. Sharp, Inc., who were responsible for the basic design and overall planning, and the government agencies and their on-the-job representatives who checked and coordinated the job.