Read Ebook: The Nuclear Ship Savannah First Atomic Merchant Ship One of the World's Safest Ships by United States Department Of Commerce United States Maritime Administration U S Atomic Energy Commission

Font size: 10 px 15 px 20 px 25 px 30 px 35 px

Background color: BlackWhiteGrayLight GrayDark GrayDim Gray

Text color: BlackWhiteGrayLight GrayDark GrayDim Gray

Apply/Save settings

Ebook has 140 lines and 8917 words, and 3 pages

the nuclear ship SAVANNAH

one of the world's SAFEST ships

CONTROL ROD DRIVE MOTORS HYDRAULIC SCRAM CYLINDERS DRIVE LINE LEAD SCREW SECTION BUFFER SEAL ENCLOSURE BORON STEEL CONTROL RODS PRESSURE VESSEL OUTLET NOZZLE REACTOR CORE THERMAL SHIELD FUEL ELEMENTS FLOW BAFFLE SUPPORT RING INLET NOZZLE PRESSURIZED WATER REACTOR

The N.S. SAVANNAH, the first nuclear-powered cargo-passenger ship, is one of the safest seagoing craft in the world.

This is the result of careful and deliberate planning.

Every appropriate safety device, factor, and technique were sought in the design and planning stage, and the ship's construction has probably been more closely and intensively inspected, tested, and scrutinized than that of any other merchant ship ever built.

SAFETY POLICY BASIC

The Declaration of Policy of the Merchant Marine Act of 1936 calls upon the Maritime Administration for the promotion and maintenance of an American Merchant Marine for trade and defense "composed of the best equipped, safest, and most suitable types of vessels."

The Atomic Energy Commission is engaged in the N.S. SAVANNAH project as a part of its responsibility under the Atomic Energy Act of 1954 "to encourage widespread participation in the development and utilization of atomic energy for peaceful purposes to the maximum extent consistent with the common defense and security and with the health and safety of the public." The Commission has the responsibility of providing a safely operable nuclear power plant for the vessel; instructions and regulations for the disposition of wastes; the use, handling, and disposal of source, special nuclear, and by-product material; and the health and safety aspects associated with these responsibilities.

Ship safety ashore, abroad, on the high seas, and in port is of major interest to the Maritime Administration, the Atomic Energy Commission, the U.S. Coast Guard, the Public Health Service, and such private agencies as the American Bureau of Shipping.

The N.S. SAVANNAH is constructed to meet or surpass every standard set by all of these responsible agencies and will have a substantial built-in safety margin in excess of the most stringent requirements of applicable standards, which are among the highest in the world. Where there were no existing standards every precaution in keeping with sound judgment and engineering experience has been applied in the construction and safety considerations of the ship.

The reputation of American industry and the integrity of the Government of the United States stand behind this statement.

Following is a detailed listing of the factors that make the N.S. SAVANNAH so safe:

SAFETY FACTORS

As the world's first commercial, nonstationary type of nuclear power plant, the SAVANNAH's design and construction have resulted in a vessel with an unprecedented degree of safety. Basically, the safety considerations concern two separate but closely inter-related factors:

The hull and interior structure surpass the highest standards of safety, both in the conventional marine sense and in the light of the additional factors created by the installation of a nuclear propulsion plant; and

The nuclear propulsion system creates no more hazard to the crew and passengers, and other ships in a busy port, than any modern conventional steam propulsion system--actually, in the light of safety factors, included because of its prototype nature, the N.S. SAVANNAH is as safe as, and in some respects safer than, a steam-powered vessel that burns coal or oil.

The basic difference in safety between a nuclear-powered ship and a conventionally powered ship involves radioactivity which results from the fission process. Provision has been made to control this radioactivity on the SAVANNAH under all foreseeable conditions. This control is accomplished through the following design and operational features:

HULL AND INTERIOR STRUCTURE

In general, the following safety requirements were used by the SAVANNAH's architects, George G. Sharp, Inc., in the design of the ship:

The ship is as safe as, or safer than, any other vessel of its class with regard to the usual "hazards of the sea"; and

In no credible accident can there be any hazardous release of radioactivity to the surroundings.

The SAVANNAH is designed to a two-compartment standard of subdivision at a draft of 29 feet, 6 inches. The ship complies with all the applicable laws of the United States and requirements of the regulatory bodies and rules in force as to standards of safety.

Structurally, the SAVANNAH differs from conventional passenger-cargo ships only in that the reactor and containment foundations are comparatively much heavier than the foundations for normal ship's machinery. The heavy longitudinal members are carried well beyond the reactor space bulkheads to tie with a smooth transition into the double-bottom structure.

Stability equivalent to that of a conventional passenger-cargo ship with fuel oil tanks full has been obtained in the SAVANNAH. In addition, because there is no fuel oil to be consumed in passage, there is less variation in the stability of the ship during the course of a long voyage.

VITAL COMPONENTS DUPLICATED

From the standpoint of ship safety, assurance of sufficient power to maintain steerage and maneuverability is the principal requirement of the propulsion plant. To this end, duplication of machinery and power sources on the SAVANNAH has been carried to the fullest practicable degree. An electric "take-home" motor is installed for emergency operation. Developing 750 hp , it is coupled to one of the high-speed pinions in the reduction gear. A quick-connect coupling permits engagement in less than 2 minutes. In addition, a temporary supplementary startup steam plant is installed in No. 7 hold. This plant is capable of developing 2,000 shp ahead and about 1,750 shp astern, using the main propulsion unit; in emergencies this steam plant may be used in lieu of the take-home motor. Using forced circulation boilers, it can, like the take-home motor, be brought on the line in about 2 minutes. In case of a reactor plant failure, the stored heat in the reactor system will be available during the interim period, so that at no time will the SAVANNAH be without power to the shaft.

From the standpoint of conventional ship operation, the SAVANNAH is designed and constructed to the highest degree of operational safety.

Reactor safety is ensured by the heavy steel containment shell surrounding the reactor system. This shell is designed to withstand the pressure surge from the hypothetical example, "maximum credible accident," used in nuclear reactor analysis. Thus, any internal accident will be contained within the reactor containment shell and no hazardous amount of radioactivity can escape to the environment.

Protection of the containment complex from ship accidents was studied in detail in establishing the SAVANNAH's design criteria. 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 is designed and constructed to withstand, without damage to the nuclear reactor compartment, any collision with any of the ships making up 99 percent of the world's merchant fleet.

COLLISION POSSIBILITY LOW

The probability of collision with a ship of this remaining 1 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 negligible. Because large ships proceed at relatively low speeds in harbors, and because of the built-in invulnerability of the SAVANNAH, the probability of a collision of sufficient severity to damage the reactor compartment is extremely low.

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 are two heavy longitudinal collision bulkheads; outboard of these bulkheads there is heavier-than-normal plating continuously welded to the beams. Inboard of the collision bulkheads are collision mats made up of alternate layers of 1-inch steel and 3-inch redwood planks for a total thickness of 24 inches.

In the event of a collision broadside to the reactor compartment, the ramming ship would have to penetrate 17 feet of stiffened ship structure, the collision mat, and the reactor containment vessel, before reaching the reactor plant.

SINKING, GROUNDING WEIGHED

Other accidents, such as grounding, fire and explosion, and sinking also were considered in the design and construction of the N.S. SAVANNAH. Grounding is very similar to collision in its effects, except that the damage is ordinarily more localized. The heavy reactor and containment foundations in the inner-bottom provide adequate protection to the reactor system.

The SAVANNAH, as a passenger ship, is prohibited by Coast Guard regulation from carrying dangerous and explosive cargo in quantity.

The ship's fire-protection and fire-fighting systems are fully adequate.

In case of sinking, provision has been made to allow for automatic flooding of the containment shell of the reactor 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 or filling with concrete in case of sinking in shallow water where recovery or immobilization of the reactor plant seems advisable.

Besides the very latest in navigation and communication equipment, including true motion radar, the ship is equipped with antiroll stabilizers. Located outside the hull amidships, the stabilizers are operated hydraulically by a gyro system capable of sensing sea conditions and providing counter-forces to reduce the roll. Each stabilizing fin has a lift of approximately 70 tons at 20 knots speed.

RADIATION SHIELDING

One of the most important features of the SAVANNAH is her radiation shielding. The main sources of radiation during operation of the SAVANNAH's power plant are the reactor itself and the primary coolant loop lines. The primary coolant which passes through the reactor core is irradiated, and itself becomes a source of radiation. Both the reactor and the coolant emit neutrons and gamma rays. There are also radiation sources of lesser magnitude including process piping, hold-up tanks, pumps, and demineralizers.

The objective of radiation shielding on the SAVANNAH is twofold: First, it limits the radiation dose outside the containment to prescribed safe levels, and second, it reduces the activation of structure within the containment shell by reactor core neutrons. The latter consideration is necessary in order that the reactor plant be accessible for maintenance within 30 minutes after shutdown.

The shielding is divided into a primary shield, which surrounds the reactor itself, and a secondary shield, which surrounds the entire containment shell.

PRIMARY SHIELDING

The primary shield, immediately surrounding the reactor pressure vessel, consists of a 17-foot-high lead-covered steel tank that surrounds the reactor vessel with a 33-inch water-filled annulus. The tank extends from a point well below the active core area to a point well above it. The active core height within the reactor is only 60 inches. Constructed of carbon steel, the primary shield tank is covered with a layer of lead varying in thickness from 2 to 4 inches. When the tank is filled with water, the dose rate outside the primary shielding from core gamma sources and activated nuclei will not exceed 200 mr per hour 30 minutes after shutdown. This is sufficiently low to permit entry into the containment vessel for inspection or maintenance.

SECONDARY SHIELDING

The containment shell completely surrounds the primary system, and serves not only to confine spread of radioactivity in the event of a rupture of the system but to support the hundreds of tons of lead and polyethylene of the secondary shield.

CONTAINMENT SHELL

The primary function of the containment shell is to surround the primary system and provide complete containment of any radioactive matter that might escape from the system. The design pressure of the vessel was determined by postulating the instantaneous release and expansion of the entire contents of the primary system. This approach is highly conservative because of the improbability of a large rupture.

A study has been made concerning the penetration of the vessel wall by a piece of debris in an explosion. An analysis of the penetrating power of high-speed components indicated that the shell would contain the largest missile that could be expected.

Share on: WhatsApp @Hash Facebook Tweet