Arc Reactor Blueprints Ebook 15
Myong Killings
The probability of collision with a ship of this remaining1 percent group is extremely low. Consideringthat the SAVANNAH, as the first nuclear-poweredmerchant ship, will be handled with extreme care, theprobability of a dangerous release of radioactivitythrough collision is negligible. Because large ships proceedat relatively low speeds in harbors, and becauseof the built-in invulnerability of the SAVANNAH, theprobability of a collision of sufficient severity to damagethe reactor compartment is extremely low.
In the event of a collision broadside to the reactorcompartment, the ramming ship would have to penetrate17 feet of stiffened ship structure, the collisionmat, and the reactor containment vessel, before reachingthe reactor plant.
Other accidents, such as grounding, fire and explosion,and sinking also were considered in the designand construction of the N.S. SAVANNAH. Groundingis very similar to collision in its effects, except thatthe damage is ordinarily more localized. The heavyreactor and containment foundations in the inner-bottomprovide adequate protection to the reactorsystem.
In case of sinking, provision has been made to allowfor automatic flooding of the containment shell of thereactor to prevent its collapse in deep waters. Theflooding valves are designed to close upon pressureequalization so that containment integrity will be maintainedeven after sinking. Salvage connections havebeen installed to allow containment purging or fillingwith concrete in case of sinking in shallow water whererecovery or immobilization of the reactor plant seemsadvisable.
The objective of radiation shielding on the SAVANNAHis twofold: First, it limits the radiation doseoutside the containment to prescribed safe levels, andsecond, it reduces the activation of structure withinthe containment shell by reactor core neutrons. Thelatter consideration is necessary in order that the reactorplant be accessible for maintenance within 30 minutesafter shutdown.
The primary shield, immediately surrounding thereactor pressure vessel, consists of a 17-foot-high lead-coveredsteel tank that surrounds the reactor vesselwith a 33-inch water-filled annulus. The tank extendsfrom a point well below the active core area to apoint well above it. The active core height within thereactor is only 60 inches. Constructed of carbon steel,the primary shield tank is covered with a layer of leadvarying in thickness from 2 to 4 inches. When thetank is filled with water, the dose rate outside theprimary shielding from core gamma sources and activatednuclei will not exceed 200 mr per hour 30 minutesafter shutdown. This is sufficiently low to permitentry into the containment vessel for inspection ormaintenance.
The containment shell completely surrounds theprimary (reactor) system, and serves not only to confine11spread of radioactivity in the event of a ruptureof the system but to support the hundreds of tons oflead and polyethylene of the secondary shield.
The containment shell is sealed at all times duringplant operation. Entry to the shell will be made onlyafter the reactor has been shut down, the shell purgedwith air, and the radiation level has dropped below 200mr per hour.
It includes all load control and protective devices,containment wiring, metering, interlocking and alarmsassociated with electrical loads for the reactor system.Power for the system normally is supplied by two turbine-generators,each rated at 1,500 kw, 0.8 pf, 450-volts,3 phase and 60 cycles. For increased reliability,a double bus type arrangement is used. In the eventof a bus fault, an automatic transfer of all vital loadsto the other bus will occur. During normal operation,a circuit breaker ties the two busses together.
The radiation monitoring system of the SAVANNAHkeeps a constant check on the intensity of radiationat various points within the reactor system as wellas areas remote from the power plant. This system isdivided into two areas for this description. They arepower-plant monitoring and health physics monitoring.The latter is covered under its own heading.
The fission product monitor keeps track of fissionproduct activity in the primary (reactor) system. Themonitor consists of a cation and anion column, an amplifier,and an indicating system. This monitor islocated in the primary coolant flow system.
The above monitor stations are the principal onesinvolved in reactor system operation. The monitorsoperate through a system of separate channels, witheach channel responsible for a pre-selected range ofactivity. All detectors relay their readings to the mainpanel in the control room, where automatic recordingand visual observation instruments are located.
The design of the control system is such that a malfunctionwhich leads to an abnormal withdrawal rateof the rods will not result in a dangerous condition.Studies indicate that the minimum reactor period resultingfrom maximum withdrawal of the rods is notless than 30 seconds. The control system is designedto maintain the net reactivity insertion always less thanthe delayed neutron fraction.
The entire reactor system is protected by the safetysystem. This system causes the reactor to terminatepower production if a dangerous operating conditionexists. The safety system also contains interlocks whichprevent actions which would otherwise jeopardize thereactor system.
Each of the 21 control rods has its own drivemounted vertically on the upper reactor head. Ofthese, 9 are servo controlled and 12 are of the nonservotype. The 9 servo rods have variable speed drives andoperate in two groups in a synchronous manner, accordingto demand signals from the reactor system.The 12-rod group can be operated manually or ingroups according to predetermined conditions. All ofthese operate at a speed determined by their gearing.
This system drains and collects, until safe for removal,all drainage from the reactor system that mightbe radioactive. Drainage may result from a leak, orbe part of the normal drainage accumulation duringinitial fill and testing, normal startup, operation andshutdown, and decontamination.
Intermediate Cooling System. The primary functionis to provide clean cooling water to the variousreactor system components. A secondary function is tomaintain water in the annular primary shield tank.
The men who will handle the SAVANNAH ashoreand afloat will have had the advantage of the specializedand extensive training program conducted bythe Atomic Energy Commission, the Maritime Administration,and the private contractors who built theN.S. SAVANNAH and her reactor.
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Underwater vehicle is designed to ensure the security of country sea boundary, providing harsh requirements for its power system design. Conventional power sources, such as battery and Stirling engine, are featured with low power and short lifetime. Micronuclear reactor power source featured with higher power density and longer lifetime would strongly meet the demands of unmanned underwater vehicle power system. In this paper, a 2.4 MWt lithium heat pipe cooled reactor core is designed for micronuclear power source, which can be applied for underwater vehicles. The core features with small volume, high power density, long lifetime, and low noise level. Uranium nitride fuel with 70% enrichment and lithium heat pipes are adopted in the core. The reactivity is controlled by six control drums with B4C neutron absorber. Monte Carlo code MCNP is used for calculating the power distribution, characteristics of reactivity feedback, and core criticality safety. A code MCORE coupling MCNP and ORIGEN is used to analyze the burnup characteristics of the designed core. The results show that the core life is 14 years, and the core parameters satisfy the safety requirements. This work provides reference to the design and application of the micronuclear power source.
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