986 resultados para Water cooled reactors.


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Seven plans on folded leaves attached inside back cover.

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In this work, we performed an evaluation of decay heat power of advanced, fast spectrum, lead and molten salt-cooled reactors, with flexible conversion ratio. The decay heat power was calculated using the BGCore computer code, which explicitly tracks over 1700 isotopes in the fuel throughout its burnup and subsequent decay. In the first stage, the capability of the BGCore code to accurately predict the decay heat power was verified by performing a benchmark calculation for a typical UO2 fuel in a Pressurized Water Reactor environment against the (ANSI/ANS-5.1-2005, "Decay Heat Power in Light Water Reactors," American National Standard) standard. Very good agreement (within 5%) between the two methods was obtained. Once BGCore calculation capabilities were verified, we calculated decay power for fast reactors with different coolants and conversion ratios, for which no standard procedure is currently available. Notable differences were observed for the decay power of the advanced reactor as compared with the conventional UO2 LWR. The importance of the observed differences was demonstrated by performing a simulation of a Station Blackout transient with the RELAP5 computer code for a lead-cooled fast reactor. The simulation was performed twice: using the code-default ANS-79 decay heat curve and using the curve calculated specifically for the studied core by BGCore code. The differences in the decay heat power resulted in failure to meet maximum cladding temperature limit criteria by ∼100 °C in the latter case, while in the transient simulation with the ANS-79 decay heat curve, all safety limits were satisfied. The results of this study show that the design of new reactor safety systems must be based on decay power curves specific to each individual case in order to assure the desired performance of these systems. © 2009 Elsevier B.V. All rights reserved.

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Conceptual designs of lead-cooled and liquid salt-cooled fast flexible conversion ratio reactors were developed. The performance achievable by the unity conversion ratio cores of these reactors was compared to an existing supercritical carbon dioxide-cooled (S-CO2) fast reactor design and an uprated version of an existing sodium-cooled fast reactor. All concepts have cores rated at 2400 MWt. The cores of the liquid-cooled reactors are placed in a large-pool-type vessel with dual-free level, which also contains four intermediate heat exchangers (IHXs) coupling a primary coolant to a compact and efficient supercritical CO2 Brayton cycle power conversion system. The S-CO2 reactor is directly coupled to the S-CO2 Brayton cycle power conversion system. Decay heat is removed passively using an enhanced reactor vessel auxiliary cooling system (RVACS) and a passive secondary auxiliary cooling system (PSACS). The selection of the water-cooled versus air-cooled heat sink for the PSACS as well as the analysis of the probability that the PSACS may fail to complete its mission was performed using risk-informed methodology. In addition to these features, all reactors were designed to be self-controllable. Further, the liquid-cooled reactors utilized common passive decay heat removal systems whereas the S-CO2 uses reliable battery powered blowers for post-LOCA decay heat removal to provide flow in well defined regimes and to accommodate inadvertent bypass flows. The multiple design limits and challenges which constrained the execution of the four fast reactor concepts are elaborated. These include principally neutronics and materials challenges. The neutronic challenges are the large positive coolant reactivity feedback, small fuel temperature coefficient, small effective delayed neutron fraction, large reactivity swing and the transition between different conversion ratio cores. The burnup, temperature and fluence constraints on fuels, cladding and vessel materials are elaborated for three categories of material - materials currently available, available on a relatively short time scale and available only with significant development effort. The selected fuels are the metallic U-TRU-Zr (10% Zr) for unity conversion ratio and TRU-Zr (75% Zr) for zero conversion ratio. The principal selected cladding and vessel materials are HT-9 and A533 or A508, respectively, for current availability, T-91 and 9Cr-1Mo steel for relatively short-term availability and oxide dispersion strengthened ferritic steel (ODS) available only with significant development. © 2009 Elsevier B.V. All rights reserved.

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"Contract AT(30-1)-2789."

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A packed bed bioreactor (PBBR) was developed for rapid establishment of nitrification in brackish water hatchery systems in the tropics. The reactors were activated by immobilizing ammonia-oxidizing (AMONPCU- 1) and nitrite-oxidizing (NIONPCU-1) bacterial consortia on polystyrene and low-density polyethylene beads, respectively. Fluorescence in situ hybridization demonstrated the presence of autotrophic nitrifiers belong to Nitrosococcus mobilis, lineage of b ammonia oxidizers and nitrite oxidizer Nitrobacter sp. in the consortia. The activated reactors upon integration to the hatchery system resulted in significant ammonia removal (P\0.01) culminating to its undetectable levels. Consequently, a significantly higher percent survival of larvae was observed in the larval production systems. With spent water the reactors could establish nitrification with high percentage removal of ammonia (78%), nitrite (79%) and BOD (56%) within 7 days of initiation of the process. PBBR is configured in such a way to minimize the energy requirements for continuous operation by limiting the energy inputs to a single stage pumping of water and aeration to the aeration cells. The PBBR shall enable hatchery systems to operate under closed recirculating mode and pave the way for better water management in the aquaculture industry.

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This report is a dissertation proposal that focuses on the energy balance within an internal combustion engine with a unique coolant-based waste heat recovery system. It has been predicted by the U.S. Energy Information Administration that the transportation sector in the United States will consume approximately 15 million barrels per day in liquid fuels by the year 2025. The proposed coolant-based waste heat recovery technique has the potential to reduce the yearly usage of those liquid fuels by nearly 50 million barrels by only recovering even a modest 1% of the wasted energy within the coolant system. The proposed waste heat recovery technique implements thermoelectric generators on the outside cylinder walls of an internal combustion engine. For this research, one outside cylinder wall of a twin cylinder 26 horsepower water-cooled gasoline engine will be implemented with a thermoelectric generator surrogate material. The vertical location of these TEG surrogates along the water jacket will be varied along with the TEG surrogate thermal conductivity. The aim of this proposed dissertation is to attain empirical evidence of the impact, including energy distribution and cylinder wall temperatures, of installing TEGs in the water jacket area. The results can be used for future research on larger engines and will also assist with proper TEG selection to maximize energy recovery efficiencies.

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"Issued April 3, 1962"

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"Contract AT(30-1)-2789."

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Includes index.

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The development of reliable, high powered plasma generators has resulted in many plasma processes being proposed as alternatives to existing pyrometallurgical technologies. This work evaluates the advantages and disadvantages of plasma systems by reviewing plasma generators, their integration with reactors and the process economics. Many plasma systems were shown to be technically and economically superior to existing technologies, but some of the plasma system advantages quoted in the literature were found to be impractical because of other system constraints. Process applications were limited by the power inputs available from plasma generators compared to AC electric furnaces. A series of trials were conducted where chromite and steelplant baghouse dusts were smelted in the Tetronics' 2.0 MW transferred arc/open bath reactor to confirm the operating characteristics of the plasma system and its economics. Chromite smelting was technical superior to submerged arc furnace technology, but the economics were unfavourable because of the limited power available from the water-cooled plasma torch and the high electrical energy consumption. A DC graphite electrode plasma furnace using preheated and prereduced chromite concentrates will compete economically with the submerged arc furnace. Ni, Cr and Mo were economically recovered from high alloy content steelplant dusts for recycling. Five Electric Arc Furnace dusts were smelted to produce a non-toxic residue and recover the contained zinc to an enriched zinc oxide product for recycling. It should be possible to condense the zinc vapour directly in a zinc splash condenser to increase the value of the product. Because of the limited power available from plasma generators, plasma processes will be most suitable for treating high and medium value materials such as Au, Pt, Mo, Ni, Ti, V, Cr etc at small production rates, heating metals in tundishes and ladles and remelting superalloy scrap. The treatment of environmentally hazardous waste materials is a particularly interesting application because of the additional financial incentives. Non-transferred arc plasma generators will be used for air and gas preheating in blast furnaces to reduce metallurgical coke consumptions.

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Renewable non-edible plant oils such as jatropha and karanj have potential to substitute fossil diesel fuels in CI engines. A multi-cylinder water cooled IDI type CI engine has been tested with jatropha and karanj oils and comparisons made against fossil diesel. The physical and chemical properties of the three fuels were measured to investigate the suitability of jatropha and karanj oils as fuels for CI engines. The engine cooling water circuit and fuel supply systems were modified such that hot jacket water preheated the neat plant oil prior to injection. Between jatropha and karanj there was little difference in the performance, emission and combustion results. Compared to fossil diesel, the brake specific fuel consumption on volume basis was around 3% higher for the plant oils and the brake thermal efficiency was almost similar. Jatropha and karanj operation resulted in higher CO 2 and NO x emissions by 7% and 8% respectively, as compared to diesel. The cylinder gas pressure diagram showed stable engine operation with both plant oils. At full load, the plant oils gave around 3% higher peak cylinder pressure than fossil diesel. With the plant oils, cumulative heat release was smaller at low load and almost similar at full load, compared to diesel. At full load, the plant oils exhibited 5% shorter combustion duration. The study concludes that the IDI type CI engine can be efficiently operated with neat jatropha (or karanj) oil preheated by jacket water, after small modifications of the engine cooling and fuel supply circuits. © 2012 Elsevier Ltd.