Showing papers by "Jacopo Buongiorno published in 2002"

Key Differences in the Fabrication, Irradiation, and Safety Testing of U.S. and German TRISO-coated Particle Fuel and Their Implications on Fuel Performance

Abstract: High temperature gas reactor technology is achieving a renaissance around the world. This technology relies on high quality production and performance of coated particle fuel. Historically, the irradiation performance of TRISO-coated gas reactor particle fuel in Germany has been superior to that in the United States. German fuel generally displayed in-pile gas release values that were three orders of magnitude lower than U.S. fuel. Thus, we have critically examined the TRISO-coated fuel fabrication processes in the U.S. and Germany and the associated irradiation database with a goal of understanding why the German fuel behaves acceptably, why the U.S. fuel has not faired as well, and what process/ production parameters impart the reliable performance to this fuel form. The postirradiation examination results are also reviewed to identify failure mechanisms that may be the cause of the poorer U.S. irradiation performance. This comparison will help determine the roles that particle fuel process/product attributes and irradiation conditions (burnup, fast neutron fluence, temperature, and degree of acceleration) have on the behavior of the fuel during irradiation and provide a more quantitative linkage between acceptable processing parameters, as-fabricated fuel properties and subsequent in-reactor performance.

Feasibility Study of Supercritical Light Water Cooled Fast Reactors for Actinide Burning and Electric Power Production

Abstract: The use of supercritical temperature and pressure light water as the coolant in a direct-cycle nuclear reactor offers potential for considerable plant simplification and consequent capital and O&M cost reduction compared with current light water reactor (LWR) designs. Also, given the thermodynamic conditions of the coolant at the core outlet (i.e. temperature and pressure beyond the water critical point), very high thermal efficiencies of the power conversion cycle are possible (i.e. up to 46%). Because no change of phase occurs in the core, the need for steam separators and dryers as well as for BWR-type recirculation pumps is eliminated, which, for a given reactor power, results in a substantially shorter reactor vessel than the current BWRs. Furthermore, in a direct cycle the steam generators are not needed. If a tight fuel rod lattice is adopted, it is possible to significantly reduce the neutron moderation and attain fast neutron energy spectrum conditions. In this project a supercritical water reactor concept with a simple, blanket-free, pancake-shaped core will be developed. This type of core can make use of either fertile or fertile-free fuel and retain the hard spectrum to effectively burn plutonium and minor actinides from LWR spent fuel while efficiently generating electricity.

Heavy-Metal Aerosol Transport in a Lead-Bismuth-Cooled Fast Reactor with In-Vessel Direct-Contact Steam Generation

Abstract: The choice of lead or lead alloys (Pb-Bi) as the coolant of a fast reactor offers the potential for enhanced safety and reliability due to their benign physical and chemical characteristics. In an effort to assess this class of coolants in advanced nuclear systems of the next generation, an innovative fast reactor concept that eliminates the need for steam generators and main coolant pumps and thus offers capital and operating cost reduction was explored. The working steam is generated by direct-contact vaporization of water by liquid metal in the chimney above the core and is then sent directly to the turbine. The presence of a lighter fluid in the chimney substantially enhances the natural circulation of the Pb-Bi within the reactor pool. A key technical issue of this reactor concept is the consequences of Pb-Bi aerosol generation within the vessel, its transport within the power cycle components and impact on the design and operation of the turbine.Generation, transport, and deposition of Pb-Bi aerosols were modeled. It was found that the utilization of a suitable chevron steam separator design reduces the heavy-liquid metal transported to the steam lines by about three orders of magnitude. Nevertheless, the residual Pb-Bi ({approx}0.003 kg/s) ismore » predicted to be sufficient to cause embrittlement of the turbine blades if conventional materials are used and the plant is to operate for 40 yr. Four solutions to this problem were assessed and found potentially viable from a technical standpoint: blade coating, employment of alternative materials, electrostatic precipitation, and oxidation of the Pb-Bi droplets.« less

An Oxygen Control Strategy for Corrosion Minimization in Direct-Contact Lead- Bismuth/Water Systems

Abstract: The selection of structural materials suitable for fuel cladding and primary system purposes is key to the development of all lead and lead-bismuth cooled nuclear systems. Traditional austenitic stainless steels cannot be used at the temperatures of interest (>450 deg. C), because of the large solubility of nickel in bismuth. The possibility of employing low nickel martensitic/ferritic stainless steels is currently being studied. Corrosion control for these alloys is based on the formation of a stable iron oxide film on the surfaces exposed to the liquid-metal coolant. This requires maintenance of at least a minimum concentration of oxygen in the liquid metal. On the other hand, excessive oxygen can cause precipitation of lead- and bismuth-oxide slag. Excessive oxidation of the coolant is particularly challenging in the case of a direct-contact system where lead-bismuth and water are mixed to generate steam. In this paper it is demonstrated that an oxygen control strategy based on injection of minute amounts of hydrogen in the feedwater can ensure formation of the stable iron film, while preventing precipitation of the liquid-metal oxides. This corrosion-control approach is quantified in the context of a conceptual lead-bismuth-cooled fast reactor of recent development, which makes use of in-vessel direct-contactmore » generation of the working steam. (authors)« less

Design of an Actinide Burning, Lead or Lead-Bismuth Cooled Reactor That Produces Low Cost Electricty - FY-02 Annual Report

Abstract: The purpose of this collaborative Idaho National Engineering and Environmental Laboratory (INEEL) and Massachusetts Institute of Technology (MIT) Laboratory Directed Research and Development (LDRD) project is to investigate the suitability of lead or lead-bismuth cooled fast reactors for producing low-cost electricity as well as for actinide burning. The goal is to identify and analyze the key technical issues in core neutronics, materials, thermal-hydraulics, fuels, and economics associated with the development of this reactor concept. Work has been accomplished in four major areas of research: core neutronic design, plant engineering, material compatibility studies, and coolant activation. The publications derived from work on this project (since project inception) are listed in Appendix A. This is the third in a series of Annual Reports for this project, the others are also listed in Appendix A as FY-00 and FY-01 Annual Reports.

Design Strategies for Lead-Alloy-Cooled Reactors for Actinide Burning and Low-Cost Electricity Production

Abstract: A multi-year project at the INEEL and MIT is investigating the potential of lead or lead-bismuth (lead-alloy) cooled fast critical reactors for producing low-cost electricity as well as for burning actinides from LWR spent fuel. While these two goals are the primary thrust in the development of a conceptual design, the proliferation resistance of the fuel and the plant safety are also important constraints incorporated into the design process. Thus, this concept addresses all Generation IV reactor goals, which involve favorable economics, enhanced safety, and sustainability. This paper outlines the objectives of the project, the challenges shaping the design strategy, and the approaches adopted to achieve the design goals. The most promising path forward is also identified. The four key factors that influence the direction of the design and also require compromise are the actinide destruction rate, safety, economy, and proliferation resistance. Achieving a maximum actinide destruction rate per MWth requires fertile-free fuels. However, the achievement of safe reactivity coefficients in such cores is difficult. If the total elimination of actinides from LWR spent fuel is pursued, multiple reprocessing with high recovery efficiency is necessary. This will probably significantly increase the fuel cycle costs, thus negatively affecting the economics. On the other hand, in-situ breeding and burning of plutonium in cores initially loaded with U235 can be cost effective. However, such a system does not achieve any reduction in the actinide inventory, and the discharge fuel contains relatively pure Pu239, which poses a potential proliferation threat. To reconcile these competing goals, a number of approaches have been investigated to achieve a balanced design that is cost competitive with other alternatives for electricity generation, attains excellent safety, helps in the reduction of transuranics from the spent LWR fuel, and has discharged fuel that is at least as proliferation resistant as spent LWR fuel from a once-through cycle. The preliminary design of the reactor concept that has the best potential to achieve these characteristics is identified and briefly described. This concept incorporates a supercritical carbon dioxide power conversion cycle that achieves thermal efficiencies up to 45% at a core outlet temperature of 550°C. However, conventional steam cycles are also an option.© 2002 ASME

Feasibility Study of Supercritical Light Water Cooled Fast Reactors for Actinide Burning and Electric Power Production Progress Report for Year 1, Quarter 2 (January - March 2002)

Abstract: The use of light water at supercritical pressures as the coolant in a nuclear reactor offers the potential for considerable plant simplification and consequent capital and O&M cost reduction compared with current light water reactor (LWR) designs. Also, given the thermodynamic conditions of the coolant at the core outlet (i.e. temperature and pressure beyond the water critical point), very high thermal efficiencies of the power conversion cycle are possible (i.e. up to about 45%). Because no change of phase occurs in the core, the need for steam separators and dryers as well as for BWR-type re-circulation pumps is eliminated, which, for a given reactor power, results in a substantially shorter reactor vessel and smaller containment building than the current BWRs. Furthermore, in a direct cycle the steam generators are not needed.