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AME 577 Presentation Chris Gilmer Sai Sandeep Kaku Slide 2 Premise Advanced High Temperature Reactor (AHTR) brings together various technologies such as nuclear fuels with coated particles; Brayton power cycles; liquid salt coolants; and passive safety systems. The system delivers high performance and operates in a window of economic sustainability. Slide 3 Outline Need for Nuclear Power Quick Overview of Nuclear Energy Nuclear Power Generation Technologies of AHTR Thermodynamics Economics Benefits Challenges Conclusions Slide 4 Need for Nuclear Power Global Warming - The threat posed by growing greenhouse gases emissions Population Growth - The increasing need for energy to support the Earth's growing population Nuclear Reality - The need to include nuclear energy as a part of long term energy solution. Source: OECD/IEA World Energy Outlook 2006 Electricity Demand Slide 5 Nuclear Energy Basics An atom - The smallest particle of matter Neutrally charged in nature The mass of the atom is concentrated in the nucleus Mass-Energy Equivalence E = mc Nuclear energy is released by three exothermic processes namely radioactive decay, fusion and fission. Fission is the splitting of the a heavy nucleus an atom into lighter nuclei involving release of large amounts of energy 3.2 10 -11 J or 7.7 10 -12 cal Slide 6 Nuclear Power Generation A nuclear reactor produces and controls the release of energy from splitting the atoms The energy released from continuous fission of the atoms as heat is used to make steam. The steam is used to drive the turbines which produce electricity Several components of a reactor include : Fuel Moderator Control rods Coolant Steam Generator Contaminant structure Slide 7 Scope for Nuclear Power Nuclear Power Today Nuclear Safety Waste Contamination and Storage Competitive Nuclear Future Sustainable Development Susquehanna Steam Electric Station, Pennsylvania, USA Slide 8 Nuclear Power Today Two thirds of world population lives in nuclear powered nations Half the world's people live in countries where new nuclear power reactors are in planning or under construction This shows that a rapid expansion of global nuclear power would require no fundamental change Nuclear Safety Zero reportable safety-related 'events Nuclear power plants rank among the strongest structures ever built. Perfect safety record while transportation Slide 9 Waste Contamination and Storage Small amounts of waste compared to large and unmanageable waste from fossil fuels Geological repositors -ensure harmful radiation would not reach the surface Competitive Nuclear Future Narrowing costs between nuclear power and that from fossil fuels A price tag on harmful emissions would make nuclear power the cheapest option Sustainable Future Vast amounts of fuel Virtually no pollution Slide 10 Nuclear Power Today Slide 11 Layout-AHTR Slide 12 AHTR Technologies Coated-particle nuclear fuel(TRISO) Brayton power cycle instead of the traditional Rankine steam turbine cycle Low-pressure liquid-salt coolants Passive Safety Systems and plant designs from liquid-cooled fast reactors Slide 13 Nuclear Fuel Definition: Any material that can be consumed to derive nuclear energy The most common type being heavy fissile elements that can be made to undergo fission, namely plutonium - 239 and uranium-235 For use as nuclear fuel, enriched uranium hexafluoride is converted into uranium dioxide powder that is then processed into pellet form Slide 14 Coated Particle Nuclear Fuel (TRISO) Tristructural-isotropic (TRISO) fuel is a type of micro fuel particle It consists of a fuel kernel composed of UOX pebble in the center This is surrounded by layers of carbon and silicon carbide These particles may be arranged: in blocks - hexagonal 'prisms' of graphite, or in billiard ball-sized pebbles of graphite Slide 15 Nuclear Fuel Rod Assembly Salient Attributes Retain fission products at elevated temperatures Give the fuel particle more structural integrity. Designed not to crack due to the stresses from differential thermal expansion or fission gas pressure. Contain the fuel in the worst of accident scenarios. Ensure good heat transfer from fuel thereby preventing hot spots in the core. Slide 16 Turbine Power Cycle Rankine (steam) power cycle It directly employs steam to drive the turbines Associated problems include lower operating temperatures (lower efficiency), turbine blade fouling, larger equipment and wet cooling Slide 17 Brayton Cycle - Power Works on the principle of isentropic compression and expansion mediated by isobaric heat addition and heat rejection Operates at higher temperatures enabling higher efficiencies and reducing total heat rejection No moisture separation and steam extraction involved Less expensive than Rankine cycle setup per unit of electrical output Facilitates the option of dry cooling in cooling towers thereby reducing water consumption Slide 18 Brayton Cycle - Integration Uses the heat from the molten salt to reheat the working fluid thereby raising its temperature to maximum level Employs up to four stages of reheating and up to eight stages of inter-cooling Gas expansion takes place in three turbines in series, with reheating between them The working fluid is typically Nitrogen or Helium Slide 19 Low-Pressure Liquid Salt Basis for Fast Reactor layout Good Heat Transfer Properties Low-Pressure Operation Transparent (In-Service Inspection) Clean Salt and Solid Fuel (not Molten Salt Reactor with Fuel in Coolant) Small Heat Gradients (~5 0C, as opposed to ~1000C Gas Cooled Reactors) Low Corrosion Rates Slide 20 Limits to Liquid Salt Selection Current Usage in Industry Cross Section Corrosion rate Melting Point Boiling Point Toxicity Cost Slide 21 Liquid Salt Selection *MP Melting Point Slide 22 Salt Specific R&D Needs Salt properties Several salts being considered (LiF, NaF, KF, etc.) Properties only partly known Impact of impurities Salt instrumentation Requirements for online reactor monitoring Salt qualification Salt purification Initial production Reactor online purification Slide 23 Passive Safety Systems Passive decay-heat-removal system Reduced need for water Reduce heat transfer from reactor to guard vessel Larger Reactors Possible Easier to remove passive decay heat with salt coolant Fewer cost-prohibitive active systems Slide 24 Decay Heat Removal Salt freezing points between 350C and 500C Salt boiling points up to ~ 1400C Fuel temperature rated to ~ 1600C Accident Exit Coolant at ~ 1,000C Peak Fuel ~ 1,160C at 30h Peak Vessel ~ 750C at 45h Natural circulation provides ~ 50C heat gradient Slide 25 Thermodynamics Ideal Brayton cycle under the cold air-standard assumptions Processes 1-2 and 3-4 are isentropic Pressure P 2 = P 3 and P 4 = P 1 Slide 26 Thermodynamics Substitution yields Efficiency Depends upon Temperature (T 2 ) LWR 33% AHTR-LT (705C) 48.0% AHTR-IT (800C) 51.5% AHTR-VT (1000C) 56.6% Slide 27 AHTR Parameters Slide 28 Price of Electricity 2002 MIT Nuclear Power Study Slide 29 Construction Costs Per Peterson (Berkeley): American Nuclear Society 2004 Winter Meeting Slide 30 Reduced Plant Size Slide 31 Economic Sustainability Slide 32 DOE-NE (2010 Roadmap Study) Slide 33 Benefits of AHTR Coated Particle Fuels Enable increased structural integrity Resistance to cracking due to thermal stresses The Brayton-cycle power technology uses higher operating temperatures (700C 1000C) Higher efficiency Produces less thermal pollution Enables use of dry cooling, reducing water consumption. Slide 34 Benefits of AHTR Low-Pressure Liquid Salts Good heat transfer characteristics Reduced temperature gradients Transparent for inspection Passive Safety Systems Radioactive decay heat removal Heat characteristics nominal for accidents Sustainability Reduced need for water Smaller physical plant size Economically feasible Slide 35 R&D Challenges Materials: Needs are goal dependent Qualified materials to 750 C Candidate materials requiring more testing to 850 C Major R&D required for 1000 C Reactor core design Salt selection and processing (several options) Neutronics Refueling temperatures 350 to 500 C (avoid salt freezing) Related Salt Uncertainties Slide 36 Conclusion The AHTR is a reactor concept that maximizes the utility of individual technologies by combining them to achieve higher process efficiencies, greater power output, and better safety. These technologies show the potential for an economically and environmentally sustainable plant design. Slide 37 References Forsberg, C.W., Peterson, P.F., and Zhao, H. (Dec. 2006). Sustainability and Economics of the Advanced High-Temperature Reactor. Journal of Energy Engineering, ASCE, 132:3 (2006): 109 - 115 Forsberg, C.W., Peterson, P.F., and Williams, D.F. (2005). Liquid-salt-cooling for advanced high-temperature reactors. Proc., 2005 Int. Congress on Advances in Nuclear Power Plants (ICAPP 05), American Nuclear Society, La Grange Park, Ill. Wikipedia, Nuclear Fuel, 9/21/2007, http://en.wikipedia.org/wiki/Nuclear_fuelhttp://en.wikipedia.org/wiki/Nuclear_fuel Wikipedia, Nuclear Power, 11/09/2007, http://en.wikipedia.org/wiki/Nuclear_Powerhttp://en.wikipedia.org/wiki/Nuclear_Power Wikipedia, Economics of New Nuclear Power Plants, 11/09/2007, http://en.wikipedia.org/wiki/Economics_of_new_nuclear_power_plants http://en.wikipedia.org/wiki/Economics_of_new_nuclear_power_plants Wikipedia, Brayton Cycle, 11/09/2007, http://en.wikipedia.org/wiki/Brayton_Cyclehttp://en.wikipedia.org/wiki/Brayton_Cycle The Future of Nuclear Power, Massachusetts Institute of Technology, 2003, ISBN 0-615- 12420-8,. Retrieved on 2006-11-10 The Future of Nuclear PowerMassachusetts Institute of TechnologyISBN 0-615- 12420-8http://web.mit.edu/nuclearpower/ Nuclear Energy- http://www-formal.stanford.edu/jmc/progress/nuclear-faq.htmlhttp://www-formal.stanford.edu/jmc/progress/nuclear-faq.html Nuclear Science & Tech- http://www.aboutnuclear.org/view.cgi?fC=NSThttp://www.aboutnuclear.org/view.cgi?fC=NST Slide 38 World Nuclear Organization, Need http://www.world-nuclear.org/why/why.htmlhttp://www.world-nuclear.org/why/why.html World Nuclear Organization, Power Reactors - http://www.worldnuclear.org/how/npreactors.html http://www.worldnuclear.org/how/npreactors.html World Nuclear Organization, Fuel Cycles- http://www.world-nuclear.org/how/fuelcycle.html World Nuclear Organization, Glossary- http://www.world-nuclear.org/info/inf51.html Nuclear Waste - http://library.thinkquest.org/17940/texts/nuclear_waste_future/nuclear_waste_future.ht ml http://library.thinkquest.org/17940/texts/nuclear_waste_future/nuclear_waste_future.ht ml Brayton Cycle- Brayton Cycle: The Ideal Cycle for Gas-Turbine Engines in Relation to Power Plants by Denise Lane Thermodynamics and Power Cycles, Thermal Engineering 2 Rajput Imagery- Brayton Cycle http://images.google.com/images?hl=en&q=brayton+cycle&gbv=2 http://images.google.com/images?hl=en&q=brayton+cycle&gbv=2 Imagery- Rankine Cycle http://images.google.com/images?q=rankine+cycle&revid=1648754521&sa=X&oi=revision s_inline&resnum=0&ct=broad-revision&cd=1 http://images.google.com/images?q=rankine+cycle&revid=1648754521&sa=X&oi=revision s_inline&resnum=0&ct=broad-revision&cd=1 Slide 39 Imagery Nuclear Power Plant- http://images.google.com/images?svnum=10&hl=en&q=nuclear+power+plant Temperature Helium Brayton Cycles- Thermal Hydraulics Group, Thermal Labs IFE Experiment page, PetersonThermal Hydraulics GroupThermal Labs IFE Experiment pagePeterson Nuclear Technology- http://www.nuc.berkeley.edu/research/index.htmhttp://www.nuc.berkeley.edu/research/index.htm Imagery, Commercial Nuclear Power Plants- http://upload.wikimedia.org/wikipedia/commons/1/18/Nuclear_power_stations.png http://upload.wikimedia.org/wikipedia/commons/1/18/Nuclear_power_stations.png Slide 40 Backup Slides Slide 41 Thermodynamics Energy Equation Heat Transfer Slide 42 Operating Costs