“The Advanced High-Temperature Reactor”

1. “The Advanced High-Temperature Reactor” AME 577 – Presentation Chris Gilmer Sai Sandeep Kaku

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.

3. Outline • Need for Nuclear Power • Quick Overview of Nuclear Energy • Nuclear Power Generation • Technologies of AHTR • Thermodynamics • Economics • Benefits • Challenges • Conclusions

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. Electricity Demand Source: OECD/IEA World Energy Outlook 2006

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 = mc² • 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

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

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

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

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

10. Nuclear Power Today

11. Layout-AHTR

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

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

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

15. 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. Nuclear Fuel Rod Assembly

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

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

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

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 (~50˚C, as opposed to ~1000˚C Gas Cooled Reactors) • Low Corrosion Rates

20. Limits to Liquid Salt Selection • Current Usage in Industry • Cross Section • Corrosion rate • Melting Point • Boiling Point • Toxicity • Cost

21. Liquid Salt Selection *MP – Melting Point

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

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

24. Decay Heat Removal • Salt freezing points between 350˚C and 500˚C • Salt boiling points up to ~ 1400˚C • Fuel temperature rated to ~ 1600˚C • Accident • Exit Coolant at ~ 1,000°C • Peak Fuel ~ 1,160°C at 30h • Peak Vessel ~ 750°C at 45h • Natural circulation provides ~ 50˚C heat gradient

25. Thermodynamics • Ideal Brayton cycle under the cold air-standard assumptions • Processes 1-2 and 3-4 are isentropic • Pressure P2= P3and P4= P1

26. Thermodynamics • Substitution yields • Efficiency Depends upon Temperature (T2) • LWR – 33% • AHTR-LT (705˚C) – 48.0% • AHTR-IT (800˚C) – 51.5% • AHTR-VT (1000˚C) – 56.6%

27. AHTR Parameters

28. Price of Electricity 2002 MIT Nuclear Power Study

29. Construction Costs Per Peterson (Berkeley): American Nuclear Society 2004 Winter Meeting

30. Reduced Plant Size

31. Economic Sustainability

32. DOE-NE (2010 Roadmap Study)

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 (700˚C – 1000˚C) • Higher efficiency • Produces less thermal pollution • Enables use of dry cooling, reducing water consumption.

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

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

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.

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_fuel • Wikipedia, “Nuclear Power”, 11/09/2007, http://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 • Wikipedia, “Brayton Cycle”, 11/09/2007, http://en.wikipedia.org/wiki/Brayton_Cycle • The Future of Nuclear Power, Massachusetts Institute of Technology, 2003, ISBN 0-615-12420-8, <http://web.mit.edu/nuclearpower/>. Retrieved on 2006-11-10 • Nuclear Energy- http://www-formal.stanford.edu/jmc/progress/nuclear-faq.html • Nuclear Science & Tech- http://www.aboutnuclear.org/view.cgi?fC=NST

38. World Nuclear Organization, Need – http://www.world-nuclear.org/why/why.html • World Nuclear Organization, Power Reactors - 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.html • 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 • Imagery- Rankine Cycle http://images.google.com/images?q=rankine+cycle&revid=1648754521&sa=X&oi=revisions_inline&resnum=0&ct=broad-revision&cd=1

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, Peterson • Nuclear Technology- http://www.nuc.berkeley.edu/research/index.htm • Imagery, Commercial Nuclear Power Plants- http://upload.wikimedia.org/wikipedia/commons/1/18/Nuclear_power_stations.png

40. Backup Slides

41. Thermodynamics • Energy Equation • Heat Transfer

42. Operating Costs