AME 577 – Presentation
Chris Gilmer
Sai Sandeep Kaku
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.
Outline
 Need for Nuclear Power
 Quick Overview of Nuclear Energy
 Nuclear Power Generation
 Technologies of AHTR
 Thermodynamics
 Economics
 Benefits
 Challenges
 Conclusions
Need for Nuclear Power
 Global Warming - The threat
posed by growing greenhouse
gases emissions
Electricity Demand
 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
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
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
Scope for Nuclear Power
 Nuclear Power Today
 Nuclear Safety
 Waste Contamination and
Storage
 Competitive Nuclear Future
 Sustainable Development
Susquehanna Steam Electric Station,
Pennsylvania, USA
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
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
Nuclear Power Today
Layout-AHTR
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
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
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
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
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
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
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
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
Limits to Liquid Salt Selection
 Current Usage in Industry
 Cross Section
 Corrosion rate
 Melting Point
 Boiling Point
 Toxicity
 Cost
Liquid Salt Selection
*MP – Melting Point
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
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
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
Thermodynamics
 Ideal Brayton cycle under the cold air-standard
assumptions
 T4 
T1   1
C p T3  T2 
T1 
wnet
qout

th, Brayton 
 1
 1
 1
qin
qin
C p T4  T1 
 T3 
T2   1
 T2 
 Processes 1-2 and 3-4 are isentropic
 Pressure P2 = P3 and P4 = P1
T2  P2 
  
T1  P1 
 k 1
k
 P3 
  
 P4 
 k 1
k
T3

T4
Thermodynamics
 Substitution yields
th, Brayton  1 
1
k 1
T1
P2
 1  , where rp 
T2
P1
rp k
 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%
AHTR Parameters
Price of Electricity
2002 MIT Nuclear Power Study
Construction Costs
Per Peterson (Berkeley): American Nuclear Society 2004 Winter Meeting
Reduced Plant Size
Economic Sustainability
DOE-NE (2010 Roadmap Study)
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.
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
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
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.
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 0-61512420-8, <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
 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, Glossaryhttp://www.world-nuclear.org/info/inf51.html
Nuclear Waste 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
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
 Imagery –Nuclear Power Planthttp://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 Plantshttp://upload.wikimedia.org/wikipedia/commons/1/18/Nuclear_power_stations.png
Backup Slides
Thermodynamics
 Energy Equation
qin  qout   win  wout   hout  hin
 Heat Transfer
qin  h3  h2  C p T3  T2 
qout  h4  h1  C p T4  T1 
Operating Costs