Advanced High-Temperature Reactors: What and Why

(A Story of Technology Development)

Charles W. Forsberg

Oak Ridge National Laboratory*P.O. Box 2008; Oak Ridge, TN 37831-6165

Tel: (865) 574-6783; e-mail: forsbergcw@ornl.gov

Oak Ridge Institute of Continued Learning (ORICL)A Program of Roane State Community College; Oak Ridge Campus

Oak Ridge, TennesseeFebruary 3, 2006

*Managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. The submitted manuscript has been authored by a contractor of the U.S. Government under contract DE-AC05-00OR22725. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to

publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes. File name: ORICL.Feb06

High Temperature ReactorsProduce Heat at Temperatures

above 700ºC (1300ºF)

THTR(FRG)

1986 - 1989

FORT ST. VRAIN(U.S.A.)

1976 - 1989

PEACH BOTTOM 1(U.S.A.)

1967 - 1974

AVR(FRG)

1967 - 1988

DRAGON(U.K.)

1963 - 76

EXPERIMENTAL REACTORSDEMONSTRATION OF

BASIC HTGR TECHNOLOGY

And Then They Were Abandoned…

High-Temperature Helium-Cooled Reactors were Partly Developed

High-Temperature Reactors are BackA Story of Changing Needs and New Technologies

• New needs and technologies− Efficient electricity

production− Liquid fuels− Limited water consumption

• New high-temperature reactor technologies− Gas-Turbine High-

Temperature Helium Reactor− The Advanced High-

Temperature Reactor

Electricity ProductionA New Technology Makes an Old Technology Useful by More Efficiently Converting High-Temperature Heat to Electricity

Brayton Power (Jet Engine) Cycles may Make High-Temperature Reactors Viable

(Helium or Nitrogen Brayton Power Cycles)

• High-temperature heat is only useful if it can be converted to electricity

• Steam turbines, the traditional heat-to-electricity technology, have historically had a temperature limit of ~ 550ºC

• New Brayton cycles can efficiently convert high-temperature heat to electricity and makes high-temperature reactors more useful

• Boost heat-to-electricity efficiency from 40 to 50%

GE Power Systems MS7001FB

General Atomics GT-MHR Power Conversion Unit (Russian Design)

Liquid Fuels(New Need for Alternative Fuel Sources)

05-021

The Age of Oil for Fuels is Closing

1900 1920 1940 1960 1980 20000

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20

30

40

50

60

0

10

20

30

40

50

60

Dis

cove

ries

(bill

ion

bbl/y

ear)

Prod

uctio

n (b

illio

n bb

l/yea

r)

Discovery

Consumption

Oil and Gas J.; Feb. 21, 2005

Conventional Futures: Liquid Fuels will be Made from Heavy Oils and Tar Sands

(Lower Hydrogen-to-Carbon Ratios)

• Tar sands and heavy oils are converted to liquid fuels by:− Addition of hydrogen

− Removal of carbon (usually with CO2 to atmosphere)

• Implies massive increase in H2 demand

• Traditional technologies imply major increases in CO2 releases per vehicle mile (greenhouse-gas concern)

Syncrude Canada Ltd. Tar Sands Operations

Conventional Futures Imply Rapidly Increasing Greenhouse Emissions per

Vehicle Mile Traveled

05-055R

Illinois #6 Coal Baseline

Pipeline Natural Gas

Wyoming Sweet Crude Oil

Venezuelan Syncrude

0

200

400

600

800

1000

1200

Gre

enho

use

Impa

cts

(g C

O2-

eq/m

ile in

SU

V)

Conversion/RefiningTransportation/Distribution

End Use CombustionExtraction/Production

Business As Usual

Using Fuel

Making and

Delivering of Fuel

(Fisher-TropschLiquids)

(Fisher-TropschLiquids)

Source of G

reenhouse Impacts

The Electric-Liquid Fuel Future(New Roles for High-Temperature Reactors)

• Plug-in hybrid cars and light trucks

• Hydrogen-rich liquid fuels

Strategy I: Hybrid Engines Enable Plug-In Hybrid Electric Vehicles (PHEVs)

(Recharge Batteries when Vehicle Not in Use)• Electric cars have two major

battery-connected limitations− Limited range− Recharge time (gasoline refueling rate

is ~10 MW) • Advanced hybrid vehicle option

− Electric drive for short trips− Hybrid (gasoline and electricity) for

long trips− Recharge battery over night (plug in)

• Reduction in oil consumption• Alternative to the strategic

petroleum reserve• Cuts greenhouse emissions by

using clean electric sources

Courtesy of the Electric Power Research Institute

Prototypes in the Field

PHEV Annual Gasoline ConsumptionConnecting Transportation to the Electric Grid

Compact Sedan

Midsize Sedan

Midsize SUV

Fullsize SUV

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100

200

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400

500

600

700

800

900

Ann

ual G

asol

ine

Con

sum

ptio

n (g

allo

ns)

Conventional Vehicle"No-Plug" HybridPlug-in HEV, 20 mile EV rangePlug-in HEV, 60 mile EV range

Courtesy of the Electric Power Research Institute

05-074

Strategy II: Hydrogen for Increasing Liquid Fuel per Unit of Feedstock and Reduce Emissions

Fossil Feedstock

(Oil,Tar Sands,

Coal)

Refinery

Furnace

Heat

H2 and O2

Nuclear Hydrogen

Refinery

Furnace

Heat

H2

HydrogenProduction

Carbon

Carbon

Liquid Fuel

Liquid Fuel

Carbon Dioxide

Releasesto

Atmosphere

TransportServices

TransportServices

Current Approach

FutureApproach

Synergistic Fossil and Nuclear H2

All Fossil Carbon Converted to Liquid Fuels No Carbon Release from Fuel Production

Hydrogen sources: nuclear, renewables, and coal with carbon dioxide sequestration

Zero-Greenhouse-Gas Liquids Fuel Strategy

06-007

Near-Term• Biomass• Trash• Sewage

Refinery

Furnace

Heat

Hydrogen

Nuclear Hydrogen

Carbon

Liquid Fuel

TransportServices

Non-FossilCarbon

Feedstock

• Cement Production

• Air• Seawater

Long-Term

Carbon Dioxide

Releasesto

Atmosphere

(Transition to longer-term liquid fuels; creates infrastructure for direct use of hydrogen if that technology is successful)

Recycle From Atmosphere or Intercept CO2 To Atmosphere

Nuclear H2 Production Options(An Incentive for Developing High-Temperature Reactors)

TodayInput: Electricity

ElectrolysisElectricity + 2H20 → 2H2 + O2

High-Temperature ElectrolysisElectricity + 2H20 (Steam) → 2H2 + O2

Hybrid CyclesHeat + Electricity + 2H20 → 2H2 + O2

Thermochemical CyclesHeat + 2H20 → 2H2 + O2

FutureInput: Lower cost high-

temperature heat

Water-Energy Conflicts(Growing Demands for Water)

05-077

Electric Power Plants are Major

Consumers of Water

04-083

High-Temperature Reactors Reduce Water Requirements and Enable

Dry Cooling

30 35 40 45 60500

0.5

1.0

1.5

2.0

2.5

Hea

t Rej

ectio

n (k

W(t)

/kW

(e)

Efficiency55

Existing Reactors

High Temp Reactors

Cut Cooling Demand in Half

→ →

Dry Cooling for Electricity Generation

Thermal Power Plant Dry Cooling(ACC at PacifiCorp’s Wyodak Power Plant (Courtesy of R. Garan)

High-Temperature Reactors

Efficient Electricity ProductionHydrogen Production

Minimal Water Consumption

Two Types of High-Temperature Reactors are Being Developed(MHTGR Near-term; AHTR Midterm)

Modular High-Temperature Gas-Cooled Reactors

Gas-Cooled: 600 MW(t); Near-Term Option

81m70m

Advanced High-Temperature ReactorLiquid-Salt-Cooled: 2400 MW(t)

Longer-term Option

Per Peterson (Berkeley): American Nuclear Society 2004 Winter Meeting

Both Reactor Concepts Use the Same Fuel Type

• Coated-particle graphite-matrix fuel

• Only demonstrated high-temperature fuel

• Two fuel variants− Hexagonal block

(shown)− Pebble bed

• Peak operating temperature: 1250ºC

Only Two Reactor Coolants areChemically Compatible with Graphite-

Matrix Fuel(Two Reactor Options Based on Choice of Coolant)

Helium(High Pressure/Transparent)

Liquid Fluoride Salts(Low Pressure/Transparent)

Modular High-Temperature Gas-Cooled Reactor

Advanced High-Temperature Reactor

The Advanced High-Temperature Reactor

Combining Different Technologies in a New Way

New Concept Being Developed at ORNL(Partnerships with Framatome, University of California at Berkeley,

University of Wisconsin, Argonne National Laboratory, Sandia National Laboratory, and Idaho National Laboratory)

Passively Safe Pool-Type Reactor Designs

High-Temperature Coated-Particle

Fuel

The AdvancedHigh-Temperature

Reactor Combining Four Existing

Technologies in a New WayGeneral Electric

S-PRISM

High-Temperature, Low-Pressure

Transparent Liquid-Salt Coolant

Brayton Power Cycles

GE Power Systems MS7001FB

There is Significant Experience with Molten and Liquid Fluoride Salts

Good Heat Transfer, Low-Pressure Operation, and Transparent (In-Service Inspection)

Liquid Fluoride Salts were Used in Molten Salt Reactors with Fuel in Coolant

(Molten Salt Reactor Experiment)

Molten Fluoride Salts are Used to Make Aluminum in Graphite Baths at 1000°C

The AHTR Uses Coated-Particle Fuel(Peak Operating Temperature: 1250ºC; Failure Temperature: >1600ºC)

Same Fuel Originally

Developed for Gas-Cooled High-

Temperature Reactors

2400 MW(t)

Brayton Power Cycles Convert the Heat to Electricity

(Helium or Nitrogen Brayton Power Cycles)• Developed from

aircraft jet engines• Required 50 years of

development before useful for the utility industry

• Electric utility needs− Reliability: Measured

in years, not 1000s of hours as for aircraft

− Cost is controlling. Economics, not performance (military) is the first requirement

GE Power Systems MS7001FB

General Atomics GT-MHR Power Conversion Unit (Russian Design)

AHTR Facility Layouts are Based on Sodium-Cooled Fast Reactors

Low Pressure, High Temperature, Liquid Cooled

General Electric S-PRISM

Schematic of Advanced High-Temperature Reactor

• 705ºC: 48.0%• 800ºC: 51.5%

Efficiency Depends upon Temperature

Liquid Cooling Allows Large Reactors with Passive Decay Heat Removed

05-023

Core

Alternative Decay Heat Removal Options to Move Heat to Vessel Surface or Heat Exchanger

Liquid(1000s of MW(t))

Gas(~600 MW(t))

Convective Cooling(~50º C Difference in Liquid Temperature)

Conduction Cooling(~1000º C Difference in Fuel Temperature)

• Passive decay-heat removal systems can remove heat from:− Vessel wall

− Liquid coolant

• Passive decay-heat removal limited by heat transport from fuel to vessel or heat exchanger− Gas-cooled reactor:

Conduction heat transfer: limited heat removal

− Liquid-cooled reactor: Convective heat transfer: no power limit

Nuclear Reactor EconomicsThe Incentive to Develop the AHTR

Coolant Properties Impact Reactor Size and Cost

(Determine Pipe, Valve, and Heat Exchanger Sizes)

03-258

10001000540320Outlet Temp (ºC)

67566Coolant Velocity (m/s)

0.697.070.6915.5Pressure (MPa)

Liquid SaltHeliumSodium (LMR)

Water (PWR)

Number of 1-m-diam. pipes needed to transport 1000 MW(t)

with 100ºC rise in coolant temperature

Reactor Comparison of Building Volume, Concrete Volume, and Steel Consumption Based on Arrangement Drawings

(High-Temperature Reactors are Potentially Competitive Sources of Energy)

Per Peterson (Berkeley): American Nuclear Society 2004 Winter Meeting

0.00

0.50

1.00

1.50

2.00

2.50

1970sPWR

1970sBWR

EPR ABWR ESBWR GT-MHR AHTR-IT

Building volume (relative to 336 m3/MWe)Concrete volume (relative to 75 m3/MWe)Steel (relative to 36 MT/MWe)

Non-nuclear input

Nuclear input

1000 MWe 1000 MWe 1600MWe 1350 MWe 1550 MWe 286 MWe 1235 MWe

←Near-Term Options→

Midterm Option

Conclusions• Technology options are created by

new technologies and new needs• High-temperature reactor rebirth

driven by three factors− New method to efficiently convert

heat to electricity− Need for liquid fuels− Need to reduce water consumption

while producing electricity• Two high-temperature reactor

options− Helium cooled (near-term)− Liquid-salt cooled (longer-term)

• The path to any new technology is long and complicated

• The AHTR was originated at ORNL and is one new direction for nuclear energy