Thorium and the LiquidFluoride Reactor: A Global Energy Option

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Thorium and the Liquid-Fluoride ReactorA Global
Energy Option

• Kirk Sorensen
• Tuesday, October 10, 2006
• Ohio State University

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Energythe Foundation of Modern Life
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World Primary Energy Consumption
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Crude Oil
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Crude Oil Reserves
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Crude Oil Consumption Per Capita
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Natural Gas
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Natural Gas Reserves
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Natural Gas Consumption Per Capita
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Coal
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Coal Reserves
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Power Generation Resource Inputs

• Nuclear 1970s vintage PWR, 90 capacity factor,
  60 year life 1
• 40 MT steel / MW(average)
• 190 m3 concrete / MW(average)
• Wind 1990s vintage, 6.4 m/s average wind speed,
  25 capacity factor, 15 year life 2
• 460 MT steel / MW (average)
• 870 m3 concrete / MW(average)
• Coal 78 capacity factor, 30 year life 2
• 98 MT steel / MW(average)
• 160 m3 concrete / MW(average)
• Natural Gas Combined Cycle 75 capacity factor,
  30 year life 3
• 3.3 MT steel / MW(average)
• 27 m3 concrete / MW(average)

1. R.H. Bryan and I.T. Dudley, Estimated
Quantities of Materials Contained in a 1000-MW(e)
PWR Power Plant, Oak Ridge National Laboratory,
TM-4515, June (1974) 2. S. Pacca and A. Horvath,
Environ. Sci. Technol., 36, 3194-3200 (2002). 3.
P.J. Meier, Life-Cycle Assessment of Electricity
Generation Systems and Applications for Climate
Change Policy Analysis, U. WisconsinReport
UWFDM-1181, August, 2002
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1998 Energy Consumption

• In 1998, the world consumed

5 billion tonnes of coal (112 quads)
27 billion barrels of oil (156 quads)
Contained 16,000 MT of thorium!
82 trillion ft3 of natural gas (84 quads)
65,000 metric tonnes of uranium ore (24 quads)
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1998 Energy Consumption

• The equivalent amount of thorium would be

5000 metric tonnes of thorium (376 quads)
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3200 MT of thorium stored until recently
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A single mine site in Idaho could recover 4500
MT of thorium per year
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SupernovaBirth of the Heavy Elements
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Three Basic Fuels
Thorium-232 (100 of all Th)
Uranium-233
Uranium-235 (0.7 of all U)
Uranium-238 (99.3 of all U)
Plutonium-239
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Thorium and Uranium Abundant in the Earths Crust
Thorium more common than boron, uranium, tin,
tungsten, and precious metals. Nearly as common
as lead.
Uranium commonly found (once it was looked for!)
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Energy from the Fission Reaction

• Fission releases a large amount of
  energytypically about 200 MeV per fission
  reaction.
• 200 MeV/232 amu of thorium is equivalent to
• 23.1 GWhr/kg
• At this rate of energy production, one quad of
  energy (quadrillion BTU) would require
• 12.7 metric tonnes of thorium per quad.
• But its not that simple, is it?

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Fission is more likely when neutrons are moderated
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Can Nuclear Reactions be Sustained in Natural
Uranium?
Not with thermal neutronsneed more than 2
neutrons to sustain reaction (one for conversion,
one for fission)not enough neutrons produced at
thermal energies. Must use fast neutron reactors.
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Can Nuclear Reactions be Sustained in Natural
Thorium?
Yes! Enough neutrons to sustain reaction
produced at thermal fission. Does not need fast
neutron reactorsneeds neutronic efficiency.
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Fuel Chains
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Thorium Fuel Cycle
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Incomplete Combustion
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Radiation Damage Limits Energy Release

• Does a typical nuclear reactor extract that much
  energy from its nuclear fuel?
• No, the burnup of the fuel is limited by damage
  to the fuel itself.
• Typically, the reactor will only be able to
  extract a portion of the energy from the fuel
  before radiation damage to the fuel itself
  becomes too extreme.
• Radiation damage is caused by
• Noble gas (krypton, xenon) buildup
• Disturbance to the fuel lattice caused by fission
  fragments and neutron flux
• As the fuel swells and distorts, it can cause the
  cladding around the fuel to rupture and release
  fission products into the coolant.

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Ionically-bonded fluids are impervious to
radiation
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Fluoride Salts Have Innate Chemical Stability
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Aircraft Nuclear Propulsion Program

• 1946 1961
• 1B Investment
• Pioneering work
• ZrH fuels
• Liquid-fluoride fuels
• Liquid metal heat transfer
• Light-weight metals
• Advanced IC
• High temperature corrosion resistant materials
• Challenges
• Changing mission definitions
• Two customers (Air Force and AEC)

Photo of NB-36
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Early Ideas

• The liquid-fluoride reactor was originally
  conceived as a response to the demands of the
  Nuclear Aircraft project for a lightweight
  reactor.
• High core power density
• High-temperature/low-pressure operation
• Ease of maintenance and operation
• Limited operational life (100 hours)
• Early designs reflected these goals
• No fertile material in core (conversion ratio
  0.0)
• Super-high power densities (megawatts per liter)
• Reactive liquid-metal coolants (liquid sodium,
  NaK)
• These designs were not intended to produce
  electrical power for utilities, rather heat for a
  nuclear-heated turbojet.
• The Nuclear Aircraft was considered a doomsday
  weapon.

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Nuclear Aircraft Concept

• Convair B-36 X-6
• Four nuclear-powered turbojets
• 200 MW thermal reactor

Liquid-Fluoride Reactor
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1954 Aircraft Reactor Experiment (ARE)
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ARE Demonstrated Liquid-Fluoride Reactor
Technology

• Evolution of Na-cooled, solid fuel design
• Fuel NaF-ZrF4-UF4 (53-41-6) (mole)
• Operated gt 100MW-hr
• Max. fuel temp. 882C
• Very large neg. temp. coeff (-6.1E-5)
• Reactor was slave to load

Core Vol. 1.37 ft3 Loop Vol. 3.60 ft3 Pump
Vol. 1.70 ft3
(Na)
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60 MWt Aircraft Reactor Test

• 1.3 MW/L (max. design)
• 1144K core outlet temp.
• 1500 hr. design life
• 10 ft3 total fuel volume
• 3.2 ft3 core fuel volume

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Fluid-Fueled Reactors for Thorium Energy
Liquid-Fluoride (Molten-Salt) Reactor (ORNL)
Aqueous Homogenous Reactor (ORNL)
Liquid-Metal Fuel Reactor (BNL)

• Uranium tetrafluoride dissolved in lithium
  fluoride/beryllium fluoride.
• Thorium dissolved as a tetrafluoride.
• Two built and operated.

• Uranyl sulfate dissolved in pressurized heavy
  water.
• Thorium oxide in a slurry.
• Two built and operated.

• Uranium metal dissolved in bismuth metal.
• Thorium oxide in a slurry.
• Conceptualnone built and operated.

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Molten-Salt Reactor Program (MSRP) began in 1958
Core Vol. 113.2 ft3 Loop Vol. 57.5 ft3
LiF-BeF2-UF4 Fuel
6 ft
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MSBR58 Reactor Plant Isometric
Image source ORNL-2634 MSRP Status Report, pg 3
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Earliest Concept of the MSRE
Image source ORNL-3014 MSRP-QPR-07/60, pg 4, 7
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MSRE HX Concepts
Image source ORNL-3014 MSRP-QPR-07/60, pg 8, 11
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Molten Salt Reactor Experiment (1965-1969)
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MSRE Plant Layout
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1967 Molten Salt Breeder Reactor (MSBR) Was
Two-Region, Two-Fluid Design

• 1000 MW(e)
• Fuel 7LiF-BeF2-UF4
• Blanket 7LiF-BeF2-ThF4
• Continuous on-line fuel processing
• 45 thermal efficiency
• Many fission products removed on-line allowing
  reactor to operate with less fuel

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Two-Fluid LFRs were easy to process
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1969 Molten Salt Breeder Reactorwas Two-Region,
One-Fluid Design

• Molten Salt Breeder Reactor (MSBR)
• 1000 Mw(e) (2250 MWt)
• 2-region-two-fluid system
• Fuel 7LiF-BeF2-ThF4-UF4
• Breeding ratio 1.06

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One-Fluid LFRs were more challenging
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MSBR72 Core Cell Isometric
Image source ORNL-4832 MSRP-SaPR-08/72, pg 6
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Then things stoppedfor a long, long time.
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Gen-4 Molten-Salt Reactor Concept
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Energy Extraction Comparison
Uranium-fueled light-water reactor 35 GWhr/MT
of natural uranium
33 conversion efficiency (typical steam turbine)
32,000 MWdays/tonne of heavy metal (typical LWR
fuel burnup)
Conversion and fabrication
Conversion to UF6
1000 MWyr of electricity
293 MT of natural U3O8 (248 MT U)
3000 MWyr of thermal energy
39 MT of enriched (3.2) UO2 (35 MT U)
365 MT of natural UF6 (247 MT U)
Thorium-fueled liquid-fluoride reactor 11,000
GWhr/MT of natural thorium
50 conversion efficiency (triple-reheat
closed-cycle helium gas-turbine)
914,000 MWdays/MT 233U (complete burnup)
Thorium metal added to blanket salt through
exchange with protactinium
Conversion to metal
1000 MWyr of electricity
0.8 MT of thorium metal
0.9 MT of natural ThO2
2000 MWyr of thermal energy
0.8 MT of 233Pa formed in reactor blanket from
thorium (decays to 233U)
Uranium fuel cycle calculations done using WISE
nuclear fuel material calculator
http//www.wise-uranium.org/nfcm.html
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Massive Inconsistency
We Americans want it all endless and secure
energy supplies low prices no pollution less
global warming no new power plants (or oil and
gas drilling, either) near people or pristine
places. This is a wonderful wish list, whose only
shortcoming is the minor inconvenience of massive
inconsistency. Robert Samuelson
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Gentlemen, our mission
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Coastal Nuclear Powerplant Complexes
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Floating Nuclear Powerplants?
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Underwater Nuclear Powerplants?
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Underwater Nuclear Powerplants?
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Underwater Nuclear Powerplants?
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Conclusions

• Thorium has innate advantages as a fuel material
  that are worthy of deep and thorough
  investigation.
• Solid-fueled reactors have been disadvantaged in
  using thorium due to their inability to
  continuously reprocess.
• Fluid-fueled reactors, such as the
  liquid-fluoride reactor, offer the promise of
  complete consumption of thorium in energy
  generation.
• The compact nature of the liquid-fluoride
  reactor, when coupled to a helium gas turbine
  system, might allow underwater power generation
  reactors to become a reality.