Thorium and the Liquid-Fluoride Thorium Reactor Concept

World Energy Consumption is Rapidly EscalatingFuture Energy Consumption Has Been Significantly Underestimated

In 2007, the world consumed*:

5.3 billion tonnes of coal (128 quads**)

31.1 billion barrels of oil (180 quads)

2.92 trillion m3 of natural gas (105 quads)

65 million kg of uranium ore (25 quads)

Contained 16,000 MT of thorium!

**1 quad = 1 quadrillion BTU = 172 million barrels (Mbbl) of crude oil

*Source: BP Statistical Review of World Energy 2008

29 quads of hydroelectricity

Dominated by Hydrocarbons

Year US World

2010 108 510

2020 121 613

2030 134 722

***Source: Energy Information Administration Outlook 2006

Total Energy Demand Projections (quads)***

In a global warming environment, where will the world turn for safe, abundant, low-cost energy?In a global warming environment, where will the world turn for safe, abundant, low-cost energy?

The Binding Energy of Matter

Electrons have binding energies of eV’s.

Nucleons (protons and neutrons) have binding energies of millions of eV’s.

Supernova—Birth of the Heavy ElementsThorium, uranium, and all the other heavy elements were formed in the final moments of a supernova explosion billions of years ago.

Our solar system: the Sun, planets, Earth, Moon, and Our solar system: the Sun, planets, Earth, Moon, and asteroids formed from the remnants of this material.asteroids formed from the remnants of this material.

Fissile fuel has extraordinary energy density!

23 million kilowatt-hours per kilogram!

Energy Generation Comparison

6 kg of fissile material in a liquid-fluoride reactor has the energy equivalent (66,000

MW*hr electrical*) of:

=

230 train cars (25,000 MT) of bituminous coal or,

600 train cars (66,000 MT) of brown coal,

(Source: World Coal Institute)

or, 440 million cubic feet of natural gas (15% of a 125,000 cubic meter LNG tanker),

or, 300 kg of enriched (3%) uranium in a pressurized water reactor.

*Each ounce of thorium can therefore produce $14,000-24,000 of electricity (at $0.04-0.07/kW*hr)

Uranium-238(99.3% of all U)

Thorium-232(100% of all Th)

Uranium-235(0.7% of all U)

Uranium-233

Plutonium-239

Nature gave us three options for fissile fuel

The fission of U-235 was discovered by Otto Hahn and Lise Meitner in 1938.

Pu-239 as a fissile fuel was discovered by Glenn Seaborg in March 1941.

U-233 as a fissile fuel was discovered by Seaborg’s student John Gofman in February 1942.

Uranium-235(“highly enriched

uranium”)

Could weapons be made from the fissile material?

Isotope separation plant (Y-12)

Natural uranium

Hiroshima, 8/6/1945

Depleted uranium

Isotope Production Reactor (Hanford)

Pu separation from exposed U (PUREX)

Trinity, 7/16/1945 Nagasaki, 8/9/1945

Thorium?Isotope

Production Reactor

uranium separation

from exposed thorium

PROBLEM: U-233 is contaminated with U-232, whose decay chain emits HARD gamma rays that make fabrication, utilization and deployment of weapons VERY difficult and impractical relative to other options. Thorium was not pursued.

U-232 decays into Tl-208, a HARD gamma emitter

Thallium-208 emits “hard” 2.6 MeV gamma-rays as part of its nuclear decay.

These gamma rays destroy the electonics and explosives that control detonation.

They require thick lead shielding and have a distinctive and easily detectable signature.

232U

Uranium-232 follows the same decay chain as thorium-232, but it follows it millions of times faster!

This is because 232Th has a 14 billion-year half-life, but 232U has only an 74 year half-life!

Once it starts down “the hill” it gets to thallium-208 (the gamma emitter) in just a few weeks!

14 billion years to make this jump

Some 232U starts decaying

immediately

1.91 yr

3.64 d

55 sec

0.16 sec

1.91 yr

3.64 d

55 sec

1.91 yr

3.64 d

U-232 Formation in the Thorium Fuel Cycle

1944: A tale of two isotopes…

Enrico Fermi argued for a program of fast-breeder reactors using uranium-238 as the fertile material and plutonium-239 as the fissile material.

His argument was based on the breeding ratio of Pu-239 at fast neutron energies.

Argonne National Lab followed Fermi’s path and built the EBR-1 and EBR-2.

Eugene Wigner argued for a thermal-breeder program using thorium as the fertile material and U-233 as the fissile material.

Although large breeding gains were not possible, THERMAL breeding was possible, with enhanced safety.

Wigner’s protégé, Alvin Weinberg, followed Wigner’s path at the Oak Ridge National Lab.

Can Nuclear Reactions be Sustained in Natural Uranium?

Not with thermal neutrons—need 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.

Spectrum Moderated Spectrum SpectrumFastThermal

Start

Reality

Pu-240Production

Produces long-lived Actinides

– Yucca Mtn

Greater propensity to absorb neutrons

• Goal of fast breeder reactors

• Most of Pu burned

• Fast reactors keep neutrons here, but at a high price:

– Safety– More fuel (5x)

Fission/Absorption Cross Sections

Neutrons are moderated through collisions

Neutron born at high energy (1-2 MeV).

Neutron moderated to thermal energy (<<1 eV).

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.

Lifetime of a Typical Uranium Fuel Element

Conventional fuel elements are fabricated from uranium pellets and formed into fuel assemblies

They are then irradiated in a nuclear reactor, where most of the U-235 content of the fuel “burns” out and releases energy.

Finally, they are placed in a spent fuel cooling pond where decay heat from radioactive fission products is removed by circulating water.

Typical Pressurized-Water Reactor Containment

This structure is steel-lined reinforced concrete, designed to withstand the overpressure expected if all the primary coolant were released in an accident.

Sprays and cooling systems (such as the ice condenser) are available for washing released radioactivity out of the containment atmosphere and for cooling the internal atmosphere, thereby keeping the pressure below the containment design pressure.

The basic purpose of the containment system, including its spray and cooling functions, is to minimize the amount of released radioactivity that escapes to the external environment.

Radiotoxicity of fission products over time

Ingestion toxicity of the fission products from a uranium-fueled LWR.

Inhalation toxicity of the fission products from a uranium-fueled LWR.

Can Nuclear Reactions be Sustained in Natural Thorium?

Yes! Enough neutrons to sustain reaction produced at thermal fission. Does not need fast neutron reactors—needs neutronic efficiency.

Thermal Spectrum Moderated Spectrum SpectrumFast

No Advantage for Thorium

U-234

U-232 contaminates U-233 and cannot be removed

– Prevents U-233 being used as weapon

Start

Thorium-Uranium Breeding Cycle

Uranium-233 is fissile and will fission when struck by a neutron, releasing energy and 2 to 3 neutrons. One neutron is needed to sustain the chain-reaction, one neutron is needed for breeding, and any remainder can be used to breed additional fuel.

Thorium-232 absorbs a neutron from fission and

becomes thorium-233.

Th-232

Th-233

Pa-233

U-233

Thorium-233 decays quickly (half-life of 22.3

min) to protactinium-233 by emitting a beta particle (an electron).

Protactinium-233 decays more slowly (half-life of 27 days) to uranium-233 by emitting a beta particle (an electron).

It is important that Pa-233 NOT absorb a neutron before it decays to U-233—it should be isolated from any neutrons until it decays.

1944: A tale of two isotopes…

“But Eugene, how will you reprocess the thorium fuel effectively?”

“We’ll build a fluid-fueled reactor, that’s how…”

ORNL Fluid-Fueled Thorium Reactor Progress (1947-1960)

1947 – Eugene Wigner proposes a fluid-

fueled thorium reactor

1950 – Alvin Weinberg becomes

ORNL director

1952 – Homogeneous Reactor Experiment (HRE-1) built and operated

successfully (100 kWe, 550K)

1958 – Homogeneous Reactor Experiment-2 proposed with 5 MW of

power

1959 – AEC convenes “Fluid Fuels Task Force” to choose between aqueous homogeneous reactor, liquid fluoride, and liquid-metal-fueled reactor. Fluoride reactor is chosen and AHR is cancelled.

Weinberg attempts to keep both aqueous and fluoride reactor efforts going in parallel but ultimately decides to pursue fluoride reactor.

Aircraft Nuclear Program

Between 1946 and 1961, the USAF sought to develop a long-range bomber based on nuclear power.

The Aircraft Nuclear Program had unique requirements, some very similar to a space reactor.

High temperature operation (>1500° F) Critical for turbojet efficiency 3X higher than sub reactors

Lightweight design Compact core for minimal shielding Low-pressure operation

Ease of operability Inherent safety and control Easily removeable

Ionically-bonded fluids are impervious to radiation

The basic problem in nuclear fuel is that it is covalently bonded and in a solid form.

If the fuel were a fluid salt, its ionic bonds would be impervious to radiation damage and the fluid form would allow easy extraction of fission product gases, thus permitting unlimited burnup.

The Aircraft Reactor Experiment (ARE)

In order to test the liquid-fluoride reactor concept, a solid-core, sodium-cooled reactor was hastily converted into a proof-of-concept liquid-fluoride reactor.

The Aircraft Reactor Experiment ran for 100 hours at the highest temperatures ever achieved by a nuclear reactor (1150 K).

Operated from 11/03/54 to 11/12/54 Liquid-fluoride salt circulated through

beryllium reflector in Inconel tubes 235UF4 dissolved in NaF-ZrF4

Produced 2.5 MW of thermal power Gaseous fission products were removed

naturally through pumping action Very stable operation due to high negative

reactivity coefficient Demonstrated load-following operation

without control rods

It wasn’t that I had suddenly become converted to a belief in nuclear airplanes. It was rather that this was the only avenue open to ORNL for continuing in reactor development.

That the purpose was unattainable, if not foolish, was not so important:

A high-temperature reactor could be useful for other purposes even if it never propelled an airplane…

—Alvin Weinberg

Aircraft Nuclear Program allowed ORNL to develop reactors

ORNL Aircraft Nuclear Reactor Progress (1949-1960)

1949 – Nuclear Aircraft Concept formulated

1951 – R.C. Briant proposed Liquid-Fluoride Reactor

1952, 1953 – Early designs for aircraft fluoride reactor

1954 – Aircraft Reactor Experiment (ARE) built and operated successfully

(2500 kWt, 1150K)

1955 – 60 MWt Aircraft Reactor Test (ART, “Fireball”) proposed for

aircraft reactor

1960 – Nuclear Aircraft Program cancelled in

favor of ICBMs

Fluid-Fueled Reactors for Thorium Energy

Uranium tetrafluoride dissolved in lithium fluoride/beryllium fluoride.

Thorium dissolved as a tetrafluoride. Two built and operated.

Aqueous Homogenous Reactor (ORNL)

Liquid-Fluoride Reactor (ORNL)

Liquid-Metal Fuel Reactor (BNL)

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. Conceptual—none built and

operated.

Molten Salt Reactor Experiment (1965-1969)

LFTR is totally passively safe in case of accident

In the event of TOTAL loss of power, the freeze plug melts and the core salt drains into a passively cooled configuration where nuclear fission is impossible.

The reactor is equipped with a “freeze plug”—an open line where a frozen plug of salt is blocking the flow.

The plug is kept frozen by an external cooling fan.

Freeze Plug

Drain Tank

A “Modern” Fluoride Reactor

LFTR produces far less mining waste than LWR ( ~4000:1 ratio)

Mining 800,000 MT of ore containing 0.2% uranium (260 MT U)

Uranium fuel cycle calculations done using WISE nuclear fuel material calculator: http://www.wise-uranium.org/nfcm.html

Generates ~600,000 MT of waste rock

Conversion to natural UF6 (247 MT U)

Generates 170 MT of solid waste and 1600 m3 of liquid waste

Milling and processing to yellowcake—natural U3O8

(248 MT U)

Generates 130,000 MT of mill tailings

Mining 200 MT of ore containing 0.5%

thorium (1 MT Th)

Generates ~199 MT of waste rock

Milling and processing to thorium nitrate ThNO3 (1 MT Th)

Generates 0.1 MT of mill tailings and 50 kg of aqueous wastes

1 GW*yr of electricity from a uranium-fueled light-water reactor

1 GW*yr of electricity from a thorium-fueled liquid-fluoride reactor

LFTR produces less operational waste than LWR,(mission: make 1000 MW of electricity for one year)

250 t of natural uranium

containing 1.75 t U-235

35 t of enriched uranium (1.15 t U-235)

215 t of depleted uranium containing 0.6 t U-235—disposal plans uncertain.

Uranium-235 content is “burned” out of the fuel; some

plutonium is formed and burned

35 t of spent fuel stored on-site until disposal at Yucca Mountain. It contains:

• 33.4 t uranium-238

• 0.3 t uranium-235

• 0.3 t plutonium

• 1.0 t fission products.

One tonne of natural thorium

Thorium introduced into blanket of fluoride reactor; completely converted to

uranium-233 and “burned”.

One tonne of fission products; no uranium, plutonium, or other actinides.

Within 10 years, 83% of fission products are stable and can be

partitioned and sold.

The remaining 17% fission products go to geologic isolation for

~300 years.

Thorium Fuel Supply

Thorium is abundant around the world and rich in energy

Estimated world reserve base of 1.4 million MT US has about 20% of the world reserve base

A single mine site in Idaho could produce 4500 MT of thorium/year

US currently would use about 400 MT/year for electricity production

The United States has buried 3200 metric tons of thorium

nitrate in the Nevada desert.

World Thorium Resources

Country

Australia

India

USA

Norway

Canada

South Africa

Brazil

Other countries

World total

Reserve Base (tons)340,000

300,000

300,000

180,000

100,000

39,000

18,000

100,000

1,400,000

Source: U.S. Geological Survey, Mineral Commodity Summaries, January 2008

A single mine site in Idaho could recover 4500 MT of thorium per year

ANWR times 6 in the Nevada desert

Between 1957 and 1964, the Defense National Stockpile Center procured 3215 metric tonnes of thorium from suppliers in France and India.

Recently, due to “lack of demand”, they decided to bury this entire inventory at the Nevada Test Site.

This thorium is equivalent to 240 quads of energy*, if completely consumed in a liquid-fluoride reactor.

*This is based on an energy release of ~200 Mev/232 amu and complete consumption. This energy can be converted to electricity at ~50% efficiency using a multiple-reheat helium gas turbine; or to hydrogen at ~50% efficiency using a thermo-chemical process such as the sulfur-iodine process.

Thorium Resources in the United States

1

3

4 5

6

78

910

11

13

1415

16

17

18

Lemhi Pass, Idaho (best mining site in US)3200 metric tonnes of thorium nitrate buried at Nevada Test Site

Conway Shale, NH

Monazite beach sands in Georgia and Florida

LFTR could produce many valuable by-products

Liquid-Fluoride Thorium Reactor

Liquid-Fluoride Thorium Reactor

Desalination to Potable WaterFacilities Heating

These products may be as important as electricity production

Thorium

Separated Fission Products

Strontium-90 for radioisotope powerCesium-137 for medical sterilizationRhodium, Ruthenium as stable rare-earthsTechnetium-99 as catalystMolybdenum-99 for medical diagnosticsIodine-131 for cancer treatmentXenon for ion engines

Electrical Generation (50% efficiency)

Low-temp Waste Heat

Power Conversion

Power Conversion Electrical

loadElectrolytic H2Process HeatProcess Heat Coal-Syn-Fuel Conversion

Thermo-chemical H2Oil shale/tar sands extraction

Crude oil “cracking”Hydrogen fuel cellAmmonia (NH3) Generation

Fertilizer for AgricultureAutomotive Fuel Cell (very simple)

The byproducts of conventional reactors are more limited

Light-Water Reactor

Light-Water Reactor

Uranium

Electrical Generation (35% efficiency)

Low-temp Waste Heat

Power Conversion

Power Conversion Electrical

loadElectrolytic H2

Crude oil “cracking”Hydrogen fuel cellAmmonia (NH3) Generation

Fertilizer for AgricultureAutomotive Fuel Cell (very simple)

LFTR can be environmentally friendly

Open Pit Mine

Nuclear Waste

Large Cooling Towers

Concern about waste disposal has hampered nuclear industry growth – and energy supply

Concern about waste disposal has hampered nuclear industry growth – and energy supply

Does not produce “green house” gases

Can be air-cooled Consequently does not vent heat into rivers and lakes Smaller cooling towers

Little operations waste Option of retaining waste storage on site

Operational waste products decay very rapidly

Little mining waste No large open pits, large waste “mountains”

Why wasn’t this done? No Plutonium Production!

Alvin Weinberg:“Why didn't the molten-salt system, so elegant and so well

thought-out, prevail? I've already given the political reason: that the plutonium fast breeder arrived first and was therefore able to consolidate its political position within the AEC. But there was another, more technical reason. [Fluoride reactor] technology is entirely different from the technology of any other reactor. To the inexperienced, [fluoride] technology is daunting…

“Mac” MacPherson:The political and technical support for the program in the

United States was too thin geographically…only at ORNL was the technology really understood and appreciated. The thorium-fueled fluoride reactor program was in competition with the plutonium fast breeder program, which got an early start and had copious government development funds being spent in many parts of the United States.

Alvin Weinberg:“It was a successful technology that was dropped because

it was too different from the main lines of reactor development… I hope that in a second nuclear era, the [fluoride-reactor] technology will be resurrected.”

No pressure vessel required Liquid fuel requires no expensive fuel fabrication and

qualification Smaller power conversion system No steam generators required Factory built-modular construction

Scalable: 100 KW to multi GW Smaller containment building needed

Steam vs. fluids Simpler operation

No operational control rods No re-fueling shut down Significantly lower maintenance Significantly smaller staff

Significantly lower capital costs Lower regulatory burden

LFTR could cost much less than LWR

The Current Plan is to Dispose Fuel in Yucca Mountain

Tunnels in Yucca Mountain

Year

2000 2010 2020 2030 2040 2050

Spe

nt F

uel,

met

ric to

ns

0

100x103

200x103

300x103

Capacity based on limited exploration

Legislated capacity

6-Lab Strategy

MIT Study

EIA 1.5% Growth

Constant 100 GWeSecretarialrecommendation

Projected Spent Fuel Accumulation without Reprocessing

DOE Plan (“GNEP”) for Spent Nuclear Fuel

Uranium-Plutonium Fuel Cycle

UraniumMining

UraniumMilling

UraniumPurification

Natural Uranium

Purification

UraniumEnrichment

IrradiatedFuel

Storage

ConverterReactor

ConverterFuel

Reprocessing

Fuel Fabrication

Conversionto UO2

PermanentWaste

Storage

InterimWaste

Storage

Uranium Ore

Uranium Concentrates

Uranyl Nitrate

PuO2-UO3Stockpile

ConversionTo (Pu,U)O2

BreederFuel

Reprocessing

IrradiatedFuel

Storage

FastBreederReactor

BreederFuel

Fabrication

Conversionto UO2

DepletedUF6

Stockpile

Recycled Mixed PuO2-UO3

Converter High-Level

Waste

High-Level Waste

Breeder High-Level

Waste

Recycled Mixed PuO2-UO3

Irradiated Fuel

Aged Breeder

Fuel

Breeder Fuel

AssembliesDepleted

UO2Depleted

UF6

Enriched UO2

Fuel Assemblies

Irradiated Fuel

Aged Converter

Fuel

Natural UF6

Depleted UF6 ~0.2%

U-235

Enriched UF6

~3% U-235

Natural UO2 or U-metal

Electricity

Electricity

Recycled UF6

Uranium Refining

Recycled Depleted UO3

Mixed Oxides

(Pu,U)O2 ~5% Pu

Mixed Oxides

(Pu,U)O2 ~20% Pu

PuO2-UO3

How does a fluoride reactor use thorium?

FluorideVolatility

VacuumDistillation

Uranium Absorption-Reduction

233,234UF6

7LiF-BeF2-UF4

233UF6

FissionProductWaste

HexafluorideDistillation

FluorideVolatility

7LiF-BeF2

“Bare” Salt

Pa-233Decay Tank

Metallic thorium

MoF6, TcF6, SeF6,RuF5, TeF6, IF7,

Other F6

Fuel Salt

xF6

238U

Core

Blanket

Two-Fluid Reactor

Bism

uth-metal

Reductive E

xtraction C

olumn

Molybdenum and Iodine for Medical Uses

Fertile Salt

Recycle Fertile Salt

Recycle Fuel Salt

Pa

Alternative LFTR/LCFR plan for spent nuclear fuel

Spent Nuclear Fuel from Light-Water Reactors

Step 1: Fluorinate it!

Remove uranium as UF6, which is then either re-

enriched or buried.

UO2 + F2 -> UF4

Zr + F2 -> ZrF4

(TRU)O2 + F2 -> PuF3,NpF4,AmF3, etc.

(FP)O2 + F2 -> (FP)F

Step 2: Use aluminum to remove the TRU-fluorides from the mix, leaving the

fission products

Step 3: Chlorinate (with 37Cl) the metallic TRUs, forming fuel for the chloride reactor.

Step 4: BURN TRU-chlorides in the fast-spectrum chloride reactor, destroying them (through fission) and forming new U-233 for fluoride reactors (LFTR).

Step 5: Dispose of FP-fluorides in 300-yr disposal sites (not Yucca Mtn) and use U-233 from TRU destruction to start LFTRs that produce no further TRUs.

Cost Low capital cost thru small facility and compact power conversion

Reactor operates at ambient pressure No expanding gases (steam) to drive large containment High-pressure helium gas turbine system

Primary fuel (thorium) is inexpensive Simple fuel cycle processing, all done on site

Cost advantages come from size and complexity reductions

GE Advanced Boiling Water Reactor (light-water reactor)

Fluoride-cooled reactor with helium gas turbine power conversion system

Reduction in core size, complexity,

fuel cost, and turbomachinery

Examples of Mobile Nuclear Reactors

Coastal Populations in US

Coastal Populations in Asia

“Gentlemen, our mission…”

Underwater Nuclear Powerplants?

Underwater Nuclear Powerplants?

Underwater Nuclear Powerplants?

Conclusions

Thorium is abundant, has incredible energy density, and can be utilized in thermal-spectrum reactors World thorium energy supplies will last for tens of thousands of years

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 world would be safer with thorium-fueled reactors Not an avenue for weapons production

The US should adopt a new “business model” for nuclear power for the country’s long term strategic needs

Learn more at:

http://thoriumenergy.blogspot.com/

http://www.energyfromthorium.com/

http://nucleargreen.blogspot.com/

Executive SummaryLiquid Fluoride Thorium Reactor (LFTR)

A nuclear technology that was demonstrated successfully 40 years ago Highly energy efficient and able to completely utilize nuclear fuel Intrinsically safe due to the physics

Meltdown-proof and self-controlling Runs at 1 atmosphere pressure Use of fluid allows the burning of all fuel, thus no need for control rods, periodic solid fuel

element replacement, etc. Produces orders of magnitude less waste than traditional light water reactors

(LWR) Thorium reactor produces 30-40 times less nuclear waste that a light water reactor Waste from LFTR need be stored for much less time than those from a LWR

Current supply of nuclear waste can be burned down in the LFTR to waste products that need to be stored for much less time No transuranic element production Yucca Mountain not a requirement for long term waste storage

Can use air or water for cooling Critical for arid areas such as the Western United States

Unsuitable for nuclear weapons Thorium fuel supply is abundant and produces less mining waste than uranium

Thorium four times as common in the Earth’s crust as uranium Could provide the US electrical energy needs for hundreds to thousands of years

and provide base power needed for non-electrical energy and resource production Coal gasification, water desalinization, oil sands and oil shale processing, etc.