Liquid Fluoride Thorium ReactorsLiquid Fluoride Thorium Reactorswithout equationswithout equations

∑x<+-=-*±

An overview of liquidAn overview of liquid-fueled liquid-cooled thermal spectrum Thorium breeder reactors and why they

matter.

Rob MorseRob Morse

Science Engineer- Nuclear OptionScience Engineer- Nuclear Option

2012201211

Outline

Motivations for Nuclear Power LFTR overview Nuclear Chemistry Chemistry Myths Questions

22

Power makes a difference.

LFTR wo Equations. Thorium LFTR wo Equations. Thorium power conference, Oct 2009power conference, Oct 2009 33

The NecessitiesThe Necessities

A power source must be-A power source must be- Self regulating when it is ONSelf regulating when it is ON ““Walk away” safe when it is OFFWalk away” safe when it is OFF Inherently safe in case of an ACCIDENTInherently safe in case of an ACCIDENT

LFTR wo Equations. Thorium LFTR wo Equations. Thorium power conference, Oct 2009power conference, Oct 2009 44

Fuel for a lifetime?

You consume a ball of coal You consume a ball of coal 10 meters in diameter…10 meters in diameter…

… …or a ball or thorium 37mm in diameter.or a ball or thorium 37mm in diameter.

LFTR wo Equations. Thorium LFTR wo Equations. Thorium power conference, Oct 2009power conference, Oct 2009 55

Outline

Motivations for Nuclear Power LFTR overview Nuclear Chemistry Chemistry Myths Questions

66

Reactor Basics Reactors make heat through fission and decay.

The heat is then converted into mechanical power and then to electrical power.

Fission is controlled by the neutron population around the nuclear fuel. More neutrons produce more fissions and more heat.

The neutron economy is tightly controlled by material properties, physics, and design.

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Nuclear Fission

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Cross SectionThe probability that the neutron interacts with the

nucleus depends on the neutron’s speed. We describe the probability as an apparent SIZE of the nucleus. The larger the apparent size, the higher the probability. This is a geometric interpretation of a probabilistic quantum mechanical event.

Reaction equations are of the form-Number of events/time = (neutron flux) (spatial

density of target nuclei) ( cross section for the event )

Moderation and Rx Probabilities

Neutron Cross Sections

0

100

200

300

400

500

Fast U-233 fission Fast Thorium absobtion Thermal U-233 fission Thermal Thoriumabsorbtion

>>Fast to Slow>>

bar

ns

(10e

-28

m-s

q)

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Speed?

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Core Options

Standard pressurized water reactor (PWR)– Water flows over a core of ceramic fuel pins.

Water acts as coolant and moderator. Reactivity is controlled by the moderator density and by control rods.

Liquid Fluoride Thorium reactor (LFTR)– A liquid fuel flows though a core of graphite.

The fuel acts as coolant, the graphite as moderator. Reactivity is controlled by the fuel density.

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Temperature Stability

inlet outlet

reactivity

Fuel-coolant

temperature

A power plant with a built in thermostat!A power plant with a built in thermostat!

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Graphite Moderator

Improved reactor designImproved reactor design

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reactivity

temperature

Fuel LoopFuel Loop

The Reactor at “idle”The Reactor at “idle”

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Walk-Away Safe

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Little or no radioactive wasteNo bomb materialsLow cost per power deliveredSmall physical sizePower on demandA wide choice of building sites.

An Efficient DesignAn Efficient Design

LFTR wo Equations. Thorium LFTR wo Equations. Thorium power conference, Oct 2009power conference, Oct 2009 1717

Size matters!Size matters!

Your nuclear waste is the size of a few grains Your nuclear waste is the size of a few grains of rice!of rice!

LFTR wo Equations. Thorium LFTR wo Equations. Thorium power conference, Oct 2009power conference, Oct 2009 1818

Lets Make Power

This is a picture of the waste heat coming from the original LFTR test cell.

The heat transfer fluid (molten salt) is at low pressure. We can use a gas cycle, like a jet engine, to convert heat

into mechanical power. (highly efficient) These plants can run at partial load.

LFTR wo Equations. Thorium LFTR wo Equations. Thorium power conference, Oct 2009power conference, Oct 2009 1919

Outline

Motivations for Nuclear Power LFTR overview Nuclear Chemistry Chemistry Myths Questions

2020

Chart of the Nuclides for LFTR

Uranium (92)

Protactinium (91)

Thorium (90)

Fissile Fuel!

+ N

~22 min half-lifeB-

~27 days half-life

B-

Ref: http://www.nndc.bnl.gov/nudat2/reCenter.jsp?z=90&n=142

Raw Material!

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Uranium vs Thorium as a Fuel

0.7 % of Uranium is fissionable. The rest becomes nuclear waste.

Thorium is isotopically pure and converted to U233 for fuel.

For fuel cycle side-reactions see- http://en.wikipedia.org/wiki/Thorium_fuel_cycle

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Fuel or WasteWe want the fuel to fission rather than transmute.

U233- 90% fissions

U235- 83% fissions

P239- 50% fissions

P241- 25% fissions

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Outline

Motivations for Nuclear Power LFTR overview Nuclear Chemistry Chemistry Myths Questions

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LFTR Processing Details

FluorideVolatility

VacuumDistillation

Uranium Absorption-Reduction

232,233,234UF6

7LiF-BeF2-UF4

233UF6

FissionProductWaste

HexafluorideDistillation

FluorideVolatility

7LiF-BeF2

“Bare” Salt

Pa-233Decay Tank

Metallic Thorium feed stream

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

Other F6

Fuel SaltxF6

Blanket

Two-Fluid Reactor

Bism

uth

-me

tal

Re

du

ctive

Extra

ction

Co

lum

n

Molybdenum and Iodine for Medical Uses

Fertile Salt

Recycle Fertile Salt

Recycle Fuel Salt

Pa

Return 2525

Core

Metal Reduction Column

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Outline

Motivations for Nuclear Power LFTR overview Nuclear Chemistry Chemistry Myths Questions

2727

Myth of Half Life

What makes a radioactive material dangerous?– Even low energy beta decays can break organic bonds.

Is a material with a 1 second half life dangerous?– It is very dangerous..today. Tomorrow it is inert.

Is a 15 billion year half life dangerous? (Half of it has decayed since the big bang.) It has a very low activity, and we used it for hundreds of years.

How about a thousand year half life? It is both active and persistent.

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Myth of Creating Radioactivity If radiation is dangerous then we should do

what we can to eliminate it from the environment. That is exactly what nuclear reactors do. They are the nuclear analog to chemical catalysis reactors; they accelerate natural processes.

The only way to “create” nuclear radiation is with particle accelerators. Conventional reactors simply accelerate decay towards stable elements.

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Myth of Concentration

Thorium and uranium are dispersed in nature and they decay naturally. We concentrate them, and so concentrate their natural toxicity.

For safe disposal, should we re-disperse them and lower their effective activity, or sequester them and decrease our contact?

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References

http://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reactor

http://www.scribd.com/doc/59204103/Thorium-presentation-Green-Energy-Forum-2008-07-25

http://www.thoriumenergyalliance.com/ThoriumSite/resources.html

http://moltensalt.org/references/static/downloads/pdf/NAT_MSBRrecycle.pdf

Thorium in 5 minutes (remix video) http://www.youtube.com/watch?v=uK367T7h6ZY

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Motivations for Nuclear Power LFTR overview Nuclear Chemistry Chemistry Myths Questions

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Binding energy

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