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Lithium Flouride
Thorium Reactors
MATT LAPPIN
Overview
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Lithium Fluoride Thorium Reactor (LFTR) – nuclear
reactor with a thorium fuel

Discussion of global energy needs

Explanation of nuclear reactor science and how
conventional nuclear reactors work

How the LFTR works and the improvements it has
on conventional nuclear reactors
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Does the world face an energy
crisis?
THE ANSWER IS PROBABLY YES
Energy Crisis
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Fossil fuel dependence
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We will run out

Potentially driving force in climate change

Pollution affects humans and wildlife
Need to limit our fossil fuel dependence
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Alternative Energy

There are many other sources of power available to us

Wind, water, solar, and nuclear to name a few

Difficult to harness effectively

Water power is only harvested in dams, these bring environmental
problems and are only available in certain areas

Wind power is geographically limited and takes up valuable land

Solar power has not become efficient enough to use on a large scale

What about nuclear power?
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Nuclear power is power generated
from the energy released when the
nucleus of an atom becomes so
large that the atom must split into
two smaller atoms
Atoms

The basic building blocks that make
up everyday things

Made up of protons, neutrons, and
electrons

Protons and neutrons are tightly
packed at the center of the atom in
the nucleus

Electrons “orbit” the nucleus

The nucleus and neutrons are
important for nuclear power

Classify atoms by their number of
protons and number of neutrons
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Atoms

The number of protons in an atom
determine which element an
atom is

Each element can have different
types of atoms, all with the same
number of protons, but a different
number of neutrons

Classify atoms by element and
weight

An atom of carbon-12 has 6
protons (carbon) and 6 neutrons
(12-6=6)
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Carbon-14 has 6 protons but 8
electrons
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Splitting Atoms

The more protons and neutrons
there are in an atom, the more
unstable it is.

The nucleus gets “crowded”

This leads to a property known as
radioactivity

Radioactive elements emit
particles and/or radiation in order
to reduce the number of protons
and neutrons

This is called radioactive decay
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Alpha decay – a plutonium-240 atom
ejects an alpha particle (2 protons and 2
neutrons) from its nucleus to become
uranium-236
Splitting Atoms

Some radioactive elements can
be forced to take on additional
neutrons

When this happens, the nucleus
becomes so crowded that it splits,
creating two atoms, some
neutrons, and a large amount of
energy

This is called fission

Main reaction used to generate
nuclear power
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Chain Reaction

Each of the new neutrons can hit
another over-crowded nucleus
and cause the release of three
more neutrons

This is how the atomic bomb was
able to release so much energy
when it detonated.

In a nuclear power plant this
would be really bad

Other materials are used to catch
some of these neutrons
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Nuclear Power Plants

At a power plant, the fission
reaction of uranium-235 proceeds
in a controlled fashion

The energy released by the
reactions is converted from heat
energy to electrical energy with a
water-steam-turbine system
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Drawbacks

Nuclear waste – products of fission
are often more radioactive, this is
harmful to humans
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Meltdowns – reaction rate and
temperature must be heavily
controlled or radioactive material
can escape
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Nuclear proliferation – enriched
uranium (ready to be used in a
reactor) is also used to make
bombs, and can get into the
wrong hands
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Mined uranium(-238) must be
enriched before it can be used as
fuel, adds cost
Note: More lives per unit of energy
produced have been lost to fossil fuel
and hydropower pollution and
accidents
Avoiding Nuclear Disaster

Mitigation of these drawbacks is
necessary for nuclear power to
become a successful source of
power

A potential solution was
discovered at Oak Ridge National
Lab in Tennesee in the 1960s

Called the “Molten Salt Reactor
Experiment”

Precursor to the Lithium Fluouride
Thorium Reactor (LFTR)
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LFTRs, How Do They Work?

LFTRs use the same type of reaction, fission, as a conventional
nuclear reactor does
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Breeder reactor – a reactor with a little bit of fuel ready to fission,
and mostly fuel that cannot undergo fission

In a breeder the initially fissionable fuel reacts to produce a neutron
that converts some of the non-fissionable fuel into fissionable fuel

Newly converted fuel can now undergo fission to release energy
and convert more material into fissionable fuel

Even with this extra step the reaction is self-sustaining and once
started will proceed naturally
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LFTR Breeder Reaction
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LFTR Breeder Design
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Fuel
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LFTRs use a small amount of
uranium-233 as an “ignition” fuel
Why this fuel is better:
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Thorium-232 comes straight out of
the Earth (no enrichment)
Naturally mined thorium-232 serves
as the rest of the fuel.
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Thorium-232 is 3 times as abundant
on Earth than uranium is
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The fission products of uranium-233
are less radioactive than that of
uranium-235 (83% shorter half life)
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Proliferation risk is reduced – most
of the fuel used in the LFTR is not
weapons grade nuclear material
Thorium-232 can be converted
into uranium-233 in the reactor
Reactor State
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LFTRs keep their fuel in a molten
state – this is the lithium fluoride part
Lithium fluoride is a salt with a high
melting temperature (845 degrees
C)
The thorium and small amount of
uranium are dissolved in the molten
salts, which serve to absorb the
heat from the nuclear reaction to
stay molten
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Why this state is preferable:
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No meltdown – the salt is highly capable of
absorbing the excess heat from the reaction
without a dramatic change in behavior
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Lower pressure – if a leak were to occur the
LFTR is a relatively low pressure reactor and
an explosion would not happen
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As the salt gets hotter the thorium reactions
automatically slow down, releasing less heat
and allowing the salt to cool down a bit
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In the event of runaway overheating, a plug
at the bottom of the reactor melts and
freezes the reaction an underground
chamber to be handled when safe
Reactor State
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The important design goal – passive safety
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Many aspects of this reactor are designed in such away that little
human intervention is required in the event of an emergency
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This minimizes risk and puts as few people as possible at health risk
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Computer simulation play a large role in the design efforts
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That technology was not available for the design of any of the
failed reactors that history has seen
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Energy Conversion
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The LFTR is a much more energy efficient reactor than the
conventional nuclear reactor
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The molten salts that are used to transfer the heat energy out of the
reactor have a much high heat transfer efficiency than water
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The specific heat exchange method used in a LFTR can use carbon
dioxide to drive the turbine instead of water and steam
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These two factors result in a 30% increase in efficiency over
conventional fission reactors
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Cost Efficiency
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These three factors not only result
in a safer and more energy
efficient reactor, but a cheaper
one as well
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The fuel is more abundant and
requires less pre-processing
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More efficient fuel means a
reduction in fuel costs
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Less safeguards are required due
to inherent safety in the system
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LFTR requires less special
machinery than conventional
fission reactor
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So why aren’t LFTRs everywhere?
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Technology hasn’t been seriously explored since shortly after its
discovery (until very recently)
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Public opinion of nuclear energy is skewed negatively by a lack of
information
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France, with a greater percentage of nuclear power than the US
and a cleaner nuclear track record, has a worse opinion of nuclear
energy than the US
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Developing a business model for LFTRs is difficult – conventional
reactor vendors sell fuel at a profit. LFTR fuel is so abundant and
requires little pre-processing anyone could mine it and sell it
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This means the reactor vendor’s business model cannot rely on just
selling fuel
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LFTRs could be on the way!
Groups all around the world are pursuing this technology
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FUJI MSR being developed to produce energy at a cost of about 3
cents/kWh
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Former NASA scientist and Chief Nuclear Engineer at Teledyne
Brown Engineering is attempting to win a military contract to
develop a LFTR that could power a military mbase
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Similar efforts being made in Australia and China
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Bill Gates spoke out in favor of these types of reactors in 2012 in a
WSJ interview
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New Energy is Necessary
Fossil fuels will only last so long!
LFTR technology, or something even safer
that could be discovered as a result of
building and studying LFTRs, needs to be
developed before fossil fuels are gone
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Thank You