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Lithium Flouride Thorium Reactors MATT LAPPIN 1

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1

Lithium Flouride Thorium ReactorsMATT LAPPIN

2Overview

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

4Energy Crisis

Fossil fuel dependence

We will run out

Potentially driving force in climate change

Pollution affects humans and wildlife

Need to limit our fossil fuel dependence

5Alternative 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

7Atoms

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

8Atoms

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)

Carbon-14 has 6 protons but 8 electrons

9Splitting 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 decayAlpha decay – a plutonium-240 atom ejects an alpha particle (2 protons and 2 neutrons) from its nucleus to become uranium-236

10Splitting 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

11Chain 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

12Nuclear 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

13Drawbacks

Nuclear waste – products of fission are often more radioactive, this is harmful to humans

Meltdowns – reaction rate and temperature must be heavily controlled or radioactive material can escape

Nuclear proliferation – enriched uranium (ready to be used in a reactor) is also used to make bombs, and can get into the wrong hands

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

14Avoiding 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)

15LFTRs, How Do They Work?

LFTRs use the same type of reaction, fission, as a conventional nuclear reactor does

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

16LFTR Breeder Reaction

17LFTR Breeder Design

18Fuel

LFTRs use a small amount of uranium-233 as an “ignition” fuel

Naturally mined thorium-232 serves as the rest of the fuel.

Thorium-232 can be converted into uranium-233 in the reactor

Why this fuel is better:

Thorium-232 comes straight out of the Earth (no enrichment)

Thorium-232 is 3 times as abundant on Earth than uranium is

The fission products of uranium-233 are less radioactive than that of uranium-235 (83% shorter half life)

Proliferation risk is reduced – most of the fuel used in the LFTR is not weapons grade nuclear material

19Reactor State 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

Why this state is preferable:

No meltdown – the salt is highly capable of absorbing the excess heat from the reaction without a dramatic change in behavior

Lower pressure – if a leak were to occur the LFTR is a relatively low pressure reactor and an explosion would not happen

As the salt gets hotter the thorium reactions automatically slow down, releasing less heat and allowing the salt to cool down a bit

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

20Reactor State

The important design goal – passive safety

Many aspects of this reactor are designed in such away that little human intervention is required in the event of an emergency

This minimizes risk and puts as few people as possible at health risk

Computer simulation play a large role in the design efforts

That technology was not available for the design of any of the failed reactors that history has seen

21Energy Conversion

The LFTR is a much more energy efficient reactor than the conventional nuclear reactor

The molten salts that are used to transfer the heat energy out of the reactor have a much high heat transfer efficiency than water

The specific heat exchange method used in a LFTR can use carbon dioxide to drive the turbine instead of water and steam

These two factors result in a 30% increase in efficiency over conventional fission reactors

22Cost Efficiency

These three factors not only result in a safer and more energy efficient reactor, but a cheaper one as well

The fuel is more abundant and requires less pre-processing

More efficient fuel means a reduction in fuel costs

Less safeguards are required due to inherent safety in the system

LFTR requires less special machinery than conventional fission reactor

23So why aren’t LFTRs everywhere?

Technology hasn’t been seriously explored since shortly after its discovery (until very recently)

Public opinion of nuclear energy is skewed negatively by a lack of information

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

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

This means the reactor vendor’s business model cannot rely on just selling fuel

24LFTRs could be on the way!

Groups all around the world are pursuing this technology

FUJI MSR being developed to produce energy at a cost of about 3 cents/kWh

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

Similar efforts being made in Australia and China

Bill Gates spoke out in favor of these types of reactors in 2012 in a WSJ interview

25New 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