Post on 21-Dec-2015
transcript
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
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?
6
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
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