The document discusses the potential benefits of molten salt reactors that use thorium as fuel instead of uranium. It summarizes that thorium is more abundant than uranium, produces less waste, and allows for greater safety and efficiency. Molten salt thorium reactors could provide clean, sustainable nuclear energy on a larger scale by addressing issues with current reactor designs like limited resources and waste disposal. The document examines how molten salt reactors worked in the past and how new designs address prior challenges through the use of liquid fuel and on-going processing of nuclear materials.

1. C6
6152
University of Pittsburgh, Swanson School of Engineering
2016/03/04
1
Disclaimer — This paper partially fulfills a writing requirement for first year (freshman) engineering students at the
University of Pittsburgh Swanson School of Engineering. This paper is a student, not a professional, paper. This paper is
based on publicly available information and may not be provide complete analyses of all relevant data. If this paper is used
for any purpose other than these authors’ partial fulfillment of a writing requirement for first year (freshman) engineering
students at the University of Pittsburgh Swanson School of Engineering, the userdoes so at his or her own risk.
THE USE OF MOLTEN SALTS AND THORIUM IN LIQUID SOLUTION IN
NUCLEAR REACTORS
Brendan Schuster, bjs111@pitt.edu, Mahboobin 4:00, Kristy Sturgess, kms302@pitt.edu, Mena, 4:00
Abstract— As of January 2016, nuclear power stations
provided over 11% of the world’s electricity with reliable
power and without carbon dioxide emissions. This number
will surely increase as society continues to use nuclear
power plants. There are several problems concerning the
sustainability of current nuclear reactors: they use uranium,
an extremely rare element, have safety issues, produce large
amounts of dangerous radioactive waste, and require large
amounts of money to run and to refine the uranium.
Constructing and implementing molten salt reactors that use
thorium can solve all of these problems, due to using liquid
fuel instead of solid fuel rods.
Current nuclear plants require electricity to cool the core
if there is a need for an emergency shutdown. This makes
nuclear plants especially vulnerable, especially when a
meltdown can be catastrophic. The molten salt reactors are
inherently safer because they shut down without human
intervention. Molten salt thorium reactors are also cheaper
to construct than current uranium reactors because of the
innate safety features using liquid fuels, like running at
atmospheric pressure and shutting down without human
intervention when power is lost. This innovation greatly
increases the amount of energy that can be harvested from
fission, and increase the efficiency of turning thermal energy
into electricity. Lastly, these reactors produce far less waste
than current uranium reactors, and this waste is harmful for
a much shorter time.
If implemented into the world today, society would have a
clean, sustainable energy that can efficiently reduce our
carbon emissions and provide the world with a clean and
sustainable energy.
Key words- Breeding, Ethical Concerns, Energy
Sustainability,Molten Salt Reactor, Thorium
THE NEED FOR CLEAN SUSTAINABLE
ENERGY
Fossil fuels are limited, non-renewable resources that the
world uses as a primary method to generate electricity. In
fact, 62.6% of energy production comes directly from coal
and natural gas [1]. However, 46% of carbon dioxide
emissions come from electricity and heat production [2].
This means almost half of the world’s energy production can
become carbon-neutral if the switch was made to nuclear
power. When carbon dioxide gas is released into the
atmosphere, it pollutes the air, creating detrimental outcomes
for our environment, such as accelerating the melting of our
glaciers, and speeding up climate change [1]. There is a
current drive to increase the amount of clean energy
production, which is energy production that does not create
carbon dioxide as a byproduct, or other unmanageable
byproducts. Burning fossil fuels is not a sustainable energy
source because of the harmful byproducts it creates, and
there is a dwindling supply of oil and gas left on the Earth.
According to the United States Environmental Protection
Agency, sustainability refers to the endurance of systems
and processes. It is based on the simple principle that we
need nature to coexist with humans because we get
everything from our natural environment [3]. Nuclear energy
can be a sustainable solution to our clean energy production
problems. Even if there were a huge supply of fossil fuels
left, the current system is not sustainable, because of the
pollution and damage to the environment. One must consider
fairness beyond generations when it comes to decisions
regarding ethical dilemmas such as the best method for
producing mass amounts of energy [3]. France has shown
that it is possible to run a country primarily on nuclear
power, providing 76.9% of their electricity from nuclear
energy, but their program is not completely sustainable right
now either [2]. There are a few problems presently faced in
the long term for current nuclear reactors, such as finding a
new nuclear fuel source besides uranium, increasing the
safety of nuclear reactors, and finding ways to dispose of
radioactive waste.
New Ideas for Nuclear Energy
Current global assessment models predict that in the
future, carbon-neutral energies will become extremely
important [4]. Carbon-neutral energy refers to energy
production without the emissions of carbon dioxide. One can
already see the shift starting to occur, because in the past
few decades, there has been a growing emphasis on “green”
technologies. Currently, nuclear energy is the only carbon

2. Brendan Schuster
Kristy Sturgess
2
neutral energy that can meet the increasing energy demands,
but it still has some problems. While solar and wind are
promising types of renewable energies, they are not
sustainable because they will not be able to power the
increasing demands of our world as developing countries
will need more power and as Earth’s population continues to
increase exponentially [5]. These problems include
increasing the safety in terms of reducing radiation leakage,
finding a new source of fuel, and reducing the production of
harmful radioactive nuclear waste. The answer lies in a new
generation of nuclear reactors, called molten salt thorium
reactors; these reactors can improve greatly on all aspects of
the issues presented. Thorium is a metal that can solve the
long term and short-term problems of current nuclear
reactors due to many factors including its abundance, waste
management, and safety concerns.
SUITABILITY OF THORIUM
Just like fossil fuels, the world is running out of uranium,
which means the current nuclear energy programs are not
sustainable. Thorium is three times more abundant in Earth’s
crust than uranium is, which means there is more of it and it
is easier to find. It has already been mined and accumulates
from rare earth metal mining in countries such as China,
Brazil, and India [2]. China and India, two of the most
populous places on Earth, do not have enough uranium to
fuel nuclear reactors. However, they have huge amounts of
thorium [5]. Thorium also has only one isotope that is usable
for fission; meaning 100% of the thorium mined from the
ground can be used for fission. Fission is the process of
splitting an atom in order to create energy. Uranium’s
primary isotope used for fission, U-235, comprises only
0.7% of the uranium found in the ground. There are also no
known large reserves of uranium left [1]. Using thorium
therefore is a much more sustainable model because there
are plenty of supplies of it compared to uranium, which will
soon become a dwindling element. Molten salt thorium
reactors will utilize thorium more effectively, efficiently,
and at a cheaper cost than current nuclear reactors [2].
If used in the molten salt reactor design, thorium
becomes a much more suitable fuel than uranium. Thorium
is immensely energy dense; you can hold a lifetime’s supply
of energy in the palm of your hand [6]. Compare this to a
solid uranium fuel rod, which has a reactor lifetime of about
3 years before it is deemed unusable [7]. The molten salt
reactor, which will be abbreviated MSR, can harvest almost
all of the energy that thorium gives off compared to the low
efficiencies of current uranium plants [1]. In the United
States alone, there is a 32,000 metric ton stockpile of
thorium buried in a shallow trench in Nevada. This could
produce almost as much energy as the United States uses in
three years [6]. Australia, Norway, and Canada all have
large reserves of thorium as well. Internationally, uranium
levels are too low to support the current nuclear programs
for years to come, meaning the current model is not
sustainable. Soon the old process will not be used, and
another form of energy will need to be found. Using the
MSR to produce energy will give nuclear energy a stable
and sustainable method to become a primary energy
producer.
Thorium Reactors in the Past
The idea of molten salt nuclear reactors has been around
since the 1950s. Oak Ridge Laboratory was the first in the
United States to begin researching the liquid fluoride salt
designs [5]. This design showed great inherent safety
because the reactor shut down without electricity, in fact the
scientists were able to shut the reactor down when they went
home for the weekend [6]. This shows that even sixty years
ago, these were much safer than traditional uranium water
reactors [6]. One of the problems with their design was the
fragile and delicate plumbing system. If there was a crack or
leak, the entire plumbing systemneeded to be replaced. This
was due to the complicated reactor design that the scientists
used. At Oak Ridge, the issues with the corrosion of the
pipes lead to the termination of the program even though the
problems were well on their way to being addressed. The
termination of the program ended the research of thorium
molten salt reactors for a long time. Since then, different
designs have shown that they can solve the problems the
engineers at Oak Ridge faced. After the program termination,
thorium molten salt reactors received almost no international
funding and improving these designs almost came to a
standstill [5].
During the time in which Oak Ridge was facing
difficulties, plutonium was useful for creating nuclear
weapons so uranium fission was highly valued for the
plutonium rich nuclear waste. Uranium water reactors were
chosen as the design to use because these reactors could be
used on submarines where a water coolant was abundant.
Plus, the production of plutonium was favored because the
United States was in an arms race during the Cold War and
plutonium was needed for nuclear warheads. Countries soon
developed their own nuclear programs based off the U.S.
and decided to use uranium for the same reasons. Now that
priorities have shifted, the nuclear waste from MSR reactors
has no ability to be made into a nuclear weapon [8]. The
plutonium rich waste from the uranium reactors is no longer
valuable because no one in the world is mass-producing
nuclear weapons that use plutonium. Since this isn’t
desirable anymore, there is no reason to use a nuclear reactor
that creates a radioactive product such as plutonium.
HOW IT WORKS
Current designs for the molten salt reactors fixed the
plumbing issue by implementing a two-fluid design,
meaning there are two ways for the liquid to enter and exit
the core. A one-fluid design meant that one crack in the
plumbing meant everything had to be replaced and the liquid

3. Brendan Schuster
Kristy Sturgess
3
fuel had to be removed while it was being fixed. The two
fluid design means that within the reactor, there is something
called a blanket and a core, and it is easier to replace certain
areas of the plumbing systems. The core (lightly shaded area
between vertical rods in the reactor in Figure 1) of nuclear
reactor contains fissile U-233, or spent uranium fuel, mixed
with fluoride salts in a liquid solution. Uranium bonds with
the fluoride creating liquid uranium tetra-fluoride (UF4).
The blanket solution (rods and plumbing channels in in
reactor in Figure 1) consists of thorium tetra-fluoride,
beryllium, and lithium. It is kept molten through the
radiating heat of the core. [7]. The fissile material is needed
to start the reaction because thorium is not naturally
radioactive. The thorium nucleus needs to be bombarded
with neutrons to start any sort of chain reaction [7]. When
the blanket solution is bombarded with neutrons from the
core, the thorium-232 (regular thorium isotope) enters beta
decay, meaning it loses an electron and a neutron is
transformed into a proton [7]. The resulting thorium-233
with an extra proton beta then decays into protactinium-233,
which decays again into 233U and bonds with the fluoride,
creating UF4, the original fissile material in the core.
FIGURE 1 [8]
MSR reactor core with thorium blanket in white rods
The molten salt blanket enters and exits the core, accepting
neutrons. Impurities are cleaned out before reintroducing
liquid to the core. Off to the right, pure liquid fluoride salts
pass heat to turbines,creating energy.
The resulting U-233 from the blanket solution must be
moved into the core; this is where the benefit of the liquid
solution comes in handy. By bubbling fluoride gas through
the blanket solution (Off gas systems), UF-4 turns into
gaseous uranium hexafluoride (UF-6), while not affecting
the rest of the thorium tetra-fluoride [7]. This means the
fission products either quickly form stable fluorides that will
stay within the salt, or become volatile and insoluble so they
can be continuously removed [5]. The gaseous uranium
hexafluoride is bubbled out and then reduced back down to
uranium tetra-fluoride (UF4). This fissile material will then
be added into the core solution to produce more heat and to
continue the reaction [7]. The liquid solutions require the use
of fluoride salts because the ionic bonds formed between the
metals and liquid fluorides withstand an extremely large
amount of heat and radiation before breaking down. The
liquid solution also allows harmful byproducts of the fission
process bubble out of the solution (chemical processing in
Figure 1). Whatever is not bubbled out of the liquid solution
will be kept and instead will fluorinate into the core solution.
This takes all of the uranium tetra-fluoride from the core and
converts it to UF-6 like in the blanket solution [7]. Then,
UF-6 reduces back to UF-4 before entering the core to
fission. This successfully removes impurities from the core
and fromthe blanket solution, which is impossible with solid
fuel uranium rods in use today. By doing this, the efficiency
of harvesting nuclear energy increases greatly. This
increases the life of the fuel and the sustainability of the
energy production. In typical uranium reactors there is no
way to remove impurities in the ceramic uranium rods, and
the reactor must shut down every few months to switch out
and rotate the solid fuel rods. With some MSR designs, you
can run a nuclear reaction for thirty years before stopping
anything. The processing will run simultaneously with the
reaction in the core [5]. Running a fission reaction for more
than thirty years straight is an extremely sustainable process.
Once the reaction begins, energy will be produced at
constant rate for thirty years, with no fuel additions to the
reactor.
Efficiency and Breeding
The extremely high temperature is also much better
suited for heat transfer [6]. The salts can reach extreme
temperatures without boiling since their boiling point is
incredibly high due to their ionic bonds. Boiling water
reactors use low power turbines to create energy with a
lower energy transfer. Primary salt that runs through the core
passes heat off to another liquid fluoride, which will directly
be used to turn a power turbine and create electrical energy.
In fact, these reactors can work at an efficiency of 50%
compared to regular nuclear plants or coal plants, which
have an efficiency of about 35% [7]. This produces a
sustainable energy that is more efficient in almost every
aspect to current uranium nuclear energy.
Another useful feature that the molten salt reactor has is
breeding. In nuclear terms, breeding refers to producing
more fissile material as the reactor core creates energy.
Breeding is extremely useful because the thorium, which is a
naturally stable isotope, is hit with a neutron, turning it
eventually into fissionable uranium. When all of the thorium
is used up in the blanket solution, the core still has

4. Brendan Schuster
Kristy Sturgess
4
fissionable material inside of it [9]. Figure 2 shows the
process of thorium decay. First thorium-232 accepts a
neutron, then it beta decays into protactinum-233. A beta
decay means the atomloses and electron, and a neutron turns
into a proton. After this it decays into U-233, releasing
neutrons to start the process again. This means that all of the
thorium in the blanket is used up and converted to fuel,
meaning the only needed material that needs added again is
thorium. Current reactors just require uranium rods to be
added, but this much more costly because uranium is
radioactive and needs to be transported and handled with
extra safety measures. Another benefit of this long chain
reaction is the amount of heat produced. Thorium breaks
down multiple times before it becomes U-233, releasing heat
and energy each time. The MSR is able to harvest all of this
energy by keeping this chain reaction enclosed within the
liquid fuel.
Figure 2 [10]
Fission process of MSR breeding
At the end of the process, the U-233 releases neutrons that
the thorium atom accepts, continuing the energy producing
process.
Thorium to Uranium Breeding Cycle
Thorium atoms are also much more likely to collide with
neutrons in the liquid solution because many impurities like
xenon are bubbled out of the solution, and xenon is
notoriously known for reducing the neutron economy in
current uranium solid fuel reactors [7]. Neutron economy
refers to the suitability of the surroundings for thorium
atoms and molecules to accept a neutron. The greater the
neutron economy, the more likely thorium will convert into
protactinium, then soon after, uranium [7]. The liquid
solution provides a much better neutron economy compared
to normal uranium rods, which become more impure with
time.
MSR reactors were able to reach breeding when they
were researched at Oak Ridge. Since then, scientists have
been able to get the breeding coefficient up to 1.13 [9]. This
means that 113% of the uranium or fissile material to start
up the reactor core was present after all the thorium is spent.
In terms of sustainability, MSR reactors can achieve a
continuous reaction for energy production just by adding
thorium. This is incredibly efficient because thorium would
be the only metal that needs to be added into a blanket
solution to continue the fission process. This is an important
aspect not only because of efficiency, but also because
transportation of radioactive materials can pose a risk to the
public. The only radioactive material that needs to be
brought to the plant would be the initial fissile startup
material. Using unrefined uranium or transuranic wastes,
such as plutonium, as the startup material will lower the
initial breeding ratio and neutron economy, but it is still
possible to keep the ratio above one. If the breeding ratio
drops below one, this means that there is less radioactive
material in the core than during the startup. If transuranic
wastes are used to add to the core, this will not be a problem
because using up these wastes is beneficial. Keeping the
transuranic wastes in the core can slightly decrease the
neutron economy, but one must consider sacrificing slight
efficiency because these materials that were once considered
wastes are used as fuel for more fission.
The breeding economy remains the best when graphite is
used as the moderator. A moderator works by slowing down
the neutrons blasted from the core atoms, because the
neutrons are moving too fast to collide and stick with
another atom’s nucleus [7]. When the neutron is slowed
down, the thorium has a higher chance of accepting the
neutron to start the fission chain reaction. Graphite also
allows for the core to run on low enriched uranium or
transuranic wastes. To further improve breeding coefficients,
protactinium can be removed from the blanket solution and
it can break down into uranium in a separate area, because it
has a half-life of 17 days (the protactinium will break down
into U233 and re-enter into the core) [5]. By removing these
atoms from the blanket, the neutron economy increases and
the chance that only a thorium atom will transform into
protactinium, and later uranium.
One disadvantage to the higher breeding ratios and
increased neutron economy is the damage inflicted to the
structural materials that hold the core and blanket salts.
When the graphite moderator slows down a neutron, it is
colliding with a neutron and then it bounces back off. MSR
reactors can run at a higher temperature and power
production level, but this means that the graphite lifespan
can greatly decrease. Estimations indicate that the graphite
can last from 2.7 to 30 years, depending on the power
production output [9]. Graphite is a very cheap and abundant
material, so replacing it will not be very expensive, but a
truly sustainable plant would not require such frequent
replacements of the moderator. The lifespan of the graphite
moderator and the plumbing is one of the biggest problems
engineers have yet to solve. Currently, American researchers
and the China Academy of Sciences are working with using

5. Brendan Schuster
Kristy Sturgess
5
molten salts as a coolant versus as a fuel component in order
to gain experience in dealing with these liquids. This
research will help improve the sustainability of the plumbing
and moderators of the MSR by making them more durable
and able to withstand more radiation and corrosion from the
molten salts. However, breeding is an extremely efficient
means of fission that current uranium reactors cannot come
close to achieving and this makes energy production with the
MSR an invaluable form of energy production [7].
WHY WE SHOULD SWITCH FROM
URANIUM
These MSR reactors have been selected as one of the
generation IV designs, meaning they highlight efficiency (in
terms of cost and energy), and safety, and are proliferation
resistant [1]. Proliferation resistance is the utilization and
deployment of a nuclear power plant without significantly
increasing the abundance of nuclear weapons, and it will be
discussed later in the paper [7]. Currently, nuclear energy is
not recognized as an effective countermeasure to global
warming because of the concerns it produces with nuclear
proliferation, safety, and radioactive waste [5]. According to
a global assessment model, nuclear fission energy may not
produce much of the world’s energy if these issues are not
adequately addressed [2]. Generation IV plants are not
expected to deploy until at least 2030 because they are still
under development [11]. The selection as a Gen IV reactor
means that this design shows great potential for long-term
use because it shows great sustainability. Even after a long
time has passed, the MSR plant shows high probability that
the technology and process of the reaction will endure
through time and still be used. The MSR reactor innovation
has been called an evolutionary, rather than revolutionary
innovation because there are multiple designs that can be
implemented to fit the specific energy needs of the areas
they are built [2].
Certain designs of MSR reactors are incredibly efficient
and sustainable. One design has been called the “30 year
design” because it can keep a high energy conversion ratio
without any fuel processing beyond chemistry control
(purifying the salts) while still maintaining a high breeding
ratio and great utilization of the uranium after it has been
converted from thorium [5]. The lower power density in the
core increase the lifetime of the graphite to 30 years and
allows for continuous running until all the thorium is spent.
This is a great accomplishment because current uranium
reactors are incapable of breeding because the fission of
uranium does not create viable products for continuation of
fission in the same reactor, and there is no way to purify the
fuel [7]. Furthermore, current reactors must shut down to
rotate uranium rods, which is costly for the plant and
inefficient because the uranium rods are still going through
fission, meaning energy is wasted.
More Reasons to Make the Switch
The efficiency of current uranium reactors is dismal. Fuel
rods need to be cycled through the core and some current
uranium plants need to shut down every 18 months to cycle
out uranium fuel rods [7]. The solid fuel rods make it
impossible to remove impurities, such as xenon, which
undermines the efficiency of the fuel because it can accept a
huge number of neutrons without breaking down into
smaller atoms. Having atoms to accept large numbers of
neutrons reduces the chance your target element will also
accept a neutron. Since it appears in solid fuel rods, there is
no way to remove it and the neutron economy drops far
below the efficiency of the MSR design [7].
While xenon quickly decays, it can set the fission chain
reaction off balance which if not managed carefully by
taking the rods out and rotating them in cycles in the core,
can cause an unstable core and an explosion like the
Chernobyl disaster. At the Chernobyl reactor, a temporary
chemical imbalance in a fuel rod caused it to overheat,
resulting in a meltdown that leaves the surrounding area
uninhabitable to this day [1]. After this accident, ethical
issues of safety were fully realized.
Being able to purify your blanket solution while running
a simultaneous fission reaction is extremely safe and
efficient. This process is far more advanced than the current
system, and the supply of fuel is far greater than any other
known fuel source for nuclear plants [7].
Cost Efficiency
If this innovation is going to acquire funding, the cost
efficiency of energy production has to be reasonable, else no
one would invest in this technology. With higher efficiency
in terms of using all of the energy that the thorium fuel
contains, molten salt reactors are more efficient than
uranium reactors. Because of the higher temperatures that
exist in the core and blanket salts, the thermal to electrical
energy efficiency of the MSR is much higher than current
coal and uranium plants [7]. The cost right now is high
because the experience curve is very small and one must
consider that there has been almost no funding for this
innovation internationally, so the learning curve is still high
[12].
A cost analysis conducted in Canada estimated that
running a thorium plant is more financially attractive than
uranium plants due to the higher burn up of thorium fuel
[12]. The thorium plant is estimated to produce $72/MWhr
compared to $74/MWhr for current uranium plants. The
construction of these plants is also cheaper because they do
not need the huge pressure dome that encloses water reactors
because MSRs run at normal atmospheric pressure. It saves
a vast amount of money during construction when you do
not need a 19-centimeter thick steel dome to contain the
pressure in the event of the water boiling [6]. Some may also
argue that the fluoride salts are expensive to use, but they are

6. Brendan Schuster
Kristy Sturgess
6
currently used in the current uranium enrichment process for
uranium, which is the type of fuel that all of the current
uranium reactors use [7].
The mining of thorium is also cheaper because there is
only one isotope; there are stockpiles of dormant fuel lying
dormant and ready to use. The cost of holding transuranic
waste is also high and most plants now store it on site. There
is 10,000 times less waste produced from the MSR than
current reactors and it is not nearly as volatile [5]. This
innovation is exponentially more efficient if these plants are
estimated to be cheaper to build and run, even when a
definite design has not been chosen.
Bringing in fuel and storing fuel becomes much cheaper
also. There is a huge reduction in the amount of waste
produced and fuel transportation will not require extra safety
measures, resulting in cheaper production of energy in the
long term [8].
In terms of cost, these reactors are far more sustainable
than current reactors. They are cheaper to build because of
the inherent safety of the design, saving huge amounts of
materials on safety measures. They are also cheaper to run
because the fuel source is a non-radioactive metal and initial
startup material. If breeding is achieved, the running cost
will also drop because of the efficiency of the decomposition
on the thorium into radioactive core fuel, meaning only
small amounts of thorium will be needed to continue the
fission process. Electrical energy transfer will also decrease
the cost of delivering energy to homes and businesses
because these reactors are small and safe enough to be built
near cities and places that have large energy needs. Being
able to strategically place these reactors in optimal places
allows for shorter wiring to its destination, meaning less
energy is lost in this transfer. Storing the waste will also be
cheaper and a more sustainable system because the MSR
produces far less radioactive waste and it only needs proper
storage for a few hundred years compared to a few hundred
thousand years with uranium radioactive waste. All of this
translates into a more sustainable process that is cheaper
than current uranium and coal plants already. In fifty years
after there is some experience with MSR reactors, the cost is
expected to be even lower [12].
ETHICAL CONCERNS
As demonstrated, it is evident that molten salt reactors are
superior in efficiency and limiting waste production. One
must also consider the aspect of proliferation resistance now
because as more countries develop nuclear energy and
technology, they will also gain the knowledge of how to
create nuclear weapons. Thorium reactors were not chosen
for further research because during this time they were
starting research, there was an emphasis on plutonium
production [5].
The United States was the first country to create nuclear
weapons and more plutonium was a good thing. This was
one of the reasons the government decided to fund uranium
plants instead. Water-cooled reactors also seemed ideal
because there is no shortage of coolant, and water-cooled
reactors would work perfectly on submarines for this reason
[5]. Priorities since then have greatly shifted because the
world is not in a nuclear arms race and limiting the
production of nuclear weapons is the ethical thing to do. As
stated above, using thorium as the primary element in
nuclear reactors will reduce the amount of nuclear weapons
being created and it will diminish the tension on nuclear
warfare.
Proliferation Resistance and Waste Disposal
Thorium does not produce plutonium when it undergoes
fission, and this is the primary element that is used in
nuclear weapons. Current reactor sites and disposal sites are
becoming plutonium mines [5]. If every developing country
starts a nuclear program with uranium reactors, they will
have material to easily make nuclear weapons. If thorium
energy is deployed in developing countries, they will have
clean energy without the means to produce nuclear warheads.
Nuclear energy may not be the best option in the future if
there are other carbon-neutral energies because of the
production of plutonium and lack of means for waste
disposal if thorium energy is not implemented. One
remarkable aspect of MSR designs is that they can actually
utilize plutonium, or spent transuranic waste, as a startup
fissile material in their cores [9]. Using up dangerous
materials instead of producing them shows that nuclear
energy can finally minimize waste production and while
maximizing energy production.
In the United States, nuclear waste disposal is a huge
concern because there are no sites where plants can legally
dump their wastes [11]. It is extremely dangerous to store
nuclear wastes on site of the reactors, but many nuclear sites
have begun to do this because there is nowhere else to put it
[1]. This is not sustainable in the long term because the
transuranic wastes radiate dangerously even after the plants
will close. It is ridiculous to think that a current nuclear
reactor will be running in 10,000 years, but the dangerous
wastes will still be producing harmful radiation. This means
that someone will eventually have to deal with these wastes
somehow instead of ignoring the problem.
There have been projects such as Yucca Mountain to
store this nuclear waste. However, after construction was
already started, the government shut it down and left nuclear
facilities with nowhere to place their radioactive waste. Now
there are only temporary storing facilities [6]. The dangerous
wastes also make current reactors a place where someone
can get their hands on plutonium, which can then be used to
create nuclear weapons. The MSR plants would not have to
worry about where they will need to send their waste and the
storage facilities will be no such targets for acquiring
dangerous radioactive material, such as plutonium because
they do not produce useable radioactive products [7]. These
plants can also use up transuranic wastes in the core, so

7. Brendan Schuster
Kristy Sturgess
7
instead of adding to current waste stockpiles, the MSR will
slowly chip away at the waste. The waste that is produced
from the MSR can be smaller than what is put in because of
the breeding ratio, leading to a truly sustainable energy
production model.
Referring back to the definition of sustainability in the
beginning of the paper, one sees that nature and humans
must coexist in order for this innovation to succeed [3].
Proliferation resistance exists to protect humans from
themselves. By limiting the production of plutonium the
availability of resources for creating nuclear weapons also
diminishes. If other countries develop nuclear programs that
produce plutonium, there is a small chance that they will not
create nuclear weapons and even a smaller chance that they
will disarm them voluntarily. By implementing this
innovation internationally, other countries can develop clean
and sustainable energy programs without risking nuclear
arms races.
Lastly, the waste produced from these plants is far less
dangerous as time goes on than current transuranic wastes
[5]. This is because the MSR can remove impurities fromthe
liquid fuel as the reaction continues unlike the solid uranium
rods, and reintroduce any radioactive materials until they
absorb a neutron and undergo a fission reaction [2].
Furthermore, any heavier atoms created can be kept in the
core until they fission. Solid uranium rods become polluted
with heavier actinides such as plutonium, americium, and
curium that leave it dangerously radioactive for extremely
100,000 years [7].
Safety Issues
Thorium molten salt reactors are superior to current
plants as well in terms of safety. Unlike current reactors,
these plants can shut down without electricity, and even
human intervention. The salts are kept running through the
reactor while a salt plug is kept frozen by blowing cool gas
over it (refer to Figure 1). If the power goes out, cool gas
stops blowing on the frozen plug, the heated liquid salts
from the reactor melt it, and the liquids drain through a pipe
into a drain tank [6]. The liquid fuel salts do not overheat
and boil like the water does in current reactors, so once in
the drain tank, the fuel will cool down on its own. Current
uranium plants require electricity to keep water pumping
through the core to avoid overheating the fuel rods [1]. Since
there is no need for a huge steel dome, these reactors can be
built in a more compact area and there is almost no threat of
a meltdown because of how easy it is to shut down the
reactor [5]. This incredible safety allows these plants to be
built in high-energy consuming areas and around cities due
to almost no threat of a meltdown. Close proximity to cities
improves on the efficiency and sustainability because the
excess heat produced in the core can be used to heat water
for the public’s use, and there is less electrical energy lost
with running power cables long distances [7].
With the idea of feasible nuclear breeding, transportation
of volatile nuclear fuel into the plant will not be needed
because thorium is not naturally radioactive. Less waste is
also produced because almost 100% burn up of thorium into
other elements, meaning that transporting waste away from
the reactor will occur less, making this energy production
safer for the public.
MOVING FORWARD WITH THORIUM
It has been proven extremely difficult to restart the clock
on nuclear energy [7]. The entire world is already so deeply
integrated with uranium energy it would be incredibly costly
to construct upwards of a thousand molten salt reactors
around the world for a full-on start up. Only in the past
twenty or so years have the concerns of nuclear waste
disposal and carbon neutral energy come into play [7]. One
must also keep in mind that there has been almost no
funding for this type of reactor since the Oak Ridge plant
was shut down [5]. The push for increased safety only
occurred after the accident at Fukushima [13]. When an
earthquake caused the power to go out at water-cooled
uranium reactor, there was no way to cool the uranium rods
or to pump the water through the core. The water turned into
steam, causing immense pressure in the reactor. An
explosion occurred that spewed radiation from the core for 6
days. This accident showed that nuclear reactors should be
prone to extreme situations such as natural disasters. When
one accident can lead to such damage, you have to be careful
not to place nuclear reactors so close to cities because over
100,000 people had to be evacuated from the surrounding
area [13]. There is definitely a possibility of this happening
again in the future, which is why this issue of safety needs to
be addressed.
Nuclear Energy’s Bright Future
It is not surprising to see that other countries around the
world have realized the potential that thorium nuclear energy
has. China is currently looking into implementing thorium
reactors along with India [11]. The reactor design China is
using will offer enhanced safety and proficient economics
compared to current nuclear reactors [11]. India is
implementing a more aggressive plan for thorium energy
with several breeder reactor designs being built. Both of the
plans that India and China have are to construct solid fuel
reactors instead of liquid fuel, mainly because the molten
salt reactor innovation is still in research and development.
The China Academy of Sciences has made progress on
researching the MSR design and they hope to obtain full
intellectual property rights to this innovation. They are
currently building a 5 MW reactor prototype that will
hopefully be running by the year 2020 [11]. The United
States and China are collaborating by researching liquid salt
cooled reactors right now in hopes to gain experience using
liquid salts as a cooling systembefore fully employing liquid
salt as a source of fuel. This research also aims to increase

8. Brendan Schuster
Kristy Sturgess
8
the sustainability of the graphite moderator and plumbing
systems, which will increase the safety and lifespan of
moderators for MSR reactors [11].
Why This Should Matter
If our society wants truly safe, clean energy then thorium
is our best choice. This advancement can produce huge
amounts of energy with a fraction of the waste that current
uranium reactors are generating. With no risk of meltdowns,
the molten salt reactor can produce the safest, and cleanest
energy possible at a cheaper price than current coal plants or
current nuclear reactors. As energy demands increase
internationally and fossil fuel supplies decrease more rapidly,
the need for engineers to find a sustainable and efficient new
source of energy becomes more imperative. If this design
receives funding, the world could use this innovation in 30
to 50 years on the industrial level [5]. Industrial
implementation of the MSR can create a sustainable energy
production model, because this reactor design can meet
increasing energy demands while providing a safe and
carbon-neutral waste that needs to be stored for a fraction of
the time of current nuclear waste. Using this innovation will
allow humans to coexist with nature without inflicting
damage to the environment with a sustainable form of
energy. The MSR innovation offers the best solution to
make a fast, environmentally conscious, and cost effective
conversion from fossil fuels, paired with the great
nonproliferation that would make it reasonable to employ
this technology in the developing world also where fossil
fuel consumption is an exigent problem [7].
REFERENCES
[1] (2016). “Nuclear Power in the World Today.” Nuclear
Engineering International. http://www.world-
nuclear.org/info/current-and-future-generation/nuclear-
power-in-the-world-today/
[2] T. Kamei, S. Hakami. (2010). “Evaluation of
implementation of thorium fuel cycle with LWR and MSR.”
Progress in Nuclear Energy. (Online Article).
DOI:10.1016/j.pnucene.2011.05.032. p. 1-6.
[3] (2016). United States Environmental Protection Agency
(Online Article). https://www.epa.gov/sustainability/learn -
about-sustainability#what
[4] A. Turnball, D., Glaser, Goldston R.J. (2015).
“Investigating the value of fusion energy using the Global
Change Assessment Model.” Energy Economics, Volume 51
(Online Article). pp 346-352.
http://www.sciencedirect.com/science/article/pii/S01409883
15002224
[5] D. Leblanc. (2009). “Molten salt reactors: New
beginning for an old idea.” Nuclear Engineering and
Design. (Online Article). DOI:
10.1016/j.nucengdes.2009.12.033. p. 1-13.
[6] K. Sorenson. (2011). “Thorium, an alternative nuclear
fuel.”
https://www.ted.com/talks/kirk_sorensen_thorium_an_altern
ative_nuclear_fuel (Video).
[7] R. Hargraves and R. Moir. (July 2010). “Liquid fluoride
thorium reactors: an old idea in nuclear power gets
reexamined.” American Scientist. [Online]. Available:
http://go.galegroup.com/ps/i.do?id=GALE%7CA257224415
&v=2.1&u=upitt_main&it=r&p=AONE&sw=w.
[8] C. Forsberg. "Overview of Nuclear Salt
Applications." Money.
http://csmb.ornl.gov/~webworks/cppr/y2001/pres/124276.pd
f
[9] C. Zou, X. Cha, (2014). “Optimization of temperature
coefficient breeding ratio for a graphite-moderated molten
salt reactor.” Nuclear Engineering and Design. (Online
Article). DOI: 10.1016/j.nucengdes.2014.11.022. p. 1-7.
[10] “MSR Technology Primer.” Egeneration.
http://www.egeneration.org/msr-technology-primer/
[11] (2015). “Thorium.” Nuclear Engineering International
http://www.world-nuclear.org/info/current-and-future-
generation/thorium/
[12] B. Graves, A. Wong, K. Mousavi, C. Canter, A. Kumar.
(2015). “Techno-economic assessment of thorium power in
Canada.” Annals of Nuclear Energy. (Online Article.) p.1-5.
DOI: 10.1016/j.anucene.2015.05.028
[13] (2015). “Fukushima Accident.” Nuclear Engineering
International. http://www.world-nuclear.org/info/safety-and-
security/safety-of-plants/fukushima-accident/
ACKNOWLEDGEMENTS
We would like to thank Allison Bundy, our co-chair, for
bringing clarity and brevity to our proposal. We would also
like to thank Janine Carlock for her helpful input and helpful
tips.