1. Feasibility of Electricity Generation
Using Thorium Based Nuclear Power-a
Possible Solution to Global Warming?
Alvia Gaskill, Jr.
Environmental Reference Materials, Inc.
PO Box 12527 Research Triangle Park, NC 27709
September 6, 2014

2. Feasibility of Electricity Generation
Using Thorium Based Nuclear Power-a
Possible Solution to Global Warming?
This report was prepared using information gathered from Internet
searches and from the knowledge of the author who has been involved in
research associated with energy and engineering solutions to global warming
for the last 15 years. He also authored a report on high level nuclear waste
disposal options while in graduate school (1977) as well as studied thermal
pollution from nuclear power plants while a summer student at the NC
Governor’s School in 1970 and authored a report while in college in 1974
entitled “Nuclear Power, 4th
Down and 100 Yards to Go.” The report is
presented in the form of general questions that would likely be asked if such
an analysis were to be performed for a customer.
What are the approaches being taken to solve the problem of
global warming?
The changes in climate (droughts, higher air temperatures, more
severe storms) and melting of ice sheets brought about by global warming
due to human produced greenhouse gas emissions have resulted in a three-
pronged approach to solve the problem: adaptation, geoengineering and
mitigation.
Adaptation to the changes to the climate such as building sea walls
around major cities to hold back sea level rise is being considered, but is not
a solution and can only limit some of the damage.
Geoengineering, the deliberate modification of the energy balance of
the atmosphere by removing carbon dioxide from ambient air or blocking
sunlight has many challenges and is only seen as a means to buy time until
so-called sustainable energy solutions are achieved. Critics also claim that if
successful, geoengineering could actually slow the development of
sustainable energy by reducing the incentive to make the necessary changes,
i.e., the moral hazard.
1

3. Mitigation, the reduction or elimination in emissions of greenhouse
gases, primarily carbon dioxide is viewed as the ultimate goal by
policymakers. However, to return the energy balance to that of the pre-
industrial period (before 1700) to achieve greenhouse gas levels in the
atmosphere that will not result in long-term ice sheet disintegration will also
require the removal of the excess carbon dioxide from the atmosphere as
well as other gases or the equivalent amount of carbon dioxide to equal all of
them. The so-called safe level for greenhouse gases in the atmosphere may
have already been exceeded and will likely be anyway in the next several
decades, regardless of mitigation efforts.
What are the options for mitigation that result in reduced or
no new greenhouse gas emissions?
In an ideal future, all energy for generation of electricity, for
transportation and for operation of factories and heating of buildings would
come from sunlight or wind power which for the most part result in few
greenhouse gas emissions. Because both are produced by energy from
sunlight, unlike fossil or nuclear fuel, their supply will never be exhausted
and at least in theory much of the power could be obtained through
distributed systems, e.g. rooftop solar panels.
While production of solar energy and operation of equipment using it
still produces waste heat, this is not considered a significant problem for the
21st
century although it may be one further down the road. Neither solar or
wind generated electricity at present is either economical or efficient enough
to meet the current or future needs by themselves and until storage
technologies are available neither can supply base-load demand since both
are produced intermittently.
Reduction in emissions from existing technologies in part through
increases in efficiency or where possible substituting natural gas for coal or
adding solar or wind are the focus of most research and policymaking.
Some improvements in efficiency with associated reduced emissions have
already been achieved in transportation through use of hybrid engines and
reduced body weight of automobiles. As an example, annual gasoline
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4. consumption in the U.S. peaked around 2007 (142 billion gallons) and hasn’t
exceeded that level (135 billion gallons in 2013) even as the number of
vehicles on the road has increased and the number of miles driven. At least
some of this can be attributed to more-efficient vehicles.
In the power generation sector, the switching from coal to natural gas
is also expected to result in lower emissions in the U.S. but not globally due
to the lack of natural gas supplies in growing major electricity users like
China and India that still depend upon coal or imported oil. Production of
natural gas is a leaky process and there is some controversy over whether the
net emissions reduction over the life cycle of natural gas vs. coal is actually
as great as advertised. Proposed EPA regulations on power generation
emissions do not address life cycle concerns.
The way forward, accepted by most governments and international
bodies (e.g. the Intergovernmental Panel on Climate Change-IPCC) is that of
a portfolio of technologies that includes fossil fuels, renewable energy from
wind and solar, hydroelectricity, bio-fuels and nuclear power.
How does nuclear power figure in the portfolio of future
options?
Nuclear plants provide about 19% of U.S. electricity base-load
demand in 2014. This varies considerably from state to state. North
Carolina gets 34% of its electricity from three nuclear power plants operated
by Duke Energy, the second highest in the country, but also gets 50% from
coal. This contrasts with France that receives 75% of its electricity from 59
reactors and exports some of the power generated to neighboring countries.
Why nuclear is not higher nationally, especially considering the need to
reduce greenhouse gas emissions from fossil fuels is discussed here.
Although this report only addresses the U.S. nuclear power industry, as the
largest producer of nuclear energy in the world, the U.S. experience is
instructive.
In 2014 there are 62 nuclear plants generating electricity in the U.S.
from 100 reactors, about 25% of the 435 reactors in the world. The number
of U.S. reactors has remained relatively constant for more than 30 years.
There are several reasons for this. The first is the high cost of reactor
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5. construction. The industry has been beset for decades by cost overruns that
were in part due to regulatory requirements added after high profile
accidents (Three Mile Island-1979, Chernobyl-1986, Fukushima-2011), but
even before Three Mile Island, costs were out of control.
Other factors that have limited the growth of nuclear include concerns
about the potential for use of power plants to produce nuclear weapons grade
plutonium (India, Pakistan, N. Korea, Iran), i.e. proliferation, the inability to
deal with spent fuel waste, and most recently, competition from natural gas.
As a result, the nuclear industry has become a static player in the search for
global warming solutions. This isn’t likely to change in the next few
decades as explained below in a look back at the U.S. nuclear power
industry.
To say that the U.S. nuclear plant construction business has been bad
is a massive understatement. Of the 62 plants currently in operation, all of
them began construction by 1974 and all of their reactors by 1977 until
recently when five new reactors were approved for construction at existing
plants in Georgia, South Carolina and Tennessee. Some of the reactors that
were under construction were finally completed in the 1980’s, but only after
long delays and massive cost overruns.
Even before Three Mile Island, cost overruns were impacting the
nuclear power industry, averaging more than 200 percent for the 75 nuclear
power reactors built from 1966 to 1977. Due to the accident at Three Mile
Island in 1979, new safety requirements were imposed and the economics of
electricity generation by nuclear became even more unfavorable.
As a result, more than 120 orders for reactors were canceled including
many under construction, bankrupting the utilities that owned them:
Washington Public Power Supply System, Public Service of New
Hampshire, Long Island Lighting, Consumers Power in Michigan and
Louisiana Power and Light to name but a few. The author owned distressed
bonds and preferred stock of several of these companies in the 1980’s and
actually made money on them.
Of the approximately 250 reactors ordered from 1953 to 2008, half of
these projects were canceled, 11 percent shut down before their licenses
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6. expired and 14% experienced a year or more outage. Half of the completed
reactors still in service are more than 30 years old.
However, the measure of how much of the potential power from
plants is being generated by operating reactors has increased from less than
60% in the 1970’s and 1980’s to more than 90% since 2001. This has made
up for the closing of eight reactors since 1991. Although there have been
major problems with the completion of reactors, after improvements in
safety were made and operating experience was obtained, the existing plants
have proven to be safe and reliable with some exceptions.
After decades of zero growth, the so-called nuclear renaissance began
in the 2000’s spawned in part by a federal program to encourage nuclear
power plant construction and the perception nuclear could help solve the
greenhouse gas emissions problem for the U.S. This led utilities to once
again submit applications for construction of new plants and reactors, but
because of natural gas, lowered projections for electricity demand and
Fukushima, most of these projects were also canceled.
Of the remaining projects, construction of the Georgia and South
Carolina reactors owned by Southern Company and SCANA began in 2013
and resumed after a 25-year delay in Tennessee at a TVA plant. They are
scheduled to come on line by 2017-2020, but in spite of federal loan
guarantees, construction delays may push these dates back even further. The
TVA reactor project is currently over budget and behind schedule.
When the loans were announced in 2010 as part of its Nuclear Power
2010 Program that was supposed to coordinate efforts for building new
nuclear power plants, the Administration seemed upbeat about the future of
the nuclear industry:
The reactors are "just the first of what we hope will be many new
nuclear projects," said Carol Browner, director of the White House Office of
Energy and Climate Change Policy. The former Clinton EPA Administrator
and Gore confidant doesn’t work there anymore and it isn’t clear how much
coordinating is still going on.
The failure of Congress and various administrations to reach
agreement on how to dispose of spent fuel also continues to hamper future
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7. growth of the industry. At present in the U.S., some 65,000 tons of spent
fuel rods are stored on site at existing plants, creating the potential for a
disastrous release of radiation if the power to operate cooling pumps were to
be lost for an extended period of time due to either a hurricane, earthquake
or electromagnetic pulse from a solar flare.
Nine states also prohibit building any new nuclear reactors until a
storage solution is found. While there is an international consensus that this
spent fuel should be stored deep underground in caves or salt mines no
country has opened such a facility. An August 2012 ruling by the U.S.
Court of Appeals for D.C. let stand a lower court ruling that no new nuclear
plants can be licensed in the U.S. until a waste fuel repository can be
created.
However, there does not appear to be a shortage of uranium to operate
existing plants or to fuel new ones. The U.S. has the fourth largest reserves
in the world at 300 million pounds and imports 87% of that used from
Canada, Russia and Australia. This is enough to fuel existing reactors for
more than a thousand years.
Since only about half of the uranium is used in a typical 17-month
cycle in a U.S. reactor, reprocessing of the spent fuel could extend supplies
even further. However, the current administration, along with others before
it has banned reprocessing of spent fuel over concerns the Plutonium could
be stolen and used to make nuclear weapons (unlikely because it is not
weapons grade) or use it in a dirty bomb.
Other reasons are that there is no agreed upon repository for the high
level actinide waste generated and because of the much higher cost of
reprocessing compared to the once-through fuel cycle presently used.
Reprocessing is also a dangerous operation as it potentially exposes workers
to very high levels of radiation.
The low price and increasing supply of natural gas along with
proposed federal regulations has also made it the go to option for new power
plants instead of coal or nuclear resulting in some negative forecasts for
nuclear in the near term.
6

8. According to the U.S. DOE “Experts see continuing challenges that
will make it very difficult for the nuclear power industry to expand beyond a
small handful of reactor projects that government agencies decide to
subsidize by forcing taxpayers to assume the risk for the reactors and
mandating that ratepayers pay for construction in advance.”
An equally pessimistic assessment was issued by Excelon Energy in
August 2012, at the time the nation’s largest utility, and operator of 17
nuclear reactors, stating that “Economic and market conditions, especially
low natural gas prices, made the construction of new merchant nuclear
power plants in competitive markets uneconomical now and for the
foreseeable future.”
Because of all these factors, instead of planning new reactor or plant
projects, utilities are seeking license extensions for existing reactors and
closing old ones due to high maintenance and repair costs. The net effect of
the new reactors from Southern Company, SCANA and the TVA and the
retirements of older ones are expected to increase generating capacity by
around 5500 MW, not enough to move the dial on greenhouse gas
emissions.
In spite of these challenges, nuclear may be poised to make yet
another comeback through use of a different kind of reactor, one fueled by
the naturally occurring element Thorium instead of Uranium or Plutonium.
Advocates argue that it will result in safer and cheaper plants than those
based on the Uranium fuel cycle.
Because of the cost of building nuclear plants in general, constructing
them solely for the purpose of providing the power to operate carbon dioxide
capture systems from coal or natural gas powered plants or from ambient air
is out of the question at present as is the same for solar or wind.
However, some believe that Thorium based nuclear power could
replace coal, natural gas and petroleum, the primary sources of new
greenhouse gas emissions and be the bridge to solar that at present does not
exist and if true, along with solar eventually greatly reduce future
greenhouse gas emissions globally. The analysis that follows attempts to
determine if Thorium is a practical path forward for nuclear or yet another
dead-end.
7

9. How do Thorium fuel cycle based reactors work?
All nuclear reactors operate with essentially the same goal to generate
heat energy that is in turn used to produce steam that spins a turbine that
turns a generator to produce electricity. The primary difference between the
production of electricity by a nuclear reactor and a coal or natural gas fired
power plant or a solar concentrator plant is the source of the heat energy.
The rest of the mechanics of the system are essentially identical.
In currently operated nuclear reactors, an unstable isotope of an
element, either uranium or plutonium is bombarded with neutrons from
nearby elements to fission these elements. This releases large quantities of
thermal energy relative to the mass of the element used according to the
formula derived by Albert Einstein e = mc2
, where m is the mass of the fuel
and c is the speed of light. This is why a few tons of uranium fuel can
provide the equivalent energy of thousands of tons of coal.
Three types of reactor fuel have been used to produce energy since the
technology was developed in the early 1940’s. In the first and the one most
commonly used today to produce electricity, Uranium 235 (U-235) is
separated from Uranium 238 (U-238) in mined Uranium ore. U-238 is the
predominant natural isotope, so an enrichment process is used to concentrate
the U-235 from 0.7 to around 3-4%.
By increasing the enrichment of U-235 beyond that needed to produce
electricity, a nuclear weapon can also be made. In a nuclear weapon, an
explosive charge slams together pieces of pure U-235 causing a sudden and
massive release of energy, a nuclear explosion. This was how the first
atomic bomb was manufactured and was the type bomb dropped on
Hiroshima. U-235 is unstable or fissile, releasing neutrons as it decays to
lighter elements, producing heat energy in the process. The neutrons from
one decaying atom of U-235 strike the nucleus of other atoms resulting in a
chain reaction process.
In a Light Water Reactor that is the design of all current U.S. reactors,
the decay is moderated by using water to slow the neutron release and to
keep the Uranium from melting. The nuclear fuel is contained in the form of
8

10. small pellets covered in zirconium cladding that are held in fuel rods. Fuel
from a nuclear reactor is generally replaced when about half of the U-235
has been converted to other elements. Fuel replacement occurs about every
17 months.
The second type of reactor fuel used is Plutonium-239. It is produced
by allowing U-238 to release neutrons to create the heavier Pu-239 that is
then separated and either used to produce electricity or make a nuclear
weapon. The atomic bomb dropped on Nagasaki was a Plutonium bomb.
No commercial power generating reactors use Pu-239 as the primary fuel
although Pu-239 produced during the operation of the reactor contributes to
overall thermal energy produced.
The third type reactor fuel uses Thorium. Thorium-232 obtained from
mined Thorium is bombarded with neutrons that it absorbs to ultimately
produce the unstable fissile element U-233 that can then be used to produce
electricity. Some Plutonium is also created in the process, but not enough to
make it a practical pathway to a nuclear weapon.
In the Thorium fuel cycle, Th-232 is known as the fertile precursor
material from which the fuel, U-233 is produced. Th-232 is itself not fissile,
so a fissile element must be present to start the chain reaction. The Th-232
first captures a neutron to become Th-233 that decays to Protactinium-233
(Pa-233) and finally Pa-233 decays to become U-233. Because more fuel is
produced than is used to initiate the reactions, it is known as a breeding
reaction and the reactors it would be used in classified as breeder reactors.
The process is similar to that of a Uranium breeder reactor where
fertile U-238 absorbs neutrons to also produce fissile Pu-239. The U-233
produced is either left in the reactor to fission into lighter elements or
chemically separated and made into new fuel. The design of the reactor and
the fuel cycle determine which is done.
Thorium is the only fertile material that can be used in the Thermal
Breeder Reactor (TBR). The TBR uses moderated thermal neutrons to
produce U-233 from Th-232. In this design, the core is surrounded by a
breeding blanket of the fertile material. The other type of breeder, the Fast
9

11. Breeder Reactor (FBR) uses fast, un-moderated neutrons to produce
Plutonium and fertile U-238. Thorium can also be used in the FBR.
Commercial Light Water Reactors (LWRs) also breed new fissile
material, mostly Plutonium, but not enough U-238 is converted to Plutonium
to replace the U-235 consumed. About one third of the power from LWRs
comes from Plutonium, but not enough of it to reduce its long-term activity
to that of fission products alone. The burn up rate or consumption rate of
fuel of breeders is much higher than that of LWRs and other non breeder
reactors because of the use of the actinides as fuel in the process.
Breeders have fallen into disfavor in part because their capital costs
are 25% more than LWRs and a sodium coolant leak could start a fire. For
cost and safety reasons, many of the countries that conducted the early
research on FBRs have abandoned research. India, Japan, China, S. Korea
and Russia are ramping up their research programs on FBRs, expecting that
rising Uranium prices will make FBR generated electricity competitive with
that from current reactors.
What are the advantages of Thorium-based nuclear power?
Use of thorium as a nuclear fuel precursor instead of U-235 or Pu-239
offers several advantages.
Greater Availability
Thorium is four times more abundant in the Earth’s crust than
Uranium-238 and almost 600 times more abundant than U-235, the fissile
isotope used as nuclear fuel. Nearly 3 million tons are believed to be readily
extractable from ores using existing mining technologies with large deposits
in the U.S., Australia, India, Turkey, Brazil and Venezuela accounting for
three fourths of known reserves.
The original interest in Thorium and breeder reactors in general was
that it could possibly replace or supplement Uranium if worldwide supplies
were depleted and that it didn’t require enrichment. Since Uranium supplies
have not become depleted in part due to the much smaller number of nuclear
10

12. reactors than was originally envisioned, because more Uranium reserves
have been discovered and because new methods of enrichment reduced
Uranium fuel costs, this advantage seems not as important today except in
nations like India that have large deposits of Thorium ore and little Uranium.
Millions more tons are assumed available in intermediate
concentrations and trillions of tons are present in total. We will never run
out of Thorium and since Uranium can also be extracted from seawater, we
will never run of it either. Nearly all of the naturally occurring Thorium-232
is fertile, i.e. can be used as the fuel to produce U-233 while only 0.7% of
naturally mined U-238 is the fissile U-235. So expensive enrichment
processes are not necessary.
These estimates have been used to calculate that Thorium could
satisfy all global electricity needs for the next 1000 years. However, U-238
could also be used to produce Pu-239, so Thorium is not necessary to
replace Uranium as Uranium supplies will not be depleted under the same
scenario of making all electricity from nuclear energy.
Lower Risk of Nuclear Weapons Proliferation
It is more difficult to make a nuclear weapon from the byproducts of
the Thorium fuel cycle. It produces only 2% of the Pu-239 of a standard
reactor using the Uranium-238 fuel cycle and there are other problems with
producing a bomb this way. Likewise, the U-233 produced from the
Thorium cycle is difficult to make into a bomb. If it were that easy, N.
Korea and Iran would have manufactured thousands of nuclear weapons by
now as would many other rogue nations in the past, e.g. Iraq and Syria.
Decay products of U-232 produced during the Thorium fuel cycle
emit high levels of gamma radiation that damages electronics limiting the
use of the U-233 in nuclear weapons as bomb triggers. Whether the U-233
could still be used in fabricating a bomb material with proper shielding of
the triggers was not discussed in references reviewed.
U-232 also cannot be chemically separated from U-233 in used
nuclear fuel. If residual Thorium in the fuel is separated, this removes the
decay isotope Th-228 and with it the gamma radiation producing decay
11

13. products. It is unclear if this would be an easy pathway to produce a nuclear
weapon.
Uranium-233 can also be denatured by mixing it with natural or
depleted uranium, requiring isotope separation before it could be used in
nuclear weapons as the level of U-233 would be too low to be of bomb
grade.
Use of a large Thorium breeding blanket over the other fissile material
would dilute the Pa-233 so that it would absorb fewer neutrons and produce
less U-233. This would come with the added expense of a larger fissile
inventory or a 2-fluid design with a large quantity of blanket salt in the case
that a molten salt reactor design is employed.
Less Nuclear Waste
The amount of radioactive waste generated is estimated to be about a
hundred times less than from that of the Uranium fuel cycle. This would
greatly reduce the need for short-term storage of spent fuel rods and the still
unsolved problem of long term disposal.
The radioactivity of the waste also decreases more rapidly, taking a
few hundred years to reach safe levels even lower than that of the Uranium
ore used to produce the fuel in a conventional LWR vs. tens of thousands of
years for waste from the Uranium fuel cycle. This is due to the smaller
quantities of Plutonium and other actinide (transuranic) elements produced
and based on the assumption that these actinides are fissioned during the fuel
cycle, converting them to more fission products while at the same time
contributing to the overall energy output of the reactor.
Other studies, however, have found that some of the actinide waste
accumulates and the resulting waste still requires long times to decay to safe
levels. The lack of operating experience with the Thorium fuel cycle leaves
this an open question.
Because a single neutron capture in U-238 produces transuranic
elements and six are required to do so with Th-232, 98-99% of the Thorium
reactor products will fission from either U-233 or U-235, producing less of
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14. the long-lived transuranics. For this reason, Thorium could be used in
mixed oxide fuels instead of Uranium to minimize production of
transuranics and maximize destruction of Plutonium.
Better Physical and Nuclear Properties
Because Thorium can be used as a molten salt, Thorium fluoride,
dissolved in a molten salt fluid, this eliminates the need to fabricate fuel
elements as is required for Uranium and Plutonium cycle solid fuel reactors,
saving money.
Thorium has three times the thermal neutron cross section of U-238
which results in more efficient conversion to U-233 which in turn has a
lower neutron capture cross section than U-235 and Pu-239 resulting in less
non fissile neutron absorptions. Thorium is therefore more efficient in
converting to a fissionable fuel than Uranium-based fuel.
When U-233 is produced from Th-232, it is much more likely to
fission upon neutron absorption than U-235, resulting in less transuranic
waste being produced than in a reactor using the Uranium or Plutonium fuel
cycles. The capture to fission ratio of U-233 is about 1:10 vs. U-235 (1:6) or
Pu-239 (1:2). Although some transuranic waste isotopes are produced using
Thorium they can be removed through chemical separation. The non-
transuranic Pa-231 that is formed is a major contributor to the long-term
radioactivity of the spent fuel as it has a half-life of over 10,000 years.
Thorium dioxide based fuel has a higher melting point, higher
conductivity and lower coefficient of thermal expansion than does Uranium
oxide. This is important in that there is less likelihood of a core meltdown in
the event of coolant loss. It is also more chemically stable and unlike
Uranium dioxide does not further oxidize. All of these factors could work to
improve reactor performance and stability in a repository after removal from
the reactor.
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15. What are the disadvantages of Thorium-based nuclear power?
Use of Thorium as a nuclear fuel instead of U-235 or Pu-239 has
several known and assumed disadvantages.
Slow Production of U-233/Fuel Efficiency
The process used to produce U-233 from Th-232 is time consuming.
It is not clear from the references reviewed exactly how much this would
affect use of Thorium as a fertile isotope. This results in a buildup of Pa-
233, which is a significant neutron absorber and results in more transuranic
production.
Higher burn up, i.e., use of the fuel is also required to achieve a
favorable neutron economy and may not be economical when used in a
LWR when the fuel is not recycled (open cycle).
Generation of Dangerous U-232
When used in a reactor, Th-232 also produces U-232 whose decay
products emit dangerous levels of gamma rays that require remote handling
during reprocessing when solid Thorium is used in a closed fuel cycle in
which the U-233 is recycled. This is also true of recycled Thorium fuel that
contains Th-228 that also produces U-232. There is also no proven
recycling technology for Thorium although one is being researched. It isn’t
possible to eliminate all of the U-232.
Fuel Fabrication and Reprocessing Issues
Because natural Thorium contains no fissile material, U-233, U-235
or Pu-239 must be added to achieve criticality in the chain reactions.
High temperatures must be used to sinter the Thorium dioxide fuel for
use in a solid fuel reactor. For this reason, Thorium tetrafluoride is much
easier to use as fuel in a molten salt reactor as well as easier to process and
separate from contaminants that slow or stop the chain reaction. This was
discovered when ORNL ran experiments with it in a test reactor in the
1960’s.
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16. Fuel fabrication using Thorium is said to be more expensive than with
U-235. How much more was not stated. Reprocessing of the fuel is also
said to be more expensive, although it may be expected to contain less long-
lived isotopes than fuel from the Uranium cycle.
However, no nuclear fuel of any kind is presently reprocessed since
doing this for the Uranium and Plutonium cycle fuels used in all currently
operating reactors would generates high-level nuclear waste streams that
require separate disposal and it has been banned by the U.S. government.
Their disposal/storage has been at the heart of the problem of what to do
with waste produced during weapons production in the 1940’s-1980’s when
most of the U.S. nuclear arsenal was created.
Some of the high level waste has been glassified and stored in
underground caverns in Carlsbad, New Mexico, but much of it remains on
site in Hanford, Washington and Idaho Falls, Idaho, a lasting legacy of the
Cold War. So reprocessing would seem to be a red herring argument with
regard to Thorium since it applies to Uranium fueled reactors as well.
Nevertheless, spent fuel rods would also start to accumulate rapidly if large
numbers of Thorium fueled reactors were built and operated in an open
cycle design in which the fuel is only used once.
Lack of Operating Experience
Many of the disadvantages of using solid fuel Thorium could be
negated by using it in a molten salt reactor or a liquid core reactor as a
fluoride salt. However, only two liquid core reactors have ever been built
and neither used Thorium, so there is no proof this work would be of benefit
in assessing its performance in such reactors. There has been some work
simulating using Thorium in a molten salt reactor (MSR) as discussed later.
In the type of MSR envisioned to use Thorium as the fuel precursor,
the fuel is a molten salt mixture of Thorium tetrafluoride. The molten salt is
the coolant while a graphite core is the moderator. MSRs are operated at
higher temperatures than water-cooled reactors to be more
thermodynamically efficient and since no water is involved, the vapor
pressure in the reactor zone is much lower. The ability to drain the liquid
fuel into a passively cooled and non-critical configuration makes them
15

17. inherently safer than Light Water Reactors that can experience core
meltdowns, e.g. Three Mile Island, Fukushima.
Continuous online processing of the fuel and its products could also
be an advantage of the MSR design. This would reduce the quantity of
fission products in the fuel including Xenon that is a good neutron absorber
and would reduce the efficiency of the process. This in turn would benefit
the use of the Thorium cycle where fewer neutrons are produced than in the
Uranium cycle.
Online fuel processing would also potentially increase worker
exposure to high levels of radioactivity in the event of accidents. This
reprocessing technology has been demonstrated on a laboratory scale. Scale
up to a commercial reactor design will require the development of an
economically competitive fuel salt cleaning system.
While several research reactors using the Thorium fuel cycle have
been built and operated for up to several years off and on since the 1960’s,
there is little practical commercial operating experience with reactors based
on it. For Thorium based reactors to replace existing ones would require
years if not decades of expensive design and testing as well as the
convoluted and drawn out licensing process already in place in the U.S. and
elsewhere for the last 50+ years. This is understandable and if one takes a
long-term view that Thorium may be a solution for the second half of the
21st
century, this need not be seen as an insurmountable obstacle.
However, as noted in the response to the next question, while some
governments are taking a look at Thorium, the private sector, namely
utilities are showing little interest as they are wedded to the Uranium fuel
cycle and are reluctant to go in a different direction, especially considering
the financial bath many of them took in the 1980’s as unfinished nuclear
plants forced them into bankruptcy. The bottom line is that unless one can
show that Thorium reactors will be less expensive to operate, the
utilities won’t touch them.
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18. What has been the experience to date with Thorium fuel cycle
reactors and what is to be expected in the near future?
The first fuel cycle reactor designed to use Thorium was an
experimental 7.4 MW one built at Oak Ridge National Laboratory (ORNL)
in 1965 that used the molten salt reactor design. It was operated off and on
for about 1.5 years total from 1965-1969, but only used U-233 bred from
Th-232 during its final year of operation. Articles reviewed differ on
whether Thorium was ever used as the Thorium breeder blanket was
removed to measure the neutron flux. The nuclear fuel used was Uranium
tetrafluoride. The reactor was shut down and never restarted, in part due to
congressional and military opposition, as they were only interested in
reactors that could make weapons grade material.
A proposed MSR breeder design using both Thorium and Uranium
tetrafluoride was later proposed but was never constructed. All U.S.
government research on Thorium was also ended in 1973 and the director of
ORNL, who was its chief supporter, forced to resign. Instead, research
dollars were allocated to the liquid metal fast breeder reactor program that
had greater political and technological support. Thus, when it had reached
the point where a much larger program would be justified, the Atomic
Energy Commission decided they could not fund both.
The third core of the Shippingport Atomic Power Station in
Pennsylvania, a 60MW commercial reactor was a light Thorium breeder that
operated from 1977-1982. Using pellets of Thorium dioxide and U-233
oxide it produced 1.4% more fissile material than when it was started,
evidence that Thorium breeding was possible.
Thorium has been used as a fuel in a number of different reactor
designs since then and continuing to present day including light water
reactors, heavy water reactors, high temperature gas reactors and sodium-
cooled fast reactors. The molten salt reactor research at ORNL is the only
conceptual use in this type reactor; the rest using solid fuel and Thorium
may not have been used as fuel in it.
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19. More interest began being shown after 2008 possibly because the
Kyoto Protocol went into effect that same year, the assumption made here
that interest in Thorium coincided with global warming mitigation needs.
Now more than a dozen nations are either conducting research or building
research reactors. The most significant ones are summarized below.
A Canadian company, Thorium Power Canada was in the mid 2000’s
negotiating to build 10 and 25MW solid thorium fueled reactors in Chile and
Indonesia, but no updates were given.
China claims to be developing two molten salt Thorium fuel cycle
reactors to be completed by 2015. They also stated that they would have a
working reactor online by 2025 to reduce air pollution. China, it must be
noted, exaggerates a lot. As evidence of this, the proposed completion date
for a test 2 MW pebble-bed solid-fuel Thorium reactor has been delayed
from 2015 to 2017. The proposed "test thorium molten-salt reactor" project
has also been delayed.
India seems to have the most ambitious program involving Thorium
based reactors, stating that it will have 62 in operation by 2025 and planning
to take advantage of its large deposits of Thorium as fuel as well as to
increase its percentage of electricity from nuclear from 3-25%. Several
reactors that could use Thorium are nearing completion, but just as with
China, the Indians make many claims that never seem to amount to
anything. One of these projects involves the advanced heavy water reactor
design. Both FBRs and Thermal Breeders using Thorium are being
developed.
Norway is currently using Thorium in an existing reactor.
A Texas company is building a research reactor that will use Thorium
as the primary fuel and expected to be operational in 2015. Other than this,
there is no private or U.S. government led Thorium program.
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20. Conclusions
According to a study conducted by MIT in 2011, even though there
are few technological barriers to building reactors employing the Thorium
fuel cycle, because of the popularity and acceptance of LWR designs there is
little reason for them to achieve market penetration and thus almost no
chance of them replacing Uranium fuel cycle reactors, despite possible
advantages.
Although the Thorium fuel cycle seems to offer some real advantages
over the Uranium and Plutonium fuel cycles, except for the claims made by
China and India, it also does not appear that much serious research is being
conducted and certainly not the kind that would lead to the operational
experience necessary to mainstream Thorium fuel cycle based reactors.
This is in part because of the inherent bias towards existing proven
technologies and the lack of a clear economic advantage offered by
Thorium. Until the latter can be shown, there will be little progress in this
area, a potential lost opportunity given the energy challenges ahead.
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September 6, 2014,
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21. 4. Construction schedule uncertain for new Georgia Power nuclear plant
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