Feasibility of Electricity GenerationUsing Thorium Based Nuclear Power-aPossible Solution to Global Warming?

Alvia Gaskill, Jr.

Environmental Reference Materials, Inc.

PO Box 12527 Research Triangle Park, NC 27709

September 6, 2014

Feasibility of Electricity GenerationUsing Thorium Based Nuclear Power-aPossible Solution to Global Warming?

This report was prepared using information gathered from Internetsearches and from the knowledge of the author who has been involved inresearch associated with energy and engineering solutions to global warmingfor the last 15 years. He also authored a report on high level nuclear wastedisposal options while in graduate school (1977) as well as studied thermalpollution from nuclear power plants while a summer student at the NCGovernor’s School in 1970 and authored a report while in college in 1974entitled “Nuclear Power, 4th Down and 100 Yards to Go.” The report ispresented in the form of general questions that would likely be asked if suchan analysis were to be performed for a customer.

What are the approaches being taken to solve the problem ofglobal warming?

The changes in climate (droughts, higher air temperatures, moresevere storms) and melting of ice sheets brought about by global warmingdue to human produced greenhouse gas emissions have resulted in a three-pronged approach to solve the problem: adaptation, geoengineering andmitigation.

Adaptation to the changes to the climate such as building sea wallsaround major cities to hold back sea level rise is being considered, but is nota solution and can only limit some of the damage.

Geoengineering, the deliberate modification of the energy balance ofthe atmosphere by removing carbon dioxide from ambient air or blockingsunlight has many challenges and is only seen as a means to buy time untilso-called sustainable energy solutions are achieved. Critics also claim that ifsuccessful, geoengineering could actually slow the development ofsustainable energy by reducing the incentive to make the necessary changes,i.e., the moral hazard.

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Mitigation, the reduction or elimination in emissions of greenhousegases, primarily carbon dioxide is viewed as the ultimate goal bypolicymakers. However, to return the energy balance to that of the pre-industrial period (before 1700) to achieve greenhouse gas levels in theatmosphere that will not result in long-term ice sheet disintegration will alsorequire the removal of the excess carbon dioxide from the atmosphere aswell as other gases or the equivalent amount of carbon dioxide to equal all ofthem. The so-called safe level for greenhouse gases in the atmosphere mayhave already been exceeded and will likely be anyway in the next severaldecades, regardless of mitigation efforts.

What are the options for mitigation that result in reduced orno new greenhouse gas emissions?

In an ideal future, all energy for generation of electricity, fortransportation and for operation of factories and heating of buildings wouldcome from sunlight or wind power which for the most part result in fewgreenhouse gas emissions. Because both are produced by energy fromsunlight, unlike fossil or nuclear fuel, their supply will never be exhaustedand at least in theory much of the power could be obtained throughdistributed systems, e.g. rooftop solar panels.

While production of solar energy and operation of equipment using itstill produces waste heat, this is not considered a significant problem for the21st century although it may be one further down the road. Neither solar orwind generated electricity at present is either economical or efficient enoughto meet the current or future needs by themselves and until storagetechnologies are available neither can supply base-load demand since bothare produced intermittently.

Reduction in emissions from existing technologies in part throughincreases in efficiency or where possible substituting natural gas for coal oradding solar or wind are the focus of most research and policymaking.Some improvements in efficiency with associated reduced emissions havealready been achieved in transportation through use of hybrid engines andreduced body weight of automobiles. As an example, annual gasoline

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consumption in the U.S. peaked around 2007 (142 billion gallons) and hasn’texceeded that level (135 billion gallons in 2013) even as the number ofvehicles on the road has increased and the number of miles driven. At leastsome of this can be attributed to more-efficient vehicles.

In the power generation sector, the switching from coal to natural gasis also expected to result in lower emissions in the U.S. but not globally dueto the lack of natural gas supplies in growing major electricity users likeChina and India that still depend upon coal or imported oil. Production ofnatural gas is a leaky process and there is some controversy over whether thenet emissions reduction over the life cycle of natural gas vs. coal is actuallyas great as advertised. Proposed EPA regulations on power generationemissions do not address life cycle concerns.

The way forward, accepted by most governments and internationalbodies (e.g. the Intergovernmental Panel on Climate Change-IPCC) is that ofa portfolio of technologies that includes fossil fuels, renewable energy fromwind and solar, hydroelectricity, bio-fuels and nuclear power.

How does nuclear power figure in the portfolio of futureoptions?

Nuclear plants provide about 19% of U.S. electricity base-loaddemand in 2014. This varies considerably from state to state. NorthCarolina gets 34% of its electricity from three nuclear power plants operatedby Duke Energy, the second highest in the country, but also gets 50% fromcoal. This contrasts with France that receives 75% of its electricity from 59reactors and exports some of the power generated to neighboring countries.Why nuclear is not higher nationally, especially considering the need toreduce greenhouse gas emissions from fossil fuels is discussed here.Although this report only addresses the U.S. nuclear power industry, as thelargest producer of nuclear energy in the world, the U.S. experience isinstructive.

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 numberof 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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construction. The industry has been beset for decades by cost overruns thatwere in part due to regulatory requirements added after high profileaccidents (Three Mile Island-1979, Chernobyl-1986, Fukushima-2011), buteven before Three Mile Island, costs were out of control.

Other factors that have limited the growth of nuclear include concernsabout the potential for use of power plants to produce nuclear weapons gradeplutonium (India, Pakistan, N. Korea, Iran), i.e. proliferation, the inability todeal 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 forglobal warming solutions. This isn’t likely to change in the next fewdecades as explained below in a look back at the U.S. nuclear powerindustry.

To say that the U.S. nuclear plant construction business has been badis a massive understatement. Of the 62 plants currently in operation, all ofthem began construction by 1974 and all of their reactors by 1977 untilrecently when five new reactors were approved for construction at existingplants in Georgia, South Carolina and Tennessee. Some of the reactors thatwere under construction were finally completed in the 1980’s, but only afterlong delays and massive cost overruns.

Even before Three Mile Island, cost overruns were impacting thenuclear power industry, averaging more than 200 percent for the 75 nuclearpower reactors built from 1966 to 1977. Due to the accident at Three MileIsland in 1979, new safety requirements were imposed and the economics ofelectricity generation by nuclear became even more unfavorable.

As a result, more than 120 orders for reactors were canceled includingmany under construction, bankrupting the utilities that owned them:Washington Public Power Supply System, Public Service of NewHampshire, Long Island Lighting, Consumers Power in Michigan andLouisiana Power and Light to name but a few. The author owned distressedbonds and preferred stock of several of these companies in the 1980’s andactually made money on them.

Of the approximately 250 reactors ordered from 1953 to 2008, half ofthese projects were canceled, 11 percent shut down before their licenses

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expired and 14% experienced a year or more outage. Half of the completedreactors still in service are more than 30 years old.

However, the measure of how much of the potential power fromplants is being generated by operating reactors has increased from less than60% in the 1970’s and 1980’s to more than 90% since 2001. This has madeup for the closing of eight reactors since 1991. Although there have beenmajor problems with the completion of reactors, after improvements insafety were made and operating experience was obtained, the existing plantshave proven to be safe and reliable with some exceptions.

After decades of zero growth, the so-called nuclear renaissance beganin the 2000’s spawned in part by a federal program to encourage nuclearpower plant construction and the perception nuclear could help solve thegreenhouse gas emissions problem for the U.S. This led utilities to onceagain submit applications for construction of new plants and reactors, butbecause of natural gas, lowered projections for electricity demand andFukushima, most of these projects were also canceled.

Of the remaining projects, construction of the Georgia and SouthCarolina reactors owned by Southern Company and SCANA began in 2013and resumed after a 25-year delay in Tennessee at a TVA plant. They arescheduled to come on line by 2017-2020, but in spite of federal loanguarantees, construction delays may push these dates back even further. TheTVA reactor project is currently over budget and behind schedule.

When the loans were announced in 2010 as part of its Nuclear Power2010 Program that was supposed to coordinate efforts for building newnuclear power plants, the Administration seemed upbeat about the future ofthe nuclear industry:

The reactors are "just the first of what we hope will be many newnuclear projects," said Carol Browner, director of the White House Office ofEnergy and Climate Change Policy. The former Clinton EPA Administratorand Gore confidant doesn’t work there anymore and it isn’t clear how muchcoordinating is still going on.

The failure of Congress and various administrations to reachagreement on how to dispose of spent fuel also continues to hamper future

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growth of the industry. At present in the U.S., some 65,000 tons of spentfuel rods are stored on site at existing plants, creating the potential for adisastrous release of radiation if the power to operate cooling pumps were tobe lost for an extended period of time due to either a hurricane, earthquakeor electromagnetic pulse from a solar flare.

Nine states also prohibit building any new nuclear reactors until astorage solution is found. While there is an international consensus that thisspent fuel should be stored deep underground in caves or salt mines nocountry 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 nuclearplants can be licensed in the U.S. until a waste fuel repository can becreated.

However, there does not appear to be a shortage of uranium to operateexisting plants or to fuel new ones. The U.S. has the fourth largest reservesin the world at 300 million pounds and imports 87% of that used fromCanada, Russia and Australia. This is enough to fuel existing reactors formore than a thousand years.

Since only about half of the uranium is used in a typical 17-monthcycle in a U.S. reactor, reprocessing of the spent fuel could extend supplieseven further. However, the current administration, along with others beforeit has banned reprocessing of spent fuel over concerns the Plutonium couldbe stolen and used to make nuclear weapons (unlikely because it is notweapons grade) or use it in a dirty bomb.

Other reasons are that there is no agreed upon repository for the highlevel actinide waste generated and because of the much higher cost ofreprocessing compared to the once-through fuel cycle presently used.Reprocessing is also a dangerous operation as it potentially exposes workersto very high levels of radiation.

The low price and increasing supply of natural gas along withproposed federal regulations has also made it the go to option for new powerplants instead of coal or nuclear resulting in some negative forecasts fornuclear in the near term.

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According to the U.S. DOE “Experts see continuing challenges thatwill make it very difficult for the nuclear power industry to expand beyond asmall handful of reactor projects that government agencies decide tosubsidize by forcing taxpayers to assume the risk for the reactors andmandating that ratepayers pay for construction in advance.”

An equally pessimistic assessment was issued by Excelon Energy inAugust 2012, at the time the nation’s largest utility, and operator of 17nuclear reactors, stating that “Economic and market conditions, especiallylow natural gas prices, made the construction of new merchant nuclearpower plants in competitive markets uneconomical now and for theforeseeable future.”

Because of all these factors, instead of planning new reactor or plantprojects, utilities are seeking license extensions for existing reactors andclosing old ones due to high maintenance and repair costs. The net effect ofthe new reactors from Southern Company, SCANA and the TVA and theretirements of older ones are expected to increase generating capacity byaround 5500 MW, not enough to move the dial on greenhouse gasemissions.

In spite of these challenges, nuclear may be poised to make yetanother comeback through use of a different kind of reactor, one fueled bythe naturally occurring element Thorium instead of Uranium or Plutonium.Advocates argue that it will result in safer and cheaper plants than thosebased on the Uranium fuel cycle.

Because of the cost of building nuclear plants in general, constructingthem solely for the purpose of providing the power to operate carbon dioxidecapture systems from coal or natural gas powered plants or from ambient airis out of the question at present as is the same for solar or wind.

However, some believe that Thorium based nuclear power couldreplace coal, natural gas and petroleum, the primary sources of newgreenhouse gas emissions and be the bridge to solar that at present does notexist and if true, along with solar eventually greatly reduce futuregreenhouse gas emissions globally. The analysis that follows attempts todetermine if Thorium is a practical path forward for nuclear or yet anotherdead-end.

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How do Thorium fuel cycle based reactors work?

All nuclear reactors operate with essentially the same goal to generateheat energy that is in turn used to produce steam that spins a turbine thatturns a generator to produce electricity. The primary difference between theproduction of electricity by a nuclear reactor and a coal or natural gas firedpower 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 anelement, either uranium or plutonium is bombarded with neutrons fromnearby elements to fission these elements. This releases large quantities ofthermal energy relative to the mass of the element used according to theformula derived by Albert Einstein e = mc2, where m is the mass of the fueland c is the speed of light. This is why a few tons of uranium fuel canprovide the equivalent energy of thousands of tons of coal.

Three types of reactor fuel have been used to produce energy since thetechnology was developed in the early 1940’s. In the first and the one mostcommonly used today to produce electricity, Uranium 235 (U-235) isseparated from Uranium 238 (U-238) in mined Uranium ore. U-238 is thepredominant natural isotope, so an enrichment process is used to concentratethe U-235 from 0.7 to around 3-4%.

By increasing the enrichment of U-235 beyond that needed to produceelectricity, a nuclear weapon can also be made. In a nuclear weapon, anexplosive charge slams together pieces of pure U-235 causing a sudden andmassive release of energy, a nuclear explosion. This was how the firstatomic bomb was manufactured and was the type bomb dropped onHiroshima. U-235 is unstable or fissile, releasing neutrons as it decays tolighter elements, producing heat energy in the process. The neutrons fromone decaying atom of U-235 strike the nucleus of other atoms resulting in achain 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 tokeep the Uranium from melting. The nuclear fuel is contained in the form of

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small pellets covered in zirconium cladding that are held in fuel rods. Fuelfrom a nuclear reactor is generally replaced when about half of the U-235has been converted to other elements. Fuel replacement occurs about every17 months.

The second type of reactor fuel used is Plutonium-239. It is producedby allowing U-238 to release neutrons to create the heavier Pu-239 that isthen separated and either used to produce electricity or make a nuclearweapon. The atomic bomb dropped on Nagasaki was a Plutonium bomb.No commercial power generating reactors use Pu-239 as the primary fuelalthough Pu-239 produced during the operation of the reactor contributes tooverall thermal energy produced.

The third type reactor fuel uses Thorium. Thorium-232 obtained frommined Thorium is bombarded with neutrons that it absorbs to ultimatelyproduce the unstable fissile element U-233 that can then be used to produceelectricity. Some Plutonium is also created in the process, but not enough tomake it a practical pathway to a nuclear weapon.

In the Thorium fuel cycle, Th-232 is known as the fertile precursormaterial 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-232first 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 isproduced than is used to initiate the reactions, it is known as a breedingreaction and the reactors it would be used in classified as breeder reactors.

The process is similar to that of a Uranium breeder reactor wherefertile U-238 absorbs neutrons to also produce fissile Pu-239. The U-233produced is either left in the reactor to fission into lighter elements orchemically separated and made into new fuel. The design of the reactor andthe fuel cycle determine which is done.

Thorium is the only fertile material that can be used in the ThermalBreeder Reactor (TBR). The TBR uses moderated thermal neutrons toproduce U-233 from Th-232. In this design, the core is surrounded by abreeding blanket of the fertile material. The other type of breeder, the Fast

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Breeder Reactor (FBR) uses fast, un-moderated neutrons to producePlutonium and fertile U-238. Thorium can also be used in the FBR.

Commercial Light Water Reactors (LWRs) also breed new fissilematerial, mostly Plutonium, but not enough U-238 is converted to Plutoniumto replace the U-235 consumed. About one third of the power from LWRscomes from Plutonium, but not enough of it to reduce its long-term activityto that of fission products alone. The burn up rate or consumption rate offuel of breeders is much higher than that of LWRs and other non breederreactors because of the use of the actinides as fuel in the process.

Breeders have fallen into disfavor in part because their capital costsare 25% more than LWRs and a sodium coolant leak could start a fire. Forcost and safety reasons, many of the countries that conducted the earlyresearch on FBRs have abandoned research. India, Japan, China, S. Koreaand Russia are ramping up their research programs on FBRs, expecting thatrising Uranium prices will make FBR generated electricity competitive withthat 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-239offers several advantages.

Greater Availability

Thorium is four times more abundant in the Earth’s crust thanUranium-238 and almost 600 times more abundant than U-235, the fissileisotope used as nuclear fuel. Nearly 3 million tons are believed to be readilyextractable from ores using existing mining technologies with large depositsin the U.S., Australia, India, Turkey, Brazil and Venezuela accounting forthree fourths of known reserves.

The original interest in Thorium and breeder reactors in general wasthat it could possibly replace or supplement Uranium if worldwide supplieswere depleted and that it didn’t require enrichment. Since Uranium supplieshave not become depleted in part due to the much smaller number of nuclear

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reactors than was originally envisioned, because more Uranium reserveshave been discovered and because new methods of enrichment reducedUranium fuel costs, this advantage seems not as important today except innations like India that have large deposits of Thorium ore and little Uranium.

Millions more tons are assumed available in intermediateconcentrations and trillions of tons are present in total. We will never runout of Thorium and since Uranium can also be extracted from seawater, wewill never run of it either. Nearly all of the naturally occurring Thorium-232is fertile, i.e. can be used as the fuel to produce U-233 while only 0.7% ofnaturally mined U-238 is the fissile U-235. So expensive enrichmentprocesses are not necessary.

These estimates have been used to calculate that Thorium couldsatisfy all global electricity needs for the next 1000 years. However, U-238could also be used to produce Pu-239, so Thorium is not necessary toreplace Uranium as Uranium supplies will not be depleted under the samescenario 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 ofthe Thorium fuel cycle. It produces only 2% of the Pu-239 of a standardreactor using the Uranium-238 fuel cycle and there are other problems withproducing a bomb this way. Likewise, the U-233 produced from theThorium cycle is difficult to make into a bomb. If it were that easy, N.Korea and Iran would have manufactured thousands of nuclear weapons bynow as would many other rogue nations in the past, e.g. Iraq and Syria.

Decay products of U-232 produced during the Thorium fuel cycleemit high levels of gamma radiation that damages electronics limiting theuse of the U-233 in nuclear weapons as bomb triggers. Whether the U-233could still be used in fabricating a bomb material with proper shielding ofthe triggers was not discussed in references reviewed.

U-232 also cannot be chemically separated from U-233 in usednuclear fuel. If residual Thorium in the fuel is separated, this removes thedecay isotope Th-228 and with it the gamma radiation producing decay

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products. It is unclear if this would be an easy pathway to produce a nuclearweapon.

Uranium-233 can also be denatured by mixing it with natural ordepleted uranium, requiring isotope separation before it could be used innuclear weapons as the level of U-233 would be too low to be of bombgrade.

Use of a large Thorium breeding blanket over the other fissile materialwould dilute the Pa-233 so that it would absorb fewer neutrons and produceless U-233. This would come with the added expense of a larger fissileinventory or a 2-fluid design with a large quantity of blanket salt in the casethat a molten salt reactor design is employed.

Less Nuclear Waste

The amount of radioactive waste generated is estimated to be about ahundred times less than from that of the Uranium fuel cycle. This wouldgreatly reduce the need for short-term storage of spent fuel rods and the stillunsolved problem of long term disposal.

The radioactivity of the waste also decreases more rapidly, taking afew hundred years to reach safe levels even lower than that of the Uraniumore used to produce the fuel in a conventional LWR vs. tens of thousands ofyears for waste from the Uranium fuel cycle. This is due to the smallerquantities of Plutonium and other actinide (transuranic) elements producedand based on the assumption that these actinides are fissioned during the fuelcycle, converting them to more fission products while at the same timecontributing to the overall energy output of the reactor.

Other studies, however, have found that some of the actinide wasteaccumulates and the resulting waste still requires long times to decay to safelevels. The lack of operating experience with the Thorium fuel cycle leavesthis an open question.

Because a single neutron capture in U-238 produces transuranicelements and six are required to do so with Th-232, 98-99% of the Thoriumreactor products will fission from either U-233 or U-235, producing less of

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the long-lived transuranics. For this reason, Thorium could be used inmixed oxide fuels instead of Uranium to minimize production oftransuranics 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 fuelelements as is required for Uranium and Plutonium cycle solid fuel reactors,saving money.

Thorium has three times the thermal neutron cross section of U-238which results in more efficient conversion to U-233 which in turn has alower neutron capture cross section than U-235 and Pu-239 resulting in lessnon fissile neutron absorptions. Thorium is therefore more efficient inconverting to a fissionable fuel than Uranium-based fuel.

When U-233 is produced from Th-232, it is much more likely tofission upon neutron absorption than U-235, resulting in less transuranicwaste being produced than in a reactor using the Uranium or Plutonium fuelcycles. The capture to fission ratio of U-233 is about 1:10 vs. U-235 (1:6) orPu-239 (1:2). Although some transuranic waste isotopes are produced usingThorium they can be removed through chemical separation. The non-transuranic Pa-231 that is formed is a major contributor to the long-termradioactivity of the spent fuel as it has a half-life of over 10,000 years.

Thorium dioxide based fuel has a higher melting point, higherconductivity and lower coefficient of thermal expansion than does Uraniumoxide. This is important in that there is less likelihood of a core meltdown inthe event of coolant loss. It is also more chemically stable and unlikeUranium dioxide does not further oxidize. All of these factors could work toimprove reactor performance and stability in a repository after removal fromthe reactor.

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What are the disadvantages of Thorium-based nuclear power?

Use of Thorium as a nuclear fuel instead of U-235 or Pu-239 hasseveral 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 wouldaffect 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 transuranicproduction.

Higher burn up, i.e., use of the fuel is also required to achieve afavorable neutron economy and may not be economical when used in aLWR 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 decayproducts emit dangerous levels of gamma rays that require remote handlingduring reprocessing when solid Thorium is used in a closed fuel cycle inwhich the U-233 is recycled. This is also true of recycled Thorium fuel thatcontains Th-228 that also produces U-232. There is also no provenrecycling technology for Thorium although one is being researched. It isn’tpossible to eliminate all of the U-232.

Fuel Fabrication and Reprocessing Issues

Because natural Thorium contains no fissile material, U-233, U-235or Pu-239 must be added to achieve criticality in the chain reactions.

High temperatures must be used to sinter the Thorium dioxide fuel foruse in a solid fuel reactor. For this reason, Thorium tetrafluoride is mucheasier to use as fuel in a molten salt reactor as well as easier to process andseparate from contaminants that slow or stop the chain reaction. This wasdiscovered when ORNL ran experiments with it in a test reactor in the1960’s.

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Fuel fabrication using Thorium is said to be more expensive than withU-235. How much more was not stated. Reprocessing of the fuel is alsosaid 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 sincedoing this for the Uranium and Plutonium cycle fuels used in all currentlyoperating reactors would generates high-level nuclear waste streams thatrequire 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 dowith waste produced during weapons production in the 1940’s-1980’s whenmost of the U.S. nuclear arsenal was created.

Some of the high level waste has been glassified and stored inunderground caverns in Carlsbad, New Mexico, but much of it remains onsite in Hanford, Washington and Idaho Falls, Idaho, a lasting legacy of theCold War. So reprocessing would seem to be a red herring argument withregard to Thorium since it applies to Uranium fueled reactors as well.Nevertheless, spent fuel rods would also start to accumulate rapidly if largenumbers of Thorium fueled reactors were built and operated in an opencycle design in which the fuel is only used once.

Lack of Operating Experience

Many of the disadvantages of using solid fuel Thorium could benegated by using it in a molten salt reactor or a liquid core reactor as afluoride salt. However, only two liquid core reactors have ever been builtand neither used Thorium, so there is no proof this work would be of benefitin assessing its performance in such reactors. There has been some worksimulating 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 isthe coolant while a graphite core is the moderator. MSRs are operated athigher temperatures than water-cooled reactors to be morethermodynamically efficient and since no water is involved, the vaporpressure in the reactor zone is much lower. The ability to drain the liquidfuel into a passively cooled and non-critical configuration makes them

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inherently safer than Light Water Reactors that can experience coremeltdowns, e.g. Three Mile Island, Fukushima.

Continuous online processing of the fuel and its products could alsobe an advantage of the MSR design. This would reduce the quantity offission products in the fuel including Xenon that is a good neutron absorberand would reduce the efficiency of the process. This in turn would benefitthe use of the Thorium cycle where fewer neutrons are produced than in theUranium cycle.

Online fuel processing would also potentially increase workerexposure to high levels of radioactivity in the event of accidents. Thisreprocessing technology has been demonstrated on a laboratory scale. Scaleup to a commercial reactor design will require the development of aneconomically competitive fuel salt cleaning system.

While several research reactors using the Thorium fuel cycle havebeen built and operated for up to several years off and on since the 1960’s,there is little practical commercial operating experience with reactors basedon it. For Thorium based reactors to replace existing ones would requireyears if not decades of expensive design and testing as well as theconvoluted and drawn out licensing process already in place in the U.S. andelsewhere for the last 50+ years. This is understandable and if one takes along-term view that Thorium may be a solution for the second half of the21st century, this need not be seen as an insurmountable obstacle.

However, as noted in the response to the next question, while somegovernments are taking a look at Thorium, the private sector, namelyutilities are showing little interest as they are wedded to the Uranium fuelcycle and are reluctant to go in a different direction, especially consideringthe financial bath many of them took in the 1980’s as unfinished nuclearplants forced them into bankruptcy. The bottom line is that unless one canshow that Thorium reactors will be less expensive to operate, theutilities won’t touch them.

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What has been the experience to date with Thorium fuel cyclereactors and what is to be expected in the near future?

The first fuel cycle reactor designed to use Thorium was anexperimental 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 onfor about 1.5 years total from 1965-1969, but only used U-233 bred fromTh-232 during its final year of operation. Articles reviewed differ onwhether Thorium was ever used as the Thorium breeder blanket wasremoved to measure the neutron flux. The nuclear fuel used was Uraniumtetrafluoride. The reactor was shut down and never restarted, in part due tocongressional and military opposition, as they were only interested inreactors that could make weapons grade material.

A proposed MSR breeder design using both Thorium and Uraniumtetrafluoride was later proposed but was never constructed. All U.S.government research on Thorium was also ended in 1973 and the director ofORNL, who was its chief supporter, forced to resign. Instead, researchdollars were allocated to the liquid metal fast breeder reactor program thathad greater political and technological support. Thus, when it had reachedthe point where a much larger program would be justified, the AtomicEnergy Commission decided they could not fund both.

The third core of the Shippingport Atomic Power Station inPennsylvania, a 60MW commercial reactor was a light Thorium breeder thatoperated from 1977-1982. Using pellets of Thorium dioxide and U-233oxide 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 reactordesigns since then and continuing to present day including light waterreactors, heavy water reactors, high temperature gas reactors and sodium-cooled fast reactors. The molten salt reactor research at ORNL is the onlyconceptual use in this type reactor; the rest using solid fuel and Thoriummay not have been used as fuel in it.

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More interest began being shown after 2008 possibly because theKyoto Protocol went into effect that same year, the assumption made herethat interest in Thorium coincided with global warming mitigation needs.Now more than a dozen nations are either conducting research or buildingresearch reactors. The most significant ones are summarized below.

A Canadian company, Thorium Power Canada was in the mid 2000’snegotiating to build 10 and 25MW solid thorium fueled reactors in Chile andIndonesia, but no updates were given.

China claims to be developing two molten salt Thorium fuel cyclereactors to be completed by 2015. They also stated that they would have aworking reactor online by 2025 to reduce air pollution. China, it must benoted, exaggerates a lot. As evidence of this, the proposed completion datefor a test 2 MW pebble-bed solid-fuel Thorium reactor has been delayedfrom 2015 to 2017. The proposed "test thorium molten-salt reactor" projecthas also been delayed.

India seems to have the most ambitious program involving Thoriumbased reactors, stating that it will have 62 in operation by 2025 and planningto take advantage of its large deposits of Thorium as fuel as well as toincrease its percentage of electricity from nuclear from 3-25%. Severalreactors that could use Thorium are nearing completion, but just as withChina, the Indians make many claims that never seem to amount toanything. One of these projects involves the advanced heavy water reactordesign. Both FBRs and Thermal Breeders using Thorium are beingdeveloped.

Norway is currently using Thorium in an existing reactor.

A Texas company is building a research reactor that will use Thoriumas 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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Conclusions

According to a study conducted by MIT in 2011, even though thereare few technological barriers to building reactors employing the Thoriumfuel cycle, because of the popularity and acceptance of LWR designs there islittle reason for them to achieve market penetration and thus almost nochance of them replacing Uranium fuel cycle reactors, despite possibleadvantages.

Although the Thorium fuel cycle seems to offer some real advantagesover the Uranium and Plutonium fuel cycles, except for the claims made byChina and India, it also does not appear that much serious research is beingconducted and certainly not the kind that would lead to the operationalexperience necessary to mainstream Thorium fuel cycle based reactors.

This is in part because of the inherent bias towards existing proventechnologies and the lack of a clear economic advantage offered byThorium. Until the latter can be shown, there will be little progress in thisarea, a potential lost opportunity given the energy challenges ahead.

Sources

1. How much gasoline does the United States consume? Energy InformationAdministration, May 13, 2014,http://www.eia.gov/tools/faqs/faq.cfm?id=23&t=10, accessed September 6,2014.

2. Nuclear basics: energy in your state, North Carolina, CASEnergyCoalition, September 2014,http://casenergy.org/nuclear-basics/energy-in-your-state/north-carolina/,accessed September 6, 2014.

3. Nuclear Power in the United States, Wikipedia, the free encyclopedia.htm,September 6, 2014,http://en.wikipedia.org/wiki/Nuclear_power_in_the_United_States, accessedSeptember 6, 2014.

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4. Construction schedule uncertain for new Georgia Power nuclear plantnear South Carolina line, Associated Press, August 28, 2014,http://www.foxbusiness.com/markets/2014/08/28/construction-schedule-uncertain-for-new-georgia-power-nuclear-plant-near-south/, accessedAugust 28, 2014.

5. Thorium-based nuclear power, Wikipedia, the free encyclopedia.htm,August 30, 2014, en.wikipedia.org/wiki/Thorium-based_nuclear_power,accessed September 6, 2014.

6. Thorium fuel cycle, Wikipedia, the free encyclopedia.htm, August 15,2014, http://en.wikipedia.org/wiki/Thorium_fuel_cycle, accessed September6, 2014.

7. Molten salt reactor, Wikipedia, the free encyclopedia.htm, August 23,2014, http://en.wikipedia.org/wiki/Molten_Salt_Reactor, accessedSeptember 6, 2014.

8. Breeder reactor, Wikipedia, the free encyclopedia.htm, September 4,2014, http://en.wikipedia.org/wiki/Breeder_reactor, accessed September 6,2014.

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