Presentation on theme: "Thorium and the Liquid-Fluoride Thorium Reactor Concept"— Presentation transcript:
1 Thorium and the Liquid-Fluoride Thorium Reactor Concept
2 World Energy Consumption is Rapidly Escalating Future Energy Consumption Has Been Significantly UnderestimatedIn 2007, the world consumed*:5.3 billion tonnes of coal (128 quads**)31.1 billion barrels of oil (180 quads)2.92 trillion m3 of natural gas (105 quads)Contained 16,000 MT of thorium!Dominated by Hydrocarbons65 million kg of uranium ore (25 quads)Total Energy Demand Projections (quads)***29 quads of hydroelectricityYearUSWorld201010851020201216132030134722In a global warming environment, where will the world turn for safe, abundant, low-cost energy?*Source: BP Statistical Review of World Energy 2008***Source: Energy Information Administration Outlook 2006**1 quad = 1 quadrillion BTU = 172 million barrels (Mbbl) of crude oil
3 The Binding Energy of Matter Nucleons (protons and neutrons) have binding energies of millions of eV’s.Electrons have binding energies of eV’s.
4 Supernova—Birth of the Heavy Elements Thorium, uranium, and all the other heavy elements were formed in the final moments of a supernova explosion billions of years ago.Our solar system: the Sun, planets, Earth, Moon, and asteroids formed from the remnants of this material.
5 Fissile fuel has extraordinary energy density! 23 million kilowatt-hours per kilogram!
6 Energy Generation Comparison 230 train cars (25,000 MT) of bituminous coal or,600 train cars (66,000 MT) of brown coal,(Source: World Coal Institute)=or, 440 million cubic feet of natural gas (15% of a 125,000 cubic meter LNG tanker),6 kg of fissile material in a liquid-fluoride reactor has the energy equivalent (66,000 MW*hr electrical*) of:*Each ounce of thorium can therefore produce $14,000-24,000 of electricity (at $ /kW*hr)or, 300 kg of enriched (3%) uranium in a pressurized water reactor.
7 Nature gave us three options for fissile fuel The fission of U-235 was discovered by Otto Hahn and Lise Meitner in 1938.Uranium-235(0.7% of all U)Pu-239 as a fissile fuel was discovered by Glenn Seaborg in March 1941.Uranium-238(99.3% of all U)Plutonium-239U-233 as a fissile fuel was discovered by Seaborg’s student John Gofman in February 1942.Thorium-232(100% of all Th)Uranium-233
8 Could weapons be made from the fissile material? Uranium-235(“highly enriched uranium”)Natural uraniumIsotope separation plant (Y-12)Hiroshima, 8/6/1945Depleted uraniumIsotope Production Reactor (Hanford)Pu separation from exposed U (PUREX)Trinity, 7/16/1945 Nagasaki, 8/9/1945PROBLEM: U-233 is contaminated with U-232, whose decay chain emits HARD gamma rays that make fabrication, utilization and deployment of weapons VERY difficult and impractical relative to other options. Thorium was not pursued.Isotope Production Reactoruranium separation from exposed thoriumThorium?
9 U-232 decays into Tl-208, a HARD gamma emitter Thallium-208 emits “hard” 2.6 MeV gamma-rays as part of its nuclear decay.These gamma rays destroy the electonics and explosives that control detonation.They require thick lead shielding and have a distinctive and easily detectable signature.232U14 billion years to make this jumpSome 232U starts decaying immediately1.91 yr1.91 yr1.91 yr3.64 d3.64 d3.64 dUranium-232 follows the same decay chain as thorium-232, but it follows it millions of times faster!This is because 232Th has a 14 billion-year half-life, but 232U has only an 74 year half-life!Once it starts down “the hill” it gets to thallium-208 (the gamma emitter) in just a few weeks!55 sec55 sec0.16 sec
11 1944: A tale of two isotopes… Enrico Fermi argued for a program of fast-breeder reactors using uranium-238 as the fertile material and plutonium-239 as the fissile material.His argument was based on the breeding ratio of Pu-239 at fast neutron energies.Argonne National Lab followed Fermi’s path and built the EBR-1 and EBR-2.Eugene Wigner argued for a thermal-breeder program using thorium as the fertile material and U-233 as the fissile material.Although large breeding gains were not possible, THERMAL breeding was possible, with enhanced safety.Wigner’s protégé, Alvin Weinberg, followed Wigner’s path at the Oak Ridge National Lab.
12 Can Nuclear Reactions be Sustained in Natural Uranium? Goal of fast breeder reactorsMost of Pu burnedFast reactors keep neutrons here, but at a high price:SafetyMore fuel (5x)RealityThermalFastSpectrumModerated SpectrumSpectrumPu-240ProductionProduces long-lived ActinidesYucca MtnGreater propensity to absorb neutronsStartNot with thermal neutrons—need more than 2 neutrons to sustain reaction (one for conversion, one for fission)—not enough neutrons produced at thermal energies. Must use fast neutron reactors.
14 Neutrons are moderated through collisions Neutron born at high energy (1-2 MeV).Neutron moderated to thermal energy (<<1 eV).
15 Radiation Damage Limits Energy Release Does a typical nuclear reactor extract that much energy from its nuclear fuel?No, the “burnup” of the fuel is limited by damage to the fuel itself.Typically, the reactor will only be able to extract a portion of the energy from the fuel before radiation damage to the fuel itself becomes too extreme.Radiation damage is caused by:Noble gas (krypton, xenon) buildupDisturbance to the fuel lattice caused by fission fragments and neutron fluxAs the fuel swells and distorts, it can cause the cladding around the fuel to rupture and release fission products into the coolant.
16 Lifetime of a Typical Uranium Fuel Element Conventional fuel elements are fabricated from uranium pellets and formed into fuel assembliesThey are then irradiated in a nuclear reactor, where most of the U-235 content of the fuel “burns” out and releases energy.Finally, they are placed in a spent fuel cooling pond where decay heat from radioactive fission products is removed by circulating water.
17 Typical Pressurized-Water Reactor Containment This structure is steel-lined reinforced concrete, designed to withstand the overpressure expected if all the primary coolant were released in an accident.Sprays and cooling systems (such as the ice condenser) are available for washing released radioactivity out of the containment atmosphere and for cooling the internal atmosphere, thereby keeping the pressure below the containment design pressure.The basic purpose of the containment system, including its spray and cooling functions, is to minimize the amount of released radioactivity that escapes to the external environment.
18 Radiotoxicity of fission products over time Ingestion toxicity of the fission products from a uranium-fueled LWR.Inhalation toxicity of the fission products from a uranium-fueled LWR.
19 Can Nuclear Reactions be Sustained in Natural Thorium? FastThermal SpectrumModerated SpectrumSpectrumU-234No Advantage for ThoriumU-232 contaminates U-233 and cannot be removedPrevents U-233 being used as weaponStartYes! Enough neutrons to sustain reaction produced at thermal fission. Does not need fast neutron reactors—needs neutronic efficiency.
20 Thorium-Uranium Breeding Cycle Protactinium-233 decays more slowly (half-life of 27 days) to uranium-233 by emitting a beta particle (an electron).Thorium-233 decays quickly (half-life of 22.3 min) to protactinium-233 by emitting a beta particle (an electron).It is important that Pa-233 NOT absorb a neutron before it decays to U-233—it should be isolated from any neutrons until it decays.Pa-233Th-233U-233Uranium-233 is fissile and will fission when struck by a neutron, releasing energy and 2 to 3 neutrons. One neutron is needed to sustain the chain-reaction, one neutron is needed for breeding, and any remainder can be used to breed additional fuel.Thorium-232 absorbs a neutron from fission and becomes thorium-233.Th-232
21 1944: A tale of two isotopes… “But Eugene, how will you reprocess the thorium fuel effectively?”“We’ll build a fluid-fueled reactor, that’s how…”
22 ORNL Fluid-Fueled Thorium Reactor Progress (1947-1960) 1947 – Eugene Wigner proposes a fluid-fueled thorium reactor1950 – Alvin Weinberg becomes ORNL director1952 – Homogeneous Reactor Experiment (HRE-1) built and operated successfully (100 kWe, 550K)1959 – AEC convenes “Fluid Fuels Task Force” to choose between aqueous homogeneous reactor, liquid fluoride, and liquid-metal-fueled reactor. Fluoride reactor is chosen and AHR is cancelled.Weinberg attempts to keep both aqueous and fluoride reactor efforts going in parallel but ultimately decides to pursue fluoride reactor.1958 – Homogeneous Reactor Experiment-2 proposed with 5 MW of power
23 Aircraft Nuclear Program Between 1946 and 1961, the USAF sought to develop a long-range bomber based on nuclear power.The Aircraft Nuclear Program had unique requirements, some very similar to a space reactor.High temperature operation (>1500° F)Critical for turbojet efficiency3X higher than sub reactorsLightweight designCompact core for minimal shieldingLow-pressure operationEase of operabilityInherent safety and controlEasily removeable
24 Ionically-bonded fluids are impervious to radiation The basic problem in nuclear fuel is that it is covalently bonded and in a solid form.If the fuel were a fluid salt, its ionic bonds would be impervious to radiation damage and the fluid form would allow easy extraction of fission product gases, thus permitting unlimited burnup.
25 The Aircraft Reactor Experiment (ARE) In order to test the liquid-fluoride reactor concept, a solid-core, sodium-cooled reactor was hastily converted into a proof-of-concept liquid-fluoride reactor.The Aircraft Reactor Experiment ran for 100 hours at the highest temperatures ever achieved by a nuclear reactor (1150 K).Operated from 11/03/54 to 11/12/54Liquid-fluoride salt circulated through beryllium reflector in Inconel tubes235UF4 dissolved in NaF-ZrF4Produced 2.5 MW of thermal powerGaseous fission products were removed naturally through pumping actionVery stable operation due to high negative reactivity coefficientDemonstrated load-following operation without control rods
26 Aircraft Nuclear Program allowed ORNL to develop reactors It wasn’t that I had suddenly become converted to a belief in nuclear airplanes. It was rather that this was the only avenue open to ORNL for continuing in reactor development.That the purpose was unattainable, if not foolish, was not so important:A high-temperature reactor could be useful for other purposes even if it never propelled an airplane…—Alvin Weinberg
27 ORNL Aircraft Nuclear Reactor Progress (1949-1960) 1949 – Nuclear Aircraft Concept formulated1951 – R.C. Briant proposed Liquid-Fluoride Reactor1952, 1953 – Early designs for aircraft fluoride reactor1954 – Aircraft Reactor Experiment (ARE) built and operated successfully (2500 kWt, 1150K)1955 – 60 MWt Aircraft Reactor Test (ART, “Fireball”) proposed for aircraft reactor1960 – Nuclear Aircraft Program cancelled in favor of ICBMs
28 Fluid-Fueled Reactors for Thorium Energy Liquid-Fluoride Reactor (ORNL)Aqueous Homogenous Reactor (ORNL)Liquid-Metal Fuel Reactor (BNL)Uranium tetrafluoride dissolved in lithium fluoride/beryllium fluoride.Thorium dissolved as a tetrafluoride.Two built and operated.Uranyl sulfate dissolved in pressurized heavy water.Thorium oxide in a slurry.Two built and operated.Uranium metal dissolved in bismuth metal.Thorium oxide in a slurry.Conceptual—none built and operated.
30 LFTR is totally passively safe in case of accident The reactor is equipped with a “freeze plug”—an open line where a frozen plug of salt is blocking the flow.The plug is kept frozen by an external cooling fan.Freeze PlugIn the event of TOTAL loss of power, the freeze plug melts and the core salt drains into a passively cooled configuration where nuclear fission is impossible.Drain Tank
32 LFTR produces far less mining waste than LWR ( ~4000:1 ratio) 1 GW*yr of electricity from a uranium-fueled light-water reactorConversion to natural UF6 (247 MT U)Mining 800,000 MT of ore containing 0.2% uranium (260 MT U)Milling and processing to yellowcake—natural U3O8 (248 MT U)Generates 170 MT of solid waste and 1600 m3 of liquid wasteGenerates ~600,000 MT of waste rockGenerates 130,000 MT of mill tailings1 GW*yr of electricity from a thorium-fueled liquid-fluoride reactorMining 200 MT of ore containing 0.5% thorium (1 MT Th)Milling and processing to thorium nitrate ThNO3 (1 MT Th)Generates 0.1 MT of mill tailings and 50 kg of aqueous wastesGenerates ~199 MT of waste rockUranium fuel cycle calculations done using WISE nuclear fuel material calculator:
33 LFTR produces less operational waste than LWR, (mission: make 1000 MW of electricity for one year) 35 t of enriched uranium (1.15 t U-235)Uranium-235 content is “burned” out of the fuel; some plutonium is formed and burned35 t of spent fuel stored on-site until disposal at Yucca Mountain. It contains:33.4 t uranium-2380.3 t uranium-2350.3 t plutonium1.0 t fission products.250 t of natural uranium containing 1.75 t U-235215 t of depleted uranium containing 0.6 t U-235—disposal plans uncertain.Within 10 years, 83% of fission products are stable and can be partitioned and sold.One tonne of natural thoriumOne tonne of fission products; no uranium, plutonium, or other actinides.Thorium introduced into blanket of fluoride reactor; completely converted to uranium-233 and “burned”.The remaining 17% fission products go to geologic isolation for ~300 years.
34 Thorium Fuel SupplyThorium is abundant around the world and rich in energyEstimated world reserve base of 1.4 million MTUS has about 20% of the world reserve baseA single mine site in Idaho could produce 4500 MT of thorium/yearUS currently would use about 400 MT/year for electricity productionWorld Thorium ResourcesCountryAustraliaIndiaUSANorwayCanadaSouth AfricaBrazilOther countriesWorld totalReserve Base (tons)340,000300,000180,000100,00039,00018,0001,400,000Source: U.S. Geological Survey, Mineral Commodity Summaries, January 2008The United States has buried 3200 metric tons of thorium nitrate in the Nevada desert.
35 A single mine site in Idaho could recover 4500 MT of thorium per year
36 ANWR times 6 in the Nevada desert Between 1957 and 1964, the Defense National Stockpile Center procured 3215 metric tonnes of thorium from suppliers in France and India.Recently, due to “lack of demand”, they decided to bury this entire inventory at the Nevada Test Site.This thorium is equivalent to 240 quads of energy*, if completely consumed in a liquid-fluoride reactor.*This is based on an energy release of ~200 Mev/232 amu and complete consumption. This energy can be converted to electricity at ~50% efficiency using a multiple-reheat helium gas turbine; or to hydrogen at ~50% efficiency using a thermo-chemical process such as the sulfur-iodine process.
37 Thorium Resources in the United States 3200 metric tonnes of thorium nitrate buried at Nevada Test SiteLemhi Pass, Idaho (best mining site in US)Conway Shale, NH316114151317181145610987Monazite beach sands in Georgia and Florida
38 LFTR could produce many valuable by-products ThoriumDesalination to Potable WaterFacilities HeatingLow-temp Waste HeatLiquid-Fluoride Thorium ReactorPower ConversionElectrical Generation (50% efficiency)Electrical loadElectrolytic H2Process HeatCoal-Syn-Fuel ConversionThermo-chemical H2Oil shale/tar sands extractionSeparated Fission ProductsCrude oil “cracking”Hydrogen fuel cellAmmonia (NH3) GenerationStrontium-90 for radioisotope powerCesium-137 for medical sterilizationRhodium, Ruthenium as stable rare-earthsTechnetium-99 as catalystMolybdenum-99 for medical diagnosticsIodine-131 for cancer treatmentXenon for ion enginesFertilizer for AgricultureAutomotive Fuel Cell (very simple)These products may be as important as electricity production
39 The byproducts of conventional reactors are more limited UraniumLow-temp Waste HeatLight-Water ReactorPower ConversionElectrical Generation (35% efficiency)Electrical loadElectrolytic H2Crude oil “cracking”Hydrogen fuel cellAmmonia (NH3) GenerationFertilizer for AgricultureAutomotive Fuel Cell (very simple)
40 LFTR can be environmentally friendly Does not produce “green house” gasesCan be air-cooledConsequently does not vent heat into rivers and lakesSmaller cooling towersLittle operations wasteOption of retaining waste storage on siteOperational waste products decay very rapidlyLittle mining wasteNo large open pits, large waste “mountains”Large Cooling TowersNuclear WasteConcern about waste disposal has hampered nuclear industry growth – and energy supplyOpen Pit Mine
41 Why wasn’t this done? No Plutonium Production! Alvin Weinberg:“Why didn't the molten-salt system, so elegant and so well thought-out, prevail? I've already given the political reason: that the plutonium fast breeder arrived first and was therefore able to consolidate its political position within the AEC. But there was another, more technical reason. [Fluoride reactor] technology is entirely different from the technology of any other reactor. To the inexperienced, [fluoride] technology is daunting…“Mac” MacPherson:The political and technical support for the program in the United States was too thin geographically…only at ORNL was the technology really understood and appreciated. The thorium-fueled fluoride reactor program was in competition with the plutonium fast breeder program, which got an early start and had copious government development funds being spent in many parts of the United States.“It was a successful technology that was dropped because it was too different from the main lines of reactor development… I hope that in a second nuclear era, the [fluoride-reactor] technology will be resurrected.”
42 LFTR could cost much less than LWR No pressure vessel requiredLiquid fuel requires no expensive fuel fabrication and qualificationSmaller power conversion systemNo steam generators requiredFactory built-modular constructionScalable: 100 KW to multi GWSmaller containment building neededSteam vs. fluidsSimpler operationNo operational control rodsNo re-fueling shut downSignificantly lower maintenanceSignificantly smaller staffSignificantly lower capital costsLower regulatory burden
43 The Current Plan is to Dispose Fuel in Yucca Mountain
48 How does a fluoride reactor use thorium? Metallic thoriumPa-233Decay Tank238UFertile SaltBismuth-metal Reductive Extraction ColumnFluorideVolatilityPa233UF6Recycle Fertile SaltUraniumAbsorption-ReductionCore7LiF-BeF2Recycle Fuel Salt7LiF-BeF2-UF4Blanket233,234UF6VacuumDistillationHexafluorideDistillationTwo-Fluid ReactorxF6“Bare” SaltFuel SaltFluorideVolatilityFissionProductWasteMoF6, TcF6, SeF6,RuF5, TeF6, IF7,Other F6Molybdenum and Iodine for Medical Uses
49 Alternative LFTR/LCFR plan for spent nuclear fuel UO2 + F2 -> UF4Zr + F2 -> ZrF4(TRU)O2 + F2 -> PuF3,NpF4,AmF3, etc.(FP)O2 + F2 -> (FP)FSpent Nuclear Fuel from Light-Water ReactorsStep 1: Fluorinate it!Step 2: Use aluminum to remove the TRU-fluorides from the mix, leaving the fission productsRemove uranium as UF6, which is then either re-enriched or buried.Step 4: BURN TRU-chlorides in the fast-spectrum chloride reactor, destroying them (through fission) and forming new U-233 for fluoride reactors (LFTR).Step 5: Dispose of FP-fluorides in 300-yr disposal sites (not Yucca Mtn) and use U-233 from TRU destruction to start LFTRs that produce no further TRUs.Step 3: Chlorinate (with 37Cl) the metallic TRUs, forming fuel for the chloride reactor.
50 Cost advantages come from size and complexity reductions Low capital cost thru small facility and compact power conversionReactor operates at ambient pressureNo expanding gases (steam) to drive large containmentHigh-pressure helium gas turbine systemPrimary fuel (thorium) is inexpensiveSimple fuel cycle processing, all done on siteReduction in core size, complexity, fuel cost, and turbomachineryFluoride-cooled reactor with helium gas turbine power conversion systemGE Advanced Boiling Water Reactor (light-water reactor)
58 ConclusionsThorium is abundant, has incredible energy density, and can be utilized in thermal-spectrum reactorsWorld thorium energy supplies will last for tens of thousands of yearsSolid-fueled reactors have been disadvantaged in using thorium due to their inability to continuously reprocessFluid-fueled reactors, such as the liquid-fluoride reactor, offer the promise of complete consumption of thorium in energy generationThe world would be safer with thorium-fueled reactorsNot an avenue for weapons productionThe US should adopt a new “business model” for nuclear power for the country’s long term strategic needs
59 Learn more at: http://thoriumenergy. blogspot. com/ http://www
60 Executive Summary Liquid Fluoride Thorium Reactor (LFTR) A nuclear technology that was demonstrated successfully 40 years agoHighly energy efficient and able to completely utilize nuclear fuelIntrinsically safe due to the physicsMeltdown-proof and self-controllingRuns at 1 atmosphere pressureUse of fluid allows the burning of all fuel, thus no need for control rods, periodic solid fuel element replacement, etc.Produces orders of magnitude less waste than traditional light water reactors (LWR)Thorium reactor produces times less nuclear waste that a light water reactorWaste from LFTR need be stored for much less time than those from a LWRCurrent supply of nuclear waste can be burned down in the LFTR to waste products that need to be stored for much less timeNo transuranic element productionYucca Mountain not a requirement for long term waste storageCan use air or water for coolingCritical for arid areas such as the Western United StatesUnsuitable for nuclear weaponsThorium fuel supply is abundant and produces less mining waste than uraniumThorium four times as common in the Earth’s crust as uraniumCould provide the US electrical energy needs for hundreds to thousands of years and provide base power needed for non-electrical energy and resource productionCoal gasification, water desalinization, oil sands and oil shale processing, etc.