Presentation on theme: "Thorium and the Liquid-Fluoride Thorium Reactor Concept."— Presentation transcript:
Thorium and the Liquid-Fluoride Thorium Reactor Concept
World Energy Consumption is Rapidly Escalating Future Energy Consumption Has Been Significantly Underestimated In 2007, the world consumed*: 5.3 billion tonnes of coal (128 quads**) 31.1 billion barrels of oil (180 quads) 2.92 trillion m 3 of natural gas (105 quads) 65 million kg of uranium ore (25 quads) Contained 16,000 MT of thorium! **1 quad = 1 quadrillion BTU = 172 million barrels (Mbbl) of crude oil *Source: BP Statistical Review of World Energy quads of hydroelectricity Dominated by Hydrocarbons YearUSWorld ***Source: Energy Information Administration Outlook 2006 Total Energy Demand Projections (quads)*** In a global warming environment, where will the world turn for safe, abundant, low-cost energy?
The Binding Energy of Matter Electrons have binding energies of eVs. Nucleons (protons and neutrons) have binding energies of millions of eVs.
SupernovaBirth 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.
Fissile fuel has extraordinary energy density! 23 million kilowatt-hours per kilogram!
Energy Generation Comparison 6 kg of fissile material in a liquid-fluoride reactor has the energy equivalent (66,000 MW*hr electrical*) of: = 230 train cars (25,000 MT) of bituminous coal or, 600 train cars (66,000 MT) of brown coal, (Source: World Coal Institute)World Coal Institute or, 440 million cubic feet of natural gas (15% of a 125,000 cubic meter LNG tanker), or, 300 kg of enriched (3%) uranium in a pressurized water reactor. *Each ounce of thorium can therefore produce $14,000-24,000 of electricity (at $ /kW*hr)
Uranium-238 (99.3% of all U) Thorium-232 (100% of all Th) Uranium-235 (0.7% of all U) Uranium-233 Plutonium-239 Nature gave us three options for fissile fuel The fission of U-235 was discovered by Otto Hahn and Lise Meitner in Pu-239 as a fissile fuel was discovered by Glenn Seaborg in March U-233 as a fissile fuel was discovered by Seaborgs student John Gofman in February 1942.
Uranium-235 (highly enriched uranium) Could weapons be made from the fissile material? Isotope separation plant (Y-12) Natural uranium Hiroshima, 8/6/1945 Depleted uranium Isotope Production Reactor (Hanford) Pu separation from exposed U (PUREX) Trinity, 7/16/1945 Nagasaki, 8/9/1945 Thorium? Isotope Production Reactor uranium separation from exposed thorium PROBLEM: 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.
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. 232 U Uranium-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! 14 billion years to make this jump Some 232U starts decaying immediately 1.91 yr 3.64 d 55 sec 0.16 sec 1.91 yr 3.64 d 55 sec 1.91 yr 3.64 d
U-232 Formation in the Thorium Fuel Cycle
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 Fermis 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. Wigners protégé, Alvin Weinberg, followed Wigners path at the Oak Ridge National Lab.
Can Nuclear Reactions be Sustained in Natural Uranium? Not with thermal neutronsneed 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. SpectrumModerated Spectrum Spectrum Fast Thermal Start Reality Pu-240 Production Produces long- lived Actinides –Yucca Mtn Greater propensity to absorb neutrons Goal of fast breeder reactors Most of Pu burned Fast reactors keep neutrons here, but at a high price: –Safety –More fuel (5x)
Fission/Absorption Cross Sections
Neutrons are moderated through collisions Neutron born at high energy (1-2 MeV). Neutron moderated to thermal energy (<<1 eV).
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) buildup Disturbance to the fuel lattice caused by fission fragments and neutron flux As the fuel swells and distorts, it can cause the cladding around the fuel to rupture and release fission products into the coolant.
Lifetime of a Typical Uranium Fuel Element Conventional fuel elements are fabricated from uranium pellets and formed into fuel assemblies They 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.
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.
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.
Can Nuclear Reactions be Sustained in Natural Thorium? Yes! Enough neutrons to sustain reaction produced at thermal fission. Does not need fast neutron reactorsneeds neutronic efficiency. Thermal SpectrumModerated Spectrum Spectrum Fast No Advantage for Thorium U-234 U-232 contaminates U-233 and cannot be removed –Prevents U-233 being used as weapon Start
Thorium-Uranium Breeding Cycle Uranium-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 Th-233 Pa-233 U-233 Thorium-233 decays quickly (half-life of 22.3 min) to protactinium- 233 by emitting a beta particle (an electron). Protactinium-233 decays more slowly (half-life of 27 days) to uranium-233 by emitting a beta particle (an electron). It is important that Pa-233 NOT absorb a neutron before it decays to U-233it should be isolated from any neutrons until it decays.
1944: A tale of two isotopes… But Eugene, how will you reprocess the thorium fuel effectively? Well build a fluid-fueled reactor, thats how…
ORNL Fluid-Fueled Thorium Reactor Progress ( ) 1947 – Eugene Wigner proposes a fluid-fueled thorium reactor 1950 – Alvin Weinberg becomes ORNL director 1952 – Homogeneous Reactor Experiment (HRE-1) built and operated successfully (100 kWe, 550K) 1958 – Homogeneous Reactor Experiment-2 proposed with 5 MW of power 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.
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 efficiency 3X higher than sub reactors Lightweight design Compact core for minimal shielding Low-pressure operation Ease of operability Inherent safety and control Easily removeable
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.
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 11/12/54 Liquid-fluoride salt circulated through beryllium reflector in Inconel tubes 235 UF 4 dissolved in NaF-ZrF 4 Produced 2.5 MW of thermal power Gaseous fission products were removed naturally through pumping action Very stable operation due to high negative reactivity coefficient Demonstrated load-following operation without control rods
It wasnt 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 Aircraft Nuclear Program allowed ORNL to develop reactors
ORNL Aircraft Nuclear Reactor Progress ( ) 1949 – Nuclear Aircraft Concept formulated 1951 – R.C. Briant proposed Liquid- Fluoride Reactor 1952, 1953 – Early designs for aircraft fluoride reactor 1954 – Aircraft Reactor Experiment (ARE) built and operated successfully (2500 kWt, 1150K) 1955 – 60 MWt Aircraft Reactor Test (ART, Fireball) proposed for aircraft reactor 1960 – Nuclear Aircraft Program cancelled in favor of ICBMs
Fluid-Fueled Reactors for Thorium Energy Uranium tetrafluoride dissolved in lithium fluoride/beryllium fluoride. Thorium dissolved as a tetrafluoride. Two built and operated. Aqueous Homogenous Reactor (ORNL) Liquid-Fluoride Reactor (ORNL) Liquid-Metal Fuel Reactor (BNL) 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. Conceptualnone built and operated.
Molten Salt Reactor Experiment ( )
LFTR is totally passively safe in case of accident In 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. The reactor is equipped with a freeze plugan open line where a frozen plug of salt is blocking the flow. The plug is kept frozen by an external cooling fan. Freeze Plug Drain Tank
A Modern Fluoride Reactor
LFTR produces far less mining waste than LWR ( ~4000:1 ratio) Mining 800,000 MT of ore containing 0.2% uranium (260 MT U) Uranium fuel cycle calculations done using WISE nuclear fuel material calculator: Generates ~600,000 MT of waste rock Conversion to natural UF 6 (247 MT U) Generates 170 MT of solid waste and 1600 m 3 of liquid waste Milling and processing to yellowcakenatural U 3 O 8 (248 MT U) Generates 130,000 MT of mill tailings Mining 200 MT of ore containing 0.5% thorium (1 MT Th) Generates ~199 MT of waste rock Milling and processing to thorium nitrate ThNO 3 (1 MT Th) Generates 0.1 MT of mill tailings and 50 kg of aqueous wastes 1 GW*yr of electricity from a uranium-fueled light-water reactor 1 GW*yr of electricity from a thorium-fueled liquid-fluoride reactor
LFTR produces less operational waste than LWR, (mission: make 1000 MW of electricity for one year) 250 t of natural uranium containing 1.75 t U t of enriched uranium (1.15 t U-235) 215 t of depleted uranium containing 0.6 t U-235 disposal plans uncertain. Uranium-235 content is burned out of the fuel; some plutonium is formed and burned 35 t of spent fuel stored on-site until disposal at Yucca Mountain. It contains: 33.4 t uranium t uranium t plutonium 1.0 t fission products. One tonne of natural thorium Thorium introduced into blanket of fluoride reactor; completely converted to uranium-233 and burned. One tonne of fission products; no uranium, plutonium, or other actinides. Within 10 years, 83% of fission products are stable and can be partitioned and sold. The remaining 17% fission products go to geologic isolation for ~300 years.
Thorium Fuel Supply Thorium is abundant around the world and rich in energy Estimated world reserve base of 1.4 million MT US has about 20% of the world reserve base A single mine site in Idaho could produce 4500 MT of thorium/year US currently would use about 400 MT/year for electricity production The United States has buried 3200 metric tons of thorium nitrate in the Nevada desert. World Thorium Resources Country Australia India USA Norway Canada South Africa Brazil Other countries World total Reserve Base (tons) 340, , , ,000 39,000 18, ,000 1,400,000 Source: U.S. Geological Survey, Mineral Commodity Summaries, January 2008
A single mine site in Idaho could recover 4500 MT of thorium per year
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.
Thorium Resources in the United States Lemhi Pass, Idaho (best mining site in US) 3200 metric tonnes of thorium nitrate buried at Nevada Test Site Conway Shale, NH Monazite beach sands in Georgia and Florida
LFTR could produce many valuable by-products Liquid- Fluoride Thorium Reactor Desalination to Potable Water Facilities Heating These products may be as important as electricity production Thorium Separated Fission Products Strontium-90 for radioisotope power Cesium-137 for medical sterilization Rhodium, Ruthenium as stable rare-earths Technetium-99 as catalyst Molybdenum-99 for medical diagnostics Iodine-131 for cancer treatment Xenon for ion engines Electrical Generation (50% efficiency) Low-temp Waste Heat Power Conversion Electrical load Electrolytic H2 Process Heat Coal-Syn-Fuel Conversion Thermo-chemical H2 Oil shale/tar sands extraction Crude oil cracking Hydrogen fuel cell Ammonia (NH 3 ) Generation Fertilizer for Agriculture Automotive Fuel Cell (very simple)
The byproducts of conventional reactors are more limited Light-Water Reactor Uranium Electrical Generation (35% efficiency) Low-temp Waste Heat Power Conversion Electrical load Electrolytic H2 Crude oil cracking Hydrogen fuel cell Ammonia (NH 3 ) Generation Fertilizer for Agriculture Automotive Fuel Cell (very simple)
LFTR can be environmentally friendly Open Pit Mine Nuclear Waste Large Cooling Towers Concern about waste disposal has hampered nuclear industry growth – and energy supply Does not produce green house gases Can be air-cooled Consequently does not vent heat into rivers and lakes Smaller cooling towers Little operations waste Option of retaining waste storage on site Operational waste products decay very rapidly Little mining waste No large open pits, large waste mountains
Why wasnt 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. Alvin Weinberg: 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.
No pressure vessel required Liquid fuel requires no expensive fuel fabrication and qualification Smaller power conversion system No steam generators required Factory built-modular construction Scalable: 100 KW to multi GW Smaller containment building needed Steam vs. fluids Simpler operation No operational control rods No re-fueling shut down Significantly lower maintenance Significantly smaller staff Significantly lower capital costs Lower regulatory burden LFTR could cost much less than LWR
The Current Plan is to Dispose Fuel in Yucca Mountain
Tunnels in Yucca Mountain
Capacity based on limited exploration Legislated capacity 6-Lab Strategy MIT Study EIA 1.5% Growth Constant 100 GWe Secretarial recommendation Projected Spent Fuel Accumulation without Reprocessing
How does a fluoride reactor use thorium? Fluoride Volatility Vacuum Distillation Uranium Absorption- Reduction 233,234 UF 6 7 LiF-BeF 2 -UF UF 6 Fission Product Waste Hexafluoride Distillation Fluoride Volatility 7LiF-BeF 2 Bare Salt Pa-233 Decay Tank Metallic thorium MoF 6, TcF 6, SeF 6, RuF 5, TeF 6, IF 7, Other F 6 Fuel Salt xF 6 238U Core Blanket Two-Fluid Reactor Bismuth-metal Reductive Extraction Column Molybdenum and Iodine for Medical Uses Fertile Salt Recycle Fertile Salt Recycle Fuel Salt Pa
Alternative LFTR/LCFR plan for spent nuclear fuel Spent Nuclear Fuel from Light-Water Reactors Step 1: Fluorinate it! Remove uranium as UF6, which is then either re- enriched or buried. UO2 + F2 -> UF4 Zr + F2 -> ZrF4 (TRU)O2 + F2 -> PuF3,NpF4,AmF3, etc. (FP)O2 + F2 -> (FP)F Step 2: Use aluminum to remove the TRU-fluorides from the mix, leaving the fission products Step 3: Chlorinate (with 37Cl) the metallic TRUs, forming fuel for the chloride reactor. 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.
Cost Low capital cost thru small facility and compact power conversion Reactor operates at ambient pressure No expanding gases (steam) to drive large containment High-pressure helium gas turbine system Primary fuel (thorium) is inexpensive Simple fuel cycle processing, all done on site Cost advantages come from size and complexity reductions GE Advanced Boiling Water Reactor (light-water reactor) Fluoride-cooled reactor with helium gas turbine power conversion system Reduction in core size, complexity, fuel cost, and turbomachinery
Examples of Mobile Nuclear Reactors
Coastal Populations in US
Coastal Populations in Asia
Gentlemen, our mission…
Underwater Nuclear Powerplants?
Conclusions Thorium is abundant, has incredible energy density, and can be utilized in thermal-spectrum reactors World thorium energy supplies will last for tens of thousands of years Solid-fueled reactors have been disadvantaged in using thorium due to their inability to continuously reprocess Fluid-fueled reactors, such as the liquid-fluoride reactor, offer the promise of complete consumption of thorium in energy generation The world would be safer with thorium-fueled reactors Not an avenue for weapons production The US should adopt a new business model for nuclear power for the countrys long term strategic needs
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Executive Summary Liquid Fluoride Thorium Reactor (LFTR) A nuclear technology that was demonstrated successfully 40 years ago Highly energy efficient and able to completely utilize nuclear fuel Intrinsically safe due to the physics Meltdown-proof and self-controlling Runs at 1 atmosphere pressure Use 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 reactor Waste from LFTR need be stored for much less time than those from a LWR Current supply of nuclear waste can be burned down in the LFTR to waste products that need to be stored for much less time No transuranic element production Yucca Mountain not a requirement for long term waste storage Can use air or water for cooling Critical for arid areas such as the Western United States Unsuitable for nuclear weapons Thorium fuel supply is abundant and produces less mining waste than uranium Thorium four times as common in the Earths crust as uranium Could provide the US electrical energy needs for hundreds to thousands of years and provide base power needed for non-electrical energy and resource production Coal gasification, water desalinization, oil sands and oil shale processing, etc.