Thorium and the Liquid-Fluoride Thorium Reactor Concept

1. Thorium and the Liquid-Fluoride Thorium Reactor Concept

2. World Energy Consumption is Rapidly EscalatingFuture Energy Consumption Has Been Significantly Underestimated In 2007, the world consumed*: 5.3 billion tonnes of coal (128 quads**) 2.92 trillion m3 of natural gas (105 quads) 31.1 billion barrels of oil (180 quads) Contained 16,000 MT of thorium! Dominated by Hydrocarbons 65 million kg of uranium ore (25 quads) Total Energy Demand Projections (quads)*** 29 quads of hydroelectricity In 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 $0.04-0.07/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-239 U-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 uranium Isotope separation plant (Y-12) Hiroshima, 8/6/1945 Depleted uranium Isotope Production Reactor (Hanford) Pu separation from exposed U (PUREX) Trinity, 7/16/1945 Nagasaki, 8/9/1945 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. Isotope Production Reactor uranium separation from exposed thorium Thorium?

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. 232U 14 billion years to make this jump Some 232U starts decaying immediately 1.91 yr 1.91 yr 1.91 yr 3.64 d 3.64 d 3.64 d 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! 55 sec 55 sec 0.16 sec

10. U-232 Formation in the Thorium Fuel Cycle

11. 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. 1944: A tale of two isotopes…

12. Can Nuclear Reactions be Sustained in Natural Uranium? • Goal of fast breeder reactors • Most of Pu burned • Fast reactors keep neutrons here, but at a high price: • Safety • More fuel (5x) Fast Reality Thermal Spectrum Moderated Spectrum Spectrum Pu-240 Production • Produces long-lived Actinides • Yucca Mtn Greater propensity to absorb neutrons Start Not 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.

13. Fission/Absorption Cross Sections

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) 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.

16. 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.

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? Fast Thermal Spectrum Moderated Spectrum Spectrum U-234 No Advantage for Thorium • U-232 contaminates U-233 and cannot be removed • Prevents U-233 being used as weapon Start Yes! 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-233 Th-233 U-233 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. 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 reactor 1950 – Alvin Weinberg becomes ORNL director 1952 – 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 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

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 11/12/54 • Liquid-fluoride salt circulated through beryllium reflector in Inconel tubes • 235UF4 dissolved in NaF-ZrF4 • 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

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 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

28. 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. Fluid-Fueled Reactors for Thorium Energy Liquid-Fluoride Reactor (ORNL) Aqueous Homogenous Reactor (ORNL) Liquid-Metal Fuel Reactor (BNL) • Uranium metal dissolved in bismuth metal. • Thorium oxide in a slurry. • Conceptual—none built and operated.

29. Molten Salt Reactor Experiment (1965-1969)

30. 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 plug”—an open line where a frozen plug of salt is blocking the flow. The plug is kept frozen by an external cooling fan. LFTR is totally passively safe in case of accident Freeze Plug Drain Tank

31. A “Modern” Fluoride Reactor

32. LFTR produces far less mining waste than LWR( ~4000:1 ratio) 1 GW*yr of electricity from a uranium-fueled light-water reactor Conversion 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 waste Generates ~600,000 MT of waste rock Generates 130,000 MT of mill tailings 1 GW*yr of electricity from a thorium-fueled liquid-fluoride reactor Mining 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 wastes Generates ~199 MT of waste rock Uranium fuel cycle calculations done using WISE nuclear fuel material calculator: http://www.wise-uranium.org/nfcm.html

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 burned • 35 t of spent fuel stored on-site until disposal at Yucca Mountain. It contains: • 33.4 t uranium-238 • 0.3 t uranium-235 • 0.3 t plutonium • 1.0 t fission products. 250 t of natural uranium containing 1.75 t U-235 215 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 thorium One 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 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 World Thorium Resources Country Australia India USA Norway Canada South Africa Brazil Other countries World total Reserve Base (tons) 340,000 300,000 300,000 180,000 100,000 39,000 18,000 100,000 1,400,000 Source: U.S. Geological Survey, Mineral Commodity Summaries, January 2008 The 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 Site Lemhi Pass, Idaho (best mining site in US) Conway Shale, NH 3 16 14 1 15 13 17 18 11 4 5 6 10 9 7 8 Monazite beach sands in Georgia and Florida

38. LFTR could produce many valuable by-products Thorium Desalination to Potable Water Facilities Heating Low-temp Waste Heat Liquid-Fluoride Thorium Reactor Power Conversion Electrical Generation (50% efficiency) Electrical load Electrolytic H2 Process Heat Coal-Syn-Fuel Conversion Thermo-chemical H2 Oil shale/tar sands extraction Separated Fission Products Crude oil “cracking” Hydrogen fuel cell Ammonia (NH3) Generation 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 Fertilizer for Agriculture Automotive Fuel Cell (very simple) These products may be as important as electricity production

39. The byproducts of conventional reactors are more limited Uranium Low-temp Waste Heat Light-Water Reactor Power Conversion Electrical Generation (35% efficiency) Electrical load Electrolytic H2 Crude oil “cracking” Hydrogen fuel cell Ammonia (NH3) Generation Fertilizer for Agriculture Automotive Fuel Cell (very simple)

40. LFTR can be environmentally friendly 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” Large Cooling Towers Nuclear Waste Concern about waste disposal has hampered nuclear industry growth – and energy supply Open 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. 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.”

42. LFTR could cost much less than LWR • 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

43. The Current Plan is to Dispose Fuel in Yucca Mountain

44. Tunnels in Yucca Mountain

45. Projected Spent Fuel Accumulation without Reprocessing EIA 1.5% Growth MIT Study 6-Lab Strategy Capacity based on limited exploration Legislated capacity Constant 100 GWe Secretarial recommendation

46. DOE Plan (“GNEP”) for Spent Nuclear Fuel

47. Uranium-Plutonium Fuel Cycle Uranium Refining Depleted UF6 ~0.2% U-235 Uranium Ore Natural UF6 Uranium Mining Uranium Milling Uranium Purification Natural Uranium Purification Uranium Enrichment Depleted UF6 Stockpile Uranium Concentrates Uranyl Nitrate Natural UO2 or U-metal Recycled UF6 Enriched UF6 ~3% U-235 Electricity Aged Converter Fuel Irradiated Fuel Fuel Assemblies Enriched UO2 Converter Fuel Reprocessing Irradiated Fuel Storage Converter Reactor Fuel Fabrication Conversion to UO2 Converter High-Level Waste Mixed Oxides (Pu,U)O2 ~5% Pu Recycled Mixed PuO2-UO3 High-Level Waste Permanent Waste Storage Interim Waste Storage PuO2-UO3 Stockpile PuO2-UO3 Conversion To (Pu,U)O2 Recycled Mixed PuO2-UO3 Mixed Oxides (Pu,U)O2 ~20% Pu Breeder High-Level Waste Electricity Aged Breeder Fuel Breeder Fuel Assemblies Irradiated Fuel Depleted UO2 Depleted UF6 Breeder Fuel Reprocessing Irradiated Fuel Storage Fast Breeder Reactor Breeder Fuel Fabrication Conversion to UO2 Recycled Depleted UO3

48. How does a fluoride reactor use thorium? Metallic thorium Pa-233 Decay Tank 238U Fertile Salt Bismuth-metal Reductive Extraction Column Fluoride Volatility Pa 233UF6 Recycle Fertile Salt Uranium Absorption- Reduction Core 7LiF-BeF2 Recycle Fuel Salt 7LiF-BeF2-UF4 Blanket 233,234UF6 Vacuum Distillation Hexafluoride Distillation Two-Fluid Reactor xF6 “Bare” Salt Fuel Salt Fluoride Volatility Fission Product Waste MoF6, TcF6, SeF6, RuF5, TeF6, IF7, Other F6 Molybdenum and Iodine for Medical Uses

49. Alternative LFTR/LCFR plan for spent nuclear fuel UO2 + F2 -> UF4 Zr + F2 -> ZrF4 (TRU)O2 + F2 -> PuF3,NpF4,AmF3, etc. (FP)O2 + F2 -> (FP)F Spent Nuclear Fuel from Light-Water Reactors Step 1: Fluorinate it! Step 2: Use aluminum to remove the TRU-fluorides from the mix, leaving the fission products Remove 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 • 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 Reduction in core size, complexity, fuel cost, and turbomachinery Fluoride-cooled reactor with helium gas turbine power conversion system GE Advanced Boiling Water Reactor (light-water reactor)