Energy Security and the Potential for Thorium Kirk Sorensen Pacific Operational Science and Technology Conference March 21, 2012

Worldwide Need for Electricity and Water We need much more energy at much lower prices… …with much less impact on the Earth’s environment.

Today’s Non-Solutions Expensive, intermittent, alternative energy isn’t the solution. Most people on Earth can’t afford unsubsidized alternative energy. Cheap and reliable, but dirty energy isn’t a viable solution either. Most people have no better alternatives.

Thorium is the Solution Natural, abundant and inexpensive thorium is the solution. Thorium energy can be inexpensive and clean if made by a liquid-fluoride thorium reactor (LFTR). With thorium, you can hold a lifetime’s supply of energy in the palm of your hand. It would cost a few cents.

Weinberg’s Vision for our Energy Future Alvin Weinberg had a vision for our energy future. It would be clean and sustainable. As director of the Oak Ridge National Lab from 1955 to 1972 he and his technical team made remarkable progress on this vision.

Jet Propulsion Drove To High-Temperatures

Aircraft Nuclear Program pushed the state-of-the-art 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 naval gas turbine.  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 removable

Nuclear-Heated Gas Turbine Propulsion  Convair B-36 X-6  Four nuclear-powered turbojets  200 MW thermal reactor Liquid-Fluoride Reactor

The Aircraft Reactor Experiment (ARE)  “Proof-of-concept” fluoride reactor  Operated from November 3-12, 1954  Achieved 1150 K outlet temperature.  Produced 2.5 MW of thermal power  NaF-ZrF UF4 circulated through beryllium reflector in Inconel tubes  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

Molten Salt Reactor Experiment ( )

Weinberg’s vision of the future was based on thorium and liquid- fueled reactors. These reactors would make electricity and produce fresh water from the ocean.

But Weinberg’s vision and research stalled in 1974 when the United States ceased funding thorium efforts in favor of a plutonium fast breeder reactor.

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 Seaborg’s student John Gofman in February 1942.

An Introduction to the Thorium Fuel Cycle

Fluoride Salts are the Key to Thorium LiF:BeF 2 3LiF:BeF 2 chemically stable in air and water Unpressurized liquid with 1000°C range of temperature

The turbine drives a generator creating electricity Hot fuel salt The gas is cooled and the waste heat is used to desalinate seawater Hot coolant salt Warm coolant salt Warm fuel salt Hot gas Warm gas Salt / Salt Heat Exchanger Salt / Gas Heat Exchanger Turbine Compressor How does a fluoride reactor make electricity? Reactor containment boundary

Fluoride Reactors can be Inherently Safe  The liquid-fluoride thorium reactor is incredibly stable against nuclear reactivity accidents.  It is simply not possible because any change in operating conditions results in a reduction in reactor power.  The LFTR is also totally, passively safe against loss-of- coolant accidents.  It is simply not possible because in all cases the fuel drains into a passively safe configuration.

LFTR is 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 and meltdown are not possible.  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 Plug Drain Tank

Liquid Salt Liquid MetalWater Gas Coolant Choices for a Nuclear Reactor Moderate Temperature ( C) High Temperature ( C) Atmospheric- Pressure Operation High-Pressure Operation Pressure Coolant Temperature

Potential PCS Efficiencies of LWR and LFTR Typical light- water reactor Liquid-fluoride reactor H2O critical temp U-FLiBe melting temp ~47% efficiency ~33% efficiency

Reactor in underground silo? Immersed in water for seismic isolation and decay heat removal? Hardened against air impacts? Truck transportable? Compact gas turbines for power generation?

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.

natural uranium centrifuge or laser enrichment highly enriched uranium Option 1: Enriching Uranium for Weapons

Option 2: Producing Plutonium for Weapons natural uranium thermal reactor (limited exposure) or fast reactor weapons-grade plutonium

natural thorium reactor U-233 Option 3: Producing U-233 for Weapons?

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

Thorium is a common mineral in the US and world

Uranium (PWR/BWR) vs. Thorium (LFTR) comparison: production of 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; contains: 33.4 t uranium t uranium t plutonium 1.0 t fission products. And lasts ~10,000+ years 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.

 Hydrogen demand is already large and growing rapidly  Heavy-oil refining consumes 5% of natural gas for hydrogen production  Energy security and environmental quality motivate hydrogen as an alternative to oil as a transportation fuel  Zero-emissions  Distributed energy opportunity  Water is the preferred hydrogen “fuel”  Electrolysis using off- peak power  High-temperature electrolysis  High-temperature thermochemical water splitting High-Temperature Hydrogen Production

Medical Radioisotopes from LFTR Bismuth-213 (derived from U-233 decay) Molybdenum-99 (derived from U-233 fission)

Conventional uranium reactors only make electricity Light-Water Reactor Uranium Electrical Generation (35% efficiency) Power Conversion Electrical load

But LFTR can 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 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)

Conclusions  Thorium has innate advantages as a fuel material that are worthy of deep and thorough investigation.  The liquid-fluoride reactor offers the promise of complete consumption of thorium in energy generation, minimizing waste.  The compact nature of the liquid-fluoride reactor, when coupled to a closed-cycle gas turbine system, might allow simplified deployment scenarios.