|• Kirk F. Sorensen
President and Chief Technologist
• Board of Advisers
Flibe Energy was founded on April 6, 2011 by Kirk Sorensen, former NASA aerospace engineer and formerly chief nuclear technologist at Teledyne Brown Engineering, and Kirk Dorius, an intellectual property attorney and mechanical engineer. The name "Flibe" comes from FLiBe, a Fluoride salt of Lithium and Beryllium, used in LFTRs. Flibe Energy Incorporated is registered in the State of Delaware. Their advertising slogan is "LFTR by Flibe Energy, powering the next thousand years"
Small modular reactor design
Presenting at the October 2011 Thorium Energy Conference, Sorensen described how various factors influence design for small modular reactors.
- U-235 and Th-232/U-233 work most efficiently with thermal spectrum neutrons (<1 eV)
- U-238/Pu-239 requires fast spectrum neutrons (>100,000 eV) to sustain breeding
Operating temperature ("Moderate" defined as 250-350 °C versus "High" defined as 700-1000 °C) and pressure ("Atmospheric" versus "High") is related to coolant type; there are four, one for each temperature/pressure combination:
- Water: Moderate Temperature, High Pressure (e.g. B&W mPower, NuScale, Westinghouse, IRIS, KLT-40S)
- Gas: High Temperature, High Pressure (e.g. PBMR, GT-MHR, EM2)
- Liquid Metal: Moderate Temperature, Atmospheric Pressure (e.g. Hyperion, Toshiba 4S, GE PRISM)
- Liquid Salt: High Temperature, Atmospheric Pressure (e.g. LFTR)
Various conclusions about the three fuels and possible reactor types were then drawn:
Some perceive U-235 as a finite and scarce resource, but the Earth's crust likely contains 40 trillion tons of it. Nonetheless, this reactor model plans to exploit a fuel 4 times as abundant: Thorium. Gas-based concepts (e.g. PBMR, VHTR, GT-MHR) are also feasible.
The liquid metal coolants used are poor neutron moderators, thus such systems strongly favor U-238/Pu-239 usage; adding moderators to enable use with U-235 or Th-232/U-233 would be "feasible but unattractive". Conversely, water is a good moderator and this rules out exclusive plutonium breeding in such systems. Gas-cooled systems with U-238/Pu-239 (Gas Cooled Fast Breeder Reactor (GCFR) and EM2 concepts) are described as feasible but with difficult fuel processing, while molten salt systems with U-238/Pu-239 (e.g. MSFR) are only "somewhat feasible."
Sorensen notes that while solid Th-232/U-233 was used in a water-cooled reactor at the Shippingport Atomic Power Station and a gas-cooled reactor at the Fort St. Vrain Generating Station, thorium dioxide fuel is "very difficult to process," making Th-232/U-233 unattractive for all systems except liquid salt, e.g. where thorium and uranium fluorides are used instead.
In summary, the LFTR thus combines the desirable characteristics of abundant fuel supply, high operating temperature, atmospheric operating pressure and simple fuel processing.
Flibe Energy reactor
|Liquid-Fluoride Thorium Reactor (LFTR)|
|Generation||Generation IV reactor|
|Reactor concept||Thorium-232 fueled, graphite moderated, FLiBe molten salt reactor (MSR)|
|Concept by||Flibe Energy|
|Main parameters of the reactor core|
|Fuel (fissile material)||233U|
|Fuel state||Liquid (FLiBe molten salt)|
|Neutron energy spectrum||Thermal|
|Primary control method||Negative temperature coefficient|
|Primary coolant||Liquid (FLiBe molten salt)|
|Primary use||Generation of electricity|
Low pressure, high temperature molten salt reactor
- FLiBe fuel & coolant salt 
- 600 MWth reactor, 250 MWe net electricity output 
- Supercritical CO2 Brayton cycle power conversion system 
- Two fluid reactor, graphite moderated, Hastelloy-N construction 
- Passive nuclear safety features 
- Fail safe freeze valve and drain tank
- Negative temperature coefficient - As demonstrated by an accident at MSRE, a "run away" reaction inherently stops far (several hundred °C) below the melting temperature of the structure/pipes/pumps/valves.
- The fuel being dissolved in FLiBe makes curtailment of fission easy. Any mechanism (including damage) which drains the FLiBe away from the reactor core will leave the (solid) graphite moderator behind, hence the fuel no longer capable of sustaining fission. Even an overheated reactor would remain far (several hundred °C) cooler than the melting temperature of the graphite moderator or reactor chamber.
- Control rods - also actively actuatable
- Primary & intermediate salt loop heat exchangers 
- Chemical processing - Move uranium from blanket to fuel salt and remove fission products 
- Off-gas handling for Xe,Kr, tritium 
In the 12 May 2011 "Introduction to Flibe Energy" with Sorensen and Dorius, an interview of Sorensen from 28 May 2011 and another from 14 July 2011[unreliable source], the creation of LFTRs was discussed.
"The real challenge will be getting to the first unit." — Kirk Sorensen
Besides the safety aspect (mentioned above) of a LFTR operating at far less pressure than a typical nuclear reactor, Sorensen expects it to reduce costs: "That obviates the need for 9 inch steel pressure vessels, and thick concrete containment structures. Everything gets smaller with Thorium and fluoride salts, and that provides a substantial economic benefit."[unreliable source] However, there are existing reactors that operate at a lower pressure than PWRs. Every other reactor design other than the PWR has lower pressure, including BWRs, CANDUs, RBMKS, GCRs, FBRs, etc...
In a February 2011 interview with Kiki Sanford (two months prior to the founding of Flibe Energy) Sorensen estimated that the production cost of a LFTR (i.e. once research and development has finished), would be on the order of $1–2 per watt, making it competitive with the construction costs of natural gas plants.[unreliable source]
At its most basic level, the function of a LFTR is to act as a source of thermal energy (colloquially: heat). The ability to harness this energy for useful and interesting work is only limited by the laws of thermodynamics and the imagination. Specific examples of other LFTR applications cited by Sorensen:
- Desalination, the conversion of salt water into fresh water, using the waste heat from electricity generation
- District heating using the waste heat from electricity generation[unreliable source]
- Hydrogen production by water splitting
- Artificial fixation of nitrogen for fertilizer.[not in citation given][unreliable source]
- Carbon-neutral synthetic fuel production
In order to achieve its goals, Flibe Energy intends to work with the US Armed Services, which have an independent nuclear regulatory authority. Accelerated military development and demonstration can speed later deployment for civilian power production by providing extended materials and operational data to inform civilian reactor licensing through the Nuclear Regulatory Commission (NRC). Many domestic military installations are dependent on surrounding vulnerable local power grids and the US Army would like its bases to have self-sufficient power generation capability (described as "base islanding"), which a LFTR could provide. Presenting at the Thorium Energy Conference on 10 October 2011, Sorensen further described how the US military needs a "remote source of power" in the form of "small rugged reactors" (SRR) "capable of operating in dangerous and remote areas" and how Flibe Energy is initially developing a "SRR LFTR" to meet that need, as it would be portable and easy to assemble/disassemble, obviating vulnerable refueling convoys.
Four specific difficulties have been mentioned:
- Salts can be corrosive to materials. However Hastelloy-N, was used in the MSRE and proved compatible with the fluoride salts FLiBe and FLiNaK.
- Designing for high-temperature operation is more difficult
- There has been little innovation in the field for several decades
- The differences between LFTRs and the light water reactors in majority use today are vast; the former "is not yet fully understood by regulatory agencies and officials." (note NRC mention above)
In addition, this reactor may require parts different from existing reactors, making them more expensive.
One question that has been raised is where the required large quantities of Lithium will come from.
Flibe Energy co-founder Kirk Sorensen has a bachelor's degree in mechanical engineering from Utah State University, a master's degree in aerospace engineering from the Georgia Institute of Technology, and a master's degree in nuclear engineering from the University of Tennessee. He worked at NASA's Marshall Space Flight Center from 2000 to 2010, followed by a year at Teledyne Brown Engineering in Huntsville, Alabama as Chief Nuclear Technologist until he left to found Flibe Energy in 2011.
Sorensen was written about in the book SuperFuel and appears in the documentaries Thorium Remix 2011, The Thorium Dream as well as being credited in the upcoming "film about thorium" titled The Good Reactor.
- Flibe Energy company website
- September 27, 2011 – New Huntsville company to build thorium-based nuclear reactors, Huntsville Newswire
- "Don't count out nuclear just yet". CNN.
- .Energy from Thorium, LFTR Technology by Flibe Energy
- Presenting at ThEC2011 and powerpoint file of slides Archived October 16, 2011, at the Wayback Machine.
- Note Neutron Yield per Neutron Absorbed graph from MIT OpenCourseWare; to sustain breeding, at least two neutrons (red line) must be released per neutron absorbed.
- Westinghouse SMR
- Westinghouse announces Small Modular Reactor
- "Program on Technology Innovation: Technology Assessment of a Molten Salt Reactor Design - The Liquid-Fluoride Thorium Reactor (LFTR)". EPRI. 22 October 2015. Retrieved 10 March 2016.
- EPRI, 2015, 2-1.
- EPRI, 2015, 2-2.
- EPRI, 2015, 3-8.
- EPRI, 2015, 3-30.
- EPRI, 2015, 3-9 & 10.
- EPRI, 2015, 3-11.
- EPRI, 2015, 3-12.
- Introduction to Flibe Energy: YouTube Video (~20 min) and PDF of slides used
- Kirk Sorensen: Thorium Could Be Our Energy "Silver Bullet" MP3 (first 38 min)
- Could Thorium solve the world's energy problems?
- International Energy Outlook 2011 (Released September 19, 2011) Note: "does not incorporate prospective legislation or policies that might affect energy markets" and excludes Fukushima Daiichi nuclear disaster impacts.
- Dr. Robert Hargraves, who is on Flibe Energy's Board of Advisers, lays out a strategy in "Aim High!" (Video:  and PDF: ) where factory mass production of 100 MW modular LFTR reactors produce one a day at 200 million dollars each. This approach enables incremental capital outlays, affordability to developing nations and truck transport to the plant site.
- Dr. Kiki's Science Hour 84: The Nuclear Alternative (note cost discussion starting ~29:20)
- TEDxYYC - Kirk Sorensen - Thorium (Calgary, AB, Canada April 1st, 2011)
- Flibe Energy Announces Board of Advisors
- Nuclear Ammonia "This article is derived from a presentation by Robert Hargraves, Darryl Siemer, and Kirk Sorensen, entitled Nuclear Ammonia: Thorium’s Killer App, presented October 11, 2011, at the iTheo annual meeting at City College of New York."
- Waldrop, M. M. (2012). "Nuclear energy: Radical reactors". Nature. 492 (7427): 26–29. PMID 23222589. doi:10.1038/492026a. "The company is developing a 40-megawatt reactor that might be used on military bases so that they can operate independently of the grid."
- Sorensen has cited the loss of power to the Redstone Arsenal near Huntsville following the April 25–28, 2011 tornado outbreak () as an example.
- Note also Army Energy Program: Vision for Net Zero "The Army's vision is to appropriately manage our natural resources with a goal of net zero installations. Today the Army faces significant threats to our energy and water supply requirements both home and abroad. Addressing energy security and sustainability is operationally necessary, financially prudent, and essential to mission accomplishment."
- DeVan, Jackson H. "EFFECT OF ALLOYING ADDITIONS ON CORROSION BEHAVIOR OF NICKEL - MOLYBDENUM ALLOYS IN FUSED FLUORIDE MIXTURES." Thesis. University of Tennessee, 1960. Web. <http://moltensalt.net/references/static/downloads/pdf/ORNL-TM-0202.pdf>.
- Sorensen, Kirk. "Blogger: User Profile: Kirk Sorensen". Kirk Sorensen. Retrieved 11 March 2015.
- "Our Company". Flibe Energy. Retrieved 11 March 2015.
- Sorensen, Kirk. "Thorium Research in the Manhattan Project Era". University of Tennessee. Retrieved 11 March 2015.
- Doug Caruso (7 March 2010). "The mighty thorium". The Columbus Dispatch. Retrieved 26 October 2011.
- Manchester Report: Thorium nuclear power
- Uranium Is So Last Century — Enter Thorium, the New Green Nuke
- SuperFuel: Thorium, the Green Energy Source for the Future at Google Books. ISBN 9780230341913
- THORIUM REMIX 2011
- Thorium Remix 2011 on Internet Movie Database
- Motherboard TV: The Thorium Dream (November, 2011)
- Thorium: World's greatest energy breakthrough? (CNN.com)
- Motherboard TV: The Thorium Dream (YouTube video)
- Cast | The Good Reactor
- Flibe Energy (company website)
- Interview with Kirk Sorensen and Kirk Dorius by Peter Schiff (MP3 starting 1:00) January 2012.
- on YouTube. Sorensen representing Flibe Energy at the Global New Energy Summit; Interview with ICOSA Magazine. April 2012.
- on YouTube. Sorensen and Bryony Worthington, Baroness Worthington discuss "the progress and advantages of thorium technology". Interview with ICOSA Magazine. June 2012.
- on YouTube. Sorensen representing Flibe Energy at the 2013 Thorium Energy Conference. October 2013.