Flibe Energy

Flibe Energy
Industry Nuclear power
Headquarters Huntsville, Alabama
Key people
Kirk F. Sorensen
President and Chief Technologist
Board of Advisers
Website flibe-energy.com

Flibe Energy is an American company that intends to design, construct, and operate small modular reactors based on liquid fluoride thorium reactor (acronym LFTR; pronounced lifter) technology.


Molten FLiBe salt

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.[1][2][3] Their advertising slogan is "LFTR by Flibe Energy, powering the next thousand years"[4]

Small modular reactor design

Presenting at the October 2011 Thorium Energy Conference, Sorensen described how various factors influence design for small modular reactors.[5]

Neutron temperature[6] requirements:

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:

Various conclusions about the three fuels and possible reactor types were then drawn:[5]

Higher temperature reactors can operate at higher thermal efficiency (e.g. with Brayton cycle turbines), which is desirable. High reactor pressure is a safety concern.

Some perceive U-235 as scarce. It is a finite resource, though there is 40 trillion tons in the Earth's crust. Nonetheless, this reactor model plans to exploit a larger fuel source, 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."

He notes that while 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
Status Concept
Main parameters of the reactor core
Fuel (fissile material) 233U
Fuel state Liquid (FLiBe molten salt)
Fertile material 232Th
Neutron energy spectrum Information missing
Primary control method Negative temperature coefficient
Primary moderator Graphite
Primary coolant Liquid (FLiBe molten salt)
Reactor usage
Primary use Generation of electricity

An independent technology assessment coordinated with EPRI and Southern Company represents the most detailed information so far publicly available about Flibe Energy's proposed LFTR design.[9]

Low pressure,[5] high temperature molten salt reactor

Initial Plan

In the 12 May 2011 "Introduction to Flibe Energy" with Sorensen and Dorius,[17] an interview of Sorensen from 28 May 2011[18] and another from 14 July 2011[19], the creation of LFTRs was discussed.

"The real challenge will be getting to the first unit." — Kirk Sorensen[19]


World energy consumption by fuel type; historical data 1990-2008, with projections to 2035[20]

Sorensen estimates that it will cost "several hundred million dollars" to get to the first LFTR.[19]

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."[19] 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[21] per watt, making it competitive with the construction costs of natural gas plants.[22]


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:


In order to achieve its goals, Flibe Energy intends to work with the US Armed Services,[26] 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[27] and the US Army would like its bases to have self-sufficient power generation capability (described as "base islanding"), which a LFTR could provide.[18][28] 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.[5]


Four specific difficulties have been mentioned:[5]

In addition, this reactor may require parts different from existing reactors, making them more expensive.

Kirk Sorensen

Kirk Sorensen

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.[29][30][31] 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.[18][32]

He has discussed the potential of thorium and LFTR technology for The Guardian's 2009 Manchester Report on climate change mitigation,[33] Wired (magazine)[34] and the TEDxYYC conference in 2011.[23]

Sorensen was written about in the book SuperFuel[35] and appears in the documentaries Thorium Remix 2011,[36][37] The Thorium Dream[38][39][40] as well as being credited in the upcoming "film about thorium" titled The Good Reactor.[41]

See also


  1. Flibe Energy company website
  2. September 27, 2011 New Huntsville company to build thorium-based nuclear reactors, Huntsville Newswire
  3. "Don't count out nuclear just yet". CNN.
  4. .Energy from Thorium, LFTR Technology by Flibe Energy
  5. 1 2 3 4 5 6 Presenting at ThEC2011 and powerpoint file of slides Archived October 16, 2011, at the Wayback Machine.
  6. 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.
  7. Westinghouse SMR
  8. Westinghouse announces Small Modular Reactor
  9. "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.
  10. 1 2 EPRI, 2015, 2-1.
  11. EPRI, 2015, 2-2.
  12. EPRI, 2015, 3-8.
  13. EPRI, 2015, 3-30.
  14. EPRI, 2015, 3-9 & 10.
  15. EPRI, 2015, 3-11.
  16. EPRI, 2015, 3-12.
  17. 1 2 Introduction to Flibe Energy: YouTube Video (~20 min) and PDF of slides used
  18. 1 2 3 Kirk Sorensen: Thorium Could Be Our Energy "Silver Bullet" MP3 (first 38 min)
  19. 1 2 3 4 5 Could Thorium solve the world's energy problems?
  20. 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.
  21. 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.
  22. Dr. Kiki's Science Hour 84: The Nuclear Alternative (note cost discussion starting ~29:20)
  23. 1 2 3 4 5 6 TEDxYYC - Kirk Sorensen - Thorium (Calgary, AB, Canada April 1st, 2011)
  24. Flibe Energy Announces Board of Advisors
  25. 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."
  26. Waldrop, M. M. (2012). "Nuclear energy: Radical reactors". Nature. 492 (7427): 26–29. doi:10.1038/492026a. PMID 23222589. "The company is developing a 40-megawatt reactor that might be used on military bases so that they can operate independently of the grid."
  27. Sorensen has cited the loss of power to the Redstone Arsenal near Huntsville following the April 25–28, 2011 tornado outbreak () as an example.
  28. 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."
  29. Sorensen, Kirk. "Blogger: User Profile: Kirk Sorensen". Kirk Sorensen. Retrieved 11 March 2015.
  30. "Our Company". Flibe Energy. Retrieved 11 March 2015.
  31. Sorensen, Kirk. "Thorium Research in the Manhattan Project Era". University of Tennessee. Retrieved 11 March 2015.
  32. Doug Caruso (7 March 2010). "The mighty thorium". The Columbus Dispatch. Retrieved 26 October 2011.
  33. Manchester Report: Thorium nuclear power
  34. Uranium Is So Last Century — Enter Thorium, the New Green Nuke
  35. SuperFuel: Thorium, the Green Energy Source for the Future at Google Books. ISBN 9780230341913
  36. THORIUM REMIX 2011
  37. Thorium Remix 2011 at the Internet Movie Database
  38. Motherboard TV: The Thorium Dream (November, 2011)
  39. Thorium: World's greatest energy breakthrough? (CNN.com)
  40. Motherboard TV: The Thorium Dream (YouTube video)
  41. Cast | The Good Reactor
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