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Flibe Energy

Flibe Energy

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.


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.

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.


In 2015, the Electric Power Research Institution (EPRI) partnered with Southern Company to conduct an independent technology assessment of Flibe Energy's LFTR design.

In July 2018, the US Department of Energy announced that Flibe Energy had been selected under the Advanced Reactor Development Projects pathway to partner with Pacific Northwest National Laboratory to develop the fluorination technique in the chemical processing system of LFTR.

Also in 2018, a report by Sandia National Laboratories was published to develop a safeguards model for Molten Salt Reactors in order to better understand the safeguards needed for this type of system. The work performed for the report was "specifically focused on modeling liquid-fueled designs with on-site processing" and cited the LFTR design from Flibe Energy as 'the most mature concept in this category."

Flibe Energy reactor

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.

  • 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
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. 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.

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




Kirk Sorensen

President, Chief Technologist, and Co-Founder

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