Imagine a form of nuclear energy with greater output and virtually no safety issues.
Such is the promise of liquid flouride thorium reactors (LFTRs), and we’ve had several past interviews with thorium expert Kirk Sorensen to discuss their potential:
Kirk Sorensen provides an update on the current state of thorium power. The bad news is that it still remains mostly theoretical concept; no operational reactor has been deployed yet — even as a prototype. However, new thorium nuclear molten salt experiments were just started in Europe.
We have good “line of sight” on the science to build one — so, at this point, the limiting factor is mostly funding. In a world of privately-funded space travel, such a gating obstacle shouldn’t remain for long.
This is one of the “bright spots” in the technology universe that offers real promise for addressing many of the challenges presented by our global addiction to depleting, pollutive fossil fuels.
Of course, perhaps humanity gaining access to an abundant source of cheap, hi-yielding energy may not be the best thing at this point — as it will enable us to extract and consume the rest of the world’s depleting resources (key minerals, water supplies, developable land, etc) at a much faster rate.
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.
It will be a low pressure, high temperature molten salt reactor.
FLiBe fuel and 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 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.”