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FAQ: Fusion Fuel Cycles

Posted: Thu Nov 12, 2015 4:40 pm
by Paul_Schatzkin
Newcomers especially often have questions about what "fuel" materials can be used to produce fusion. There are several combinations of molecules that produce fusion, from the simplest D+D to the more complicated (but perhaps more desirable) P+B11.

I found this very straightforward explanation of the various combinations and their advantages and disadvantages: ... they-work/

Re: FAQ: Fusion Fuel Cycles

Posted: Sat Nov 18, 2017 1:25 am
by Richard Hull
I must add this to this fusion theory and fuel cycles posting. It goes a good bit deeper on the subject than the above link posted by the perfesser for the advancing fusioneer.

Probably the best ever discussion on this subject but, unfortunately buried in the minutia, was posted by Scott Stephens in a January, 1999 post. For those who are somewhat cogent and conversant in the theory, this post is a rare superlative of straight talk. I recognized this back then and have commented on this and given this URL in past postings. I hope that in this FAQ it will supply a real grasp on a number of possible fusion fuels and their advantages and many issues as to why they just will not work. ... sg-48.html

Read and learn from this excellent compilation. For my money, there is no better comprehensive discussion on this entire 19 year effort, related to fusion theory and the fusion fuels to be considered even remotely viable.

Richard Hull

Re: FAQ: Fusion Fuel Cycles

Posted: Sat Nov 18, 2017 5:41 pm
by Dennis P Brown
To be complete - any fusion fuel cycle should at least discus these devices as effective breeders for fission based fuels; in this manner, a poor performing fusion reactor can still produce and support many fission reactors via breeding of fissionable uranium from non-fissionable uranium; unlike a regular fission breeder which has extremely serious proliferation issues but also must have very high energy density reactors (to effectively breed fuel) these reactor designs can undergo small nuclear run-away: i.e. a limited nuclear explosion.

Even a single tokamak like ITER could supply fuel for ten regular fission reactors. For comparison, it takes ten breeder reactors to generate enough 'new' fuel for a single fission reactor.

Whether fission reactors can be made inexpensive and safe enough is a side issue (my money is on the Candu design since it can lose coolant flow and never melt down) but certainly, a ITER class fusion reactor has so many available neutrons, the breeding of non-fissionable fuel into useful fuel is a very real and possible way to create a viable fusion reactor (massive net energy produced in comparison to the energy in.) Also, the fusion reactor never needs to have levels of fissionable materials in its breeding blanket that would ever create a proliferation problem - an aside: this also partly simplifies shielding for a tokamak.

So, relative to fusion burn cycles, one should consider uranium breeding by the excessive neutrons that are available from many fusion fuel cycles and how this can shift total energy costs into the black.

Re: FAQ: Fusion Fuel Cycles

Posted: Sun Nov 19, 2017 4:45 am
by Richard Hull
A fusion reactor as a breeder would be an very expensive solution. Why not just run a thorium breeder and get real power output while breeding fuel?
Again in both cases throwing all other issues to one side, at least the fission breeder is providing useful power while breeding more fission fuel. A fusion breeder would gulp power in coal car loads and just make fission fuel...a net loss.

Richard Hull

Re: FAQ: Fusion Fuel Cycles

Posted: Sun Nov 19, 2017 12:42 pm
by Dennis P Brown
Richard, all I can say relative to thorium is, when I see one operating to produce real power and fuel I'll start to believe their usefulness. Since current uranium based infrastructures (costing surely many hundreds of billions of dollars) already exist, uranium based reactors are a fact of life and getting enough fuel (if one wants to go nuclear) has issues. Since a fusion reactor like ITER will never produce usable power, as we all agree, then that device is not a viable methodology for direct power; however, it does produce enough neutrons to supply ten regular fission reactors if ITER is turned into a breeder. At the cost to build fission based breeder reactors (currently, I'd expect that to exceed $10 billion each) and that ten fission based breeders are needed to supply the fuel needed by one reactor, ITER might not be such a bad deal (lol.)

Again the American need for Sub reactors really shoe-horned this country into a uranium based, far too high a power density, reactor design. Too bad since the Candu is cheaper; but regardless, all our fuel cycle and reprocessing infrastructure costing ridiculous sums already exists and is based on uranium; might as well leverage that and the existing reactors.

Re: FAQ: Fusion Fuel Cycles

Posted: Mon Nov 20, 2017 12:09 pm
by Dennis P Brown
Here is a part of a talk I attended on breeding fission fuel using an ITER class device - the links are to the original work (Richard, note use of Th!):


"Iter can obtain a" Q~10, "which" is fine for fusion breeding 233U from 232Th. It produces 10x more nuclear fuel than neutron power alone.
ITER like device is an end in itself, not a stepping stone to who knows what DEMO, who knows how many decades later, who knows how many tens of billions of $$$ more.Next step for USA: Build the scientific prototype. A tokamak like JT-60 but runs steady state for days,
weeks months, in a DT plasma at Q~1, and breeds its own T and 233U. ITER has no plans for either. For
the first time fusion produces something the world can actually use!

(The following link was written for the average reader and is an excellent overview of the subject - this is my comment: D. Brown)

Wallace Manheimer, Fusion Breeding for Midcentury Sustainable Power, Journal of Fusion Energy, vol 33,
p 199, 2014, ... 014-9690-9 (open access)

Wallace Manheimer, Fusion Breeding: An Old, New Strategic Opportunity for Fusion, J Fusion Energy (2016) 35:117–122
Wallace Manheimer, The Scientific Prototype, a Proposed Next Step for the American MFE Program, J Fusion Energy,
(2013) 32:419–421

Re: FAQ: Fusion Fuel Cycles

Posted: Mon Nov 20, 2017 4:52 pm
by Silviu Tamasdan
There are several thorium reactors operating in India. That seems to be the only country committed to the thorium path (among others), probably because they have so much of it and it's cheap (and doesn't make them dependent on someone else's uranium).

Also IMHO while you can breed fissile fuel with a tokamak, it would be probably much cheaper and less logistically complex to just use a fission reactor that both breeds and burns its own fuel, such as a TWR