Fine progress for ITER.

Reflections on fusion history, current events, and predictions for the 'fusion powered future.
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Richard Hull
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Re: First the Pregnancy...

Post by Richard Hull »

There a vast gulf affixed between fission and fusion, regardless of what we think we observe in the processes.

In fission, seemingly dead material ( mater) does not require any input energy, yet can be merely macro-mechanically assembled and fully controlled to deliver, on demand, as little or as much energy as needed up to its net mass equivalent. (critical mass assembly) It is always an exothermic reaction or a net energy producer. We note the disolution of mater in this case into two nuclei, both huddling about the middle of the periodic chart masses

In fusion, seemingly dead material always demands that vast amounts of energy be applied or added to the dead material, plus, a number of special subatomic mechanical conditions must also be made to exist and then regardless of what we see happen, particle wise, we evolve a process yielding either net excess energy or net loss of energy, depending on whether an exothermic or endorthermic fusion has taken place.

The key differences are fission needs no input energy and is a 100% exothermic, energy producer. Fusion demands input energy in 100% of all cases and may or may not produce excess energy once the fusion occurs.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
David Geer
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Re: First the Pregnancy...

Post by David Geer »

The CNO fusion reaction in a star is nearly self-sustaining in the right environmental conditions. We don't have the sheer resources to duplicate it but with the combination of other fusion and fission reactions, a sustainable fusion event occurs with these specific atoms.

Using exothermic and endothermic reactions is the only sure way to produce long sustainable energy output aside from standard exothermic nuclear fission reactors. Fundamentally different but mutually beneficial to eachother.

-David Geer
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Re: Fine progress for ITER.

Post by David Geer »

I was talking about amateur folks running on large funding without the board of directors and project guidelines getting in the way of scientific progress. I do believe the ITER project is a great scientific undertaking and they are learning a great deal about particle behaviors and engineering improvements.

A simplified goal with a complex and difficult road to reach it. Not what they have for the big projects now, where a single project has numerous goal objectives being mandated from higher authorities.

I guess the bottomline, is that, these projects funded by government or multi-national efforts need to be streamlined and not simply for academia.
- David Geer
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Chris Bradley
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Re: First the Pregnancy...

Post by Chris Bradley »

David Geer wrote:
> The CNO fusion reaction in a star is nearly self-sustaining in the right environmental conditions. We don't have the sheer resources to duplicate it .....
(....nor the gravitational field, it would appear...)


> but with the combination of other fusion and fission reactions, a sustainable fusion event occurs with these specific atoms.
I've posited here before that it is irrelevant to consider the 'CNO' cycle and all we need do is pick the fastest, most useful reaction in that chain. It takes an eternity for each step to happen for any quantity of these reactants that can be contained on earth.

The 'possibly useful' reaction CNO teaches us is the p+15N reaction, which seems only a little bit more unlikely than the p+¹¹B (and some folks talk that up as a walk in the park, so why not p+15N?).

But this is a thread about ITER, and magnetic confinement can never likely do any fusion for the so called 'advanced' fuels because there is too great a power loss from the plasma from higher Z thermal plasmas.

What you have to do to avoid losses in a thermal fusion plasma is decrease the plasma surface area (through which losses flow) to volume. There is no object within several light years of us with a smaller surface area:volume ratio than the Sun.

Hence, because the Sun is also suspended in a vacuum, this is why it becomes incandescent even though its specific power, by volume, is a couple orders of magnitude *lower* than the heat output of a mammal.
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Chris Bradley
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Re: Fine progress for ITER.

Post by Chris Bradley »

There are such projects I'd put in that category and they still have problems: General Fusion, Focus Fusion and FPGeneration appear to surely fit into the 'non-academic' definition - I would tend to describe these folks as 'well-funded amateurs' (excepting the last who now appears to have run out of funding).

Then there are EMC2, Tri-Alpha, Helion Energy and others that are 'academic lead' but not with the 'Board of Directors' format you are describing as being the 'big hold-up'.

Then there are those amateurs who are doing/have built 'non-fusor' reactor configurations never before attempted by amateurs, such as FamulusFusion, Bee Research, Ed Miller and myself. In all these cases, I think I am right to say that funding and interfering Boards of Directors aren't the fundamental issues - other limitations come to bear, as they always would in any project (e.g., time, space, opportunities to disseminate).

So, on evidence, it looks more to be the 'problem' that is the limitation, not the organisation per se.
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Re: First the Pregnancy...

Post by Dan Tibbets »

Speaking of CNO fusion and fusion in general. The Sun is indeed a low power density fusion reaction. But, again remember that it is burning by the P-P reaction (except ~ 1 % by CNO). If it was burning D-D it would be ~ be fusing at a rate of ~ 10^15 times faster. If it was burning D-T it would be ~ 10^17 times faster.
In a heavier star the CNO cycle scales with temperature at ~ the 17th to 18th power. At seveal hundred thousand eV this could max out at ~ 1/1000 to 1/10,000 as fast as D-D fusion at similar temperatures. I am not sure how this compares from a density standpoint. With the density considered the fusion power output may actually be 100-1,000 times higher than a Tokamak burning D-T. In reality massive stars may be burning hydrogen by the CNO cycle at a rate ~ 10,000 to 100,000 times faster than the Sun. This doesn't consider the volume of the star or it's core so the output per unit volume of the core or total stellar volume to the photosphere is unknown.

If 15N or 15O (I think) is used without utilizing the slower CNO steps, the fusion rate could be ~ 100 times greater, or if my memory serves me ~ 1-2 orders of magnitude smaller fusion cross sections compared to D-D cross section at the same temperature of several hundred KeV.
In a reactor burning p-15N at several hundred KeV the fusion rate would be ~ 1/10 to 1/100 times that of D-D. This occurring within a massive star that somehow had an abundant supply of 15 N would burn with impressive fusion energy output. A massive star may burn through the available hydrogen (perhaps as much as 10-20 times the amount of hydrogen in the Sun's core) within ~ 1-10 million years by utilizing the CNO cycle. By utilizing the p-15N reaction without the rate limiting (and carbon recycling) slower steps, the star would burn through it's aviable hydrogen in as little as ~ 10,000 years. I don't know what the volume of the giant's core or total stellar volume would be, but I suspect a few cubic meters of this imaginary core would compete with terrestrial hypothetical fusion reactors- possibly beating Tokamaks, matching Polywells, and approaching DPF, and that is with hydrogen (and 15N) fuel. If D-D or D-T fusion was occurring in this starthe fusion energy density would be at least several orders of magnitude greater yet.

This addresses my pet peeve that many consider stars as feeble fusion reactors compared to terrestrial reactors. The comparison is meaningless unless fuel considerations are included, along with temperature, density and system considerations. For instance a Tokamak plasma might have a given volume, but the system including the magnets, shell and building all would need to be considered if you are comparing it to a star with it's reacting core and all of the overlying non reacting layers.

The biggest problem with 15N is Bremsstrulung X-ray radiation. As Bremsstrulung scales as the 0.75 power of the temperature and the square of the Z . Nitrogen with a Z of 7 would result in increased Bremmstrulung of 49/25 or ~ 2 times that with Boron. This does not consider the effects of excess hydrogen in the fuel mix, so the net effect may be more subtle. Also, the P-15N fusion cross section may be several orders of magnitude less than the P-11B cross section at similar temperatures. With an optimistic Q of ~ 5-20 for P-11B in a Polywell, I doubt P-15N could have a positive Q. But, if Dense Plasma Focus x-ray recovery methods are utilized (perhaps 80-90% recovery efficiency) perhaps some net useful energy might be squeezed out in a larger machine. But as other losses would increase with machine size, it might also require some other fusion magnifying effect like POPS.

It would be sexy if isotropically purified ammonia or even water could be used as aneutronic fusion fuel. Of course the same could also be said for D-D fusion (from water) if you don't mind those pesky neutrons, and it would probably be several orders of magnitude easier- relatively easier but still unabtanium thus far.

Dan Tibbets
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