Do we need breakeven to consider fusion power sources?

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
prestonbarrows
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Re: Do we need breakeven to consider fusion power sources?

Post by prestonbarrows » Wed May 28, 2014 9:50 am

There are few, if any, people in the field who would say we are 'nearly there' in regards to a feasible fusion reactor connected to the grid. The scheduled timeline for ITER is on the order of 15 years before full scale tests are being run, and 30 years for DEMO. (and this is the sunny polished version they are selling their funding sources)
Wikipedia wrote:Handwaving is a pejorative label applied to the action of displaying the appearance of doing something, when actually doing little, or nothing.
From a physicists perspective, one can wave their hands and omit the power requirements for external coils because they could be made superconducting. That is 'just a problem for the engineers'. Doing so is not a lie, per say, but it is important to know the context if you are not familiar with their reasoning.

Another 'trick' you'll run into is extrapolating experimental D-D results to equivalent D-T results. This is because tritium is nasty stuff to deal with in real life and drags in extremely expensive handling systems and extra regulations. The behavior of the two reactions is well known and waving your hands at is is a legitimate approach in initial experimental stages.

No one is saying these issues are minor or will magically go away, just that in principle they shouldn't fundamentally matter and proving so is beyond the limitations of the existing experimental device. When you have exhausted what your experiment can teach you, you design and build a more sophisticated experiment which can address the shortcomings of the previous iterations.
Chris Bradley wrote:tokamaks have not yet been driven by a bootstrap current, which they would require
Neither of these points are correct. A quick search turns up "Quasisteady High-Confinement Reversed Shear Plasma with Large Bootstrap Current Fraction under Full Noninductive Current Drive Condition in JT-60U" or "Experimental study of neoclassical plasma flow and bootstrap current in the tokamak textor" among other papers. Also, bootstrap currents are a nice bonus that could boost efficiency under certain conditions, but not a fundamental requirement for a tokamak scheme.
Chris Bradley wrote:have not yet been driven by a superconducting magnet
Not true. See HT-7, EAST, KSTAR, Tore Supra, or upgrades to JT-60. In other words, most of the newest generation of large reactors.
Chris Bradley wrote:why don't the experiments recover that energy now?
Again, those with superconducting coils must do this any time they power down their large magnets. Some may dump it into a resistive dummy load or some may pass it back onto the grid but it has to go somewhere. Super conducting magnetic energy storage is a well developed and implemented idea in its own right.

Most older reactors use resistive copper coils which you can't recover energy from like you could feasibly do with superconducting coils. In the ideal end game scenario, you would never have to shut your SC magnets off. Simple copper is much cheaper and more practical on smaller scales. From a physics standpoint, an amp through a copper turn gives identical results as an amp through one of expensive superconductor. Scientists tend to look at the more interesting and unknown aspects first. Any experiment has limits on scope, current technology level and a finite budget. It dosen't always make sense to add the extra cost and time to integrate every possible feature.

Today, we are in the transition between emphasis on pure experimental physics of the components and the practical engineering of combining them into a full working system.
A physicist doesn't really care how you make a 5 Tesla field happen, an engineer does.

The newer existing reactors listed above are essentially partnered under the ITER umbrella and have been testing superconducting coils and non-inductive heating schemes for many years. The idea is ITER will take things demonstrated in JET, EAST, JT-60 etc and improve on them. Only the newest devices will have cutting-edge technology. Why dosen't my rotary phone have bluetooth?
Chris Bradley wrote:absolutely no guarantee that they are tractable problems
That's why its called research. Tokamak Fusion Test Reactor, Experimental Advanced Superconducting Tokamak, International Thermonuclear Experimental Reactor and so on.

Damn those Wright brothers for not landing on the moon.
Chris Bradley wrote:Under what circumstances would 'tokamak' ever be deemed a failed experiment?
If someone proves a fundamental physics limitation either theoretically or experimentally, or new generations of devices stop progressing and improving beyond their predecessors, or some other fusion scheme (MTF,ICF, RFP, DPF to name a few) is proven to work on a faster or cheaper scale, I suppose commercial tokamaks will have 'failed'.

So far, none of these things has happened yet.

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Dennis P Brown
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Re: Do we need breakeven to consider fusion power sources?

Post by Dennis P Brown » Fri Jun 06, 2014 7:10 pm

The cost for ITER is getting more and more expensive every year (still haven't even built a single real component, as far as I've seen) and I have strong doubts even if it were to cost just 10-12 billion it'd not be shorted by governments who are facing very tight budgets resulting in failure. In that sense, ITER and any future tokamacs in general are failures - simply by the fact that the cost to research dollar isn't exactly workable; that is, ITER, at present cost growth will never get finished. Any design that can't even be cost estimated within a factor of ten (!) isn't, in my opinion, a viable design - yet, as you say, it is just an experimental machine - I'd hate to see the final cost of even just a proto-type reactor.

On the other hand, as Chris pointed out, and if ITER had somehow stayed on an even reasonable budget, a tokamac fusion-breeder is capable (with currently projected performance - a big if) of producing net energy.

There is currently only one big machine that was brought in under budget and has some hope to achieve "steady state" fusion for any real length of time - the Wendelstein-7 stellarator. Whether it does ever become operational is still an open question but the basic design has been proven to work, and budget to real world cost for a finished test reactor was well understood and came in under cost estimates - tell me the last time that ever happened in a major fusion project?

While this was delayed it was primarily due to the first company unable to build the complex magnetic coils and remain solvent - that issue has been addressed, is rather well understood, and was solved.

Also, while this is a toy compared to even a proto-type power reactor, at least if it works, stellarators would appear to be a far better bet for scale up than any tokamac.

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Chris Bradley
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Re: Do we need breakeven to consider fusion power sources?

Post by Chris Bradley » Fri Jun 06, 2014 10:13 pm

prestonbarrows wrote:
Chris Bradley wrote:tokamaks have not yet been driven by a bootstrap current, which they would require
Neither of these points are correct. A quick search turns up "Quasisteady High-Confinement Reversed Shear Plasma with Large Bootstrap Current Fraction under Full Noninductive Current Drive Condition in JT-60U" or "Experimental study of neoclassical plasma flow and bootstrap current in the tokamak textor" among other papers. Also, bootstrap currents are a nice bonus that could boost efficiency under certain conditions, but not a fundamental requirement for a tokamak scheme.
Oh really? Neither point correct? So, running a tokamak on a fraction of a bootstrap current, or running one in a computer is a practical demonstration of actually driving a tokamak with a bootstrap current? I think not. And if not a self-sustaining current, how do you see the current being sustained? What practical example, here today, shows the route forward without bootstrap currents?
prestonbarrows wrote:
Chris Bradley wrote:have not yet been driven by a superconducting magnet
Not true. See HT-7, EAST, KSTAR, Tore Supra, or upgrades to JT-60. In other words, most of the newest generation of large reactors.
So, errr... what were the best fusion rates for these devices, or have you noticed if they are just hydrogen-only plasma experiments.

The issue of the line of conversation above was directed towards real and practicable implementation of a fusion reactor, not a fancy research plasma. Give me some details of the neutron rates out of these super-conducting tokamaks and I'll take a greater interest. Maybe they have by now, the Koreans are dead keen to get going (good for them), but I have not heard much lately and have not gone looking for it.
prestonbarrows wrote:
Chris Bradley wrote:why don't the experiments recover that energy now?
Again, those with superconducting coils must do this any time they power down their large magnets. Some may dump it into a resistive dummy load or some may pass it back onto the grid but it has to go somewhere. Super conducting magnetic energy storage is a well developed and implemented idea in its own right.
So what? Again to say, this thread we are talking here about actual stuff, not prospective and hoped-for outcomes. If it's that easy, why haven't they demonstrated it by now?
prestonbarrows wrote:
Chris Bradley wrote:absolutely no guarantee that they are tractable problems
That's why its called research. Tokamak Fusion Test Reactor, Experimental Advanced Superconducting Tokamak, International Thermonuclear Experimental Reactor and so on.
You are taking all of my responses out of context, if you think your retorts are justified, because I was explicitly talking about here-and-now actual outcomes in fusion research per the original question that '[the OP] would say they are almost there...', not wanna-be research projects.

Your aim is mis-judged. There is little point in taking pot-shots at me here because I am quite supportive of tokamak (and few here cheer such projects). But they have shown very little in the way of being 'almost there' and that was the origin of this particular discussion.
prestonbarrows wrote:
Chris Bradley wrote:Under what circumstances would 'tokamak' ever be deemed a failed experiment?
If someone proves a fundamental physics limitation either theoretically or experimentally
But that will never happen. You can't disprove a limitation in a field you have never mastered before. This is a recipe to go on forever because someone will always have another 'what-if'. As we approach the 4th generation of scientists now getting into tokamak research, it is clear that if one lifetime of research is not enough to convince you to give up then the next generation will always think they have some insight the old-fogies never did, and they'll carry on regardless.

My opinion on takamak is that it does show promise, but they are going about it in the wrong way. They are spending all their money on hydrogen based experiments and materials testing, and they still haven't shown the damned thing can get a fusion reaction going to pay back even 1/10th of the input energy. My prioritisation would be very different and focussed on getting fusion out of the thing.

In regards cost, bear in mind that JET came in on budget at around GBP 200 million 3 decades ago and is still the only reactor capable of running tritium experiments. JET's main costs have been its running costs, not its manufacture. Years ago when ITER started and it was still being pitched as a euro 5 bn project, I was alerting folks to my opinion that it would end up as euro 30 bn and I was ignored as being way off. Then it escalated to 8 bn. Then 10 bn. Now it is 15 bn looking to head up to 18~20 bn. I will stick with my prediction of 30 bn because it is an experiment with a poorly defined objective, and not really having a good plan always escalates costs.

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Richard Hull
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Re: Do we need breakeven to consider fusion power sources?

Post by Richard Hull » Sat Jun 07, 2014 4:54 pm

Nice followup Chris! I cannot and dare not add anything to it. You kinda' told it like it was. Power producing fusion talks and b-ll-hit walks.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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