Tokomak

[Doug Coulter]

You're not going to hear me say I think toko's are a great idea anytime soon, as I don't like the physics model much. But hey, they are doing nice work anyway, and in this case, have a nice spokesperson.
http://www.ccfe.ac.uk/videos.aspx?currV ... urrCateg=0

I like the big flywheels so they can get more peak power than the British grid can provide...

In a fairly strange twist of fate, someone has decided that for ITER, they need a real fusion source first to test some parts, and a variant called a spherical tokomak does that better....hmm, why then are they still planning to build the inferior model "in the large"? I have no clue, and they're not saying.

But here is an example of one. http://www.ccfe.ac.uk/MAST.aspx

This and slight variants are being proposed to actually make enough fusion to test things like wall blankets for ITER -- because ITER won't! ??? If it works that well, and right now, well, I see a little cognitive dissonance going on there.

So far it seems all these guys are testing with DD, then extrapolating to DT, which of course makes much nastier fast neutrons. They are planning to breed the T in a 6Li blanket material, using unspecified "neutron multipliers" as they need more neutrons to breed T than the DT reaction makes, or more accurately, they won't capture the required 100% of them needed to breed enough T, assuming zero losses of it.

Does that smack of driven, sub-critical fission to anyone else? Why then are fusion-fission hybrids being talked about as a separate issue?

Clearly, either I or they don't get something here.

[chrismb]

So far it seems all these guys are testing with DD, then extrapolating to DT, which of course makes much nastier fast neutrons.

As far as I am aware to date, there are only two facilities set up to handle tritium, and these are JET and TFTR.

For the remainder of the tokamaks, again as far as I know, the majority actually don't even run DD - they are all H [or other heavier gases] plasma experiments. Just...plasma....experiments....

JET has run two experimental 'campaigns' on tritium over the years, but most is still H or DD. I'm lead to believe the reason is actually a little more mundane than an issue with getting or handling tritium - JET has a lifetime budget of 2E21 neutrons permitted. (I think this neutron budget figure is due to total activation and permitted displacements per atom in the structure.) It has got most of those from the DT experiments. So it runs DD to keep the total neutron emissions down, which is currently one tenth of that budget. I believe the aim is to finish its days (which I think is planned for only a few more years) with more DT experiments.

They are planning to breed the T in a 6Li blanket material, using unspecified "neutron multipliers" as they need more neutrons to breed T than the DT reaction makes, or more accurately, they won't capture the required 100% of them needed to breed enough T, assuming zero losses of it.

I've asked the ITER press office about what plans there are for the blanket experiments and...get this... there are currently no plans. They are still talking about it and there is not yet a specific objective to run a blanket with ITER! So here we have an experiment that potentially is to demonstrate viable fusion, but that they have not yet planned the experiments to show viable fusion (as it isn't viable without tritium breeding).

That's not to say they won't put it in place sometime in the decades-long timescales of ITER, but I was surprised when I was told that!

I do not believe ITER is actually a good scientific experiment because the objectives are unclear. It is a load of activity to make a big tokamak. What is the objective? I've directly suggested that it is off-message and that if it were really to show tokamak power stations can work then it should be 100% directed to a machine that pumps out energy. They are planning to spend years on investigating special materials when, in actual fact, they could make not just this but jump to a DEMO version, making the darned thing out of stainless steel, run it at net-power, and then have proved the experiment. Once they are making net energy, solutions would be found to overcome all the other issues quick enough... once folks can be confident that there really is a power station at the end of the effort. So why are they wasting time on exploring materials when they could get busy building a bigger version of JET in a quarter of the time at a quarter of the budget to prove viable over unity power? Sure, they'll end up with a slightly more activated pile of scrap than if they spent an extra 20 years investigating low activation materials, but if my suggestion was followed, to go straight for a DEMO power station out of stainless steel and run it for a few months to show it could be done, the stuff would probably not even be radioactive after that long!!!!

It's almost as if whoever is actually running the project has decided it's going to work and that they actually delude themselves to think the only remaining issues are engineering ones. I'm afraid that my opinion is that no-one is actually in charge of this runaway gravy-train and no-one knows where the brakes are even if they figured out there are better ways to approach the experiment.

Surely the experimental objective is to prove magnetic confinement can be used as the basis of a fusion power station. ITER, alone, cannot do this, so why is it being done? DEMO, the one that is meant to come after ITER [if it is successful] can show this, so why not just go for DEMO?

[Doug Coulter]

Yup, that pretty much sums up what I think, too. Are they really that sure they're going to get to net power? I kind of doubt that, and they are going so slow as to make it possible (and already happening) that others are learning new ways to control plasma instabilities that make their current design not so good. If they're worried about neutron damage and all that, why not just run in intermittent mode for awhile? Heck, that's what I do with fusors here, as otherwise I have issues with how many neutrons I'm willing to have in the lab (and in ME!). Seems simple enough an idea for starting up.

I think it's a tenure-mill, a sinecure for privileged scientists who have played the office politics well enough to get a fun job that doesn't require them to produce timely results, and that it's one of the more extreme cases of that in "big science". And it seems they are dumb enough to be using academic type scientists as engineers -- not a good idea if you want things to work right.
(NASA has fallen into that trap as well for various political reasons, and it's not serving them well at all)

Which is not to say I think their funding should be cut off or anything like -- I want to see working fusion power before I die, darnit, and this is one possibility -- though perhaps not the best one.
On the other hand, think how different that would be if one of the good CEO's was running it instead, with hire-fire power, the power to change direction the instant something was found that wouldn't work, and the power to immediately turn on a dime if something new was found out. Get that Alan Mulaly from Ford, and they'd be kicking butt in no time! Heck, even a CEO who basically stinks (think Larry Ellison or Mark Hurd) would be better than how it is. And Lloyd Blankfein would find a way to have it make money every day, on top of the rest!
Of course, there are counter-examples. Bill Gates would make it make money whether it worked or not, and Steve Jobs would make it pretty but wouldn't let anyone else have their way with it afterwards.

In other words, do it like we are doing it in our home labs, but just with more resources and talent -- I've found having more resources a good thing and at least part of the reason I've done so well here, it never hurts to be well off -- though as many startup businesses have found, you CAN have too much money to develop the correct discipline. Most of the stick in the mud old-school scientist types would quit of course, being resistant to change of any kind -- is that bad? I think not!

To me, though, one of the biggest problems with this kind of thing is the scaling factor -- plain old surface to volume ratio means you can't do quick test kinds of things so easily. I'm sure there are other issues, but the requirement that it be huge to work at all is a big hindrance to getting anywhere, even if you can afford it. It's not the affording of just one -- you might need to build a number of them to get anywhere as in, duh, all other hard science. At least fusors and even DPF devices don't seem to care so much about scaling, insofar as I've tried. They are a little better when a little bigger, as often as not, but it's not a huge factor in tests here over range of about 3::1 size/power.

Of course, there's all the other scientific objections to trying to contain the snakiest stuff on earth with magnetism and keep it thermal a long time at pressure, while blowing current through it, when it's like trying to comb the hair on a sphere -- there's always a cowlick until a new geometry or physical dimension occurs on this planet -- quite unlikely. (which is the same problem Bussard's thing has -- there will always have to be a leak, you can't make a monopole). Even with those objections -- it could work, though poorly. That would at least be a beginning to improve what can be improved, and some motivation to get real serious about it, as you point out.

Yeah, I think they should just get on with it, and know if it's even worth sweating those other problems. This kind of reminds me of the hubris we Americans had about the Soviet bomb effort. We were so sure they'd not make it anytime soon, as we'd had such an effort to get there. But they had one extremely important thing we didn't, that was overlooked entirely.

An existence-proof -- they knew there was light at the end of that tunnel, and more or less where the tunnel had to begin.

As you point out, ITER seems to be trying to avoid that step or are fearful of a non-existence proof, just as likely. Which would turn the gravy train right off for them. Even honest scientists can fall prey to that kind of rationalization without realizing they are doing it, it's pretty hard to avoid.

The one good thing I think we can take away from this effort is all the nice tricks they are using as diagnostics, to find out what's really going on in there -- those are useful in our other approaches too.