Hey, maybe I can be a guest on “America’s funniest home typos” 
I like it as well but one thing at a time - let’s start by making a fusion device that can boil water.
(Insert hot cup of coffee/tea jokes here.) 
They certainly did! I was working at Harwell in 1989 and I was one of a team that dropped everything to build accurate neutron detectors to measure any output from a Pons/Fleischmann cell - a busy weekend. Pity it doesn’t work 
Perhaps they forgot to carry the one.
My impression was that all you have to do is build a big enough tokamak to have the thing work. There’s engineering challenges, but no show-stoppers like with fuel cells or other tech. If people put down the money, that’s it.
It didn’t make sense why we weren’t putting down the money, but then Chimera’s post made a lot of sense. Rationally, fusion isn’t much better than fission. Fission already gives you limitless cheap, clean energy. I think it’s when you start thinking irrationally, getting all worked up about worthless hills in the middle of the desert that might become radioactive dozens of millenia from now when humans will either be an intergalactic civilization or dead, that fusion starts to look a lot better. The proliferation of nuclear materials associated with fission is a problem, though. A problem we’re barely taking any steps to deal with (with, eg, a fuel bank), partly due to those same dumb irrationalities.
Ah!
This is some new use of the terms “cheap” and “clean” that I wasn’t familiar with.
Isn’t the last word on cold fusion still, “there’s something really interesting going on, we just wish we could make it happen regularly enough to make sense of?” I think it’s all the cynics and bullies that are stopping us from getting to the bottom of it.
Oh good lord yes! I mean there wouldn’t be any value in actually being able to demonstrate and patent such a device. It’s all about keeping the truth hidden.
:rolleyes:
I’m not sure what you mean by this. You can’t have solid optics sealed everyplace – the light has to get to the target, after all, and you don’t want stuff near your exploding/imploding microballoon. My point is that, once you fire the lasers, stuff from the ablated surface of that microballoon target is going to blow off and hit the optics.
We speak from experience here – I didn’t work on laser fusion, but I have done laser ablation. Stuff that comes off a surface travels until it hits something, where it sticks. We had crud on the inside of our chambers.
And in the case of laser fusion, you don’t need much to cause trouble. You’re putting terawatts of power through those optics. A tiny bit of absorption there due to a dust speck will be lethal to the optics. When your shots are twelve hours apart, you can afford to relace the optics if you have to. But you can’t if you have a continuous process.
OK, the beam exit can’t be solid all the way to the target, but I’ve seen clever solutions to similar problems in the Semiconductor manufacturing biz: an example
But it isn’t “clean”. It produces large amounts of waste that we still haven’t worked out how to deal with.
Ok, realistically, we HAVE worked out how to deal with it, but there are too many people worried about what is going to happen 10,000 years from now (by which point I’d bet they have better solutions than we do now; or it has ceased to be an issue because we’re all dead). (IMHO: Get on with it and build the damned storage place already. I’m more worried about transportation accidents than millenium long storage issues.)
The other side of that is: We’re a large rich nation that can afford to deal with our radioactive waste properly. There are a lot less…(insert descriptive words here) nations that might be more than happy to just dump it in their local rivers, their landfills, or into the ocean. Hell, with any luck, one day we’ll wake up to find that some Chinese factory has been putting it in our cat food and children’s toys.
Then there are legitimate issues with plant safety and accidental release (see: Chernobyl, Three Mile Island) that must give us pause.
Now at the base of it, I think we cannot deny other nations reliable sources of energy. This is especially true for poor, developing nations, even moreso for those lacking their own oil or coal resources. What the hell are they supposed to depend on for power? Are we dooming them to eternal non-development?
But we do have a right and a keen interest in preventing Nuclear Proliferation.
We should take those bullies out behind the woodshed and give them a good ol’ fashioned American howdy-do! Then they’ll stop holding cold fusion back! And then we can conquer the world! Bwa-ha-ha-ha-ha!
Well … no. Ignoring for the minute the waste (which I tend to agree is not a show-stopper) the real problem for the longer term is that it is by no means limitless. Supplies of uranium and other fissionable materials are definitely finite. You can stretch them massively using breeder reactors to produce plutonium but then you really do have nuclear proliferation issues.
I’m not arguing against building fission power plants - as I’ve said before: we need every carbon free energy source we can get - but they can’t be the only solution in 50-100 years.
It was from the same lexicon used to describe 'Seventies-era Detroit automobiles as “fast”, “reliable”, “fuel efficient”, and “crisp handling”.
I hear that if you build the apparatus in your own kitchen sink “the bullies” come knocking down your door and smash the equipment while jumping up and down and yelling, “Long live Big Energy!” On the other hand, you get a very nice tracking implant and the government starts transmitting financial reports directly into your brain.
The “trick”, so to speak, with nuclear fusion isn’t confinement per se; someone already mentioned the Farnsworth-Hirsch-Meeks fusor, which requires little more than a high voltage cathode, a vacuum pump, and a cylindrical chamber. This device is small enough to fit on a workbench and run from commercial power. However, because of the limits of power density this is not a practical method for net energy production. Several different stabs have been taken at this problem but without demonstrated success. Ditto for muon-catalyzed fusion; owing to the decay rate of muons (which act as superheavy electrons and thus make it easier for protons to get close enough to fuse in sufficient frequency) it takes much more energy to maintain muon production than can be extracted from the products. Laser or particle inertial confinement requires high and regular stimulus; it’s not clear how this could ever be made workable for an energy producing systems. Toroidal magnetic confinement systems like the tokamak tend to suffer from Bremsstrahlung radiation losses due to self-interference at high energy densities sufficient for power production. Some proposed designs help guide the plasma to minimize cross currents, but it is still a long, long way from being practical.
Because, roughly speaking, the rate of fusion depends upon volume, but the necessary PT conditions are bounded by a surface, the larger your fusion cell the more efficient and easier to sustain it becomes; we can see this in nature, where on very large scales fusion can be powered by the gravitational attraction of the fuel mass alone. However, on scales more relevant to terrestrial power production, losses tend to overwhelm net power output; even the largest reactors we could conceive of would need a gain factor significantly over unity to actually provide net power out.
Thirty years is probably a lower bound for practical fusion confinement based upon current technology. There might be some more practical method which simply hasn’t been developed yet, but I wouldn’t bet the mortgage on it. “Cold fusion”, being non-reproducible in laboratory environments and for which there isn’t even an established hypothetical mechanism that is accepted by credible peers, is at best proto-science. Even if there is “something” anomalous going on there, there is no indication that it can be used for practical power generation despite the enthusiastic tin foil hat-ism of the free energy crowd. Ditto for Blacklight Power, et cetera.
Stranger
So, if I understand you correctly, it will take a revolutionary rather than evolutionary leap in technology to make commercial-scale fusion power a reality. IOW, it isn’t just a matter of throwing money at it, we need a new, as yet unforeseen idea to make it work. Which means that it could come next year or never.
Thanks,
Rob
In a nutshell, yes. There are significant basic control and plasma dynamics problems for which no clear path toward resolution exists; in other words, it is still a basic science problem rather than an engineering challenge. There are, of course, substantial technical hurdles as well, including how to effectively extract energy from it. As a “fancy way to boil water” nuclear fusion is problematic, unlike nuclear fission, which uses a fluid medium to both moderate the reaction and convert thermal energy into the mechanical energy of fluid motion via conduction and convection, an attempt to extract energy from nuclear fusion will be by pure (thermal) radiation, straining or exceeding the limits of material science to carry away such energy without breaking down. A possible method of power transfer, especially in magnetic confinement systems, is by magnetohydrodynamics, i.e. causing the charged plasma to create conductive currents in electromagnets. Doing this in a way that is efficient and doesn’t inhibit the fusion process is yet another major challenge, however.
I’d put real money that we won’t see practical confinement fusion in the near future (next couple of decades) at a minimum, much less power generation applications. More likely it’ll be fifty years or more. I think we’ll develop it eventually (unless some even more desireable method of energy production comes about) but it’s hard to say when or specifically what it will look like.
Stranger
Stranger on a Train, I didn’t quite follow you. You seemed to agree that just by making a big-enough reactor, most of the problems go away? This is the main thing I’d like to understand. But also, do we really have no good way to collect the power? Wouldn’t that be problem numero uno?
Making a reactor larger in general tends to scale down the losses–and in general, this is true with any bulk energy conversion process, up to a point–but the gains are not significant enough to overcome losses, at least not on any practical scale. And of course, the larger you make it, the the more power required for initiation and confinement, even if it is a smaller proportion of the overall gross energy budget. Converting and transmitting that kind of power into something that can sustain the fusion reaction is not trivial; in multistage fusion weapons, this is done by reflecting x-rays from the primary (fission) explosion into a secondary. Of course, that’s not something you can do in equilibrium; if a controlled nuclear fission reaction is “twisting the dragon’s tail”, controlled nuclear fusion is like trying to perform oral surgery on Godzilla as he rampages through Tokyo.
Problem “numero uno” is just to extract significantly more power out of a fusion reaction than it costs you to confine it. We still have yet to achieve that goal. Once you have a sufficient amount of energy output to justify the business of trying to squeeze deuterium atoms together (and estimates range from a gain factor of Q=10 to 100 for an effective and sustainable reaction), then you have the problem of trying to convert the energy coming out of the reactor into something you can make use of. The “temperatures” of particles coming out of the reactor are literally unearthly; and it is not, as with a fission reaction, as if you can have a water moderator flowing through the core, absorbing neutrons to cause mechanical fluid motion. So you have a relatively small surface area (around the reactor) in which to absorb a lot of energy, and then quickly distribute it out sufficiently that it won’t cause materials to degrade.
With D-T fission (by far the most likely candidate for controllable fusion) the most energetic products are fast neutrons with 14.1 MeV of energy, which are virtually useless of power production as is, while the heavier alpha particle (the energy from which can be captured by interactions in electromagnetic fields) is only 3.5 MeV. Either you are going to lose about eighty percent of your energy yield, of you have to figure out some way of making use of fast neutrons. One possible solution might be to have a dense, fissionable (but not fissile) material that will absorb energetic neutrons and produce slower moving thermal neutrons that can be used for thermodynamic steam cycles; of course, you then get back to the issue of having to deal with radioactive waste (though you could presumably fast fission products down to relatively benign isotopes if you can afford the losses).
So there are a number of basic problems that have to be addressed before power generation from fusion beyond merely obtaining an over unity yield. Making things bigger lets you minimize the “edge effects” of a smaller system but it doesn’t rid you of basic issues.
Stranger
Stranger - I think you are being too pessimistic. IANAPhysicist but my understanding from the physicists is that the problems are understood and routes to resolving them can be seen. Thislink (Note: pdf file) is to a paper setting out a fast track route to commercial fusion power production. It dates from early 2005 - most of the work was done in 2004 - but it gives a pretty good summary of the issues to be addressed and the facilities needed to work on them.
In the three years since then no show stoppers have turned up and a start has been made on building ITER and designing IFMIF. As always there are technical - and organisational - problems in constructing something as complex as ITER, particularly as an international collaboration, but it will happen - too much political capital is tied up in it to let it fail now.