Nuclear Fusion

seamus

In similarity to the AI thread - will this ever become a reality? The current problem with fusion is the energy required to excite atoms enough to overcome their repulsive forces, and once this is overcome, then we must prevent the reaction from spiralling out of control. Since the research is obviously heavily guarded, does anyone know what sort of advances have been made? I believe they are close, but obviously have no basis for that. As well, it seems like it's a bit too much of the perfect solution to all our problems, maybe god is teasing us??

Also, how usable is the power generated? Using sci-fi references, the warp drive in Star trek is a nuclear fusion reaction catalysed by a matter/antimatter reaction, ie. matter and antimatter annihilate eachother when in contact and release loads of energy. Would this be a viable solution for catalysing fusion reactions instead of using a fission reaction, seeing as antimatter has been created recently(ish)? And to further that, would anyone think it is possible to direct the energy created in a fusion reaction to be used as propulsion, or is it really only usable for power generation? What would be the power output, even if loss was at around 10%? Sounds like a good topic to me but tis up to you lot.

bonkey

Originally posted by seamus
In similarity to the AI thread - will this ever become a reality? The current problem with fusion is the energy required to excite atoms enough to overcome their repulsive forces, and once this is overcome, then we must prevent the reaction from spiralling out of control.

Actually, there's no case at the moment for the reaction spiralling out of control, that I'm aware of. Of course, I could well be wrong on that.

Fusion, at present, is typically based on one of two systems. One uses an array of high-powered lasers, fired at a small bubble containing (IIRC) deuterium. The ultra-high pressure and energy levels allow fusion to occur.

The second method uses a toroidal enclosure, and some seriously powerful magnets to have the same net effect.

The main issues are twofold. At present, it requires more energy to initiate and sustain a fusion reaction than the reaction produces. Secondly, these experiments are done on relatively small scales (i.e. using very small amounts of matter) which would make a sustainable reaction impossible.

In fairness, they have been very smart about it. In general, the reactions are small so the problems of containment and runaway reactions do not arise.

Since the research is obviously heavily guarded, does anyone
know what sort of advances have been made? I believe they are close, but obviously have no basis for that. As well, it seems like

You may be confusing cold fusion and fusion. Man-made fusion reactions have beeb a realtiy for a long time - they are just to o expensive to be useful as a soruce of energy.

Cold fusion is a slowly dying area of research which has never truly done anything remarkable. Yes, I know that people have demonstrated remarkable systems which produce vast quantities of energy, but nothing has ever come of these.

Also, how usable is the power generated?

Power is always useful. Tapping it is the problem - but thats typically done using heat-exchange mechanisms (water to steam, steam to drive turbines).

Using sci-fi references, the warp drive in Star trek is a nuclear fusion reaction catalysed by a matter/antimatter reaction, ie. matter and antimatter annihilate eachother when in contact and release loads of energy. Would this be a viable solution for catalysing fusion reactions instead of using a fission reaction, seeing as antimatter has been created recently(ish)? And to

Antimatter has been created for a fraction of a second in a supercollider. If we had a means of actually containing large amounts of antimatter in order to use it in a matter/antimatter reaction, it might become a possibility, but I think you'll find that the cost of storing the antimatter would outweigh the energy produced by it in a reaction.

Also, matter/anti-matter reactions are neither classed as fusion nor fission, I think.

further that, would anyone think it is possible to direct the energy created in a fusion reaction to be used as propulsion, or is it

It would probably be a terrible means of propulsion - not much different to the theoretical model from the 60s of using nuclear explosions to drive a ship forwards. But thats just an uneducated opinion Of course, there are other ways to use it for propulsion (see below)

If you're thinking of star-trek science though, be warned. The propulsion systems described in that series are ridiculous. They do not rely on the action/reaction principle to begin with, and while not impossible, they rely on scientific mumbo-jumbo. Basically, the authors devised a system which is not explicitly prohibited by modern science (at the time at least) but which is not necessarily possible.

In other words, good use of analogy, but dont take it any further, or Occy will get narked at you

really only usable for power generation? What would be the power output, even if loss was at around 10%?

Well, now, here's the thing. At the moment, there is no power output because fusion costs more to create than it generates. Why? Because the high temperatures and pressures needed do not exist naturally. Even if we started a fusion reaction, it most likley could not be self-sustaining - as evidenced by fission-fusion bombs and fusion experiments.

If it were practical (lets say they do find a way) then the description of "only usable for power generation" is a but unfair. Consider (for example) experiments done to use lasers against solar sails as a means of propulsion. What drives the lasers? Oh - yes - power

jc

Shiminay

I remember reading an article on this subject a few years back which stated that in theory, they could make a fusion reactor sustain itself with the power it generated, so I can only guess that maybe now they're approaching the stage where nuclear fusion is creating "extra" energy but not enough to be commercially viable. Hopefully soon! Fusion produces little waste, yeah?

bonkey

Originally posted by Kharn
I remember reading an article on this subject a few years back which stated that in theory, they could make a fusion reactor sustain itself with the power it generated, so I can only guess that maybe now they're approaching the stage where nuclear fusion is creating "extra" energy but not enough to be commercially viable. Hopefully soon! Fusion produces little waste, yeah?

They are approaching the break-even point, but I dont think they've gotten there. The problem is that the current experiments all use "one shot bursts " to my knowledge. Turning this into continuous production would be another matter entirely (no pun intended).

And yeah - fusion, if using light elements (deuterium for example) is pretty much perfectly clean.

Bob the Unlucky Octopus

Fusion involving deuterium and tritium (usually tritiated water), both forms of hydrogen has been successfully peformed many many times. The trouble is, energy output-input ratio is very inefficient, unless the reaction is very small. It is also supremely difficult to control a fusion reaction beyond a certain point- the reaction ends up degenerating into a two-split reversible reaction, entropy's way of trying to restack the chessboard if you will. Now, a small diversion, feel free to skip over it:



And I don't mind if people refer to science fiction sources, as long as they do so in a scientific and intelligent manner with a sense of perspective- like the way seamus has. I frequently refer to Jules Verne when I discuss 20th century science- many were driven, for over a hundred years by his imagination, and his vision actually shaped large parts of the world we live in. He effectively brainstormed the submarine, we still use the (at the time ficticious) names for the various instruments found in Captain Nemo's Nautilus on our own submarines. I have therefore, no objection to such comparisons if they are made sensibly and with a bit of perspective. The only problem with sci-fi television in particular, (with the notable exception of Babylon 5) is that people tend to spout jargon to explain complicated scientific concepts. Which I despise...desperately.

Just for the record, I'm not a trekkie: I hate the namby-pamby pyjama-wearing, tricorder-waving, jargon-spouting, 60's-hairdo-sporting, and generally annoying spin-offs that comprise the world of Star-Trek. That is of course, my humble opinion.

Now, back to fusion- cold fusion was never really more than a dream, and will probably stay in our imagination I think. Several people have claimed to have produced a sustainable and viable energy source with supercooled materials, the only problem is...these reactions are not just on a minute, but miniscule scale, with the atoms barely fluctuating. If you want to call that success...you'd have to call a few nitrogenous atoms on a piece of rock from Mars evidence of alien life. More to the point, it has no practical use...the research is now at a dead end.


Just as an aside, it'd be an interesting idea for someone to start a thread on means of energy production, listing their preferred means of producing energy, its viability, pros and cons scientifically explained, etc. I might start one myself next week when I have more time

seamus

A lot of great info there, I'm really fascinated by this subject and I dunno why . I agree with Occy on the cold fusion front. Many people have come forward proclaiming the mystery solved, only to not be able to reproduce their results, either on a larger scale or at all, and there are very few major companies investing in this now.

My knowledge is based on what my 6th year physics teacher told us about fusion(they've never discussed it properly even on the college 1st year syllabus). Afair, isn't the Hydrogen Bomb essentially a fusion reaction started by a fission reaction(I could easily be wrong)? This would mean that power output is not seriously hampered by the energy needed to create more reactions, provided the amount of deuterium available is large, otherwise, it twould be a fairly crap bomb.

I had never heard of deuterium - tritum reactions before, sounds intruiging(sic). From what I have read the fusion reaction was always described as two deuterium atoms fused to create a Helium and loads of energy > than a fission reaction . Seeing then, they have used fission reactions to create a fusion reaction, would there not be excess energy left over after catalysing a second fusion reaction? Or is this the fundamental theory that no-one can seem to prove? I'm not arguing with anyone, I'm just looking for answers. The web tells me very little, because companies give away no info. The first ones to get it right will be completely rolling in it.:)

As for propulsion, it does sound like a pipe dream. Since reactions are fundamentally explosions, then the energy goes out in all directions, making it pretty useless for propulsion. Has anyone heard of attempts to utilise the power from any type of explosion directly? It sounds like a good idea to me. The IC engine is the only machine I've ever heard of that uses explosive power directly(I think )

Feel free to disprove/rubbish me

daveirl

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bonkey

Originally posted by daveirl
FFS people a coal plant puts out more nuclear radiation than a well run modern Nuclear fission plant.

Thats a bit unfair. People do not dislike nuclear plants because of the radiation they emit.....

A coal plant does not produce toxic waste with a halflife so long there is no known way to securely store it. Nor does it run the risk of becoming another Chernobyl.

As for Seamus idea of "excess" energy....there are is one big problem...

You get deuterium (or tritium) and fuse it into Helium.Why cant you just fission this apart and do it again and again, reaping the energy gain each time? Count the neutrons

AS for fuel cells....there is a few problems....if memory serves me correct. SciAm had a discussion on this recently, and I also saw a documentary or perhaps an online article (cant remember) about some big "energy guru" in the US advocating fuel cells and others debunking him because he ignored the issue of the hydrogen generation. Oh - hang on - I saw it as a lonk off slashdot about a month ago....thats where it was.

1) Production of Hydrogen - there are some models which show how this could be done efficiently, but in general, a fuel-cell is considered to be more like a battery than a generator - which means that it doesnt remove the problems of generation.

2) Most efficient fuel cells use platinum as the catalyst. This is fine while FCs are not massively popular, but if there were to become (say) the energy-supplying source for all automobiles, the world would run out of platinum inside about 6 months according to the last figures I saw.

jc

daveirl

This post has been deleted.