Nuclear fusion....

[MoonRocker]

I have no doubt that they'll get it working and net producing at some point. Out of the tokamak and the laser which system is closest? I know fusion is now produced regularly but up to now it has always been at the cost of an energy overdraft. Anyone know of any completely different approaches where a surprise break through may come?

[jake-the-peg]

The largeset tokamak to date Jet was never designed to produce more energy - it was essentially a science experiment - It did however achieve ignition which was a great achievement.

Iter being build in France now is it's sucessor which should produce more energy than it consumes. This is still however not a power station. It's designed to be an Engineering experiment to answer questions about how you get the energy out, how you maintain and run such a power plant.

DEMO is planned to be the first demonstration fusion power plant. The Japanese lost to France on ITER so there's a good chance it will go there.

There are a number of other approaches being looked at - the Americans are big into inertial confinement (basically lasers) http://en.wikipedia.o...al_confinement_fusion

and there is Z pinch too
http://en.wikipedia.org/wiki/Z-pinch

But these are quite a way behind tokamaks in development.

There are a few odd ball ones where you get small amounts of fusion but simply can never scale.

For example you can have "cold fusion" that is catalysed by muons if there were to be some sort of surprise breakthough from somewhere it could come from someone finding a source of muons sufficient to make it practical.

However as demonstrated by the JET/ITER/DEMO process even when you have the physics sorted you're talking 50 years to develop and certify commercial reactors based on that physics

It's also not going to be boundless free energy - reactors cost money to build and run and maintain in a safe manner and the energy must be transmitted etc. etc. etc.

[jake-the-peg]

One further thought - energy generation may not be the right problem

Energy storage and transmission is difficult. Solar cells are developing at a fantasic rate.

Cover half the Sahara with them and that's a heck of a power plant - the difficulties of storing and transmitting the power are just so great.

If you want a world changing breakthrough my money's on high temperature superconductors

[heathfield]

Seems I've been waiting all my life for someone to come up with a practical fusion energy device. We all had high hopes for the UK's Project Zeta back in the 1950s, but little came from it. I'm pleased to learn that investigations into 'cold fusion' are still taking place on a limited basis, despite the original criticism and almost total rejection of the idea by the scientific establishment. As to solar panels in the Sahara - nice idea, but the power still has to be transported. In a similar vein, whatever happened to the proposal to use Iceland's almost unlimited geothermal energy to supply electricity to the UK? I wonder what the cost would be, compared to covering the country with wind turbines plus a few nuclear power stations to keep things going when the wind drops!

[JayPaul]

Electrostatic fusion machine, more energy out than in.

http://www.youtube.com/watch?v=ro5-QYqqxzM

[jake-the-peg]

Oh yes JayPaul reminds us of the fusor - this is one of the odd ball ones I mentioned that can't scale

A popular Phd project device

http://en.wikipedia.org/wiki/Fusor

As for cold fusion - well the scientific establishment pooh poohed it for a reason - it was fundamentally nonesense on stilts.

Muon catalysed cold fusion is another non scaling dead end.
http://en.wikipedia.o...Muon-catalyzed_fusion

There have been so many of these - yes there was too much enthusiasm in the 50s which gave fusion a bit of a bad name but since then there has been slow steady progress.

I worked in a minor role as a scientist on fusion in the 80s and since then JET achieved ignition and ITER is under construction I'm hopeful that I'll see a comercial fusion reactor in my lifetime and like the thousands of people who worked in minor roles on projects like Apollo I'll be able to say I played a very small role on this

[MoonRocker]

many thanks, very interesting

[beso]

No matter how the ignition is achieved there is still a problem with the neutron bombardment. High speed neutrons damage the structure of all known materials.

[heathfield]

I thought the purpose behind the neutron bomb was to kill off living tissue but to leave e.g. buildings and vehicles undamaged

[jake-the-peg]

Yes and no beso

That is certainly true with the reaction chain being persued right now with deuterium.

If you have access to Helium 3 you can use the H2 He3 reaction which is aneutronic and allows direct conversion

See here
http://www.visionofea...re-and-how-they-work/

However getting hold of that is another story entirey!

Not on the current agenda

[beso]

Heathfield: The neutron bomb is a one hit blast that kills living things. It isn't enough flux for long enough to break down construction materials. The flux to be contained in a reactor is enough to vaporise biological materials in a very short time.

Jake: I realise that but you surely agree that in terms of this discussion, contemplating a fuel that doesn't really exist in more than trace concentrations in particularly awkward locations is somewhat pointless

[jake-the-peg]

I wouldn't say pointless just ambitious, it may for example become prefereable and practical to generate H3 in fission reactors to use as fuel iin fusion ones.

In this way fission reactors could be located safely away from population centres.

Other aneutronic cycles exist like the Proton Boron reaction for which there is plenty of fuel readily available - the energies for this are far beyond our current reach but then the the LHC was well beyond our current reach 40 years ago

[beso]

Yet you discount muon catalysed fusion as a dead end? We could potentially discover an efficient way to produce muons.

[JayPaul]

I think all IEC reactors can be scaled if they receive enough investment for research and prototyping, considerably less expensive and with positive results in less time than ITER and NIF.
http://en.wikipedia.org/wiki/Polywell
http://en.wikipedia.org/wiki/Migma

[jake-the-peg]

The principals behind plama fusion are established as are the ways in which Helium 3 can be created in a reactor.

The challenges with these last two are engineering

The challenge with Muon catalysed fusion are scientific

We might discover all sorts of things


As for the fusor devices - I'm not sure they're as small as you think they are - the simulation in that document refers to a Q=1 (that means breakeven) at a 13 M diameter and migma preheats ions in a partical accelerator!

Although three are a lot of claims of progress this is still rather at the promises stage from what I can see

On the other hand ITER is being built *now* to run fusion reactions for up to 20 minutes.

Perhaps "dead end" is too harsh but I would suggest the chances of a sudden leapfrog by fusors are slight