Lockheed Skunkworks hopes to have a prototype fusion reactor in 5 years

[Osmeric]

The first fusion reactors were also pretty cheap too. You can build one at home (Some people have made them for science projects).

Those are not fusion reactors, in that they don't achieve the fusion equivalent of a chain reaction (for fusion, that's "breakeven", Q=1).

Achieving fusion reactions is very easy, compared to that. But simply achieving fission reactions (without a self-sustaining chain reaction) is even easier -- they occur naturally in uranium ore, without any human intervention at all, from spontaneous fission and fission from neutron background.

---------- Post added 2013-02-20 at 01:52 PM ----------

CWell, that's because Fermi lucked out with the graphite XD imagine they had to go the heavy water route to obtain adequate moderation!

Fermi was a fiercely competent genius, so I don't think it was luck. Also, Szilard remembered that graphite was manufactured in arc furnaces using boron carbide electrodes -- and boron is a fierce neutron absorber, so even small amounts of contamination would ruin the material. He pushed tirelessly for the graphite makers to switch to better electrodes.

[Deleted]

Those are not fusion reactors, in that they don't achieve the fusion equivalent of a chain reaction (for fusion, that's "breakeven", Q=1).

Achieving fusion reactions is very easy, compared to that. But simply achieving fission reactions (without a self-sustaining chain reaction) is even easier -- they occur naturally in uranium ore, without any human intervention at all, from spontaneous fission and fission from neutron background.

You might want to check this out:
http://www.physicscentral.com/explor...s-research.cfm
A natural, accidental fission reactor, together with chain reactions and moderator.

On the other hand, as it has just been pointed out, natural reactors of nuclear fusion require temperatures like the ones that ignite stars. So it's natural that a fusion reactor should be more expensive to contain.

That means that if indeed we are unable to find materials to build a large, long-lasting tokamak, we can always make a dyson sphere and say "hey! we're using fusion power after all!"