[cleansy]

There are already some more or less successful fusion reactors out there like Wendelstein [1] with a way smaller budget (~€1B) and that are already completed. Why does ITER need such a huge budget, long time to completion and the involvement of 7 countries/organizations to essentially proof the point of fusion energy? As far as I understood ITER is not meant to be commercially viable.

[1] https://en.wikipedia.org/wiki/Wendelstein_7-X

EDIT: originally I wrote 195 countries, which is BS of course :)

[lmm]

Wendelstein is a smaller demonstration that will never come close to producing power. It's comparable to JET which cost ~500 million in today's money.

No fusion reactor so far has achieved ignition, that is, producing more energy than we put in. Are you suggesting we just assume one would work without building one?

ITER isn't meant to be commercially viable, it's the step in between something like Wendelstein/JET and a commercializable plant. If all goes well the plan is to follow up with DEMO which will be a commercial design that can be replicated for actual power plants.

Science and engineering cost money, and investment in fusion has consistently been substantially below what scientists estimated as necessary. There's a whole bunch of materials science, control systems, and so on that needs to be done. (And while there's plenty that could probably have been done more efficiently if this wasn't a multinational project, the political reality is that no country is willing to fund such a project on its own, and everyone who contributes wants some of the contracts to go to back to their own constituents; it's not great, but politics is the art of the possible).

[pantalaimon]

Wendelstein-7X is not a fusion machine, it's only a test for the plasma vessel design.

[DennisP]

High school kids build fusors in their garages, fuse deuterium, and get neutron counts. Wendelstein certainly will as well. It'd be very silly not to, and if you look at their technical specs, you'll see that the fuel will include deuterium, at over 100M degrees, enough for plenty of fusion reactions.

http://www.ipp.mpg.de/16931/einfuehrung

Their initial tests did not use deuterium, and that gave a lot of people the wrong impression.

(For net power at this temperature they would need tritium, which they aren't using. Tritium is expensive and hard to deal with, and most fusion projects don't bother with it.)

[nomercy400]

Question by a noob: I heard they have 4 grams tritium diluted in ~770000 tons of water in Japan. Can't we use/extract that if it is that valuable? Or isn't it that hard to produce?

[DennisP]

I'm not sure but I think it'd be pretty hard to extract four grams of tritium from 770000 tons of water.

The main issue with tritium isn't the expense of getting it, but the problems you face in dealing with it. It's hydrogen with two extra neutrons; it's hard to keep it from leaking and it's radioactive.

[rkangel]

While the Wendelstein is incredibly impressive (and my personal bet for the path that will produce the first commercially viable fusion plants), it is not a fusion reactor. Or at least not yet. They have produced a plasma for a very short burst, but that's about it.

[DennisP]

That's a bit like saying an automobile is not yet an automobile, because you haven't yet put gasoline in it. Wendelstein will fuse deuterium. (It won't produce net power, but we still call it a fusion reactor if it fuses atoms.)

[rkangel]

I'm saying that calling an automobile a successful automobile before you have even put gasoline in it is premature.

The Wendelstein has so far been successful, and will likely perform fusion soon, but as yet it isn't a successful fusion reactor.