The Bizarre Reactor Scientists Hope Will Save Fusion Research (sciencemag.org)

sciencehabit writes: In a gleaming research lab in Germany's northeastern corner, researchers are preparing to switch on a fusion device called a stellarator, the largest ever built. The €1-billion machine, known as Wendelstein 7-X looks a bit like Han Solo's Millennium Falcon, towed in for repairs after a run-in with the Imperial fleet. Stellarators have long been dark horses in fusion energy research but the Dali-esque devices have many attributes that could make them much better prospects for a commercial fusion power plant than the more popular tokamaks: Once started, stellarators naturally purr along in a steady state and they are not prone to the potentially metal-bending magnetic disruptions that plague tokamaks. Unfortunately they are devilishly hard to build.

Comments

Re:Q: heat

[benjfowler]

Heating (and confinement) are now basically solved problems in magnetic confinement machines. The Wikipedia article says that they'll be using bog-standing microwave heating (they don't say exactly what), and neutral-beam heating in W-7X.

Both tokamaks and stellarators have to 'twist' the magnetic field around the torus (since paths around the inside of the torus are smaller than the outside, leading to instabilities). Tokamaks achieve this by inducing a current through the plasma to induce the twist in the magnetic field using a huge solenoid or other means; stellarators use external coils.

The former are prone to catastrophic disruptions (which in extreme cases, can unleash strong forces that could, in the absolute worst case, physically break the machine); the latter are more stable, but much harder to manufacture.

Re:Dat Title

[fisted]

Dat device tho.

Re:Even if ITER or W7X works, is it economical?

[Anonymous Coward]

The bullet points where you give numbers make no sense. 10000 tons of lithium? Design studies for DEMO, which would have several GW of thermal output, have a blanket volume on the order of 500 m^3. Even if assuming that was all lithium, you are talking about 300-400 tons, much smaller than 10000 tons. 10000 tons would be a block of lithium about 27 m on a side, which is much larger than the whole reactor vessel design.

Scaling the costs is very difficult to do. A production reactor would be far cheaper in many ways, because you don't need as much diagnostic access. A lot of compromises have to be made to just get enough space between the magnets of many designs for diagnostics, plus the costs of diagnostics (millions of dollars each for the many of them), plus the costs to use, maintain and analyse them. This is part of why designs for DEMO are only about 15% larger than ITER, but of a much more compact design considering it is producing nearly 4-8 times as much thermal output.

Re:DOE report says fusion is likely uneconomical

[Zak3056]

Wind and solar will never compete with coal and fission.
But actually they do. In Germany coal planets get decomissioned because they can no longer compete.

The reason that coal is not competitive in Germany is because the playing field is severely tilted in favor of wind (wind power gets a premium price that is, IIRC, funded by fossil, and also has priority in the grid. If there is renewable available, the fossil plans have to spin down). That climate makes it absolutely uneconomical to run a large powerplant that is slow to respond to changes in supply and demand.

Please note that I'm not saying this is necessarily a bad thing (though some of my German colleagues think the situation is untenable for various reasons), but your argument above is not nearly as simple as you frame it.