How To Line a Thermonuclear Reactor

sciencehabit writes "One of the biggest question marks hanging over the ITER fusion reactor project — a giant international collaboration currently under construction in France — is over what material to use for coating its interior wall. After all, the reactor has to withstand temperatures of 100,000C and an intense particle bombardment. Researchers have now answered that question by refitting the current world's largest fusion device, the Joint European Torus (JET) near Oxford, U.K., with a lining akin to the one planned for ITER. JET's new 'ITER-like wall,' a combination of tungsten and beryllium, is eroding more slowly (PDF) and retaining less of the fuel than the lining used on earlier fusion reactors, the team reports."

Comments

A better first wall

[Animats]

This is known as the "first wall" problem in fusion reactors. It's good to hear there's been progress.

It's discouraging to hear how slow progress is on ITER.

Solar

[Bananatree3]

Solar is orders of magnitude simpler in technological complexity, but economic return on solar is just starting to happen. Not because of the technology, simply because population is growing and the cheaper black shit is running out.

Same thing with Fusion. Technologically, we have enough engineers and scientists in the world to make it a world-scale Apollo type endeavour and get Fusion to market by 2020-2030.... if we wanted to. But honestly, the economy doesn't want to. Not until it runs out of whatever is cheaper.

Re:Solar

[doublebackslash]

Bananatree3 likely wasn't being ignorant, but rather stating the situation simply. The economics are driven by... economics. Just because they know where more is and are getting at it faster does not mean that it is the cheap stuff that used to spring out of the ground and soak the plains of Texas and Texans alike. This oil is deeper, dirtier, and more spread out.

We are really good at getting at oil, because we need it for every piece of modern life, or at least it is the only feasible way to do it. So we get the oil, however we can.

It would have been more accurate to say, "the CHEAP shit is running out". Other than that I think it is a fine comment.

Re:Solar

[Bananatree3]

You're missing the point. I was really pointing at all Fossil Fuels too.

We'll switch over to alternative fuels long before we run out of Fossil Fuels, simply because they'll be cheaper to produce. A gallon of bio-diesel be cheaper per gallon than petrol diesel at some point, Solar will be cheaper per KWh than burning coal at some point. When that happens, the entire economy will flock over to these alternatives because of price benefits. There will probably be some economic swings as oil/gas/coal producers try to keep competitive, but they're prices will eventually be too high to compete against alternatives.

It's classic supply and demand. When exponential demand meets a finite resource, prices go up. All the alternative fuels are also finite (only so much KWh of sun can be extracted, for example) but they are also renewable. Fossil fuels don't.

Re:Solar

[bmo]

forbid some rich dude has see an oil platform...

Fucking this. God forbid they see a fucking windmill. I live here in the Northeast and the fucking Cape Wind project should have been finished 5 years ago (I may be exaggerating) but for the fucking douchebags on Nantucket being butthurt seeing windmills on the horizon TEN FUCKING MILES AWAY.

We could have a combination of wind, solar, tide, and nuclear weaning our asses off of the middle-eastern oil, but no, NIMBYism abounds. So we continue to get our asses mired in the middle east, where politics is not just a social structure, but a full contact sport with no rules and every day being a grudge match over slights done 1500 years ago.

We're fucking masochists wanting to be a part of that. We must be. No other explanation make sense.

--
BMO

Re:Solar

[bmo]

"Nuclear" includes fusion. But consider this: Fusion has been "5 years away" for 40 years.

And it will continue to be "5 years away" for another 40 years. In the meantime, we should be building fission plants based on standard designs. And we should bring back breeder reactors, so we can make more fuel out of used fuel.

But that's not going to happen because of the politics of shrill earth-firsters and others who don't understand nuclear and who think that every nuclear plant is Fukushima or Chernobyl.

--
BMO

Interesting

[interval1066]

Its a little like the old puzzle "What do you use to hold an acid that can eat anything?" Difficult, but interesting, problem.

how long will it last with homer at the contols?

[Joe_Dragon]

how long will it last with homer at the controls?

THORIUM

[sanman2]

Thorium is better, it's clearly doable, much safer, and it's incredibly abundant.

Re:THORIUM

[benjfowler]

Thorium is very heavy. This is a bad thing.

For a tokamak first wall, you want a very tough, lightweight material. Something with very few electrons to strip off when it inevitably contaminates the plasma. If you use heavy elements, loads of energy is wasted ionizing the contaminants, and the energy is radiated away.

They're using beryllium, which is a very lightweight metal, doesn't retain expensive fuel, but toxic six ways to Sunday. It melts at a low temperature, but the operators of JET have installed elaborate safety systems to prevent as much as possible, damage to the first wall.

For the divertor (the 'exhaust pipe'), they use tungsten: heavy, but has the highest melting point of any known material, and there are few worries about contamination of the plasma, where the plasma edge ('scrape off layer') contacts a physical surface inside the reactor.

These are way better than the old material: carbon composites; which are incredibly tough and don't melt or sputter easily, but trap fuel away from the plasma.

Re:THORIUM

[benjfowler]

Tungsten is used on the divertor, not the first wall, so the fact that it's a high-Z material is less relevant.

The confined plasma itself doesn't contact anything (and if it were to, it would cool down and fizzle out); the region of the interior where the magnetic field lines are closed never contact the first wall or divertor. The region outside the closed field lines, the 'scrape off layer', is drawn close to (and particles impinge on), the tungsten divertor strike plates. It's not the plasma per se; but there are still loads of hot, fast particles, and there's still the possibility of material being ejected from the strike plates. However, it will not get drawn in to the main ('confined') plasma, where the impurities can radiate energy away from the plasma. This is the beauty of the divertor configuration, as opposed to, say, limiters -- contaminants are kept out of the plasma, and ash is transported out through the scrape-off layer.

Re:My first thought... shuttle tiles

[mrbester]

What material can withstand 100,000C ???

The pastry wrapping a McDonalds Apple Pie.

Re:Fraudsters

[Anonymous Coward]

It's not supposed to work economically, experiments are like that.
Troll harder next time.

Re:My first thought... shuttle tiles

[mako1138]

Space-age materials are pretty amazing, but Fusion-age materials are at a whole different level. I think the community hasn't expressed to the public just how daunting the challenges are. Controlling the plasma is one thing, but engineering the plasma-facing components (PFCs) is a whole 'nother kettle of fish.

The so-called "first wall" is the interior layer of the fusion reactor. It has to stand up to neutron bombardment, but it also has to avoid shedding particles into the plasma. For example high-Z materials such as tungsten, molybdenum, and vanadium are interesting for their neutron tolerance, but if atoms scrape off into the fusion plasma they will radiate like crazy (proportional to Z^2) and drain a lot of energy out of the plasma. That's why they are testing a Be coating (Z=4).

On the other hand, you have divertors, which sit in direct contact with the plasma and basically hold it in place so it doesn't randomly hit the wall. These have to withstand a high heat load. I admittedly don't know much about divertors so I will stop there.

There's also the superconducting material in the coils of the tokamak to consider. Of course there's a whole bunch of neutrons flying around. But also but it turns out that a lot of the issues with superconducting magnets are mechanical in nature. The HEP community has figured out how to build SC magnets consistently, but I think the magnets needed for a tokamak are quite different.

There is supposed to be a International Fusion Material Irradiation Facility, part of the ITER project (and basically a consolation prize to Japan), that will provide intense neutron beams for materials studies. But I am not really sure what the situation/timeline is for that given the funding problems ITER has faced.

Re:My first thought... shuttle tiles

[elfprince13]

The problem isn't the temperature alone, it's also that heavy atoms will pollute the plasma if they come loose at all. The Princeton Plasma Physics Laboratory is working on a liquid-lithium walled reactor to try and handle several of these problems. Check out LTX (Lithium Tokamak Experiment).

There is no way a tokamak can be cost competitive

[InterGuru]

Twenty years ago I was a program officer at the Office of Fusion Energy, US Department of Energy. The ITER planning had started. My take -- there is no way on Earth that a tokamak can be cost competitive. Even if it works, even if the first wall problem is solved as may be indicated above, the engineering costs are so prohibitive as to price the whole concept out of consideration.

I earlier worked on Trisops, a simpler fusion concept that might be economically feasible, but I even doubt that. In the official fusion community, which is fixated on the the tokamak, it suffered from the NIH ( Not Invented Here ) syndrome and was defunded.