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Liquid Lithium to Contain Fusion Reactors
nigelc writes: "ABCNews.com reports on Liquid Metal walls for a fusion reactor, and how it may solve some of the temperature problems. Probably only of scientific interest to most of us, unless you're into some serious overclocking.""
I used to work in Oak Ridge in the nuclear program years ago and those guys LOVE to consider using liquid metals to cool things. Back in the 1970s it was the the Clinch River Breeder Reactor, which was gonna turn plentiful inert (U-238) uranium into vast quantities of power-packed plutonium in a machine cooled with liquid sodium. Wow - CRBR never got built.
Logically, a layperson would consider a liquid metal to be a very dangerous material to have around, but if you've already got pounds and pounds of plutonium you are juggling around, sodium doesn't seem so nasty anymore. They would still be talking about using sodium if it weren't so darn reactive - read corrosive. That's where our friend lithium comes in - less reactive, less corrosive. Ha.
There aren't any electric generator turbines that run on liquid lithium pressure so there's gonna be a lithium-to-water-to-steam heat exchanger loop in there somewhere in a functional fusion powerplant. Lithium is gonna come in contact with water somehow, by accident (or design) and make hydrogen gas which is not only explosive, but turns into radioactive tritium when bombarded by the neutrons put out by ANY reactor - fission or fusion.
Playing around with explosive hydrogen gas near a reactor is often done deliberately and may be a hidden agenda here. Don't kid yourself - America needs tritium. It is a prime ingredient in nuclear weapons and however much of it you've got, you've only got half that much 12 years later. This means unless you replenish your tritium stockpile you loose half of your nuclear weapons arsenal every 12 years. So far this hasn't been a problem because we are retiring nukes rapidly after winning the Cold War and we are scavinging tritium for our online weapons from the ones we retire. Sooner or later the US will run out of recycled tritium.
We used to make tritium at Savannah River Nuclear Plant but that was closed for environmental reasons years ago. Now the US is going to refurbish that old reactor and start it back up. Sooner or later we're gonna have to switch over to something else besides World War II factories like Savannah River. When that happens, and it's a fusion reactor with a lithium core, remember that there's something else in going on with that liquid metal coolant...
The article mentions that controlling Lithium flow is the main problem of this design:
"...scientists use a magnetic field to control the high-energy plasma inside a fusion reactor. And since liquid lithium is a metal, it's tugged around and made erratic by the magnetic field.
So they basicaly have introduced a new problem by trying to solve the containment issues with a liquid metal. My understanding of previous reactor designs was that the magnetic field was so strong that the plasma never touched the walls of the containment unit and thus did not create as much of the thermal problems (neutron bombardment is another matter). So by introducing liguid Lithium into the reactor core as a sheilding agent, they solve containment but the same magnetic field now causes flow problems with the Li.
No being a fusion technology specialist, I wonder how feasible it would be to refine and control the magnetic fields they are using. Create one for the plasma and another for the Li. Would the fields interfere with each other? If so, could they dampen the plasma field to give stability to the Li? What kind of power generation is required for two fields of similar strength?
ASCII tastes bad dude.
Binary it is then.
Scientists restrict study to entire physical universe; creationist
Lithium is a lot less active (and thus corrosive) than sodium, but it's not suitable as a coolant for fission reactors because it has this pesky tendency to capture neutrons. In a fusion reactor which needs tritium anyway, this is an advantage.
Just FYI, people play around with "explosive hydrogen gas" for lots of reasons in lots of places. You'll find people playing with hydrogen in every plant which manufactures vegetable shortening from oil, because hydrogenating the oil is part of the process to allow it to solidify at room temperature. Ditto every plant which manufactures nitrogen fertilizers (which starts with fixation via the Haber process, N2 + 3 H2 -> 2 NH3).A little more information and a little less paranoia would serve you well.
Scientists restrict study to entire physical universe; creationist
This concept appears to use lithium as the "first wall". I'm not sure exactly what the first wall has to absorb, besides the heat conducted to it from plasma leakage (plasmas do leak, they are subject to all kinds of instabilities) and soft X-rays. I do know that if you had a symmetric torus you could rotate the magnets to "pump" the liquid metal along the wall using eddy-currents, but I expect that this would be far more expensive and difficult than what they're planning. You can't have two different magnetic fields; you have one field, which is the sum of all the fields induced by all the current-carrying elements in the reactor, plus whatever the Earth decides to give you (which is probably not significant on this scale). You could have a multi-pole magnetic field at the surface which would fall off rapidly toward the center (not unlike the focussing magnets used in a synchrotron) but I'm not sure what effect this would have on either the metal wall or the plasma (and unlike synchrotrons, I don't know any tokamak experts I could ask).
Scientists restrict study to entire physical universe; creationist
Making facts apparent and being clear is the journalist's job... and he's not doing it!
Have you heard of typos?
People make mistakes, this is an easy one to understand. We all (should) know that nuclei fuse in these reactors, not neutrons.
Yep, people play around with explosive hydrogen gas in lots of places....
Like KANSAS ---Farmland Industries Inc.'s fertilizer plant will remain closed while officials seek the cause of the second explosion in a week in a compressor building.
The building's safety systems contained the fire, which was fed by hydrogen gas.Lind didn't know how much hydrogen gas was in the pipeline, but he estimated it was more than the 12,000 pounds of gas that officials had said was in the system July 7.
The building was significantly damaged, although a specific damage estimate hadn't been made, said Carl Findley, the plant's human-resource director.
No injuries were reported in the latest blast, which occurred Friday afternoon as employees were resuming production in the building where a smaller explosion damaged a pipe and control systems July 7.
And LOUISIANA...Two workers were killed and a total of ten were hurt when a CF Industries fertilizer plant exploded in Donaldsonville, LA, fifty-five miles west of New Orleans. The explosion occurred in the facility's Ammonia No. 3 unit. Fueled by hydrogen, the blast did so much damage that investigators had trouble finding the exact origin. It occurred as workers were preparing an empty mixing tank.
And let's not forget FRANCE where this litle playing around with hydrogen gas at a fertilizer plant killed 18, seriously injured 49, sent 500+ to the hospital in a 3.2 Richter scale blast. Hey, the only reason it's called the Haber process is that in 1900, when the French chemist Henri Le Chatalier showed that ammonia could be formed from nitrogen and hydrogen in the presence of a catalyst, an explosion destroyed his apparatus and he lost interest in the experiment.
Realization that hydrogen explosions happen is not paranoia. Pointing out that a leak in a lithium / water heat exchanger could result in a hydrogen gas explosion in a fusion powerplant is not paranoia. I am gung-ho about building whoop-ass technology. But let's not minimize our perception of the risks we're taking by making it sound like hydrogen gas is some harmless toy like a can of Crisco or african violet food. That attitude is even worse than having dumb journalists making basic errors in their science writing.
Given the current political climate, nobody's going to be building ANY nuclear power plants in the U.S. for years to come. Even if a Li-cooled plant were to prove its superiority over conventional water-cooled plants, nobody's going to build a new reactor design outside the U.S. using unproven American technology until the Americans do it first. It's a combination of NIH and fear. Unless some other government like France or Japan does it, this will be wonderful bookshelf lining research.
And we should be using pebble bed reactors too.
If you get nothing else out of this, know that neutron absorbtion and tritium production are GOOD, not sneaky, nor nefarious. They are things we are trying to accomplish so that this will be a commercially viable technology.
From working at General Atomics in San Diego, I know that the "wall problem" is one of the few last hurdles that fusion programs will have to clear before they produce a commercial grade reactor.
So... what will this wall need to do?
First, it's there in part to seal in the vacuum chamber, but there are many ways of doing that.
Second... well, there are a LOT of things the wall has to do, but one of the most difficult, and important is that it HAS to absorb neutrons.
You point out that lithium absorbs neutrons all over the place, and that makes you suspicious. The reason they want to use lithium in liquid walls is because it absorbs neutrons! In fact, it would be nice if it absorbed MORE neutrons. They want to use lithium in solid walls, but it melts too quickly, hence, liquid walls.
We don't want those things just flying around everywhere, I would rather create some tritium than irradiate my office (and if you can feed it back into the reactor... remember tritium is FUEL for fusion plants!)
I'm sure that the engineers who will eventually design a lithium, liquid metal wall reactor will have no idea what to do with all this spare fuel they are generating. What a problem! Better just go sell it to the government, because we don't want any more fuel in our reactor.
Maybe that's what dilithium is supposed to be ...
The Raven.
The Raven
This liquid wall approach seems to be doing the same thing, but continually. Wouldn't a recycled solid wall scheme be simpler? Is there a reason it wouldn't work?
I am pro fusion, but not a fusion pro. I am confused why such reactive metals must be used for the jacket, Tin and Lead have low melting temperatures, even lower if mixed as an alloy. Not sure how reactive Gallium is, or whether Mercury would had a high enough boiling point, but there are dozens of metals, potentially infinite alloys, what huge advantage does sodium and lithium have for this proposed use? Also, do Lithium and Sodium have large magnetic properties, or do all metals react to a strong enough magnetic field? Yes I know most metals are nowhere near as magnetic as iron and nickel, but are there any completely magnetically inert? Does the liquid jacket have to be a metal? While the plasma is very hot, what will be the surface temperature of the surrounding jacket? It is my understanding that the magnetic confinement should confine most of the extreme heat, with the liquid jacket extracting thermal energy at a controlled rate for use.
Letter To Iran
You sure changed your tune pretty quick on the tritium issue didn't you?
Interesting idea, that. I wonder if there wouldn't be any non-magnetic high-temperature liquid they could use instead of lithium etc.
/. moderation model's the answer here..!
In any case, unorthodox ideas take science forwards. Unfortunately most of them are just plain bad. If there was a way to separate the unworkable ideas from great ones..
No, I don't think
Scientists restrict study to entire physical universe; creationist
One curious thing about the article was the reference to larger reactors. Another recent article on the BBC site refers to MAST , a smaller spherical tokamak design, purportedly more energy-efficient, rendering the compressed plasma easier to control. Plasma control is quite a challenge; it's described as writhing and dancing in the torus - one report I heard of was that the JET was jolted off it's supports from the contained plasma jerking about.