Liquid Lithium to Contain Fusion Reactors 42
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.""
Hooboy, Better Think Twice About This... (Score:5, Interesting)
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 [gcsechemistry.co.uk] 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 [energy.gov]. 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...
And think again, without paranoia (Score:4, Informative)
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.
Re:And think again, without paranoia (Score:1)
Wow! I'm sure there are some legitimate uses of hydrogen, but as a short list it looks like when people play around with hydrogen, bad things happen. There is hardly a more toxic foodstuff foisted on the unsuspecting public than hydrogenated vegetable oils. There is hardly an agricultural innovation that can match the nutritionally, economically, and environmentally destructive impact of the advent of synthetic nitrogen fertilizers. (no sarcasm intended)
I'd never thought about it before, but maybe hydrogen IS scary. (full sarcasm intended)
Re:And think again, without paranoia (Score:3, Informative)
I know a little about the nuclear uses of lithium. In Oak Ridge I worked on the team that documented the pollution that occurred in the program there in the 1950s when Lithium 6 was separated from Lithium 7 and purified to use as fusion fuel in hydrogen bombs. There was a step where the Lithium 6 was dissolved in liquid mercury to purify it and later recovered by reacting it with nitric acid. Over 7 million pounds of mercury were dumped into Bear Creek, then the Clinch River, then the Tennessee River, then the Ohio River and ultimately the Mississippi by lithium processing in Oak Ridge. My point remains, and it's not paranoia, that there are unintended consequences that come with the use of major technologies like this. The public would do well to keep this in mind...if only they were smart enought to, as you correctly allude to in your other post here.
I've got a permanent burn mark above my right knee where I dropped a blob of solder on bare skin and I'm still using it routinely at work and at home in building my Beowulf cluster, etc, so I assure you I'm not afraid of technology for technology's sake. The fact remains that a reactive liquid alkali metal at 600 degrees C is inherently much more dangerous than non-reactive tin and lead at 250 degrees C. Fusion powerplants of the future will almost certainly use a lithium-water heat exchanger as I stated (and you did not deny) and it's almost a certainty that THESE THINGS LEAK at times and such a leak will probably cause LOTS of hydrogen gas to form. Hydrogen gas explosions were serious steps in both Three Mile Island and Chernobyl accidents and have the potential to be one in a lithium cooled fusion reactor accident as well. Such a reactor probably wouldn't contaminate miles of countryside but the loss of the investment in the reactor would be devastating, as well as public confidence in the supposed "safety" of fusion reactors over fission ones. Such a public relations disaster doesn't occur at vegetable shortening of fertilizer plants even when they have explosions there (and they do) because those are "low-tech" kinds of plants in the public eye and they are more conditioned to think of them as "risky". Things like reactors and space shuttles are held, perhaps unfairly, to a higher standard.
Again, you post proves my point when you note correctly that sodium doesn't absorb neutrons like lithium does. It's easier in explaining it to the public to say sodium is "more corrosive" which is true. But the very fact a fusion reactor group would pick lithium instead of sodium for the coolant shows that somewhere along the line, neutron absorption and tritium production is important...the "hidden agenda" that is neither paranoia on my part or even hinted at in the ABC article.
Re:And think again, without paranoia (Score:3, Interesting)
Your obsession with hydrogen is misguided anyway. The reaction is
The problem is that the hydrogen is liberated rapidly, making the system explode from overpressure, which causes an overpressure wave (explosion) and blows chunks of hot nasty stuff everywhere. Afterwards the hydrogen might burn a little in the air, or even cause a gas explosion, but that's minor compared to the explosion of the piping and pressure vessels. If the reaction liberated nitrogen it would be just as bad. There are very few, if any, unintended consequences in any industrial operation. The bad things you are talking about are predictable and manageable. The only unknown is the will to proprely address them. Yeah, but those were fission reactors, which have to be as strong as possible because fission ash is so dangerous. The high strength of their pressure vessels and pipes means that more pressure can build up, producing a more spectacular explosion. A fusion reactor is vastly less radioactive, and its systems can be made deliberately weak so that they explode at a lower pressure, causing less damage. I suspect you strongly underestimate the political fallout from uncontrolled energy releases at chemical plants, and overestimate panic from 'nookyular radiation'. 1) There is no "hidden agenda". The fusion reactors will probably burn a deuterium-tritium mixture. If they didn't breed tritium, you'd need accelerators or fission reactors to get the tritium. If they make their own tritium, you can feed them with deuterium from tap water and lithium, both of which are fairly plentiful and innocuous.2) Tritium for boosting plutonium bombs? Big deal. Any nation that can afford plutonium and ICBMs can afford tritium no matter how it's made.
Re:And think again, without paranoia (Score:2, Informative)
Well, you are wrong on this as well. The proper reaction is something like this:
alkali metal (M) + 2 H2O --> alkali hydroxide (MOH) + H2 + heat
Re:And think again, without paranoia (Score:2)
Here's another reaction: write equation in haste --> look like fool in public.
Re:Lets try a little logic here (Score:3, Insightful)
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.
Better, don't make what you don't need (Score:2)
Re:And think again, without paranoia (Score:2)
What Paranoia? (Score:2)
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 [bbc.co.uk] 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.
Re:And think again, without paranoia (Score:2)
Flow problem (Score:2, Informative)
"...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?
This isn't the first concept to use lithium thusly (Score:3, Informative)
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).
This is science journalism? (Score:3, Insightful)
Re:This is science journalism? (Score:2, Offtopic)
Amen, brother, preach on. Last night a fellow slashdotter was wondering when a supernova in a distant galaxy went off and actually stated "...so it stands to reason it actually took place days, weeks, or even months ago" [slashdot.org]. I am VERY concerned that the average slashdotter is an absolute computer whiz that has no feeling at all about basic scientific reality. Maybe this is why we have guys writing code that crashes orbiters on Mars because there's no inherent gut-feeling perception of difference between meters and miles? Or that write code that cut off the Mars lander engines when a switch is closed, and never considers that the switch accidentally gets closed by the jolt of the lander legs opening instead of contact with the Martian surface? Both of these actually happened, of course...
I dunno, it just makes me nervous to go in a bookstore and see miles of shelves on computer topics and one little corner of science books that never get looked at. Or to see a slashdot posting on Tivo get 200+ comments and one on fusion reactors get less than 10 comments less than an hour later....
Re:This is science journalism? (Score:1)
Re:This is science journalism? (Score:1, Offtopic)
One comment and one moderator. From that you're drawing conclusions about "the general population" of Slashdot? Awfully anecdotal evidence to draw conclusions from... what were you saying about science?
How about looking at the whole thread [slashdot.org], in which several readers (who have been moderated higher) point out the error, correct it, and provide three links to interesting websites about interstellar objects and distances. Or do you prefer to focus only on negative anecdotes?
Re:This is science journalism? (Score:1)
at least for us non-editors.
Re:This is science journalism? (Score:2)
Re:This is science journalism? (Score:1)
Re:But you forgot (Score:1)
Re:This is science journalism? (Score:2, Insightful)
slow down (Score:1)
People make mistakes, this is an easy one to understand. We all (should) know that nuclei fuse in these reactors, not neutrons.
Mostly of academic interest (Score:1, Troll)
Re:Mostly of academic interest (Score:1)
The main method of Magnetic Confinement Fusion (the article subject) is to confine the plasma in a tokamak, Russian technology.
Most fusion technology can't be said to be "American". Even in cases where it is developed in the US, there usually is some visiting scientest from Japan or Europe who is part of the team.
The US hasn't built any next generation fission reactors either, although they are popping up all over the place in the rest of the world.
Don't assume.
pebble bed (Score:1)
Re:pebble bed (Score:1)
Lithium (Score:2)
The Raven.
Brittle walls (Score:2)
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?
Re:Brittle walls (Score:1)
Why Li and Na? (Score:3, Interesting)
Re:Why Li and Na? (Score:3, Informative)
Also, the key reason (which isn't even mentioned in the ABC article) for using lithium is that when lithium is hit by the fusion reactor's neutrons, it will change into radioactive tritium gas, which is a rare fuel the fusion reactor needs to keep going. So you start the reactor with a little bit of tritium you got someplace else, then use the reactor's own neutrons to convert common metal (lithium) into the rare fuel you need to keep it going. No other metal - sodium, lead or tin included - will do this, only lithium.
You are the smartest person in this whole thread, pal - instead of showing your ingnorance by stubbornly defending a particular position with facts (me included), you openly admit the things you don't know and ask intelligent questions to make yourself more knowledgable. Do not ever lose this open mind you have - it is much more rare than tritium gas.
Re:WTF? (Score:2)
Ideas.. (Score:1)
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