Slashdot Mirror
Fusion Plasma Plant in The Future
NightWulf writes "The BBC reports that Europe and Japan are currently looking to host a new JET power plant. This new plant creates plasma, which is akin to creating a star on Earth. Interesting to note that 1kg of fusion fuel would produce the same amount of energy as 10,000,000kg of fossil fuels."
In the same sense, my logging on to slashdot today is akin to designing TCP/IP.
Reality has a conservative bias: it conserves mass, energy, momentum...
Step away from the car... This is a fusion research reactor, not a reactor to be used as a power source...
does this solve the energy problems?
Do you need a website upgrade?
One kilogram of fusion fuel would produce the same amount of energy as 10,000,000 kg of fossil fuel.
How much energy do they estimate it will take to create (and control?) that one kilogram of "fusion fuel"?
Casual Games/Downloads
Wow, I had no idea fusion power was so far along.
It would be the first fusion device to produce thermal energy at the level of conventional electricity-producing power stations, and would pave the way for commercial power production.
This is awsome. Expensive for the amount of power though. Anything that can reduce our dependency on oil, deserves some research in my eyes.
Of course, fusion is better than fission in this regard, but the same arguments hold in either case.
"He who would learn astronomy, and other recondite arts, let him go elsewhere. " -- John Calvin, commenting on Genesis 1
Well taking that you get left with helium its obvious that a by product will be a market for baloons
Rus
Cheap UK and US VPS
you idiot. Fusion can not go Chernobyl, and the only radio activity is the Neutron bombarded walls of the chamber which dissipate quickly enough to not be a big problem
I am the Alpha and the Omega-3
Slashdot has a strange fascination with potential energy solutions. Ah...so much energy wasted thinking about potential energy.
...is how much energy it will take to maintain that 100 million degrees Celcius temp for 500 seconds or longer. Sure, 500 megatwatts sounds awesome, but fusion reactions are historically extremely difficult to maintain as the plasma constantly bumps into the container and kills efficiency. That being said, more research into the field is a Good Thing(TM).
why? vented Plasma is not toxic.
read about Fusion from Wikipedia please and cure your ignorance before you start some crazy anti-fusion lobby
I am the Alpha and the Omega-3
I would have thought that decision to build the project in Japan would have been unanimous. How else could Gozilla be resurrected?
Chewie does not get a medal. Come on, George. Can a Wookie get a medal?
50-100 years is way better than tens of thousands of years, as with fission waste. That won't outlast the containers it's in.
I'm in the hole of the broadband donut.
If anyone is interested there is a wealth of information on JETs website
Including some pretty cool pictures of their kit.
Why was this modded Funny? It's the truth. A fusion reaction is hard to keep going, and if just about anything goes wrong, the reaction will die. Somebody detonates a bomb next to the reactor? Fine, so the thing gets jolted. The worst that could happen is that the reaction is disrupted slightly---and it stops. There is not much excess reactivity in a fusion reactor. Just because something uses a process used in bombs doesn't mean it is a bomb. Gunpowder contains sulfur; does this mean that rotten eggs are an explosion just waiting to happen?
50-100 years is nothing, and it's not the fuel or exhaust that you need to worry about, only the parts of the reactor itself that become radioactive from neutron bombardment. So, we only need to store retired reactor parts for 50-100 years, which is much less mass and much less duration than what we currently produce from nuclear plants, and massivly less environmental impact when compared to the equivilent fossil fuel usage.
Goodness -- I was surprised by the number of wildly incorrect postings about nuclear fusion. Some I could have tried to clear up myself, but a better recommendation would just be to read up for five minutes before posting some misinformed comment.
Wikipedia has a good article on Fusion Power. Read it, then post.
Not much. The waste produced by a fusion reactor is helium - probably the most harmless stuff you can get. The process of fusion produces neutrons, so the fusion container itself will become mildly radioactive, but nowhere near the kind of nastiness you get with fission.
In addition, fusion is inherently fail-safe. If something goes horribly wrong with a fission reactor, you can get a runaway reaction. Meltdown. Not good. But in a fusion reactor, you have to carefully maintain the right conditions for the reaction to happen at all. Screw up and the light goes out, that's about it.
Real Daleks don't climb stairs - they level the building.
Nope - helium isn't toxic.
But helium at 100,000,000 degrees celsius might have slightly different effect if you tried to use it to make yourself sound like a munchkin...
'Don't worry' said the trees when they saw the axe coming, 'The handle is one of us.'
I would hope these same scientists would also be looking for a way to tap the energy off the reaction vs superheating turbine water. How much energy is wasted in the conversion process that could be better tapped through other methods.
Only on slashdot can you be called an idiot if you don't know anything about nuclear fusion.
But since when do we power our power plants with oil?
We will always depend on Arab oil in some way or another.
Oil is used to make plastics, and from what I see it seems like everything is made out of plastic.
American cars for one.
So the Arabs will find a way to still charge $100.00 a barrel.
I think perhaps you don't grasp the fundamentals of what a magnetically confided burning plasma reactor really means. While a reactor of this sort aims at providing net power production via nuclear fusion, you have to be aware that a significant amount of energy is used to create the magnetic fields, and other auxillory control mechanisms like nuetral particle beams and radio/microwave power used in controlling the plasma to get the very precise conditions under which net power can be achieved. You turn off any of these control systems..the plasma start under performing. Unlike fission, you aren't trying to control a run-away process by slowing it down. In terresterial magnetic confinement fusion reactors..you are doing everything you can think of to produce the very specific conditions that maximize the amount of nuclear reactions. And if the plasma conditions change or your control system fails, plasma performance quickly degrades on its own because of naturally occuring instabilities in the magnetohydrodynamics that govern bulk plasma behavior.
Nothing like a world ending 'meltdown' can happen, a magnetically confided plasma has so many different ways to dissipate energy. The trick has always been and always will be to get enough nuclear reactions out of this plasmas to make it worth while to build them as an energy source, becuase running them invovles using lots of energy just to create the plasmas conditions at all.
Wikipedia has a solid list of the containment types. This helps illustrate way it's just so hard to keep the reaction going.
"The most advanced test reactors, the Tokomak Fusion Test Reactor (TFTR) in the U.S. and the Joint European Torus (JET), use the tokomak design and have come close to break even conditions. In fact, in November, 1991, the British-based Tokomak reported break even conditions. This occurs when the energy given off by the fusion reaction is equal to the energy input required to sustain the reaction. In order for a fusion reaction to generate useful amounts of electricity, the energy given off must be many times greater than that required to sustain the reaction. Even the most optimistic researchers feel that it will be well into the next century before this stage is reached." (from This site)
No need for us to prove it. You can do it yourself. The equation is E=mc^2. c is a really big number.
How can we continue to believe in a just universe and freedom to eat crackers if we have no ale?
and the only radio activity is the Neutron bombarded walls of the chamber which dissipate quickly enough to not be a big problem
What do you think happens to the Neutron bombarded materials? (Hint: They can become radioactive.) Fusion produces a tremendously strong neutron flux. So strong, that very few materials survive being near the process. Obviously, your choice in containment materials can make all the difference in HOW radioactive we're talking.
Personally, I don't think we'll quite get the hang of fusion inside Earth's gravity well. Once in space, we can allow the Fusion to bleed off its neutron flux like the Sun does. Thus it might be very useful for space-based power generation and propulsion. But here on Earth, fission is a much more viable energy source. Our biggest problem is that most of the reactor designs are from the 50's and 60's, when we were just starting to understand nuclear power. With hindsight firmly in place, plus ~500 commercial reactors, a hundred or so military reactors, and a few hundred research reactors currently in service, we have the knowledge and technology to create very safe reactor designs. Hell, just removing the 19th century boiler design out of the equation makes something like Chernobyl impossible.
The real problem right now is government fear over terrorism. The U.S. government forces plants to keep potentially useful materials sitting in pools of water or buried in the ground instead of being used in commercial ventures. Some of that stuff can be reprocessed into nuclear fuel, and some of it has uses in medical, electronic, and aerospace fields. None of it is useful to "terrorists" until it's reprocessed into fissionable fuel. (Don't get me started on the uselessness of a dirty bomb.)
Javascript + Nintendo DSi = DSiCade
The plasma is VERY thin... and there's a reason why they have to try very hard to keep it away from the reactor walls. Not because the walls will melt but because the plasma will instantly cool down and stop doing its fusion thing.
"Studies have shown that people who eat peanuts live longer than those who do not eat."
Iter - latin for "road" - is the next stage, but not the final.
It will produce more energy than put in, will will not create electricity as such.
"Creating" electricity, as a normal powerplant does, will be the next stage. As in DEMO.
So another year before knowing where to build iter, it should have been decided long ago. A few years to build it. 20 to 30 years of research. A few years op political maneuvering for deciding demo, building and doing research for another generation.
So 50 or 60 years before we have an electricity producing fusion plant.
If they have to vent tritium (used in the reaction) and you are are you are near enough to breath it in you will be somewhere between deeply fscked and completely fscked. This is why everyone stays inside when they are running experiments :)
For a brief primer, read this article.
I'm not tense. I'm just terribly, terribly, alert.
One of the problems with previous attempts to build a fusion reactor is that they couldn't keep it running for more than a few seconds. The holy grail of fusion physics is to build a reactor that can maintain a sustained reaction; and, does so without requiring more energy input than the amount of energy produced in the reaction.
But whats the possible damage if one of these plants pulls a Chernobyl on us?
Well, the most significant damage would be to our understanding of physics, since there is no possible way that a fusion reactor can "run away" like a fission reactor can.
Think about it this way: for a fusion reaction to happen, the outside control is critically important: in typical designs, the control is provided by huge electromagnets (magnetic confinement) or by powerful lasers (intertial confinement). If the reaction did somehow get "out of control," the first thing that would happen is that the control systems would be destroyed, and there would be no way to keep the reaction going.
Compare this to a fission reactor, where the reaction can proceed without any outside control whatsoever (for example, the natural uranium reactor in Russia or wherever that was). That is why there is so much effort currently put into designing "passive safety systems" for fission reactors - which are basically hacks that make a fission reactor behave as if it could not work without outside control.
Honestly, if it were so easy to get a runaway fusion reaction (in non-bomb form), don't you think we would have achieved one by now?
After the slashdot story a few weeks ago on the NASA Institute for Advanced Concepts (sorry, I'm too lazy to go look up the original Slashdot reference, but at least I'm honest about it), I started reading a lot of their proposals and most of the ones regarding how to handle interstellar travel involved anti-matter.
;-)
I started thinking about that and the two biggest problems with that are: A> It takes a huge amount of energy to create anti-matter, a hell of a lot more goes into the production than comes from using it. B> We don't really have a system for containing significant amounts of anti-matter.
So I started thinking about alternative energy sources and one of them was fusion. Pound for pound, fusion produces about 1/27th of the energy of anti-matter (based on my naive calculations, so I may be way off) whereas other types of fuel are several orders of magnitude less efficient.
To me, that makes fusion a pretty good option. The only problems I have encountered so far with the idea are:
1: Fusion isn't quite ready for real applications, though by the time we're capable of sending an interstellar craft, I believe it will be.
2: For an interstellar journey, you'll need a power plant that can survive for no less than decades, if not centuries, without maintenance. That's a serious issue given the harsh environment it would be operating in.
I'm sure there are additional problems I haven't thought of yet, but I'm still thinking it might be a good option. Perhaps some sort of self-repairing reactor could be built to solve #2.
But another huge advantage of hydrogen is that you could collect fuel along the way using the Bussard Ramjet idea. You'd just need a way of separating out deuterium and tritium from the hydrogen that doesn't suffer from problem #2 as well, but it should be doable. As most here are probably aware, fuel mass is a serious issue for space travel.
Anyway, I think fusion has a great deal to offer in a number of ways. Maybe I ought to work on my NIAC proposal
If you're interested in some of the specifics, a little googling turned up this, which talks about fusion in relation to the sun. The number that they cite is actually a factor of about 1:1 billion. (It depends, of course, on exactly what fusion fuel and fossil fuels you're talking about.)
How can we continue to believe in a just universe and freedom to eat crackers if we have no ale?
It's an OO thing. The attraction of moving to electric or hydrogen-cell cars isn't so much that these are more environmentally friendly *right now* as that it provides a potential for a vast environmental-friendliness advantage because it decouples the method of energy production from energy use.
Yeah, at the moment this electricity or hydrogen would be probably just generated using fossil fuels. But the catch is it doesn't *have* to be. You could substitute a nuclear power plant for that coal-burning one and the electric cars would continue to run just the same... it makes productive change much easier. Whereas if you buy a gasoline-based automobile, it's going to be running on burned fossil fuels forever*.
* Unless you are Doc Brown and you do some retrofitting.
Irritable, left-wing and possibly humorous bumper stickers and t-shirts
Aside from the initial jumpstart of energy required could it not sustain itself afterward using its own energy, perpetually maintaining itself once stability has been established?
Keeping the plasma hot enough for fusion to be possible is only part of the picture; you also have to solve the confinement issue. You not only have to keep the ionized plasma confined (and no, a material "containment vessel" similar to what's used in fission reactors doesn't work; you need something nonmaterial, such as strong magnetic fields), you also need that confinement to be within a very small volume for reaction rates to be sufficiently high (for any kinetic "collision"-ish process, reaction rates are proportional to the square of the density). Heat is necessary for the nuclei to be moving fast enough for fusion to take place; but heat is also the enemy of keeping the plasma at high density.
Yes - but only just and only in small volumes and for a short time - the glow in the balls is the plasma recombining. Those plasmas are created in small volumes at room temperature by stripping the odd electron of a heavy molecule using electric fields. The plasmas for fusion are at millions of degrees, well above the point where thermal effects knock the electrons off. Comparing these with a fusion reactor is like comparing the forost on your car on a cold morning with the Antarctic Ice cap. Sure, they are bot ice - but that is about all they have in common.
Consciousness is an illusion caused by an excess of self consciousness.
I think you are way off base. Fusion power would not end energy companies. I doubt it would even end fossile fuel exploitation. Oil gives more bang for the buck then any other fuel source which is why we are so addicted to the damned stuff. Bonus points for the fact that it is cheap and easy to make an engine that will run on it.
Now, fusion offers a great deal of possibilities, but there are two very large problems with it even when it is 'worked out'. First, it will be expensive. It is a major task to build such a plants. Building enough to power the world would take many decades and cost far more then I imagine most nations would be willing to spend. I am not saying that it couldn't eventually be done, but don't expect it to happen over night. Further, even if the world was covered in fusion plants, that energy would not be free. You still need to pay for all the parts and labor it takes to keep such a plant going. Sure, you might cut costs on material expenses, but they would rise everywhere else. Electricty wouldn't suddenly become cheap, just abundent. Second, fusion is large. You can't throw a fusion engine in your car and electric motors just don't have the capacity of a gas engine. If electricity was free tomorrow we still wouldn't hav electric cars.
I doubt energy companies are cowering at the prospects of fusion. Even if fusion was to completely upset the need for oil and coal, there is still the fact that people need energy and in a nation like the US that energy is going to be brought by a corportation. An energy company is in a perfect position to fill that need. At worst it means they have to shift their bussiness to focus less on oil and coal and move to fussion. The world won't end for them.
Let me point you to the sun as an an example of what it takes to keep fusion conditions viable over long timescales without extra energy input. Thats a hell of a lot of mass to produce the gravitational energy to keep a burning plasma self-confined, not to mention the large scale bulk motion of the solar plasma that is still not completely understood that allows the sun to create its own magnetic field via a dynamo effect. Regardless of what the open scientific questions about how our sun and other stars operate, few if any competent researchers will argue that a self-sustaining magneticially confined plasma is something that can be created on earth, simply because of the scales invovled to produce a dynamo. Earth's core for example, is probably a good example of the amount of material needed to produce a dynamo..and thats not even a fusion plasma..just a magnetic dynamo..getting to the much higher pressure/temperature conditions required to produce a self-sustaining magneticlly confided plasma will require stellar mass.
-jef
Would you want this venting on Wall Street?
Better there than many other places I can think of.
http://xkcd.com/386/
I don't know, but if you think it even approaches 10000000 kilograms of fossil fuels, you need to get your head checked.
Another way of stating what you have said is that plasma fusion requires intervention to sustain the reaction, whereas the current generation of fission based power plants require intervention to restrain the reaction.
Fission is a stable reaction, fusion is very unstable. The difficulty in sustaining fusion is due to the fact that it is so hard to sustain the conditions under which it will occur.
The implications for safety are obvious: current generation fission designs require all kinds of redundant safety systems to prevent an ongoing and very dirty accident. Such systems would not be needed in a fusion reactor, becuase the least hiccup, such as weakening of magnetic containment or the leaking of tiny amounts of contaminants into the reactor would cause the reaction to collapse. There is no possibility of anything like the reactor catching fire driven by the heat of a runaway reaction.
That said, I'm skeptical we're going to see practical fusion in my lifetime, because it is so difficult to sustain, although you can always hope. A more promising technology would be a stable fission designs, that would require intervention to maintain fission, or which would only output heat at a limited rate.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
Correction, we are addicted to oil until such point that is becomes uneconomical to do so. At which point, it would probably be natural gas for a few years until we realize we hadn't built enough refineries for that either. And the fission people will be saying, if you had only built any plants in the last 30 years... but noone will listen. The whole time, there will be thousands of other people pointing at all the resources buried in the ground and off the coasts, untouchable due to self-imposed regulations.
By then, I wouldn't be surprised if we switch back to coal, given the advances in plant designs over the last 30 years. That's a fuel that the eastern US has an overabundance of, yet is frowned upon by the environmentalist lobby because of the tendancy of existing plants to just vent the waste products into the atmosphere. Good thing the DoE is already working on it. It's amazing what the free markets can provide, when you let them work...
Exactly. Let me spew some physics for a moment.
The temperature of a gas is related to how fast the particles of the gas are moving. The hotter the gas, the faster the average kinetic energy. However, not all the particles move at the same speed. There is a distribution of speeds, with most of the particles at or below the average speed. However, a very thin "tail" of particles travels at speeds much, much higher than the average. In the Sun, it is these very high-speed nuclei, way above the average kinetic energy of the plasma, which collide and fuse.
So, why can't we get fusion with temperatures equivalent to the center of the Sun? Pressure. We can't hope to achieve pressures anywhere near that in the Sun. In the sun, the pressure is so immense that the particles are squeezed extremely close together. Imagine these particles moving at insane velocities, in such close quarters. They will collide with each other extremely often. This extremely high collision rate allows fusion to occur, because it brings the super-high-energy nuclei together more often.
On Earth, at very low pressures (at least relative to the core of the Sun), the particles are moving fast enough to fuse, but they just don't collide often enough. They aren't close enough together. Thus, to make up for this, we must increase the temperature so that a larger fraction of the particles are in the kinetic energy realm where fusion can occur. In other words, we make up for the lack of pressure by increasing the temperature.
A quick Google reveals a current price of about $300/kg for heavy water, which must include the energy costs of separating it. Deuterium is 4/20 of this, so about $1500/kg for pure deuterium. Prices will probably fall with real mass production.
Consciousness is an illusion caused by an excess of self consciousness.
Seastead this.
Actually, you have it backwards on fission. Fission is also an unstable reaction; the difference is the following:
Fusion reactions occur at an energetic peak. Basically, for fusion, we're trying to balance a ball on top of a hill. If we lose our balance, the ball rolls down the hill and the energy production ceases.
By contrast, fission reactors operate at an energetic low (this is simplifying, but true for illustrative purposes.) We're trying to stay in the bottom of a valley, while the reaction tries to force us to climb up the walls. If we lose our balance, the reaction can shoot up a wall and then you get meltdown.
notes on this: fission reactors can be designed to be negative coefficient, such that an increase in output leads to a cycle that will decrease output, but the reaction itself is still positive coefficient.
---
Mod me down, you fucking twits. Go ahead. I dare you.
(I read with sigs off.)
I think the correct plea is please, please, please, nobody tell the environmentalists about it.
This has the word nuclear in it. The nuclear boogieman will derail this a lot faster than anything else.
For example, the correct term for and MRI is Nuclear Magnetic Resonance Imaging. The nuclear here has nothing to do with nuclear power, it just means that the magnets make the nuclei of the atoms move in certain ways and that the images are created by iterpreting those movements. The Nuclear part was dropped because people were worried about radiation.
It really won't matter to the fanatic environmentalist how safe this is, it has the word nuclear in it, and thus is to be fought.
I'm confused on two points here. First, why this was deemed, "insighful", and second, what christians have to do with the subject at hand.
Last I heard, "christians" mainly get negatively involved in life sciences. I'm not sure how this relates to the topic at hand or why it would even be a concern. Especially since this is heavily a physics topic and not a life sciences topic. Worse, even if it were a concern, why would it matter. Unless you have proof that fusion creates souls, no one but zealots are going to listen to these crackpots anyways.
This could be a useful technology, please, please, please, nobody tell the christians about it.
Now, for some karma whoring. Since his comment was deemed karma worthy, surely my comment will make as much sense and someone with reward me accordingly. So, here goes. This could be a useful technology, please, please, please, nobody tell the inanimate carbon rods about it. We all know how involved in physics they are.
Was his comment supposed to be a joke which simply missed its target?
Oh, and as an added bonus for geeks in that area, they have a public open house coming up on June 12!
I'll add that the reason a star can sustain fusion is because of the immense gravity involved, it keeps the hydrogen (well, there are others, but those are later in a stars lifetime) compacted, and the force compressing them generates the heat needed for fusion.
As we can't create miniature stars at the moment, we have to compensate by supplying the heat and containment ourselves. One of the major barriers to a useful fusion reactor is getting it to produce more power than it draws.
The part that becomes radioactive from neutron bombardment is called the "reactor vessel". It weighs about 1000 times as much as the fuel in a fission reactor. The irradiatted iron/nickel/chromium/cobalt/whatever-else-is-in-yo ur-alloy-of choice has a much shorter half-life, and this is far more radioactive than the spent fuel rods.
You'd probably get more irradiated metal in a fusion reactor than a fission reactor, though this no doubt depends on design details. But the neutron flux will be higher, per watt, so expect it to tend toward more radiatted metal rather than less.
In other words, don't expect fusion to be cleaner than fission. There'll be a different mix of radioactive byproducts, but it is by no means clear that there will be less, or that said byproducts will be easier to dispose of.
"I do not agree with what you say, but I will defend to the death your right to say it"
"Helium causes death??? Come on; get real. Helium is an inert gas (if you don't know what inert means, look it up). It is not a poison and it cannot hurt you by breathing it. Divers use a mixture of helium and oxygen when they go deep because pressurized nitrogen is poisoness. The only way that helium could hurt you is if you were breathing pure helium (no oxygen). You would pass out and eventually die from a lack of oxygen not from any property of helium. This is true of any gas that you might breath that does not contain oxygen.
If you are sucking on a helium filled balloon and start to get light headed, just pull the balloon out of your mouth and take a breath of normal air. If you don't stop sucking on the balloon when you get light headed, you will probably drop it when you pass out and the problem will fix itself."
Please stop spouting Urban Legends that have no validity.
Please don't paint all environmentalists with one big brush!
I like to consider myself a "green" kinda guy. I recycle, don't drive a SUV, etc. However, that said, bring on the nuclear power plants (provided we can properly secure them from whoever may want to crash a small plane into them... another story tho). Nuclear power is much cleaner than coal power, and the waste, while icky, isn't produced in huge quantities.
Some environmentalists will agree with me, some will disagree. But don't paint everyone with the same label. That'd be like me saying that most republicans are christian conservatives who want to turn the United States into a Christian version of Iran.
See how annoying that is?
Currently, the DOE has so many clean up sites, not because the nuclear energy projects were not successful and profitable, but the fact that the DOE is required, COME WHAT MAY, to take care of any finality issue with a nuclear based energy company. So the companies have a whopping zero cost for failure or liability, and remember, we're talking nuclear.
So, when they think their operating costs get too high, or they just don't want to do it anymore, the nuclear companies can literally drop what they are doing right there, walk out, and it is all a Department of Energy (DOE) problem from then on. Guess what? DAMN NEAR EVERY ONE OF THEM DOES. That is their little perk. This stuff is too dangerous without permanent government supervision. The US doesn't want some weird Iranian group that they don't trust buying up their workplace (because if anyone is going to sell something to Iranians we don't trust, by god, it should be bought direct from the US government), and after all, businessmen don't care what they have to do as long as they get the cash for doing it. So, as a protection, they have no responsibility for their nuclear actions.
"We leaked some sludge? WHOOPS. That's it, it is now too expensive with the lawyers. Close shop. Call the DOE. It is their child now. Thanks for the BILLIONS, and see ya later, suckers!"
The best analogy would be that the government would now be responsible for auto manufacturing recalls. "Sorry we made some bad cars. Call the government, it is their problem now."
There are some fission designs that require active intervention to remain active, and have been in active production in Germany and South Africa.
c to r
My understanding is that these designs have been ignored in the US due to the costs to get approval from the Nuclear Regulatory Commision are too high.
http://www.wordiq.com/definition/Pebble_bed_rea
plus-good, double-plus-good
I don't think that was the question the poster asked at all. Its a very complicated process to turn the nuclear energy released in a plasma back into electricity, and requires a metric buttload of human effort.
The goal of course of any fusion reactor is to get enough energy out than it takes to produce the fields and other things...to produce net energy that can be put to use. The point at which this happens is called break-even, there is a handy dandy ratio called Q=power-out/power-in that gets used to describe the reactor power. Q=1 is break even...the reactor produces just enough energy via nuclear reactions to make up for the energy needed to be spent by humans to power the reactor. Of course what goes into defining Q is sort of dependant on who you talk to. The efficiency of turning the energy released in the nuclear reactions into electricity is a matter of debate. The process we do most efficiently is turning steam into electricity...turning fast moving energetic nuclear particles into steam is something we aren't really good at doing. Anyways...i digrest.
The point at which a plasma is self-sustaining is Q=infinity and is called ignition. Plasmas that ignite, don't need external power sources to continue their fusion processes. They go about their business all by themselves if given a supply of fuel.
Production reactor designs aim between something like Q=5 to Q=20. At first glance a higher Q value would seem to be a better thing. But actually it isn't. Q isn't just a measure of how much net power your are getting out, but its also a measure of how much control you have over the plasma itself by external means. It could very well be the case that the most economical reactors long term are ones that can be better controlled at Q=5 than higher performing Q=20 reactors.
-jef
http://www.nrel.gov/geothermal/geoelectricity.html
Prolonged neutron bombardment makes many metals brittle. Fortunately it is a relatively well understood phenomenon which is familiar from the operation of current reactors - some of which have run for over 40 years.
Fusion reactors can expect some embrittlement with time, but the consequences are much less likely to be serious than with a pressurised vessel such as a PWR.
The biggest problem will be that the plant will have to be mothballed for a period before dismantling at the end of its life. Again that is something we know about as the US and UK are already dismantling their first generation of nuclear reactors.
Best wishes,
Mike.
Except:
1: Fossil fuels aren't necessarily fossil. It's possible that oil is produced in a way that doesn't involve life. Abiogenic theory might turn out to be correct after all. Remember how in the 1960s everyone believed "the oil is going to run out in forty years"?
2: We're not choking as much as you think.
3: There were despots in the middle east before the Oil Age began.
4: If TMI was (if you will excuse the pun) blown out of all proportion, what about Chernobyl?
I agree that the anti-nuclear lobby can be mischevious, but that's one of the aspects of lobbies. At the other extreme, arguing that if we embraced nuclear power then we would be living in paradise is also well, I mean, hello?, look at France. They have totally bought into nuclear power and they still can't come up with a good pop song or a decent car.
Just for my reference...a metric buttload is 1.83 Imperial buttloads, right?
I'm American, so I don't really use metric units that much.
bkr
"Growing old is inevitable; growing up is optional."
What he said.
Neutrons running amok in the reactor vessel (which, if it wasn't obvious, is a big metal container with the reactor core inside) cause two things to happen:
1. Some small fraction of the metal atoms absorb neutrons and change from stable isotopes to non-stable ones. Cobalt-60, with a half-life short enough to be pretty radioactive, and long enough to be a nuisance, is the biggest issue here.
2. Neutron embrittlement occurs. The reactor vessel becomes more prone to cracking instead of stretching under pressure changes. This is likely to be less of an issue in a low-pressure fusion reactor than in a high-pressure fission reactor. Both effects are known in advance, and designed around, though the earliest reactors were built without this (later) information. I don't know how many of the "earliest" reactors are still operational. My guess is none, but that's a guess.
Only real long term issue is the radioisotopes in the reactor vessel. This is why you have to mothball the reactor before dismantling it. Ideally, once you dismantle the things, you'd recover the Co-60 and related radioisotopes, but practically, it doesn't occur in amounts that are worth the trouble.
So you have to dispose of it in some "safe" way. Sealing it in glass bricks and stacking it in some out-of-the-way corner of the desert would do nicely.
"I do not agree with what you say, but I will defend to the death your right to say it"
The US already has at least one of these already.
The Princeton Plasma Physics Lab in Princeton, NJ has been experimenting with fusion since 1951.
I've toured the reactor, in addition to working there one summer, and it is a very fascinating technical achievement. Basically you have a large magnetic containment device (big donut) which contains a vacuum. The vacuum and the magnetic field keep the plasma from melting the containment device. Tritium (used to be deuterium) is placed inside and a huge amount of energy is pumped into the donut converting the gas inside to plasma with a temperature hotter than the interior of the sun allowing fusion to take place. Currently the amount of energy released is less than the energy needed to generate the fusion.
To give you an idea of how much energy is needed. The energy from the localpower company is used to get a bunch of giant dynamos spinning. To get the dynamos up to full rotational speed takes, IIRC, about 10 hours. All this stored energy is then released all at once.
The vast majority of their power is Nuclear, I was suprised .
77% Nuclear
14% Hydro
8 % Fossil
1 % Other
Thanks,
Ex-MislTech
google "32 trillion offshore needs IRS attention"