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Thread: how close are we to fusion power reactors?

  1. #1
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    how close are we to fusion power reactors?

    in the text of an artical i read (scientests measure coldest temp yet) i spotted this:

    [[[At such low temperatures, atoms cannot be kept in physical containers, because they would stick to the walls. Also, no known container can be cooled to such temperatures.

    "To circumvent this problem, magnets surround the atoms, which keep the gaseous cloud confined without touching it. To reach the record-low temperatures, the researchers invented a novel way of confining atoms, which they call a "gravito-magnetic trap." The magnetic fields acted together with gravitational forces to keep the atoms trapped."]]]

    Now im not a scientist but I was under the impression that one of the biggest hurdles to developing fusion power was containing the plasma. Has this changed?

  2. #2
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    Re: how close are we to fusion power reactors?

    Quote Originally Posted by kenneth rodman
    in the text of an artical i read (scientests measure coldest temp yet) i spotted this:

    [[[At such low temperatures, atoms cannot be kept in physical containers, because they would stick to the walls. Also, no known container can be cooled to such temperatures.

    "To circumvent this problem, magnets surround the atoms, which keep the gaseous cloud confined without touching it. To reach the record-low temperatures, the researchers invented a novel way of confining atoms, which they call a "gravito-magnetic trap." The magnetic fields acted together with gravitational forces to keep the atoms trapped."]]]

    Now im not a scientist but I was under the impression that one of the biggest hurdles to developing fusion power was containing the plasma. Has this changed?
    What you read was related to Bose-Einstein Condensates, not fusion. The magnetic trap mentioned is extremely shallow - so much so that the gravitational potential energy of a single atom is noticable within the trap. Notice that the discussion here is about really low temperatures (nanokelvin), while in fusion plasmas, the temperatures are extremely high.

    So yes, a big hurdle to fusion is containment and compression, and no, that hasn't changed. But your quoted comments have nothing to do with that.

  3. #3
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    Scientists can contain the plasma fusion creates, but they can't break even yet in terms of the energy to start the reaction vs. the energy from the reaction. I think that they also aren't sure how they will add more fuel to the plasma once its going but that's a problem for an engineer building a functional reactor- and we're not that far along yet.

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    Re: how close are we to fusion power reactors?

    The topic of the article you mentioned involves containing a small number of particles at very low temperature, thus with little kinetic energy.
    What a fusion reactor is around, is containing extremely hot (that translates to extremely fast) ions, and keeping the plasma as dense as possible, because the number of collissions that happen between the ions in the plasma is a function of the density of the plasma (and of the particles' speed, of course). As you see, the plot for low temperature experiments is quite different from the requirements for nuclear fusion to take place.
    I hope that makes things clearer.

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    Viewing this thread before and after i post my reply, i guess i write a little bit to slow.

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    Just wanted to say "welcome to the Bad Astronomy Bulletin Board" to Kenneth Rodman. Good first post.

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    Yup, yup, yup! I've heard all the disappointing stories about how difficult or impossible perfecting nuclear fusion energy is. That said, I'd like to hear some positive news (if any) on nuclear fusion research. Please, please, please give me some positive news on nuclear fusion research no matter how insignificant it is!
    :x

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    50 years ago, we were 20-30 years away from fusion power that was "too cheap to meter". I guess the big difference is that today, we are 20-30 years away from fusion power that is cheap enough to be competitive.

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    According to Heinlein's Timeline fussion will not happen until 2100AD. I think we are right on shedule.

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    We are about 150 million kilometers from a fusion reactor, and given the general public hysteria whenever anything "nukyular" is mentioned, its going to be the closest for some time! :-?

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    There is a ninternational consortium that is scouting locations right now to build a new experimental reactor. It may not actually reach fusion but it is intended to work out some of the tech hurdles. The US was backing a site in Spain.

    http://www.iter.org/

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    Quote Originally Posted by Celestial Mechanic
    We are about 150 million kilometers from a fusion reactor, and given the general public hysteria whenever anything "nukyular" is mentioned, its going to be the closest for some time! :-?
    Thought I'd delurk and clear up something - we're a hell of a lot closer than that to fusion powerplants:

    http://deseretnews.com/dn/view/0,1249,510054502,00.html

    The reactor the kid built is one based on a 1960s design. We've actually built plenty of fusion reactors - we just can't get one that passes the "break even" point, where it produces more energy than it uses.

    Personally, I'm more eager for fission-based "rockets", such as NASA's Prometheus Project. BTW, beware their PDFs - they keep crashing my browser.

    This site has a pretty good description of the Prometheus Project, and it appears they've had more luck with NASA's PDFs than I have.

    Depending on the type of fission rocket (solid, liquid or gas core), estimates put the specific impulse for them at 800-1100, 1200-1500, or 3000-7000 seconds respectively. Thespacesite.com has a good page on fission rocketry, as well.

    While this isn't going to get us to Alpha Centauri, it WILL get us pretty much anywhere we need to go in the solar system within a reasonable period of time.

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    <--------------------------------------------->
    we are about this close. 8)

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    Quote Originally Posted by SirThoreth
    Thought I'd delurk and clear up something - we're a hell of a lot closer than that to fusion powerplants:

    http://deseretnews.com/dn/view/0,1249,510054502,00.html

    The reactor the kid built is one based on a 1960s design. We've actually built plenty of fusion reactors - we just can't get one that passes the "break even" point, where it produces more energy than it uses.
    ... which is precisely what we'd need to achieve if we ever want to be able to build fusion powerplants.

    I don't see how the Farnsworth design brings us any closer to the break-even point -- so what if it's simple enough that a college freshman can build one out of junkyard parts? It's still as inefficient as any of the other designs out there, and far more inefficient than the designs that show promise.

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    But wait ... did that article say the Farnsworth reactor uses solely deuterium? Not deuterium and tritium?

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    Quote Originally Posted by tracer
    Quote Originally Posted by SirThoreth
    Thought I'd delurk and clear up something - we're a hell of a lot closer than that to fusion powerplants:

    http://deseretnews.com/dn/view/0,1249,510054502,00.html

    The reactor the kid built is one based on a 1960s design. We've actually built plenty of fusion reactors - we just can't get one that passes the "break even" point, where it produces more energy than it uses.
    ... which is precisely what we'd need to achieve if we ever want to be able to build fusion powerplants.

    I don't see how the Farnsworth design brings us any closer to the break-even point -- so what if it's simple enough that a college freshman can build one out of junkyard parts? It's still as inefficient as any of the other designs out there, and far more inefficient than the designs that show promise.
    The Farnsworth design doesn't bring us any closer to having an efficient reactor. My point was to show that the first hurdle, producing a controlled fusion reaction in the lab, has long since been solved. Producing a useful reactor? :-? Still a ways off.

    Quote Originally Posted by tracer
    But wait ... did that article say the Farnsworth reactor uses solely deuterium? Not deuterium and tritium?
    You read correctly.

  17. #17
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    Just want to say, "Welcome, and a most excellent delurk!" to SirThoreth. =D>

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    aw, man. i'm about his age and i haven't even invented fire yet... oh well, better get crackin'. #-o

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    zrice03: I hear someone's invented these little sticks of wood with a chemical coating on one end that you can set on fire just by zipping it across the rough surface on the side of the box! That'd be a good place to start, I think.

  20. #20
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    i was just making a joke.

  21. #21
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    How about we dig a large underground cave, Fill it with water, detonate termonuclear bombs in it and use the steam produced to turn a turbine that turns a dynamo to produce electricity?

    It is a very large version of a fission reactor.

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    1) I'd hate to be the engineer charged with designing the turbines to take the stress of going from zero to a bazillion (technical term) atmospheres of pressure in microseconds.
    2) I'm afraid that this would be a one shot device, since after use, it would no longer be water tight and the water would leak out faster than you could pump it in. #-o

  23. #23
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    Plus, I'm still not convinced that the majority of energy released from a thermonuclear bomb (i.e. an H-bomb) is produced by fission. Call me crazy, but that deuteron-triton reaction sure seems to me like it'd produce a pretty substantial portion of the direct bomb yield.

  24. #24
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    Cold fusion... hmmm

    Hot fusion is produced because the negatively charged electrons are exited by heating to such a high state of exitement that they are in such a high orbit that they can be said to have been striped from their nuclei. So the repulsive effect of their same polarity of charge (negative) is negated allowing the neutraly charged nuclei of deuterium and tritium (The most electronically active, albeit least electronically active in the universe, atoms that can be fused on a large scale by current human technology.) to fall together under the attractive force of gravity and fuse together to form one helium nuclei and one fast neutron. The energy gotten from the reaction being got from the fast neutron being "kicked" out by the release of the binding energy contained in the difference between the two particle nuclei of deuterium (one proton and one neutron) and the three particle nuclei of tritium (one proton and two neutrons) combining to form the four particle nuclei of helium (two protons and two neutrons).


    Cold fusion...

    Reduce the exitation of the electrons so that they havn't the energy to repel other atoms of same polarity or to allow for the magnetic orientation of the electrons so that their same polarity is negated.

  25. #25
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    Quote Originally Posted by SAMU
    Cold fusion... hmmm

    Hot fusion is produced because the negatively charged electrons are exited by heating to such a high state of exitement that they are in such a high orbit that they can be said to have been striped from their nuclei. So the repulsive effect of their same polarity of charge (negative) is negated allowing the neutraly charged nuclei of deuterium and tritium (The most electronically active, albeit least electronically active in the universe, atoms that can be fused on a large scale by current human technology.) to fall together under the attractive force of gravity and fuse together to form one helium nuclei and one fast neutron. The energy gotten from the reaction being got from the fast neutron being "kicked" out by the release of the binding energy contained in the difference between the two particle nuclei of deuterium (one proton and one neutron) and the three particle nuclei of tritium (one proton and two neutrons) combining to form the four particle nuclei of helium (two protons and two neutrons).


    Cold fusion...

    Reduce the exitation of the electrons so that they havn't the energy to repel other atoms of same polarity or to allow for the magnetic orientation of the electrons so that their same polarity is negated.
    (emphasis added)

    Deuterium and tritium aren't neutral - the have a proton. It's that repulsion that needs to be overcome. Gravity doesn't come into play - the gravitational force between nucleons is many orders of magnitude weaker than both the strong nuclear force and the electrostatic repulsion.

    Your cold fusion blurb is, frankly, gibberish.

  26. #26
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    Cold fusion isn't exactly rubbish (although I agree that his explaination is). There is a theoretical proccess which can result in cold fusion.

    Basically take an amount of Deuterium and bombard it with muons. Occasionally one will enter the orbital shared by two Deuteron atoms. Muons are much heavier than electrons, about 204 times, and will cause the two nuclei of the atoms to rapidly move together and fuse.

    The problems with making this practical is that it takes alot of energy to produce muons and most of them made don't result in fusing two atoms together. Also, muons have a very brief half-life, about 2.2 microseconds. Any machinery that produces the muons would have to be close enough to the reaction to make it work, yet that might hinder the reaction itself.

    I have also thought about using taus, which are like electrons, but are about twice as massive as protons. I am not sure, though, of their half-life or how much energy it takes to produce them. Does anybody have information of this?

    Anyway, if we could overcome all these technical limitations, then we could produce millions of times more energy than we can today, but realistically, I don't see it happening. I much more hold my breath for something like zero-point energy.

    P.S. "[The Scarlet Pimpernel]'s the most overrated human being since Judas Iscariot won the AD 31 Best Disciple Competition." -E. Blackadder

  27. #27
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    Right you know I think all of the "research" in this field had been tossed out years ago because it was bull.......

  28. #28
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    Oh Ghod ... where to start:

    Quote Originally Posted by SAMU
    Hot fusion is produced because the negatively charged electrons are exited by heating to such a high state of exitement that they are in such a high orbit that they can be said to have been striped from their nuclei.
    That's a "plasma", not "hot fusion." (Albeit hot fusion does admittedly involve plasmas.)
    So the repulsive effect of their same polarity of charge (negative) is negated allowing the neutraly charged nuclei of deuterium and tritium
    As swansont stated, the nuclei of deuterium and tritium are not neutrally charged -- they're positively charged.
    (The most electronically active, albeit least electronically active in the universe, [ snip] )
    I have absolutely no clue what you mean here. But I'll bet it's bogus.
    to fall together under the attractive force of gravity and fuse together to form one helium nuclei and one fast neutron.
    The gravitational attraction between individual nuclei is so weak as not to merit attention. In hot fusion, nuclei don't "fall" together -- they're thrown toward each other so fast that their own momentum is high enough to overcome their mutual electrostatic repulsion, to the point where they're close enough together that the strong nuclear force (which has an extremely short range, like 1/100,000 of the diameter of an atom or so) can take over and bind the two nuclei together.
    Cold fusion...

    Reduce the exitation of the electrons so that they havn't the energy to repel other atoms of same polarity or to allow for the magnetic orientation of the electrons so that their same polarity is negated.
    Have you ever looked at a scale model or scale diagram of an atom before? If you drew the orbits of the electrons -- even "unexcited" electrons in the lowest possible ground state -- as a sphere as big around as your bedroom, the nucleus would be about the size of a dust grain. The electrons don't even enter into the picture where nuclear fusion is concerned.

  29. #29
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    Certainly, the challange of describing thermonuclear fusion in less than 200 words does result in a certain degree of imprecision. You don't agree with my description? I challenge you to write one that is more precice, in less than 200 words and in coloquial nomenclature.

    I write with a reader in mind, a reader who does not necesarily know what the word "plasma" means. (a word which, by the way, is used in other fields with other meanings than in atomic physics.(ever heard of blood plasma?))

    Fusion does not happen because like charged atoms (via the eletron) or nuclei repel each other.

    A thermonuclear reaction happens because the electrons that have like charges, as was mentioned, that repel each other are stripped from the atom. An elemental hydrogen atom has one proton and one electron and as such, even if the electron is stripped away will still have a positively charged proton nuclei that will repel other proton nuclei and not allow fusion to happen. The hydrogen isotopes deuterium and tritium have neutrons in the nucleus which make their specific gravity greater than elemental hydrogen. The reason deuterium and tritium are used in fusion is because the greater specific gravity allows the nuclei to overcome their respective proton repulsions. (also because their additive nucleonic structure, two protons three neutrons, results in one higher order nucleus (a helium nuclei, two protons two neutrons) plus a fast neutron.) They fall together under their mutual, (not the Earth's) close range, gravitational attraction.

    We can't fuse heavier atoms on a large scale because they have more electrons to strip away. Thus requiring more energy to exite them to a state where the nuclei will fall together under their gravitational attraction.

    What is meant by (full aplicable quote) "deuterium and tritium (The most electronically active, albeit least electronically active in the universe, atoms that can be fused on a large scale by current human technology.)" can be best explained in coloquial terms by "The most I can lift is 200 pounds. That is not the most that exists but it is the most I can lift". So deuterium and tritium are not the most electronically active* atoms in the universe (they are the least) but they are the most electronically active that we can fuse on a large scale by current human technology.

    *electronically active meaning the number of electrons they have in the elemental (non ionized) form of the atom.

  30. #30
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    Quote Originally Posted by SAMU
    The hydrogen isotopes deuterium and tritium have neutrons in the nucleus which make their specific gravity greater than elemental hydrogen. The reason deuterium and tritium are used in fusion is because the greater specific gravity allows the nuclei to overcome their respective proton repulsions. (also because their additive nucleonic structure, two protons three neutrons, results in one higher order nucleus (a helium nuclei, two protons two neutrons) plus a fast neutron.) They fall together under their mutual, (not the Earth's) close range, gravitational attraction.
    No. Absolutely not. The gravitational force isn't nearly large enough to come into play. The force of attraction is the strong nuclear force, which is short-ranged. The nuclei must overcome the Coulomb barrier, which is present because the nuclei have like charges, and has an infinite range, in order to get close enough for the nuclear force to attract the nuclei.

    Exercise: what is the gravitational potential energy of two deuterium atoms at 10^-15m separation? What is the electrostatic PE at this distance?


    We can't fuse heavier atoms on a large scale because they have more electrons to strip away. Thus requiring more energy to exite them to a state where the nuclei will fall together under their gravitational attraction.
    We don't bother with heavier nuclei because it's even harder for them to get close to each other. The repulsive force goes as q^2. Stripping the electrons away is relatively easy. And the energy released has a local maximum when you form He-4, since it's so tightly bound.

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