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B Is nuclear fusion possible on earth??

  1. Jul 13, 2016 #1
    Is nuclear fusion fusion possible on earth naturally or can it be possible in an earth in a parallel universe??
     
  2. jcsd
  3. Jul 13, 2016 #2
    It is not possible naturally, since the temperatures and pressures required do not occur naturally on Earth. We have to recreate them. Places like ITER and JET have undergone brief nuclear fusion. We aren't quite at the point where the energy out is more than the energy put in, but we are very close! :smile:

    Here is ITER's website: https://www.iter.org/
    And here is JET's website: https://www.euro-fusion.org/jet/

    But no, it cannot occur naturally.
     
  4. Jul 13, 2016 #3

    Vanadium 50

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    There is a very, very small amount of muon-catalyzed fusion in the oceans.
     
  5. Jul 13, 2016 #4

    Ibix

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    Do you have a reference for that? That's something I'd like to have in the old mental filing cabinet, along with the Oklo fission reactor.
     
  6. Jul 13, 2016 #5

    mfb

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    All sorts of reactions happen if you look close enough. About 1 in 1017 hydrogen atoms is tritium, about 1 in 7000 is deuterium, now imagine the probability that a muon gets stopped by a hydrogen molecule (those are rare enough in sea water) that has both together...

    Fusion reactions from cosmic rays in the atmosphere happen more frequently, but still on the level of "oh, there was one fusion reaction here".
     
  7. Jul 13, 2016 #6

    Vanadium 50

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    There was a Scientific American (I think) article many years back that calculated this. Basically, you get a mu- that slows down in seawater and is captured on deuterium. Then you get D-H fusion, or if you happen to hit some D2O, D-D. (While D2O is rarer than DHO by a factor of several thousand, the fusion rate is higher by a factor of several thousand) It's a hard process to observe, because there are many larger sources of helium.
     
  8. Jul 13, 2016 #7

    TeethWhitener

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    I'm highly skeptical of this. The reason lab-observed muon-catalyzed fusion works so well is because the muon is captured by an exchange reaction, where H2+ (two nucleons and an electron) undergoes an electron-muon exchange to give H2μ+. The thing is, the only thing holding the H2+ system together is that one electron. When it's replaced by the muon, the bond length shortens by the mass factor of the muon. For D2O, on the other hand, you have a system of 10 electrons, 4 of which directly participate in bonding and 8 of which are valence electrons. Furthermore, if the fusion is D-D, you have to get the deuterons close enough together to fuse, but remember, there's an oxygen atom in the way. So the muon would have to either, as mfb said, encounter some dissolved D2 in the seawater, or it would have to 1) catalyze the breakup of D2O into something that was geometrically amenable to fusion, and 2) remain attached to that species to actually catalyze the fusion. I'd be interested in seeing the reference you're pulling from, if you can remember it.

    EDIT (and I'm sure someone out there has looked at this): It would be informative to look at a paper on muon interactions with water. My guess is that the muon occupies a deep core orbital on the oxygen, giving a species that looks nominally like H2N- (assuming no electrons are ejected) (this is because the Oμ system behaves chemically like a nitrogen atom since the muon orbits so much closer in to the oxygen nucleus than the electrons), a species whose bond length is probably comparable to that of NH3.
     
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