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Helium 3 and Artificial Creation of Isotopes

  1. Dec 1, 2009 #1
    Hey folks,

    I think this is the best section to ask this question.

    I've been thinking about the mining of He-3 on either the moon or the gas giants and the associated exorbitant costs, usually measured in the tens to hundreds of billions of dollars. I've also been trying to think of ways around this.

    I'm no atomic physicist, but how hard would it be to strip a He nucleus of one of its neutrons to make He-3 (I think I've got that correct).

    Ok Ok, I may hear cries of 'Alchemy', but hear me out for a second. Let's say, for the sake of argument, that a full scale He-3 mining operation on the moon would cost $100 billion...thats a LOT of money. How much might a 'matter transmutation' project cost? Surely less.

    Is there anything wrong here in terms of the physics? Could one, in theory, strip a neutron from a nucleus? How might it be done? PetaWatt lasers perhaps?

    Ideas...
     
  2. jcsd
  3. Dec 1, 2009 #2

    mgb_phys

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    You can make He3 from Tritium.
     
  4. Dec 1, 2009 #3

    Astronuc

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    That's the most practical way, and tritium can be produced from (n,α) reaction with Li-6. Unfortuantely, T has a half-life of ~12.3 yrs, so it would take a while.

    The α particle (He4 nucleus) is quite stable, and it would take a pretty energetic neutron to knock out a neutron with an (n,nn') reaction. And He3 is a great absorber of thermal neutrons.
     
  5. Dec 1, 2009 #4
    Thanks for the quick responses mgp phys and Astronuc.

    It sounds like there's nothing physically wrong then with the idea of creating He-3 here on Earth instead of launching massive mining operations and sending them to the moon.

    Astronuc - what do you think of the idea of using PetaWatt lasers - could that be used, in principle, to strip the [itex]\alpha[/itex] particle of one of the neutrons?
     
  6. Dec 2, 2009 #5

    Astronuc

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    Firstly - Petawatt is simply a power level (rate of energy). One would have to look at the photon energy, which would have to be on the order of the binding energy of one neutron in the He-4 nucleus, which is in the MeV range.

    One can dissociate a deuteron (into a proton and neutron) with a photon of energy on the order of 2.2 MeV, but an alpha particle requires more energy.

    d + d fusion produces He3 (along with a neutron) in about 50% of the reactions.

    d + He3 => is a nice aneutronic reaction => α + p
     
  7. Dec 2, 2009 #6
    Ok, I see - thanks for putting me straight on the Petawatt aspect.

    So here's another question. The whole purpose of mining He-3 would be for a more energetic fusion reaction so one would assume that fusion technology would have been pretty much perfected before we started performing any mining operations.

    However, from your reaction above, d+d produces He-3 in approx 50% of reactions, then surely it would be cheaper to fuse d+d on Earth and extract the He-3 from this process....right?
     
  8. Dec 2, 2009 #7

    Astronuc

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    Most of He3 produced in dd fusion would likely be consumed in the fusion process. If it could be produced in the fusion plasma, it wouldn't be worthwhile to remove it, but use it in situ. This is the basis for catalyzed-dd fusion.

    In dd fusion, the other 50% of reactions produce t + p. Unfortunately the t + d => He4 + n, and the n has an energy of 14.1 MeV. The d+t reaction is easier to achieve than d+He3.
     
  9. Dec 2, 2009 #8
    As I understand it, Helium3 was found on the Moon by Apollo missions. I am unsure why our little sister planet should be so favoured, given that the stuff is so hard to make. Maybe the Earth magnetic field made all the difference in deflecting the solar wind.

    So even approximately, how much do we guess is likely to be on the moon?
    And.. how much of it might we need for our (future) fusion plant?

    I know, I know - my internal skeptics flag is beginning to wave about madly, and is seriously interfering with my attempts to to keep an open mind about it.
     
  10. Dec 2, 2009 #9

    f95toli

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    Most of the He-3 that we use IS made via nuclear reactions. Nearly all of the He-3 on the world market was originally made in various American facilities that primarily make material for nuclear bombs(tritium, they just keep the He-3 as well). Hence, the original customer was the US Military and they've just been selling off what they didn't need.
    However, nowadays the production of new bombs has stopped meaning they don't make nearly as much He-3 anymore. The price of He-3 has gone up a LOT over the past few years, from about $100 per liter(1 Bar) to $1300. And that price is still too low to justify commercial production.

    Fortunately, when we use He-3 in the lab (for e.g. cryogenics) it is mostly in closed systems so we rarely have to buy new gas (the He-3 I use has been in our system for at least ten years).

    Anyway, the main point is that yes we can make He-3 on earth (and we've been making it for a long time) but the process is way to expensive to be used to make fuel.
     
    Last edited: Dec 2, 2009
  11. Dec 2, 2009 #10

    Astronuc

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    The solar protons cause spallation reactions in the lighter elements, and He-3 and T (which decays to He-3) are products.

    Some folks at NASA and DOE have used the presence of He-3 as a justification for returning to the moon. There are estimates out there, but I'd have to look around.
     
  12. Dec 3, 2009 #11
    Thanks for all who responded to this topic for providing your insights.

    I'm very interested in seeing what would be most cost effective. Spending $100 Billion + on a lunar mining program, or spending $100 Billion on an Earth based program to generate the He3 artifically with, perhaps, an undiscovered technology.

    Your inputs have been valuable!
     
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