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Clean Fusion Bombs?

  1. Mar 29, 2005 #1
    Could it be possible to one day create fusion bombs that are "clean"(not create radioactive isotopes and other nasty stuff that lingers for years)? The only thing it'd do is create thermal energy and the bast when it goes off?
  2. jcsd
  3. Mar 29, 2005 #2


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    To trigger a fusion bomb you need intense pressure and high temperature. At present using a fission bomb is the only practical method. Maybe in the distant future a laser trigger might be possible. At the moment they are simply trying to get something for a fusion reactor, using lasers.
  4. Mar 29, 2005 #3


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    That's correct.

    Additionally, saying that the fusion reaction is "clean" because it doesn't
    create any radioactive species [ at least not directly ] is short-sighted.

    The main fusion reaction under consideration is "D-T" fusion:

    D + T --> He4 + n + 17.6 MeV

    The product isotope He4 is stable - so it is often said that fusion is
    "clean" and doesn't produce radioactive species.

    However, that neutron; the "n" ; receives 14.1 MeV worth of energy and
    the next atom it hits will most likely become radioactive.

    So D-T fusion is only "clean" if you look at just the first generation of
    products. If you look one generation removed from the initial products -
    then you are going to have radioactive species and fusion is not "clean".

    In fact, fission gives you about 2 radioactive atoms per reaction, which
    releases about 200 MeV worth of energy. Fusion gives you 1 radioactive
    atom per reaction that releases 17.6 MeV of energy.

    So in effect, on a per energy released basis; fusion is more than 5 times
    more "dirty" than fission.

    Dr. Gregory Greenman
  5. Mar 29, 2005 #4
    Clean fusion bombs via tungsten or lead jacketing

    But can't the neutrons be stopped with lead?

    By jacketing the third stage with non-fissionable material, three stage devices can produce high yield clean weapons. Both Zuni and Tsar Bomba were in fact very clean devices - Zuni was 85% fusion and Tsar Bomba was 97% fusion. Both designs permitted replacing the lead or tungsten third stage jacket with U-238 however.
  6. Mar 29, 2005 #5


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    Yes - but you get radioactive lead - albeit a relatively short lived isotope.

    The "clean" Tsar bomb had a yield of 58 Megatonnes, or 58,000 kilotons.
    If it was 97% fusion, then it was 3% fission. Thus the fission yield was
    1740 kilotons - so Tsar was 116 times as "dirty" as Little Boy.

    The last line above tells the story on this. The lead jacket is used in lieu
    of a jacket of U-238. Under the flood of fast neutrons, the U-238 would
    fission thus creating lots of radioactive fission products.

    The fully configured Tsar bomb, with the U-238 jacket, was supposed to
    have a yield of 100 Megatonnes. Since the fusion yield was 97% of the
    tested 58 MT yield; or 56.26 MT - the fully configured device would have
    a fission yield of 43.74 MT. So the never tested "full-up" version would be
    56.25% fusion and 43.74 % fission. The "as tested" device, although having
    a yield that was 97% fusion - there was still very substantial fission yield.

    So the lead jacket case is only relatively clean in that you are not
    letting the neutrons cause extra fissions. You aren't escaping the
    fact that the neutrons are going to induce radioactivity; no matter
    what you do.

    Dr. Gregory Greenman
    Last edited: Mar 30, 2005
  7. Mar 29, 2005 #6

    Are you blind,

    the energy that is emmited from Deutrerium and Tritium fusion on the order of 17.6 meV is radioative - a stream of photons of a 10^-14 gamma wavelength.
  8. Apr 4, 2005 #7
    Well if fusion won't work what about anti-matter-matter bombs? IIRC anti-matter reactions only give off gamma and thermal energy. How would one shield the gamma from getting out but still have the huge explosion?
  9. Apr 4, 2005 #8


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    There are at least two obvious problems using anti-matter (in spite of Star Trek). First, how to make it in sufficient quantities for a bomb? Second, what sort of container can you use to hold it until you want the bomb to go off?
  10. Apr 4, 2005 #9
    Third, If accidentally the container gets broken or the bomb is hit with a nuclear missile, the whole bomb explodes. You don't want a 100,000 kiloton explosion in your own country.
  11. Apr 5, 2005 #10


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    lol i think this proves how people actually do care about the environment. We want the weapons that are made to kill hundreds of millions of people to be as harmless to the environment as possible lol.
  12. Apr 5, 2005 #11
    The only problem there is that the gamma rays produced are extremely high energy. As soon as they hit a nucleus, these rays would easily be able to knock several nucleons out, possibly even splitting the atom altogether. And these nucleons would likely have high kinetic energies, and thus be capable of causing further radioactivity upon impact with other nuclei.
  13. Apr 5, 2005 #12


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    Thermal energy implies particles other than photons, i.e. thermal energy is the manifestation of particle kinetic energy. A proton-anti-proton reaction generally causes pions or Kaons, which then decay muons and pions/muons respectively (see table on decay modes), and muons ultimately decay into electrons and neutrinos.

    Photo-nucleon reactions have a threshold, the binding energy of the nucleons. The gamma-rays are much more likely to scatter off-electrons.

    One does not keep gamma-rays from getting out - they scatter and each subequent photon has less energy.
  14. Apr 5, 2005 #13
    Going back to the inital topic for a second, why make something like fusion a weapon!? I want to go into research on fusion when I graduate and I do not want to make it into something that is a weapon. I know that is far too idealistic, but I would feel better thinking that I am helping the world, not working towards its destruction.
  15. Apr 5, 2005 #14


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    Although it is counterintuitive; nuclear weapons, in the opinion of many,
    are responsible for keeping the peace.

    There is an old expression from "Epitoma Rei Militaris" by Vegetius -
    "Igitur qui desiderat pacem, praeparet bellum." or "If you want peace,
    prepare for war".

    Owing principally to both World War I and World War II; during the
    first half of the 20th century - about 1 million people per year were
    killed in war.

    After 1945, that number dropped precipitously. What happened in
    1945 to cause that? The dropping of the bombs on Hiroshima and
    Nagasaki is what!

    Due to the existence of nuclear weapons - all out war, like humankind
    experienced twice in the first half of the 20th century, is no longer an

    The deterence to war afforded by the existence of nuclear weapons
    has arguably saved many, many lives. In that matter; those that
    work on nuclear weapons are helping to save the world - not destroy it.

    Dr. Gregory Greenman
  16. Apr 5, 2005 #15


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    Ir is regrettable that this people lost time "saving the world" instead of, for instance, decoding the origin of the spin-orbit coupling at magic numbers.
  17. Apr 7, 2005 #16

    Were did I say weapon? I didn't. The point of having non radioactive isotope creating bombs is you could use them for stuff without hurting biology for decades afterwards. Using nukes for blasting out huge amounts of rock in pit mines is one use I can think of, or that pesky mountain you want gone. :smile: :wink:
  18. Apr 7, 2005 #17

    Particle accelerators designed to make it in high amounts, they are powered by fusion power plants.

    Magnetic bottles, like we already use to hold small amounts of anti-matter. Or the ones that keep plasma from touching matter in plasma rockets.<-- These things already exist; they just need improving before NASA uses them.
    Or out in the realm of still speculation, thin tanks of monopolium .
  19. Apr 8, 2005 #18


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    How high is high amounts - thousands of anti-protons? For bomb purposes, it may not be enough. There are no fusion power plants!
  20. Apr 9, 2005 #19


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    you guys get offended so easily lol. Its a weapon against mountains!
  21. Apr 9, 2005 #20


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    .... fusion bombs already exist. They are banned by international treaty though but Russia and the US most likely still have half a dozen or so sitting around. At least thats how i think it is.... not sure. Can anyone clarify?

    And whoever said the whole, nukes have stopped war... man... isnt that the greatest irony this worlds ever realized lol. The real question though is having the threat of a small accident causing the human race's exstinction vs the practical guarantee of no massive wars killing tens of millions ever happening again. And i hate when people think its bad to have nukes because there 'full of hate' or some other hippie slogan like that. I mean come on, look at Russia now and look at it the past 50 years. Take nukes outta the equation and we'd be doing WW5 right about now. We learned nothing from WW1 and WW2 (typical human nature) and would probably have gone into ww3 the second another nation got back to military strength. So yes, totally, peace = threat of annihilation!
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