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An easy one about atomic bombs.

  1. Sep 16, 2007 #1
    The Little Boy bomb dropped on Hiroshima was very inefficient in terms of the amount of uranium fissioned. My questions are: What happened to the unreacted uranium and does it still pose a problem? I'm sure for most of you on this site this is an extremely easy question, but I am new to this and would really appreciate any help.
  2. jcsd
  3. Sep 16, 2007 #2
    Considering that it was seemingly relatively safe to stand right next to (or at least be in the same plane as) the bomb where the uranium was concentrated, I would assume that less than 60 kg of uranium spread over an area of say 10 km² (value guesstimated from the wikipedia article on the hiroshima bombing) causes a negligible radiation stress.
    Personal sidenote: I always have to wonder why people are interested in nukes. Apart from some exotic ideas about accelerating spaceships, they are pretty useless devices - at least for morally-acceptable applications.
    Last edited: Sep 16, 2007
  4. Sep 17, 2007 #3


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    Another exotic idea is to save us from astreoids :)
  5. Sep 17, 2007 #4


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    Well, they are the most powerful form of energy we have yet been able to harness. Why would we NOT exploit it?
  6. Sep 17, 2007 #5
    Hmm, Fusion Reactor.... Atomic Bomb....

    The former is a fantastic display of the (to most people) mythical power of the universe, it has tendrils into the moral ideas of compromise and egotistical power. These emotions and concepts are interesting at the least. The Fusion reactor? Well to most people it’s just a new toy that they never see directly.

    (I work in the oil field, so "most people" is in reference to this group of people that I have been exposed to.)
  7. Sep 17, 2007 #6
    I don't really see how nukes are used in fusion reactors. It seems a bit counter-productive trying to start the fusion process by blowing up the facility and everything in a 1 km radius around it. I've not said that nuclear physics is a useless field, but explicitely meant the weapons which in contrast to e.g. dynamite have no useful purpose (except for movies :biggrin:). Discussion about that is not the topic of the thread, anyways; being the only one responding to the OP, I just took the liberty to comment on the (in my eyes somewhat ill) wide public interest in nukes (which does not necessarily apply to BillH, the question was certainly not in the "how does one build nukes"-line and hadn't gotten any reply by me if it had been).

    EDIT: Did you (lilrex) possibly mean "the latter" instead of "the former"? Your post seems to make more sense with "the latter".
    Last edited: Sep 17, 2007
  8. Sep 17, 2007 #7
    Timo, the Fusion reference was intended to compare something useful in Nuclear physics with the fascination of nukes, I am sorry if my comparison was not clear I just found your comments on the matter interesting.

    BillH, the unreacted uranium would still pose a problem if the dust were to get in your lungs, it is unforgiving in that respect but the uranium its self is heavy and would likely be precipitated out of the air born environment. I am still looking for a reference for that though, so don’t quote me on that.
  9. Sep 17, 2007 #8


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    Off hand I suspect that, in the fallout from a nuclear bomb, the fission products would pose a much more serious hazard than the unexploded uranium.
  10. Sep 19, 2007 #9


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    The primary health hazard posed by uranium is one of chemical toxicity (think "lead poisoning"), not radioactivity. As far as isotopes go, the uranium series is an extremely benign alpha-emitter -- won't even make it through the top layer of your skin. Ingestion is the health-risk posed by alpha-emitters (raises the relative biological effectiveness by an order of magnitude), but that being said, with uranium you'd be dead from heavy-metal toxicity long before the radiation would do anything.
  11. Sep 27, 2007 #10
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