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Why does radiation stick to things?

  1. Jul 21, 2012 #1
    It is my understanding that radiation is caused by the weak nuclear force, that its the decay of particles. if this is the case, then can some one please explain why after an incident like Chernobyl for instance, that things for thousands of miles in all directions are still to this day emitting radiation.
     
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  3. Jul 21, 2012 #2

    Simon Bridge

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    It doesn't.

    When journalists talk about the radiation contamination they are being sloppy.
    An incident like fukushima and chernobyl and nuclear weapons detonations produce a lot of radionuclides and these fall, as dust, to the ground and get in the water and stick to things. These produce the ionizing radiation they are concerned about. This stuff is called "fallout".

    You'll also have heard of radioactive groundwater in Texas - which is radium-salt dissolved in the water and also getting deposited with the lime on the inside of pipes.

    Though you should realize that atoms bombarded by energetic charged particles can become radioactive, producing radiation when they decay.

    Notes:
    the strong nuclear interaction can also produce nuclear radiation

    particles produced in nuclear reactions can stick to stuff by any of the four forces ... they are matter after all. For instance, a beta particle may get captured by an atom since it's just an electron. (This is how non radioactive material may become radioactive through this interaction ... which is another way radiation ca appear to "stick to" things.)
     
  4. Jul 21, 2012 #3
    So your saying there are two types of radioactivity;
    the decay of atoms, or the weak nuclear force emitting radioactive particles such as beta particles,
    and radionuclides which are unstable isotopes that are remnants of nuclear explosions such as chernobyl

    In the case of the ground water in Texas, would it be that the radium-salt is a radionuclide of Radium. It is highly radioactive meaning it decays quickly releasing lots of radioactive particles into the water contaminating everything else?
     
  5. Jul 21, 2012 #4
    Most "everyday" radioactivity (ie apart from things that happen in collider experiments etc) is the decay of atoms. But not all atomic decays are betas - the other two common types are alpha and gamma decays, neither of which involve the weak force.

    A further process is nuclear fission, where very large nuclei split into two or more smaller chunks. This can happen spontaneously, but more commonly comes about as a result of a chain reaction. For example, a 235U nucleus will break into fragments if a 'slow' neutron collides with it. Usually, the nucleus disintegrates into two smaller nuclei plus some neutrons. These neutrons can then collide with other 235U nuclei ... this is basically how nuclear reactors work.

    The problem is that some of the the fission fragments are themselves radioactive. This is what's called nuclear waste.

    Radioactive isotopes all have a consistent decay rate, which can be described by their half life, namely the time it takes for 50% of any initial quanity to have decayed. Depending on the type of decay and the difference in energy of the isotope and its daughter produce, the half life can be anything from a tiny fraction of a second to billions of years. It's often the isotopes with half lives that range from a few days to several years that are the most problematic - see http://en.wikipedia.org/wiki/Fission_product.
    The predominant radium isotope has a half-life of 1601 years but is very highly radioactive. See http://en.wikipedia.org/wiki/Radium. The long half-life means it does not go away, at least not within timescales relevant to human lives.
     
  6. Jul 21, 2012 #5

    Simon Bridge

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    No - I am saying there are several ways that radiation can be produced.

    Nuclear Radiation is as umbrella terms for all the bits that fly off a disintegrating nucleus. The bit left behind is called the "daughter".

    Radiation, in general, can be matter, antimatter, or light, and does not have to be created by a nuclear disintegration. The matter and antimatter may be charged or uncharged. So - sunlight is radiation, so is the light from an incandescent bulb.

    Radiation from a nucleus may occur by strong or weak nuclear processes or by electromagnetic de-excitation. These commonly produce alpha, or beta particles, and light (and neutrinos, ejected nucleons etc).

    "Contamination" is not a good description for what radiation does. Treat it as one of those cases where the journalists don't get it.

    Something not normally radioactive can become contaminated by radioactive materials either by the materials themselves being introduced into it from outside or by radiation transmuting otherwise stable nuclei into unstable ones. The first kind is the most common. Bear in mind that radioactive materials occur naturally and a certain percentage even of our own bodies is naturally radioactive because of this.

    In relation to your question: the contaminant is radium chloride (or bromide?[1]). Radium is radioactive - so things contaminated with radium will set off a geiger counter. It is common for the press to mistakenly report this as contamination by radiation. The radiation from radium is not able to transmute common elements.

    Note: apart from radioactivity, radium salts are also poisonous.

    http://en.wikipedia.org/wiki/Radium#Radioactivity
    http://www.atsdr.cdc.gov/substances/toxsubstance.asp?toxid=154
    [1] Radium chloride is toxic, dunno about bromide. There's also nitrate and hydroxide ... so I could be assuming too much here.
     
    Last edited: Jul 21, 2012
  7. Jul 21, 2012 #6
    Thanks to all, you've really helped clear the matter up for me :)
     
  8. Jul 21, 2012 #7

    Simon Bridge

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    No worries ... :)
     
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