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Homework Help: Estimating Radiation Risk

  1. Apr 24, 2013 #1

    I'm looking to estimate my total extra exposure (dose above background) by taking into account account roughly how long I was near each source, the strength of the source, and its approximate distance from me. I believe it's useful to use the following equation,


    where [itex]\frac{dD_{0}}{dt}[/itex] is the dose rate at x=0 and c is the absorption coefficient.

    The dose rates measured at x=0 for the 3 sources, as well as the calculated absorption coefficients are

    Ba-133: 277 μR/h , c=0.303/in.
    Cs-137: 107 μR/h , c=0.375/in.
    Co-60: 117 μR/h , c=0.360/in.

    *note that the background radiation has been subtracted from the dose rates shown.

    So if I take the time t spend near each source as 10 minutes, and the distance from each source as x=0 in. (as I was holding the sources as we varied the distance in the first part of the experiment) I can approximate the exposure as


    and then sum these for from each source. So therefore I get,

    Ba-133: 277 μR/h * (10 min) * (1 h/ 60 min) = 0.0462 mR
    Co-60: 107 μR/h * (10 min) * (1 h/ 60 min) = 0.0195 mR
    Cs-137: 117 μR/h * (10 min) * (1 h/ 60 min) = .0178 mR

    Thus as my total extra exposure I get,

    0.0462 mR + 0.0195 mR + 0.0178 mR = 0.0835 mR

    Is this reasoning correct? Thank you in advance for any input.
  2. jcsd
  3. Apr 25, 2013 #2


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    Staff: Mentor

    Neither the dose measurement nor you received all radioactive decays, as just some fraction of them went in the direction where they got detected / absorbed in your body. In general, this fraction will be different, and depend on the setup.
    I would expect that you were holding something which was holding the sources. Even without absorber, distance to the source is crucial in the analysis.
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