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Homework Help: Atoms/cubic cm of radiation

  1. Nov 24, 2007 #1
    1. The problem statement, all variables and given/known data
    "After cleanup at 3 mile island approximately 400,000 gal of radioactive water remained in the basement of the contaminated building. The principle sources of radioactivity were 137 Cs at 156E-6 Ci/cubic cm. How many atoms per cubic cm were in the water ?

    2. Relevant equations
    Not sure...

    3. The attempt at a solution

    6.022E23 * 156E-6/137 = 6.86E17
    Last edited: Nov 24, 2007
  2. jcsd
  3. Nov 24, 2007 #2


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    Homework Helper

    It's a little more complicated than that.

    A Curie (Ci) is 3.7E10 decays/second - so there are 156E-6 * 3.7E10 decays/sec/cc.

    Then you need the activity or half-life of Cs137 to know what chance there is of a decay in a second for one atom, or alternatively how many atoms there needs to be to give the above overall decay rate.
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