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Help with radiactive decay and radiation interactions hw

  1. Feb 6, 2005 #1
  2. jcsd
  3. Feb 6, 2005 #2


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    Staff: Mentor

    Nothing like waiting for the night before, eh?

    For problem 2. One is given a source strength 2.3 Ci (1 Ci = 3.7E10 disintegrations/sec) of 60Co (t1/2=5.27 yrs), which is also the activity.

    Activity A = [itex]\lambda[/itex] N, where [itex]\lambda[/itex] (the decay constant) = 0.69315/ t1/2. Make sure you convert half-life to seconds if used with 1 Ci = 3.7E10 dps.

    Therefore N (the number of atoms) = A / [itex]\lambda[/itex].

    Using Avogadro's number and atomic mass, one can convert number of atoms to mass.

    The activity A(t) as a function of time is given by A(t) = Ao [itex]e^{-\lambda t}[/itex]. So one needs to find t when the activity has decreased to 1.4 Ci from 2.3 Ci.

    For problem 3.

    Look at class notes (Cross-section.pdf is a better explanation of the nuclear cross section concept covered during lecture 3):

    FIGURE II.17. Monoenergetic parallel neutron beam incident normally on a thick target

    and equations II.34 and II.35.
    Last edited: Feb 6, 2005
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