Posted by **Velaria** on Thursday, November 20, 2008 at 4:55am.

Please help me with this problem.

The standard source for radiation therapy was radioactive 60Co which decays with a halflife of 5.27y, into an excited nuclear state of 60Ni. That nickel isotope then immediately emits two gamma ray photos wach with energy of 1.2 MeV. How many radioactive 60Co nuckei are present in a 6000 Ci source?

Cheers

- Physics -
**drwls**, Thursday, November 20, 2008 at 9:27am
The decay process is explained better at

http://en.wikipedia.org/wiki/Cobalt-60

Each Co-60 nucleus results in one beta electron and two gamma photons. That is three nearly simultaneous radioactive emission processes during the each transmutation, with a 5.27 year half life.

One gram of Co60 has a radioactivity level of 50 Ci. One should be able to derive that from the half life and the three radioactive decay steps per nucleus. 6000 Ci would therefore require 120 g of Co-60. That equals 2.00 moles, so there are 12*10^23 Co-60 nuclei in that amount of Curies.

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