Re: cesium-137 gamma abundance

[Judd Sills <sillsj@GAT.COM>]

At 04:40 PM 10/22/96 -0500, you wrote:
>I have a question concerning the yield or abundance for the cesium-137 662
>keV gamma.  The lesson plans used here at Los Alamos National Laboratory
>(which are written by the DOE) use the 6CEN to get the exposure
>rate in R/hr, where C is the activity in curies, E is the energy of the
>gamma in MeV, and N is the percent abundance.  The lesson plan uses 85% as
>the abundance for the 662 keV gamma and I ahve ssen the 85% used elsewhere.
>When looking in books that show the decay scheme for cesium-137 they
>indicate that the abundance is 93.5%.
>
>Which one is correct?  Any thoughts on the subject would be appreciated.
>
>Thanks.
>
>
>Rick Rasmussen
>Los Alamos National Laboratory
>phone: 505-665-7973
>fax:   505-665-4859
>e-mail rickras@lanl.gov
>
>
Cs-137 decays to Ba-137m by beta emission, 93.5% of the time.
The other 6.5% of the time it decays directly to Ba-137.  It is
Ba-137m that then emits a 661.6 KeV photon with a yield of 89.98%.
The product of .935 and .8998 is 0.84131 or 84.13%.  Close enough
to 85% for me!

Best regards
J. M. Sills, CHP                                          (619)455-2049
General Atomics, Room 01-166C      Fax:(619)455-3181
3550 General Atomics Court              E-Mail:  sillsj@gat.com
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