RE: cesium-137 gamma abundance

["Vetter, Richard J., PhD." <rvetter@mayo.edu>]

ICRP 38 gives 94.6% as the abundance for the beta decay from Cs-137 to
Ba-137m and 90% as the abundance for the 0.662 MeV gamma from Ba-137m
(the other 10% emitted as conversion electrons). Thus, the abundance of
the 0.662 MeV gamma per Cs-137 decay is 85%. 


Richard J. Vetter (rvetter@mayo.edu)


>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
>
>