Re:?-Chart of the Nuclides -Reply

[Charles Willis <CAW@nrc.gov>]

Zack,

I believe the fission product yields reported on the Chart of Nuclides are the total
yields for the isobar.  For example, in the 135 isobar, most (perhaps 95%) of the
nuclides are "born"  as I-135 or the shorter-lived precursors.  these nuclide decay
to Xe-135, some (perhaps 30%) by way of Xe-135m.  A small fraction, perhaps 3%,
are "born" as Xe-135 or Xe-135m.  If there were no significant neutron fluence to
interfere, these nuclides would decay to Cs-135 and a few (perhaps 2%) of the
isobar fission products would be formed directly as Cs-135.  I believe the number
of nuclides created directly as Ba-135 is negligible.  The number on the Chart (6.54
atoms per 100 fissions) is the sum of all the nuclides "born" into the isobar family. 
The number is the same whether the thermal neutron fluence is low or high, even
though in a high fluence environment, few of the nuclides would ever reach the
Cs-135 stage.  Of course, very few of the nuclides would ever be seen  as Ba-135
because of the 2.3 million year half life of Cs-135.

Of course, for an authoritative answer, you might want to contact the authors.  The
last time we talked, Sue Breneman was still at KAPL and still involved in this
work.

Charlie Willis
caw@nrc.gov