RE: ?-Chart of the Nuclides

["Fulmer, Philip" <philip.fulmer@cplc.com>]

Quoting from the introductory text at the beginning of the Chart of the
Nuclides, "The fission yields...are total cumulative chain yields (in
percent) of the last isobaric chain member."  In that respect, the
yields in the Chart of the Nuclides are sums of the independent yield of
the fission product and the independent yield of all its precursors.  So
for Cs-137, the yield in the CON is the yield for Cs-137 produced
directly from fission and the yield of other -137 isobars that decay to
Cs-137 (same for Cs-135).  Thus, the yields are calculated based on two
mechanisms: a) fission and b)radioactive decay of a precursor.  Neutron
absorption in the reactor is not taken into consideration in the
derivation of these yields.  HOWEVER, the point that Brian has been
TRYING to make is that in a REAL reactor, the Xe-135 will absorb
neutrons and be removed from the -135 isobaric chain so that in reality,
any isobar downstream of Xe-135 will have a measured yield that may be
much less than the published yield in the Chart of the Nuclides.

Same disclaimers as usual (if I've muddied the waters further, my
apologies).

Philip

__________________________
Philip C. Fulmer, PhD, CHP 
Carolina Power & Light Company
Harris Energy and Environmental Center
3932 New Hill-Holleman Road
P. O. Box 327
New Hill, NC 27562-0327
philip.fulmer@cplc.com
(919) 362-3363      

>----------
>From: 	Zack Clayton[SMTP:zack.clayton@epa.state.oh.us]
>Sent: 	Thursday, January 29, 1998 8:45 AM
>To: 	Multiple recipients of list
>Subject: 	Re:?-Chart of the Nuclides
>
>I am unclear about what seem to be two different interpretations of the
>fission
>product fractions on the Chart of the Nuclides going on in theis thread.  
>
>Some of the replies seem to indicate that this is a number based on end
>product
>neutron capture by the fragments.  (Which it seems would have a natural
>"endpoint"
>or equilibrium built around nuclides with reasonably long half life and small
>neutron
>capture sections.)
>
>The other seem to indicate that the fraction is the primary fission daughter
>that is
>then subject to neutron capture or other decay.
>
>These seem to be mutually exclusive interpretations.  Am I missing something?
>
>Zack Clayton
>zclayton@epa.state.oh.us
>
>