Noble gasses in power plant accident scenarios -Reply

[Charles Willis <CAW@nrc.gov>]

Joelle,

Generally, we do not make a distinction between the noble gas compositions of gap
and fuel damage releases, but a difference is possible.  

In a gap release, the cladding is presumed damaged thus releasing the noble
gasses that had diffused out of the fuel and collected inside the cladding.  The
composition would depend on the half lives and the diffusion rates of the various
nuclides.  The diffusion rates of Xe and Kr, of course, are different and the half life
of Kr-85 is exceptionally long in this context.

In a fuel damage release, generally the fuel material is assumed to reach melting
temperatures.  Consequently, the noble gas release consists of the nuclides that
have built up in the fuel.

Charlie Willis
caw@nrc.gov