Re: DECAY-IN-STORAGE

["Patrick D. Beyer" <pbeyer@post.its.mcw.edu>]

We lets talk microspheres.......... The reason behind our including the 
activity from microspheres in our effluent, even though we all know that 
a majority of the activity stays in the ash, is due to three factors, 
Time, Money and Staff.

There are only 7 studies I was able to find that addressed 
the incineration of microspheres. They are all detailed in Emery and 
Sprau, 1990 - "retention and Subsequent release of raioactivity From the 
Incineration of Wastes Containing Microspheres", in the HPJ vol 59 no. 6 
(december) Pages 911-914. They summed up all the previous studies and 
incorporated them into a table. It appears from the table that ther 
retention rate can be from around 30 -100 % for some nuclides. Also all 
the microspheres we use are not included in the studies. With this broad 
of a range, we could not reliably estimate the ash retention for nicro 
spheres. One option was to perform our own study because it appears that 
the retention rate also varies according to the configuration of the
incinerator used. Well, This brings us to the point. No time, No money, No 
Staff (Also no good equipment either).

Before our license was renewed, our license was written where we assumed
that we had a 30 % retention rate in the ash. During our recent renewal,
we couldn't justify that (both to our selves and to the NRC, though we
probably could have sneaked it past them, but being responsible HP's we
didn't) so inorder to not lose this great disposal resource, we submitted
it as if 100% of the activity from all nuclides incinerated is exahausted
up the stack as effluent. But as i said before, being responsible HP's we
also keep the ash until there is no detectable activity. Our sampling is
very simple, we just use a calibrated detector with a NAI probe. Its not
very quantitative (as in microCi/g) but it does tell us if there is any
activity there. My only current concern is about s35 retention in the ash,
but seeing that we only burn very small amounts (< 1 micro Ci/yr) I'm not
too concerned. This also goes for p32 and p33. My goal is to eventually
find the time to perform a proper retention study as soon as those guys in
Biochemistry figure out how to clone me.........