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Uranium-containing wafer disposal
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Dear Radsafers,
After having consulted with one of my colleagues and searching the RADSAFE
archives, I find that I need to try and tap the collective wisdom of the
list regarding how to properly dispose of uranium-containing wafers found
in one of our labs. Apparently, the wafers were sputtered with uranium at
a facility other than our own, but at some point, the wafers found their
way to our site and the potential radioactivity issues went unrecognized.
Based on a rough calculation made by the researcher who brought the
situation to the attention of EH&S, the mass of uranium is estimated to
range between 1 and 10 mg -- probably closer to the lower end.
One reference I consulted (Radiation Protection (3rd Ed.) by Shapiro)
states that in naturally-occurring uranium the respective percentages of
U-238, U-235, and U-234 are 99.72%, 0.72% and 0.0054% and gives respective
specific activities of 3.34E-4 and 2.14E-3, and 6.19 microcuries per
milligram. If one uses 10 milligrams as the worse case estimate of the
mass of uranium present and assumes that nearly all of that uranium is
U-238, we are then looking at just under 4 nCi of radioactive uranium. If
I break the estimated quantity of uranium down using the relative
percentages and the respective specific activities, then I have 3.3
nanocuries of U-238, 1.5 nanocuries of U-235, and 3.3 nanocuries of U-234.
When I look at some of the tables in 10 CFR 20, I see limits with respect
to effluent discharges to air, water, and sewers, but no limits applicable
to solid materials other than quantities exempt from labeling (1 nanocurie
for U-234 and U-235 and 100 microcuries for U-238 per Appendix C of 10 CFR
20). Using the labeling exemption quantities, it would appear that I am
slightly above those limits with respect to U-235 and U-234, but I could
just as well be slightly below those limits if I go with the lower end (for
example, 2 mg) of the estimated quantity range.
Any practical suggestions you might have for addressing the proper disposal
of this particular type of NORM (uranium-containing wafers) would be
appreciated. If nothing else, it would be helpful to receive comments
from list members on the above assessment and the appropriateness of
applying the labeling exemption quantity limits to this situation. If not
those limits, than which limits?
(My apologies for the possible duplication of this posting during RADSAFE's
transition from its previous server location to its current one).
Thank you for your assistance.
Regards,
Stephen
Stephen Hemperly, MS, CIH, CSP
West Region Occupational Health Services (Safety, Industrial Hygiene,
Ergonomics)
Internet address: shemperly@almaden.ibm.com
T/L 457-1375, (408) 927-1375 Fax: (408) 927-2100
Almaden Well-being Services:
http://resalm1.research.ibm.com/projects/gohs_alm/home.nsf/Home?OpenPage
IBM Employee Well-Being:
http://w3-1.ibm.com/hr/us/ohs/gohsweb.nsf/well-being
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Date: Mon, 19 Mar 2001 08:40:38 -0600
From: PBarring@KDHE.STATE.KS.US
Subject: Re: "The Secret Word"
Easy, Sandy. The whole thing was meant in fun. Nobody REALLY believes
that changing the name will help. It is rather funny though that sometimes
it does work. K-mart is now BigK and they haven't suffered for it. I am
not ashamed of being a nuclear worker (an NO I don't glow) and I DO post my
name. The whole thing was a fun Friday thread. I you want boring tech
talk all the time read RADRAP or the NRC news page. Most of us here are
here for the discussions and comments serious AND funny. Please don't take
offense at good natured humor. If we can't laugh once in a while we'll all
be up on rooftops in no time. BTW, MY spot across from the Greenpeace
building is reserved, thank you very much.
"Just a voice in the darkness"
Phil
Philip Barringer
Kansas Dept. of Health and Environment
785-296-6342
IMHO this thread should end.
It's bad enough that there are many on this listserver who aren't
willing to identify themselves, unwilling to stand behind their own
statements. Now we have a thread (where some is only sated in
humor) who aren't willing to stand behind the profession they
chose.
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