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Re: Decommissioning problem
Greg,
The metal is probably cadmium. Concerning the contamination, it would be
fairly simple to test for radon daughters. Determine the half-life of the
contamination and compare to the decay table for the U-238 decay chain, or
the Th-232 chain. If you have access to a good alpha spectrometer, look at
the alpha spectrum for a 3 min alpha at 6 Mev from Radium A, and a 7.7 Mev
alpha from Radium C'. The half life of this higher energy is so short, the
apparent half life will be about 20 min, the half life of Radium C. If the
contamination is due to radon daughters, bag it and wait for a few hours.
If it is due to thoron daughters, it will take a few days.
Fred Haywood
----------------------------------------------------------------
"Greg Krause" To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
<greg_krause@operations.und. cc:
nodak.edu> Subject: Decommissioning problem
Sent by:
radsafe@romulus.ehs.uiuc.edu
08/15/2000 02:57 PM
Please respond to radsafe
I inherited the clean up of an old subcritical reactor. The fuel and PuBe
sources are gone (thank you Sherry Jones and the Y-12 people), but:
the fuel and other U itmes were stored with Aluminum reactor components in
a small sealed room for many years. All of the Aluminum items now appear
to be contaminated when I perform wipe tests on them using liquid
scintillation. Other items in the room: cardboard, wood, steel don't
appear to be contaminated. Is this consistent with deposition of radon
daughter products? (leaded glass is also contaminated while the metal frame
is not.) Contamination levels appear to be around 300 - 1000 dpm/100 cm2.
The contamination appears to wipe off easily with detergent, so I have a
choice of contaminated aluminum or contaminated paper towels. Assuming
that the contamination is radon daughters, how to dispose of the bags of
towels?
Final question: although I got rid of the PuBe sources, I still have the
storage container. Its a large aluminum can filled with parafin, but would
anyone know what the thin sheet of soft, gray metal is that's apparently
used as the thermal neutron absorber? I need to know, because unless
someone out there wants it, I intend to send it to the landfill. The only
info I have on the container is that a tag on the outside reads: Universal
Nuclear, New York, NY
Greg Krause, P.E.
Director, Radiation & Chemical Safety
University of North Dakota
701-777-3341
greg_krause@operations.und.nodak.edu
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