Re: DECAY-IN-STORAGE

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

Our research waste waste disposal at the Medical College of Wisconsin
consists of DIS, Incineration and Offsite Disposal. We are allowed to DIS
for any nuclide with a HL < 120 days and can dispose of any DIS waste
after 10 HL's (after conducting a proper survey of course). We then
incinerate the decayed waste to obliterate any radioactive markings,
though personnaly I would rather use a shredder if I had one. Currently we
are using DIS for S35, P32, P33, Cr51, I125, I131, Ru86, Ce141, Ru103,
Nb95. The wastes are segregated by nuclide and then consolidated into
18x16x18 craft boxes. We are in the process of implementing a new
inventory system for these items which consists of marking each box with
the Nuclide and a control number. The control number includes the month
and year stored. As the waste is packaged the waste tag is marked with the
control number and then the information is entered into the DIS database.
A listing is printed of what is in each box as a redundency and because i
don't carry my computer with me to the waste room. Also monthy a sheet 
will be printed listing what has decayed enough for disposal.

We currently have three waste rooms where we store items for DIS. All the
rooms are basically in areas where occupancy is not desired (back rooms in
basements) and all are constructed of either concrete or block walls. I
have found that 8" block does well as a sheilding material for all but the
higher energy gammas. Room number 1 is our processing room where we store
incinerator ash (from the incineration of radioactive microspheres, more
about that later), Bulk liquids, and also process the waste, ie. crush
vials, box DIS, drum waste for shipment. Room Number two is used as a DIS
facility for animal carcasses. In it we have 20 freezers that contain
animal carcasses that contain radioactive microspheres (Cr51, Ce141,
Ru103, Nb95). These are decayed prior to incineration to bring the effluent
levels to where the microshere carcasses only account for 50 % of our
total radioactive incinerator effluent (for 10CFR20 and yes we also check
for NESHAPS). Room number three is just used for the storage of DIS
packaged in boxes. Each nuclide is grouped into different areas
so we can find something when its ready to be disposed. We have 
approximatly 7000 sq. Ft of DIS space (including processing area). We 
have toyed with the idea of getting a compactor, but it seems we are at 
about equilibrium with our incoming/outgoing. 

Well, you may ask, What about H3 and C14, Those are normally incinerated, 
unless we have some graduate student who dreams up a protocol for using 5 
Ci of tritium to label something (with only a projected 1 % 
incorporation into his labeled compound!!).

As for incineration, we have a radiaovtive "burn" every friday. Our 
license is written so that the effluent released is a calculated as if 
100 % of each nuclide is exhausted. Becuase this is not based in reality, 
we hold the incinerator ash for 1 year or when a survey of the barrel 
reaches background readings. Our prelimenary analysis of the ash shows 
that the predominate residue is due to the Microspheres from the animal 
carcasses. We have no numbers as what % stays in the ash.



Pat Beyer
Office of Radiation Safety
Medical College of Wisconsin

No discaimers, this is what we do.....