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Re: Contamination Dispersion Cs 137
What I can tell you is my experience managing the Radiological Accident in
Goiania
The Source used in the teletherapy unit was Cs-137, in form of highly
soluble Cesium Chloride salt 137CsCl, and readily dispersible. This had been
compacted to form a coherent mass which was doubly sealed within two
stainless steel capsules.
The source's activity at the time of the accident was 50.9 TBq (1375 Ci),
gross source mass 93 gr, total Cs-137 activity mass at the time of the
accident 19 g
The Goiania Source was manufactured at ORNL, you can ask to R. Ricks
(REAC/TC) probably he can provide you good information. He was in Brazil at
the time of the accident, and we were curious about the "blue radiation"
Jose Julio Rozental
joseroze@netvision.net.il
Israel
----- Original Message -----
From: Mike Malaxos <mike@radiationsafety.com.au>
To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Sent: Tuesday, April 25, 2000 12:49 PM
Subject: Contamination Dispersion Cs 137
>
>
>
> >Hullo Group,
> My second attempt to get the formatting right.
> > I would like to see your comments regarding the
dispersion
> of contamination from a ceramic bead double encapsulated Cs 137 special
form
> source. I believe that information concerning the following experience
> would be valuable to many of us. A 5 year old 50 mCi Cs 137, ?? double
> encapsulated, X8 approx 6 mm x 8 mm ) source was removed from a density
> gauge source container for testing. The source was enclosed in an X 38 (13
> mm x19 mm) aluminium outer capsule to fit the cavity in a Density Gauge
> source container. The container label identified the enclosed source as 50
> mCi 1995. The thorough wipe of the X 38 outer aluminium capsule
> concentrating on the grub screw end was 2- 3 Bq. The X 38 capsule was
> installed in a holder in a hot cell and the grub screw removed to extract
> the source. When the extended hex driver was inserted into the grub screw
> it was found that the grub screw was fully inserted but only finger
tight.
> (it would not have compressed the source) As the grub screw was unscrewed
> from the capsule it was noted that the thread contained flakes of white
> material(probably a sealing compound). The rod holding the grub screw was
> withdrawn over the middle of the hot cell
> >and checked with a thin window GM detector. It was grossly contaminated .
> No attempt was made to measure the activity. It was replaced in the X 38
> capsule and the capsule transferred to a holding pig with contaminated
> waste. Care was taken to prevent the grub screw and screw holding tool
from
> touching another surface during the procedure. The rod holding the screw,
> the area over which it passed ( a track 20 cm wide), and a vertical
section
> of the hot cell wall 20 cm from the centre of the path was contaminated
> (probably 2 - 200 kBq in all) . Is it possible internal corrosion may have
> generated internal pressure causing tiny particles of contamination to be
> blasted out from the cavity when the grub screw was removed or could the
> particles of contamination been small enough to disperse over the area (in
a
> draft free location). I require information concerning the chemical form
of
> the Cs 137, the chemical and physical characteristics and retention
> capability of the ceramic. I would appreciate any information concerning
> previous occurrences of suspected internal pressure build-up due to
> corrosion in Cs 137 or Co 60 sources which could spread contamination or
> experience of dispersion of microscopic particles in still air. Is the
use
> of a fume hood considered mandatory when handling sealed sources. We now
do
> an additional wipe test when the source retaining screw has been
unscrewed
> about three turns to prevent a re-occurrence of this type of situation.
> >
> Thanks in advance for your comments.
> >
> >Best Regards,
> >Mike Malaxos.
> >Radiation Safety Services
> >Mike@radiationsafety.com.au
> >69 Robinson Avenue Belmont Western Australia 6104
> >Phone 61 (0)8 94750011 FAX 61 (0)8 94750011
> >
>
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