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Re: Contamination Dispersion Cs 137
Further information is needed concerning the source manufacturer and
encapsulation to respond to your inquiry.
You indicate an X8 or X38 capsule. I am not aware of anyone with an X8 model
number any more. Amersham at one time had some x numbered sources.
I also find it hard to believe that anyone would encapsulate Cs-137 in an
Aluminum capsule.
The early Ceramic Cs-137 sources were Cesium Chloride taken up on
Montmorillonite clay and were not fired. Later on some were glazed and fired.
Still later, other types of ceramics were utilized. Some were powder type
ceramics such as microspheres. Others were pressed and fired pellets. Most of
the ceramics disappeared about 7-10 years ago and glass became and remains
the preferred source material.
The use of doubly encapsulated stainless steel has been the norm for the last
20 years. Heliarc welding has also been the norm although many of the
microsphere sources were silver soldered. The use of Aluminum has never been
the norm. I am surprised that any regulatory agency would authorize
encapsultion of 50 mCi of Cs-137 in Aluminum.
With respect to contamination, we have recovered ceramic pellet Cs-137
sources where the capsule has been cut in two. We were able to remove
significant activity from the source but all of the activity was in the
particulate of the ceramic. We did not see the activity transferring to other
surfaces.
The white mterial you have described may very well be Aluminum oxide or
hydroxide from the oxidation of the Aluminum. I am unable to determine what
type of facility the density gauge is at but, if it is a cement manufacturer,
we have seen Aluminum components of equipment corroded away by the caustic
nature of the cement.
With respect to the movement of the activity, I would doubt that there was a
pressure buildup within the source. I would believe the problem is one of
airflow and dust. The activity, if particulate should come off the
contaminated surfaces with a damp paper towel. If it does not, I would guess
that the source was Cs-137 Chloride baked onto clay.
While the use of a fume hood is not required for handling sealed sources
normally, when handling a source holder with significant corrosion evident or
sources encapsulated in anything other than doubly encapsulated stainless
steel, it would be advisable. If for example, one is removing a thin window
source of Am-241, I would recommend the use of a glove enclosure if there is
any possibility that source is stuck in the unit and could rupture.
ROBERT D GALLAGHER
NSSI
713 641-0391
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