Re: Re Special Form Certificates Applied to Old Sources.

["Mike Malaxos" <mike@radiationsafety.com.au>]

>
> --On Thursday, February 22, 2001, 8:03 PM -0600 Emil Murat
> <kerrembaev@yahoo.com> wrote:
>
> > Mike,
> >
> > This is one of those cases.
> >
> > 1. Nobody thinks, what will be in fifteen years, when
> > they are buying a gauge ...
> >
> > 2. How much does it cost to change containers?
> >
> > 3. May be it is the time to buy a new gauge?
> >
> > 4. I would suggest you in any situation to do
> > ADDITIONAL leak tests to check and to show.
> >
> > 5.1. To check that if it is still sealed alright.
> >
> > 5.2  To show your regulator that you are aware about
> > the problem.
> >
> > 6. Not to offend the other side of the aisle:
> >
> > Regulators are also humans and they can understand
> > your problem and may be you will get a break.
> >
> > 7. Or just buy a new gauge.
> >
> > 8. If I were you, I would buy a new, if I had the
> > money, of course.
> >
> > 9. For mind sake, just do not repeat the mistake of
> > you predecessors and buy gauge with "Unlimited
> > millage"
> >
> >
> > I have a question of my own:
> >
> > Is there a technical reason for 15 years limit on
> > certificate or it
> > is just a business driven decision?
> >
> > They won't sell too many gauges if Y'all could use
> > them for too long. Right?
> >
> >Emil,
            The following answer to your question concerning the recommended
working (RWl) life is my opinion only.
            RWl is that time after which the source (if used in benign
environments) should be re-examined or discarded.
            The RWLshould be reduced if used in harsh environments. As far
as I know there is no mechanism yet in place in which the manufacturer or
some other organsiation approved by the manufacturer re-tests sources and
recommends an updated RWL commencing atthe time of the inspection.
When considering the older Troxler moisture density units the two sources
must be considered seperately.
The  double encapsulated stainless steel density source (usually 8-10 mCi Cs
137 as CsCl in a ceramic matrix to reduce the potential for dispersion) has
the potential to corrode internally because any traces of water remaining
absorbed in the ceramic
have the potential to become HCl. I have not seen any data indicating the
frequency of the developement of this type of fault.
The Source is permanently enclosed in a cavity formed by a cup with a wall
thickness of about 2 mm screwed onto the end of the rod which is welded into
position.  Unless it has been subjected to very severe damage contamination
would be contained inside the rod cavity. However even the the ceramic may
reduce the dispersion the ceramic does not prevent the release of
significant contamination when the capsule has a flaw.  I have seen a badly
contaminated capsule which looks okay.

I may add a bit more about the 40 mCi Am 241 Be source later if you are
interested.



Best Regards,
Mike Malaxos.
Radiation Safety Services
Mike@radiationsafety.com.au
www.radiationsafety.com.au
69 Robinson Avenue Belmont Western Australia 6104
Phone 61 (0)8 94750011 FAX  61 (0)8 94750011

severely



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