Re: NDT of diagnostic x-ray rooms

[Bob Wilson <bmwils2@pop.uky.edu>]

David,

I have used both Am-241 and Tc-99m.  For diagnostic x-ray energies, I find
Tc-99m will give superior results, plus it is cheap.  One can use a
relatively light-weight vial shield and make a handy "gamma camera" that
give a collimated but conveniently broad beam.  the main concern is that it
is liquid and can be broken.  In tests, I have found it to provide an
almost exact lead thickness result.  For testing unknown walls, the source
to detector distance must be well controlled and consistent.  I use a 1
meter distance unshielded reading, comparing to the 1 meter readings
through a barrier (I prefer to use an ion chamber, but any detector is
fine).  "Walkie-Talkie" radios are great to coordinate between the person
maneuvering the source and the person taking the measurements.

My tests indicate that it will require about a Ci of Am-241 to be generally
useful, and the Am x-ray is a much higher energy than diagnostic x-ray.
For sheet lead, this means that the thickness resolution is not so good.

There are some really good Australian papers on using Am, however.

Bob

At 04:55 PM 3/13/00 -0600, you wrote:
>dear all
>
>we have a need to perform NDT of diagnostic x-ray rooms (perhaps up to 2.5 
>mm lead) in remote locations i.e. need a procedure which is simple, 
>versatile and very transportable.  we are thinking of using a sealed source 
>of Am-241 in a suitable container & a sensitive survey meter-type detector.
>
>i have 2 questions:
>
>1.  is this the optimum method?  what do others do?
>
>2. where can we obtain a >= 500 mCi Am-241 source?
>
>many thanks! 
> =================================== 
> David Thiele PhD 
> Manager, Statewide Medical Physics 
> Biomedical Engineering & Health Technology Services (7D) 
> Royal Brisbane Hospital 
> Herston  Qld  4029 
> Australia 
>  ---------------------------------------------------- 
> Phone: +61 7 3636 7896 
> Fax: +61 7 3636 3518 
> Email: thieled@health.qld.gov.au 
> ===================================
>
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Bob Wilson, Director
Radiation Safety Office
University of Kentucky
102 Animal Pathology
Lexington, KY  40546-0076
W:	606-323-6308
FAX:	606-323-4752
bmwils2@pop.uky.edu
http://www.uky.edu/FiscalAffairs/Environmental/radiation/
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