RE: NDT of diagnostic x-ray rooms

[Dave Derenzo <dave@uic.edu>]

Dear Louie,

When I said collimated, I used the term loosely.  What I meant was, shield 
the back end of the source so that the radiation is only pointed toward the 
wall being checked.  This will reduce the exposure of anyone (including the 
surveyors) that need to be in the x-ray room while the test procedure is 
being conducted (ALARA consideration).   Use of a  flood source is a good 
idea, but it is less readily transported (the original question referred to 
remote locations).

Dave Derenzo


At 07:25 AM 03/15/2000 -0600, you wrote:
>We use our Co-57 flood source for the check of walls.  It is often hard to
>find the source when it is collimated to a small spot.
>
>As far as using Am-241 - remember it is hard to get rid of once obtained.
>
>Further, the energy spectrum for x-ray is considerably different than that
>of a rad source.  So if you use your readings/measurements to calculate the
>wall attenuation and then determine if this meets your requirements as
>determined for the x-ray system, great.  If however, you mistakenly think
>the source's attenuation characturistics mimic the x-ray, think again.
>
>Louie Tonry, CHP
>U.S. Army
>C, HEalth Physics
>louie.tonry@se.amedd.army.mil
>
>-----Original Message-----
>From: Gary Isenhower [mailto:garyi@bcm.tmc.edu]
>Sent: Tuesday, March 14, 2000 5:42 PM
>To: Multiple recipients of list
>Subject: Re: NDT of diagnostic x-ray rooms
>
>
>We also use Tc-99m, but we use a scint for the measurements because that
>allows us to use only 7 or 8 mCi and still get a good reading inside and
>outside the room. The exposure is not high, but your collimator method is a
>good idea for the inside measurements - I should adopt it.  I have a simple
>spreadsheet that corrects for background and attempts to guess the lbs/ft2
>in the wall - let me know at garyi@bcm.tmc.edu if you would like a copy.
>
>Gary Isenhower
>Baylor College of Medicine
>713-798-8353
>
>-----Original Message-----
>From: Dave Derenzo <dave@uic.edu>
>To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
>Date: Tuesday, March 14, 2000 9:09 AM
>Subject: Re: NDT of diagnostic x-ray rooms
>
>
> >Dear David,
> >
> >You can use a Tc-99m source, which should be readily available from your
> >nuclear medicine department.  Use the lead pig as a shield and collimator
> >and point the open top at the wall of interest.  In the past I have used  a
> >Co-57 dose calibrator source too.  Transmission through lead for Tc-99m is
> >approximately:
> >
> >0.1 mm lead - 65.5%
> >1 mm lead - 8.1%
> >2 mm lead - 0.8%
> >
> >You can use a geiger counter to make the measurements.  Have fun.
> >
> >Dave Derenzo
> >
> >At 04:54 PM 03/13/2000 -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
> >>  ===================================
> >>
> >
> >Dave Derenzo, RSO (dave@uic.edu)
> >UIC Radiation Safety Section, M/C 932
> >Phones: Voice (312) 996-1177  Fax: (312) 996-8776


Dave Derenzo, RSO (dave@uic.edu)
UIC Radiation Safety Section, M/C 932
Phones: Voice (312) 996-1177  Fax: (312) 996-8776

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