X-Ray Shielding Requirements

[MAJ Don Jordan <djordan@osiris.cso.uiuc.edu>]

This is the first time I have tried to send a message so will apologize
ahead of time for any breechs of internet decorum.  I am looking for any
information relating to the practical impact of the 100 mrem
nonoccupational annual dose limit on medical/industrial x-ray facilities
whose shielding requirements were initially determined using NCRP 49 and
the previous 500 mrem/yr nonoccupation dose limit.  As you might guess,
retrospectively applying the NCRP criteria with 100 mrem limit
significantly increases the calculated required shielding.  In fact, all
other parameters being the same, using the NCRP methodology with the 100
mrem limit would require many of our medical/industrial x-ray facilities
to be extensively modified to add additional shielding.  As I believe the
NCRP 49 calculational methodology is very conservative (overestimates
shielding required), the practical impact, as shown by the results of
environmental/area surveys or other methods, may not be that great.  Any
information or view points would be appreciated.