Absorption Coefficients for Sheet Rock

[VERNIG.PETER@FORUM.VA.GOV]

Group,
First, I doubt all of RADSAFe is interested.  Please send me a new
message unless you're sure your system doesn't automatically send
replys to the sender and think the sender is RADSAFE, ie it goes to
the whole list.
 
I am looking for absorption coefficient for concrete and sheet rock
or wallboard or lead equivolents @ 76 kVp or as close as I can get.
I've found a few things in Radiologica Health Handbook and new HP &
Rad Health Handbook.  But nothing below 150 kVp.
 
Also has anybody seen anything published on the NCRP 49 recommendations
wrt secondary barriers applied to x-ray bone densitometers?  Please
don't respond to tell e that bone densitometers don't need secondary
shielding or shouldn't or have very low leakage, etc.
 
Thanks in advance.
Peter G. Vernig, VA Medical Center, Denver, CO 
vernig.peter@forum.va.gov