Micorshield

["Case, Diane (OD)" <DCase@exchange.nih.gov>]

I compared the exposure rates from a point source at one meter found with (1)
Microshield 5.01 and by the (2) gamma dose constants listed in ORNL "Specific
Gamma-Ray Dose Constants for Nuclides Important to Dosimetry and Radiological
Assesment,"by Unger and Trubey.

These are my results in mR/hr at 1 meter from 1 mCi, in air, no Buildup:

Tc-94m  	MS =1.05 		Hand calculation  = 1.15
Fe-59		MS = 0.620		ORNL =  0.662
Ba-133		MS =  0.287 		ORNL =  0.455
Sm-153		MS  = 0.055		ORNL =  0.090
Cr-51		MS  = 0.0175		ORNL  = 0.0234

Notice that Ba-133, Sm-153 are off by about a factor of 2, and Cr-51 slightly
off.  I have taken everything into account...... different energy groupings,
compared the energies and yields used, cut-off energies (i.e. in ORNL, only
gamma rays of E>0.01 MeV were used), etc........ (In fact, if I rememember
correctly, I got Microshield to give closer values to those listed in ORNL if I
DID include E<0.01 MEV..)

I asked Grove Engineering about it, and I didn't get an answer.
This is a very simple test case. Why are Ba-133 and Sm-153 off by a factor of 2.
How about other radionuclides?  Anyone want to try it out?

Please enlighten me, but please do so by running the case yourself and making
sure that your theory is correct. Please don't just give a suggestion, because
chances are I've already tried it.  I'd really appreceiate a solution.

Thanks.

Diane Case
dcase@nih.gov
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