Re: Bi207 -Reply

[FRAMEP@ORAU.GOV]

Dale Boyce wrote:

>What is the methodology used to determine
>the dose constants in the RHH?

Dale, if RHH refers to the latest pretender to the throne (just
joking), the constants came from Unger and Trubey "Specific Gamma Ray
Constants for Nuclides Important to Dosimetry and Radiological
Assessment" ORNL/RSIC-45/R1.  The equations are not difficult but
awkward to convey over the superhighway. I'll send a xerox copy of
them if you wish. 

The sources for the old RHH numbers would have used something like
the following:

gamma constant = 19.53 E I (uen/p)

where: the gamma constant is R/hr at 1 meter per curie
       E is the gamma energy in Mev
       I is the gamma intensity or yield in gammas per decay
       uen/p is the mass energy absorption coefficient in air in cm
squared per gram

For a radionuclide with multiple gammas a constant is calculated for
each and they are then summed together.

eg for Co-60  

 E1 = 1.1732  I1 = 1.0  and uen/p = 0.0269

Its constant is 19.53 x 1.1732 x 1.0 x 0.0269 = 0.616

 E2 = 1.332   I2 = 1.0  and uen/p = 0.0263

Its constant is 19.53 x 1.1332 x 1.0 x 0.0263 = 0.684

Adding the two constants together to get that for C0-60 we have

0.616  +  0.684  =  1.3 R/hr at 1 meter per curie

This is the same as the old RHH value when converted to these units.
If Co-60 had x-rays exceeding say 10 keV, these would have been
included in the calculation.

 Fun stuff!

Paul Frame
Oak Ridge Associated Universities