errata

["Dale E. Boyce" <dale@radpro.uchicago.edu>]

My previous post was buggy.  The calc is corrected here:

Paul,

The method you posted is very similar to what I use to calculate
dose constants in Rad as opposed to R.

A source emitting 3.7E10 photons per second emits 1.332E14 photons
per hour(1.332 must be one of those cosmic numbers!:))
ADD> It therefore emits a flux of 1.332E14 /4 /pi /(100 cm)^2
ADD> = 1.06E9 photons/cm^2/hr

100 ergs is about 6.25E7 MeV so

Rad/hr at 1 meter = 1.06E9/6.25E7 * (1 - exp(-uen * 1 g)) * I * E
                    ^^^^^^Changed to correct flux

or nominally 16.98 * uen * I * E , which is then summed over all photons.

I then use uen for muscle instead of air.  I assume that the greater
than 15% difference for many isotopes is due to the difference in
R to Rad conversion that results from a nonlinear relationship
in uen between air and tissue.

The rule of thumb constant for the rad calc becomes:

Rad/hr/Ci at 1 meter = E * I / 2 summed over all photons.

This also is good from about 70 KeV to about 2 MeV.

Co-60 by rule of thumb then is (1.1173 + 1.332)/2 = 1.25 Rad/hr/Ci

Dale
dale@radpro.uchicago.edu

I agree fun stuff.