The value ofMe a is relatively constant within 20% of the maximum
value over the gamma energy range of 0.13 to 1.9 Mev.
all of the important gamma contributions.
This range includes
The average E @ fromthe preceding
table is 0.5) Mev, anda value of£, of 1.06 x 1073 #t-l is justified for
all calculations.
For simplicity, it is desirable to use a single average energy.
From the table, it is apparent that the error involved in using 0.5) Mev is
negligible in comparison with other uncertainties in calculation.
Since the distribution of gamma energy with mass is apparently
random, the difference in energy distribution between slow and fast fission
has been ignored.
This allows the simplification of the dose formula to,
Dose Rate = 6.64 x 10-10 n,
millirads/minute
Where N, is the number of gamma d/m/ft® at time t.
Derivation of Time Function
Assuming beta decay follows the t7/** law, it is possible to calculate the total mumber of beta disintegrations which will result from a
5
¢
a
U U
given sample,
7200 Ny
(te - tp)?
(tg
-
t,) 9?
Total /b disintegrations/ft* frou cacplicg day to infinity.
fe
d/m/ft® on counting day.