dene ee em Sk ee ee ee
-
mee
DNA 1240H-2
time.
However, in any case, its possible range is lese than:
(max),
a5
ts
-1.2 «<
a
g{max)<,(max),
do
7
ty
-1.2
The lower limit would result if all the activity were suddenly deposited
at tr; the upper limit would result if essentially all the activity were
(These two situations are of course not teats
suddenly deposited at t,.
they are introduced only to show the bounds of possible values of a‘™*/),
For the linear buildup assumed differentiation shows that q (max)
always occurs at t = 6t,,since
tety e722 (tye tE ty),
a= a{max) —G
(17-27)
Thus if te < 6ty, as is generally the case then
(7-28)
(max) - (mex) tet?
and if tee St;
(max)
(max )
.
> dp
ty
(6t4)
~1.2
(17-29)
—-1
ty
Values of t, and ty may be estimated from Ref. 2,
from a fallout model.
or may be obtained
The calculated results of the above equations represent doses
caused by radiations from sources deposited and remaining on an in-
finitely large flat retentive surface, where no drainage or runoff of
the active material occurs. The calculations could apply to the dose
on the deck of an aircraft carrier with no operating washdown system.
If washdown were operating, the dose would be reduced to 0.1 or per-
haps 0.05 of the calculated value. The dose is substantially less,
also, for ships with weather decks of smaller size. Figures 20 and el
of Ref. 67 graphically present factors that may be used to calculate
the reduction of the infinite-plane dose or dose rate which results
when the deposited activity lies on a finite area.
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17-80
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