calculation is based on the formula:
5 xr x t = 1000
where r is the dose rate in r/hr at time t, and t is the time of
arrival of fall-out in hours.
This curve is also plotted in Figure 15.
It is worth noting that out to 20 hours it is still above the LD, curve
for acute lethality.
Figure 16 is an expression of the same data in
terms of the H+l hour dose rate.
It is constructed by taking the re-
spective dose rate measured at (t,) and extrapolating back to H+l hour
according to the gi? decay law.
These basic curves are used to de-
velop Figure 17 which shows the extent of downwind lethal effects along
the axis of the fall-out pattern for a 15 kmot mean wind.
This figure
indicates the effect of increasing yie1a™ on lethality expectation for
these downwind locations under this specific wind condition.
By estimating the crosswind effect on the fall-out distribution, the data from Figure 17 has been extended to express lethality
in terms of area as a function of fission yield and this is plotted in
Figure 18.
The reduction of lethal area accomplished by affording a
protection factor of 5 is also plotted in Figure 18.
As an illustra-
tion, assume that a 5 MI weapon is detonated on land surface.
The
unshielded LD,09 and LD) contour lines enclose 2200 and 3600 square
miles, respectively. If there is 80% effective shielding available,
the LD,,, area is reduced to 450 square miles and the LD, area to 1100
square miles.
The quantity of radiation accumulated from time of entry into
an area to time of exit from the area is calculated by the formula
De Rye - t.7"*)
{1)
D = total integrated dose of radiation in roentgens.
(2)
Ruy) = Radiation dose rate at H+l hour.
(3)
t, = Time of entry in hours after detonation.
(4)
ts = Time of exit in hours after detonation.
* For a thermonuclear weapon, the yield_is assumed to be derived from
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