repre
a
It is hoped that the chronic toxicity experiments now in progress at the University of Utah
can be extended so as to permit comparison of Sr-90 with Ra, MsTh, and Pu in dogs.
Such
a comparison would give a much more reliable conversion factor between Ra and Sr than is
now available.
2. 1-131:
In view of the probable importance of I-131 in GABRIEL, it would be desirable to compile
a critical review of the dependence of thyroid damage on I-131 dose. This will be done in the
near future. The sources of information are almost entirely in the open literature.
From the data previously presented, it is possible to construct certain conclusions about
the nature and magnitude of the radiological hazard to man from nuclear weapon debris. It
would be superfluous to emphasize that such conclusions are over-simplifications based on insufficient data whose pertinence to chaotic wartime or postwar conditions is limited. A crudely
estimated error is associated with each numerical value. When it is stated that a parameter
has a value of N with a probable error (PE) of a factor of 2, if is meant that the most probable
value is considered to be N, with an estimated 50% chance that the true value falls between N and
2N (i.e., a normal error distribution is assumed on a log scale).
The hazard may be expressed in a semi-quantitative manner by the equation:
2
te SOE a OF ae”
VI. CALCULATIONS AND CONCLUSIONS
H=F(q,t) D(0,t) S(o0,d,r)
where
H-=hazard
F(q,t) fallout in terms of quantity (KT of fission products/mi*) and time (days) after
detonation
D(o,t) average dose in rads to the organ concerned as a function of time after detonation,
for a failout of 1 KT/mi?.
S(o,d,r) sensitivity of the organ concerned in terms of damage as a function of dose and
dose rate. (See section V., G)
A. Fallout:
1. Airburst:
All debris falls out exponentially with time.
For shots whose mushrooms stay below the tropopause (approximately 100KT orless),
time for 50% of debris to be deposited on the earth’s surface is 20 days (PE—factorof 1.5).
For larger shots, whose clouds penetrate well into the stratosphere, there is essentially no
information pertinent to rate of fallout. It is expected, however, that the higher the yield
the less rapid the fallout. As a result of slow mixing of stratosphere and troposphere, half time
for fallout could be several times as long as for troposphere debris.
In any large scale war essentially all detonations would take place in the North Temperate
Zone. From troposphere clouds 75% (PE=factor of 1.2) of the debris would be deposited in
the N. Temperate Zone. From the stratosphere clouds, one might guess 60% deposition
(PE=-factor of 1.3) in the N. Temperate Zone. Assuming a half time for fallout of 20 days and
a mean time for debris to circle the world (easterly movement) of 15 days, fallout per unit of
longitude would vary around the world by less than a factor of 2 for an average shot. If
detonations took place over a considerable spread in latitude within the N. Temperate Zone,
few large populated regions would receive fallout (KT/mi7?) differing from the mean by a factor
16
7s,
Tos ARGHIVES
emer oo.
The following figures will be used in the calculations of hazard.