For times longer than one day, the results are
[4]
a(t) =~ 5.2 x 107° dé! 2 sec
and 38(t) +r(t) =~ (3.9 d7!e2 + 11.7 a7! +4)
x 1076 Mev/sec.
[5]
These results, which apparently are the source of the t7}-2 "law, “
suggest that there should not be a simple power-law dependence of the
external gamma-exposure rate as a function of time and that t “1.4 might
have been a better “law” over longer times.
Nevertheless, the t
-1.2
approximation was frequently used to describe the decrease with time of
the external gamma-exposure rate.
As an approximation, it was then a
natural extension to calculate an infinite exposure (IE) as
re = a(iy f emt2ut = 8D fe? | = 5R(1)aO°?
a
where a is the time of arrival.
the t"
°.
[6]
In such a calculation, the validity of
1.2 approximation is of major importance.
If, for example, a
more appropriate model were rl-4 » the infinite exposure would be
R(1)ao"4 70.4,
For an arrival time of 3 hr, the two models differ by
a factor of 4.0/1.6 or 2.5.
Recent analysis of the original data taken following the weapons
test HARRY (May 19, 1953) indicates that a more appropriate model of
the rate of decrease of the external gamma exposure rate is 7}-35
over periods of about 100 hr (Qu81).
Hicks (Hi82) has also performed
detailed calculations of the expected rate of decay of the HARRY and
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