convention was adopted frequently that the exposure rate from material
deposited at a given location varies with time according to the
relationship
R(t)
SN
R(1) tv?
[1]
Ff
~~”
where, A(t)
Exposure rate at time t in hr, and
fo:
2 “RQ) = Exposure rate at 1 hr.
é
f-
—
aie
This has beceimeknown as the t"“1.2 "law," but the relationship was
originally derivedas an approximation (Wa48) of the rate of decay of
fission-product pete
actiy ty.
It is instructive to note that Way and
Wigner (Wa48) actually| taldulated two quantities: the rate of betaparticle emission as a functionof time, 8(t), and the rate of total
energy emission as a function-oFtime, 3B(t) +1P(t); where B(t) is the
rate of total beta-energy emission, ane-T(t) is the rate of total
gamma-energy emission.
Neither of-these quantities is an appropriate
analog of the external gamma-exposure rate for the resulting fallout
field, but presumably the rate of total energy emission would be the
better analog.
The results of Way and Wigner's calculations for
t.< 1 sec are
6(t)
zy
©”
(0.38
-
2.6t)
/sec
_
—-
and 38(t) +T(t) =~ (3.8 - 0.61t) MeV/sec * —
205
[2]
[3]