ual radiation from fallout will follow approximately the expressions:
i = tt?
and
2
r=
A
(1.1)
dt = 5], (ty? ~ t, 4)
ty
Where:
Kk = exposure rate at time t
I, = exposure rate at unit time
t = time
r = exposure between times t; andt,, where t = 10 seconds.
It is expected that the decay of the residual radiation will vary with device design. For
example, the presence of Np”** would tend to decrease the absolute value of the decay exponent
for a period of time.
4
YT
X
EXPOSURE ROENTGENS
3,
\
LN
\
GAMMA
10"
‘NX
X
S
N
Xx ‘\
<
__-—FISSION PRODUCTS
GAPTURE TO FISSION RATIO #Q5
“oC REFERENCE 8)
NN
w
nin aw \
-
‘\
~“
io”
N
_
‘NX
=4
~~
NC >
10
Ny
3
3
DISTANCE FROM GZ, 10° YARDS
‘
NN
ae
Figure 1.1 Gamma exposure for 1 kt surface burst.
1.3.3 Absorption in Air. The absorption of unscattered gamma radiation in air is exponential
with distance. From a point source of mono-energetic radiation, the variation of intensity with
distance is expressed as:
hel?
Ip ~
(1.2)
47D2
11