PREDICTION OF SUBSURFACE-DETONATION FALLOUT
33:
product radioactivity is unfractionated and that 1 kt of unfractionate:
fission products spread uniformly over 1 sq mile corresponds to a:
(H+ 1)-hr dose rate of 3380 r/hr at a height of 3 ft above aninfinit:
plane.! This normalization constant of 3380 r/hr is corrected for ter.
rain shielding by a factor of 0.8.
Certain atmospheric processes or effects have been neglected i
developing the cratering fallout model, just as these same effects wer:
neglected in developing the land surface-burst fallout model:?
1. The effect of synoptic-scale vertical motions on the vertica
displacementof the falling disk of particles.
2. The effect of ‘the mean divergence of the horizontal wind on th
radius of the disk of falling particles during descent.
3. The effect of vertical eddy diffusion.
4. The time from detonation to cloud stabilization.
9. The development of subsynoptic-scale wind systems.
6. Changes in time and space of the shear tangential and norma
to the horizontal wind at cloud-top level.
7. The effect of water products of condensation on the size and fal
rate of radioactive particles.
Fraction of Gamma Activity in the Close-in Pattern
For calculation of the close-in fallout pattern from a subsurface
detonation, the fraction of the gamma activity produced by the fissior
yield and appearing in the close-in fallout pattern, F,, must be known.
Thus far, experimental data fromthe Sedan, the Teapot ESS, the Jangle
U, the Neptune, the Jangle S, and other surface-burst shots have pro-
vided a basis for estimating F,. The measured fallout patterns fror
these shots have been integrated’ from the radius of direct throwouttc
the limit of themeasured pattern. The results are shown in Table 1.
These F., calculations were performedby assuming a normalizatior
constant of 3380 r/hr per kiloton of fission yield per square mile at
H+ 1 hr and a terrain shielding factor of 0.8. The graphical presenta-
tion of F. as a function of z/W
is shown in Fig. 1. In construction of
the experimental F. curve, the following asymptotes were used: (1) an
Table 1-—- EXPERIMENTAL DATA
Shot
W, kt
z, ft
F.
Medium
Sedan
Teapot ESS
Jangle U
Neptune
100
1.2
1.2
0.115
635
67
17
100
~0,10
0.46
0.64
0.005
Alluvium
Alluvium
Alluvium
Tuff
Danny Boy
Blanca
0.43
19
109
835
' Jangile S
1.2
0
0.50
0.04
0.0005
Alluvium
Basalt
Tuff