SLIDE 33
External exposure rate,
Rate of rise in exposure rate at Rongerik Atoll was
measured by a monitoring instrument for one-half hour.
A best fit of the
results yielded an exponential rate of rise in exposure rate.
The exposure
rate peaked within an hour after the arrival of fallout at Rongelap and Sifo
Islands.
Arrival time and peak exposure rate were estimated by us based on
granule size considerations and the rate of activity deposition.
The estimate
of rate of rise was in agreement with the rate of rise observed at Rongerik.
The exposure rate peaked within 3 hours at Ucirik. Decline of exposure rate
was based on the decay of 142 nuclides which precursed the Bikini Ash. The
exposure rate histories at Rongelap, Utirik and Sifo Islands were normalized
to the results of the radsafe survey teams of the USS PHILIP and USS RENSHAW
COCg8). The mean exposure rate at Rongelap was estimated to, peak af 521 x
10°?
€ kg bh”
(22 Rh“). At Utirik phe peak yas 1.5 x 10° C kg
h~ (0.59
Rh!) and at Sifo 5.2 x 107°C kg h~ (20 Rh ~). After the cessation of
fallout the exposure rate ratio between Rongelap and Sifo Islands was 3.0 to
1.0 and between Rongelap and Utirik Islands, 9.5 to 1.0.
o
o
O
:
%r
i
"
5 = Oe
ao>
419.005
Fo Evacuation |
=a:
Sw S:
Q
Se
25 |
%
ew {0aS ft
Of
S2 0505
UTIRIK
]
ae
;
=7
i0.001
2°
S
4;
lu &
i
_ 30000
8 BE
KON
\y
i
|
|
ONL
oc
ae
2S
of
23
0.00005
Liou
10
.
{2
100
HOURS POST DETONATION ON MARCH |, 1954
35