{
vo
~
Bikini lagoon contamination of consequence was confined to lagoon areas containing suspended sediment. For the first few days this area was confined to the western quarter of the
lagoon, This radioactive sediment washed over the western reef, out through the southwest
passage, or settled to the bottom of the lagoon in a period of three days.
No alpha activity was detected in swipes about the living areas of the Task Group.
wee ee
.
(b)
_. A partial Rad-Safe survey was conducted on Runt I Day with incompleteatoll
results (Table 4.2). Results of this survey indicated no extensive recontamination of the atoll
cowtar See me
Table, 4.2 4
RADIATION SUMMARY IN ROENTGENS PER HOUR
Extrapolated
H+4 hr
Island
—
———
+1 day
went
~
back
~
ground at
+2 days
Enyu
Bikini*
0,03
0,20
0.03
0.12
0.06
0.14
0,03
0.12
Aomoen*
Romurikku*
Uorikku*
0.80
1.6
0.€-1.4
0.80
1.7
1.4
0.60
0.75
0.85
0.22
1.1
1.2
1.3
Yurochi*
0.8-1.0
Namu*
2000
1.0
1.3
100
0.6
Bokobyaadaa*
Ourukaen
1000
0.04
50.0T
0.10f
55
0.16%
1.2
0,04
Arriikan
0.02
0,403
0,32%-
0,02
Eniirikku
0,005
0.005
0.01
0.08.
0.05
0,01
Eninman
0.012
0,012
0.06
°
Airukiiji
0,02
Crater
0.01
11006
Ships
/
*Contamination by.
0,02-0.04
——
—
__ Shot.
+200-ft altitude, “~
yRadiation shine from water in southwest passage,
-
SAt 300 ft.
except within the Bokobyaadaa-Namu chain. An unforeseen fall-out of radioactive mztcrial Jess
than 5 p in size did occur on the night of*
+1. This fall-out covered the atoll and raised
radiation levels by approximately 100 mr/hF.Because ofthe late period of fall-out, this
radiation level would have corresponded to 3.5 r/hr fall-out at H+2 hr.
Because of small particle size this fall-out was much more difficult to decontaminate than
the macroscopic particles off
;
Secondary fall-out leveled off between v700—0800M,
+2, Residual topside levels on
ships were Ainsworth, 8 mr/hr; Estes, 12 mr/hr; and Bairoko, 30 mr/hr. Maximum levels
were 20 to 45 mr/hr.
Lagoon contamination covered the western quarter of the lagoon with levels comparable to
those of
\ Lagoon flushing through the southwest passage materially increased background-raaiation levels in the vicinity of Ourukaen, Bokcactokutoku, and Bokororyuru.
(c)
A partial Rad-Safe survey was conducted on,
__.., Day with in-
complete atoll results (Table 4.3), Results of this survey did indicate that Bokobyaadaa, Namu,
Eniirikku, Bikini, and the Yurochi-Aomoen chain were materially contaminated. Reentry and
recovery were accomplished to a large degree on shot day. No secondary fall-out was detected
as results of this shot.
Lagoon contamination was restricted to a V-shaped pattern with apex at Eninman and tips
covering the Bokoby2zadaa-Aomoen area. A reading of 100 mr/hr was obtained over the Enin.
68