~
3.3.2 Shot 1. The data gathered by the Bikini Atoll surveys and collectors were supplemented by surveys performed on the atolls that were unexpectedly contaminated. The
major portion of the pattern, which occurred over the open ocean, was not documented.
However, an analysis of the wind structure during the fallout period was performed; this
TABLE 3.1
AREAS OF AVERAGE RESIDUAL
GAMMA ACTIVITY
Shot 1 Area
Average Residual
Gamma Activity*
m¢?
r/br at H + 1 br
2,040
3,000
2,680
2,500
3,860
4,600
6,030
750
12,900
300
*See WT-915, Appendix F.
analysis, combined with the available data points, produced the pattern exhibited in
Figure 3.5.
The time of arrival of fallout at the Bikini Atoll stations was between 15 and 45 minutes
after detonation. Statements from persons accidentally exposed on downwind atolls in-
dicated an arrival time of 8 hours on Rongerik Atoll (at a distance of 126 nautical miles)
and of about 18 hours at Uterik Atoll (300 nautical miles). The data from two measure-
MASTICRL OES
oo
pt 0 OH
WO HM
Figure 3.5 Reconstructed complete fallout pattern, Shot 1, (r/hr at H + 1 hour).
ments of residual gamma versus time at nearby stations are presented in Figure 3.6.
The decay exponents estimated from these graphs are between 1.1 and 1.4 for Station
220.12, and 0.81 for Station 220.08. (Decay exponent is defined as x in the relation for
exposure rate I =1, t™*, where t is the time. )
Table 3.1 presents the data on contour areas.
From this, a rough activity-balance
wf MF Celera,