but at times requiring speeds two to five times the known ocean surface currents in the area.
gives further indirect evidence for such sources (Section 3.3.2). A comparison of the std-GITR
and the UW-GITR records from Stations DR 4.5, CR 4.1, and CR 5.2 for Wahoo and DRR 3.9
for Umbrella reveals several instances at later times where the std-GITR shows a spike in dose
rate, which is either not recorded or recorded at a much lower intensity by the UW-GITR; such
differences could be the result of radioactive foam.
Finally, a careful inspection of photographs taken at an altitude of 24,000 feet over Wahoo
surface zero shows a white border, which is probably foam, persisting along the downwind edge
of the white water area aS late as 24 minutes after zero time. After about 13 minutes, the white
water area becomes indistinct, being distinguished only by the foam border along the downwind
edge and by a discontinuity in the surface roughness of the ocean observable along the other
edges.
Photographic evidence indicates that the spread of the white water itself is probably not a
toroidal circulation as suggested in Reference 102 but rather an overlayering of the surface
water by the violent upwelling of contaminated waters near the surface zero. This water, which
is white in appearance probably due to included bubbles (and bottom material in the case of Umbreila}, spreads out radially along the surface to a distance of about 3,500 feet at velocities not
less than 10 knots. Evidence for overlayering is found by inspection of the white water boundaries presented with the isodose contours in Section 3.3.3, which reveal an indentation on their
outer perimeter associated with each of the closer target ships. These indentations are located
radially beyond the ships and are particularly pronounced for Wahoo. It seems more probable
that they would have been caused by surface interference with the suggested radial overlayering
phenomenon rather than by the interruption of a toroidal circulation extending to greater depths.
Additional evidence of radioactive surface water is provided by the 0- to 6-hour records of
both the standard and the underwater GITR’s (Figures 3.154 through 3.182).
When considering
these figures, it should be remembered that many of the coracles on Wahoo were drifting; their
estimated positions at later times are indicated in Figure 2.1. Recovery, when it occurred
during the record, is also indicated. The observed times of arrival and cessation for white
water are presented in Table 3.24.
.
Times of cessation are particularly difficult to read from the gamma record and in many
instances are little better than guesses. For Wahoo, the TOA have been plotted as a function
of distance (Figure 3.139). Although the points show some Scatter, a Straight line witna slope-
ef approximately 1 knot may be faired through them. The fact that these later events occur at
times and in directions that are compatible with known ocean surface currents in the region
further supports the assumption that they are indeed due to the movement of water directly
contaminated by the nuclear device. The reported dose rates may be converted to fission product concentrations as indicated in Section C.6.
Assuming a speed of 1 knot, the path lengths through the white water have been computed for
the Wahoo stations and are also included in Table 3.24. These path lengths are usually shorter
than the last observed white water diameter (about 10,000 feet at 24 minutes), probably because
corrections for drift can only be approximate. They suggest, however, that this body of radio-
active water does not greatly increase its boundaries after about 24 minutes.
The 0- to 6-hour records for Umbrella do not show much evidence of radioactive water at
later times. Since all deep-moored stations were recovered before any white water could have
crossed the reef and reached their positions, these stations are omitted from the analysis of
white water movement. Consequentiy, not all the 0- to 6-hour records for Umbrella have been
reproduced. The more distant stations within the lagoon indicate white water arrival at a time
compatible with an assumed radiai expansion of 0.5 knot {rom the photographically established
23~mimute white water boundary (Section 3.3.2). An assumed movementin the direction of the
surface wind at a speed of 1 knot also fits the water data nearly as well. Movement of lagoon
waters by the wind at comparable speeds has been reported for Bikini (Reference 94). A plot
of the Umbrella TOA for water is scattered; however, a line with a slope of approximately 2
knots may be faired through the points (Figure 3.140).
248
This line is presumed to represent the
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