1.8 mr/be and at 45 meters it was 15.0 mr/hr.
The radioactivity of the water in the deepest
layer is lost by decay and by the mixing of this layer with the less radioactive water above.
During the Project 2.64 aircraft fallout survey, an area of radioactivity was found in the
ocean near Site William.
through the passes.
This in all probability came from the radioactive water draining
The ocean currents transported the contaminated water westward.
An
attempt was made to obtain permission for the LCU to explore the radioactive water mass outside the lagoon. This request was denied, because regulations prohibited operation of LCU’s
in the open ocean. Hence, the activity in this mass will remain unknown.
3.6.3 Shot Flathead. The fallout: pattern included two thirds of the lagoon. Only the southeasternthird was free of contamination (Figure 3.2). The fallout was graded from light contami
nation along its southern edge to heavy contamination in the northern area. A line of lightcolored water, formed from the mixing of powdered coral, marked the boundary of the mostintensely radioactive water.
This water registered 3 r/hr, when observed 6.5 hours after the
ghot; and its boundary was very sharp in both color change and contamination.
The distance
between 3.0 and 0.23 r/hr water was not more than 50 yards.
The edge of discoloration in the water began off the middle of Site Fox and extended clock-
wise in an arc to about a mile south of the shot site, then straight towards 240 degrees, beyond
which no observations were made the first day.
By Fiathead plus one day, the water that measured more than 150 mr/hr was located in the
northwest corner of the lagoon. The center appeared to be about 2 miles south of Site Charlie.
At the shot site, the water measured 30 mr/hr at the surface, with a gradual increase to 112
mr/he at 18 meters.
The large decrease in radioactivity at ground zero from the day of the shot to Flathead plus
one can be accounted for through the processes of decay, the settling of the floured coral to the
bottom, and the transport to the west end of the lagoon by currents. The transport of radioactive
water from the vicinity of surface zero to the zone of high activity in the western end of the lagoon on D+1 is very possible, consideringthe length of time and average velocity of the curreat.
On D+2, a series of current-stations and probe measurements were made from the shot site
towards 255 degrees. The currents on the surface were ina direction of 260 degrees. The
currents in the lower layers were from a half to two thirds of the velocity of the surface currents
and, generally, in a direction between 150 and 260 degrees. The probe measured a maximum of
more than 150 mr/hr in the lower layers.
Due to the failure of the probe on D+3, the next observations were on D+7. By this time, a
pattern was well developed. There was a trough of radioactive water along an axis of 070 degrees. The high radioactivity was located about 3 miles south of Site Charlie. It was 1.9 mr/hr
on the surface and 4.5 mr/hr in the lower layer. Five miles due south of Site George, the surface was 1.0 mr/hr, and in the lower level it was 1.5 mr/hr (Figure 3.3).
This figure illustrates
the current in the lower layer transporting radioactive water toward the southeast and the radioactive water on the surface being moved toward the westward by the upper-layer current.
By D+11, the pattern of D+7 still held for the surface level (Figure 3.4). The cell of highest
radioactive water still existed south of Site Charlie, feeding the lower levels of the lagoon as the
current moved the water eastward. By this time the observed 1.0- mr/hr line had moved 2 miles
@ast southeast. The 0.4-mr/hr contour line had been over 5 miles from Site How, whereas on
Dili, it was 1.5 miles from How.
The pattern of radioactive water represents the current pattern of the lower layer. There.
appears to be a cellular system rotating counterclockwise in the area of highest radioactivity
inthe water. The current data gives evidence to its existence, and the pattern of radioactive
water tends to support this idea. Coming from this cell on its east side were currents toward
the East Southeast that continue feeding radioactive water into the East Southeast flow. As the
water flowed in that direction, it was mixed with the upper layer by the wind, and some upwelling may have occurred before the lower layer reached the eastern edge of the lagoon. The
leading edge of the lower water was continually being eroded away by nonradioactive water with
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