which it was in contact. In addition, mixing with the nonradioactive water above reduced the
activity of the lower layer.
3.6.4 Shot Dakota. The boundary of the fallout pattern was extremely sharp (Figure 3.5),
No probe measurements were made in the area of more than 150 mr/hr. Deck readings just
inside the boundary measured up to 700 mr/hr. The edge of fallout was marked by the lightcolored water, as appeared following Shot Flathead. Some 200 feet outside the light-colored
water, the radioactivity of the water measured less than 1 mr/hr along part of the boundary,
In the western end of the lagoon, the fallout became graded, and the transition from clean water
to the 150-mr/hr contour covered much more distance.
3.6.5 Discussion of Presented Dose-Rate Values. No attempt has been made to construct
iso-dose-rate contours as they would have resulted from fallout on an infinite level plane. In
the lagoon there is the complication of shallowness. By the time most measurements could be
taken, the radioactivity would have reached the bottom of the lagoon. There is no way to tell
what percentage of the radioactive particles would have settled on the bottom. Also, there is
the problem of the upper layer currents transporting the radioactive water westward while the
lower layer is being transported eastward. Near the edges of the lagoon, there is much mixing
with fresh water from the ocean, which would cause the upper layer to measure less radioactiy.
ity that the lower layer.
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