30-
later, contained the lowest levels of gamma radioactivity.
levels
in the plankton from
this location
western perimeter of the contaminated
only a few miles away.
The low
indicated that the
south-
water mass at this time was
The low level of radioactivity also suggests
that the radioactive water had travelled primarily ina westward
rather than a southwestward direction.
The radioisotopic composition of the plankton samples
collected
before and after the Wahoo detonation is givenin Table 3.
was
the
major
contributor in all of the samples, but
amounts of Mo99-Tc99M, Te132-1132
the
and U23? differed,
Np239
relative
Mo99-
Tc?9M was much higher and Te132-1132 was much lower in the preWahoo sample.
Ru!05-Rh105 was detected in one post-Wahoo sample
and Rul06-Rn106
was detected
in one pre- Wahoo sample.
These differences in radioisotopic
content
may be
used
tablish the origin of the radioactive material in the samples
during the survey.
to es-
collected
As seenin Table 3, the radioisotopes in samples
P-25 and P-26, collected at the western periphery,
were similar to
the radioisotopes in earlier samples; therefore, it was assumed that
the origin of the radioactive material was
the
same
for all samples
collected after the Wahoo detonation.
Results of radiochemical separations and gamma spectrum analyse
revealed that the percentages of Bal40-Lal40 and U237 were higher i