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Summary
1.
During July 1957, chemical separations by ton-exchange
resin columns were made on five grouped plankton samples taken
in and west of the Eniwetok Proving Ground
in September 1956.
Also, radiochemical separations for Sr99-y90 were made.
The
radioactive isotopes in the separated fractions were identi-
fied by decay rates, maximum beta energies and gamma energies.
2.
The distribution pattern of Co°7 and Zn®5
simples
not subjected to
in plankton
ion-exchange separation was deter-
mined by analysis of gamma spectrum curves.
3.
The predominant fission product radioisotopes found were
Zr95-Nb22, Cett4-prl44 ana in one sample, Rul06-Rp106,
Fission products accounted for 22 to 44 per cent of the total
radioactivity at the collection date.
in the
Sr99-y90 was not found
lon-exchange separations nor in fuming nitric acid pre-
cipitations made on duplicate aliquots.
4.
[DOE ARCHIVES
The non-fission radioisotopes Fe55, Co57, Co58, ana zn®5
contributed 55 to 77 per cent of the total radioactivity, and
Co? ana Mn>4 accounted for a total of 0.8 to 1.6 per cent.
5.
Cod? and Co©° were present at Bikini Atoll in a 1:1 ratio
and at
Eniwetok ina
5.3:1 ratio.
These
ratios
were re-
flected in plankton samples collected in the vicinity of the
two atolls.
The ratio of Co57/¢060 in an area 300 miles wide
north to south and 200 to 500 miles west of Eniwetok was
30