12
di
2415, 2394240, activity ratio was 11,7 and the 24155, 239py ratio was
21.0 + 1.1 (No 75).
Recent values of the
2415, 239
Pu ratio in soil
samples from Bikini and Eneu Islands and in Bikini island vegetation
averaged 22.0 + 3.3 (Mo 76) as of 1 January 1975.
Bikini and Eneu Islands and
the sedimentary environment from which the coral was obtained were
contaminated principally with radioactive debris from the 1954 Bravo
event.
The good agreement between the ratios determined in the
terrestrial and marine samples indicates a lack of discrimination
between
241
Pu and
239
Pu isotopes in processes in these environments,
No other americium isotopes were detected In
the aquatic environment of either Enewetak or Bikini.
Curium
.
242
No strenuous effort has been made to obtain an inventory of
Cm
Correcting the 241pu
in the November 1972 coral growth section for decay to 1 January 1975
yields a 244 5y 239py ratio of 18,9 + 1.1.
location in the lagoon.
or
244
“'"Cm in Enewetak by alpha spectrometry,
.
Curdum activities were
separated and measured in several lagoon water samples; P82 on activities
were less
than 0.2
(Ci/l.
No
42a or
244 was detected
in
sediment
samples from the Bravo Crater at Bikinl Atoll (Be76).
Higher Transuranics
No information is available to this authors knowledge on either
Berkelium or Californium in marine sarples from Enewetak or Bikini.
Bikini and Enewetak have very different isotopic ratios and therefore
different inventories of plutonium isotopes.
The amount of 2415, in the
environment regulates the projected inventory of 241 am through growth
and beta decay of the parent radionuclide.
The amount of 24d that
will be generated at Bikini from 24ley decay will exceed the amount
The distributions of
2394240),
and 240 activities measured in
December 1972 and expressed as mC4 [ler in the 2.5-cm-thick surface layer
of sediment from the lagoon floor are shown in Tigs. 2 and 3.
produced by this source at Enewetak.
Isolines
were constructed to distinguish regions of the lapoon having similar
Americium
The distribution of 2Als, is also widespread in the aquatic
environment of the Atoll.
Although the highest concentrations of
plutonium and americium are in the same areas of the lagoon at Enewetak,
the two transuranics are distributed differently.
The 241, 23942405,
ratio in sediments collected during 1972 from the lagoon ranged from
0.06 to 0.93,
TRANSURANICS IN THE BENTHIC ENVIRONMFNT OF ENLWETAK ATOLL
Surface Sediment Distributions and Inventories
Significant errors therefore can be introduced if one
transuranic is used to predict the levels of others at any given
concentrations.
The mean transuranic inventory in the surface layer and
the range of concentrations within the defined areas are shown in the
two figures.
with similar
Figs. 4 and 5 show regions of the surface sediment layer
238, 2394240, and 241ea OP2 AG
Pu ratios.
The transuranic concentrations in the surface layer sediments were
determined in over 150 ball-milled surface samples of known thickness
and in 20 core samples obtained throughout the lagoon.
we
The lagoon was