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TRANSURANIUM ELEMENTS IN SAMPLES COLLECTED NEAR BIKINI ATOLL
Table |. Sampling data on manne sediment sumples
Sample
Patitude
Cangitude
73104
TA1O8
FAH)
VV
1341.6"
1156.07
Poe
1149.0"
beax44 Y
Loa*-44 4°
LAA
LO4° 2) a
Wailer depth
{mn}
Topography of sea bottom
XXX
1420
1600
etd)
then dissolved with hydrochloric acid and the
coprecipitation was repealed by adding a
sodium hydroxide solution. Afler removing
iron by the solvent extraction with di-isobutylketone, plutontum was extracted with
lO% (viv) tri-n-octylamine (TOA) xylene
solution from 8M nitric acid solution. The
organic phase was washed successively with
8m nitric acid lo remove the uranium, and
with [Om hydrochloric acid to remove the
thorium. Plutonium was stripped with 6M
hydrochlori¢ acid containing 0.2 M hydrofluaric
acid (Sa7 1).
The aqueous phase of the TOA extraction,
containing anericium and gadolinium, was
evaporated to dryness. The americium was
then extracted, together with “Gd, into 50%
(viv)
di(2-ethylhexyl)
phosphoric
acid
(HDEHP) toluene solution from the hydrochloric acid solution adjusted to pH 1.2, and
stripped with 8M hydrochloric acid.
For alpha spectrometry, americtum and plutaniumfractions were subjected, respectively,
to electrodeposition on 18-8 stainless steel
disks having diameters of 2.7 cm. The eleetrolytic solution containing 0.5 ml of O.1M
hydrochloric acid, 0.5 mi of 0.5 M oxalic acid,
O.75 ml of 2M ammonium formate, 5 ml of
sodium chloride and 3 ml of distted water. The
eleclrodeposition was carried out for 2hr at
SO) mA, using a platinum wire as an anode.
Americium and plutonium were determined
by alpha-spectrometry using a Si(Au) surface
barrier detector and a 200-channel pulse
height analyzer.
The top of Guyot
The top of Guyot
The shoulder of Guy ot
Oocan faar
Characteristics
af sample
Globiyerina sand
Globigenina sand
Globigerina sand
Red cley
RESULTS AND DISCUSSION
The
alpha-spectra
of
plutonium
and
amiericiumfractions of all samples are shown
in Figs. 4a and b, respectively. In the alphaspectra of the americium fraction of the
sample 73113, the contamination with *7Ac,
the daughter nuclide of **U, is shown by the
existance of the alpha-emitting daughter
nuclides of *7Ac. Since actinium in a 3+
oxidation state is the most stable in an
aqueous solution and the chemical properties
of actinium resemble americium and lanthanides, actinium may behave as similarly as
americium and lanthanide in the present
analytical procedure for americium. As the
energies of alpha rays from the daughters of
7Ac are higher than that from “Am, the
peaks due to these nuclides did not interfere
with the determination of “'Am in samples
which had no high *’Ac content.
The contents of ??°"’Pu and *“'Am are
shown in Table 2 and Fig. 3, The overall
chemical yields of ’*Pu and '"Gd varied from
12 to 42%. The “'Am in the “Bikini Ash"
sample was found to be 12.9 + 0.9 dis/min/mg.
The “'Am/??'**°pu
ratios
for the
‘Bikint
Ash" sample and the sediment samples were
found to be nearly the same, within the statistical counting error of the samples.
239 MOTD
There are a few reports on the
contamination of deep sea sediments due to
the worldwide fallout. Noshkin and Bowen
analyzed six sediment profiles collected from
the Atlantic Ocean and the Medilerrancan
Sea tn 1969~ 1971 (No73). Among. these
samples three had been collected im the
northern
hemisphere.
The
contents
of
Concurrent with these analyses, the intercalibration sample, plutontum standard soll
No. 3, prepared by the US Energy Research
2)in ocean floor sediment samples,
Service Laboratory in Idaho was also
analyzed by the above-mentioned method,
bulk sediment, respectively. Livingston ef al,
and
Development
Administrations
Health
The validity of our calibration of Pu tracer
was confiemed by the agreement of our data
with those from the Health Service LaboraLory.
collected from about 1000 and $000 m depths,
were around 0.02 and 0.005 dis/minfem’ of
reported the value of 0.16dis/min/g for the
top-of-core samples collected from the 1000-
m depth in the Atlantic Ocean in 1972 (L175).
The present values for samples 73108 and
ope
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