AO1LORS
Health Physics Vol. 35 (Aug), pp. 301-307
Pergamon Press Ltd., 1978.
© Health Physics Society
0017-9078/7 8/080 | 0.30 1/$02 00/0
Printed in Great Britain
DETERMINATION OF TRANSURANIUM
ELEMENTS IN A SO-CALLED
“BIKINI ASH” SAMPLE AND IN
MARINE SEDIMENT SAMPLES
COLLECTED NEAR BIKINI ATOLL
SHUN'ICHI HISAMATSU
School of Medicine, Akita University, Hondo {-I-[ Akita 010
and
:
MASANOBU SAKANOQUE
Faculty of Science, Kanazawa University, Marunouchi I-1, Kanazawa 920, Japan
(Received 3 May 1977, accepted 9 December 1977)
Abstract—The concentrations of ”?**’Pu and *'Am in the debris from the second
thermonuclear test detonation of the USA (Bravo) were determined. This debris, called
“Bikini Ash”, was collected in 1954 on the deck of the Japanese fisherboat ‘Sth
Fukuryu-Maru” which was located some 150 km to the east of Bikini Atoll at the time of
the thermonuclear test. A portion of the 1954 sample was subjected to analytical analysis
in 1974. Accordingly, the concentrations of 7"**’Pu and “‘Am in the sample were
determined to be 25.9+ 1.7 and 12.9+ 0.9 dis/min/mg, respectively. From these values, the
ratio of “'Pu/?**?Pu at time zero was calculated to be 26+ 3, andthis ratio was almost
the same as the ‘‘Mike’ thermonuclear debris. Furthermore, **°?“Pu and ™'Am contents
of the marine sediment samples collected near Bikini Atoll were also analyzed, and it was
found that a significant contamination with these nuclides was found to be still remaining
in this area.
test of the USA was carried out at Bikini
Atoll (Bravo). The Japanese fisherboat ‘‘Sth
Fukuryu-Maru”’ was exposed to the nuclear
debris from this test. The highly radioactive
debris collected on the boat, called “Bikini
Ash” in Japan, has become an urgent subject
of many investigators (JA54). It was found
that this debris was coral reef having a
composition of CaO 55.2%, MgO 7.0% and
CO, 11.8% and contaminated with a large
amount of fission products and induced
radioactive
nucludes,
such
as
21),
The
“Bikini Ash" has been subjected to only a
few studies on transuranium elements, although the presence of Pu was supposed
from one track on nuclear emulsion exposed
for many days to a radiochemically separated
fraction. In this present study, the objective
301
was to determine the 7°'"Pu and “Am
contents of both the “Bikini Ash” sample and
several marine sediment samples collected
near Bikini Atoll, as accurately as possible by
radiochemical techniques. Just recently, the
59.6keV
gamma
ray
from
™“'Am
in
the
“Bikini Ash” has been detected by gamma ray
spectrometry with a Ge(Li) detector (OK74).
These transuranium elements in the debris
might be produced, as shown in Fig. la,
by the rapid, successive neutron cap-
ture of ?*U exposed to the unusually high
neutron flux generated by the thermonuclear
explosion and the following beta-decays. [n
Fig. la, the nuclear reaction sequences for
the production of heavy nuclides in a reactor
are also shown by the broken line. The
radiochemical studies (Di60) made soon after
the
first
thermonuclear
explosion
test
(“Mike™) revealed the relative abundance and
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INTRODUCTION
ON | Marcu 1954, the second thermonuclear