months from tide and wave action and
in summer months from ‘tides and the
North Equatorial Current. The surface
movement of waterborne radioactivity
from Bikini and Eniwetok atolls would
therefore
be
westward
toward
the
Philippine Islands, with the possibility
UNCLASSIFIED
of the most radioactive clam kidney
from Eniwetok Atoll in an anticoincidence shielded x-ray counter gave a
positive indication of ®°Ni (at a counting error of 1 S.D.), with an upper
limit of some 0.1
disintegration per
of some movement back toward the
minute per gram of dry weight. No
59Ni was detected in 1000-minute
in the Cromwell Current (73). Both
counts of soil samples obtained from
either atoll. It is probable, therefore,
that no large amounts of 5°Ni were
east in the Equatorial Countercurrent
and possibly eastward at shallow depth
Christmas Island and Penrhyn Atoll lie
in the path of the westward-moving
South Equatorial Current and consequently would be unlikely recipients
of waterborne radioactivity emanating
from Bikini and Eniwetok lagoons.
Nickel-58 comprises some 68 percent
of stable nickel, and we have consid-
ered the possibility of the production
of 5°Ni (half-life, 80,000 years) both
by (n,y) interactions with stable nickel,
(pn) reactions with stable cobalt, and
(p,a@) reactions with “*Fe (92 percent
abundance). Based on abundances,
cross sections, and decay constants, we
calculated an activity ratio of “Ni to
59Ni of approximately 600 for the (n,y)
production of **Ni. Nickel-59 decays
by electron capture and is determined
by measuring the 6.9-kev x-ray which
results from the de-excitation of its
daughter, ®°Co. A 3000-minute count
produced, and that the presence of
small amounts of 5°Ni precludes its
usefulness as a tracer in oceanic processes.
A realistic assessment of the total
®Ni present at Bikini and Eniwetok
atolls is not possible from the data
presented here, although knowledge of
such an inventory and of the rate at
which it is injected into the North
Equatorial Current would help one to
determine its usefulness as a downstream tracer for these waters. However, the giant clam Tridacna sp. ap-
pears to be an excellent indicator organism, which could be used to deline-
ate the downstream penetration of ®Ni.
THOMAS M. BEASLEY
Epwarpb E, HELp
Laboratory ef Radiation Ecology,
University of Washington, Seattle
UNCLASSIFIED
References and Notes
1. F. G. Lowman, in Disposal of Radioactive
Wastes, K. Saddington and W. L. Templeton,
Eds. (Macmillan, New York, 1959), pp.
105-138.
2. G. M. Lederer, J. M. Hollander, I. Perlman,
Table of Isotopes (Wiley, New York, ed. 6,
1967).
3. W. S. Broecker, in The Sea, M. N. Hill, Ed.
(Interscience, New York, 1963), vol. 2,
pp. 88-108.
4. E. D. Goldberg, in The Sea, M. N. Hill, Ed.
(Interscience, New York, 1962), vol. 1, pp.
3-25.
5. R. C. Voter and C, V. Banks, Anal, Chem.
21, 1320 (1949).
6. J. M. Nielsen and T. M. Beasley, in Assess-
ment of Radioactivity in Man (International
Atomic Energy Agency, Vienna, 1964), pp.
245-260.
7. G. D. Nicholls, H. Curl, Jr., V. T. Bowen,
Limnol. Oceanogr. 4, 472 (1959).
8. L. J. Kirby, The Radiochemistry of Nickel
(National
Academy
of
Sciences—National
Research Council Report No. NAS-NS 3051,
Washington, D.C., 1961).
9. T. R. Folson and D. R. Young, Nature 206,
803 (1965).
10. W. C. Hanson, D. G. Watson, R. W. Perkins,
in Radioecological Concentration Processes,
B. Aberg and F. B. Hungate, Eds. (Pergamon Press, Oxford, 1967), pp. 233-245.
11. The concentrations of 5’Co were measured
at the time of collection and are tabulated
in this laboratory.
12, W. S. von Arx, Trans. Amer. Geophys.
Union 29, 861 (1948).
13, J. A. Knaus, in The Sea, M. N. Hill, Ed. (Interscience, New York, 1963), vol. 2, pp. 235-252.
14, We thank Dr. W. Pearcy of Oregon State
University for supplying samples of chaetognaths; Dr. T. R. Folsom of Scripps Institute
of Oceanography and C. H. Fiscus of the
Marine Biological Laboratory, Bureau of
Commercial Fisheries, for supplying squid
specimens. Supported by AEC under contract
No. AT(26-1) -269.
3 March 1969