-
second,
4-
to determine the distribution of these seven gamma-
emitting radionuclides in many tissues from each of the 11 whole
tuna; and third,
to determine the presence of iron-55
(Fe>>)
in
the tissue samples from the whole tuna with the greatest gamma
radioactivity.
The six fallout radionuclides above were selected, based
upon past experience,
in the samples.
as the nuclides most likely to be present
Cerium-141
(cet,
and ce 44 also might be
expected to be present, but because of the difficulty of obtaining reliable estimates of small quantities of low-energy
Mev),
gamma-emitting nuclides by gamma-spectrum analysis,
(< 0.2
cel!
and cel44 were not included in the list of nuclides that were
determined routinely.
If the gamma spectrum had suggested the
presence of significant quantities of cerium or other radionuclides,
additional analyses would have been made.
The gamma nuclides were measured in a detector system with
four pi geometry.
The detector consisted of an eight-inch well
and a three-inch solid sodium iodide crystal.
In practice,
a
sample is placed on the three~inch solid crystal which is raised
into the three-inch well of the large crystal,
thereby com-
pletely surrounding the sample with at least 2-1/2 inches of
crystal.
The counting efficiency of this system was about ten
times greater than the efficiency of the system with.the single,