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A great number of radioisotopes have been added
to the oceans from the detonation of nuclear devices
especially in the vicinity of Bikini and Eniwetok Atolis.
The kinds of radioisotopes produced are determined largely
by the type of detonation -- fission or fusion.
Previous
to 1952 nuclear detonations were exclusively of the fission
type but since then there also have been detonations of the
fusion and the fission-fusion-fission type.
The greatest
number of radioisotopes is produced by the detonation of a
fission type device.
In the fission process the nuclei ot atoms of
ue>5 or Pu239 are split when struck by neutrons.
In
addition to the release of energy at the time of fission,
the two parts of the original atom become isotopes of two
new elements that are approximately one-half the weight
of the original atom.
The nuclei of the newly-formed
isotopes are unstable usually because of an excess of
neutrons, hence are radioactive.
(Because the neutron-
proton ratio in the nucleus of stable lignt elements is
less than in heavy elements and,
nearly all of the newly-
formed isotopes retain the neutron-proton ratio of the
original atom (U°55 or Pu239), there is generally an excess of neutrons in the nuclei of the newly-formed isotopes)