5
of 237 Np (ca. 1.8 x 1072, 237 N/a 2381) have been reported in pitchblende by
Peppard and co-workers (195}).
Amecicium-241 was first fsolated from an
trradiated plutonium sample by Seaborg et a}. in late 1944 (1949).
Although
the half-lives of c44o 247 Cm or other unidentified super heavy elements may
be long enough to provide for their ({sotopic) persistence since primordial
times, none have yet been measured quantitatively (Keller, op.cit).
The formation of transuranium isotopes with proton or mass numbers different from those of their parent occurs primarily by nucleon capture of neutrons,
deutrons and alpha particles supplied from particle accelerators or pulsed
fission or fuston reactions.
In the process of operating a uranium-fueled
reactor, for example, isotopes of neptunium, plutonium, americium and curium
are formed and can be subsequently separated from the depleted uranium fuels.
The production of transuranium elements is accomplished by successive neutron
capture reactions from products created from 238, or 239 Pu in nuclear detonations or in reactors.
Isotopes with mass numbers as hich as 257 have been
found or identified from both laboratory and thermonuclear tests (Keller, op.
cit.).
The mass yield of heavy isotopes from the Mike and the Barbe) and
Cyclamen thermonuclear experiments decreased in atom amounts approximately
logarithmically with increasing isobars from mass numbers of 239 and 242,
respectively (Ofiamond et al.,1960; Keller, op.cit.).
The major alpha-emitting radioisotopes of uranium, neptunium, plutonium
and americium which are produced from the detonation of plutonium or uranium
nuclear devices, and their mode of production as found in Lederer et at. (1967)
and keller (ap.cit.), is shown in Fig. 1.
From this diagram it is apparent
that relating the abundance of transurantum isotopes in environmental samples
to their origin from a specific radionuclide parent may be extremely difficult.
This ts particularly true with respect to 23854, which can be produced by at