Evening star., 1947-07-30
Stars, Men and Atoms
Bosic A-Bomb Explosive
Exists Free in Nature
Plutonium Found Only in Extremely
Small Amounts in Pitchblend
By Thomas X. Henry

By Thomas X. Henry
Plutonium, the synthetic element which Il
the basic explosive material OF the atomic bomb.
exists In nature but In inconceivably minute
amounts.
1t is found, to the extent Of one part IN .
hundred trillion, in pitchblend. the mineral
from which most uranium Is extracted. 1t
never would have been found unless the pre-
else chemical properties Of the element had
been determined In the atomic bomb research.
This has just been revealed by Drs Glen L.
Seaborg and Emilio Segre OF the University
OF California, discoverers Of the new synthetic
elements heavier than uranium, americum and
curium
Plutonium must be manufactured In one Of
the great uranium piles such as those st Oak
Ridge. Tenn, and Hanford, Wash. But its
existence in nature however minute the guam
tity. establishes the fact that the earth itself
acts as 'pile" on a small scale. wherever
atoms of the rare isotope of uranium U-3s5,
exist, one of them is exploded now and then.
One of the results is to transform some of the
ordinary uranium into plutonium.
Element Wouldn't Exist Otherwise.
Otherwise the extremely short life Of TIE
element would have made it impossible for
any to have remained in the earth. Whatever
the amount in the original material Of the
planet torn loose from the sun, 1t would have
disintegrated completely in a few weeks.
The two University of California chemists
also reveal the existence of an isotope Of
neptunum the synthetic element which is q
transition stage from uranium to plutonium,
which has half life Of more than two million
years instead of a few seconds, as is the
case with the greater part Of the element
manufactured. The term half life" means
that one-half of any definite amount will dis
appear in two million years. Then half Of
what is left will disappear in the next two
million years, and so on.
This isotope is of great value, the discov-
erers say because it is produced In measurable
amounts in the uranium piles and makes pos
sible comprehensive chemical study Of nep-
tunium. 1t appears to be closely allied to the
so-called rare earth" elements-as do also
americum and curium.
New Form Of Americum Found.
They have also found a form Of the new
synthetic element americum which has half
life Of 500 years, compared to one month for
the more plentiful form. Like the first dis
covered. it is an emitter Of alpha particles
essentially the nuclei of helium atoms. Both
the new elements are produced by lombard.
ing plutoniurn with whole helium atoms.
1t Is highly unlikely, the Investigators say
in report just issued, that either americ,nn
or curium exists in nature. Unlike the parent
plutonium, they are entirely the results Of
synthesis which can take place only In ths
laboratory. 1t Is possible, however, that tbs
earth might contain small amounts OF the
long-lived neptunium
At present the two new transuranic sle-
ments are purely Of scientific interest. They
do not, so far as known, fit into any program
Of atomic bomb or energy development. Pre-
else determination Of their properties, however.
may lead to some Use Of minute quantities Of
them