Uranium
The Element
Uranium (symbol U) is the heaviest naturally occurring element.
Pure uranium consists of 99.3% of the isotope U-238, 0.7% of
the fissile isotope U-235, and a trace of U-234 formed by radioactive decay
of U-238.
Occurence
Uranium is found as an oxide or complex salt in minerals
such as pitchblende and carnotite. It has an average concentration
in the earth's crust of about 2 parts per million (ppm). The ore at Roxby
Downs has a concentration of about 500 ppm.
Radioactivity
Uranium is radioactive and emits hazardous ionizing radiation
Uranium often occurs with radioactive isotopes of other
elements such as radon (a dense gas), radium and polonium. The isotopes
are related to uranium through a series of radioactive decays.
Toxicity
Like many other "heavy metals" such as lead and cadmium,
uranium is toxic.
Combustion
Because it rapidly oxidizes, uranium is pyrophoric, that
is it can rapidly self combust. The product of this combustion is finely
divided oxides of uranium which can be readily inhaled or ingested.
Uranium tipped shells and rockets used in the Gulf war,
in the Balkan conflict, and in Afghanistan appear to be causing health
problems related to the radioactivity and toxicity of uranium.
Nuclear Fission
U-235 is said to be 'fissile' because it can undergo a nuclear
reaction called 'nuclear fission'. During nuclear fission the nucleus is fissioned, or split,
into smaller particles. This process releases large amounts of energy and
is the basis of nuclear weapons and nuclear power stations.
Uses
Uranium is mined for several purposes. The most common uses
of uranium are in nuclear weapons and
in nuclear power stations. It has been
used to produce nuclear weapons for more than 50 years and electricity
for more than 40 years.
Greater technical detail can be found on the NIC website or by searching through
the publications at the Conservation Council of South Australia.
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© 2002 Conservation Council of SA.
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