Enriched uranium
Enriched uranium is a kind of uranium in
which the percent composition of urani-
um-235 has been increased through the pro-
cess of isotope separation. Natural uranium
(or NU) is 99.284% 238U isotope, with 235U
only constituting about 0.711% of its weight.
235U is the only isotope existing in nature (in
any appreciable amount) that is fissionable
by thermal neutrons.
Enriched uranium is a critical component
for both civil nuclear power generation and
military nuclear weapons. The International
Atomic Energy Agency attempts to monitor
and control enriched uranium supplies and
processes in its efforts to ensure nuclear
power generation safety and curb nuclear
weapons proliferation.
During the Manhattan Project enriched
uranium was given the codename oralloy, a
shortened version of Oak Ridge alloy, after
the location of the plants where the uranium
was enriched. The term oralloy is still occa-
sionally used to refer to enriched uranium.
There are about 2,000 tonnes (t, Mg) of
highly enriched uranium in the world,[1] pro-
duced mostly for nuclear weapons, naval
propulsion, and smaller quantities for re-
search reactors.
The 238U remaining after enrichment is
known as depleted uranium (DU), and is con-
siderably less radioactive than even natural
uranium, though still extremely dense. It is
useful for armour- penetrating weapons, and
other applications requiring very dense
metals, though at the present time, only 5%
of it is put to any use; the rest remains in
storage at the enrichment facilities.
Grades
Slightly-enriched uranium (SEU)
Slightly-enriched uranium (SEU) has a 235U
concentration of 0.9% to 2%.
This new grade is being used to replace
natural uranium (NU) fuel in some heavy wa-
ter reactors like the CANDU. Costs are
lowered because less uranium and fewer
bundles are needed to fuel the reactor. This
in turn reduces the quantity of used fuel and
its subsequent waste management costs.
Reprocessed uranium (RU)
Reprocessed uranium (RU) is a variation of
SEU. It is based on a fuel cycle involving