Environmental Engineering Reference
In-Depth Information
Nuclear Fuel
There are two primary forms of fuel used in nuclear power plants: uranium and plutonium.
Uranium
Uranium has an atomic number of 92 and its chemical symbol is U. It has between 141 and 146 neutrons,
meaning there are six isotopes, the most common being U-238 (146 neutrons), which makes up 99.284 percent
of the uranium found in nature. U-235 (143 neutrons) and U-234 (142 neutrons) also occur naturally, at 0.711
percent and 0.0058 percent of natural reserves, respectively. All six forms of uranium are at least weakly radio-
active, meaning that they shed particles. Uranium is commercially extracted from uranium-containing minerals
such as uraninite. Uranium decays slowly by emitting an alpha particle.
U-235 is the only naturally occurring isotope capable of nuclear fission. Only 3 percent of U-235 is used in
power plants to generate electricity, while 85 percent is used for weapons. Power plants convert U-238, which
is not fissile, into plutonium-239 (Pu-239), which is fissile.
Plutonium
Plutonium, whose chemical symbol is Pu, is the heaviest naturally occurring element and has an atomic num-
ber of 94. As fission occurs in a nuclear reactor, Uranium (U-238) is said to be
fertile
and is able to capture one
of the free neutrons flying around in the core of the reactor. This indirectly becomes plutonium (Pu-239). It is
estimated that one-third of nuclear energy produced comes from his process, known as burning Pu-239.
International inspectors regularly inspect nuclear power plants to limit the production of Pu-239 and other ra-
dioactive isotopes that could be used to build nuclear weapons. One of the greatest fears is that if Iran and
North Korea develop nuclear power plants (see an example in the following figure), they will not participate in
these inspections and, thus, could build a supply of Pu-239 to be used in nuclear weapons.
Nuclear Reactors
