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Nuclear Reactors
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is a device for producing nuclear energy by controlled nuclear
reactions. It can be used for either research of power production.
The reactor is so constructed that the fission of atomic nuclei
produces a self-sustaining nuclear chain reaction, in which
the produced neutrons are able to split other nuclei. A fission
reactor consists basically of:
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[
1 ] a fuel, usually uranium or plutonium, enclosed in
shielding;
[ 2 ] a moderator-a substance such as graphite, beryllium,
light (or ordinary) water, or heavy water that slows
down the neutrons so that they may be more easily captured
by the fissionable atoms; and
[ 4 ] a cooling system that extracts the heat energy
produced. |
The fuel is sometimes enriched-i.e., its concentration of
fissionable isotopes is artificially increased-to increase
the frequency of neutron capture. Light-water reactors are
the most common power-generating reactors. They use enriched
uranium and produce steam to drive turbines. The breeder reactor
is a special type of reactor that produces more fissionable
atoms than it consumes by using surplus neutrons to transmute
certain fissionable atoms into fissionable atoms.
The design of fusion reactors is still in an experimental
stage because of the problems involved in containing the PLASMA
fuel and attaining the high temperatures needed to initiate
the reaction. The best fusion results have been obtained deuterium-tritium
fuel in a tokamak reactor, which uses a powerful magnetic
field to confine the plasma in a doughnut-shaped chamber.
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U.S. Nuclear Reactors
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