Glossary of Nuclear Terms
- Atom: The basic building block of all
matter. The smallest particle of an
element that has the same properties
as the element. It consists of a
central core called the nucleus that is
made up of protons and neutrons.
Electrons revolve in orbits in the
region surrounding the nucleus.
- Dry-cask storage: A method for
storing spent fuel. Dry casks are
large, rugged containers made of
steel or steel-reinforced concrete, 18
or more inches thick. The casks use
materials like steel, concrete and
lead - instead of water - as a
radiation shield. Depending on the
design, a dry cask can hold from
seven to 56 12-foot-long fuel
- Fission: The splitting of atoms that
results in the release of large
amounts of energy. Two or three
neutrons are usually released during
this event. Fission occurs either
naturally or when an atom's nucleus
is bombarded by neutrons.
- Fossil fuel: Carbon based fuel
resulting from millions of years of
biological decay. Coal, oil, and
natural gas are the most common
- Fuel assembly: Assemblies of fuel
rods that are placed in the reactor
vessel to form the core. Each fuel
assembly may contain from
approximately 60 to 300 fuel rods.
- Fuel pellets: The Uranium fuel for
nuclear reactors in the form of
ceramic cylinders about one-half of
an inch long and three-eighths of an
inch in diameter. These "pellets" are
stacked in long tubes to form fuel
- Fuel rod: A long, slender tube that
holds the fuel pellets; fuel rods are
assembled into bundles called fuel
elements or fuel assemblies that are
loaded individually into the reactor
- NRC: Nuclear Regulatory
Commission, a U.S. agency
chartered to develop and administer
rules for regulating commercial
nuclear applications (including
nuclear power plants, medical and
- Nuclear energy: Energy, usually in
the form of heat or electricity,
produced by the process of nuclear
fission within a nuclear reactor. The
coolant that removes the heat from
the nuclear reactor is normally used
to boil water, and the resultant steam
drives steam turbines that rotate
- Pressurized water reactor (pwr):
A reactor designed in which water
flowing through the reactor is heated
by nuclear energy but is kept at high
pressure to keep the water from
boiling. This heated water then
transfers its heat to a secondary
water system that boils into steam to
drive the turbine.
- Pressurizer: A device to keep water
in the primary system within pressure
limits needed to operate the reactor.
- Radioactivity: The spontaneous
transformation of an unstable atom
and often results in the emission of
radiation. This process is referred to
as a transformation, a decay, or a
disintegration of an atom.
- Radiation: Particles (alpha, beta,
neutrons) or rays (gamma) emitted
from the nucleus of an unstable
radioactive atom as a result of
- Radon: A naturally occurring
radioactive gas formed when the
element radium decays.
- Reactor vessel: A device in which
nuclear fission may be sustained and
controlled in a self-supporting nuclear
reaction. It houses the core (made up
of fuel rods, control rods, and
instruments contained within a
reactor vessel) of most types of
- Spent fuel: Fuel rods which no
longer have enough fissionable
uranium in them to be efficiently used
to produce power.
- Steam generator: The heat
exchanger used in some reactor
designs to transfer heat from the
primary reactor coolant system to the
secondary (steam system).
- Uranium: A naturally radioactive and
very dense element. Mine Uranium
contains 0.7 percent of the isotope
Uranium-235, needed for fission.
Uranium-235 is the principal nuclear
fuel material used in today's nuclear
- "Watch list": Twice a year the
United States Nuclear Regulatory
Commission (NRC) evaluates the
performance of the operating nuclear
power plants in the United States
and identifies those which require
additional regulatory oversight
because of declining performance.
Those plants are placed on a list
commonly called the "watch list".
Once placed on the "watch list" a
plant must demonstrate consistent
improved performance before it is
removed from the list.
Edelson, Edward. The Journalist's
Guide to Nuclear Energy. 4th ed.,
Nuclear Energy Institute, 1994.
Florida Power & Light Nuclear
Notebook. Florida Power & Light
Emergency Public Communications
Manual. lim. ed., Institute of Nuclear
Power Operations December, 1993.
Waltar, Alan E., Ph.D. America the
Powerless: Facing our Nuclear
Energy Dilemma. Madison,
Wisconsin: Cogito Books, 1995.