Electricity is a very important part of our lives. Electricity lights and heats our homes, refrigerates our food, and powers our factories, hospitals, schools and businesses. In solving the energy crisis now facing our nation, electricity, particularly electricity from nuclear power plants, will play an increasingly important role. This glossary defines some of the commonly used nuclear terms that you will need to discuss and understand the generation of electricity from nuclear power.

Alpha Particle

A positively charged particle emitted by certain radioactive materials. Alpha particles can be stopped by a sheet of paper.


The basic component of all matter; the smallest part of an element that has all the chemical properties of that element. Atoms in turn are made up of protons, neutrons and electrons.

Background Radiation

The radioactivity in the environment including cosmic rays from space and radiation that exists everywhere-in the air, in the earth, and in man-made materials that surround us. In the United States most people receive about 300 millirems of background radiation per year.

Beta Particle

A negatively charged particle emitted from an atom during radioactive decay. A beta particle is an electron that has a mass equal to 1/1837 that of a proton. A beta particle can be stopped by an inch of wood or a thin sheet of aluminum.


Boiling Water Reactor

A nuclear reactor in which water is boiled in the reactor vessel; the resulting steam drives a turbine to generate electricity.

Breeder Reactor

A type of reactor that produces more fissionable material then it consumes.


Chain Reaction

A self-sustaining series of events occurring when a neutron splits a heavy atom releasing sufficient neutrons to cause many other atoms to split in the same way.

China Syndrome

A figure of speech which refers to a total meltdown of the core such that the molten core penetrates the reactor vessel and floor of the containment building and melts into the earth below(in fantasy, through the earth to China).



The zircaloy tube that encapsulates the fuel pellets. The pellets are stacked in the zircaloy tubes and bundled into fuel assemblies.


Cold Shutdown

A reactor condition in which the coolant temperature has been reduced to 200F or below, the pressure has essentially been reduced to atmospheric pressure, and the chain reaction is stopped.

Control Room

The operation center of a nuclear power plant from which the plant can be monitored and controlled.


A fluid, usually water, used to cool a nuclear reactor and transfer heat energy. The water also moderates, or slows down, the fissioning of neutrons.



The point at which a nuclear reactor is just capable of sustaining a chain reaction.


Critical Mass

The smallest amount of fuel necessary to sustain a chain reaction.



A device, such as a film badge, which can be worn and used to measure the radiation dosage a person receives over a period of time.



A subatomic particle with a negative electric charge and a mass 1/1837 that of a proton. It circles the nucleus of an atom.


Emergency Core Cooling System

A series of backup safety systems designed to inject thousands of gallons of cooling water into the reactor, thus maintaining the integrity of the core in the event the normal core cooling system fails.

Enriched Fuel

Uranium which has been modified by increasing the concentration of the fissionable isotope, Uranium-235. Enriched fuel is more able to sustain a chain reaction and is normally used as the fuel for a nuclear power plant.



The splitting or breaking apart of a heavy atom into two or more new atoms. When a heavy atom, such as uranium, is split, large amounts of energy and one or more neutrons are released.

Fission Products

The atoms formed when uranium is split in a nuclear reactor. Fission products are usually radioactive.


Fossil Fuels

Coal, oil or natural gas. These fuels are referred to as fossil fuels since they are the remains of plants and animals that lived on earth hundreds of millions of years ago.


Fuel Cycle

The sequence of steps involved in supplying, using and disposing of the fuel used in nuclear reactors.

Fuel Reprocessing

The processing of used reactor fuel to chemically separate the fuel into waste products, plutonium, and reusable uranium.

Geiger Counter

An instrument for detecting and measuring beta and gamma radiation.


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