A charged nuclear particle emitted from the nucleus of an atom. It cannot penetrate clothing or the outer layer of the skin.

A design change in operating nuclear power plants required by safety-related regulatory decisions.

A charged nuclear particle emitted from the nucleus of an atom. Some beta particles can penetrate skin, but, like alpha particles, they may cause the most serious side-effects when they are inhaled or ingested.

A nuclear reactor designed to produce more fissionable fuel than it consumes. No commercial breeder reactors are operating in the United States.

High-energy electromagnetic radiation emitted from nuclei as a result of nuclear reactions or decay. It has the greatest penetrating power and usually accompanies beta radiation. It can penetrate and damage human organs. Most fission products are gamma and beta emitters.

A nuclear reactor that uses ordinary water as its coolant and moderator. There are two commercial types of light water reactors: the boiling water reactor and the pressurized water reactor.

The unit by which the rate of electricity production is usually measured. One MW equals one million watts or one thousand kilowatts.

A radioactive species of an atom characterized by the constitution of its nucleus.