Glossary
Atom — Building blocks for all matter. Smallest particle of an element that has the chemical properties of that element.

Cladding — Outer covering of nuclear fuel. Usually a metal rod containing hundreds of nuclear fuel pellets each about the size of a pencil eraser.

Containment or reactor building — Steel reinforced concrete building housing the reactor and other nuclear components. The building is designed to keep radioactive materials from escaping into the environment even if other plant systems are severely damaged.

Contamination — Radioactive materials located anywhere they shouldn’t be. Removed by decontamination – usually washing with ordinary soap and water.

Core — Nuclear fuel rods inside the reactor. Where heat-producing fission occurs.

Criticality — The point at which fission becomes selfsustaining in a nuclear reactor.

Decay heat — Heat produced by radioactive materials as they become less radioactive or “decay.” This heat is produced in the reactor after it is shut down. Many plant safety systems are designed to remove this heat.

Dose — Measure of a person’s radiation exposure. Dose is usually measured in millirems, units that take into account the biological effects of radiation. An average South Carolinian’s radiation dose from his or her natural environment is about 200 millirems.

FEMA — Abbreviation for the Federal Emergency Management Agency. This branch of the federal government oversees nuclear emergency plans of states and counties.

Fission — Splitting of atoms. In a nuclear plant, atoms of uranium fuel split giving off heat used to make steam for generating electricity.

Fission products — Radioactive by-products produced in the fission reaction. Plant safety systems and emergency plans are all designed to protect the environment from these fission products.

Millirem — A measure of radiation that takes into account the effects of radiation on humans. One thousand millirems make one rem.

NRC — Abbreviation for Nuclear Regulatory Commission, a federal agency that oversees nuclear power plant operation and construction.

Primary side or loop — Term for water systems that flows over nuclear fuel in the reactor picking up heat from the fission process. It transfers this heat to a separate water system, the secondary side, producing steam used to generate electricity.

Radiation — Energy in the form of minute particles or waves given off by materials that are radioactive. More familiar types of wave energy are heat, light, radio waves and microwaves.

Radioactive — Unstable atoms that give off radiation as they become more stable. Radioactive elements become less radioactive or “decay” over time. The time that it takes for an element to become half as radioactive is referred to as its “half-life.” This time varies from a few minutes for some elements to thousands of years for others.

Reactor — Large steel vessel containing the nuclear fuel where fission takes place.

Trip or Reactor Trip — An immediate shut down of the fission process inside the reactor. This safety precaution occurs automatically any time instruments detect potentially unsafe conditions in the plant.
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