Glossary

Cesium 137 (Cs137): Radioactive isotope of Cesium which decays by beta emission into barium 137m, which in turn emits a photon for measuring density. Cs137 has a half-life of 30.17 years.

Chronic exposure: Exposure to a source of radiation over a longer period of time, typically greater than 24 hours.

Contamination (radioactive): Contamination means that radioactive materials are released in the form of solids, gases or liquids into the environment and contaminate people externally, internally or both.

Controlled area/zone: An area where entry, activities and exit are controlled to help ensure radiation protection and prevent the spread of contamination.

Cosmic Radiation: Radiation produced in outer space that enters the earth’s atmosphere.

Count: Electronic pulse from a radiation detector tube that indicates an ionizing event. Portable nuclear gauges use Geiger-Muller tubes to detect ionizing events.

CFR: Code of Federal Regulations

Chronic dose: A chronic dose means a person received a radiation dose over a long period of time. Example: 300mrem per year.

Chronic Radiation Exposures: Radiation exposures that occur over extended periods of time (greater than 24 hours). Exposure to natural background is a chronic radiation exposure.

Contamination: Radioactive material distributed and in contact with some person, equipment or area. Requires decontamination efforts.

Critical Mass: The minimum amount of fissile material necessary to achieve a self-sustaining nuclear chain reaction. Nuclear gauges only contain non-fissile material and are therefore not capable of creating a chain reaction.

Curie (Ci): The basic measure of radioactivity equal to an average transformation of 37 billion disintegrations per second. One curie is the approximate activity of 1 gram of radium. Named for Marie and Pierre Curie, founders of radium in 1898.