A unit of absorbed dose. One rad is 0.01 Joule absorbed per kilogram of any material. Also defined as 100 ergs per gram. Rad is being replaced by gray (Gy). One rad equals 0.01 gray.

RADIAC is the acronym for radiation detection, identification and computation. RADIAC equipment is used to detect, identify, and measure radiation.

The spontaneous decay or disintegration of an unstable atomic nucleus, usually accompanied by the emission of ionizing radiation, such as alpha (a) or beta (ß) particles or gamma (g) rays.

The isotopes of an element that are unstable (radioactive).

A radioactive species of atom characterized by the makeup of its nucleus (the number of protons, the number of neutrons, and the energy content) which causes the nucleus to be unstable.

A heavy radioactive gaseous element formed by the decay of radium.

A unit of dose, called the "dose equivalent," that is used in the regulatory, administrative, and engineering design aspects of radiation safety practice. The dose equivalent in rem is numerically equal to the absorbed dose in rad multiplied by the quality factor (1 rem is equal to 0.01 sievert).

Relating to the kidneys.

Extending in scope or effect to a prior time or to conditions that existed or originated in the past.

A measure of the chance that an undesirable event or effect may actually happen. For example, a risk of 1x10-6 means that there is one chance in a million of the event happening. As applied to radiation risk, this means that if 1,000,000 persons received a certain radiation dose, then we would expect that one person may show the harmful effect. The estimated risk from low doses of radiation, where no harmful effects have actually been seen, is extrapolated from high radiation doses, where the effects have been seen. In making this extrapolation, it is assumed that the chance of injury from the low dose is proportional to the chance of injury from the high radiation dose.

A measure of exposure to X and gamma radiation. Although a roentgen does not directly provide exact information about the radiation close to the exposed person, an exposure of one roentgen results in a dose equivalent of one rem. Named after William Roentgen, a German scientist who discovered x-rays in 1895.