Glossary

Radiation: Energy in transit in the form of high speed particles and electromagnetic waves. Electromagnetic waves, including visible light, radio, television, ultra violet (UV) and microwaves, are all types of radiation that do not cause ionizations of atoms because they do not carry enough energy to separate molecules or remove electrons form atoms. These are all forms of non-ionizing radiation. Ionizing radiation is a very high energy form of electromagnetic radiation that has enough energy to remove tightly bound electrons from their orbits around atoms. Alpha, beta, gamma ray and neutron radiation are all ionizing radiation.

Radiation dose: The quantity of radiation energy deposited into an object or medium, divided by the mass of the object or medium. The radiation dose is ionizing radiation. Ionizing radiation doses can be expressed as an absorbed dose, equivalent dose, or effective dose. The basic unit of absorbed dose is the rad or its SI equivalent, the gray (Gy).

Radiation exposure: The act of being exposed to radiation. Also referred to as irradiation. Formally in radiation detection and measurement, radiation exposure is related to the ability of photons to ionize air.

Radiation sickness: See Acute Radiation Syndrome (ARS).

Radiation source: Radioactive material packaged to use the radiation it emits.

Radiation warning symbol: A universally recognized magenta or black trefoil on a yellow background that must be displayed where radioactive materials are present or where certain doses of radiation could be received.

Radioactive: Elements that are unstable and transform spontaneously (decay) through the emission of ionizing radiation, a process known as radioactive decay.

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

Radioactive decay: The spontaneous disintegration of the nucleus of an atom.

Radioactive material: Any material that contains radioactive atoms.

Radioactivity: Process of spontaneous transformation/breakdown of the nucleus, generally with the emission of alpha or beta particles, usually accompanied by gamma rays. This process is described as decay of the atom.

Radiography: The use of radiation to create images of a subject, especially the internal features of a subject. An example of medical radiography is a dental x-ray. Industrial radiography includes x-rays of pipes and reinforced concrete construction.

Radioisotope: Isotopes of an element that have an unstable nucleus.

Radiological: Related to radioactive materials or radiation. The radiological sciences focus on the measurement and effects of radiation.

Radiological dispersal device (RDD): Also known as a dirty bomb. A device to spread radioactive material for malevolent purposes. The objective of such a device would be to cause social disruption and panic.

Radioisotope: A radioactive/unstable isotope that undergoes spontaneous transformation, emitting radiation.

Radionuclide: An atom with an unstable nucleus which undergoes radioactive decay. A radioactive nuclide.

Radium: A naturally occurring radioactive material (NORM) formed by the decay of uranium and thorium. It occurs at low levels in virtually all rock, soil, water, plants and animals. Radon is a decay product of radium.

Radon: A naturally occurring radioactive gas found in rock, soil and water throughout the United States. Radon is the largest source of exposure to people from naturally occurring radiation.

Reciprocity: The act of one licensing agency honoring the license of another agency. Companies desiring to use their gauges outside of their own state must notify and receive permission to carry the gauge into another state. License holders in a NRC regulated state can use their gauges in another NRC state without obtaining reciprocity permission. License holders in an Agreement State may also need to obtain reciprocity before entering a NRC regulated area such as a military installation.

Regulations: The rules and requirements of a license. All license holders must maintain, review and update a copy of the regulations from their regulatory agency.

REM (Roentgen equivalent, man): The special unit of dose equivalent. Not all radiation has the same biological effect, even for the same amount of absorbed dose. The dose equivalent in rem is equal to the absorbed dose in rad multiplied by the quality factor that accounts for the biological effect of the radiation. (1 rem = 0.01 sievert). This relates the absorbed dose in human tissue to the effective biological damage of the radiation. To determine the equivalent dose (in rem) you multiply the absorbed dose (rad) times the quality factor (Q).

RQ – Reportable Quantity: An EPA designation that establishes thresholds for quantities of radioactive materials used in gauges. An RQ designation must appear on the Type A Package Label and shipping papers for gauges that contain Am241 in excess of 10mCi. All moisture density gauges exceed this limit and must therefore show the designation.

Roentgen: A unit of measure to exposure to gamma and x-rays. It is that amount of gamma or x-rays required to produce ions carrying 1 electrostatic unit of electrical charge in 1 cubic centimeter of dry air under standard conditions. Named for Wilhelm Roentgen, discoverer of x-rays in 1895.