Glossary

TERMS

Activation: The process of making a radioisotope by bombarding a stable element with neutrons, protons, or other types of radiation
Alpha particle: A positively charged particle ejected spontaneously from the nuclei of some radioactive elements with very low penetrating power and a short range. Alpha particle will generally be easily stopped by a sheet of paper.
Atom: The smallest particle of an element that cannot be divided or broken up by chemical means consisting of a central core of protons and neutrons, called the nucleus, with electrons revolving in orbits surrounding the nucleus.
Attenuation: Attenuation is the process by which the number of particles or photons entering a body of matter is reduced by absorption and scattering.
Background radiation: Radiation from cosmic sources; naturally occurring radioactive materials, including radon (except as a decay product of source or special nuclear material), and global fallout as it exists in the environment from the testing of nuclear explosive devices. The average individual exposure from background radiation is approximately 360 millirems per year.
Becquerel (Bq): The unit of radioactive decay equal to one disintegration per second. The Becquerel is the basic unit of radioactivity used in the international system of radiation units, referred to as the “SI” units. 37 billion becquerels = 1 curie (Ci).
Beta particle: A charged particle emitted from a nucleus during radioactive decay, with a mass equal to 1/1837 of a proton. Thin sheets of metal or plastic may stop beta particles.
Curie (Ci): The original unit used to express the decay rate of a sample of radioactive material. . It was based on the rate of decay of atoms within one gram of radium. It is named for Marie and Pierre Curie who discovered radium in 1898. The curie is the basic unit of radioactivity used in the system of radiation units in the United States, referred to as "traditional" units.
Detector: A material or device that is sensitive to radiation and utilized for measurement or analysis. A radiation detection instrument.
Dose: A general term used to refer to the effect on a material that is exposed to radiation. It is used to refer either to the amount of energy absorbed by a material exposed to radiation or to the potential biological effect in tissue exposed to radiation
Dosimeter: A small portable instrument (such as a film badge, thermoluminescent or pocket dosimeter) for measuring and recording the total accumulated dose of ionizing radiation.
Dosimetry: The theory and application of the principles involved in the measurement of ionizing radiation doses.
Electron: A negatively charged beta particle.
Exposure: A general term used loosely to express what a person receives as a result of being exposed to ionizing radiation.
Film badge: Photographic film used for measurement of ionizing radiation exposure for personnel monitoring purposes
Gamma radiation: High-energy, short wavelength, electromagnetic radiation emitted from the nucleus of an atom. Gamma radiation frequently accompanies the emission of alpha and beta particles
Geiger-Mueller Counter: A radiation detection and measuring instrument. It is also called simply a Geiger counter or a G-M counter, and is the most commonly used portable radiation measuring instrument.
Half-life: The time in which one-half of the activity of a particular radioactive substance is lost due to radioactive decay.
Health Physics: The science concerned with the recognition, evaluation, and control of health hazards to permit the safe use and application of ionizing radiation.
Mrem (Millirem): One thousandth of a rem.
NCRP: The National Council on Radiation Protection and Measurements
Neutron: An uncharged elementary particle with a mass slightly greater than that of the proton, and found in the nucleus of every atom heavier than hydrogen.
NORM: An acronym for Naturally Occurring Radioactive Material. Naturally occurring radioactive materials are common in virtually all rocks, minerals, and soils. They naturally contain small amounts radioactive isotopes. Plants and animals are also naturally radioactive; they contain very small levels of radioactive materials that are formed by cosmic ray interactions in the atmosphere.
Photon: A quantum (or packet) of energy emitted in the form of electromagnetic radiation. Gamma rays and x rays are examples of photons.
Positron: A positively charged beta particle
Rad: The original unit developed for expressing absorbed dose, which is the amount of energy from any type of ionizing radiation such as alpha, beta, gamma, x-rays, neutrons, etc. A dose of one rad is equivalent to the absorption of 100 ergs (a small but measurable amount of energy) per gram of absorbing tissue. The rad has been replaced by the gray in the SI system of units (1 gray = 100 rad).
Radiation area: Any area with radiation levels greater than 5 millirems in one hour at 30 centimeters from the source.
Radiation (diagnostic): Alpha, Beta, Gamma, X-Ray, Protons, Neutron and other energy given off as either particles or rays from the unstable nucleus of an atom
Radioisotope: An unstable isotope of an element that decays or disintegrates spontaneously, emitting radiation. Approximately 5,000 natural and artificial radioisotopes have been identified.
Radiological survey: The evaluation of the radiation hazards under a specific set of conditions. Such evaluation customarily includes a physical survey of materials and equipment, measurements or estimates of the levels of radiation that may be involved
Radiology: The medical diagnostic imaging and therapeutic treatment applications of radiant energy, including x rays and radioisotopes.
Rem (Roentgen): A unit in the traditional system of units that measures the effects of ionizing radiation on humans.
Scatter radiation: Radiation that, during its passage through a substance, has been changed in direction. It may also have been modified by a decrease in energy. It is a form of secondary "scatter" radiation.
Sievert (Sv): The international system (SI) unit for dose equivalent equal to 1 Joule/kilogram. The sievert has replaced the rem. One sievert is equivalent to 100 rem.
Shielding: Any material, product or other obstruction that absorbs radiation and thus tends to reduce or protect personnel, equipment or materials from the effects of ionizing radiation.
X-Rays: Penetrating radiation having a range of wavelengths (energies) that are similar to those of gamma photons. X-Rays are usually produced by excitation of the electron field around certain nuclei.