Unit 5 Glossary of Terms
ALARA: “As Low As Reasonably Achievable” Personnel working in the field are required to keep their radiation exposures ALARA.
Gamma Rays: High energy, short wavelength electromagnetic radiation emitted during radioactive decay.
Gamma Radiography: Radiographs (film, DDA plates, and CR plates) are exposed using a gamma ray camera or radiograph-shooting machine, which can be portable, fixed in a cabinet or located in a vault.
Gamma Source (source): Industrial gamma radiography typically uses a man=made (activated) radiation source (Cobalt-60, Iridium-192, and Cesium-137). These sources are typically created for specific purposes and applications.
Half-Life: the amount of time required for ½ of the original number of radioactive atoms to decay or change into daughter atoms.
Half-Life Ir 192: 74 days
Half-Life Co 60: 5.3 years
Half-Life Cs 137: 30.17 years
Biological half-life: the amount of time required for one half of a radioactive substance to be removed (from a human) by the natural biological processes (urination, sweating, bowel movements, vomiting)
HVL (Half-Value Layer): The amount (thickness) of a given shielding material needed to reduce the radiation emissivity by one-half it’s value.
HVL Formula: Io = Original Intensity Id = Desired intensity
Ionizing Radiation: a type of radiation that is able to disrupt atoms and molecules on which they pass through, giving rise to ions and free radicals.
Time, Distance, and Shielding: These are the three basic tenets of Radiation Safety and the ALARA doctrine.
