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

Half- life Calculator

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.


Week 5 Glossary of Terms

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