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Radiation Survey

Individuals processing radioactive material are required to perform routine surveys to ensure radiation exposures are maintained as low as reasonably achievable (ALARA).  There are three types of routine surveys:

Ambient Radiation Survey 

An ambient radiation survey is required when gamma-emitting radionuclides are used or stored.  Such isotopes include Co-57, Co-60, Tc-99m, I-125, I-131, Cs-137, Tl-201, etc.  A survey must be performed with an ionization chamber-type instrument.  Examples include Ludlum Model 9 and a Fluke Model 451P.
Individuals processing unsealed sources of radioactive material in a clinical setting must perform ambient radiation surveys every day.  The areas to be surveyed are customized to each department but must include work areas where radioactive material is received, processed, administered to patients and disposed. 
Before starting the ambient survey, individuals must ensure the batteries of the survey instrument are sufficiently charged.  The individual must also ensure the survey instrument is properly detecting radiation by surveying a sealed check source – typically 1 microcurie of Cesium-137.
Ambient radiation surveys are also required for therapeutic administrations of radioactive material.  In all cases, the performance of the ambient survey must be documented and available for review by Radiation Safety.
Ambient surveys should also include areas individuals are likely to touch with their hands – i.e. telephones, keyboards, doorknobs.  Individuals must also perform an ambient survey of their hands when leaving a controlled area.

Survey for Surface Contamination

Work areas, including bench tops, cabinets, storage areas, floors, etc must be surveyed daily for contamination.  Surveyed should be performed with meters appropriate to the types of radionuclides used in the area.  For example, a GM pancake detector is useful for detecting beta-emitting isotopes such as P-32, Y-90, and I-131; a NaI(Tl) detector should be used for gamma-emitting isotopes such as Co-57, Tc-99m, I-125, Tl-201.

Surveys should also include areas individuals are likely to touch with their hands – i.e. telephones, keyboards, doorknobs.  Individuals must also perform a survey of their hands when leaving a controlled area.

Survey for Removable Contamination (Wipe Test)

A wipe test survey is performed by swabbing a potentially contaminated surface with a media capable of absorbing radioactivity.  “Q-tips”, alcohol swabs and filter paper are all suitable media for a wipe test survey.
Individuals processing unsealed sources of radioactive material must perform wipe tests at least once a week.  The areas to be wiped are customized to each department but must include work areas where radioactive material is received, processed, administered to patients and disposed.  Ambient surveys should also include areas individuals are likely to touch with their hands – i.e. telephones, keyboards, doorknobs.  The individual performing a wipe test should swab an area equivalent to the palm of the hand.
Once collected, the wipes must be counted in a detection system capable of detecting radioactivity at levels below 200 dpm (approximately 0.1 nanocurie.)  A sodium iodide well counter or liquid scintillation counter typically offers an appropriate level of sensitivity.  A Geiger Counter is NOT sufficiently sensitive to analyze wipe tests.
The results of wipe tests must be documented and available for review by Radiation Safety.