Radiation Safety Guide



Radioactive Material Survey Procedures

The most common survey procedure to detect the presence of loose contamination is called a wipe test. In this procedure, a piece of filter paper (usually about 1 square or circular) is used to wipe over a surface suspected of being contaminated. The area which the wipe should cover is approximately 100 square centimeters. Depending on the surface being wiped or the type of material being surveyed for, it may be necessary to wet the wipe material with alcohol or other solvent for better adhesion of contaminated particles to the wipe. Wipe samples should include your working areas, floor space near your working areas, waste container areas and storage areas.

Analyze the wipe samples, using an appropriate instrument. Beta-emitting isotopes below 200 keV should be analyzed using a liquid scintillation or counting system. Wipe samples of gamma or x-ray emitters should be analyzed using a gamma counting system. Record on the survey diagrams the maximum contamination levels found as well as the final levels.

Portable survey instruments can also be used to survey for contamination. Geiger (GM) counters with thin window probes can be used to detect beta emitting isotopes with energies above 70 keV. Where gamma emitting isotopes are used, a survey instrument with a sodium iodide (NaI) probe should be used.

Before using any instrument, become familiar with its proper operation. To perform a survey using a potable instrument, scan the area suspected of being contaminated with the instrument's probe. To prevent possible contamination of the probe, do not let it touch the surface being surveyed. Any contamination found should be tested for removable contamination.

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