How to Perform a Swipe Survey and use an LSC

In order to determine if there is any unfixed contamination in the lab, swipe (or wipe) surveys are the best tool. These swipes will then be counted in an appropriate radiation detector, usually a liquid scintillation counter (LSC). Swipe tests are the only reliable method of determining H-3 contamination without special equipment.

Contact Radiation Safety if you need help identifying an LSC for you to use.

Taking Swipes

Be sure to use appropriate media (paper filters, cotton swabs, glass fiber filters, etc.) and adequately cover the laboratory. Each swipe should cover at least 100 cm2, which can be accomplished by using medium pressure and drawing an “S” over a 2’x2’ (60cm x 60cm) square. These swipes should then be segregated to prevent cross contamination between swipes before counting.

Counting Swipes

Swipes should be loaded into an appropriately sized LSC vial. LSC cocktail (counting fluid) will then be added to the vial and then the vials will be placed into LSC racks and counted. Be sure to use a counting protocol that is programmed to detect the radionuclides being used by your lab. A background sample (a clean swipe in cocktail) should be prepared and run along with your swipes. Contamination is considered to be any swipe sample that is found to have a count rate greater than two times the count rate of the background sample.

Addressing Contamination

All contamination outside of radioactive work area must be cleaned  and resurveyed until the count rate is below two times background. Contamination limits inside radioactive work areas are outlined in the Radiation Safety Manual. Contact Radiation Safety if you are having difficulty with any decontamination efforts or if you have any questions about setting up LSC protocols, counting consumables, or other general questions.