Radioactive material authorizations which are currently in “active” status are required to survey weekly or monthly, depending on the amount of activity used per experiment, and document these results.

Each group is responsible for performing and documenting their own surveys, with a frequency dependent on the levels of use.  Because of the size of our institution and the number of groups Radiation Safety services, we do not have the staff to perform the required surveys of every lab.  Radiation Safety does conduct “confirmatory” surveys on each authorization during every inspection.

If you cannot find the information you are looking for in the sections below, please contact the Radiation Safety Office at 314-362-3476 or

Conversion From CPM To DPM

This conversion is necessary, as we are required by our NRC license to document wipe test results in dpm.  Many counters will do the conversion for you.  If yours does not, you’ll need to do the conversion manually before recording results.   Following is the formula to use to convert cpm to dpm:

  • dpm = (cpm – BKG)/efficiency

As you can see, you will need to count a background vial (be sure it is in the first position IF your LSC has first position background subtraction!) and know the efficiency of your liquid scintillation counter (LSC) for the isotopes you’re counting.  Many LSC operating manuals will list this information.  If yours does not, you can use the following common efficiencies:

  • P-32 (95%)
  • S-35 (80%)
  • H-3 (50%)
  • C-14 (60%)

For more assistance in determining efficiencies, please call Radiation Safety.

Hand-Held Radiation Detector Information And Repair

Radiation Safety recommends the use of Ludlum model 2 or 3 Geiger counters.  The type of probe can be customized to your needs, but a pancake probe is a good, general-purpose probe that makes surveying areas quick and easy.

If your Geiger counter needs repair, please contact Radiation Safety as we can do minor repairs.   If any repair is beyond the scope of our capabilities, we will refer you to a repair vendor.  To directly contact a repair vendor, please refer to the document Survey Meter Repair Vendors.

Recommended LSC Cocktails

We highly recommend using only non-flammable (or non EPA-regulated) scintillation cocktail.  Please contact Radiation Safety at 314-362-2996 if you have a questions about your scintillation cocktail.

Survey Types And Survey Frequency Requirements

All authorizations that use or store RAM in unsealed form are required to perform and document wipe tests.  Authorizations that contain any gamma emitter(s) in unsealed form are also required to perform and document survey instrument readings at all the same locations. 

Each user group will need to survey weekly or monthly, depending on the amount of activity used per experiment, and document these results.  Typically, if less than 200 uCi of activity (any isotope) is used per application, monthly documented surveys are required.  Anytime greater than 200 uCi is used, weekly surveys will need to be performed.  There should be no more than 30 days in between monthly surveys, and no more than 7 days in between weekly surveys.  

Surveying With No Radioactive Materials Of Any Kind In The Lab

If your lab’s radioactive materials authorization is currently on “active” status, and you are approved for radioactive materials in unsealed form, you are still required to perform documented lab surveys.  This must be done at least monthly, and must include both wipe AND meter surveys.   The areas to be surveyed are: all designated “break rooms” (individually, not batched together); all RAM-approved drains; and at least five other areas in the main lab (excluding break rooms and RAM sinks).   These final five locations should be rotated every month, so eventually a greater portion of the lab will be surveyed.  In order to have this survey requirement suspended, your AU’s authorization must first be officially placed on “inactive” status.  Please contact Radiation Safety at 314-362-3476, for more information on “inactive” status. 

Training On Survey Meter Use

Click here for training on meter use.