K. Surveys

Survey records must be documented on a Radiation Survey Data Sheet and filed in the Radionuclide Inventory and Survey Book. These records must be kept for three years.

A wipe survey is required after each experiment using unsealed quantities of activity in excess of the limits specified below:

AFTER EACH EXPERIMENT (Table 3)

Wipe surveys should be performed in radionuclide use areas such as lab benches, hood sills, sinks, etc. Also, areas where contamination would not be expected should be included as part of the survey (e.g., refrigerator handles, telephones, desks, etc.). These areas should be chosen at random in addition to the routine survey locations. One other area that should be included in the survey is the floor in the doorway of the laboratory. Contamination in this location may indicate a more widespread problem (i.e., contamination leaving the laboratory).

Preceding a wipe survey with a direct radiation survey (e.g., using a thin, end-window GM meter) may aid in locating contaminated areas within the laboratory. However, this type of survey is only applicable in laboratories where medium to high energy beta emitters (e.g., ³²P and ³⁶Cl) or gamma emitters are used. Any elevated direct radiation reading which may be associated with contamination should be followed up with a wipe survey in that location to determine if the contamination is fixed or removable.

The actual wipe survey consists of rubbing a filter paper or Q-tip over an area of approximately 100 cm². Care should be taken to prevent cross contamination between wipe samples. These wipes should be counted in a liquid scintillation counter (LSC) or gamma counter as appropriate.

Wipe surveys from several locations which are above background but less than the levels specified in the limits below may indicate a widespread contamination problem. This may require a review of procedures. If gross ( > 50,000 cpm) or widespread contamination is detected, immediately notify the RSO.

Wipe surveys should typically be counted in the same instrument utilized for counting the samples associated with the clinical/research procedure (e.g., liquid scintillation counter or gamma counter). The instrument should be set to count for the radionuclides used in the laboratory. If wipes are to be counted for beta and gamma radionuclides, both a liquid scintillation and gamma counter should be used. In all instances, the window should be set wide enough to capture all energies or multiple windows may be used. Presets, if available on the instrument, may also be used; however, the window for the preset should be verified as appropriately established for the radionuclide in question.

The table below provides channel setting suggestions for some common radionuclides. When in doubt, a wide open window should be used (e.g., 0-2000 keV).

Table 4

*The energies listed in Table 4 for beta-emitting radionuclides provide the average beta particle energy.

The results (printout) from the counting instrument should be included and keyed to a diagram of the laboratory(s) with the wipe numbers corresponding to a number on the diagram. Make sure to include all labs and areas of radioactive material use (e.g., specific-use areas, shared labs, etc.).

The completed Radiation Survey Data Sheet must be placed in the Radionuclide Inventory and Survey Book. Although a PH may assign one individual to perform the appropriate surveys at the required frequency, all radionuclide users should know how to perform and document the surveys to prevent the omission of surveys when the responsible individual is absent. In addition, all lab personnel should know the location of this manual and the Radionuclide Inventory and Survey Book.

During time periods of inactivity (i.e., for months when radionuclides are not used), wipe and direct surveys are not required; however, documentation must be made in the survey book each month to indicate the reason for the omission of the required surveys.