Surveys for radiation and radioactive contamination must be performed AFTER EACH USE of radioactive material. The purpose of this survey is to identify any contamination present and to prevent its spread.
A formal survey for radioactive contamination and radiation levels (if appropriate) must be performed and recorded on forms provided by EH&S at least once in each month that radioisotopes are handled, or at such other times or intervals as specified by EH&S.
Required surveys must be performed by adequately trained personnel. A copy of the survey report form must be sent to EH&S by the first of the month. Keep the other copy with raw data attached in your lab binder.
A Notice of Violation will be sent if the survey is not received on time. This Notice of Violation temporarily suspends the lab's privilege to order and receive additional radioactive material until the survey is performed,properly documented and submitted to EH&S.
In addition to the monthly survey requirement, weekly surveys may be required whenever large quantities of radioactive material are received in the laboratory. Whenever weekly surveys are required, users are notified and survey forms provided.
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 yourself, your working areas, floor space near your working areas, and any other area where contamination may be likely.
Analyze the wipe samples, using an appropriate instrument. Beta-emitting isotopes below 200 keV (H-3, C-14, S-35, etc.) must be analyzed using a liquid scintillation counting system. Wipe samples of gamma or x-ray emitters (I-125, Cr-51) should be analyzed using a gamma counting system.
Data from the wipe survey must be transferred to the appropriate survey form which must include a background, standard counts and counter efficiency for each isotope used.
Portable survey instruments must also be used to survey for contamination (other than H-3). Before using any instrument, be sure to check it for proper operation. To perform a survey using a portable instrument, scan the area suspected of being contaminated with the instrument's probe. To prevent possible contamination (and damage) to the probe, do not let it touch the surface being surveyed. Geiger (GM) counters with thin window probes can be used to detect beta emitting isotopes with energies above 70 keV such as S-35 and P-32. Where gamma emitting isotopes are used such as I-125 and Cr-51, a survey instrument with a sodium iodide (NaI) probe should be used. Refer to the calibration sticker affixed to the side of the instrument for the efficiency of the detector for the nuclide being detected. Also remember to perform a battery check, obtain a background reading and count the attached instrument check source prior to using the survey meter.
Any contamination found should be wipe tested for removable activity. Hold the wipe material about 0.5 cm away from the detector and observe the count rate. Record on the survey diagrams the maximum contamination levels found (removable and fixed) as well as the final levels after decontamination.