The University of Arizona

The Radiation Control Office

Multimedia Learning

How to Perform an Instrument Survey

How to perform an instrument survey for radioactive material use:

(For Ludlum instruments, call the RCO for help with other manufacturers)

1. Check the calibration – If the calibration date is greater than one year old, contact the RCO
2. Check the batteries – turn knob to “bat test” and check that needle falls within the battery testing area on the meter face. If it does not, replace the batteries and perform the battery test again. If the battery test does not pass after installation of fresh batteries, contact the Radiation Control Office (RCO).
3. Use the “counts per minute” (cpm) scale for contamination surveys. Do not use the mR/hr scale. Pay attention to the multiplier dial. For example, if the meter reads 2K and you are on the 0.1 scale, the reading is 200 cpm.
4. Remove the red cap (if present). This is a protective covering, not a beta shield. If a protective covering is desired, use plastic wrap or other thin material (no parafilm).
5. Test the check source
   1. Put the probe window flat onto the check source on the side of the instrument. Center the window over the surface of the check source.
   2. The reading should be within the range indicated on the calibration sticker. If it is not within the stated range, contact the RCO.
6. Obtain a background reading
   1. Take meter away from all radioactive material
   2. Turn dial to the lowest scale and take a reading with the probe waste at waste height
   3. If the meter’s needle swings beyond full scale, go up to the next scale.
   4. Record the background
   5. Typical background for a pancake probe is less than 100 cpm and for a low energy gamma (LEG) probe background is approximately 300 cpm or less.
      1. If the meter’s background reading is substantially greater than expected, confirm that there are no unexpected sources of radiation or radioactive materials in the vicinity, then call the RCO.
7. Survey the area
   1. Hold the probe no more than 1 cm away from the surface being surveyed. Ensure the probe does not touch the surface.
   2. Slowly move the probe over the area in a S pattern going about 1inch per second.
   3. Monitor the meter reading and/or the instrument audio to identify areas of concern or potential contamination.
8. Identify and clean contaminated areas - If a measurement is greater than 50 counts above the background, the area is considered contaminated. When contamination is found:
   1. Hold the probe over area until the meter reading stabilizes.
   2. Record the reading
   3. Clean the area
   4. Perform the survey again.
   5. Repeat the cleaning and survey until the contaminated area is below 50 cpm above background. If the contamination persists, contact the RCO.
9. Turn the meter off to preserve the batteries.
10. Document after use and/or monthly surveys as required.