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Using a survey meter

A radiation survey meter is used to detect moderate to high energy beta, gamma and x-ray radiation. This kind of meter is unable to measure low energy radioisotopes like tritium (H-3). The unit is composed of a probe to detect radioactivity, the base containing the electronics, and the meter face. Prior to using a survey meter, do the following :

  1. Check for a calibration sticker. The CNSC requires meters used for dose rate measurements (i.e. mR/hr or mSv/hr) to be calibrated annually.
    Note: instruments that read in counts per minute (cpm) or counts per second (cps) are called "contamination meters" and cannot be calibrated. Instead they are given a verification check on an annual basis to see if they operate well.
  2. Ensure that the probe is capable of detecting the radioisotope you are using. If unsure, contact the RSO.
  3. Check for tightness of cable connections. Loose cable connections can cause instrument damage.
  4. Perform a battery check.
  5. Turn the on/off switch to the lowest multiplication scale. Turn on the audio and ensure the unit is on the "F" position, if there is a F/S switch.
  6. Allow the unit to warm up (15-20 seconds). Determine the background. This should be done away from sources of radioactivity.
  7. Measure the area of radioactivity, by placing the probe as close as possible to the area being monitored without actually touching it. Note the audio function will guide you to the source of contamination.
  8. Find the highest count rate and record it in cpm. Determine the spread of the contamination. Take a wipe to determine if the contamination is removable.
  9. Never forget to turn off the survey meter once the work is completed.

Interpreting survey meter readings

When using an end window or pancake probe:

Survey Meter Readings

Assessment of Measurements

0-200 cpm / 0-0.05 mR/hr Background readings
200-400 cpm / 0.05-0.1 mR/hr Suspect contamination
>400 cpm / >0.1 mR/hr Contamination

Converting radiation meter readings

Units

Meter Readings

cps
0
2.5
5.0
7.5
10.0
12.5
 
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mR/hr
0
0.1
0.2
0.3
0.4
0.5
 
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µS/hr
0
1
2
3
4
5

To convert to cpm: cps x 60 = cpm