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Using a Survey Meter

Radiation Survey Meter – Description and Use

Purpose and limitations

  • Used to detect moderate‑ to high‑energy beta, gamma, and X‑ray radiation
  • Cannot detect low‑energy beta emitters, such as tritium (H‑3)
  • Not appropriate for measuring tritium contamination

Components

  • Probe – detects radiation
  • Base unit – houses electronics
  • Meter face/readout – displays measurements

Pre‑use checks

Before using a radiation survey meter, ensure the following:

Calibration and compliance

  • Verify the presence of a valid calibration sticker
    • The CNSC requires annual calibration for meters used for dose‑rate measurements (e.g., mR/hr or mSv/hr)
  • Note:
    • Instruments that read in counts per minute (cpm) or counts per second (cps) are considered contamination meters
    • These instruments cannot be calibrated and are instead verified annually for proper operation

Instrument suitability

  • Confirm the probe is appropriate for the radioisotope being used
  • If uncertain, contact the Radiation Safety Officergurnam.manku [at] affiliate.mcgill.ca ( (RSO))

Equipment condition

  • Ensure all cable connections are secure
    • Loose connections may damage the instrument
  • Perform a battery check

Operating the survey meter

  • Set the scale to the lowest multiplication range
  • Turn on the audio function
  • If the instrument has an F/S switch, ensure it is set to “F”
  • Allow the meter to warm up for 15–20 seconds
  • Measure and note the background radiation level
    • Perform this step away from radioactive sources

Surveying for contamination

  • Hold the probe as close as possible to the surface without touching it
  • Use the audio signal to help locate contamination
  • Identify and record the highest count rate (cpm)
  • Assess the extent of contamination
  • Perform a wipe test to determine whether contamination is removable

After use

  • Turn off the survey meter once monitoring is complete

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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µ/
0
1
2
3
4
5

To convert to cpm: cps x 60 = cpm

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