Radiation Safety
Radiation Survey Procedures
- Check gloves frequently when working with radioactive material.
- Survey work area after each use of radioactive material.
- At least once a month (or at a frequency specified in your radiation permit), randomly survey locations outside of normal radioactive material use and storage.
- Don protective equipment, such as gloves, before performing survey.
- Check survey instrument. If using a GM probe + ratemeter (commonly known as a Geiger counter) or NaI probe + ratemeter, see "instrument check list."
-
Perform survey appropriate to
the isotope(s) used.
- For low-energy beta emitters (H-3, C-14, S-35, etc.), take swipe samples and count using liquid scintillation counting.
- For high-energy beta emitters (P-32, etc.), take swipe samples and count using either liquid scintillation counting or a ratemeter + GM probe. Floors and surfaces can also be directly monitored using a ratemeter + GM probe.
- For low-energy gamma emitters (I-125, etc.), take swipe samples and count with a ratemeter + thin crystal NaI probe or a gamma counter. Floors and surfaces can also be directly monitored using a ratemeter + thin crystal NaI probe.
- If using a ratemeter + probe, hold the probe window 1 cm from the surface to be surveyed and move the probe over the surface at a rate of approximately 1 cm/second. If surveying for alpha or beta contamination, do not put plastic or parafilm over the probe window, as alpha and lower-energy beta particles will not be able to reach the probe window.
- Make sure to check the most common sites for contamination, such as survey meter, soap/towel dispensers, drawer handles, refrigerator/freezer handles, chair edges, writing utensils, survey record books, floors, radio dials, telephone receiver/keypad, microwave oven touch pads/handles, and non-radioactive trash containers.
-
Record survey results in
survey record. The record should contain
- Date survey was performed
- Area(s) surveyed
- Survey results
- Identity of surveyor
- Instrument used for survey
- If contamination was found, the action taken
Instrument check list
To check the operation of a ratemeter with either a GM probe or a NaI probe,
-
Check battery -
- Turn the switch on the ratemeter to "BATT" or flip the "BATT" switch to "ON."
- The needle on the meter face should move to a position within or beyond the indicated area on the meter face scale.
- Replace batteries if needed before use of the ratemeter.
-
Check speaker -
- If there is an audio switch on the ratemeter, turn it to "ON."
- Set the ratemeter to a scale of "X1."
- The ratemeter should "chirp" or "click."
- If the speaker does not function, the survey meter can be used, but the surveyor will need to check the reading on the ratemeter face frequently.
-
Check background -
- Go to an area with an expected low background rate.
- Note the count rate when the ratemeter is switched to the "X1" scale.
- The background rate will vary from as little to 10 counts per minute up to several hundred counts per minute.
- Do not use the survey meter if it does not register a background rate.
-
Check probe -
- Hold the supplied check source (often a thorium lantern mantle) up to the probe window.
- Note the counting rate.
- Do not use the survey meter if the counts per minute registered does not fall within +/- 20% of the expected reading for that check source.
Questions?
Contact the Division of Research Safety, Radiation Safety Section (333-2755 or via e-mail) or visit our website: http://www.drs.illinois.edu/rss/.
Other Radiation Safety Fact Sheets are available from the Radiation Safety Section at our website: http://www.drs.illinois.edu/rss/factsheets/.
