Surveying the Lab for Contamination

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Surveying your lab is important to ensure contamination is not being spread. It also allows you to know where radioactive sources are and minimize any potential exposures. Are you trying to:

• Document your survey and swipe results?
• Use your survey meter?
• Use your Liquid Scintillation Counter?
• Perform a swipe survey?
• Calibrate your instrumentation?

 

HOW TO DOCUMENT A SURVEY

Documented surveys shall reference a map of the area surveyed, or clearly describe the locations monitored. Records of the survey shall include

• Locations where swipe samples were taken;
• Printout results from swipes counting (Instrument printout shall be attached in its entirety, including counting date and instrument-specific information.);
• Removable contamination reported in disintegrations per minute (dpm) (If counts per minute (cpm) are recorded, then the record shall also include a documented conversion to dpm.);
• Locations where swipes indicated levels are above 200 dpm per 100 cm2, instrument contamination readings greater than 0.3 mR/hr, and area radiation levels are greater than or equal to 0.2 mR/hr;
• Instrument used;
• Date of survey;
• Name or initials of person performing the survey.

When contamination or radiation levels are found above Table 2 or Table 3 action levels found in the Survey Requirements, then records shall also indicate the corrective action(s) taken to eliminate or minimize the excessive levels found, including the print out results of the re-surveyed areas. 

Inspection Survey Records shall be kept readily available for review by RW’s, AU’s, RSS, and NRC. 

 

HOW TO USE YOUR SURVEY METER

A survey meter is probably your most useful tool in assessing contamination in the laboratory when you are working with radioactive materials. It can be used to identify areas of contamination in the work area and to survey areas where you don't suspect contamination. It should also be used to check yourself to ensure that you have not contaminated your lab clothing, personal clothing and, most importantly, your skin.

Tritium (H-3) is not detectable with a standard GM meter. You must rely on swipe data for meaningful information. Listed below are some helpful reminders on how to check your meter prior to surveys and how you should operate your meter.

PRE-OPERATIONAL CHECKS

• Make sure your meter has been calibrated within the past year.
• Use your battery check switch to ensure that there is enough battery power to operate your meter.
• Use a check source to ensure that your meter responds to a radiation field. If no check source is available, you can check the meter against a known radiation source. 

Note: If your meter fails any of the above tests, it is not valid for meter surveys. You can request a loaner meter from EHS while yours is being calibrated or fixed. To have your meter calibrated, see the How to Maintain Instrument Calibrations section on this page.

OPERATION

When surveying for contamination using a GM (or appropriate detector), use a slow sweeping motion (5-8 cm per second) approximately 1 cm away from the surface being surveyed. Be careful to avoid sharp objects when surveying. The probe window is fragile and could puncture (about $100 to replace). 

Remember to use the survey meter to check for areas where you also may want to swipe. Just because you can't see contamination on the meter does not mean that it is not there. Conversely, you may find contamination with the meter and not a swipe because it may be "fixed" and not readily removable.

 

HOW TO USE YOUR LIQUID SCINTILLATION COUNTER

Before beginning actual system operation, the user should become familiar with the identification of all system controls and indicators and their functions as related to use during system operation by referring to the manufacturer's operation manual.

MATERIALS NEEDED

• Drawing of the area to be surveyed,
• Swipes,
• Pen to mark the drawing and the swipes.  Swipes need to be marked or pre-numbered by manufacturer to match the swipe location on the drawings, 
• Scintillation vials and media,
• Liquid Scintillation Counter (LSC) and/or Gamma Counter, with a pre-programmed protocol or setting corresponding to the energy of the suspected contaminant (radioisotope), 
• Survey meter to check contaminated swipes throughout survey for gross indication of contamination,
• Pad or envelope to secure or hold the swipes as they accumulate, such that they do not "cross-   contaminate" other swipes, and
• Gloves, safety glasses, and lab coat.

PERFORMING METER CONTAMINATION SURVEYS

• Should be performed first to identify “hot” spots to be swiped.
• Identify swipe locations on drawing of lab.
• Number locations sequentially on drawing and on the corresponding swipe for that location. Start in areas with the least potential for contamination and proceed to the areas with the greatest potential for contamination. Identify the following:
  • "Hot" spot locations identified with survey meter, i.e., > 0.3 mR/hr;
  • "Use" areas, in addition to "hot" spots (floors, benches, equipment);
  • Storage areas, where material is used,
  • Waste,
  • Material transport areas (to and from storage/use/waste areas),
  • Areas you may have gone before surveying yourself (phone, desk, office, etc.),
  • Entrance to lab (floor), "no-use" areas,
  • Floor, desks, offices within lab, hallways, etc,
  • Telephone, handles (drawers, equipment, faucets, meter knobs, etc.), door knobs.

PERFORMING REMOVABLE CONTAMINATION (SWIPE) SURVEYS

• "Swipe" areas with filter paper, making sure that the number on the swipe corresponds to the numbered location on the drawing, and that the area covered by the swipe is 100 cm² .
• Check suspected "hot" swipes with the survey meter so you can separate them from the rest of the swipes; a periodic check should be conducted of other swipes as well.
• Swipes are now ready for sequential placement in scintillation vials and counting in the LSC or Gamma Counter.
• The results should be analyzed and compared to the Removable Contamination Survey action limits of Table 2.

 

HOW TO MAINTAIN INSTRUMENT CALIBRATIONS