Skip to main content
ARS Home » Northeast Area » Docs » Safety, Health and Environmental Training » Radiation Safety » Page 4
Page 4
headline bar
1 - Radiation Safety
2 - Page 2
3 - Page 3
4 - Page 4
5 - Page 5
6 - Page 6
 HOME
Contamination Surveys are required after EVERY use of unsealed radioactive materials - If you don't have time to survey, you don't have time to do your experiment!
 
The following video is a supplement to the training session.

Radiation Survey in Quicktime
RunningTime: 7 minutes


Monthly Surveys

A thorough meter and wipe survey shall be conducted at least monthly in each room authorized by the Radioactive Materials Permit holder, i.e. labs, equipment rooms, environmental chambers, counting rooms, cold rooms, etc. Record all results, positive and negative, on the LABORATORY SURVEY REPORT form.

Monitor with a meter areas where radiation fields are expected to be most intense i.e storage areas, waste containers, etc. Areas most likely to be subject to contamination, such as benches, sinks, floors, waste areas, centrifuges, incubators, refrigerators, freezers, fume hoods, cabinets, etc., shall be monitored with both a meter and a wipe survey. 
Lab room diagram 

A meter survey provides increased assurance that contamination "hot spots" will be detected and, unlike a wipe survey, it can detect fixed contamination. A meter survey alone will not determine if contamination is removable.

On a rotating random basis, include as part of the wipe survey a few frequently used areas where contamination is not expected, such as door knobs, light switches, telephones, etc.. Perform a wipe survey on areas where positive meter results are indicated.

Performing the meter survey

  1. Check the meter for proper operation
    1. Check the batteries using the self-check function of the meter. Replace them if necessary.
    2. Determine that the background count rate is normal (20-50 cpm for GM and 250-350 cpm for LEG). Zero background indicates that the meter is nonfunctional. A high background indicates contamination of the probe or a meter malfunction.
    3. Check detector response by exposing the probe to a radiation source. An intermittent response indicates a damaged probe cable. If no response is observed, the meter is nonfunctional.
    4. Check reproducibility. If the meter is provided with a check source, a notation of the meter/probe response is indicated on the check source calibration label. When checking the reproducibility, the meter reading should be within 10% of the reading noted on the label.

    If found to be nonfunctional, immediately label with an "Out of Service" label (see attached sheet) or other label stating "DO NOT USE! INOPERABLE!", and arrange for calibration services.

  2. Survey all authorized rooms. For maximum sensitivity, hold the probe no more than 1 centimeter from the surface, move the probe slowly, and check for increased count rates.

    Record readings in disintegrations per minute (DPM)/100 cm2 on the survey drawing.

     

  3. Background count rates will vary by perhaps a factor of 2. Consider a reading to exceed background when the count rate exceeds twice the background count rate.

  4. Mark areas of suspected contamination (use a grease pencil, a non-permanent marker, tape, etc.). Include the marked areas when performing the wipe survey.


Return to Top of Page

Wipe Survey

The wipe survey is the most sensitive method for determining the amount of removable contamination. It is the only method for determining whether contamination is removable or fixed. To perform the wipe survey, follow instructions below.

  1. Collect wipe samples 
    1. Use a 2.5 cm paper filter disk. It may be moistened with distilled water, ethanol or "decontamination" solution. A dry filter is acceptable, but less sensitive.
    2. Wipe areas designated by lab's survey system and any area marked during the meter survey.
    3. Wipe some additional non-use areas, including areas of frequent contact, such as door knobs, sink handles, light switches, telephones, etc.
    4. Wipe an area of approximately 100 cm2.
    5. Specify in the record any area(s) wiped which is not indicated on the survey map or legend.

  2. Prepare wipe samples for Radioactivity Counter
    1. Beta emitters
      1. Using tweezers, place filter disk wiped-side up on the bottom of a 20 ml counting vial.
      2. Add 0.5 ml of distilled water.
      3. Add five (5) ml of LSC cocktail.
      4. Mark cap with wipe identification.
      5. Repeat steps (1) - (4) for each sample taken.
      6. Prepare a control sample using a clean filter and following steps (1) - (4). The control provides the background count rate.

    2. Gamma emitters
      1. Using tweezers, place filter disk into a gamma counting vial.
      2. Mark vial with wipe identification.
      3. Repeat steps (1) - (2) for each sample taken.
      4. Prepare a control sample using a clean filter and following steps (1) - (2). The control provides the background count rate.

  3. Count samples. Load wipes in the proper radioactivity counter. Record type of counter used and its efficiency. All wipes should be recorded in disintegrations per minute (DPM) per 100 cm2.

    1. Liquid Scintillation Counter
      1. Set the proper channel perimeters (window settings) for the isotopes in use. This will help identify the isotope for any positive wipe results.
      2. Count the samples, a background sample, and a standard(s) for at least two (2) minutes each.
      3. Results of less than two (2) times background are considered negative. Counts which are greater than or equal to two (2) times background are considered positive.
      4. Recount the sample(s) with positive results for verification. Some positive results could be the result of extraneous luminescence.
      5. Calculate the activity for all positive samples using the equation at the top back side of the attached survey form.

    2. Gamma Counter
      1. Count the samples, a background cample and appropriate standard for gamma emitted being counted. Samples should be counted for at least two (2) minutes each.
      2. Results of less than two (2) times background are considered negative. Counts which are greater than or equal to two (2) times background are considered positive.
      3. Recount the sample(s) with positive results and the background sample for 5 minutes each. Some positive results could be the result of extraneous luminescence.
      4. If the recounted sample counts are ofless than two (2) times background, results are considered negative. Counts that are greater than or equal to two (2) times background are still considered positive. Refer to lab policy for decontamination procedures for areas with positive wipe test results.

  4. Calculate the activities and interpret the results.






<< Previous 1 2 3 [4] 5 6 Next >>