Performing Radiation Safety Surveys

Performing Self-Surveys

Self-surveys are the main tool for demonstrating compliance with the contamination standards on campus. By documenting any known contamination or lack thereof, the lab creates a record to inform future use of a space. This record will also ensure that any residual contamination is cleaned before a room is renovated or decommissioned. Contact Radiation Safety if you need help identifying the proper survey instruments (e.g. liquid scintillation counters (LSC) or hand-held meters).

Using your survey meter

Survey meters are the most efficient tool for finding contamination in the lab, but cannot inform the user if it is fixed or removable. A meter survey allows an individual to survey a larger area than a swipe, but is less sensitive. By ensuring the probe is matched to the type of radiation emitted, a survey meter will allow you to  find contamination levels that would exceed the Radiation Safety Manual limits relatively quickly.

1. Verify that the instrument is in calibration by checking the calibration sticker on the side of your instrument and confirming that the dates reflect a current calibration.

2. Turn on your meter (as well as the audio) and confirm that the batteries are good. Low batteries will give inaccurate readings.

3. Verify that the probe is responding to radiation by placing the probe by a source of radioactivity such as a check source or your stock solution and confirming that it responds. If it does not respond, contact Radiation Safety for assistance.

In general, you should avoid wrapping the detector probe with a mylar, parafilm, or plastic as this will eliminate (or at least significantly reduce) the instrument’s response to low energy beta particles.

Hand-held survey meters will not detect tritium (3H); swipe tests with a Liquid Scintillation Counter are required. Accurate surveying requires you to survey close to an object and to move slowly.

See Radiation Survey Meters for additional information.

Taking Swipes

In order to determine if there is any removable contamination in the lab, swipe (or wipe) surveys are the best tool. These swipes will then be counted in an appropriate radiation detector, usually a liquid scintillation counter (LSC). Swipe tests are the only reliable method of determining 3H contamination without special equipment.

Be sure to use appropriate media (paper filters, cotton swabs, glass fiber filters, etc.) and adequately cover the laboratory. Each swipe should cover at least 100 cm2, which can be accomplished by using medium pressure and drawing an “S” over a 2’x2’ (60cm x 60cm) square. These swipes should then be segregated to prevent cross-contamination between swipes before counting.

Counting Swipes

Swipes should be loaded into an appropriately sized LSC vial. LSC cocktail (counting fluid) will then be added to the vial and then the vials will be placed into LSC racks and counted. Be sure to use a counting protocol that is programmed to detect the radionuclides being used by your lab. A background sample (a clean swipe in cocktail) should be prepared and run along with your swipes. Contamination is considered to be any swipe sample that is found to have a count rate greater than two times the count rate of the background sample.

Addressing Contamination

All contamination outside of the radioactive work area must be cleaned and re-surveyed until the count rate is below two times background. Contamination limits inside radioactive work areas are outlined in the Radiation Safety Manual. Contact Radiation Safety if you are having difficulty with any decontamination efforts or if you have any questions about setting up LSC protocols, counting consumables, or other general questions.

Directions for decontaminating an area can be found under Radiation Emergency Procedures

Areas to Survey in a Lab

At a minimum, your survey needs to cover all radioactive work areas, radioactive storage areas, and areas where contamination is a concern (e.g. break rooms, the desks of common radioisotope users, etc.). Be sure to survey different areas each time to ensure you do not miss contamination in the lab. The number of locations should be based on the type and amount of work since the last survey. These areas should include:

• Floors in front of your work area

• Benchtops and work surfaces

• Non-radioactive trash containers (ensure no radioactivity or visible radiation labels)

• Fume hoods

• Sinks (no sink disposal of any radioactivity)

• Fixed equipment (e.g. hybridization ovens, centrifuges, incubators, LSC, etc.)

• Frequently handled items (e.g. pipettors, glassware, pens, telephones, doorknobs, lab notebooks, keyboards,etc.)

• Refrigerators and freezers

• Radioactive waste storage areas

• Personal protective equipment (e.g. lab coats, safety glasses, reusable gloves, etc.)

• Any area designated as a “clean area”

Self-Survey Guidelines

Use the self-survey form to document findings along with a diagram of the laboratory (available from EH&S Radiation Safety Team (RST) outlining locations of swipes and elevated radiation levels.

The lab's RUA will outline the minimum frequency required for documented surveys, but routine self-surveys are required while working with radioactive materials, as they are the primary tool for detecting contamination and measuring radiation fields.

Survey all rooms involved in the storage or use of radioactive materials, including shared rooms such as cold rooms, equipment rooms, dark rooms, etc. For a complete reference of where to survey or swipe in your lab, refer to Areas to Survey in a Lab

Swipe surveys should always include a copy of the swipe results counted on a Liquid Scintillation Counter (LSC). Document the issues identified, actions taken, and the resolution of any problems (e.g., contamination location, steps taken to clean-up, a final survey showing no contamination, etc.). If you have any questions, contact the Radiation Safety Team at radsafety@berkeley.edu.

NOTE: If you find removable contamination over twice the background on a swipe taken outside of a designated radioactive work area or if you find a radiation exposure reading > 2.0 mR/hr, contact the RST for assistance. Removable contamination found outside of radioactive use areas must be cleaned up immediately. See Radiation Emergency Procedures for further guidance.