Radiation Safety Training Survey Meter Use Washington State University Radiation Safety Office

1. Radiation Safety TrainingSurvey Meter UseWashington State UniversityRadiation Safety Office

2. What is a Survey Meter? • A survey meter is a portable handheld, electronic instrument used to detect radiation, often called a “Geiger counter”.

3. Choosing a Survey Meter • Portable survey instruments can be very useful in aiding workers in locating radioactive contamination. However, the type of detector (or probe) must be chosen according to the kind of radioactive material that is being used.

4. Choosing a Survey Meter(cont.) • Generally, thin window Geiger-Mueller (GM) probes are best suited to detect beta radiation with energies above 70 keV • while sodium iodide (NaI) scintillators are best for gamma radiation. 

5. Choosing a Survey Meter(cont.) Ensure that the probe you are using is capable of detecting the isotope you are using. If you are unsure, consult with the manufacturer, your Authorized User or the Radiation Safety Office.

6. Know Your Meter! • Unless you know exactly what you are measuring and understand the limitations of detection instruments, it is possible to draw misleading conclusions from your readings.

7. Know Your Meter! Here is one example. • The radiation from some isotopes can cause a Geiger-Mueller (GM) tube to overexcite and indicate a higher level of radiation than is actually present. Americium 241 is an example of this phenomenon.

8. Know Your Meter! Read the meter's operating manual to gain familiarity with the controls and operating characteristics of your meter.

9. Meter Parts. • The detector or probe is the device which produces electrical signals when exposed to radiation. It usually has a window through which radiation can penetrate its cavity.

10. Meter Parts. (Cont.) • The dial or readout is the gauge which indicates the amount of radiation exposure present. It often has two scales, mR/hr and/or CPM. The selector switch is a switch to turn the meter on-off, check the meter batteries, and/or select a scale multiplier.

11. Meter Parts. (Cont.) • The reset button allows the meter reading to be zeroed. When the level of radiation or the number of counts exceeds the highest reading at a particular scale multiplier, switch the scale multiplier to a higher range and push the reset button. This causes the readout needle to reset to zero so the user can accurately determine the count rate.

12. Meter Parts. (Cont.) • The response button adjusts the response time of the meter. When this switch is on “F” the meter will have a faster response but, the meter readings will be less stable. For routine work set the response button to the slow mode “S”.

13. Meter Parts. (Cont.) • The speaker is an audible device connected to the radiation monitor. It may be located outside or inside the meter and may have its own battery. The speaker is in-line with the detector so each count produces an audible click on the speaker.

14. Listen! • Always use the instrument's audible response while conducting surveys. The audible response is much faster than the meter indication. While scanning areas, listen to the "clicks" of the instrument rather than relying on meter deflection. What you are listening for is any increase in the rate of "clicks" above normal background levels. When you note any increases, stop and scan that area more thoroughly. Any sustained increase above background levels should be investigated.

15. Survey meter use. • 1) Check the meter for any physical damage. Check the cord for damage or wear. Make sure the probe window has not been punctured.

16. Survey meter use. • 2) Before using your meter, check the calibration sticker. Most meters are calibrated once a year. Be sure your meter is in calibration. If it is not, do not use it and contact the Radiation Safety Office.

17. Survey meter use. • 3) Perform a battery check. This is performed differently on different meters. So please become familiar with your meter. Turn the selector switch to BATT position. The needle must be within BATT OK range. If not, the batteries are weak and must be replaced.

18. Survey meter use. 4) Check the background radiation levels. Remember there is always background radiation. Record the background reading in the Survey Meter Quality Assurance Notebook.

19. Survey meter use. • 5) Check your meters response to a known radiation source. This meter has an attached check source. If yours does not, use the source in the meter notebook.

20. Survey meter use. Every survey meter should have a “Survey Meter Quality Assurance Notebook”. Be sure the cover page of your note book is filled in properly. Fill in meter manufacturer and serial number. Fill in probe model number and serial number. Ludlum 3 111111111 44-9 22222222 Fill in Meter storage location. Fill in Authorized User or Equipment Coordinator’s name and contact phone number and the same for an alternate contact. Fulmer 123 Arthur Dent 555-4242 Ford Prefect 555-5883

21. Survey meter use. This is the Response Check Source page in the notebook. Place the meter probe over the check source to get the check source reading. Record this reading on the next page of the notebook.

22. Survey meter use. Ludlum 3 1111111111 44-9 222222222 450 Be sure the information has been filled in on this page. Meter and serial number. Probe and serial number. The Expected response to check source, should have been filled in by the Radiation Safety Office. 1/1/11 Dr. Who 50 450 Verify the calibration status of the meter. Record the background reading and the response check reading. Record the date and your name. The meter is now ready to be used for the radiation safety survey.

23. Use of Survey Meter review. Check for Calibration Sticker Check battery Check background radiation Check meter response to a known radiation source. Record the check source results and background readings in the meter notebook. Survey meter use.

24. Start the Survey. • The detector's "window" (probe) should be held as close as possible (within about 1 cm (1/2 ")) to the surface being measured. Use extreme care to avoid actually touching surfaces and spreading radioactive contamination to the detector. Remove plastic coverings, if present, from the detector window as this will effectively shield out lower energy radiations and preclude their detection.

25. The Survey (Cont.) • Scan surfaces slowly enough to detect the presence of low levels of radioactive contamination. Typically, the rate of detector movement should not exceed about 1" to 2" per second.

26. The Survey (Cont.) • Ensure that you select the proper scale on the instrument for conducting the survey. Whenever scanning surfaces for radioactive contamination, always use the lowest scale (i.e., x0.1 or x1 scale) available. Select higher range scales as necessary to obtain maximum readings if contamination or other measurable radiation is detected.

27. The Survey (Cont.) Be sure to survey all areas of the lab. That have to potential for radioactive contamination and other areas that you might not think are contaminated. Such as Telephones, door knobs, and lab coat sleeves. Always survey the bench tops, floors, and equipment used in the experiment. Everyone uses survey meters.

28. Test Time! • Follow this link to the test. https://myresearch.wsu.edu • Use your WSU user name and password to sign in. • Click on the training tab. • Then click on the available training tab • Find the radiation safety training Survey Meters course, in the “OR” section, click on it and take the test.