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Radiation Safety Manual


Appendix


 

Radiation Safety Manual for Laboratory Users

SECTION 5: Surveys and Contamination Control

Frequent surveys performed by knowledgeable laboratory personnel are the main line of defense to detect spills and to prevent the spread of contamination within and beyond the laboratory. This section summarizes the requirements for performing surveys. See Appendix A for detailed information about the types of contamination surveys, how to use a survey meter, how to perform a survey using a survey meter and how to perform a wipe test.

Survey Instrumentation (top)

Table 5.1 summarizes the instrumentation and method of choice for the isotopes most commonly used at Princeton University.

Performing a Meter Survey (top)

Appendix A provides detailed instructions on the use of a survey meter and how to perform a survey. The following list is a brief survey checklist:

  • Perform a battery test
  • Perform an operational check the first time you use the meter each day
  • Check meter background. Meter background should be < 100 counts per minute (cpm) for a G-M meter and < 300 cpm for a sodium iodide (NaI) scintillation meter.
  • Perform the survey
  • Decontaminate or label contaminated areas and items.
  • Document survey results in your personal survey log or in the lab survey log.

Defining Contamination (top)

If an item or area with a sustained count rate of three times background or more is found, the item or area should be considered to be contaminated.

When to Survey (top)

Laboratory personnel must conduct individual work area surveys (surveys of floors, workbenches, handles, experimental equipment, etc.) and personal surveys (surveys of one’s person and clothing) under the following conditions:

  • at the end of an experimental procedure
  • at the end of each day for multi-day procedures;
  • frequently during the manipulation of millicurie quantities of open sources;
  • following the opening of radioactive material packages;
  • following withdrawals from stock vials containing more than 1 mCi;
  • prior to exiting the laboratory (for personal surveys)

Where to Survey (top)

Survey areas where splashes or spills may have occurred and areas where a person could unknowingly transfer contamination. Typical survey locations include:

  • Bench tops, including the edges
  • Fume hoods (aprons, sashes, sash handles)
  • Beta shields
  • Refrigerator and freezer door handles
  • Sinks designated for radioactive material disposal (sink basin, surrounding bench, faucet handles)
  • Floors: at working areas, laboratory entrances, waste containers, fume hoods
  • Communal equipment, such as pipettors, timers, incubators, centrifuges, water baths, etc.
  • Non-radioactive trash (to ensure that contaminated waste is not disposed of as regular trash)
  • Clean areas (offices, desks, doorknobs, phones, computers)

When to Document Surveys (top)

Document the survey results:

  • when radioactivity in amounts of 250 µCi or more have been handled,
  • whenever contamination is discovered, regardless of the amount used, and
  • to show follow-up actions, whenever contamination has been cleaned up.

How to Document Surveys (top)

Record survey results in a personal survey log or in the laboratory survey log. Appendix A contains a copy of a blank survey log page. Each log entry should contain the following information:

  • Name of person performing the survey
  • Date of survey
  • Brief description of the area surveyed
  • Survey meter results (in cpm), even for background count rates
  • Meter identification (model, serial number)
  • Follow-up action taken when contamination is found.

When to Report Contamination (top)

  • Skin contamination, regardless of level of contamination, must always be immediately reported to EHS.
  • Uncontained spills (e.g., spills outside of contained areas on the work bench or hood) in excess of 10 µCi must be promptly reported to EHS.
  • Widespread contamination in any amount should be promptly reported to EHS. Contamination is considered to be widespread if it is found in several locations which are not normally expected to be contaminated (e.g., on floors and handles, in non-radioisotope areas, etc.).

Purchase, Repair and Calibration of Survey Meters (top)

Call EHS for recommendations and information about purchasing a radiation survey meter. After a new meter arrives, call EHS to register the meter. Every survey meter must have a check source attached to it. Check sources are available from EHS.

EHS performs a periodic electronic calibration of laboratory survey meters. Meters must be calibrated at least annually.

Call EHS whenever a survey meter is not functioning properly or needs to be repaired for any reason. EHS maintains repair and calibration records for each survey meter and can offer limited diagnostic and repair services.

Table 5.1

Survey Instrumentation Guide

Radioisotope Acceptable Survey Method Comments
H-3 LSC There are no other acceptable survey methods
C-14 G-M or LSC LSC is most sensitive; G-M detects moderate to high levels of contamination; do not cover G-M with parafilm
P-32 G-M or LSC G-M detects low levels of contamination
P-33 G-M or LSC LSC is most sensitive; G-M detects moderate to high levels of contamination; do not cover G-M with parafilm
S-35 G-M or LSC LSC is most sensitive; G-M detects moderate to high levels of contamination; do not cover G-M with parafilm.
Cr-51 NaI, g, or LSC  
Zn-65 G-M or g  
I-125 NaI, g, or LSC  
U-238 G-M or LSC  

Table Key:
G-M = Survey meter with a Geiger-Muller detector
LSC = liquid scintillation counting
NaI = survey meter with a thin crystal sodium iodide detector
g = gamma counter



       
       
     

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