Baylor > Environmental Health & Safety > Radiation Safety Manual > Section 8: Radiation Surveys

Section 8: Radiation Surveys


A. For Gamma Emitters

  1. Wipe Survey (for highest sensitivity)
    • Use filter papers (about 1 inch in diameter).
    • Smear area approximately 100 square centimeters with each paper.
    • Use enough papers for thorough survey of suspected area.
    • Count samples with a gamma analyzer with sodium iodide crystal, placing sample as close as possible to the detector.
    • If a gamma analyzer is not available, a Geiger tube with scalar may be used although the efficiency is much less than with a gamma analyzer.
    • A liquid scintillation counter can also be used for gamma although the efficiency is lower than a gamma analyzer with a sodium iodide crystal.

  2. Geiger Survey (for rapid information)
    • Use a thin window Geiger survey meter.
    • Indicates presence of contamination only precision is very low.

  3. Deleted 6/19/13 (instrument not available at Baylor University)

B. For Beta Emitters

  1. Wipe Survey (for highest sensitivity a must for carbon-14 and tritium)
    • Use 1 inch filter papers or cotton swabs.
    • Smear an area approximately 100 square centimeters with each paper.
    • Use enough papers for thorough survey of suspected area.
    • Drop each paper into a vial containing liquid scintillation counting solution and count.
    • If a liquid scintillation counter is not available, a windowless flow counter may be used for the filter papers.
    • For high energy betas such as those from phosphorous-32, the samples can be counted with a Geiger counter and scalar. This system is poor for carbon-14 and useless for tritium.

  2. Geiger Survey
    • Use a Geiger counter with thin end window probe.
    • This method is poor for carbon-14 and useless for tritium. Wipe samples must be used to detect tritium. Count in a liquid scintillation counter.

C. For Alpha Emitters

  1. Take smears as for beta surveys and count by liquid scintillation or windowless flow counter.
  2. A Geiger counter with thin end window can detect alpha radiation at close range.

D. Frequency of Surveys

  • A survey shall be made at least once per month where radioactive material is used and more often if conditions warrant.

E. Survey Report Form

  • Results shall be recorded on the form provided by the Radiation Safety Officer and kept available for inspection by the Radiation Safety Officer or state or NRC inspectors. A copy of the survey must be submitted to the Radiation Safety Officer each month. NOTE: All radiation surveys must be documented with the following information:
    • instrument used and its calibration date
    • name of person completing the survey
    • date of survey
    • location of survey
    • survey results

F. Decontamination Requirements

  1. If contamination on a wipe sample of 100cm2 is greater than 3 times background
    • decontaminate the area.
    • resurvey after decontamination to verify the area is clean.
    • record results on a standard survey form and retain for monthly survey records.

  2. If contamination on a wipe sample is greater than 10,000 decays per minute per 100cm2
    • immediate decontamination is required.
    • the Radiation Safety Officer must be notified in writing. The Radiation Safety Officer will provide advice and assistance if required.
    • record results on a standard survey form (also include results after decontamination). Retain for monthly survey records.

  3. Surveys performed by Radiation Safety Officer detecting greater than 2000 dpm/100cm2 will result in immediate oral and written notification to the user.
    • Immediate decontamination is required.
    • Record results of decontamination on the form provided by Radiation Safety Officer. Failure to comply with (1) and (2) above will result in the withholding of all orders for radioactive materials until decontamination has been verified.

G. Decontamination Procedures

  • Decontamination procedures generally fall into two categories: chemical and physical removal.
    1. Chemical
      • Usually can be accomplished by using soap or detergent and water.
      • Dilute acid, base, or other strong cleaning agent may be required.
      • Any solution used in decontamination will be disposed of as liquid waste.
      • Any paper towels, kim wipes, cloth or rags will be disposed of as solid waste.

    2. Physical
      • Removal of the contaminant by chipping, grinding, abrasion, or by covering with tile, paint, etc. (depends on type of emitter and half-life)
      • Care must be exercised to avoid formation of aerosols or dusts.

    3. Decontamination should be continued until a wipe sample taken on the surface indicates no more than 3 times above background.