Wipe test counter

A wipe test counter is a device used to measure for possible radioactive contamination in a variety of environments. When using radioactive materials it is necessary to test for accidental contamination, whether from use of liquid unsealed sources or to check for leaking sealed sources. A swab or small absorbent smear can be used to “wipe” an area, the wipe is then placed into a test tube and counted, typically using a gamma counter. Testing for leaks in this manner is a method described in the ISO 9978 standard.[1]

Equipment

Survey instruments may be used to detect surface contamination without requiring wiping, however this requires careful calibration and technique to ensure adequate sensitivity is achieved.[2]

A gamma counter is a typical choice for measuring wipe samples for radioactivity as it allows multiple tests to be counted in a largely automated way. These systems detect radiation using a scintillator and photomultiplier tube and may allow the energy spectrum of a sample to be recorded, which can be used to identify the contaminant.[3][4]

Use of a gamma camera has also been proposed, where collimators are removed to improve sensitivity.[5]

Regulation

Wipe testing is typically a requirement of licenses to hold radioactive materials. In the United States the Nuclear Regulatory Commission requires wipe testing of sealed sources "periodically" using equipment sensitive down to 185 Becquerels.[6] In the United Kingdom the Health and Safety Executive guidance for the Ionising Radiations Regulations 1999 requires wipe testing (usually every two years) and it is also likely to be a requirement of Environment Agency permits.[7][8] In Australia licence conditions may require adherence to Australian standard AS2243.4 and ISO 9978 for wipe testing of sealed sources.[9]

References
  1. "ISO 9978:1992 Radiation protection -- Sealed radioactive sources -- Leakage test methods" (PDF). Public.Resource.Org. Retrieved 27 February 2017.
  2. "Information Notice No. NO. 93-30: NRC Requirements for Evaluation of Wipe Test Results; Calibration of Count Rate Survey Instruments". Nuclear Regulatory Commission. 12 April 1993. Retrieved 27 February 2017.
  3. Rayburn, Stephen R (1990). The Foundations of Laboratory Safety a Guide for the Biomedical Laboratory. New York, NY: Springer New York. p. 206. ISBN 9781461233206.
  4. Lombardi, Max H (2006). Radiation Safety in Nuclear Medicine (2nd ed.). Hoboken: CRC Press. p. 129. ISBN 9780849381799.
  5. Friede, Juan; Dumesnil, Cecile; Caron, Camille (1990). "Gamma Camera and Computer-Assisted Wipe Tests: A Simple Method". Journal of Nuclear Medicine Technology. 18 (1): 49–51. ISSN 0091-4916.
  6. "10 CFR 39.35 Leak testing of sealed sources". Nuclear Regulatory Commission. Retrieved 27 February 2017.
  7. Health & Safety Commission (2000). Work with ionising radiation : Ionising Radiations Regulations 1999 approved code of practice and guidance. London: HSE Books. ISBN 9780717617463.
  8. "Sealed sources: how to comply with your EPR RSR environmental permit". Environment Agency. 2011. Retrieved 27 February 2017.
  9. "Wipe Testing of Sealed Sources & Use of Sealed Sources Beyond Recommended Working Life" (PDF). Australian Radiation Protection and Nuclear Safety Agency. February 2013. Retrieved 27 February 2017.
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