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Efficiency calibrations of surface contamination monitors with α/β sources

Calibrations-5.3

Efficiency calibrations of surface contamination monitors with α/β sources of Sr-90, Cl-36, Cs-137, Co-60, C-14 and Am-241 is done with class 1 surface contamination sources of 10 cm x 15 cm (015 CAL BELAC accreditation scope).

The calibration of surface contamination monitors is performed at LNK by comparing the response of the monitor against the surface emission rate of class 1 calibrated sources. The comparison is done for several nuclides that emit β particles with different maximum energies and also for one nuclide that emits α particles (in case of α probes).

While the regulatory documents refer to surface contamination in terms of activity per unit area, the response of monitoring instruments is related directly to the radiation emitted from the surface rather than to the activity contained upon or within the surface.

The calibration of such monitors LNK follows the guidelines of the standard standards below:

  • ISO 8769:2020 "Measurement of radioactivity — Alpha-, beta- and photon emitting radionuclides — Reference measurement standard specifications for the calibration of surface contamination monitors" [1].
  • NPL Good Practice Guide No. 14, The Examination, Testing and Calibration of Portable Radiation Protection Instruments, C J Lee and P H Burgess (Nuvia), Issue 2, revised August 2014 [4].
  • ISO 7503-3:2016 "Measurement of radioactivity — Measurement and evaluation of surface contamination Part 3: Apparatus calibration".
  • IEC 60325:2002 standard “Radiation protection instrumentation – alpha, beta and alpha/beta (beta energy > 60 keV) contamination meters and monitors [2].
  • ISO 7503-1:2016 Measurement of radioactivity - Measurement and evaluation of surface contamination - General principles.
  • ISO 8769:2020 specifies the characteristics of reference sources of radioactive contamination, traceable to national measurement standards, for the calibration of surface contamination monitors.
Figure: Example of surface contamination monitors that can be calibrated at LNK.

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