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Schuler, C; Butterweck, G.; Wernli, C.; Bochud, F.; Valley, J.-F.
Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)2007
Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)2007
AbstractAbstract
[en] A standardised measurement procedure for surface contamination meters (SCM) is presented. The procedure aims at rendering surface contamination measurements to be simply and safely interpretable. Essential for the approach is the introduction and common use of the radionuclide specific quantity 'guideline value' specified in the Swiss Radiation Protection Ordinance as unit for the measurement of surface activity. The according radionuclide specific 'guideline value count rate' can be summarized as verification reference value for a group of radionuclides ('basis guideline value count rate'). The concept can be generalized for SCM of the same type or for SCM of different types using he same principle of detection. A SCM multi source calibration technique is applied for the determination of the instrument efficiency. Four different electron radiation energy regions, four different photon radiation energy regions and an alpha radiation energy region are represented by a set of calibration sources built according to ISO standard 8769-2. A guideline value count rate representing the activity per unit area of a surface contamination of one guideline value can be calculated for any radionuclide using instrument efficiency, radionuclide decay data, contamination source efficiency, guideline value averaging area (100 cm2), and radionuclide specific guideline value. n this way, instrument responses for the evaluation of surface contaminations are obtained for radionuclides without available calibration sources as well as for short-Iived radionuclides, for which the continuous replacement of certified calibration sources can lead to unreasonable costs. SCM verification is based on surface emission rates of reference sources with an active area of 100 cm2. The verification for a given list of radionuclides is based on the radionuclide specific quantity guideline value count rate. Guideline value count rates for groups of radionuclides can be represented within the maximum permissible errors of verification of ± 50% by an average basis guideline value count rate as verification reference. The SCM calibration and verification procedures are illustrated by means of calibration and verification of 17 different products of SCM sensitive for α, β/γ, or α/β/γ radiation. In addition, realistic verification scenarios demonstrate the SCM verification procedure. (author)
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Mar 2007; 88 p; ISSN 1019-0643;
; figs., tabs., refs.

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