Calibration and Validation of a Proportional Counter for Determining Beta Emitters

概要

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Calibration of recently installed proportional counter at the Hot Cells Facility of the Jozef Stefan Institute was performed. Instrument was calibrated for determination of total beta activity, Sr-90 and Pb-210. Detection efficiencies for K-40, Sr-90, Y-90, Pb-210 and Bi-210 were determined, allowing for more accurate determination of the particular nuclide as a single K-40 efficiency. In addition, self-absorption curves for different surface densities for the nuclides mentioned were derived. Two empirical equations for faster and more accurate determination of Sr-90 and Pb-210 were derived. These two equations consider differences in surface density and in-growth of Y-90 and Bi-210, respectively. The detection efficiencies obtained ranged from 10 to 52%, depending on the nuclide, surface density and chemical compositions of the salts used or precipitates obtained following radiochemical separation in the experiment. As a performance test of derived empirical equation for the determination of detection efficiency for Pb-210, specific activity of Pb-210 in IAEA 385 and IAEA 414 intercomparison materials were determined. All procedures and formulae developed include calculation of minimal detectable activities and uncertainty budgets for the determinations concerned.