Calibration and Validation of a Proportional Counter for Determining Beta Emitters

Abstract

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.