Modified 2-window approach for rapid determination of 90Sr and 90Y at low quench level using liquid scintillation counting

Abstract

90Sr is a product of nuclear fission, the radioactivity of which can be determined by liquid scintillation counting (LSC). Because the LSC spectra of 90Sr and its daughter 90Y overlap each other, the following methods are usually used: (1) measuring immediately after 90Sr/90Y separation; (2) waiting to reach radioactive equilibrium; (3) adopting the conventional 2-window approach; and (4) using the spectra deconvolution technique. The first one requires 90Sr/90Y separation and immediate measurement; the second one is time-consuming; the third one is valid only for samples with the same quench level as the calibration standard; the last one is somewhat complicated, and in some cases it is not convenient to export the experimental data to some deconvolution software. Therefore, we have developed a modified 2-window approach to rapidly determine 90Sr and 90Y in either equilibrium or disequilibrium at low quench level. The key modification of the approach is to provide an LSC spectrum of pure 90Y with the same quench level as the sample to be determined. This modification eliminates the need to conduct 90Sr/90Y separation for the sample itself, to prepare the quench curves, and to fit the LSC spectra with some deconvolution software.