Crosstalk correction for determination of gross alpha and beta radioactivities in drinking water using a low background scintillation counter

Abstract

BackgroundThere is α-β crosstalk in determination of gross α and β radioactivities in drinking water using a low background scintillation counter, which may lead to erroneous measurement results.PurposeThis study aims to reduce the α-β crosstalk in the determination of gross α and β radioactivities on a low background scintillation counter.MethodsFirst of all, α-β crosstalk correction factors for α (241Am) and β (90Sr-90Y) planar sources were determined on a typical scintillator with low background α/β measuring instrument--BH1227, to ascertain the particles or rays causing the α-β crosstalk. Then, α-β crosstalk correction factors for α and β standard sources with different areas and thicknesses were measured by the BH1227 to explore the relationship between the crosstalk correction factors and the areas and thicknesses of α and β standard sources. The gross α and β radioactivities of drinking water samples with different α or β radioactivity levels were measured and corrected by the BH1227, and the crosstalk correction factors obtained from the α and β standard sources, respectively. Finally, comparisons of the gross α and β radioactivities without and with the crosstalk corrections in drinking water samples were performed to verify the crosstalk correction.ResultsIt is shown that, while pulses arising from alpha particles can get into β channel, the opposite is not typically done. With the increasing of thicknesses of the α standard sources, the α-to-β crosstalk correction factors increase first and then tend to be stable, but have no relation with their areas. The β-to-α crosstalk correction factor for the β standard sources is zero. The correction with the α-to-β crosstalk correction factors obtained from α standard sources, which have the same thickness and area as sample sources, minimizes the α-to-β crosstalk in gross β radioactivity measurement for drinking water samples. The determination of gross α radioactivity in the drinking water samples is not affected by the β-to-α crosstalk.ConclusionsThe pulses caused by β particles or X-γ rays, which can get into α channel lead to erroneous counting, can be effectively rejected by a reasonable increase of α threshold. The α-to-β crosstalk can be effectively reduce with properly adjusting the upper and lower thresholds of β channel to make the α-to-β crosstalk factor as small as possible and performing the α-to-β crosstalk correction on the β count.

Keywords

• low background α and β measuring scintillation counter
• determination of gross α and β radioactivities in drinking water
• crosstalk correction