Radium Interference During Radon Measurements in Water: Comparison of One- and Two-phase Liquid Scintillation Counting

Assessment of radiation exposure to drinking, surface, and groundwater and of the associated health risks calls for accurate and precise (226)Ra and (222)Rn measurements. One method that fits the bill is liquid scintillation counting (LSC), which allows measurements in one-phase (homogenous) or two-phase samples. The aim of our study was to compare the measurement efficiency with both variations in Niška Banja spa water, known for its elevated (222)Rn content to get a better insight into the stability and behaviour of the samples and (226)Ra interference in samples spiked with (226)Ra with (222)Rn measurement. (226)Ra interference was more evident in homogenous, one-phase and much lower in two-phase samples. However, one-phase samples offer more accurate indirect (226)Ra measurements. Water-immiscible cocktails (in two-phase samples) have shown a limited capacity for receiving (222)Rn generated by Ra decay from the aqueous to organic phase when (222)Rn/(226)Ra equilibrium is reached. We have also learned that samples with naturally high (222)Rn content should not be spiked with (226)Ra activities higher than the ones found in native samples and that calibration of two-phase samples can be rather challenging if measurements span over longer time. Further research would require much lower (226)Ra activities for spiking to provide more practical answers to questions arising from the demonstrated phenomena.