Characteristics of liquid scintillation analysis of radon in water

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 ²²⁶Ra and ²²²Rn 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 ²²²Rn content to get a better insight into the stability and behaviour of the samples and ²²⁶Ra interference in samples spiked with ²²⁶Ra with ²²²Rn measurement. ²²⁶Ra interference was more evident in homogenous, one-phase and much lower in two-phase samples. However, one-phase samples offer more accurate indirect ²²⁶Ra measurements. Water-immiscible cocktails (in two-phase samples) have shown a limited capacity for receiving ²²²Rn generated by Ra decay from the aqueous to organic phase when ²²²Rn/²²⁶Ra equilibrium is reached. We have also learned that samples with naturally high ²²²Rn content should not be spiked with ²²⁶Ra 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 ²²⁶Ra activities for spiking to provide more practical answers to questions arising from the demonstrated phenomena.

PSA discriminator influence on (222)Rn efficiency detection in waters by liquid scintillation counting

A procedure for the (222)Rn determination in aqueous samples using liquid scintillation counting (LSC) was evaluated and optimized. Measurements were performed by ultra-low background spectrometer Quantulus 1220™ equipped with PSA (Pulse Shape Analysis) circuit which discriminates alpha/beta spectra. Since calibration procedure is carried out with (226)Ra standard, which has both alpha and beta progenies, it is clear that PSA discriminator has vital importance in order to provide precise spectra separation. Improvement of calibration procedure was done through investigation of PSA discriminator level and, consequentially, the activity of (226)Ra calibration standard influence on (222)Rn efficiency detection. Quench effects on generated spectra i.e. determination of radon efficiency detection were also investigated with quench calibration curve obtained. Radon determination in waters based on modified procedure according to the activity of (226)Ra standard used, dependent on PSA setup, was evaluated with prepared (226)Ra solution samples and drinking water samples with assessment of measurement uncertainty variation included.