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

Cherenkov Radiation Detection on a LS Counter for 226Ra Determination in Water and Its Comparison with Other Common Methods

Reliable determination of ²²⁶Ra content in drinking water, surface water and groundwater is required for radiological health-risk assessment of populations and radiation-dose calculations after ingestion and inhalation. This study aimed to determine ²²⁶Ra presence in the untreated water samples on a liquid scintillation counter via Cherenkov radiation detection. Cherenkov counting is a faster, simpler, less expensive technique than other commonly used methods for ²²⁶Ra determination. Step-by-step optimization of this technique on the Quantulus detector is presented in this paper. Improvement of detection limit/efficiency in the presence of sodium salicylate was investigated in this study. The main parameters of the method obtained were detection efficiency 15.87 (24)% and detection limit 0.415 Bq/L achieved for 1000 min of counting in 20 mL of sample volume. When 1 g of sodium salicylate was added, efficiency increased to 38.1 (5)%, with a reduction in the detection limit to 0.248 Bq/L for 500 min of counting. A satisfactory precision level of Cherenkov counting was obtained, the results deviating between 5% and 20% from reference values. The precision and accuracy of the Cherenkov counting technique were compared to liquid scintillation counting (EPA Method 913.0 for radon determination) and gamma spectrometry (the direct method for the untreated water samples on HPGe spectrometer). An overview of the advantages/disadvantages of each technique is elaborated in this paper.

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.

MEASUREMENT OF THE POTENTIAL ALPHA ENERGY CONCENTRATION OF RADON PROGENY BY USING LIQUID SCINTILLATION COUNTING METHOD

For more accurate measurement of the potential alpha energy concentration (PAEC) of radon progeny by the liquid scintillation counting (LSC) method, its counting efficiency was studied in this work. A radon progeny standard source was used to provide different concentrations of radon progeny, and the progeny collected on the sampling filters were measured with a low background liquid scintillation counter. The result showed that the quenching effect could not be ignored, and the counting efficiency was estimated to be 86.12%. The co-comparison experiments showed that the PAECs of radon progeny measured by the LSC methods were in generally consistent with those of other three methods. It indicates that for more accurate measurements of PAEC of radon progeny by using the LSC method, the counting efficiency should be well determined.

Evaluation of different LSC methods for 222Rn determination in waters

Monitoring of ²²²Rn in drinking or surface waters, as well as in groundwater has been performed regularly in connection with geological, hydrogeological and hydrological surveys and health hazard studies. Liquid scintillation counting (LSC) is often preferred analytical method for ²²²Rn measurements in waters as it allows multiple-sample automatic analysis. LSC method implies mixing of water samples with organic scintillation cocktail, which triggers radon diffusion from the aqueous into an organic phase for which it has a much greater affinity, eliminating the possibility of radon emanation in that manner. The main aim of this paper is calibration of the liquid scintillation counter Qunatulus 1220™ for measuring of radon in water and evaluation of two different methods (one-phase and two-phase) in order to obtain the most suitable LSC technique for radon in water measurement. In this study four different scintillation cocktails were tested: one miscible (Ultima Gold AB) and three immiscible (High Efficiency Mineral Oil Scintillator, Opti-Fluor O and Ultima Gold F). Evaluation of presented methods was based on obtained detection efficiency and achieved Minimal Detectable Activity (MDA) values. Comparison of presented methods, accuracy and precision, as well as different scintillation cocktail's performance, was considered from results of measurements of ²²⁶Ra spiked water samples with known activity and environmental samples. LSC results were compared with the results of radon in water measurement obtained by alpha spectrometer RAD7. Calibration was done as a dependence of calibration factor (CF) from Pulse Shape Analysis (PSA). According to the obtained results, with proper adjustment of calibration parameters, both methods could be used for radon in water measurements. The obtained MDA values for all four scintillation cocktails are very low, less than 0.1 Bq l^-1 for measuring time of 300 min.