Comparison of two direct LS methods for measuring 222Rn in drinking water using α/β liquid scintillation spectrometry

Towards a radon-in-water primary standard at LNHB

Despite widespread radon-in-water measurements, no primary radon-in-water standards currently exist. This work aims to bridge this gap by developing a system to produce radon-in-water reference materials. The system relies on cryogenic, loss-free transfer of radon, which is standardized through defined solid angle measurements, to a radon standard in water. It allows for preparation of liquid scintillation and gamma-ray spectrometry samples with traceable radon-in-water concentrations. The system's design, functionality, and the results of pilot performance tests are described.

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 RADON ACTIVITY CONCENTRATION IN UNDERGROUND WATER OF BURETI SUB-COUNTY OF KERICHO COUNTY KENYA

The activity concentration of radon in underground water of Bureti sub-county was measured using liquid scintillating counter device. The average radon activity concentration in all the water samples was 12.41 Bql-1. The maximum and minimum activity concentrations of radon were 22.5 and 4.57 Bql-1, respectively. In total, 53% of the total samples analysed had radon concentration levels above the US Environmental Protection Agency-recommended limit of 11.1 Bql-1. The annual dose received by an individual as a result of waterborne radon was determined according to the United Nations Scientific Committee on the Effect of Atomic Radiation reports and was found to be 33.23 𝜇Svy-1. All the samples recorded a value <100 𝜇Svy-1 recommended by the World Health Organization and the European Union council.

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.

Environmentally Friendly Measurement of Airborne Radon Using a Nonvolatile Liquid Scintillation Absorbent

The practicality of using a liquid scintillation method with a nonvolatile liquid scintillation absorbent for the measurement of airborne Rn (radon) in a residence was examined. The relationship between the radioactivity absorbed by the liquid scintillation absorbent and the radon concentration in the air was investigated in a calibrated walk-in radon chamber. The equivalent radioactivity of radon was calculated for Po radioactivity immediately after radioactive equilibrium was attained using successive decay equations via alpha-particle spectrometry based on the 1 h, indirect, selective measurement of the Po alpha-particle spectrum generated after sampling radon. We confirmed that the amounts of radon absorbed in the liquid scintillation absorbent were proportional to the radon concentration in the air. The calibration curve that exhibited reliable quantitative linearity from 500 to 8,000 Bq m in air was extrapolated to the region between 0 and 500 Bq m using the least-squares method with data from 500 to 8,000 Bq m. The validity of the extrapolated curve at less than 500 Bq m was confirmed by comparison of the measured radon concentrations in the room and atmosphere with those determined using an existing ionization chamber. Variations in the absorption of radon were observed due to changes in temperature and humidity. The health and environmental safety of nonvolatile liquid scintillation absorbent was also considered.

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.

Radon in spring waters in the south of Catalonia

Spring waters in the south of Catalonia were analysed to determine the (222)Rn activity in order to be able to establish a correlation between the obtained values with the geology of the area of origin of these samples, and also estimate the potential health risks associated with (222)Rn. Most of the analysed samples (90%) show (222)Rn activities lower than 100Bq/L (exposure limit in water recommended by the World Health Organisation and EU directive 2013/51/EURATOM). However, in some cases, the activity values found for this isotope exceeded those levels and this can be attributed to the geology of the area where the spring waters are located, which is predominantly of granitic characteristics. To verify the origin of the radon present in the analysed samples, the obtained activity values were compared with the activities of its parents ((226)Ra, (238)U and (234)U). Finally, we have calculated the annual effective dose from all the radionuclides measured in spring water samples. The results showed that the higher contribution due to spring water ingestion come from (222)Rn and (226)Ra. The resulting contribution to the annual effective dose due to radon ingestion varies between 10.2 and 765.8 μSv/y, and the total annual effective dose due to his parents, (226)Ra, (234)U and (238)U varies between 0.8 and 21.2 μSv/y so the consumption of these waters does not involve any risks to population due to its natural radioactivity content.

Critical remarks on gross alpha/beta activity analysis in drinking waters: conclusions from a European interlaboratory comparison

The most common gross alpha/beta standard methods used for drinking water analysis are discussed, and sources of interferences are reviewed from a metrological point of view. Our study reveals serious drawbacks of gross methods on the basis of an interlaboratory comparison analyzing commercial mineral water samples with the participation of 71 laboratories. A proposal is made to obtain comparable measurement results using true standardized methods.