Method for determining 226Ra in water via liquid scintillation counting and its uncertainty evaluation

An analytical method was developed for the rapid determination of 226Ra in water through liquid scintillation counting. The separation and purification of 226Ra from water were performed by co-precipitation using barium sulfate as the carrier; the direct measurement of 226Ra was realized by using a liquid scintillation spectrometer. Through sample analysis, a mathematical model for uncertainty evaluation was established and the sources of uncertainty were analyzed. The results showed that the overall counting efficiency of 226Ra is 91.3%-98.5%, the detection limit is 0.01 Bq/L, and the relative extended uncertainty is 7% (k=2), indicating that the proposed method is suitable for the rapid analysis of 226Ra in drinking water. The uncertainty of the method for the determination of 226Ra in water is mainly caused by the errors of sample counting rate and overall counting efficiency.