Determination of 222Rn and 226Ra in aqueous samples using a low-level liquid scintillation counter

A method for measuring 222Rn and 226Ra in aqueous samples has been studied. The technique uses low-level liquid scintillation counting from vials containing an insoluble high efficiency mineral oil scintillation cocktail. A Wallac 1220TM Quantulus LS counter was used for all the experiments. The optimum pulse-shape discrimination value was evaluated by using the minimum detectable activity criterion for each condition of measurement. Experiments on the optimum volume and sample-cocktail ratio, the influence of shaking, type of vial and diffusion of radon from vials were carried out. The study was applied to the determination of very low levels of 222Rn and 226Ra from aqueous environmental samples. The results reached using this method were very satisfactory and even better than from other more laborious procedures.