Determination of specific alpha-emitting radionuclides (uranium, plutonium, thorium and polonium) in water using [Ba plus Fe]-coprecipitation method

The indicative dose (ID) is one of the parameters established in the current European directive for water intended for human consumption. To determine the ID, it is necessary to know the activity concentration of: U-238, (234)u, Ra-226, (210)po, (239,240)pu and Am-241. The existing methods to determine these radionuclides involve complex radiochemical separations (ionic exchange columns, extraction chromatography, etch), followed by measurements with a semiconductor detector, laboratory procedures that are time-consuming and costly. As a lower cost alternative that reduces measuring and preparation times, avoids the need for a self-absorption correction and the use of tracers, and above all that can be used in any laboratory, methods based on liquid-liquid extraction and selective co-precipitation were developed. These methodologies offer high separation recovery and selectivity, and the measurements are made using a gas proportional counter or a solid ZnS(Ag) scintillation counter. The separation factor ranged between 91.4% and 100.0% for all alpha-emitting radionuclides across the different methods. The activity concentration for each method was computed through linear equations that represent the relationship between the activity and selectivity of the different alpha-emitting radionuclides. This mathematical procedure simplifies the radiochemical separations and provides more accurate activity concentrations. The results of the internal and external validation studies proved that the proposed method is suitable for determining (241)AM, Ra-226, uranium, plutoniuml thorium and Po-210 in water samples.