Liquid Scintillation Screening Method For Isotopic Uranium in Drinking Water

The radiation dose resulting from the ingestion of uranium is determined by activity rather than mass; isotopes such as can contribute significantly to the total uranium activity, without being detected by mass-based fluorometric techniques. As 2U I 238U ratios signif i-cantly in excess of 1 are frequently noted in groundwater, the determination of uranium on a mass basis and the assumption of isotopic equilibrium can lead to serious dose underestima-tion. Techniques for specific uranium isotope determination are well developed, but involve considerably more effort than fluorimetry. The relative ease with which uranium can be extracted from water into a liquid scintillation compatible solution provides an alternative approach for screening drinking water supplies. A technique originally developed for PERALS (Photon, Electron Rejecting Alpha Liquid Scintillation) systems has been modified for use in conventional LS systems as a screening test for isotopic uranium and other actinides in drinking water. While lacking the degree of alphaibeta discrimination and energy resolution available with PERALS systems, conventional units offer the advantages of large sample volume, high throughput, and widespread availability. This chapter demonstrates that with appropriate sample preparation, the resolution and background attainable with conventional systems is more than adequate to provide a simple, effective screening technique for uranium concentrations of significance to public health