Radiochemical determination of strontium-90 in environmental samples by liquid scintillation counting

The quantification of uncertainty in the determination of Sr-90 in environmental samples using liquid scintillation counting for the final radioactivity measurement is covered in this example. The determination of the chemical yield is done by adding a known quantity of strontium to the sample; corrections have to be made for the presence of the stable strontium in the original sample which contribute to the overall uncertainty. From measurements made in different energy windows, the Sr-90 activity is obtained and corrected for the interference caused by the Y-90 daughter isotope. The uncertainty introduced by this approach is discussed in detail. The procedure is applied to the determination of Sr-90 in three IAEA environmental reference materials. Comprehensive sets of tables, including all raw data, intermediate calculations and end results, provide guidance through the radioanalytical procedures. The quantification of uncertainty is extensively documented according to the error propagation method and according to the spreadsheet method. (author)