Liquid scintillation determination of low level components in complex mixtures of radionuclides

A new approach to simultaneous activity measurements of the complex radionuclide mixtures using liquid scintillation counting, which is applicable to the analysis of the environmental and technological samples, is presented. The method is based on specially developed software ‘SpectraDec’, realized on a Windows 95/98/NT platform and a spectra library created for different kinds and levels of quenching. The method allows analysis of complex mixtures when the activity ratios of the individual components vary considerably. For example, the radionuclide concentrations were successfully determined in the following complex mixture: 3H, 63Ni, 90Sr+90Y, 137Cs, 241Am (model mixture), where the 90Sr+90Y/3H activity ratio was 1/2500 (0.2 Bq/500 Bq) and 90Sr, 137Cs, 134Cs, 232Th, 226Ra (IAEA-reference sample), where the 90Sr/137Cs activity ratio was 1/50 (92 Bq/4515 Bq) with an accuracy of about 20%. The limitations of the given approach to the LS analysis of the radionuclide mixtures are considered.