89,90Sr-determination in various environmental samples by collinear resonance ionization spectroscopy

The application of Collinear Resonance Ionization Spectroscopy for the determination of 89,90Sr contaminations in various environmental samples is presented, demonstrating the versatility of this highly specialized and isotope-selective ultra-trace determination technique. Additionally to these studies we have analysed the different processes, which lead to nonselective ionization and hence cause background. Optimization of the experimental conditions resulted in a significant lowering of the detection limit to a value of 3x106 atoms of 90Sr (corresponding to an activity of 2mBq) in the presence of up to 1017atoms of stable 88Sr. In a parallel measurement trace determination of both isotopes 89Sr and 90Sr is possible with a detection limit for 89Sr of 108atoms. Measurements on different samples, ranging from air filter samples of 1958 up to today, soil, vegetation, milk and human urine samples as well as cooling water from nuclear power plants document the applicability and the specifications of the technique. copyright 1997 American Institute of Physics