Browsing by Subject "radiostrontium"

Radioactive strontium is a fission product of plutonium and uranium often found in high concentrations in spent nuclear fuel and radioactive waste. Strontium-90 was spread worldwide through nuclear weapons testing in the 1950s and 1960s. Sharing similar properties with calcium, it poses significant health risks when released into the environment, as it can accumulate in bone tissue and teeth, where it continues to radiate surrounding tissues. Therefore, efficient, and rapid monitoring methods for routine analysis of radioactive strontium from nuclear sites and during radiological emergencies are crucial. The aim of this master’s thesis was to validate a strontium-89/90 separation method for the Radiation and Nuclear Safety Authority (STUK) for their routine analysis of emission samples from the Olkiluoto and Loviisa Nuclear Power Plants. Previously, STUK has utilized proportional counting for their strontium analysis. However, this method is time-consuming, involving the ingrowth of the daughter nuclide of strontium-90, yttrium-90, which can take up to 18 days. The strontium determination method used by STUK was modified so the samples could be measured with Hidex 300 SL liquid scintillation counter, equipped with the triple-to-double coincidence ratio (TDCR) liquid scintillation counting technique. Using the liquid scintillation counter makes it theoretically possible to skip the yttrium-90 in-growth phase by measuring strontium-89 immediately after chemical separation using Cherenkov counting, followed by measuring strontium-90 by liquid scintillation counting. At the end of the experimental part of the thesis, considerations for further development of the method included ideas for shortening the sample measurement time, such as increasing the volume of the Cherenkov sample, or the volume of the discharge water used for the analysis. These adjustments would enable faster achievement of the 0.2 Bq/l minimum detectable activity (MDA) and allow for the addition of the scintillation cocktail on the same day, minimizing the growth of yttrium-90. Although the final validation of the method was not completed during this study, STUK gained data and ideas for the continued development of their strontium-89/90 analysis method.