APPLICATION OF LIQUID SCINTILLATION COUNTING TECHNIQUE TO THE DETERMINATION OF 90Sr IN MILK SAMPLES

ABSTRACT. The Nuclear and Technological Institute (ITN) has the legal responsibility to carry out the national environ-mental radiological survey. It was planned to provide relevant information on radioactivity levels in different components of the ecosystem (atmospheric, aquatic, and terrestrial environments). For the terrestrial environment, evaluation of the stron-tium-90 (90Sr) concentrations in milk samples was performed. The levels of 90Sr activities have been decreasing since it has been spread to the environment during nuclear atmospheric tests, waste discharges, and power plant accidents. Nevertheless, the measurement of 90Sr is still necessary for radiation protection purposes, because 90Sr has long physical and biological half-lives and could be taken in by man via the food chain. During the environmental radioactivity survey undertaken by ITN/ UPSR, 90Sr was measured in milk samples using classical methods; however, continuous effort was put into developing new analytical methods. Determination of 90Sr on milk samples using a safer technique and a less elaborate procedure was the objective of the studies reported in this paper. A method based on the separation of 90Sr with Sr Resin (Eichrom) was used. The trials were carried out using 1 L of milk and 3 g of resin (20-mL columns). The beta measurements were performed by liquid scintillation counting (LSC) and the 90Sr activity was determined after 90Y ingrowths in the channel region 250–800 keV, under normal counting mode, using a Packard Tri-Carb 3170 TR/SL spectrometer