Estimation of Strontium-90 Concentrations in Pakistan Using Combination of TBP Solvent Extraction, Precipitation and Cherenkov Counting Methods

90Sr does not exist in nature. Its main sources in the environment are global fallout of past nuclear accidents or nuclear detonations. 90Sr is radiologically significant because of its relatively long physical and biological half-lives and its chemical resemblance to calcium. In order to estimate the radioactivity level of 90Sr around Pakistan Institute of Nuclear Science and Technology (PINSTECH) Islamabad, environmental samples (soil, water, vegetation, and water) and food samples (wheat, milk, poultry) were collected from the different selected sites around PINSTECH within the area of about 12.5 km radius. All samples were pretreated using the guidelines of International Atomic Energy Agency (IAEA) Technical Reports Series No. 295. 90Sr was indirectly determined through its progeny 90Y in secular radioactive equilibrium. 90Y was radiochemically separated using combination of Tri-n-butyl Phosphate (TBP) solvent extraction and precipitation. Finally, the activity was measured on Tri-Carb Liquid Scintillation Counter (LSC) through Cherenkov radiation. The activity concentrations of 90Sr in all samples were too low to be detected by the LSC system, except for a vegetation sample from Rawal Dam where a minimum activity of 0.16 ± 0.04 Bq/kg of fresh weight was found. No considerable activity concentration of 90Sr was found around PINSTECH research facilities.