Standardisation of 89Sr using three different methods

Three independent methods were used to standardise a 89Sr solution within the frame of an international comparison organised by BIPM/CCRI(II): 4π liquid scintillation (LS) spectrometry, based on the CIEMAT/NIST efficiency tracing method, and direct activity measurements with a windowless 4π CsI(Tl)-sandwich spectrometer and a 4π pressurised gas proportional counter. Quantitative solid point-like sources were prepared paying special attention during the source drying phase. The impurities in the original solution were measured and corrected for in the results of all three methods. The activity concentration of 89Sr was found to be 26.21±0.08 kBq g−1. A new half-life value for 89Sr of 50.61±0.05 days was determined from the LS measurements. The measurement methods, including the impurity measurements, are described and the results compared, considering the advantages and disadvantages of each method.