Standardisation of 89Sr using three different methods

Three independent methods were used to standardise a Sr-89 solution within the frame of an international comparison organised by BIPM/CCRI(II): 4pi liquid scintillation (LS) spectrometry, based on the CIEMAT/NIST efficiency tracing method, and direct activity measurements with a windowless 4pi CsI(Tl)-sandwich spectrometer and a 4pi 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 Sr-89 was found to be 26.21+/-0.08 kBq g(-1). A new half-life value for Sr-89 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. (C) 2002 Elsevier Science Ltd. All rights reserved.