Activity standardization by liquid scintillation counting and half-life measurements of 90Y

Radioactive 90Y was standardized by means of 4πβ liquid scintillation efficiency tracing with a two-phototube counting system. The efficiencies of 90Y and the tracer 3H are related by the CIEMAT/NIST method. The dependence of the calculated efficiency on various shape factors and the importance of accurately measuring the radionuclide impurity of 90Sr are discussed. The half-life of 90Y was measured with improved accuracy by means of a liquid scintillation counting and a 4π ionization chamber measuring system, and an average value T1/2=64.053(20) h was found.