Standardisation and half-life of Zr.

The nuclide Zr is being tested for the labelling of compounds with long blood circulation times. It decays by beta plus emission (22.8%) and by electron capture (77.2%) to Y. Its half-life has been determined by following the decay rate with two measurement systems; an Ionisation Chamber and an HPGe detector. The combination of six results gives a value of T = 78.333 (38) h, slightly lower than the DDEP recommended value of 78.42 (13) h. This radionuclide has also been standardised by liquid scintillation counting, 4πγ counting and coincidence techniques.