Determination of hafnium in zirconium and its alloys by stable isotope dilution-neutron activation analysis

A new method, an isotope dilution method combined with neutron activation analysis, has been applied to the determination of traces of hafnium in zirconium and Zircaloys. A known amount of 174Hf-enriched hafnium solution was added to the sample as a spike. The mixture was dissolved and then irradiated in a reactor, together with natural and spike hafnium solutions. After cooling, the spiked hafnium was separated and the γ-ray spectra were measured, together with the natural and spike hafniums. The content of hafnium in the sample was calculated from the measured 175Hf/181Hf count rate ratio. A few parts-per-million of hafnium was determined with a relative standard deviation of 0.93%. The method was used to determine the value of hafnium in zirconium and Zircaloy reference materials, prepared by the National Bureau of Standards (NBS) and the Japan Atomic Energy Research Institute (JAERI). 3 figures, 4 tables