Oxide layers of Zr–1% Nb under PWR primary circuit conditions

Oxide layers were grown on Zr–1% Nb under conditions simulating those in VVER-type pressurised water reactors (PWRs), viz. in borate solutions in an autoclave at 290°C. The layers were characterised by various methods: their respective thickness values were determined by weight gain measurements, Rutherford backscattering (RBS), nuclear reaction analysis (NRA) and scanning electron microscopy (SEM); the electrical properties were tested by electrochemical impedance spectroscopy. The results show that the oxide layer on Zr–1% Nb is homogeneous and somewhat thicker than that on Zircaloy-4.