Oxygen diffusion in β-Zircaloy

Abstract

The diffusion of oxygen in β-Zircaloy-4 has been studied from 900 to 1500°C with survey measurements for β-zirconium and β-Zircaloy-2. The tracer diffusivity was measured over the entire temperature range and the chemical diffusivity from 1100 to 1450°C. The experiments were performed by using oxygen-18 as the tracer and activating it by proton bombardment. Some complementary measurements were made using Auger Electron Spectroscopy. The results indicated that the tracer and chemical diffusivity of oxygen in β-Zircaloy-4 are statistically identical, and that there is no oxygen concentration dependence over the oxygen concentration range studied, 0.1 to 0.6 wt.%. The temperature dependence of the diffusivity of 18O from 1000 to 1500°C is given by D = 2.48 × 10 −2 exp(−28200/ RT) cm 2/sec. The results for the β-zirconium and β-Zircaloy-2 indicated that the compositional differences between the three host materials exert no influence upon the oxygen diffusivity. An examination of the activation entropy, calculated assuming that Snoek's model describes the diffusion process, indicates that this model probably is not appropriate.