The Influence of the air fraction in steam on the growth of the columnar oxide and the adjacent -Zr(O) layer on Zry-4 fuel cladding at 1273 and 1473 K

Negyesi, M.; Amaya, Masaki  

The growth kinetics of the columnar oxide and -Zr(O) layers of Zry-4 under mixed steam-air conditions at temperatures of 1273 and 1473 K were investigated in this study be means of post-test metallographic measurements. The hydrogen uptake was also determined by the inert gas fusion technique. The kinetics of the columnar oxide layer obeyed a parabolic law for all air fractions at both temperatures. The kinetics of -Zr(O) layer appeared to deviate slightly from the parabolic law. The parabolic oxidation rate constant of the columnar oxide increased with increasing air fraction, whereas the parabolic oxidation rate constant of -Zr(O) layer seemed to be independent of the air fraction. Mixed steam-air conditions appeared to enhance hydrogen absorption substantially, especially after the columnar oxide lost its protectiveness.