Microstructure evolution in Zr1Nb fuel cladding during high-temperature oxidation

Highlights: → Microstructure inside Zr1Nb fuel cladding was observed. → The α-Zr(O) thickness kinetics is slower compared to Zry-4 alloy. → The (α + β)-Zr thickness kinetics is faster than parabolic. → The oxide layer thickness kinetics changes depending on temperature. - Abstract: This work is concerned with the microstructure evolution during high-temperature oxidation inside the cladding wall fabricated of Zr1Nb alloy. The kinetics of the α-Zr(O) growth in the temperature interval of 800-1200 deg. C has been assessed using LM, SEM, and an image analyzer. In addition, the results of nanohardness measurement were used to determine the thickness of the α-Zr(O) layer. Eventually, the experimental results were compared to analytical calculations. Very good agreement has been achieved between experimental and theoretical results, mainly for lower thicknesses. The paper also deals with the kinetics of oxide and (α + β)-Zr layers. The oxide layer growth kinetics changes depending on temperature. The kinetics of the (α + β)-Zr layer is independent of temperature and slightly faster when compared to the parabolic growth.