Mechanical Properties of Oxidized Zr-1Nb-0.7Sn-0.1Fe Alloy Nuclear Cladding Tubes at High Temperatures

Abstract

The ductility loss and the failure of cladding tubes due to oxidation are considered as a threat to the safety of the nuclear. In this study, oxidation behaviors and the effect of oxide layer on the mechanical properties of Zr-1Nb-0.7Sn-0.1Fe alloy cladding tubes with a lower tin content (<1 wt. %) were investigated. The drastic increase of the oxidation rate at 700oC suggests the change in the nature of the oxide layer with increase of temperature. The acceleration of the oxidation rate for Zr-1Nb-0.7Sn-0.1Fe alloy tubes at 700oC suggests the increased volume fraction of less protective porous oxide, supported by the presence of oxide cracks even before mechanical testing. The ductility increased after oxidation at 600oC, suggesting softening due to recovery and recrystallization is predominant over the ductility loss caused by oxidation. The ductility began to decrease significantly after oxidation at 700oC and cladding tubes exhibited the brittle fracture.