Creep behavior at high temperature of the oxygen stabilized zirconium alpha phase of fuel cladding tubes oxidized in loca conditions

Abstract : During hypothetical Loss-Of-Coolant-Accident (LOCA) scenarii, zirconium alloy fuel cladding tubes are oxidized at high temperature (HT): zirconia and oxygen-stabilized alpha, called alpha(O) are formed on the outer surface of the cladding. To model the behavior of the cladding during LOCA transients, the specific behavior of each layer must be known. This study focuses on the characterization of the viscoplastic behavior of the alpha(O) phase at HT. Model alpha(O) phase specimens enriched by 2 wt% in oxygen were produced from zirconium alloys cladding specimens. Creep tensile tests were performed in the tube axial direction under secondary vacuum between 900 and 1100°C for stresses between 2 and 31 MPa. The creep resistance of the alpha(O) phase is higher than that of the beta phase by three to four decades. The HT creep behavior of oxidized cladding was then modeled by finite element simulation.