Deformation of zircaloy-4 cladding during a LOCA transient up to 1200 C

Abstract

The high temperature ballooning properties of Zircaloy-4 cladding were evaluated at the simulated loss of coolant accident (LOCA) conditions. Two types of tests were performed. The first one is an isothermal-ballooning test in which a Zircaloy-4 cladding with inner gas pressures between 10 and 60 MPa was ballooned in a high-temperature steam environment. The second one is a transient ballooning test in which an initially pressurized cladding was heated until rupture. Burst elongation and burst temperature were measured after the test. The results showed that the phase transformation between a and β has a great influence on the ballooning behavior in that the a phase acts in a transgranular slip mode and the β phase in intergranular sliding mode. In the case of isothermal ballooning, oxidation has a great effect on the cladding deformation by reducing the burst elongation at high temperature.