Coupled experimental/numerical approach to determine the creep behavior of Zr-4 cladding under LOCA condition

Abstract

The thermo-mechanical behavior of Zircaloy-4 fuel rods under Loss-Of-Coolant Accident (LOCA) conditions is investigated. A custom experimental setup is dedicated to the high-temperature creep ballooning study of 90mm long cladding samples. Creep tests were performed under an inert environment (argon), for temperatures from 750 to 850°C and internal pressures ranging from 1 to 5, MPa. As the high-temperature creep of metals is strongly influenced by the temperature, the setup allow for a heterogeneous thermal distribution along the specimen. A unique test provides a rich database about the steady-state creep of the alloy. A first campaign is dedicated to bare Stress Relieved Annealed Zr-4. Creep-rates are computed along a generatrix of the tube using 2-Dimensional Digital Image Correlation (2D-DIC) and are correlated to thermal distribution measurements allowed by Near Infra-Red Thermography (NIRT). As-received Zr-4 behavior laws are determined using Finite Element Model Updating (FEMU). Norton exponents and activation energies are determined for thermal-mechanical conditions of the performed tests.