Thermal creep analysis and correlation development for manufactured HT9 cladding

HT9 cladding was manufactured through successive cold working and heat treatments, and its creep strains were obtained at various stresses and temperatures in the range of 10–120 MPa and 843–953 K, respectively, for up to 20,000 h. Primary and secondary creep regimes were observed, whereas only a few specimens at extreme conditions experienced a tertiary creep regime and creep rupture. The reference creep models, including the theta projection and modified Garofalo equation for HT9 cladding, did not fit the experimentally obtained creep strain curves; the manufactured HT9 cladding showed higher creep resistance than the reference models. Hence, a new correlation was developed by deriving various constants, such as the activation energy, stress exponent, and material constants, from the measured creep strains. The creep correlation successfully predicted the creep behavior of HT9 cladding manufactured. Obtained extensive creep strains over a range of stresses and temperatures, closely approximate actual operating conditions, and developed correlation in this study are valuable in various applications using HT9, providing essential data for analyzing and estimating creep resistances of cladding during the operation of nuclear reactors.