Thermal creep modeling of HT9 steel for fast reactor applications

The ferritic martensitic steel HT9 is a primary candidate material for the fuel cladding of liquid-metal-cooled fast reactors (LMFRs) owing to its excellent stability under irradiation. Thermal creep of fuel cladding is a potential life-limiting factor in the long-life fuel design of LMFRs. Using the measured data available in the literature, such as creep strain data, stress rupture data, and steady-state creep rate data, a generalized creep correlation was developed. The new correlation is based on the Garofalo equation and the modified Monkman-Grant equation, and it shows better agreement with the experimental data than existing correlations that use either the theta projection method or the minimum commitment method, making it more appropriate for use in long-life applications.