Nuclear Materials and Energy (Sep 2023)
Impact of creep-fatigue interaction on divertor tungsten under high heat flux
Abstract
High heat flux as 20 MW m−2 during stationary operation can be foreseen in future fusion devices, leading to recrystallization and thermal creep in tungsten targets. Both recrystallization and thermal creep impact would play significant roles in service. Strength loss would happen after tungsten has recrystallized. Meanwhile, continuous plastic deformation namely thermal creep occurs and is visible when temperature exceeds the recrystallization temperature (RCT). In this paper, thermo-mechanical analysis of four different analytical models has been performed: stress-relieved tungsten without recrystallization, tungsten with RCT as 1500℃, 1300℃ and 1150℃ separately using finite element method based on ITER-like tungsten divertor monoblock, since the RCT of new developed tungsten base materials and pure tungsten is normally in this range. Low-cycle fatigue lifetime and creep rupture lifetime of these models has been calculated and compared to identify the impact of recrystallization and thermal creep, respectively, under cyclic thermal loads. A linear rule fracture criterion is used to roughly estimate the creep-fatigue interaction impact. The results reveal that low-cycle fatigue lifetime would be decreased to a great extent if recrystallization happens, and the lifetime is shorter for model with lower RCT. Creep rupture life is fairly dependent on the heating duration, and it’s of much concern to estimate divertor tungsten allowable cycles when consider creep-fatigue interaction.
