Thermal gradient effect on the helium and intrinsic defects transport properties in Tungsten

Plasma-facing materials (PFMs) in a fusion reactor are expected to withstand stringent conditions, with high heat and particle fluxes,which will create strong gradients of temperature and concentration. Helium ash, hydrogenic species and neutron-created point defects will migrate in the presence of the afore-mentioned gradients. In this work, we use nonequilibrium molecular dynamics simulations to study the transport properties of He, and self-interstitial atoms in the presence of thermal gradients in tungsten. We observe that in both cases, the defects and impurity atoms tend to migrate toward the hot regions of the material. The resulting concentration profiles are in agreement with the predictions of irreversible thermodynamics. We demonstrate that, when the mass-heat transport coupling is considered, the resulting steady-state profiles vary significantly from those when species transport is decoupled from heat transport.