Modeling and simulations of the dynamic and static D/T retention during DIII-D discharges

We used our ITMC-DYN package to simulate recent DIII-D experiments where W samples with different microstructure and damage rate were irradiated during ten discharges. We developed a new approach for modeling trapping sites accumulation depending on irradiation conditions and sample temperature. We predicted D accumulation during and between discharges and explained the spatial distribution of high-energy traps formation/growth. Carbon accumulated on W surface in DIII-D can affect D behavior in plasma facing materials (PFMs). We compared our modeling of impurity effects with recent results of lab experiments for W and WC.

These simulations explained the different response of pre-damaged W with different grain sizes to D irradiation. We also predicted the effect of limited D surface recombination (due to C) on enhanced D retention in bulk and in voids with increasing irradiation temperatures. Increasing damage level (dpa) causes a transition from preferential D trapping in low-energy traps to more voids/bubbles production and growth. Irradiation conditions and temperature variation during and between discharges is critical for hydrogen isotopes accumulation in PFMs.