Integrated Simulations and Applications of Pellet Injection for Tokamak Central Fueling and Management of Transient Events*

Central fueling and management of transient events are critical tokamak research issues. Scoping studies using a new Pellet Ablation Module (PAM), developed based on an analytic ablation expression, and model density and temperature profiles, show that central fueling can be achieved for L-mode reactor plasmas, but would be challenging for H-mode reactor plasmas, as expected. Peak ablation location depends strongly on pellet injection velocity and size and central electron temperature. A PiC-based Shattered Pellet Injection (SPI) model has been developed to mimic the SPI fragment plume and implemented in the 3D MHD code NIMROD. DIII-D and ITER SPI simulations show that MHD mixing plays an important role in the dynamics of the thermal-quench event. NIMROD simulations with constant and temperature-dependent resistivity and thermal conduction show that the ITER baseline scenario is able to achieve full thermal quench with nearly 100% radiation with pure Ne or mixed Ne/D2 SPI. Detailed DIII-D and CFETR central-fueling simulations with self-consistent OMFIT core-pedestal workflows and DIII-D and ITER NIMROD SPI simulations will be presented.