Pellet injection is a viable technique for fueling burning plasma, triggering MHD activity, and injecting massive materials into the plasma. This talk summarizes our efforts to develop the pellet ablation model and to compare it with the experimental data, especially focusing on the work at the Large Helical Device (Toki, Japan). Pure neon and neon doped hydrogen pellets were injected with high reproducibility, allowing detailed analysis of the pellet penetration depth and the deposition profiles. The physical insight obtained has been incorporated in the INDEX code to predict the material assimilation for future reactor-grade device during disruption mitigation.