This project will extend the current FES project on additive manufacturing (AM) IN617 by incorporating in-situ monitoring, melt-pool thermal analysis, and multi-scale modeling to generate qualification-relevant insights for nuclear applications. While IN617 is the active FES focus, this project will integrate results from a separate project on AM stainless steel 316 (SS316) for high-temperature gas-cooled (HTGR) and molten-salt reactors (MSR). MSRs operate at ~650–750 °C, while HTGRs operate at ~700–950 °C, creating extreme thermal and chemical environments that demand a deep understanding of process-dependent microstructures and performance. This LBP project will establish a unified framework that transfers knowledge between the two programs, enabling comparative evaluation of thermal behavior, microstructural stability, and high-temperature performance across both alloys. This will be achieved by integrating in-situ thermal data with computational modeling to define reliable processstructure-property-performance relationships under these reactor-relevant conditions. By combining datasets from both IN617 and SS316, the project will identify critical processing windows, defect-formation mechanisms, and microstructural transitions relevant to high-temperature nuclear service. The outcome will be ASTM-aligned qualification guidance that consolidates currently isolated results into a coherent framework capable of informing pre-qualification steps, industry engagement, and future FES activities.