A robust alloy design (RAD) strategy for next-generation (IV) nuclear fission reactors

• Robust Alloy Design Framework: Integrates nuclear criteria and high-throughput thermodynamic simulations in a systematic stepwise approach to design advanced alloys. • Unified Multi-Parametric Score: Combines fuel-clad chemical interaction, neutron absorption, electron configuration, and melting point factor into a single ranking system. • Reactor Selectivity: Enables design of alloys with stable single- or multi-phase microstructures across operating temperatures for diverse reactor types. • Experimental Validation: Alloy V5Fe5Cr5Al identified as top candidate and validated for single-phase microstructure and superior mechanical properties compared to Zircaloy-4. • Scalability and Adaptability: Easily extended to other extreme environments, such as aerospace, through customizable property weighting. Next-generation nuclear reactors demand structural materials capable of withstanding extreme conditions, including high temperatures, intense neutron flux, and corrosive environments. Multi-Principal Element Alloys (MPEAs) have emerged as promising candidates due to their exceptional radiation tolerance, thermal stability, and compositional flexibility. This study introduces a versatile and customizable Robust Alloy Design (RAD) strategy for systematically designing MPEAs for GEN-IV reactor fuel cladding. The RAD framework integrates nuclear-relevant selection criteria, empirical parameter assessments, and high-throughput CALPHAD simulations to efficiently narrow compositional space and identify stable alloys. A unified RAD score developed for the first time, combines key performance metrics, including fuel-clad chemical interaction (FCCI), neutron absorption cross-section (NAC), valence electron configuration (VEC), and melting point factor (MPF), into a flexible ranking system adaptable to reactor-specific priorities. Among 724 candidates, V555(5Al–5Cr–5Fe–85V) emerged as the top alloy, validated experimentally with a homogeneous single-phase BCC microstructure and superior mechanical properties (nano-indentation: 3.389 ± 0.258 GPa; Vickers hardness: 240 ± 6.7 HV), significantly outperforming Zircaloy-4 and V-4Cr-4Ti. Importantly, the RAD strategy is not limited to nuclear applications; its customizable weighting system enables scalability to other extreme environments. This adaptability positions RAD strategy as a versatile tool for advanced materials design across multiple industries.