Silicon Carbide (SiC) materials used in nuclear reactors can react with steam during severe accidents to generate carbon monoxide (CO) and hydrogen (H2), posing heightened risks to containment integrity. However, the current CFD code for hydrogen safety analysis, CYCAS, lacks a dedicated CO combustion model. This study focuses on developing and validating a comprehensive combustion model for CO/H2/air mixtures to enhance predictive capabilities in nuclear safety assessments. The Turbulent Flame Closure (TFC) model is employed to capture turbulence-flame interactions, while an empirical correlation for laminar burning velocities (LBVs) is derived, incorporating temperature, pressure, and steam dilution effects. This correlation merges LBVs of pure H2 and CO, showing good agreement with experimental datasets across various equivalence ratios. The developed combustion model for CO/H2/air mixtures was then directly integrated into the computational framework of CYCAS. Closed-vessel experiments at 300 K and 1 bar were conducted, demonstrating that the enhanced code accurately predicts temperature and pressure evolutions during combustion. This study contributes to improving containment design and developing effective accident mitigation strategies, thereby advancing nu-clear safety engineering.