This study investigates the seismic performance of reinforced concrete shear walls in nuclear power plants using high-strength reinforcing bar through finite element (FE) modeling and probabilistic fragility analysis. High-strength reinforcing bar is increasingly considered for nuclear structures to mitigate reinforcement congestion and improve constructability while maintaining structural integrity. Using experimental data, FE models were developed and validated to accurately capture shear and flexural failure behaviors. Seismic fragility curves were derived based on probabilistic evaluations under various ground motion intensities. The results indicate that shear walls reinforced with Grade 550 MPa and reduced reinforcement ratios exhibit equivalent seismic performance to identically detailed walls except for reinforcing bar grade (Grade 420 MPa). Additionally, a case study on a nuclear containment structure estimates a potential reduction of up to 325 tons of reinforcing bar. These findings highlight the feasibility of applying high-strength reinforcing bars in nuclear structures while ensuring seismic resilience and optimizing construction efficiency.