Study on the difference of internal flow in reactor coolant pump under high-temperature and high-pressure environment and normal temperature and pressure

•Comprehensive Assessment of Coolant Pump Performance: This study provides a detailed examination of coolant pump performance under extreme high-temperature and high-pressure conditions, with a focus on nuclear reactor applications.•Minor Differences in Characteristic Curves: Despite minor variations in characteristic curves, simulations reveal that the impact of temperature and pressure on maximum head and efficiency is within 4%, suggesting limited global performance differences.•Enhanced Fluid Flow Smoothness: Under extreme conditions, fluid flow within coolant pumps exhibits smoother streamlines and reduced vortex intensity, particularly at lower flow rates, enhancing fluid stability.•Flow State Deterioration at High Flow Rates: At higher flow rates, deviations from optimal conditions disrupt fluid stability, revealing a critical threshold for maintaining efficient pump operation.•Static Pressure Similarity: Static pressure distribution within pump blades remains largely unchanged under extreme conditions, with minor variations observed only at blade tips.•Viscosity Effects in Narrow Gaps and High Flows: While simulations support using clean water as a proxy for boric acid water for global performance metrics, viscosity differences may significantly impact pump performance in specific conditions, necessitating future experimental validation. This study investigates coolant pump performance under high-temp & pressure conditions versus standard, focusing on nuclear reactors. Our comprehensive analysis includes 3D modeling, numerical simulations, and experimental validation. We compared internal flow patterns of coolant pumps using boric acid water vs. clean water. Results show significant changes in pumps’ characteristic curves, head, and efficiency under extreme conditions. Minor differences impact flow phenomena crucially. We observed alterations in streamline smoothness, vortex intensity, and pressure distribution, enhancing our understanding of fluid-pump-environment interactions. This paper offers insights and guidance for optimizing coolant pump design and maintenance in nuclear reactors.