Filtration performance and hydraulic characteristic analysis on the bottom nozzle in a fuel assembly of a nuclear energy system.

This article focuses on investigating the filtration and flow characteristics of fuel assembly bottom nozzles in nuclear reactors to prevent fuel failure caused by debris-induced wear. Using a newly constructed visualization test facility and a coupled computational fluid dynamics–discrete element method (CFD-DEM) numerical simulation, the study evaluates three different bottom nozzle designs against various debris types and sizes. Results indicate that increased geometric complexity in both bottom nozzles and debris enhances filtration efficiency, with strip-shaped debris tending to align with flow direction, reducing filtration effectiveness. The study also finds that filtration efficiency is more sensitive to debris diameter than length and that flow velocity has minimal impact on filtration performance. These findings provide theoretical and practical insights for optimizing bottom nozzle design to improve debris filtration in nuclear reactor systems.