Impact of Circumferential Fabrication Deviations in Research Reactor Fuel Assemblies on the Thermal Behaviors of Fuel Meat

A computational study wa s conducted using STAR-CCM+ to analyze the temperature distribution in the fuel meat of the Tsinghua High Flux Reactor (THFR), focusing on cases with circumferential fabrication deviations. The results indicate that even under the most severe misalignment, where the fuel meat edge aligns with the side plate surface, no localized hotspots form at the fuel meat corners under a uniform circumferential power distribution. For nonuniform power distributions, the coolant–fuel meat temperature rise ratio between the corner regions and adjacent areas never exceeds the corresponding power density ratio. In all cases, the maximum temperature occurs in the central region of the fuel meat.Thermal property sensitivity analysis identified side plate thermal conductivity as the dominant factor influencing potential corner hotspot formation. For conventional metallic side plate materials and a uniform circumferential power distribution, corner hotspots are not expected. This stability arises from two factors: (1) the coolant channel boundary layer thickness is approximately 0.15 mm, minimizing low-velocity flow regions and (2) convective heat transfer constitutes the majority of total thermal resistance. Heat generated in the corner regions effectively conducts through the side plates into the coolant, preventing hotspot development.These results offer practical guidance for nuclear core design and fuel manufacturing optimization. The broad parameter space considered in the sensitivity analysis ensures the approach is widely applicable, making the conclusions relevant to a variety of research reactor fuel assembly configurations.