Numerical analysis of flow-induced deflection of curved nuclear reactor fuel plates under high velocity flows

Plate-type fuel elements, widely used in high flux reactor (HFR), may experience collapse or vibration under high coolant flow rates. The study examined the behaviors of curved fuel plates under varying coolant velocities. The deformations of curved plates with varying curvature radii and flat-plate assemblies were computed to facilitate comparison. The fluid domain was simulated using Ansys Fluent, while the solid domain was analyzed using Ansys Mechanical. The study employed a partitioned, two-way, and explicit coupling strategy. The simulation results have shown that the critical velocity for assemblies of curved plates is 20 m/s, whereas for flat plates it is 6 m/s. As the curvature radius or width increases, the plates become increasingly susceptible to collapse. The critical velocity is associated with the nonlinearity between the maximum plate deflections and the square of flow velocities. It also involves plate deflections that extend from the leading edges to the entire length of the fuel at the critical velocity. Under axial flow conditions, the deflection directions of multiple curved plates exhibit regular patterns. The leading edges of the plates adjacent to the walls deflect towards the walls, while the adjacent plates deflect in opposite directions.