Predicting Mechanical Instability of a Cylindrical Plate under Axial Flow Conditions

Five U.S. high performance research reactors (HPRRs) are currently part of an international non-proliferation program with the objective of ultimately converting their highly enriched uranium (HEU) fuel to a new high density, low enriched uranium (LEU) fuel while still maintaining their reactor kinetic and thermal hydraulic performance. A uranium-molybdenum (U-Mo) alloy is under development as the proposed LEU fuel. This prototypic fuel must be qualified through the relevant regulator (either the Department of Energy (DoE) or Nuclear Regulatory Commission (NRC)) prior to its implementation in the HPRRs. One particular aspect of this qualification being investigated is the hydro-mechanical integrity of the fuel elements during typical operation conditions; with emphasis on coolant-clad reactions. Due to the highly turbulent flow conditions which produce extreme viscous forces over the plate type fuel elements found in the HPRRs, interfacial reactions regarding the prototypic fuel are of concern for the fuel's qualification. One issue associated with coolant-clad interactions is the onset mechanical fuel plate instability induced by the flow field. This phenomenon has the potential to induce sufficient plate membrane stresses to challenge the hydro- and thermo-mechanical integrity of the elements. In this study, a flow induced vibration model is developed to characterize elastic plate motion of a single HPRR fuel plate in an attempt to address plate instability concerns associated with HPRR elements.