A Comprehensive Study of AA 6061 Thermal Creep Models and their Effect on Residual Stress Predictions in Irradiated U-10Mo Fuel Plates

The United States High Performance Research Reactor (USHPRR) project is developing a plate-type nuclear fuel that utilizes uranium and molybdenum (U-10Mo) monolithic fuel and Aluminum Alloy 6061 (AA 6061) cladding which will be qualified for use in High Performance Research Reactors (HPRRs). As part of the qualification process, the fuel system must be shown to have stable and predictable behavior while maintaining structural integrity during normal operational conditions. Residual stress is a key parameter used when evaluating fuel system simulations for indications of geometric instability and structural degradation. Recently, efforts have been made to increase the accuracy of residual stress calculations in the fuel system by leveraging the sensitivity of these calculations to the AA 6061 creep formulation. Previously, these efforts focused on the residual stress developed during the fabrication process of the fuel plates. However, the residual stress development during irradiation is imperative for understanding the overall fuel performance in the reactor during irradiation. This work compares three separate simulations that include no AA 6061 creep model, a time hardening creep model, and a hyperbolic sine creep model to analyze the differences in residual stress calculations and determine the most accurate configuration of models.