Integrated Modeling and Experimental Validation of Residual Stresses in Nuclear Fuel Plates Before and After Reactor Irradiation

The United States High Performance Research Reactor (USHPRR) project is advancing the development and qualification of a low-enriched uranium (LEU) monolithic fuel system for use in high-performance research reactors. This fuel consists of a U-10Mo alloy foil with a zirconium diffusion barrier, clad in Aluminum 6061 via Hot Isostatic Pressing (HIP). A critical aspect of fuel qualification is understanding and predicting residual stresses, which arise during fabrication and irradiation due to mismatched thermal and mechanical properties at material interfaces. These stresses can significantly impact fuel integrity, particularly in terms of delamination resistance and structural stability under operational conditions.

To improve predictive capabilities, this work evaluates three modeling approaches—no creep, time hardening creep, and hyperbolic sine creep—for the aluminum cladding. The hyperbolic sine model, which accounts for temperature-dependent creep behavior, shows strong agreement with experimental data and provides a continuous approximation of creep strain rates. Complementing the modeling efforts, a novel remote slitting system with eddy current sensors has been developed to measure residual stresses in irradiated fuel plates, overcoming the challenges posed by high radioactivity. This system enables stress profile reconstruction using Tikhonov regularization, allowing for discontinuities across interfaces.

Together, these modeling and experimental advancements enhance the understanding of stress evolution in U-10Mo fuel systems, supporting safer and more reliable reactor operation.