We present the development of a grid-to-rod fretting (GTRF) modeling methodology using mortar contact. We leverage a recently-developed computational framework for the modeling of thermomechanical contact in dynamic simulations within the nuclear fuel performance code Bison. Usage of mortar contact ensures a smooth distribution of normal and frictional contact forces, displacements, and velocities on the contact interface, which facilitates an accurate computation of wear. The integration within an advanced nuclear fuel performance code allows for the analysis of complex interactions between fuel, cladding, and spacer grid; including swelling, creep, fuel fragmentation, burnup, plenum pressure, and fission gas release. The methodology is exemplified by the modeling of two spacer grid geometries and the influence of fuel-cladding mechanical contact on the generation of fretting wear.
