Uncertainty Quantification Of Fuel Assembly Bow In Pressurized Water Reactor Through a Thermomechanical Simulation

In the core of nuclear reactors, fluid-structure interaction and intense irradiation lead to progressive deformation of fuel assemblies. Detrimental deformation can lead to additional costs, constrained core operation due to longer fuel unloading and reloading operations. Therefore, it is preferable to adopt a fuel management that avoids excessive deformation and interactions between fuel assemblies. However, the prediction of deformation and interactions between fuel assemblies is complex. Uncer-tainties affect neutronics, thermohydraulics and thermomechanics parameters. These are propagated through the coupling of non-linear, nested and multidimensional thermal-hydraulic uncertainties and thermomechanical simulations. This article studies a structural model of the fuel assembly and quantifies its uncertainties. The objective is achieved through a multi-stage approach, beginning with an initial sensitivity analysis to identify the most influential parameters in the mechanical model. The sensitivity analysis aims to build an accurate and suitable surrogate model that represents the mechanical behavior of fuel assembly bowing within the reactor core. This surrogate model is then integrated with the hydraulic model developed in [A. Abboud et al., BEPU 2024, 272] to quantify the final uncertainties in simulating fuel assemblies deformation within a pressurized water reactor.