Experimentally Validated Multiphysics Modeling of Fracture Induced by Thermal Shocks in Sintered UO2 Pellets

TL;DR

This study combines experimental testing and a validated multiphysics phase-field model to understand and predict fracture behavior in UO2 nuclear fuel pellets caused by thermal shocks, enhancing safety and performance insights.

Contribution

It introduces a validated multiphysics phase-field fracture model that accurately predicts experimental fracture results in UO2 pellets under thermal shock conditions.

Findings

Experimental data confirms model accuracy in fracture prediction.

Thermal gradients significantly influence UO2 pellet fracture behavior.

Model sensitivity analysis identifies key parameters affecting fracture outcomes.

Abstract

Commercial nuclear power plants extensively rely on fission energy from uranium dioxide (UO2) fuel pellets that provide thermal energy; consequently, generating carbon-free power in current generation reactors. UO2 fuel incurs damage and fractures during operation due to large thermal gradients that develop across the fuel pellet during normal operation. The underlying mechanisms by which these processes take place are still poorly understood. This work is a part of our combined experimental and computational effort for quantifying the UO2 fuel fracture behavior induced by thermal shock. In this work, we describe an experimental study performed to understand the fuel fracturing behavior of sintered powder UO2 pellets when exposed to thermal shock conditions, as well as a multiphysics phase-field fracture model which accurately predicts the experimental results. Parametric studies and sensitivity analysis are used to assess uncertainty. Experimental data was collected from multiple experiments by exposing UO2 pellets to high-temperature conditions (900-1200C), which are subsequently quenched in sub-zero water. We exhibit that the fracture results gathered in the experimental setting can be consistently recreated by this work phase-field fracture model, demonstrating a reliable ability to our model in simulating the thermal shock gradients and subsequent fracture mechanics in the primary fuel source for Light-Water Reactors (LWRs). This model advanced the fundamental understanding of thermal shock and property correlations to advance utilization of UO2 as a fuel for nuclear reactors.