Fracture parameter estimation for crack simulation models of spent nuclear fuel cladding with hydrides under pinch load

• A novel method for simulation of SNF cladding failure under pinch load is proposed. • Key parameters of the ductile damage model are identified using statistical methods. • The damage parameters are calibrated by a global optimization using metamodel. • Validation is achieved through comparison with RCT experimental data. It is essential to evaluate the fracture resistance of spent nuclear fuel (SNF) rod cladding under impact loads during transportation. The fracture resistance varies with the radial hydride fraction (RHF), with high RHF significantly reducing resistance to Mode-III failure under pinch load. This study developed a simulation model to evaluate cladding failure resistance under such conditions. A continuum damage mechanics (CDM) were used in the ring compression test (RCT) simulation to analyze the mechanical behavior of cladding with hydrides. However, it is challenging to determine fracture parameters in the damage model due to limited experimental data and variability in hydride morphology. To address this, we propose a framework to estimate fracture parameters using an image-based finite element model. A metamodeling technique was introduced to overcome the high computational cost of direct simulation-based optimization. A dataset was constructed via design of experiments (DoE), and the effects of parameters were analyzed through analysis of variance (ANOVA). The fracture parameters were then calibrated using a Kriging metamodel by minimizing the error between simulated and experimental load–displacement curves. The optimized parameters successfully predicted the crack initiation load and displacement with errors less than 2%. Unlike previous approaches that rely solely on global indicators such as strain energy density (SED), the proposed methodology incorporates microstructural features and enables the consideration of variability in failure criteria arising from hydride morphology. This framework provides powerful tools for understanding cladding failure under pinch load.