Uncertainty Quantification of Creep Crack Growth Predictions in Irradiated Metallic Components

Metallic components in high-temperature nuclear reactors typically operate in creep regimes where progressive crack growth mechanisms such as creep crack growth tend to be life-limiting. Informed by deformation and failure properties of the material, defect assessment procedures are then employed at the component level to quantify crack growth rates. Aleatoric uncertainty in material properties drives the adoption of bounding intervals in these inputs to ensure conservative assessments. In addition, irradiation effects on mechanical properties used in defect tolerance assessments translate into further uncertainties compared to the case of unirradiated material. The present paper adopts the use of Uncertainty Quantification (UQ) techniques to propagate the variability in underlying material properties used in defect assessments and concomitant irradiation effects on the overall defect assessment outcomes. Quantities of interest include creep ductility, creep rate, yield strength and hardening modulus, failure times and crack size. The particular case of pre-cracked unirradiated and irradiated Nimonic PE16 tie-bar component-type specimens is, here, explored as experimental data in irradiated state are available. The current evaluation to assess creep crack growth while focusing on providing insights on 1-uncertainty of the defect assessment procedure in predicting typically crack growth rate correlations such as a˙-K and a˙-C(t)⬚; 2-model sensitivity to specific material properties; 3- possible use of uncertainty estimates for the definition of failure criterion and inspection intervals.