Application of 3D-DIC in seismic response analysis of graphite core structures

This study introduces and validates the application of the three-dimensional digital image correlation (3D-DIC) technique for the seismic assessment of graphite core structures in horizontal Micro-High-Temperature Gas-cooled Reactors (MHTGRs). Addressing a critical gap in conventional instrumentation, the non-contact 3D-DIC method was employed to capture the full-field vibrational response of individual graphite blocks within a loosely stacked core assembly under simulated seismic excitation. A full-scale reactor core model, comprising 31 discrete graphite blocks, was subjected to multi-axis seismic loading on a six-degree-of-freedom shaking table. The displacement-time histories and frequency-domain responses of each block were simultaneously measured using 3D-DIC and compared directly with data from traditional accelerometers. The 3D-DIC technique effectively eliminated the mass-loading and cable interference artifacts inherent in wired sensor arrays and captured the full field information of the graphite core structures. Comparative analysis in both time and frequency domains demonstrated amplitude correlations within ±10% between the two measurement methods. The results confirm that 3D-DIC provides a robust, high-fidelity, and non-invasive alternative for capturing complex, full-field structural dynamics in modular reactor cores. This work establishes a novel methodological framework for the seismic safety evaluation of advanced reactor designs and offers significant insights for enhancing structural health monitoring protocols in nuclear energy applications, thereby contributing to improved seismic resilience and operational safety of future high-temperature gas-cooled reactors.