Hong-Pyo Lee

Evaluating the seismic performance of safety-related electrical equipment is crucial for limiting severe damage caused by major disasters at nuclear power plants (NPPs). In this study, various electrical components used in multiple Korean NPPs underwent seismic performance tests in accordance with IEEE Std 344, considering the dynamic characteristics of their mounting equipment and the in-cabinet response spectrum (ICRS) at each mounting location. Electrical components demonstrated satisfactory seismic performance and met the acceptance criteria for electrical functions specified in IEEE Std C37.98. Based on the acceleration responses obtained from the seismic performance tests, amplification analysis and amplification factor (AF) calculations were performed using the method specified in NUREG/CR-5203, and the results were compared with the observed response behavior for reference purposes. Evaluation of the AF showed that it was comparable to or conservative relative to the structural response (global mode) of the test specimen but insufficient for adequately accounting for the ICRS (local mode). Results confirmed that nonlinear behavior could occur as the input magnitude increased within the range where the test specimen remained undamaged, and the resulting amplification could decrease. Local mode behavior and impact effects increased the response amplification of the ICRS, particularly in the high-frequency range and in the vertical direction. Accordingly, reinforcement measures that reduce the amplification of vertical and high-frequency components could further enhance the seismic performance of electrical components.

Given the critical role of electrical cabinets in the post-earthquake recovery and emergency response of nuclear power plants (NPPs), a comprehensive assessment of their seismic performance is essential to ensure operational safety. This study analyzed seismic behavior by fabricating an electrical cabinet model based on the dynamic characteristics and field surveys of equipment installed in a Korean-type NPP. A shaking table test with simultaneous tri-axial excitation was conducted, incrementally increasing the seismic motion until damage was observed. A numerical model was then developed based on the experimental results, followed by a seismic response analysis and comparison of results. The findings verified that assuming fixed anchorage conditions in the numerical model may significantly overestimate seismic performance, as it fails to account for the nonlinear behavior of the anchorage system, as well as the superposition between global and local modes caused by cabinet rocking and impact under strong seismic loading. Furthermore, damage and impact at the anchorage amplified acceleration responses, significantly affecting the high-frequency range and the vertical behavior, leading to substantial amplification of the in-cabinet response spectrum.