Numerical modeling development based on seismic test of graphite core in gas-cooled microreactor

An efficient and conservative numerical model was developed and validated to optimize the assessment of the dynamic response of graphite cores in air-cooled microreactors subjected to seismic loading. By designing a 1:1-scale planar test model of the graphite core and conducting sweep, sine wave, and seismic wave tests, we obtain the dynamic characteristics and acceleration response data of the core structure. Based on multi-body dynamics theory, we developed a simplified numerical model incorporating rigid bodies, springs, damping, and gaps to simulate the collision behavior between graphite bricks. The model incorporates equivalent stiffness, brick stiffness, and a damping ratio of 10%, with key parameters calibrated using experimental data. Analysis of harmonic test and simulation revealed mean relative errors of 4-17% at 5 Hz, 15-47% at 7 Hz, and 4-75% at 15 Hz across the tested amplitude range. The acceleration results of the numerical model under seismic conditions exhibit a larger amplitude but can envelope the test response, reflecting a conservative approach. The numerical model's displacement results under seismic conditions show good agreement with the test results. The model successfully captures the dynamic characteristics of the core, such as boundary stiffness sensitivity to frequency and the damping dissipation effect, thereby verifying its engineering applicability. This simplified numerical model can efficiently predict the seismic response of the graphite core, providing a reliable tool for the seismic design of air-cooled microreactors.