Seismic analysis of the KSTAR tokamak

The objectives of this analysis are to investigate the structural integrity of the KSTAR (Korea Superconducting Tokamak Advanced Research) device for the design earthquake and to enhance its aseismic performance. Three-dimensional finite element beam-shell models of the vacuum vessel, cryostat, and pumping ducts were developed and spectrum analyses based on the floor response spectra for the KSTAR building were carried out separately for each finite element model. Natural frequencies, seismic displacements and stress intensities were determined and effective seismic accelerations for the static analysis were also calculated by using the reaction forces at the fixed points. From a comparative study on the two kinds of seismic analyses (spectrum and static), equivalent static earthquake loads were verified for the detailed structural analysis. The results reveal that effective seismic accelerations in the horizontal direction are three times greater than the peak ground acceleration (PGA) and those in the vertical direction are less than two times of PGA. It can also be shown that the maximum stress intensities are less than 20% of the allowable stress limit specified in the ASME Boiler and Pressure Vessel Code.