A STUDY ON THE SEISMIC ANALYSIS METHOD FOR INTERFACE PIPING SYSTEM MULTI-SUPPORTED BETWEEN BASE-ISOLATED BUILDING AND NON-ISOLATED BUILDING

摘要

A study on the application of seismic isolation system has been widely researched in order to increase the seismic safety of SSCs (Structures, Systems, and Components) for nuclear power plant (NPP). In the design of base isolated NPPs, the seismic analysis of interface piping system multi-supported between base-isolated building and non-isolated building is one of the key issues. The main steam supply piping connected to the high pressure (HP) turbine of APR1400 (1400 MW-class advanced nuclear power plant in Korea) is a typical example of interface piping system multi-supported between base-isolated building and non-isolated building, and it is routed from the Containment building (base-isolated building) to the Turbine building (non-isolated building) via the Main Steam Isolation Valve House in the Auxiliary building (base-isolated building). In the seismic analysis of this piping system based on seismic inputs developed from the study for application of base isolation system to APR1400, using the Enveloped Response Spectrum (ERS) method, a commonly used methodology for seismic analysis of piping systems in the nuclear industry, generates overly conservative analysis results. This paper performs parametric research on combination effects of responses between support groups, damping effects and modal combination method with close modes in applying the Multiple Input Response Spectrum (Independent Support Motion : ISM) method to the analysis model of the main steam interface piping. Quantitative assessment and comparison with the analysis results of the ERS method and Time History Method (THM) are also carried out. As a result, it is shown that the analysis results of the ISM method together with the SRSS combination between support groups, 4% damping with ±15% spectrum peak broadening and modal response combination methods considering the contribution of closely spaced modes are remarkably similar to those of THM.