Reanalysis of the floor response spectra of the Ignalina Nuclear Power Plant Reactor Building

Abstract

The purpose of this paper is re-evaluation of the floor response spectra of the reactor building of Ignalina Nuclear Power Plant (NPP), Lithuania. The operation of reactor was stopped at the end of 2009; however, the removal of the nuclear waste takes a long time. The seismic evaluation of the Nuclear Power Plant Reactor Building is important in assessment of the reactor safety. The safe operation of the NPP is important not only during the reactor operation, but also when it is stopped. The building of the reactor should satisfy the safety requirements during maintenance of the building until final utilization of the nuclear fuel and equipment. The seismic analysis of Ignalina NPP are performed to evaluate the level of seismic potential in the structures with respect to new data and recent knowledge.The seismic input is evaluated on basis of the seismotectonic data and seismic properties of soil of the Ignalina NPP site. The dynamic finite element analysis of the reactor building was conducted in two stages. The soil-structure interaction analysis was carried out in order to assess the effects of the soil on the input spectra by applying two quasi two-dimensional coupled soil-structure finite element models. A detailed three-dimensional model of the building structure was developed for the fixed base dynamic analysis. The floor response spectra were obtained at the specified levels and specified points of the building. The influence of 3D effects and specific properties of the building structure are comprehensively discussed.