Seismic analysis and evaluation of the base isolation system in AP1000 NI under SSE loading

Abstract Safety and integrity of NPP must be ensured during the plant life in any design conditions, particularly, in the event of a severe earthquake. Base isolation as a popular and powerful technology can drastically reduce the seismic response of the structure and prevent the structure from damage. The objective of this paper is to numerically investigate the dynamic response of the AP1000 Nuclear Island (NI) building with and without isolators under a typical safe shutdown earthquake (SSE). By the help of a sophisticated detailed three-dimensional finite element model of the Nuclear Island, the different design solutions are compared in terms of acceleration and relative displacement. The decreasing amplitude ratio (DAR) obtained in the calculations highlights the effectiveness of the isolation system in mitigating the seismic response of the nuclear island of AP1000. Acceleration floor response spectra (carried out from both isolated and non-isolated seismic analysis) are herein also presented and compared in order to validate the isolation technology effectiveness. The obtained numerical results highlight the drastic reduction of considered floor accelerations as the base isolation major effect. The connection of pipelines and design criteria of isolators presently recommended for the stability of isolated building are also validated and verified to highlight the feasibility and safety of the base isolation system. In addition, seismic gap, expansion joint and horizontal fail safe system are also recommended to apply in the isolated structure.

[1]  Jianyun Chen,et al.  Numerical simulation and investigation of the base isolated NPPC building under three-directional seismic loading , 2013 .

[2]  Jianyun Chen,et al.  Dynamic characteristics of AP1000 shield building for various water levels and air intakes considering fluid-structure interaction , 2014 .

[3]  A. Colaiuda,et al.  Investigation upon the dynamic structural response of a nuclear plant on aseismic isolating devices , 2001 .

[4]  R. Lo Frano,et al.  Preliminary evaluation of the seismic response of the ELSY LFR , 2012 .

[5]  Andrew S. Whittaker,et al.  Seismic performance assessment of base‐isolated safety‐related nuclear structures , 2010 .

[6]  T. V. S. R. Appa Rao,et al.  Non-linear dynamic response of a reinforced concrete secondary containment shell subjected to seismic load , 2001 .

[7]  Mohd Zamin Jumaat,et al.  Non-linear time domain analysis of base isolated multi-storey building under site specific bi-directional seismic loading , 2012 .

[8]  Jianyun Chen,et al.  Dynamic analysis of AP1000 shield building for various elevations and shapes of air intakes considering FSI effects subjected to seismic loading , 2014 .

[9]  Andrew S. Whittaker,et al.  Seismic demands on secondary systems in base‐isolated nuclear power plants , 2007 .

[10]  Giuseppe Forasassi,et al.  Preliminary evaluation of seismic isolation effects in a Generation IV reactor , 2011 .

[11]  Marco Domaneschi,et al.  Seismic Isolation of the IRIS Nuclear Plant , 2009 .

[12]  Man Liu,et al.  Formulation of Rayleigh damping and its extensions , 1995 .

[13]  J. Y. Chen,et al.  Damage mechanism and mode of square reinforced concrete slab subjected to blast loading , 2013 .

[14]  Massimo Forni,et al.  Shaking Table Tests on a Spherical Tank Mock-Up Provided With Seismic Isolation and Flexible Piping Connections , 2005 .

[15]  C. F. Zhao,et al.  Damage mechanism and response of reinforced concrete containment structure under internal blast loading , 2012 .

[16]  Giuseppe Forasassi,et al.  Isolation systems influence in the seismic loading propagation analysis applied to an innovative near term reactor , 2010 .

[17]  Richard S. Orr,et al.  Finite element modeling of the AP1000 nuclear island for seismic analyses at generic soil and rock sites , 2007 .