A unified approach for the seismic design of 500 MWe pressurized heavy water reactor buildings

India is planning to increase its nuclear capacity by const-ructing a number of small size (235 Mwe) and large size (500 MWe) pressurised heavy water reactors (PHWRs). To enable the construction of a series of power reactors of standardised design at various rocky sites under consideration, an enveloping ground motion has been generated which takes care of the local seismic conditions at these sites. Seismic analysis of a typical 500 MWe PHWR building has been carried out for local site conditions as well as for the enveloping ground motion. The paper presents the approach adopted for developing standard earthquake design for 500 MWe nuclear power plants. Various features of modelling are also described in this paper.