A new method of essential decreasing of floor response spectra is proposed in the paper. The design considers interconnection of main structures inside NPP containment by High Viscous Dampers. In result within the same ZPGA level of a reference earthquake or the same intensity of other than seismic external loads the acceleration range of floor response spectra could be dropped in factor 2 to 3 or even more depending on a number of installed damping devices.

That way an essential decreasing of dynamic loads on structures, components and systems (SSC) could be achieved. Another important advantage of the actual proposal consists of eliminating of possible interactions and collisions in the gaps between building structures that wears potential threat of building failure. In-depth dynamic analysis of the Reactor Building System with proposed design decision was undertaken and presented in the paper. Both a simplified stick model and accurate 3D Finite Element Model of PWR Reactor Building were investigated and comparative analysis results for the systems without dampers and with dampers were obtained. The proposed decision could be relatively simply implemented in design of a new Nuclear Plants as well as for existing one and upgrade its seismic, wind, blast and other kind of external event capacities.