Seismic Isolation of Nuclear Power Plants

The paper presents the world state-of-the-art of the Nuclear Power Plants (NPPs) provided with seismic isolation and focuses on the main problems related to the application of this technology to so peculiar structures, characterized by high masses, large sizes and severe safety requirements due to the possibility of relevant accidents with release of radioactivity and other extremely dangerous materials. Difficulties in the application of seismic isolation to NPPs are mainly due to the lack of specific standards and to the need of manufacturing quite large isolators (and test them in extreme multidirectional dynamic conditions), and using interface components, like pipe expansion joints for hot and pressurized pipelines, capable of absorbing the large relative displacements which occur between the isolated nuclear island and the ground during the seismic attack.