CAGE Cofrentes

 Earthquake Engineering & Soil-Estructure Interaction Analysis

Alternative Emergency Management Center for the Nuclear Power Plant of Cofrentes.

Following the accident at the Fukushima Nuclear Power Plant caused by the March 2011 earthquake, the Western European Nuclear Regulator Association (WENRA) imposed stress tests to be carried out at European nuclear power plants. Based on the results of the evaluations carried out, the Consejo de Seguridad Nuclear (CSN) asked the spanish nuclear power plants to build a center that allows to manage the plant in case of a severe accident.

To cope with the request of the CSN, an alternative emergency management center (CAGE) has been designed in the Cofrentes plant to deal with situations that are defined beyond the design bases of the nuclear power plant.

The CAGE consists of a reinforced concrete building whose seismic design makes it resistant to severe earthquakes. They are built in non-floodable areas and are intended to have the resources to deal with an emergency situation, such as extensive damage to the facility. The building has complete autonomy. Likewise, this building has decontamination areas, its own medical services, chemical laboratory, radiological control, filling station for breathing air bottles and rest areas for staff.

Soil-Estructure Interaction Studies and Added Value

Dynamis’ mission in the Cofrentes CAGE project was to carry out advanced design engineering for IBERDROLA INGENIERIA Y CONSTRUCCION (IBERINCO). In order to take into account the effects of soil-structure interaction in the seismic case, we obtained the frequency variations of the soil stiffness and damping (more commonly known as dynamic impedances). Dynamis also built a finite element 3D model to obtain the in-structure response spectra (ISRS) that size the equipment that are incorporated.

Two levels of earthquake were analyzed, an operating basis earthquake (OBE) scaled to 0.3g and safe-shutdown earthquake (SSE) scaled to 0.5g.

The Analyses performed include the consideration of soil-structure interaction effects through a simplified method where the stiffness and damping of the soil are obtained as a function of the frecuency (the so called dynamic impedances). Dynamis also built a finite element 3D model where this impedances functions were implemented to obtain the in-structure response spectra (ISRS) that size the equipment that are incorporated.