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EJ System (Technological Safeguards Cooling Water System) at Vandellós II NPP


The project carried out by IDOM under an EPCC contract (Engineering, Procurement, Construction and Commissioning) consisted of the development and implementation of a new system that comprises of the Ultimate Heat Sink (UHS) for the thermal loads transferred from the Component Water Cooling System (EG System). The project was one of the most challenging design modifications made in Spain. The new Technological Safeguards Cooling Water System (EJ System) complemented the old Essential Service Water System (EF System), which has been converted to a non-safety-related support system.

The new EJ system is the ultimate support system for cooling of the Technological Safeguard systems which ensures a safe shutdown of a nuclear power plant in case of an accident. The EJ system can replace the old (EF) system under any operating condition (normal, shutdown and design basis accident). The new system uses a system of cooling towers as a heat sink, with a water reservoir of 30000m3 stored in an open pond.

Moreover, as a preliminary phase of the deployment of the EJ system, the Emergency Diesel Generator System (KJ System) and Essential Chilled Water System (GJ System) became independent of the EF System. In both cases, an autonomous cooling system was installed, in which Air-Cooled Heat Exchangers dissipate the heat load directly into the atmosphere.

The proposed modifications involved the design and construction of new buildings and installations, modifications to existing buildings as well as the design and construction of new tunnels for the installation of underground pipes, cooling pools and towers. After completion of the detailed engineering, IDOM also carried out the Construction and Project Management for the implementation of the design modifications. Safety and licensing experts completed all the required documentation associated with the licensing of the new system. They also provided support to the owner during the negotiations with the Nuclear Safety Council (Consejo Seguridad Nuclear, CSN). The Quality Assurance requirements were of paramount importance on the project as the project was Safety-Related. An independent team of Nuclear Quality Assurance professionals was formed who verified the fulfilment of the most rigorous technical requirements.

New Build

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Asociación Nuclear Ascó-Vandellós (ANAV)


  • Idom_Nuclear_Services_Design_Construction_Commissioning_EJ_System_Technological_Safeguards_Cooling_Water_System_Vandell_s_II_NPP_ANAV
  • Idom_Nuclear_Services_Design_Construction_Commissioning_EJl_Safeguards_Cooling_Water_System_Vandell_s_NPP_ANAV