Internal structures are located within the space limited by the inner containment and the building foundation plate. They include four main ceilings at elevations of +8.000, +16.100,+22.500 and +34.300, which are rigidly bonded to each other and to the foundation plate by walls, columns and the reactor vault located in the centre of the building, thus forming a single cast-in-situ reinforced concrete three-dimensional structure. The ceilings are separated from the inner containment by the joint. All reactor building structures are made of cast-in-situ reinforced concrete, except for removable ceiling sections of prefabricated reinforced concrete slabs arranged above the equipment.