Abstract: A system (10) for dissipating heat from the interior space (50) of a containment structure (3, 6) for a nuclear reactor (2), for an indefinite time period, comprises a first heat exchanger (15, 15') outside said containment structure (3, 6) which is submerged vertically in a pool (11) associated with the exterior of the top wall (4, 7) of the structure (3, 6), and a second heat exchanger (25) placed in the interior space (50), said first and second heat exchangers (15, 25) being fluid connected to each other in a closed loop circuit (28) with piping (23, 24) containing a thermal carrier fluid. Said pool (11 is provided with a covering (90) defining a first duct (12) in communication with an outside air intake, and a second duct (13) communication with a chimney (14), the interconnection of said ducts (12, 13) being inhibited by the water present in the pool (11) when filled to a predetermined level (9).

Abstract: A pressurized-water nuclear reactor with inherent safety comprises a pressurized vessel filled with borated water within which is the body of the reactor. The latter includes an upper part and a lower part within which is the reactor core. The upper part includes a first tubular cavity, a second tubular cavity coaxial with and outside the first cavity and a plurality of helical tube bundles extending between respective pairs of connectors for the inlet and outlet of water circulating in the tube bundles.

Abstract: An intrinsic-safety nuclear reactor of the pressurized water type, having:a reactor vessel (2) equipped with a core (4), a lower header (5) and an upper header (6), at least one heat exchanger (3) with a secondary fluid, means of hydraulic connection (9, 10) between said headers and said heat exchanger and at least one circulation pump (11),a pressurized container (1) surrounding the reactor vessel (2) and which defines a tank (15) full of a cold, neutron-absorbing liquid;pipes (20) allowing communication between the lower area of said tank and the lower header of the vessel, as well as pipes (21) allowing communication between the upper area of said tank and the upper header,in which the pressure drop in the primary fluid across the core is substantially equal to the difference in head between the cold column of said tank and the hot column of the vessel.The pressurized container (1) is immersed in a pool (18) containing a neutron-absorbing liquid at atmospheric pressure.

Abstract: The invention refers to a solution for the reactor block of a sodium-cooled fast reactor, fitted with an inner cylindrical vessel. This forms the mechanical structure for hydraulic separation 7 between the primary sodium hot header 2 and the cold header 3. The hot header is located in the area above the core, and the cold header, having a larger volume and an annular shape, is located all around the hot header. According to the invention the primary pumps and intermediate exchangers 8 are immersed in the cold header 3. The intermediate heat exchangers 8 are of the straight tube bundle type, with primary sodium outside the tubes, and they are hydraulically connected to the hot header by a transverse duct 13, solid with the inner cylindrical vessel 7, and mechanically sealed where it interfaces with the heat exchanger. This mechanical sealing system is made as close against the heat exchanger, as possible, so that the heat exchanger is removable.