Abstract: A steam generator for a PWR comprise a pressure vessel having an upper portion forming a steam chamber and a bundle of U-shaped exchange tubes within the vessel. A feed-water ring header is located within the pressure vessel above the bundle, extends horizontally and is connected to a feed water inlet nozzle passing through the wall of the pressure vessel, said header having an approximately toridal shape. Feed water is discharged into the pressure vessel above the bundle by crook-shaped tubes each having an end opening into the upper portion of the header of and projecting upwardly from the header. The crook-shaped tubes are spaced apart at substantially equal angular intervals and have respective controlling cross-sectionam flow areas which differ depending on the angular position of the discharge tube on the header.

Abstract: Cold water introduced with a low flow rate into a duct filled with hot water normally circulates in the bottom thereof and accumulates at its end. It is discharged only at the end of the distributor where its pressure is highest. The immiscible hot water is located elsewhere and high thermal stresses appear on the distributor at the interface between two layers. This problem is solved by providing the distributing tubes (2) or the actual duct (1) with cuts (6 and 9) in particular favoring the upstream flow.

Abstract: Device for preventing thermal stratification for a steam generator feed pipe. A fixed helix (14) downstream of a rising break (12) of the pipe subdivides its interior into twisted channels. The cold water entering at a low flame rate is blocked upstream until a predetermined height (h) is reached and completely fills an upstream part (11) to be protected against thermal gradients.

Abstract: The invention concerns a device for separating water and steam for the drying of a moist steam which has a rising current at the inlet of the device. The device comprises at least an assembly (8) comprising drying elements in a zone (12) in which a perforated panel (11) is located. The perforated vertical panel (11) is formed by a grid of expanded metal for deflecting the incident stream (9) of the steam and rendering it horizontal or sightly downwardly inclined (16). The invention is in particular applicable to steam generators of pressurized water nuclear reactors.

Abstract: A steam generator has a pressure vessel containing a stack of exchange tubes and a feedwater header of ring shape connected to a feed water intake pipe passing through the wall of the vessel. A horitzontal section of the pipe contains at least one deflector comprising an axial hub and several helical blades connecting the hub to the wall of the pipe. The blades have a length which represents at least half a winding pitch if the deflector is to counteract thermal stratification only, at least 1.5 winding pitch if for avoiding pressure surges.