Abstract: The steam generator (1) comprises an outer casing (2) with an axis (8) that is in a vertical disposition when the heat exchanger is in service, a bundle of tubes having straight portions that are parallel to one another and to the axis (8) of the heat exchanger (1) inside the outer casing (2), at least one tube plate (4) having through holes, each receiving the end of a tube of the bundle, and at least one water chamber having a wall (6) that is circularly symmetrical about the axis (8) of the heat exchanger (1), the water chamber being fixed to the tube plate (4) at the bottom of the heat exchanger. The surface (14a) of the solid bottom (14) of the heat exchanger includes at least one central point disposed substantially on the axis of the heat exchanger (1) at a highest level relative to the set of points constituting the inside surface (14a) of the bottom (14) of the heat exchanger.

Abstract: The wall of the water chamber is welded to the tube plate via a connection ring projecting from the tube plate. The wall of the water chamber is welded to the tube plate after the bundle of tubes has been secured to the tube plate. The connection ring presents a length in the axial direction that is equal to or greater than 250 mm.

Abstract: The steam generator (1) comprises an outer casing (2) with an axis (8) that is in a vertical disposition when the heat exchanger is in service, a bundle of tubes having straight portions that are parallel to one another and to the axis (8) of the heat exchanger (1) inside the outer casing (2), at least one tube plate (4) having through holes, each receiving the end of a tube of the bundle, and at least one water chamber having a wall (6) that is circularly symmetrical about the axis (8) of the heat exchanger (1), the water chamber being fixed to the tube plate (4) at the bottom of the heat exchanger. The surface (14a) of the solid bottom (14) of the heat exchanger includes at least one central point disposed substantially on the axis of the heat exchanger (1) at a highest level relative to the set of points constituting the inside surface (14a) of the bottom (14) of the heat exchanger.

Abstract: The wall (6) of the water chamber (5) is welded to the tube plate (4) via a connection ring (10) projecting from the tube plate (4). The wall (6) of the water chamber is welded to the tube plate (4) after the bundle of tubes (3) has been secured to the tube plate (4). The connection ring (10) presents a length in the axial direction that is not less than 300 mm and that is preferably about 370 mm.