A steam generator comprising: a primary side including: an inlet chamber for receiving a heated primary fluid; an outlet chamber for returning the primary fluid to a heating source; a tube sheet forming at least one wall of the inlet chamber and at least one wall of an outlet chamber; a plurality of heat exchange tubes respectively having first and second ends and an intermediate extent, with the first ends extending through the tube sheet and opening into the inlet chamber and the second ends extending through the tube sheet and opening into the outlet chamber with the intermediate extent passing through and in heat exchange relationship with a secondary side; the secondary side including; a generally cylindrical outer shell have a central axis; a generally cylindrical wrapper supported above at least a portion of the tube sheet, within, spaced from and coaxially position with the shell and forming a downcomer region between at least part of the wrapper and the shell; a feedring positioned above the downcomer region for introducing feedwater into the downcomer region; and characterised in that a plurality of standpipes spaced circumferentially along the feedring, extending vertically from an upper portion of an interior of the feedring downward through the interior of the feedring and having a feedwater intake in the upper portion of the feedring and a feedwater discharge at or below a bottom of the feedring, for distributing the feedwater into the downcomer region. a primary side including: an inlet chamber for receiving a heated primary fluid; an outlet chamber for returning the primary fluid to a heating source; a tube sheet forming at least one wall of the inlet chamber and at least one wall of an outlet chamber; a plurality of heat exchange tubes respectively having first and second ends and an intermediate extent, with the first ends extending through the tube sheet and opening into the inlet chamber and the second ends extending through the tube sheet and opening into the outlet chamber with the intermediate extent passing through and in heat exchange relationship with a secondary side; the secondary side including; a generally cylindrical outer shell have a central axis; a generally cylindrical wrapper supported above at least a portion of the tube sheet, within, spaced from and coaxially position with the shell and forming a downcomer region between at least part of the wrapper and the shell; a feedring positioned above the downcomer region for introducing feedwater into the downcomer region; and an inlet chamber for receiving a heated primary fluid; an outlet chamber for returning the primary fluid to a heating source; a tube sheet forming at least one wall of the inlet chamber and at least one wall of an outlet chamber; a plurality of heat exchange tubes respectively having first and second ends and an intermediate extent, with the first ends extending through the tube sheet and opening into the inlet chamber and the second ends extending through the tube sheet and opening into the outlet chamber with the intermediate extent passing through and in heat exchange relationship with a secondary side; the secondary side including; a generally cylindrical outer shell have a central axis; a generally cylindrical wrapper supported above at least a portion of the tube sheet, within, spaced from and coaxially position with the shell and forming a downcomer region between at least part of the wrapper and the shell; a feedring positioned above the downcomer region for introducing feedwater into the downcomer region; and a generally cylindrical outer shell have a central axis; a generally cylindrical wrapper supported above at least a portion of the tube sheet, within, spaced from and coaxially position with the shell and forming a downcomer region between at least part of the wrapper and the shell; a feedring positioned above the downcomer region for introducing feedwater into the downcomer region; and