Steam generator assembly for pressurized water reactors with a straight tube bundle and a partial flow preheater traversible by pressurized water

Steam generator assembly for pressurized water reactors having a housing surrounding a straight tube bundle traversible by pressurized water and connected to a pressurized water inlet chamber and a pressurized water outlet chamber, respectively, at opposite ends thereof, the housing having an inlet and an outlet for feedwater flowing into and out of the housing over the tube bundle and being vaporized and slightly superheated in a single pass therethrough, comprising two pressurized water outlet lines of relatively smaller and larger diameter, respectively, extending from the outlet chamber, a partial flow preheater for the feedwater heatable by pressurized water connected to the outlet line of relatively smaller diameter, said partial flow preheater having a pressurized water outlet line, and a control valve connected in said pressurized water outlet line of said partial flow preheater for controlling the pressurized water flow through said partial flow preheater so as to effect maximal preheating of feedwater therein up to substantially vaporization temperature thereof.