A steam generator for a pressurized-water coolant nuclear reactor is of the type having a vertical housing with its lower portion closed by a horizontal tube sheet in which the inlet and outlet legs of an inverted U-shaped tube bundle are mounted, one forming an inlet leg and the other forming an outlet leg for the pressurized-water coolant circulated via the tube bundle and the reactor. The tube bundle is peripherally enclosed by a vertical shell forming a feed-water descent space between it and the housing with this space adjacently above the tube sheet peripherally opening to the latter for radially inwardly directed feed-water flow thereover through the interspaced tubes of the tube bundle legs and upward flow through the latter to generate steam in the housing. The feed-water flow over the tube sheet and through the tubes of the inlet leg, which is the hotter of the two legs, tends to locally boil so that corrosion-promoting products in the feed water are concentrated to form deposits introducing the danger of corrosion failure on the part of the tubes and/or tube sheet. To prevent this, means are provided for removing a portion of the feed water from adjacently above the tube sheet and between the interspaced tubes of the inlet leg, the means preferably removing a plurality of flows of feed water from a plurality of positions interspaced transversely over the tube sheet. The constant removal of the flows of feed-water increases the rate with which the feed water radially flows inwardly over the tube sheet and upwardly through the tube bundle, consequently reducing or eliminating the boiling tendency throughout the critical area where this tendency occurs over the portion of the tube sheet in which the inlet leg of the tube bundle is mounted.