Abstract: The feedwater of a nuclear reactor at low-power levels, particularly during start-up, is controlled by combining an error signal component dependent on the departure of the actual level in the steam generator from a preset level and a component dependent upon the nuclear power delivered by the reactor. The nuclear-power change is the earliest reaction to the command to change the load level or to start up so that the nuclear-power component is a feedforwarded component. The invention prevents the system from "chugging." It also avails automatic control of the feedwater at low loading heretofore not feasible.