Abstract: Excessive primary cooldown and start up of the auxiliary feedwater system in a pressurized water reactor (PWR) following a reactor trip are avoided by switching to primary coolant T.sub.avg programmed, main feedwater flow control in place of normal level programmed control. The Low T.sub.avg set point at which the main feedwater isolation valves are closed is lowered below the no load T.sub.avg temperature set point and the flow rate is decreased gradually to zero at a T.sub.avg between these two set points. In addition, the low-low level set point at which the auxiliary feedwater system is started is lowered if possible, and/or the level signal is filtered, or the start signal delayed, to increase the margin to the low-low set point.

Abstract: A steam generator level measurement system of the type having a reference leg which is kept full of water by a condensation pot, has a separator pot in the connecting line between the condensation pot and the steam phase in the steam generator to remove excess liquid from the steam externally of the steam generator. The separator pot has an expansion chamber which slows down the velocity of the steam/liquid mixture to aid in separation, and a baffle, which directs steam introduced at the top of the chamber on one side of the baffle to flow downward and then upward for discharge on the other side of the baffle to avoid direct liquid penetration into the line connected to the condensate pot.