Automatic steam generator feedwater control over full power range

In a pressurized water nuclear reactor steam supply system having a recirculation type steam generator including a variable speed feedwater pump, a main feedwater valve and a bypass feedwater valve, a method for controlling the water level in the steam generator comprising:

• measuring the steam flow out of the steam generator and generating a steam flow signal commensurate with the steam flow;
• measuring the feedwater flow into the steam generator and generating a feedwater flow signal commensurate with the feedwater flow;
• measuring the water level in the steam generator and generating a water level signal commensurate with the water level;
• measuring the reactor power and generating a power signal commensurate with the reactor power;
• passing the water level signal through a a first adaptive network, wherein the control coefficients in said first network have a functional form dependent on said power signal, the output of said first network representing a dynamically compensated level signal;
• comprising the steam flow signal with the feedwater flow signal and passing the difference through a first proportional/integral circuit to generate a compensated flow error signal;
• comparing the compensated level signal with the compensated flow error signal to generate a flow demand signal;
• controlling the steam generator water level as a function of said flow demand signal, through a logic scheme including three power regimes corresponding to low, intermediate, and high power levels, wherein,
• the feedwater pump speed demand is constant at low power and is modulated by the flow demand signal at intermediate and high power,
• the bypass valve position is modulated by the flow demand signal at low power, closed at intermediate power and open at high power, and
• the main valve position is closed at low power and modulated by the flow demand signal at intermediate and high power;
• whereby the operation of said feedwater pump, bypass valve and main valve determine the water level in the steam generators during operation of the nuclear steam supply system.