Patent Number: 
Section: claims

1. A steam dump control system for controlling a response of a nuclear reactor to a transient, comprising:at least one steam dump valve having a positioner operable to open said valve;a coolant sensor system for monitoring an average temperature of a coolant of the nuclear reactor and providing a temperature error signal when the average temperature of the coolant exceeds a reference temperature;a nuclear power plant power sensing system for monitoring power of the reactor and power of a turbine, and providing a power error signal when the power of the turbine is reduced and the power of the turbine changes relative to the power of the reactor at a rate that exceeds a preselected rate; anda control means having an input from the coolant sensor system and an input from the nuclear power plant power sensing system, for combining the temperature error signal and the power error signal to produce a valve control signal to control said valve positioner. 2. The system of claim 1 wherein said nuclear reactor is a pressurized water reactor. 3. The system of claim 1 wherein said steam dump valves are selected from the group consisting of condenser dump valves and atmospheric steam dump valves. 4. The system of claim 1 wherein a summator is provided for summing said temperature error signal and said power error signal. 5. A system for controlling a response of a nuclear reactor to a load rejection transient, comprising:a coolant sensor system for monitoring an average temperature of a coolant of the nuclear reactor and generating a temperature error when the average temperature of the coolant exceeds a reference temperature;a power sensing system for monitoring power of the nuclear reactor and power of a turbine and generating a power error when the power of the turbine is reduced and the power of the turbine changes relative to the power of the reactor at a rate that exceeds a preselected rate;a conversion means to convert the power error to a corresponding temperature error;a summator to add the temperature error from the coolant sensor system and the temperature error corresponding to the power error from the power sensing system to generate a resultant temperature error;a control means to provide a valve control signal based on the resultant temperature error; andat least one steam dump valve which is operable to open on receipt of the valve control signal. 6. The system of claim 5 wherein the nuclear reactor comprises a Reactor Coolant System having a hot leg with a temperature, Thot, and a cold leg with a temperature, Tcold, said average temperature determined from an average of Thot and Tcold. 7. The system of claim 5 wherein the nuclear reactor comprises a turbine having an impulse chamber and said reference temperature is determined from a pressure measured in the impulse chamber of the turbine. 8. The system of claim 5 wherein the at least one steam dump valve has a valve positioner and the valve positioner enables opening of the at least one steam dump valve.