Patent Number: 046541900
Section: claims

1. In an emergency feedwater system for the steam generators of a pressurized water nuclear reactor power plant adapted to supply emergency feedwater from a storage tank, with pumps provided to direct emergency feedwater to at least one steam generator, when water from a main feedwater system, which feeds through an inlet line containing a check valve and terminating at a feedwater nozzle to a steam generator, is not available, so as to remove heat from the reactor, the improvement comprising: two separately located subsystems, each subsystem adapted for supplying emergency feedwater to at least one steam generator, each subsystem comprsing;  (a) an emergency feedwater supply tank;  (b) a pair of emergency feedwater lines for discharge of water from the tank, said feedwater lines communicating with the inlet line to a steam generator between the check valve and feedwater nozzle;  (c) an electrically operated motor driven pump in one of said pair of emergency feedwater lines having an electrical power source for activation thereof;  (d) a steam driven pump in the other of said pair of emergency feedwater lines having means for providing steam from a steam generator, to which the said other feedwater line leads, to said pump, and a normally closed valve means associated therewith; and  (e) a cavitating venturi in a said emergency feedwater line at a location following said pump and prior to communicating of said feedwater line with said inlet line. 2. In the emergency feedwater system defined in claim 1, the improvement wherein a cavitating venturi is provided in each of said emergency feedwater lines. 3. In the emergency feedwater system defined in claim 2, the improvement wherein four steam generators are provided and one subsystem is provided for two of said four steam generators and another subsystem is provided for two other of said four steam generators. 4. In the emergency feedwater system defined in claim 3, the improvement wherein a flow modulating means is provided in each emergency feedwater line between the pump and said cavitating venturi. 5. In the emergency feedwater system defined in claim 4, the improvement wherein a first connecting line is provided between said pair of emergency feedwater lines at a location between said pumps and said flow modulating means, and valve means are provided in said first connecting line. 6. In the emergency feedwater system defined in claim 5, the improvement wherein a second connecting line is provided between said pair of emergency feedwater lines at a location between said flow modulating means and said cavitating venturi, and valve means are provided in said second connecting line. 7. In the emergency feedwater system as defined in claim 6, the improvement wherein each of said pumps is capable of supplying a sufficient amount of emergency feedwater to two steam generators at a rate equivalent to the rate at which steam is being removed to dissipate at least the core decay heat. 8. In the emergency feedwater system defined in claim 1, the improvement wherein three steam generators are provided and wherein one of each of said pair of emergency feedwater lines of a said subsystem is adapted for discharge of water from a tank to separate first and second steam generators, each of said emergency feedwater lines contains a cavitating venturi downstream of said pump, and the other of each of said pair of emergency feedwater lines combine to form a common discharge line for discharge of water from a tank to a third steam generator, and a further cavitating venturi is provided in said common discharge line. 9. In an emergency feedwater system defined in claim 8, the improvement wherein said motor driven pumps are located in said emergency feedwater lines which combine to form said common discharge line. 10. In the emergency feedwater system as defined in claim 9, the improvement wherein a flow modulating means is provided in each emergency feedwater line between the pump and said cavitating venturi. 11. In the emergency feedwater system as defined in claim 10, the improvement wherein a first connecting line is provided between said pair of emergency feedwater lines, at a location between said pumps and said flow modulating means, and valve means are provided in said first connecting line. 12. In the emergency feedwater system as defined in claim 11, the improvement wherein a second connecting line is provided between said pair of emergency feedwater lines, at a location between said flow modulating means and said cavitating venturies, and valve means are provided is said second connecting line. 13. In the emergency feedwater system defined in claim 1, the improvement wherein two steam generators are provided and wherein each said pair of emergency feedwater lines combine to form a common discharge line, to separate ones of said two steam generators, and a said cavitating venturi is provided in each of said common discharge lines. 14. In the emergency feedwater system defined in claim 13, the improvement wherein a flow modulating means is provided in each emergency feedwater line between the pump and common discharge line. 15. In the emergency feedwater system defined in claim 14, the improvement wherein valve means are provided in each said emergency feedwater line between said flow modulating means and said common discharge line.