Patent Number: 
Section: claims

1. A passive natural circulation cooling system configured for use with a nuclear reactor, comprising:a passive condensation tank connected between a main steam line and a feedwater line of a steam generator and configured to accommodate cooling water therein; anda condensation heat exchanger provided in the passive condensation tank to be in contact with the cooling water, and configured to transfer heat transferred from the steam generator to the cooling water; anda condensate water recirculation device provided in or above the passive condensation tank and configured to condense the cooling water so that the cooling water circulates inside the passive condensation tank,wherein the condensate water recirculation device comprises:a duct extending upward from an upper portion of the passive condensation tank; anda first separator extending downward from one side of an inner wall of the passive condensation tank toward another side in an inclined manner, the first separator forming a portion with the another side of the inner wall to communicate a lower space and an upper space with each other,wherein at least a part of the first separator is configured to be submerged in the cooling water, andwherein the condensation heat exchanger is disposed in the lower space of the first separator. 2. The system of claim 1, wherein the plurality of separators further comprise:at least one of second and third separators extending along a lengthwise direction of the duct to minimize a leakage of steam rising along the duct. 3. The system of claim 2, wherein the second and third separators are spaced apart from each other,wherein the second separator extends upward from the first separator, andwherein the third separator extends downward from an upper inner wall of the duct to generate a downward flow path of steam rising along the second separator. 4. The system of claim 2, wherein the first separator is provided with a steam collection guide pipe, andwherein the steam collection guide pipe extends into a lower space of the first separator and an inner space of the duct partitioned by the second separator. 5. The system of claim 4, wherein an inserted length of the steam collection guide pipe into the lower space of the first separator is determined based on information related to a preset water level and pressure. 6. The system of claim 1, wherein the duct is provided therein with a heat exchanger to transfer heat of the cooling water inside the duct to external air. 7. The system of claim 1, wherein the duct is provided with an external air outlet formed on an upper side thereof, andwherein the external air outlet is provided therein with a condensate water collecting structure for further collecting condensate water. 8. The system of claim 1, further comprising a heat exchanger installed below the first separator to receive heat from the cooling water within the lower space of the first separator. 9. The system of claim 8, wherein the heat exchanger comprises:an inlet formed on the first separator to allow the cooling water in the upper space of the first separator to be introduced therethrough;an outlet formed on the first separator at a position spaced apart from the inlet to allow the cooling water introduced through the inlet to flow out therethrough; anda body portion connecting the inlet and the outlet on a rear surface of the first separator, and configured so that the introduced cooling water is evaporated by exchanging heat with the cooling water within the lower space of the first separator while passing through the body portion. 10. The system of claim 9, wherein the outlet is located higher than the inlet above the first separator. 11. The system of claim 9, wherein the body portion is formed to be inclined upward from the inlet to the outlet. 12. The system of claim 9, wherein the body portion comprises a plurality of tubes formed in a bundle to increase a heat exchange area. 13. The system of claim 12, wherein the inlet and the outlet are provided in plurality, respectively, andwherein the body portion comprises:a plurality of first pipes each having one side connected to each of the plurality of inlets and another side extending downward;a plurality of second pipes each having one side connected to the another side of each of the plurality of first pipes, and another side formed in an inclined direction; anda plurality of third pipes each having one side connected to the another side of each of the plurality of second pipes, and another side extending upward to be connected to each of the plurality of outlets. 14. The system of claim 13, wherein the body portion further comprises:a first connection portion connecting the plurality of first pipes and the plurality of second pipes so that the cooling water introduced from each of the plurality of first pipes is joined and then dispersed again into the plurality of second pipes; anda second connection portion connecting the plurality of second pipes and the plurality of third pipes so that the cooling water introduced from each of the plurality of second pipes is joined and then dispersed again into the plurality of third pipes. 15. The system of claim 8, wherein the condensation heat exchanger is provided in plurality, andwherein heights of the inlet and the outlet of each of the condensation heat exchangers are sequentially reduced on the first separator. 16. The system of claim 8, wherein the condensate water recirculation device further comprises:a second separator located above the first separator with being spaced apart from the first separator, to condense steam evaporated from the cooling water in the upper space of the first separator and steam generated in the heat exchanger. 17. The system of claim 16, wherein the second separator extends downward from one side of the passive condensation tank toward another side in an inclined manner. 18. The system of claim 17, wherein the second separator is provided with a plurality of protrusions formed on one surface thereof in a protruding manner to increase heat exchange efficiency. 19. The system of claim 1, wherein a plurality of partitions are formed on an inner wall of the duct to induce condensation of steam contained in air rising along the duct and to prevent a leakage of steam. 20. The system of claim 1, wherein an outer wall of the duct is coated with a material having a white-based color so as to suppress a temperature rise inside the duct.