Nuclear reactor containment vessel and method of cooling the nuclear reactor containment vessel

A reactor containment vessel cooling technology for preventing the cooling capability and structural integrity of a reactor containment vessel cooling system from decreasing by lowering the temperature of water vapor and gases acquired by the reactor containment vessel cooling system is provided. Based on the technology, the present invention provides a reactor containment vessel cooling system that acquires water vapor in a reactor containment vessel by using water vapor pressure in the vessel as a drive force, condenses the acquired water vapor into condensate, and cools the reactor containment vessel with the condensate. The reactor containment vessel cooling system includes a heat exchange pool 21 that is arranged apart from a dry well 15 and a suppression chamber 16 in the reactor containment vessel 10 and stores a medium for cooling water vapor, a heat exchanger 22 that is immersed in the heat exchange pool 21, acquires water vapor from the dry well 15 in the reactor containment vessel 10, and performs heat exchange between the eater vapor and the cooling medium in the heat exchange pool 21 to generate condensate, and a condensate drain pipe 25 that extracts the condensate from the heat exchanger 22 and guides and discharges the condensate toward a reactor pressure vessel 12.