Patent Number: 
Section: claims

1. A heat removal system for a nuclear power plant, the heat removal system comprising:an air duct provided on an outside of a reactor containment building, the air duct being configured to allow air flow of outside air therethrough and being vertical to the ground;a heat exchanger disposed in the air duct, the heat exchanger being constructed and positioned to be in the air flow through the air duct;a first pipe operatively connected to a heat source on an inside of the reactor containment building and being configured to transfer fluid heated in the reactor containment building to the heat exchanger;a second pipe operatively connected to the interior of the reactor containment building and configured to transfer cooled fluid to the interior of the reactor containment building;a cooling water supply module above the heat exchanger and configured to release cooling water into the air duct; anda first shut-off valve positioned in the air duct below the heat exchanger, the first shut-off valve being constructed and operable to selectively open and close the air duct below the heat exchanger,wherein the heat exchanger is configured to be alternatively at least partially cooled using outside air flowing across the heat exchanger inside of the air duct when the first shut-off valve is open, and cooled by being immersed in a cooling water supplied from the cooling water supply module when the first shut-off valve is closed. 2. A residual heat removal system for a nuclear power plant, the residual heat removal system comprising:an air duct provided on an outside of a reactor containment building, the air duct being configured to allow air flow of outside air therethrough and being vertical to the ground;a heat exchanger disposed in the air duct, the heat exchanger being constructed and positioned to be in the air flow through the air duct;a first pipe operatively connected to a steam generator disposed on an inside of the reactor containment building and being configured to transfer steam generated in the steam generator to the heat exchanger; anda second pipe operatively connected to the steam generator and being configured to transfer to the steam generator condensation water that is cooled and condensed in the heat exchanger;a cooling water supply module connected to spray a cooling water on the heat exchanger; anda first shut-off valve positioned below the heat exchanger, the first shut-off valve being constructed and operable to selectively open and close a lower end of the air duct,wherein the heat exchanger is configured to be alternatively air-cooled using outside air flowing across the heat exchanger inside of the air duct, water- and air-cooled using water sprayed on the heat exchanger and air flowing across the heat exchanger inside of the air duct, and water-cooled by being immersed in a cooling water supplied from the cooling water supply module when the first shut-off valve is closed. 3. The residual heat removal system of claim 2, wherein the cooling water supply module is located at a higher elevation when compared to the heat exchanger so as to supply the cooling water to the heat exchanger through use of a water head differential. 4. The residual heat removal system of claim 2, the cooling water supply module comprising:a water pipe arranged to supply the cooling water; anda water pipe shut-off electric valve arranged to open and close the water pipe. 5. The residual heat removal system of claim 2, further comprising:a second shut-off valve positioned over the heat exchanger, to selectively open and close an upper end of the air duct,wherein the first pipe and the second pipe comprise a first opening and closing valve unit and a second opening and closing valve unit to selectively open and close the first pipe and the second pipe, respectively, andthe air duct being cut off from the outside air and the reactor containment building when the first shut-off valve, the second shut-off valve, the first opening and closing valve unit, and the second opening and closing valve unit are closed. 6. The residual heat removal system of claim 2, further comprising:a connection pipe disposed between the air duct and the reactor containment building, the connection pipe comprising a check valve and a safety valve,whereby a fluid inside the air duct is released into the reactor containment building when the first shut-off valve, the second shut-off valve, the first opening and closing valve unit, and the second opening and closing valve unit are closed. 7. The residual heat removal system of claim 2, wherein the first pipe and the second pipe have a downward slope in a direction of the steam generator.