Patent Number: 
Section: claims

1. A passive cooling system of a nuclear power plant, the passive cooling system comprising:a steam generator in which steam is generated by heat exchange with a primary coolant system including a nuclear reactor;a cooling water storage tank storing cooling water therein;a water cooling heat exchanger disposed in the cooling water storage tank;an air cooling heat exchanger connected to the steam generator in parallel with the water cooling heat exchanger,wherein the air cooling heat exchanger is located outside of the cooling water storage tank;a divergence valve controllable to divert steam from the steam generator into both the water cooling heat exchanger and the air cooling heat exchanger,wherein the divergence valve controls the flow of steam generated in the steam generator which passes through the water cooling heat exchanger to be condensed by heat exchange with the cooling water,wherein the divergence valve controls the flow of steam generated in the steam generator which passes through the air cooling heat exchanger to be condensed by heat exchange with ambient air, andwherein the divergence valve includes an inlet, a first outlet, and a second outlet;a first pipe connecting an upper portion of the steam generator and the inlet of the divergence valve,wherein the first pipe allows steam generated in the steam generator to flow from the steam generator to the divergence valve;a second pipe connecting the first outlet of the divergence valve and an inlet of the water cooling heat exchanger,wherein the second pipe allows steam generated in the steam generator to flow from the first outlet of the divergence valve to the water cooling heat exchanger;a third pipe connecting the second outlet of the divergence valve and an inlet of the air cooling heat exchanger,wherein the third pipe allows steam generated in the steam generator to flow from the second outlet of the divergence valve to the air cooling heat exchanger;a fourth pipe connected to each of an outlet of the water cooling heat exchanger, an outlet of the air cooling heat exchanger, and a lower portion inlet of the steam generator,wherein the fourth pipe allows condensed steam to flow from the water cooling heat exchanger to the lower portion inlet of the steam generator,wherein the fourth pipe allows the condensed steam from the water cooling heat exchanger to be introduced in a liquid water state into the lower portion inlet of the steam generator,wherein the fourth pipe allows condensed steam to flow from the air cooling heat exchanger to the lower portion inlet of the steam generator, andwherein the fourth pipe allows the condensed steam from the air cooling heat exchanger to be introduced in a liquid water state into the lower portion inlet of the steam generator;a first open/close valve disposed in the second pipe,wherein the first open/close valve controls the flow of the steam passing through the second pipe;a second open/close valve disposed in the third pipe,wherein the second open/close valve controls the flow of the steam passing through the third pipe; anda cooling tower,wherein each of the cooling water storage tank, the water cooling heat exchanger, and the air cooling heat exchanger are located in the cooling tower. 2. The passive cooling system according to claim 1, wherein the water cooling heat exchanger and the air cooling heat exchanger are positioned above the steam generator such that the cooling water and the steam naturally circulate by gravity. 3. The passive cooling system according to claim 1, wherein the cooling tower having an air inlet in a lower portion thereof.