Patent Number: 
Section: claims

1. A passive containment heat removal system, comprising:an outer containment (2);an inner containment (1) disposed in the outer containment (2),an air duct (200) formed between the inner containment (1) and the outer containment (2) having an air inlet (4) and an air outlet (5);a spraying assembly (10) disposed outside the inner containment (1) and configured to passively spray cooling water to an outer wall of the inner containment (1) to cool the inner containment (1);a built-in heat exchanger (9) disposed in the inner containment (1);an air cooling channel (171) located outside the outer containment (2) and having an air inlet (18) of the air cooling channel and an air outlet (21) of the air cooling channel, wherein the air cooling channel (171) is defined by a chimney wall (17) and an outer wall of the outer containment (2) or by the chimney wall (17) isolated from the outer containment (2); andan external air cooler (12) disposed in the air cooling channel (171) with an inlet connected with an outlet of the built-in heat exchanger (9) via a first communication pipe (13) and an outlet connected with an inlet of the built-in heat exchanger (9) via a second communication pipe (14), wherein a filter (19) is disposed in the air cooling channel (171) between the air inlet of the air cooling channel (18) and the external air cooler (12);wherein a plurality of the air cooling channels (171) are provided and arranged at regular intervals in a circumferential direction of the outer containment (2), a plurality of the external air coolers (12) are provided and disposed correspondingly in the plurality of the air cooling channels (171), and a plurality of the built-in heat exchangers (9) are provided, each of the built-in heat exchangers (9) being connected with at least one of the external air coolers (12). 2. The passive containment heat removal system according to claim 1, wherein when an accident happens, the spraying assembly sprays the cooling water to the outer wall of the inner containment and a heat-carrying agent is circulated naturally between the external air cooler and the built-in heat exchanger to cool the inner containment, so that an amount of spraying water of the spraying assembly is reduced per unit time and a spraying time is extended; andafter the cooling water of the spraying assembly is exhausted, the inner containment is cooled by an air in the air duct and the heat-carrying agent circulated naturally between the external air cooler and the built-in heat exchanger. 3. The passive containment heat removal system according to claim 1, wherein when an accident happens, the spraying assembly sprays the cooling water to the outer wall of the inner containment to cool the inner containment and at the same time a heat-carrying agent is not circulated naturally between the external air cooler and the built-in heat exchanger; andafter the cooling water of the spraying assembly is exhausted, the inner containment is cooled by the air flow in the air duct and the heat-carrying agent circulated naturally between the external air cooler and the built-in heat exchanger. 4. The passive containment heat removal system according to claim 1, wherein when an accident happens, the spraying assembly sprays the cooling water to the outer wall of the inner containment to cool the inner containment;when a temperature and/or a pressure in the inner containment exceeds a designated threshold value during spraying the cooling water, a heat-carrying agent is circulated naturally between the external air cooler and the built-in heat exchanger; andafter the cooling water of the spraying assembly is exhausted, the inner containment is cooled by the air flow in the air duct and the heat-carrying agent circulated naturally between the external air cooler and the built-in heat exchanger. 5. The passive containment heat removal system according to claim 1, wherein when an accident happens, the spraying assembly sprays the cooling water to the outer wall of the inner containment to cool the inner containment, andafter the cooling water of the spraying assembly is exhausted, the inner containment is cooled by the air flow in the air duct, andwhen the temperature and/or the pressure in the inner containment exceeds the designated threshold value during spraying the cooling water as well as after the cooling water is exhausted, the heat-carrying agent is circulated naturally between the external air cooler and the built-in heat exchanger. 6. The passive containment heat removal system according to claim 1, wherein a lower part of the air cooling channel (171) is open to form an air inlet of an air cooling channel (18), an air outlet of an air cooling channel (21) is formed on the outer wall of the outer containment (2), and the air cooling channel (171) is communicated with the air duct (200) via the air inlet (4) located below the lower part of the air cooling channel (171). 7. The passive containment heat removal system according to claim 1, wherein the air inlet (4) is located above an upper part of the air cooling channel (171), and the air inlet of the air cooling channel (18) and the air outlet of the air cooling channel (21) are formed on the chimney wall (17). 8. The passive containment heat removal system according to claim 1, wherein the air inlet (4) is adjacent to a lower part of the outer containment (2) to communicate the air cooling channel (171) with the air duct (200), and the air inlet of the air cooling channel (18) and the air outlet of the air cooling channel (21) are formed on the chimney wall (17). 9. The passive containment heat removal system according to claim 1, further comprising an expansion tank (22) with a first opening (221) and a second opening (222), wherein the expansion tank (22) is disposed in the inner containment (1), the first opening (221) is connected with the first communication pipe (13) via a venting pipe (24) and the second opening (222) is connected with the second communication pipe (14) via a connecting pipe (23). 10. The passive containment heat removal system according to claim 7, wherein a bottom surface of the expansion tank (22) is above the built-in heat exchanger (9) and the external air cooler (12). 11. The passive containment heat removal system according to claim 9, wherein the first communication pipe (13) comprises a first horizontal pipe segment (131) and a first vertical pipe section (132), and the external air cooler and the first horizontal pipe segment are aslant arranged with respect to a horizontal direction;the second communication pipe (14) comprises a second horizontal pipe section (141), a second vertical pipe section (142) and a third horizontal pipe section (143), and the built-in heat exchanger, the second horizontal pipe section (141) and the third horizontal pipe section (143) are aslant arranged with respect to a horizontal direction. 12. The passive containment heat removal system according to claim 1, further comprising:a condensate water collector (38) for collecting condensate water disposed in the inner containment (1) and located below the built-in heat exchanger (9), anda drainage pipe (39) connected with a drainage outlet of the condensate water collector (38). 13. The passive containment heat removal system according to claim 1, wherein a level of a top of the external air cooler (12) is above a level of a top of the built-in heat exchanger (9), and a level of a bottom of the external air cooler (12) is above a level of a bottom of the built-in heat exchanger (9). 14. The passive containment heat removal system according to claim 1, wherein the spray assembly (10) comprises:a water tank (6) disposed outside of the outer containment (2);a spray pipe (8) with a first end connected with the water tank (6) and a second end located on a top of the inner containment (1); anda spray valve (7) disposed at the spray pipe (8). 15. A method for controlling the passive containment heat removal system according to claim 1, comprising:the passive containment heat removal system as defined in claim 1; andtriggering automatically spraying of the cooling water to the outer wall of the inner containment to cool the inner containment by spraying and circulating naturally the heat-carrying agent between the inner containment and the outer containment to cool the inner containment when an accident happens. 16. The method for controlling the passive containment heat removal system according to claim 15, comprising:spraying the cooling water to the outer wall of the inner containment while circulating the heat-carrying agent naturally between the inner containment and the outer containment in order to reduce the amount of spraying water per unit time and extend the spraying time, andcooling the inner containment by the air flow in the air duct between the inner containment and the outer containment and by the heat-carrying agent circulated naturally between the inner containment and the outer containment after the cooling water is exhausted. 17. The method for controlling the passive containment heat removal system according to claim 15, comprising:circulating naturally the heat-carrying agent between the external air cooler and the built-in heat-exchanger during spraying the cooling water, andcooling the inner containment by the air flow in the air duct between the inner containment and the outer containment and by the heat-carrying agent circulated naturally between the inner containment and the outer containment after the cooling water is exhausted. 18. The method for controlling the passive containment heat removal system according to claim 15, comprising:circulating naturally the heat-carrying agent between the inner containment and the outer containment when the temperature and/or the pressure of the inner containment exceeds the designated threshold value during spraying the cooling water, andcooling the inner containment by the air flow in the air duct between the inner containment and the outer containment and by the heat-carrying agent circulated naturally between the inner containment and the outer containment after the cooling water is exhausted. 19. The method for controlling the passive containment heat removal system according to claim 15, comprising:cooling the inner containment by the air flow in the air duct between the inner containment and the outer containment after the cooling water is exhausted, andcirculating the heat-carrying agent naturally between the inner containment and the outer containment when the temperature and/or the pressure of the inner containment exceeds the designated threshold value during spraying the cooling water as well as after the cooling water is exhausted. 20. The passive containment heat removal system according to claim 1, further comprising a first drainage pipe (28) and a first drainage valve (27) disposed in the first drainage pipe (28), and a second drainage pipe (163) and a second drainage valve (16) disposed in the second drainage pipe (28), whereina first end of the first drainage pipe (28) is connected with the external air cooler (12), a second end of the first drainage pipe (28) is connected with the air duct (200), and the first drainage valve (27) comprises a first electric drainage valve and a first pneumatic drainage valve which are connected with each other in series;the second drainage pipe (163) is disposed in the inner containment (1) and connected with the second communication pipe (14), and the second drainage valve (16) comprises a second electric drainage valve and a second pneumatic valve which are connected with each other in series. 21. The passive containment heat removal system according to claim 1, wherein a first penetrating piece is disposed in a wall of the inner containment and a second penetrating piece is disposed in a wall of the outer containment, the first communication pipe and the second communication pipe pass through the first penetrating piece and the second penetrating piece and extend from the inner containment to an outside of the outer containment.