1. Technical Field
The present invention relates to a nuclear reactor containment vessel of a nuclear power generation plant.
2. Description of Related Art
Patent Literature 1 (JP-A-5-256977) discloses a technique relating to an emergency gas processing equipment of a nuclear power station. Specifically, a hollow structure covering a nuclear reactor containment vessel is provided, a side suction port and an upper discharge port are disposed in the hollow structure, and a filter is attached to the upper discharge port. At the time of an accident, heated air is generated by decay heat conducted to the hollow structure from the nuclear reactor containment vessel, and air flow is generated by the heated air. The heated air is discharged to the outside of the hollow structure by the air flow.
Since the driving force due to buoyancy is very small as compared with a case where a dynamic device such as a pump is used, it is required to reduce pressure loss of air flow as much as possible. However, in the emergency gas processing equipment disclosed in Patent Literature 1, the sectional area of an air flow path of an annulus part is reduced toward an upper part of the containment vessel. Thus, the air flow speed increases, and the acceleration loss due to air acceleration increases. Accordingly, there is a problem that the cooling performance of the containment vessel is reduced since the acceleration loss due to the air acceleration increases.
An object of the invention is to improve the cooling performance of a containment vessel.
According to the invention, an air flow path is provided vertically above an air-cooled heat exchanger.
According to the invention, the cooling performance of the containment vessel is improved.
Hereinafter, embodiments will be described with reference to the drawings.
In order to facilitate understanding of this embodiment, a comparative example of a nuclear reactor containment vessel cooling equipment of a nuclear power generation plant will be described.
If an accident occurs in which steam is discharged from a nuclear reactor pressure vessel 10 into the nuclear reactor containment vessel 2 and the temperature of the nuclear reactor containment vessel abnormally rises, the heat in the containment vessel is transmitted through the containment vessel 2 to air 8 in the annulus part 7. A specific gravity difference occurs between the heated air and the atmosphere, and buoyancy is generated. The heated air is discharged to the atmosphere through the upper discharge port 5, and new air flows into the annulus part 7 through the side suction port 4. That is, cooling by natural ventilation can be achieved without using a dynamic device. At this time, driving force F (Pa) obtained when the air 8 in the annulus part 7 rises by the buoyancy can be calculated by the following expression.
F=ΔμgH (1)
Where, Δρ(kg/m3) is a density difference between the heated air and the atmosphere, g(m/s2) is a gravity acceleration, and H(m) is an effective height. If the containment vessel 2 is a heat transfer surface, the air 8 of the annulus part flowing in from the side suction port 4 is gradually heated by the whole surface of the containment vessel. Thus, the effective height H is about ½ of a height difference between the side suction port 4 and the upper discharge port 5.
Besides, as shown in
Since the air flowing in from the side inflow port 4 is immediately heated by the air-cooled heat exchanger 9, the effective height H in the expression (1) is a height difference between the air-cooled heat exchanger 9 and the upper discharge port 5, and the driving force F of the air 8 of the annulus part due to the buoyancy can be more improved. Dimensionless heat transfer coefficient Nu(−) representing the cooling performance of air cooling is obtained by the following Dittus-Boelter expression.
Nu=0.023Re0.8Pr0.4 (2)
Where, Re(−) is Raynolds number and is proportional to a flow speed in an identical system. Pr(−) is Prandtl number and is a physical property value determined by the kind of working fluid. Since the cooling performance of the air cooling increases in proportion to 0.8 power of the flow speed from the expression (2), if the flow driving force F is improved by installing the air-cooled heat exchanger 9 and the flow speed is increased, the cooling performance of the equipment can be more improved.
When the air-cooled heat exchanger 9 is used in order to increase the driving force for causing the air of the annulus part 7 to rise, since an air flow path sectional area of the annulus part is reduced toward an upper part of the containment vessel, the acceleration loss increases. Besides, for maintenance of the air-cooled heat exchanger, a take-out port and a take-out mechanism of the air-cooled heat exchanger 9 are required to be provided in the vicinity of the side suction port 4. Thus, there is a problem that the structure becomes complicated and the cost increases. Since an air-cooling heat transfer coefficient is smaller by several hundred times than a boiling-condensation heat transfer coefficient, the air-cooled heat exchanger 9 is large as compared with a general heat exchanger using boiling-condensation heat transfer of steam. Accordingly, it is difficult to provide the take-out port of the large heat exchanger in the hollow structure 3.
Since the sectional area of the bypass air flow path 12 is larger than the sectional area of the air-cooled heat exchanger when seen from above, at the time of maintenance of the air-cooled heat exchanger 9, the bypass air flow path 12 can be used as a removing port when the air-cooled heat exchanger 9 is lifted by a cable 13 attached to a tip of a crane 14. At the time of maintenance of the air-cooled heat exchanger 9, the air-cooled heat exchanger 9 and a connection pipe of the containment vessel are separated, and the heat exchanger 9 is lifted by the crane 14. The air-cooled heat exchanger 9 is taken out to the outside through the bypass air flow path 12. After the maintenance, the air-cooled heat exchanger 9 is installed at a specified position of the annulus part by using the crane 14. Since the bypass air flow path 12 is used as the removing port of the air-cooled heat exchanger 9, a take-out port and a take-out mechanism in the vicinity of the side suction port 4 become unnecessary, and the cost of installation of the air-cooled heat exchanger 9 can be reduced.
At the time of maintenance of the air-cooled heat exchanger 9, the air flow path 12a can be used as a removing port when the air-cooled heat exchanger 9 is lifted by a cable 13 attached to a tip of a crane 14. At the time of maintenance of the air-cooled heat exchanger 9, the air-cooled heat exchanger 9 and a connection pipe of the containment vessel are separated, and the air-cooled heat exchanger 9 is lifted by the crane 14. The air-cooled heat exchanger 9 is taken out to the outside through the air flow path 12a. After the maintenance, the air-cooled heat exchanger 9 is installed at a specified position of the annulus part by using the crane 14. Since the air flow path 12a is used as the removing port of the air-cooled heat exchanger 9, a take-out port and a take-out mechanism in the vicinity of a side suction port 4 are unnecessary, and the cost of installation of the air-cooled heat exchanger 9 can be reduced.
At the time of maintenance of the air-cooled heat exchanger 9, the air flow path 12b can be used as a removing port when the air-cooled heat exchanger 9 is lifted by a cable 13 attached to a tip of a crane 14. At the time of maintenance of the air-cooled heat exchanger 9, the air-cooled heat exchanger 9 and a connection pipe of the containment vessel are separated, and the heat exchanger 9 is lifted by the crane 14. The air-cooled heat exchanger 9 is taken out to the outside through the air flow path 12b. After the maintenance, the air-cooled heat exchanger 9 is installed at a specified position of the air flow path by using the crane 14. Since the air flow path 12b is used as the removing port of the air-cooled heat exchanger 9, a take-out port and a take-out mechanism in the vicinity of the side suction port 4 are unnecessary, and the cost of installation of the air-cooled heat exchanger 9 can be reduced.
Number | Date | Country | Kind |
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2014-009082 | Jan 2014 | JP | national |