Reactor top air supply cooling system

Abstract

The invention relates to the technical field of pressurized water type nuclear reactor top structures, and provides a reactor top air supply cooling system which comprises a shroud which surrounds a control rod driving mechanism and forms a cooling ventilation flow channel, and further comprises a separated air supply pipeline, an air inlet is formed in the bottom of the shroud, and an air outlet is formed in the top of the shroud. The inlet end of the separated air supply pipeline is installed on the top of the reactor pit, the outlet end of the separated air supply pipeline is opposite to the air inlet, and a gap is reserved between the outlet end of the separated air supply pipeline and the air inlet. Compared with the prior art, air flow is changed from air draft to air supply, a connecting structure between an air pipe and the shroud is omitted, meanwhile, it is guaranteed that most of cooling air enters the shroud, the situation that the reactor refueling and maintenance cycle is prolonged due to disassembly and assembly of the connecting structure is avoided, and the situation that the reactor top structure is complex and the cost is low due to the fact that a draught fan is directly installed on the shroud is also avoided. And risks caused by the fact that fan vibration directly acts on the reactor are avoided.

Description

Technical Field

[0001] The invention relates to the technical field of pressurized water nuclear reactor top structures, and in particular to a reactor top air supply cooling system. Background Art

[0002] The reactor top structure is one of the important components of the reactor. One of its main functions is to remove the heat generated by the control rod drive mechanism (CRDM) coil with the help of cooling air to ensure that the CRDM temperature does not exceed the limit. The CRDM is an important component that drives the movement of the control rod assembly and accurately adjusts the reactivity changes in the reactor. It has important safety functions such as reactor startup, power increase, power maintenance, load tracking, normal shutdown and emergency shutdown. Nuclear reactor operation experience and related research have shown that the main factors affecting the life and working performance of the control rod drive mechanism are operating temperature, working pressure and working load. If there is no appropriate cooling measure, the temperature of the control rod drive mechanism coil may exceed the maximum temperature that the coil in the coil assembly can withstand, which will cause the function of the coil assembly to degrade or fail, and even cause the coil to burn. Therefore, ensuring that the CRDM operates within the temperature limit is crucial to ensuring the safety and stable operation of the reactor.

[0003] At present, the ventilation cooling system in the existing stack top structure mainly uses a fan to force air extraction, so that the cooling air passes through the surface of the drive mechanism to take away the heat. There are two main types of structural forms: one is the duct connection type exhaust cooling system, such as Figure 1 As shown, the fan is arranged in a room of the reactor building (not shown), and is connected to the shroud 7 through the exhaust pipe 9 for exhaust. The main problem is that each time the reactor is refueled or repaired, the connection structure between the exhaust pipe 9 and the shroud 7 needs to be removed. This operation takes a long time and is located on the main line of the reactor disassembly and assembly, which increases the reactor refueling or maintenance cycle, reduces the effective operation time of the reactor, and reduces the economic efficiency of the reactor. The other is a fan direct-connected exhaust cooling system, such as Figure 2 As shown, the direct-connected exhaust fan 11 is directly installed on the shroud 7. The direct-connected exhaust fan 11 is hoisted together with the reactor top structure. There is no need to dismantle the connection structure between the exhaust pipe 9 and the shroud 7, which saves the material replacement or maintenance cycle. However, the main problem of this solution is that the direct-connected exhaust fan 11 is directly installed on the shroud 7, which greatly increases the complexity of the reactor top structure, and also greatly increases the weight and volume, and increases the difficulty of disassembly and maintenance of the reactor top structure. At the same time, the vibration of the fan also directly acts on the reactor, which brings risks to the reactor structure. Summary of the invention

[0004] The object of the present invention is to provide a reactor top air supply cooling system to solve the above-mentioned defects of the prior art.

[0005] The present invention is achieved through the following technical solutions:

[0006] A reactor top air supply cooling system includes a casing, which surrounds a control rod drive mechanism and forms a cooling ventilation channel, and also includes a separate air supply pipeline. An air inlet is provided at the bottom of the casing, and an air outlet is provided at the top of the casing. The inlet end of the separate air supply pipeline is installed on the top of the reactor pit, and the outlet end of the separate air supply pipeline is opposite to the air inlet, and a gap is left between the outlet end of the separate air supply pipeline and the air inlet.

[0007] Optionally, the size of the outlet of the separated air supply duct is exactly the same as the size of the air inlet.

[0008] Optionally, the height of the center of the outlet of the separate air supply pipeline is greater than the height of the center of the air inlet, so as to compensate for the expansion of the air inlet position in the height direction when the reactor is running.

[0009] Optionally, the gap is 500 mm.

[0010] Optionally, there is one air inlet and a plurality of air outlets are provided along the circumferential direction.

[0011] Optionally, a cable channel is provided on the outer wall of the enclosure, and a heat insulating gasket is provided between the cable channel and the enclosure.

[0012] Optionally, the coil of the control rod drive mechanism can withstand a temperature greater than or equal to 400°C.

[0013] Optionally, the cooling air transported by the separate air supply duct has a target flow rate and pressure, and the temperature of the cooling air is lower than the temperature of the air near the enclosure.

[0014] The technical solution of the present invention has at least the following advantages and beneficial effects: In the present invention, cooling air is transported through a separate air supply pipeline, the cooling air enters the interior of the shroud from the air inlet, cools the control rod drive mechanism, and flows out from the air outlet after the cooling air is heated. Compared with the prior art, the air flow is changed from exhaust to supply, and the connection structure between the air duct and the shroud is eliminated, while ensuring that most of the cooling air enters the interior of the shroud, avoiding disassembly of the connection structure to increase the reactor refueling and maintenance cycle, and also avoiding the fan being directly installed on the shroud to cause a complex top structure, and avoiding the risk of the fan vibration directly acting on the reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 It is a schematic diagram of the structure of the air duct connection type exhaust cooling system in the prior art;

[0017] Figure 2 It is a schematic diagram of the structure of a fan direct-connected exhaust cooling system in the prior art;

[0018] Figure 3 A schematic structural diagram of a reactor top air supply cooling system provided by the present invention;

[0019] Figure 4 It is a schematic diagram of cooling air flow;

[0020] Icons: 1-separated air supply duct, 2-air outlet, 3-cable channel, 4-pressure vessel top cover, 5-reactor pit, 6-control rod drive mechanism, 7-container, 8-air inlet, 9-exhaust duct, 10-connection structure, 11-direct-connected exhaust fan. DETAILED DESCRIPTION

[0021] refer to Figure 3 A reactor top air supply cooling system includes a shroud 7 and a separate air supply pipeline 1. In actual application, the shroud 7 is installed on the pressure vessel top cover 4 by bolts. The shroud 7 surrounds the control rod drive mechanism 6 inside and forms a cooling ventilation flow channel. An air inlet 8 is provided at the bottom of the shroud 7, and an air outlet 2 is provided at the top of the shroud 7. The inlet end of the separate air supply pipeline 1 is installed at the top of the reactor pit 5, and the outlet end of the separate air supply pipeline 1 is opposite to the air inlet 8, that is, the separate air supply pipeline 1 is introduced from the top of the reactor pit 5, sinks along the pit wall to the position of the air inlet 8 of the shroud 7, and a gap is left between the outlet end of the separate air supply pipeline 1 and the air inlet 8. Preferably, the gap is 500 mm, leaving space for the top structure to move up and down for reactor refueling or maintenance.

[0022] During operation, cooling air is transported through the separate air supply pipeline 1, and the cooling air enters the interior of the shroud 7 from the air inlet 8 to cool the control rod drive mechanism 6. The cooling air flows out from the air outlet 2 after being heated. Compared with the prior art, the air flow is changed from exhaust to supply, and the connecting structure 10 between the air duct and the shroud 7 is eliminated. At the same time, it is ensured that most of the cooling air enters the interior of the shroud 7, avoiding the disassembly and assembly of the connecting structure 10 to increase the reactor refueling and maintenance cycle, and also avoiding the fan being directly installed on the shroud 7 to cause a complex top structure, and avoiding the risk of the fan vibration directly acting on the reactor.

[0023] The cooling air delivered by the separate air supply pipeline 1 has a certain flow rate and pressure to ensure that most of the cooling air can be smoothly pushed into the enclosure 7. The temperature of the cooling air is lower than the temperature of the air near the enclosure 7, preferably, the temperature of the cooling air is 16°C.

[0024] The size of the outlet of the separated air supply duct 1 is exactly the same as the size of the air inlet 8. Furthermore, the height of the center of the outlet of the separated air supply duct 1 is greater than the height of the center of the air inlet 8, so as to compensate for the expansion of the air inlet 8 in the height direction when the reactor is running. On this basis, it is easy to understand that in actual applications, the height difference between the center of the outlet of the separated air supply duct 1 and the center of the air inlet 8 is determined according to the actual expansion of the air inlet 8 in the height direction.

[0025] In this embodiment, only one air inlet 8 is provided, and multiple air outlets 2 are provided along the circumferential direction to ensure that the cooling air flows upward after entering the shroud 7 (such as Figure 4 As shown), it is used to cool the drive mechanism. As an option, in this embodiment, eight air outlets 2 are provided along the circumferential direction.

[0026] It is worth noting that, with the structure provided by the present invention, there is only the control rod drive mechanism 6 inside the shroud 7, and the cooling shroud and the air duct between the shroud 7 and the control rod drive mechanism 6 in the prior art can be eliminated. Since the cooling shroud and the air duct inside the shroud 7 are eliminated, the uniformity of the air flow through each group of control rod drive mechanisms 6 is reduced. In order to reduce the requirements for the air volume of the cooling air supply system, the control rod drive mechanism 6 is a high-temperature resistant drive mechanism, and the temperature that its coil can withstand is greater than or equal to 400°C. The use of a high-temperature resistant drive mechanism improves the temperature resistance level of the drive mechanism and reduces the demand for the air volume of the cooling air supply system.

[0027] The outer wall of the shroud 7 is provided with a cable channel 3 for laying the in-pile measurement cable led out from the pressure vessel top cover 4. On this basis, a heat insulating gasket (not shown) is provided between the cable channel 3 and the shroud 7 to prevent the cable from aging rapidly due to high temperature. The thickness of the heat insulating gasket is determined according to the heat insulating effect of its material, and the preferred value is 20 mm.

[0028] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A reactor top air supply cooling system, comprising a shroud, which surrounds a control rod drive mechanism and forms a cooling ventilation channel, characterized in that: It also includes a separate air supply duct, an air inlet is provided at the bottom of the enclosure, an air outlet is provided at the top of the enclosure, the inlet end of the separate air supply duct is installed at the top of the reactor pit, the outlet end of the separate air supply duct is opposite to the air inlet, and a gap is left between the outlet end of the separate air supply duct and the air inlet.

2. The reactor top air supply cooling system according to claim 1, characterized in that: The size of the outlet of the separated air supply pipeline is exactly the same as the size of the air inlet.

3. The reactor top air supply cooling system according to claim 2, characterized in that: The height of the center of the outlet of the separate air supply pipeline is greater than the height of the center of the air inlet, so as to compensate for the expansion of the air inlet position in the height direction when the reactor is running.

4. The reactor top air supply cooling system according to any one of claims 1 to 3, characterized in that: The gap is 500 mm.

5. The reactor top air supply cooling system according to any one of claims 1 to 3, characterized in that: There is one air inlet, and there are multiple air outlets along the circumferential direction.

6. The reactor top air supply cooling system according to any one of claims 1 to 3, characterized in that: The outer wall of the enclosure is provided with a cable channel, and a heat insulating gasket is provided between the cable channel and the enclosure.

7. The reactor top air supply cooling system according to any one of claims 1 to 3, characterized in that: The coil of the control rod drive mechanism can withstand a temperature greater than or equal to 400°C.

8. The reactor top air supply cooling system according to any one of claims 1 to 3, characterized in that: The cooling air transported by the separate air supply pipeline has a target flow rate and pressure, and the temperature of the cooling air is lower than the temperature of the air near the enclosure.

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