A top ventilation cooling system and cooling method for enhancing circulation

Abstract

The present invention relates to a top ventilation cooling system and a cooling method for enhancing circulation, which includes an outer cylinder of a reactor control rod drive mechanism. An air inlet is provided at the lower part of the outer cylinder, and an air outlet is provided at the top. The upper side of the outer cylinder is connected to a cooling air duct, and the other end of the cooling air duct is connected to a top ventilation structure for enhancing circulation; cold air enters the outer cylinder from the air inlet to cool the control rod. A part of the hot air flows out from the air outlet, and another part of the hot air flows out from the top ventilation structure through the cooling air duct. The present invention utilizes the top ventilation structure to form a negative pressure at the outlet of the cooling air duct to guide the hot air in the control rod drive mechanism to flow out quickly. The air flowing out from multiple sets of top ventilation structures forms rotating air after flowing out at a certain angle, creating a vortex low-pressure area at the top of the control rod drive mechanism, and further enhancing the outflow of the hot fluid in the control rod drive mechanism.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear reactor design, and particularly relates to a top ventilation cooling system and a cooling method for enhancing circulation. Background Art

[0002] The control rod drive mechanism is installed on the top cover of the reactor pressure vessel. During the normal operation of a nuclear power plant, the heat of the primary circuit of the reactor and the heat generated during the operation of the drive mechanism will cause the temperature inside the drive mechanism coil to rise. The M310 top structure ventilation cooling system consists of an exhaust fan, air ducts, ventilation hoods, air duct transition sections, enclosures, instruments, and electrical components. The M310 uses upward air intake, and the cooling air enters the yoke coil area of the control rod drive mechanism through the upper opening of the enclosure, is shunted inside the lower ventilation hood and enters four circumferentially arranged air ducts respectively, and then enters the exhaust duct through the air duct transition section and is discharged by the exhaust fan. The control rod drive mechanism cooling system of the AP1000 consists of a damper, a cylinder (including an internal enclosure), a fan, and an air duct. The cooling damper is located at the lower part of the cylinder, and 4 fans are installed on the cylinder. Together with 4 independent air ducts that do not need to be disassembled, the fan is used to forcibly cool the coil assembly and the rod position indicator assembly of the control rod drive mechanism to maintain the normal operation of the control rod drive mechanism. The reactor top of the HPR1000 reactor type is also provided with a control rod drive mechanism ventilation cooling system. At the position corresponding to the coil assembly of the control rod drive mechanism inside the lower cylinder of the HPR1000, a control rod drive mechanism cooling enclosure is provided. The cooling air duct is located inside the upper cylinder and is fixed to the inner wall of the cylinder by bolts. The cylinder, the cooling enclosure, the cooling air duct, and the external ventilation equipment together constitute the cooling system channel of the top control rod drive mechanism. The cooling fan (exhaust) is located in the annular corridor and is connected to the cooling air duct through an external exhaust duct. During operation, the hot air is extracted by the cooling fan to maintain the temperature inside the control rod drive mechanism within the limit value. However, the external exhaust duct of the HPR1000 control rod drive mechanism ventilation cooling system and its support occupy a large space, which has a certain impact on the passability of the plant; during the overhaul period, the disassembly and assembly of the air duct and the support are large in quantity, the disassembly and assembly operations are laborious, and it is not conducive to temporary storage. Considering that the coil temperature resistance level of the current new high-temperature resistant drive mechanism (ML-C type drive mechanism) reaches 440 °C, and the rod position detector reaches 220 °C, the drive mechanism already has the ability to operate for a long time under the condition of no forced ventilation. However, too high a temperature will affect the electrical insulation performance and the service life of the insulating material, especially the neutron measurement cable and the rod position measurement cable, whose temperature resistance limit value is relatively low (about 60 °C). Under normal operating conditions, the natural circulation method can be considered to export the hot air inside the drive mechanism. When the natural circulation ability is insufficient, the temperature inside the control rod drive mechanism is controlled within the limit value by forced circulation or enhancing the natural circulation method. Summary of the Invention

[0003] The object of the present invention is to provide a top ventilation cooling system and a cooling method for enhancing circulation to address the deficiencies in the prior art, strengthen the outflow of hot fluid in the control rod drive mechanism, and improve the safety of reactor operation.

[0004] The technical solution of the present invention is as follows: A top ventilation cooling system for enhancing circulation includes an outer cylinder of the reactor control rod drive mechanism. An air inlet is provided at the lower part of the outer cylinder, and an air outlet is provided at the top. The upper side of the outer cylinder is connected to a cooling air duct, and the other end of the cooling air duct is connected to a top ventilation structure for enhancing circulation; cold air enters the outer cylinder from the air inlet to cool the control rod. Part of the hot air flows out from the air outlet, and the other part of the hot air flows out from the top ventilation structure through the cooling air duct.

[0005] Further, in the top ventilation cooling system for enhancing circulation as described above, a cooling baffle is provided inside the outer cylinder, and an air flow channel is formed between the outer cylinder and the cooling baffle.

[0006] Further, as a specific embodiment of the top ventilation cooling system for enhancing circulation as described above, the top ventilation structure includes an air compression device, an air outlet duct, and a supply air duct for connecting the air compression device and the air outlet duct. The cooling air duct is communicated with the air outlet duct.

[0007] Furthermore, in the top ventilation cooling system for enhancing circulation as described above, the air outlet duct is of a double-wall structure, and a slit outlet is provided on the inner wall surface of the end connected to the supply air duct for discharging the compressed air from the air compression device at a higher speed.

[0008] Furthermore, in the top ventilation cooling system for enhancing circulation as described above, the air outlet duct can be in the shape of a flared mouth.

[0009] Further, as a specific embodiment of the top ventilation cooling system for enhancing circulation as described above, the top ventilation structure includes a rotary ventilation cap connected to the cooling air duct, and a cooling fan is provided on one side of the rotary ventilation cap.

[0010] Further, as a specific embodiment of the top ventilation cooling system for enhancing circulation as described above, the top ventilation structure includes an air compression device, an ejector, and a supply air duct for connecting the air compression device and the ejector. The cooling air duct is communicated with the ejector.

[0011] Further, in the top ventilation cooling system for enhancing circulation as described above, multiple sets of the same top ventilation structures are evenly arranged circumferentially around the control rod drive mechanism, and the air blown out by the multiple sets of top ventilation structures forms a vortex low-pressure area at the top of the control rod drive mechanism.

[0012] Furthermore, for the top ventilation and cooling system for enhancing circulation as described above, the angle formed by the air outlet direction of the top ventilation structure and the central coordinate axis of the control rod drive mechanism is between 110° and 160°.

[0013] A cooling method for the top ventilation and cooling system for enhancing circulation as described above. Under normal operating conditions, without starting the air compression device or cooling fan of the top ventilation structure, the outer cylinder, cooling shroud, cooling air duct, and top ventilation structure jointly form a natural circulation cooling system channel for the control rod drive mechanism; when it is found that the natural circulation capacity is insufficient by monitoring the air volume at the inlet of the control rod drive mechanism, start the air compression device or cooling fan of the top ventilation structure, and rely on the drainage effect to enhance the circulation cooling capacity of the control rod drive mechanism at the top of the reactor, and by controlling the air outlet direction of multiple sets of top ventilation structures, a swirling low-pressure area is formed at the top of the control rod drive mechanism to further enhance the natural circulation capacity.

[0014] The beneficial effects of the present invention are as follows: The present invention uses the top ventilation structures in various design forms to form a negative pressure at the outlet of the cooling air duct, guiding the hot air in the control rod drive mechanism to flow out quickly. At the same time, the air flowing out of multiple sets of top ventilation structures forms rotating air after flowing out at a certain angle, creating a negative pressure above the air outlet at the top of the control rod drive mechanism and the gaps of the anti-seismic structure at the top of the control rod drive mechanism, further enhancing the outflow of the hot fluid in the control rod drive mechanism and keeping the control rod drive mechanism and its auxiliary facilities within the allowable temperature range. By using compressed air, the air supply pipeline can be designed as a thin pipeline with a small floor area, which is convenient for disassembly and storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic structural diagram of an embodiment of the top ventilation and cooling system for enhancing circulation of the present invention;

[0016] Figure 2-1 It is a cross-sectional view of the air outlet pipe in the top ventilation structure of the present invention;

[0017] Figure 2-2 is Figure 2-1 the developed view of;

[0018] Figure 3 It is a schematic diagram of the angular arrangement of multiple sets of top ventilation structures of the present invention;

[0019] Figure 4 It is a schematic structural diagram of a second embodiment of the top ventilation and cooling system for enhancing circulation of the present invention;

[0020] Figure 5 It is a schematic structural diagram of a third embodiment of the top ventilation and cooling system for enhancing circulation of the present invention.

[0021] In the figure, 1 - air compression device (compressed air bag or air compressor), 2 - air outlet pipe, 3 - air supply pipe, 4 - cooling air pipe, 5 - outer cylinder, 6 - cooling baffle, 7 - air inlet, 8 - air outlet, 9 - control rod, 10 - slit outlet, 11 - cooling fan, 12 - rotary ventilation cap, 13 - ejector, 14 - control rod drive mechanism. Specific embodiments

[0022] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] Embodiment 1

[0024] This embodiment provides a top ventilation and cooling system for enhancing circulation, as Figure 1 shown, including the outer cylinder 5 of the reactor control rod drive mechanism. The lower part of the outer cylinder 5 is provided with an air inlet 7, and the top is provided with an air outlet 8. A cooling baffle 6 is arranged inside the outer cylinder 5. An air flow passage is formed between the outer cylinder 5 and the cooling baffle 6. The upper side of the outer cylinder 5 is connected to the cooling air pipe 4, and the other end of the cooling air pipe 4 is connected to the top ventilation structure for enhancing circulation. The top ventilation structure includes a compressed air bag (or air compressor) 1, an air outlet pipe 2, and an air supply pipe 3 for connecting the compressed air bag (or air compressor) 1 and the air outlet pipe 2. Cold air enters the outer cylinder 5 from the air inlet 7 to cool the control rod 9. Part of the hot air flows out from the air outlet 8, and the other part of the hot air flows out from the top ventilation structure through the cooling air pipe 4. The compressed air bag (or air compressor) 1 of the top ventilation structure relies on the drainage effect to enhance the natural circulation cooling capacity of the top control rod drive mechanism.

[0025] As Figure 2-1 , 2-2 shown, the air outlet pipe 2 of the top ventilation structure can be a normal opening or a flared shape. The air outlet pipe 2 is a double-wall structure, and there is a certain gap between the inner wall surface and the outer wall surface. One end of the air outlet pipe 2 connected to the air supply pipe 3 is provided with a slit outlet 10 on the inner wall surface. This outlet can make the flowing air stable and continuous through streamline design, and is used to flow out the compressed air generated by the compressed air bag (or air compressor) 1 at a higher flow rate. The compressed air flowing out from the slit outlet 10 has a higher speed and entrains the surrounding fluid, which will form a low pressure at the outlet of the air supply pipe 3, thereby enhancing the gas flow in the control rod drive mechanism.

[0026] A plurality of identical sets (four sets or three sets) of top ventilation structures can be evenly arranged along the circumferential direction of the control rod drive mechanism. As Figure 3As shown in the figure, four sets of top ventilation structures are arranged in this embodiment. The air outlet direction of the top ventilation structure is arranged at an angle with the coordinate axis passing through the center, so that the air blown out from the air outlet pipes 2 of the four sets of top ventilation structures forms a vortex, which can form a low-pressure area above the top outlet of the control rod drive mechanism 14, and further enhance the gas flow in the control rod drive mechanism. Specifically, the angle formed by the air outlet direction of the top ventilation structure and the central coordinate axis of the control rod drive mechanism can vary between 110° - 160° (the supplementary angle is 20° - 70°), as long as a vortex can be formed.

[0027] Under normal operating conditions, cold air enters the inside of the control rod drive mechanism from the air inlet 7. The heated cold air flows upward between the cooling air ducts between the cooling shroud 6 and the outer cylinder 5 and the gaps of the control rods 9. A part of the hot air flows out from the top outlet 8, and another part of the hot air flows out from the cooling air pipe 4. The hot air flowing out from the cooling pipe 4 flows out from the outlet of the air outlet pipe 2 of the top ventilation structure at a certain angle. The outlet air of the four sets (or three sets) of top ventilation structures forms a vortex at a certain angle, reducing the pressure at the top outlet 8 and further enhancing the natural circulation ability.

[0028] By monitoring the air volume at the inlet of the control rod drive mechanism, when the natural circulation ability is insufficient, the compression airbag (or air compressor) 1 starts. Compressed air flows through the air supply pipe 3 to the air outlet pipe 2 and flows out through the slit outlet 10 of the air outlet pipe 2. The air flowing out from the slit outlet 10 has a very high flow rate, forming a negative pressure at the outlet of the cooling air pipe 4, guiding the hot air in the control rod drive mechanism to flow out. At the same time, the air flowing out from the slit outlet 10 is mixed with the air diverted from the cooling air pipe 4 and flows out from the outlet of the air outlet pipe 2 of the top ventilation structure at a certain angle. The outlet air of the four sets (or three sets) of top ventilation structures forms a vortex at a certain angle, reducing the pressure at the top outlet 8 and further enhancing the natural circulation ability.

[0029] Embodiment 2

[0030] This embodiment provides a top ventilation cooling system for enhancing circulation, as Figure 4As shown in the figure, it includes an outer cylinder 5 of the reactor control rod drive mechanism. An air inlet 7 is provided at the lower part of the outer cylinder 5, and an air outlet is provided at the top. A cooling baffle 6 is provided inside the outer cylinder 5. An air flow passage is formed between the outer cylinder 5 and the cooling baffle 6. The upper side of the outer cylinder 5 is connected to a cooling air duct 4, and the other end of the cooling air duct 4 is connected to a top ventilation structure for enhancing circulation. The top ventilation structure includes a rotary ventilation cap 12 connected to the cooling air duct 4, and a cooling fan 11 is provided on one side of the rotary ventilation cap 12. Cold air enters the outer cylinder 5 from the air inlet 7 to cool the control rod 9. Part of the hot air flows out from the air outlet, and the other part of the hot air flows out from the top ventilation structure through the cooling air duct 4. The cold air sent out by the cooling fan 11 of the top ventilation structure, or the incoming air from different directions, will drive the rotary ventilation cap 12 to rotate, thereby enhancing the gas circulation in the control rod drive mechanism.

[0031] Embodiment III

[0032] This embodiment provides a top ventilation cooling system for enhancing circulation, as Figure 5 shown in the figure, it includes an outer cylinder 5 of the reactor control rod drive mechanism. An air inlet 7 is provided at the lower part of the outer cylinder 5, and an air outlet is provided at the top. A cooling baffle 6 is provided inside the outer cylinder 5. An air flow passage is formed between the outer cylinder 5 and the cooling baffle 6. The upper side of the outer cylinder 5 is connected to a cooling air duct 4, and the other end of the cooling air duct 4 is connected to a top ventilation structure for enhancing circulation. The top ventilation structure includes a compression air bag (or air compressor) 1, an ejector 13, and an air supply duct 3 for connecting the compression air bag (or air compressor) 1 and the ejector 13. The cooling air duct 4 is communicated with the ejector 13. Cold air enters the outer cylinder 5 from the air inlet 7 to cool the control rod 9. Part of the hot air flows out from the air outlet 8, and the other part of the hot air flows out from the top ventilation structure through the cooling air duct 4.

[0033] Under normal operating conditions, cold air enters the inside of the control rod drive mechanism from the air inlet 7. The heated cold air flows upward between the cooling air duct between the cooling baffle 6 and the outer cylinder 5 and the gap of the control rod 9. Part of the hot air flows out from the top outlet 8, and the other part of the hot air flows out from the cooling air duct 4. The hot air flowing out from the cooling duct 4 flows out at a certain angle from the outlet of the ejector 13 of the top ventilation structure. The outlet air of multiple sets of top ventilation structures forms a vortex at a certain angle, reducing the pressure at the top outlet 8 and further enhancing the natural circulation ability.

[0034] By monitoring the inlet air volume of the control rod drive mechanism, when the natural circulation capacity is insufficient, the compression airbag (or air compressor) 1 of the reactor top ventilation structure relies on the drainage effect to enhance the natural circulation cooling capacity of the control rod drive mechanism at the reactor top. Since the air supply pipe 3 has a small diameter, the compressed gas from the compression airbag flows out at a high speed from the outlet of the air supply pipe 3, forming a low-pressure vortex in the ejector 13, thereby enhancing the outflow of the fluid in the control rod drive mechanism from the self-cooling air pipe 4. The outlet air of multiple sets of reactor top ventilation structures forms a vortex at a certain angle, reducing the pressure at the top outlet 8 and further enhancing the natural circulation capacity.

[0035] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0036] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A top ventilation cooling system for enhancing circulation, characterized in that, it includes an outer cylinder (5) of the reactor control rod drive mechanism. An air inlet (7) is provided at the lower part of the outer cylinder (5), and an air outlet (8) is provided at the top. A cooling air duct (4) is connected to the upper side of the outer cylinder (5). The other end of the cooling air duct (4) is connected to the top ventilation structure for enhancing circulation; cold air enters the outer cylinder (5) from the air inlet (7) to cool the control rod (9). Part of the hot air flows out from the air outlet (8), and the other part of the hot air flows out from the top ventilation structure through the cooling air duct (4); A plurality of identical top ventilation structures are uniformly arranged circumferentially around the control rod drive mechanism, and the air blown out by the plurality of top ventilation structures forms a vortex low-pressure area at the top of the control rod drive mechanism.

2. The top ventilation cooling system for enhancing circulation according to claim 1, characterized in that, a cooling baffle (6) is provided inside the outer cylinder (5), and an air flow channel is formed between the outer cylinder (5) and the cooling baffle (6).

3. The top ventilation cooling system for enhancing circulation according to claim 1 or 2, characterized in that, the top ventilation structure includes an air compression device (1), an air outlet duct (2), and an air supply duct (3) for connecting the air compression device (1) and the air outlet duct (2). The cooling air duct (4) is communicated with the air outlet duct (2).

4. The top ventilation cooling system for enhancing circulation according to claim 3, characterized in that, the air outlet duct (2) is of a double-wall structure, and a slit outlet (10) is provided on the inner wall surface at one end connected to the air supply duct (3) for discharging the compressed air from the air compression device (1) at a higher speed.

5. The top ventilation cooling system for enhancing circulation according to claim 4, characterized in that, the air outlet duct (2) is in the shape of a flared mouth.

6. The top ventilation cooling system for enhancing circulation according to claim 1 or 2, characterized in that, the top ventilation structure includes a rotary ventilation cap (12) connected to the cooling air duct (4), and a cooling fan (11) is provided on one side of the rotary ventilation cap (12).

7. The top ventilation cooling system for enhancing circulation according to claim 1 or 2, characterized in that, the top ventilation structure includes an air compression device (1), an ejector (13), and an air supply duct (3) for connecting the air compression device (1) and the ejector (13). The cooling air duct (4) is communicated with the ejector (13).

8. The top ventilation cooling system for enhancing circulation according to claim 1, characterized in that, the angle formed by the air outlet direction of the top ventilation structure and the central coordinate axis of the control rod drive mechanism is between 110° and 160°.

9. A cooling method for the top ventilation cooling system for enhancing circulation according to any one of claims 1-8, characterized in that, Under normal operating conditions, the air compression device or cooling fan of the top ventilation structure does not need to be started. The outer cylinder, cooling shroud, cooling air duct and top ventilation structure together form the channel of the natural circulation cooling system of the control rod drive mechanism. When it is found that the natural circulation capacity is insufficient by monitoring the air volume at the inlet of the control rod drive mechanism, the air compression device or cooling fan of the top ventilation structure is started. Relying on the drainage effect, the circulating cooling capacity of the control rod drive mechanism at the top is enhanced. And through the control of the air outlet direction of multiple sets of top ventilation structures, a vortex low-pressure area is formed at the top of the control rod drive mechanism to further enhance the natural circulation capacity.

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