A passive cooling system for the core of a pressurized water reactor nuclear power plant after an accident

Abstract

The invention discloses a passive cooling system for a core of a pressurized water reactor nuclear power plant after an accident, relates to the technical field of nuclear power plant safety, solves the problem that the existing passive cooling system cannot effectively cool the containment in winter in cold areas, and improves safety. The specific scheme is as follows: it comprises a shielding building, a containment arranged in the shielding building, and a pressure vessel arranged in the containment, a cooling water distribution plate is fixedly arranged at the middle position of the top of the containment, a cooling water tank connected to the cooling water distribution plate and an air flow channel penetrating the top of the shielding building are arranged on the top of the shielding building, a plurality of air inlets are arranged on the cylinder of the shielding building, a heat conducting plate is arranged on the periphery of the containment, a heat conducting plate contains a heat transfer medium and a partition for heat insulation, a space allowing air to pass through is provided between the lower end of the heat conducting plate and the bottom of the shielding building, the top of part of the heat conducting plate is fixedly connected to the top inner wall of the shielding building and is provided with a gas channel, and the top of part of the heat conducting plate extends into the cooling water tank.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear power plant safety, and in particular to a passive cooling system for a core of a pressurized water reactor nuclear power plant after an accident. Background Art

[0002] The third-generation passive nuclear power technology represented by AP1000 adopts a passive core cooling device. A smoke window is provided at the central top of the conical shielding building, and an annular water tank is provided above the shielding building and around the smoke window. A cooling water distribution plate is provided in the middle of the shielding building on the top of the steel containment, and the cooling water distribution plate is suspended on a hanging ring. A spray water pipe is provided on the top of the shielding building, and the water inlet end of the spray water pipe is connected to the bottom of the water tank, and the water outlet end of the spray water pipe extends to above the cooling water distribution plate. A through air inlet is opened at the upper end of the outer wall of the shielding building, and a heat conduction plate is provided between the shielding building and the steel containment, and the upper end of the heat conduction plate is connected to the top of the shielding building.

[0003] The inventors found that the above-mentioned existing passive cooling system (CN103377729A--Complete passive cooling system for core after accident of large pressurized water reactor nuclear power plant) can maintain the safety of core without relying on operator operation within 72 hours after the accident. However, the simple setting of heat conduction plate cannot achieve continuous cooling of containment. External water replenishment 72 hours after the accident depends on external operation. In winter in cold areas, the water in the water tank on the top of the containment will freeze, resulting in the inability of the containment spray water pipe to operate normally. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a passive cooling system for the core of a pressurized water reactor nuclear power plant after an accident. A heat conducting plate with heat exchange and heat insulation capabilities is arranged on the surrounding side of the containment, and part of the heat conducting plate is extended into the cooling water tank. The heat transferred by the heat conducting plate is used to heat the frozen area, thereby solving the problem that the existing passive cooling system cannot effectively cool the containment in cold areas in winter.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] In the first aspect, the present invention provides a passive cooling system for the core of a pressurized water reactor nuclear power plant after an accident, comprising a shielding building, a containment shell arranged in the shielding building, and a pressure vessel arranged in the containment shell, a cooling water distribution plate is fixedly provided at a middle position on the top of the containment shell, a cooling water tank connected to the cooling water distribution plate and an air flow channel running through the top of the shielding building are provided on the top of the shielding building, a plurality of air inlets are provided on the cylinder of the shielding building, a heat conducting plate is provided on the periphery of the containment shell, the heat conducting plate contains a heat transfer medium and a partition for heat insulation, a space allowing air to pass between the lower end of the heat conducting plate and the bottom of the shielding building, the top of some heat conducting plates is fixedly connected to the top inner wall of the shielding building and is provided with a gas channel, and the top of some heat conducting plates extends into the cooling water tank.

[0007] As a further implementation, the cooling water tank is located above the cooling water distribution plate and is connected to the cooling water distribution plate through a cooling water pipe, and the heat conduction plate in the cooling water tank is close to the cooling water pipe.

[0008] As a further implementation, the heat conducting plate is located between the inner wall of the shielding building and the containment vessel.

[0009] As a further implementation method, the interior of the heat conductive plate has a cavity containing a heat exchange medium, the partition is fixedly arranged in the cavity to symmetrically divide the cavity, the upper part of the partition is spaced from the top of the cavity, the bottom of the partition is fixedly connected to the bottom of the cavity, and the bottom of the partition is provided with a plurality of square holes penetrating the partition.

[0010] As a further implementation, the top of the heat conducting plate fixedly connected to the inner wall of the top of the shielding building is provided with a plurality of notches penetrating the heat conducting plate, so that the notches and the inner wall of the top of the shielding building form gas passages allowing air flow.

[0011] As a further implementation, the heat conducting plates are arranged in blocks in width and height directions, and adjacent heat conducting plates are not connected to each other.

[0012] As a further implementation method, the air inlet is located in the circumferential direction of the upper part of the shielding plant cylinder, and the air inlet is arranged obliquely upward.

[0013] As a further implementation, a core is arranged in the pressure vessel, the pressure vessel is connected to a loop pressure boundary arranged in the containment vessel, and a loop steam release valve is arranged on the loop pressure boundary.

[0014] As a further implementation, the containment is provided with a gate for equipment and personnel to enter and exit, the lower end of the heat conducting plate extends to the lower part of the gate and a channel is opened on the heat conducting plate at a position corresponding to the gate.

[0015] As a further implementation, the shielding plant consists of a cylindrical body and a top of a double-layer structure fixedly arranged above the body, and the cooling water tank is arranged in the top of the double-layer structure.

[0016] The beneficial effects of the present invention are as follows:

[0017] (1) The present invention sets a heat conducting plate with heat exchange and heat insulation capabilities on the peripheral side of the containment, and allows part of the heat conducting plate to extend into the cooling water tank. The heat transferred by the heat conducting plate is used to heat the iced area, thereby avoiding the influence of ice on the operation of the cooling water tank and improving safety. At the same time, the heat conducting plate plays a role of heat insulation, preventing the air outside the heat conducting plate from being heated too quickly, and effectively ensuring the cooling effect of the air on the containment.

[0018] (2) The heat conducting plate of the present invention plays an auxiliary role in cooling down. While the air and the containment are exchanging heat, the heat of the containment can be conducted out through the heat conducting plate and exchanged with the air. On the basis of ensuring the heat conduction capacity, the heat exchange efficiency between the air and the containment is greatly improved.

[0019] (3) The top of the heat conducting plate of the present invention is provided with a notch to allow air to flow. The external air entering from the air inlet flows through the gas channel, which can cool the top of the heat conducting plate, thereby greatly improving the cooling efficiency of the heat exchange medium in the heat conducting plate.

[0020] (4) The heat conducting plate and the bottom of the shielding building of the present invention have a gas passage that allows air to pass through, which greatly improves the air cooling capacity of the passive containment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Figure 1 It is a schematic cross-sectional view of the overall structure of a passive cooling system for a core of a pressurized water reactor nuclear power plant after an accident according to one or more embodiments of the present invention;

[0023] Figure 2 is a schematic structural diagram of an extended arrangement of a heat conducting plate according to one or more embodiments of the present invention;

[0024] Figure 3 is a schematic cross-sectional structure diagram of a heat conducting plate according to one or more embodiments of the present invention;

[0025] Figure 4 is a perspective schematic diagram of a heat conducting plate according to one or more embodiments of the present invention;

[0026] In the figure: the distances or sizes between parts are exaggerated to show the positions of the parts, and the schematic diagram is for illustration only;

[0027] Among them, 1. Pressure vessel; 2. Loop pressure boundary; 3. Containment; 4. Shielding building; 5. Cooling water tank; 6. Cooling water pipe; 7. Chimney; 8. Cooling water distribution plate; 9. Heat transfer plate; 91. Partition; 10. Gate; 11. Loop steam release valve; 12. Core; 13. Air inlet; 14. Inner shell; 15. Outer shell; 16. Air flow channel. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0029] As introduced in the background technology, the existing passive cooling system is simply equipped with a heat transfer plate, which cannot achieve continuous cooling of the containment. External water replenishment 72 hours after the accident depends on external operation. In winter in cold areas, the water in the water tank on the top of the containment will freeze, resulting in the problem that the containment spray water pipe cannot operate normally. In order to solve the above technical problems, the present invention proposes a passive cooling system for the core after an accident of a pressurized water reactor nuclear power plant.

[0030] Example 1

[0031] In a typical embodiment of the present invention, Figure 1-Figure 4 As shown, a passive cooling system for the core after an accident of a pressurized water reactor nuclear power plant is proposed, comprising a shielding building 4, a containment shell 3 arranged in the shielding building 4, and a pressure vessel 1 arranged in the containment shell 3. The containment shell 3 is a steel structure, and a gate 10 for the entry and exit of equipment and personnel is provided on the containment shell 3. A core 12 is arranged in the pressure vessel 1, and the pressure vessel 1 is connected to a loop pressure boundary 2 arranged in the containment shell 3, and a loop steam release valve 11 is provided on the loop pressure boundary 2.

[0032] A cooling water distribution tray 8 is provided at the top of the containment vessel 3 and in the middle of the shielding building 4. The cooling water distribution tray 8 is suspended on the top inner wall of the shielding building 4. A cooling water tank 5 is provided on the top of the shielding building 4. The cooling water tank 5 is located above the cooling water distribution tray 8 and is connected to the cooling water distribution tray 8 through a cooling water pipe 6.

[0033] An air flow passage 16 penetrating the top of the shielding building 4 is provided. The air flow passage 16 is located above the cooling water distribution plate 8 . The cooling water tank 5 is located around the air flow passage 16 . A chimney 7 is fixedly provided in the air flow passage 16 .

[0034] A plurality of air exhaust inlets 13 are provided on the cylinder of the shielding building 4 near the top, and the axes of the air inlets 13 are inclined upward from the outside of the shielding building 4 .

[0035] A heat conducting plate 9 is arranged in the gap between the inner wall of the shielding building 4 and the containment shell 3, the lower end of the heat conducting plate 9 extends to the lower part of the gate 10, and a passage for allowing personnel and equipment to pass through is opened on the heat conducting plate 9 at a position corresponding to the gate 10.

[0036] Specific as Figure 1 As shown, the shielding building 4 is a steel-concrete composite structure, including a cylindrical body and a double-layer structure top. The double-layer structure top is formed at the upper end of the cylindrical body, and the double-layer structure top includes an inner shell 14, an outer shell 15 and an air flow channel 16.

[0037] The steel frame on the top of the shielding building 4, the inner shell 14 is a semi-ellipsoidal arch shell, and its semi-ellipsoidal arch shell is set on a tensile stress ring beam; the outer shell 15 is a hemispherical arch shell, and its hemispherical arch shell is set on another tensile stress ring beam.

[0038] Specifically, the tensile stress ring beam of the inner shell 14 is taken as the outer circle, the air flow channel 16 is taken as the inner circle, and the semi-elliptical arch beams are evenly arranged at equal angles around the center of the circle. The number of semi-elliptical arch beams of the inner shell 14 is 10 to 16, which may be 10, 12 or 16. The projection of the arch beam is the secant of the outer circle and the tangent of the inner circle, and the midpoint of the secant is on the circumference of the inner circle, thereby forming a semi-ellipsoidal arch shell with a mesh structure;

[0039] The tensile stress ring beam of the outer shell 15 is taken as the outer circle, the air flow channel 16 is taken as the inner circle, and semicircular arch beams are evenly arranged at equal angles around the center of the circle. The outer shell 15 has 10 to 16 semicircular arch beams, which can be 10, 12 or 16. The projection of the arch beam is the secant of the outer circle and the tangent of the inner circle. The midpoint of the secant is on the circumference of the inner circle, thereby forming a hemispherical arch shell with a mesh structure. Straight beams are arranged in the center of the semi-ellipsoidal arch shell of the inner shell 14 and the hemispherical arch shell of the outer shell 15 to form an opening as the air flow channel 16.

[0040] The cavity formed between the inner shell 14, the outer shell 15 and the air passage 16 is a water tank 5, that is, the top of the double-layer steel-concrete composite structure constitutes a cooling water tank 5. A cooling water distribution plate 8 is arranged on the top of the steel containment 3 and in the middle of the shielding plant 4, and the cooling water distribution plate 8 is suspended on the arch shell of the inner shell 14.

[0041] Two or three cooling water pipes 6 are arranged in the cooling water tank 5 , wherein the water inlet end of the cooling water pipe 6 is arranged in the cooling water tank 5 , and the water outlet end passes through the bottom of the cooling water tank 5 and extends to the upper part of the cooling water distribution plate 8 .

[0042] A chimney 7 is installed on the middle channel of the steel-concrete composite structure of the shielding building 4, which is 0m to 12m higher than the top of the shielding building 4, and can be 0, 1m, 5m or 12m. In the shielding building 4, a heat conducting plate 9 is fixedly arranged in the gap between the inner wall of the shielding building 4 and the containment shell 3 to enclose the containment shell 3. Specifically, the top of the heat conducting plate 9 is fixedly connected to the top of the shielding building 4, and the ratio of the inner side spacing of the heat conducting plate 9 to the containment shell 3 and the outer side spacing to the shielding building 4 is in the range of 0.15 to 1:1, and can be 0.15:1, 0.5:1 or 1:1.

[0043] The lower end of the heat conducting plate 9 extends to the lower part of the gate 10 and is not connected to the bottom of the shielding building 4 to form a space allowing air to pass through, and a passage allowing equipment and personnel to pass through is opened at a position corresponding to the gate 10 on the heat conducting plate 9. The lower end of the heat conducting plate 9 is 1m to 4m from the ground, which can be 1m, 2m or 4m.

[0044] Specific as Figure 3-Figure 4 As shown, the heat conducting plate 9 is arranged around the containment shell 3. The heat conducting plate 9 is a hollow structure. There is a cavity inside the heat conducting plate 9. A partition 91 is fixedly arranged in the cavity to symmetrically divide the cavity. The partition 91 is made of a heat insulating material. There is a gap between the upper part of the partition 91 and the top of the cavity. The bottom of the partition 91 is fixedly connected to the bottom of the cavity. At the same time, a plurality of square holes penetrating the partition 91 are opened on the bottom of the partition 91.

[0045] A heat transfer medium is injected into the cavity of the heat conducting plate 9, so that the heat conducting plate 9 becomes a heat plate capable of forming a natural circulation. When the liquid phase heat transfer medium at the bottom of the heat conducting plate 9 absorbs heat, it vaporizes into a gas phase, and the gas phase medium rises to the top of the cavity, exchanges heat with the outside through the heat conducting plate 9 to dissipate heat to the outside, condenses into a liquid phase, and then flows back to the bottom of the cavity.

[0046] Under accident conditions, the containment shell 3 heats up, and the side of the heat conduction plate 9 close to the containment shell 3 heats up quickly. When the working fluid vaporizes and enters the top space, due to the lower temperature on the outside, the gas phase working fluid condenses and flows back to the bottom along the outer wall, and then flows through the square holes at the bottom of the partition 91.

[0047] While dissipating heat, the heat conducting plate 9 also serves to guide the air. The external air entering from the air inlet 13 sinks, bypasses the bottom of the heat conducting plate 9 and enters between the heat conducting plate 9 and the containment shell 3, and takes away the heated moisture on the containment shell 3 during the rising process.

[0048] The top of a portion of the heat conducting plate 9 is fixedly connected to the top inner wall of the shielding building 4. The top of the portion of the heat conducting plate 9 is provided with a plurality of recesses penetrating the heat conducting plate 9 to form a gas passage allowing air flow between the inner shell 14. In this way, the external air entering from the air inlet 13 flows through the gas passage and can cool the top of the heat conducting plate 9.

[0049] After the heat transfer medium is injected into the heat conducting plate 9 for heat transfer, a heat insulating layer is formed on the heat conducting plate 9 as a whole, which can reduce the heating of the air outside the heat conducting plate 9 compared with a solid air guide plate.

[0050] Considering the processing width of the heat conducting plate 9, the heat conducting plate 9 can be divided into blocks in the width and height directions. The adjacent heat conducting plates 9 arranged in blocks are not connected to each other. When the heat transfer medium condenses, the heat conducting plate 9 on the lower layer can transfer heat to the heat conducting plate 9 on the upper layer.

[0051] like Figure 2 As shown, the top of part of the heat conducting plate 9 extends into the cooling water tank 5 and is located near the cooling water pipe 6. In this way, in cold areas, when ice forms in the cooling water tank 5, the heat transferred by the heat conducting plate 9 can be used to heat the frozen area to melt the ice and achieve the spraying of cooling water.

[0052] 2 to 5 rows of air inlets 13 are provided along the circumferential direction of the upper part of the cylinder of the shielding plant 4, which may be 2, 3 or 5 rows, and the axis of the air inlet 13 is inclined upward from the outside of the shielding plant 4 by 50° to 80°, which may be 50°, 65° or 80°. The diameter of the air inlet 13 is 7 cm to 20 cm, which may be 7 cm, 10 cm or 20 cm, and the center spacing is 12 cm to 24 cm, which may be 12 cm, 20 cm or 24 cm.

[0053] The specific working principle is:

[0054] When an accident occurs in the reactor, such as the rupture of the pressure vessel 1 or the rupture of the loop pressure boundary 2, the pressure water in the loop flashes into steam and is ejected into the containment 3; if there is no rupture in the system, the system automatically opens the loop steam release valve 11, and the system actively discharges the steam in the loop into the space of the containment 3. Due to the cooling outside the containment 3, the condensed water flows to the bottom of the containment 3, and is then heated and evaporated to form a natural cycle, which continuously evaporates and cools, and transfers the heat of the core 12 to the outside world;

[0055] When receiving the signal of high pressure in the containment 3, the cooling water pipe 6 starts to open automatically and injects water into the cooling water distribution plate 8. The cooling water distribution plate 8 evenly distributes the cooling water to flow on the containment 3. The cooling water evaporates on the containment 3 and takes away the heat. As time goes by, less and less cooling water flows on the containment 3, and the water film coverage on the containment 3 becomes smaller and smaller. At this time, the cooling effect of the air gradually becomes significant. The air enters the shielding building 4 through the air inlet 13, flows downward along the heat conduction plate 9, and after reaching the bottom, turns upward along the containment 3. In the air channel between the containment 3 and the heat conduction plate 9, it is heated by the surface of the containment 3, and the flow rate gradually increases. Finally, it is discharged through the chimney 7 to take away the heat in the containment 3, thereby achieving the purpose of cooling the core 12.

[0056] The heat conducting plate 9 plays a role of heat insulation, preventing the air outside the heat conducting plate 9 from being heated too quickly, effectively ensuring the cooling effect of the air on the containment shell 3. At the same time, the heat conducting plate 9 plays a role of auxiliary cooling, extracting the heat of the containment shell 3 and exchanging heat with the air, ensuring the heat conduction capacity while greatly improving the heat conduction efficiency (which can also be understood as the heat exchange efficiency between the air and the containment shell 3).

[0057] It is understandable that when ice forms in the cooling water tank 5 , the heat transferred by the heat conducting plate 9 can be used to heat the frozen area, so that the ice melts and the cooling water is sprayed.

[0058] The above description is only a preferred embodiment of the present invention and is 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 passive cooling system for the core of a pressurized water reactor nuclear power plant after an accident, comprising a shielding building, a containment shell arranged in the shielding building, and a pressure vessel arranged in the containment shell, a cooling water distribution plate is fixedly arranged at the middle position of the top of the containment shell, a cooling water tank connected to the cooling water distribution plate and an air flow channel penetrating the top of the shielding building are arranged on the top of the shielding building, and a plurality of air inlets are arranged on the cylinder of the shielding building, characterized in that: A heat conducting plate is provided around the containment shell, and the heat conducting plate contains a heat transfer medium and a baffle for heat insulation. There is a space between the lower end of the heat conducting plate and the bottom of the shielding building that allows air to pass through. The top of some heat conducting plates is fixedly connected to the top inner wall of the shielding building and is provided with a gas channel. The top of some heat conducting plates extends into the cooling water tank. The heat conducting plate has a cavity inside, and the cavity contains a heat exchange medium. The partition is fixedly arranged in the cavity to symmetrically divide the cavity. There is a gap between the upper part of the partition and the top of the cavity, and the bottom of the partition is fixedly connected to the bottom of the cavity. The bottom of the partition is provided with a plurality of square holes penetrating the partition.

2. The post-accident core passive cooling system of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: The cooling water tank is located above the cooling water distribution plate and is connected to the cooling water distribution plate through a cooling water pipe. The heat conduction plate in the cooling water tank is close to the cooling water pipe.

3. The post-accident core passive cooling system of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: The heat conducting plate is located between the inner wall of the shielding building and the containment vessel.

4. The post-accident core passive cooling system of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: The top of the heat conducting plate fixedly connected to the inner wall of the top of the shielding building is provided with a plurality of notches penetrating the heat conducting plate, and the notches form a gas passage allowing air flow between the notches and the inner wall of the top of the shielding building.

5. The post-accident core passive cooling system of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: The heat conducting plates are arranged in blocks in the width and height directions, and adjacent heat conducting plates are not connected to each other.

6. The post-accident core passive cooling system of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: The air inlet is located in the circumferential direction of the upper part of the shielding plant cylinder, and the air inlet is arranged obliquely upward.

7. The post-accident core passive cooling system of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: A core is arranged in the pressure vessel, and the pressure vessel is connected to a loop pressure boundary arranged in the containment vessel, and a loop steam release valve is arranged on the loop pressure boundary.

8. The post-accident core passive cooling system of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: The containment shell is provided with a gate for equipment and personnel to enter and exit, the lower end of the heat conducting plate extends to the lower part of the gate, and a passage is opened on the heat conducting plate at a position corresponding to the gate.

9. The post-accident core passive cooling system of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: The shielding plant consists of a cylindrical body and a top of a double-layer structure fixedly arranged above the body, and the cooling water tank is arranged in the top of the double-layer structure.

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