Passive residual heat removal system after primary side accident of nuclear power plant and control method

Abstract

The invention provides a nuclear power plant primary side post-accident passive residual heat removal system and a control method, the system comprises a reactor coolant system, a containment inner water tank, a collecting mechanism and a passive water replenishing tank, and the reactor coolant system comprises a hot section and a cold section; the containment inner water tank is installed on the inner wall of the steel containment, the heat exchanger is arranged in the containment inner water tank, the hot section is connected with an inlet pipeline of the heat exchanger, the cold section is connected with an outlet pipeline of the heat exchanger, and the collecting mechanism is arranged on the inner wall of the steel containment and communicated with the containment inner water tank through a connecting pipe. The collecting device is used for collecting condensate on the inner wall of the steel containment in a grading manner along the axial direction of the containment and enabling the condensate to flow to a water tank in the containment through a connecting pipe; one end of the passive water replenishing tank is connected with the water tank in the containment through a runner pipe, and the passive water replenishing tank replenishes water to the water tank in the containment when the liquid level of the water tank in the containment drops to a target value.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power maintenance, and in particular to a passive residual heat removal system and a control method after a primary side accident in a nuclear power plant. Background Art

[0002] At present, the primary side post-accident residual heat removal systems in the design of nuclear power plants are mainly divided into active and passive types.

[0003] Among them, when the passive primary side post-accident residual heat removal system is in operation, the natural circulation driving force formed by the height difference and temperature difference is used to flow the coolant from the reactor to the heat exchanger tube side and then return to the reactor cooling system. The heat exchanger is arranged in the water tank inside the containment which serves as a heat sink.

[0004] In passive power plants, the heat sink is the water tank inside the containment. During the heat exchanger heating process, the water in the water tank will boil and evaporate. In order to achieve long-term cooling, a large water tank needs to be installed inside the containment. For example, for a million-kilowatt nuclear power unit, the water tank volume can reach 2000m 3 , and it is earthquake-resistant equipment, so the structural construction is difficult and costly.

[0005] Based on this, the inventors of the present application propose a passive residual heat removal system and control method after a primary side accident in a nuclear power plant, in order to solve one or more of the above technical problems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects in the prior art of the passive power station water tank being too large, resulting in difficulty in structural construction and high cost, and to provide a passive residual heat removal system and control method after a primary side accident in a nuclear power plant.

[0007] The present invention solves the above technical problems through the following technical solutions:

[0008] The present invention provides a passive residual heat removal system after a primary side accident in a nuclear power plant, comprising:

[0009] Reactor coolant system, including hot and cold sections;

[0010] The containment water tank is installed on the inner wall of the steel containment, and a heat exchanger is arranged in the containment water tank. The hot section is connected to the inlet pipeline of the heat exchanger, and the cold section is connected to the outlet pipeline of the heat exchanger;

[0011] A collecting mechanism is provided on the inner wall of the steel containment shell and is connected to the water tank in the containment shell through a connecting pipe, wherein the collecting mechanism is used to collect condensate on the inner wall of the steel containment shell in stages along the axial direction of the containment shell and flow the condensate to the water tank in the containment shell through the connecting pipe;

[0012] A passive water replenishment tank has one end connected to the water tank in the containment shell through a flow pipe. The passive water replenishment tank replenishes water to the water tank in the containment shell when the liquid level in the water tank in the containment shell drops to a target value.

[0013] According to one embodiment of the present invention, the collection mechanism includes at least two collection boxes, and the at least two collection boxes are arranged at intervals along the axial direction of the steel containment shell.

[0014] According to one embodiment of the present invention, the collection box includes a box body and a guide plate, one end of the box body is connected to the inner wall of the steel containment shell, the guide plate is located above the box body and one end is connected to the inner wall of the steel containment shell, and the other end extends toward the inner cavity of the box body.

[0015] According to one embodiment of the present invention, a first water baffle is provided on one side of the box body close to the guide plate, one end of the first water baffle is connected to the box body, and the other end extends toward the guide plate.

[0016] According to one embodiment of the present invention, a second water baffle is further provided on the top of the box body, and the second water baffle is arranged around the circumference of the top of the box body;

[0017] One end of the second water baffle is connected to the box body, and the other end extends toward a side away from the box body.

[0018] According to one embodiment of the present invention, the height of the second water baffle is greater than the height of the first water baffle.

[0019] According to one embodiment of the present invention, adjacent boxes are connected in sequence via the connecting pipes.

[0020] According to one embodiment of the present invention, one end of the flow pipe is connected to the bottom of the water tank in the containment vessel;

[0021] The passive water replenishment tank is pressurized by high-pressure gas. When the liquid level of the water tank in the containment vessel is lower than the target value, the water in the passive water replenishment tank is automatically replenished into the water tank in the containment vessel under the pressure of the high-pressure gas.

[0022] According to one embodiment of the present invention, a one-way valve is provided on the flow pipe, and the one-way valve is used to control the one-way replenishment of water in the passive water replenishment tank to the water tank in the containment.

[0023] The present invention also provides a method for controlling the removal of passive residual heat after a primary-side accident in a nuclear power plant, using the above-described passive residual heat removal system after a primary-side accident in a nuclear power plant. The control method includes:

[0024] By arranging a passive water replenishment tank outside the steel containment, when the liquid level of the water tank inside the containment is lower than the target value, the passive water replenishment tank automatically replenishes water into the water tank inside the containment.

[0025] The positive progress effect of the present invention is:

[0026] The passive residual heat removal system after a primary side accident in a nuclear power plant of the present invention is provided with a collection mechanism on the inner wall of the steel containment shell, which is used to collect condensate formed by condensation of water vapor emitted by boiling in the water tank in the containment shell on the inner wall surface of the steel containment shell in a graded manner along the axial direction of the containment shell, thereby improving the utilization rate of the water tank in the containment shell as a heat sink. At the same time, a passive water supply tank is provided on the outer side of the steel containment shell to reduce the volume of the water tank in the containment shell, effectively improving the economy, reliability and operation and maintenance convenience of the nuclear power plant, and at the same time, realizing long-term cooling of the nuclear power plant without human intervention, thereby effectively improving the safety of the nuclear power plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which:

[0028] Figure 1 This is a schematic structural diagram of a passive residual heat removal system after a primary side accident in a nuclear power plant according to the present invention;

[0029] Figure 2 for Figure 1 Schematic diagram of the structure of the collection box.

[0030] 1. Reactor coolant system; 11. Hot section; 12. Cold section;

[0031] 2. Water tank inside containment;

[0032] 3. Steel containment;

[0033] 4. Heat exchanger; 41. Inlet pipeline; 42. Outlet pipeline;

[0034] 5. Collection mechanism; 51. Connecting pipe; 53. Collection box; 531. Box body; 532. Drain plate; 533. First water baffle; 534. Second water baffle;

[0035] 6. Passive water supply tank; 61. Flow pipe; 62. One-way valve. DETAILED DESCRIPTION

[0036] The present invention is further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description herein. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0038] Please refer to Figure 1 and Figure 2 The present invention proposes a passive residual heat removal system after a primary side accident in a nuclear power plant. The residual heat removal system includes a reactor coolant system 1, a water tank 2 in the containment, a collection mechanism 5, and a passive water supply tank 6. The reactor coolant system 1 includes a hot section 11 and a cold section 12; the water tank 2 in the containment is installed on the inner wall of the steel containment 3, and a heat exchanger 4 is arranged in the water tank 2 in the containment. The hot section 11 is connected to the inlet pipeline 41 of the heat exchanger 4, and the cold section 12 is connected to the outlet pipeline 42 of the heat exchanger 4.

[0039] It can be seen that in the passive primary side post-accident residual heat removal system, the natural circulation driving force formed by the height difference and temperature difference is used to flow the coolant from the reactor to the tube side of the heat exchanger 4 and then return to the reactor coolant system 1.

[0040] Because during heat exchange, the water temperature in the water tank 2 inside the containment increases until it boils and evaporates, and the generated water vapor is discharged into the space of the steel containment 3. When the water vapor contacts the inner wall of the steel containment 3, it will cool down and exchange heat to form condensate. Traditional condensate flows directly into the pit and is not used as circulating cooling water.

[0041] In order to support long-term cooling, the present invention sets a collection mechanism 5 on the inner wall of the steel containment shell 3. The collection mechanism 5 is connected to the water tank 2 in the containment shell through a connecting pipe 51. The collection mechanism 5 is used to collect the condensate on the inner wall of the steel containment shell 3 in stages along the axial direction of the containment shell and flow it to the water tank 2 in the containment shell through the connecting pipe 51.

[0042] That is, conventional condensate is collected in a sump at the bottom of the steel containment vessel 3. The water in the sump is either safely treated or recycled. However, recycling requires further decontamination and filtration of the water, which is a very cumbersome process. Therefore, the water is generally not recycled back to the containment vessel water tank 2 for use. However, the present invention provides a collection mechanism 5 on the inner wall of the steel containment vessel 3 to directly collect the condensate generated on the inner wall of the steel containment vessel 3. The collected condensate is then directly replenished to the containment vessel water tank 2, effectively improving the utilization rate of the containment vessel water tank 2 as a heat sink.

[0043] Furthermore, one end of the passive water replenishment tank 6 is connected to the water tank 2 in the containment shell through a flow pipe 61 , and the passive water replenishment tank 6 replenishes water to the water tank 2 in the containment shell when the liquid level in the water tank 2 in the containment shell drops to a target value.

[0044] In order to be used for long-term cooling, the traditional water tank 2 in the containment is set to be very large. On the one hand, it takes up space and is difficult to install. On the other hand, the overly large water tank 2 in the containment makes the overall size of the containment too large, which is not conducive to the miniaturization design of the containment.

[0045] The present invention provides a collecting mechanism 5 to collect most of the cooling liquid obtained by evaporation and cooling, thereby replenishing a certain amount of water to the water tank 2 in the containment, thereby reducing the installation volume of the water tank 2 in the containment.

[0046] Because some of the condensed water on the top of the containment will directly drip into the pit, this collection method will still have certain losses. Based on this, the present invention further arranges a passive water replenishment tank 6 on the outside of the steel containment 3. When the liquid level of the water tank 2 in the containment drops to the target value, the water tank 2 in the containment is automatically replenished with water. Thus, the water tank 2 in the containment is replenished with water through the passive water replenishment tank 6 and the collection mechanism 5, which meets the miniaturized design of the water tank 2 in the containment.

[0047] Therefore, the volume of the water tank 2 inside the containment vessel of the present invention can be set relatively small, thereby reducing the construction difficulty and cost of the water tank 2 inside the containment vessel, improving the convenience of operation and maintenance, realizing long-term cooling of the nuclear power plant without human intervention, and effectively improving the safety of the nuclear power plant.

[0048] In one embodiment, the collection mechanism 5 includes at least two collection boxes 53 , and the at least two collection boxes 53 are arranged at intervals along the axial direction of the steel containment shell 3 .

[0049] It can be seen that the water tank 2 inside the containment vessel in the present invention is arc-shaped and is arranged around the inner wall of the steel containment vessel 3 .

[0050] Reference Figure 1The collecting box 53 is annular, and each collecting box 53 is arranged circumferentially around the inner wall of the steel containment shell 3 , so that the collecting box 53 can collect the condensate formed on the inner wall of the steel containment shell 3 and transport it to the water tank 2 inside the containment shell.

[0051] The purpose of arranging multiple collection boxes 53 along the axial direction of the steel containment shell 3 is to reduce the flow rate of the condensate reaching the water tank 2 inside the containment shell, avoid the final flow rate of the condensate reaching the water tank 2 inside the containment shell being too high and causing splashing, thereby helping to improve the collection rate of the condensate.

[0052] Specifically, as to the number of water tanks 2 provided in the containment vessel, three are taken as an example for explanation, but the specific number is not limited.

[0053] Please refer to Figure 2 The collection box 53 includes a box body 531 and a guide plate 532. One end of the box body 531 is connected to the inner wall of the steel containment shell 3. The guide plate 532 is located above the box body 531 and one end is connected to the inner wall of the steel containment shell 3, and the other end extends toward the inner cavity of the box body 531.

[0054] To facilitate the installation and maintenance of the box body 531, in the present invention, one end of the box body 531 is detachably connected to the steel containment shell 3 via a threaded connector, thereby providing a small gap between the box body 531 and the inner wall of the steel containment shell 3. By providing a guide plate 532, the condensate can be introduced into the box body 531, thereby avoiding the loss of condensate caused by the condensate flowing directly into the gap between the box body 531 and the steel containment shell 3.

[0055] It can be seen that the guide plate 532 is annular as a whole and is arranged circumferentially around the inner wall of the steel containment shell 3.

[0056] Furthermore, the included angle between the guide plate 532 and the inner wall of the steel containment shell 3 is set so that the condensate can be guided into the box body 531, thereby preventing the condensate from impacting the top surface of the box body 531 and splashing, which is beneficial to improving the collection rate of the condensate.

[0057] Furthermore, a first water baffle 533 is provided on one side of the box body 531 close to the guide plate 532 . One end of the first water baffle 533 is connected to the box body 531 , and the other end extends toward the guide plate 532 .

[0058] After the condensate reaches the box body 531, it will splash between the box body 531. In order to prevent the splashed condensate from flowing out through the gap between the box body 531 and the inner wall of the steel containment shell 3, a first water baffle 533 is set on the side of the box body 531 close to the guide plate 532. The top of the first water baffle 533 is matched with the gap between the guide plate 532. In this way, the amount of splashed condensate flowing out from the gap between the box body 531 and the inner wall of the steel containment shell 3 can be greatly reduced, thereby improving the collection rate of the condensate.

[0059] Optionally, a second water baffle 534 is further provided on the top of the box body 531 , and the second water baffle 534 is arranged circumferentially around the top of the box body 531 ; one end of the second water baffle 534 is connected to the box body 531 , and the other end extends toward a side away from the box body 531 .

[0060] That is, when the condensate flows into the box body 531 along the guide plate 532, the direction of the splashing condensate is irregular, so a second water baffle 534 is circumferentially arranged around the top of the box body 531. The second water baffle 534 can greatly reduce the condensate from the box body 531.

[0061] It should be noted that, because the condensate mainly splashes in the circumferential direction away from the second water baffle 534 toward the box body 531 when reaching the box body 531, the height of the second water baffle 534 is greater than the height of the first water baffle 533 in the present invention. As a result, the condensate introduced through the drainage plate 532 is isolated by the first water baffle 533 and the second water baffle 534 and is all retained in the box body 531, thereby greatly reducing the loss of condensate collection.

[0062] It can be seen that the first water baffle 533 and the second water baffle 534 are connected to the box body 531 by welding. Alternatively, the first water baffle 533 and the second water baffle 534 and the box body 531 can also be integrally formed, and the connection relationship between the first water baffle 533 and the second water baffle 534 and the box body 531 is not limited here.

[0063] Please continue to refer to Figure 1 Adjacent boxes 531 are connected in sequence through connecting pipes 51.

[0064] The connecting pipe 51 is used to connect the adjacent box 531 , so that the condensate collected in the box 531 can be gradually introduced into the box 531 through the connecting pipe 51 .

[0065] The number of connecting pipes 51 can be one, two or more, which is not limited here and can be adjusted according to actual needs.

[0066] Please continue to refer to Figure 1 One end of the flow pipe 61 is connected to the bottom of the water tank 2 in the containment shell; the passive water supply tank 6 is pressurized by high-pressure gas. When the liquid level of the water tank 2 in the containment shell is lower than the target value, the water in the passive water supply tank 6 is automatically replenished into the water tank 2 in the containment shell under the pressure of the high-pressure gas.

[0067] As can be seen, the high-pressure data filled in the passive makeup water tank 6 corresponds to the hydraulic data generated by the liquid level in the containment tank 2. Therefore, when the liquid level in the containment tank 2 has not dropped to the target value, the high-pressure gas cannot replenish the water in the passive makeup water tank 6 into the containment tank 2. However, when the liquid level in the containment tank 2 falls below the target value, the high-pressure gas automatically replenishes the water in the passive makeup water tank 6 into the containment tank 2, maintaining the liquid level in the containment tank 2 at a certain value. This passive cooling method achieves long-term core cooling throughout the entire accident cycle.

[0068] Furthermore, a one-way valve 62 is provided on the flow pipe 61 , and the one-way valve 62 is used to control the one-way replenishment of water in the passive water supply tank 6 to the water tank 2 in the containment.

[0069] In order to prevent the water in the water tank 2 in the containment vessel from flowing into the passive water supply tank 6 , a one-way flow mode is adopted between the passive water supply tank 6 and the water tank 2 in the containment vessel.

[0070] It is known that other control components such as a flow rate regulating valve may be provided on the flow pipe 61, which is not limited here. Also, the one-way valve 62 may be replaced by other types of control valves, which is not limited here.

[0071] In summary, the present invention provides a collection mechanism 5 on the inner wall of the steel containment shell 3 to collect the condensate generated on the inner wall of the steel containment shell 3 , thereby facilitating the improvement of the utilization rate of the water tank 2 in the containment shell as a heat sink.

[0072] Moreover, a passive water supply tank 6 is provided outside the steel containment vessel 3, which is conducive to reducing the volume of the water tank 2 inside the containment vessel, effectively improving the economy, reliability and operation and maintenance convenience of the nuclear power plant, and at the same time realizing long-term cooling of the nuclear power plant without human intervention, effectively improving the safety of the nuclear power plant.

[0073] The present invention also provides a method for controlling the removal of passive residual heat after a primary-side accident in a nuclear power plant. The method adopts the above-mentioned passive residual heat removal system after a primary-side accident in a nuclear power plant. The control method includes:

[0074] By setting a passive water replenishment tank outside the steel containment, when the liquid level in the water tank inside the containment is lower than the target value, the passive water replenishment tank automatically replenishes water into the water tank inside the containment.

[0075] A passive water replenishment tank is set outside the steel containment, which reduces the water demand of the water tank inside the containment and realizes automatic water replenishment of the water tank inside the containment without human intervention.

[0076] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "install", "connect", "connect", "fix" and so on should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can also be a mechanical connection. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0077] This application uses specific terms to describe the embodiments of this application. For example, "one embodiment," "an embodiment," and / or "some embodiments" refer to a certain feature, structure, or characteristic associated with at least one embodiment of this application. Therefore, it should be emphasized and noted that "one embodiment," "an embodiment," or "an alternative embodiment" mentioned twice or multiple times in different locations in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application may be appropriately combined.

[0078] Although the present invention is disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modifications, equivalent variations, and modifications made to the above embodiments in accordance with the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A passive residual heat removal system after a primary side accident in a nuclear power plant, characterized in that: include: Reactor coolant system, including hot and cold sections; The containment water tank is installed on the inner wall of the steel containment, and a heat exchanger is arranged in the containment water tank. The hot section is connected to the inlet pipeline of the heat exchanger, and the cold section is connected to the outlet pipeline of the heat exchanger; A collecting mechanism is provided on the inner wall of the steel containment shell and is connected to the water tank in the containment shell through a connecting pipe, wherein the collecting mechanism is used to collect condensate on the inner wall of the steel containment shell in stages along the axial direction of the containment shell and flow the condensate to the water tank in the containment shell through the connecting pipe; A passive water replenishment tank has one end connected to the water tank in the containment shell through a flow pipe. The passive water replenishment tank replenishes water to the water tank in the containment shell when the liquid level in the water tank in the containment shell drops to a target value.

2. The passive residual heat removal system after a primary side accident in a nuclear power plant according to claim 1, characterized in that: The collection mechanism includes at least two collection boxes, and the at least two collection boxes are arranged at intervals along the axial direction of the steel containment shell.

3. The passive residual heat removal system after a primary side accident in a nuclear power plant according to claim 2, characterized in that: The collection box includes a box body and a guide plate. One end of the box body is connected to the inner wall of the steel containment shell. The guide plate is located above the box body and one end is connected to the inner wall of the steel containment shell, and the other end extends toward the inner cavity of the box.

4. The passive residual heat removal system after a primary side accident in a nuclear power plant according to claim 3, characterized in that: A first water baffle is provided on one side of the box body close to the guide plate. One end of the first water baffle is connected to the box body, and the other end extends toward the guide plate.

5. The passive residual heat removal system after a primary side accident in a nuclear power plant according to claim 4, characterized in that: The top of the box body is further provided with a second water baffle, which is arranged around the circumference of the top of the box body; One end of the second water baffle is connected to the box body, and the other end extends toward a side away from the box body.

6. The passive residual heat removal system after a primary side accident in a nuclear power plant according to claim 5, characterized in that: The height of the second water baffle is greater than that of the first water baffle.

7. The passive residual heat removal system after a primary side accident in a nuclear power plant according to claim 3, characterized in that: The adjacent boxes are connected in sequence through the connecting pipes.

8. The passive residual heat removal system after a primary side accident in a nuclear power plant according to claim 1, characterized in that: One end of the flow pipe is connected to the bottom of the water tank in the containment vessel; The passive water replenishment tank is pressurized by high-pressure gas. When the liquid level of the water tank in the containment vessel is lower than the target value, the water in the passive water replenishment tank is automatically replenished into the water tank in the containment vessel under the pressure of the high-pressure gas.

9. The passive residual heat removal system after a primary side accident in a nuclear power plant according to claim 8, characterized in that: A one-way valve is provided on the flow pipe, and the one-way valve is used to control the one-way replenishment of water in the passive water replenishment tank to the water tank in the containment shell.

10. A method for controlling the removal of passive residual heat after a primary side accident in a nuclear power plant, characterized in that: The passive residual heat removal system after a primary-side accident in a nuclear power plant according to any one of claims 1 to 9 is used, wherein the control method comprises: By arranging a passive water replenishment tank outside the steel containment, when the liquid level of the water tank inside the containment is lower than the target value, the passive water replenishment tank automatically replenishes water into the water tank inside the containment.

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