Containment heat removal system

Abstract

This invention discloses a containment heat removal system, including a heat exchanger, a coolant tank, and a steam collection device disposed within the coolant tank, all located inside the containment. The heat exchanger is connected to the medium in the coolant tank. The medium in the heat exchanger absorbs heat from the containment and is discharged into the coolant tank through the steam collection device. The medium in the coolant tank returns to the heat exchanger. The steam collection device includes a vent valve assembly corresponding to different coolant tank levels. The vent valve assembly is configured to automatically open under its own force when the coolant level decreases, allowing at least a portion of the medium entering the steam collection device to enter the coolant tank through the vent valve assembly. The containment heat removal system proposed in this application avoids the problem of decreased heat removal capacity due to reduced coolant level, improves system driving force and heat exchange capacity, and eliminates risks such as steam hammer vibration, two-phase flow excitation, and flow stagnation.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactor safety, and more specifically, to a containment heat removal system. Background Technology

[0002] The containment vessel is the last physical safety barrier in a pressurized water reactor nuclear power plant. Maintaining its integrity to prevent the release of large amounts of radioactive material in the event of an accident is crucial to ensuring the safety of the nuclear power plant. When a major accident occurs, such as a large breach in the primary coolant circuit or a rupture in the secondary coolant main steam pipe, a large amount of high-temperature, high-pressure steam is released into the containment vessel. This causes a rapid rise in temperature and pressure within the containment vessel, exposing it to the risk of overpressure failure and a large-scale, uncontrolled release of radioactive material, thus posing a serious threat to the surrounding environment and personnel safety.

[0003] To ensure the integrity of the containment structure, many countries have conducted research on passive containment heat removal technologies, attempting to remove the massive decay heat within the containment under accident conditions solely through natural forces such as gravity and fluid density differences. For concrete containment structures, the main research schemes are divided into closed systems and open systems. Closed systems generally consist of an internal heat exchanger, an external heat exchanger, a cooling water tank, and connecting pipes and valves, forming a closed natural circulation loop. This type of scheme has not been widely applied in engineering due to its numerous heat transfer links, complex structure, and low heat removal capacity. Open systems generally consist of an internal heat exchanger, a cooling water tank, and connecting pipes and valves, forming an open natural circulation loop. This type of scheme has fewer heat transfer links, a simpler structure, and relatively higher heat removal capacity. However, these open system schemes pose risks such as steam hammer vibration, two-phase flow excitation, and flow stagnation, posing significant challenges to engineering applications.

[0004] Patent 201410126253.3 describes a system riser pipe with several outlets equipped with valves located in the water tank. The opening and closing of these valves are controlled by a measurement and control system, aiming to eliminate the adverse effects of the water level in the tank. However, this solution lacks feasibility in engineering wet environments with drastic water level fluctuations, especially in the event of a plant-wide power outage. In such an event, the measurement and control system would fail, and the valves would be unable to open and close properly. Addressing such accident scenarios is the fundamental starting point for configuring passive containment heat removal systems in next-generation nuclear power systems.

[0005] The designs of patents 202110361911.7 and 201580075448.2 overcome the shortcomings of designs such as steam hammer vibration, but there are still shortcomings such as the water tank level and static pressure significantly reducing the system's natural circulation capacity, and the concentration and accumulation of non-condensable gases outside the heat transfer tubes of the internal heat exchanger significantly increasing the heat transfer resistance. These shortcomings limit the system's heat dissipation capacity and can only meet the needs of coping with reactor over-baseline accidents. The patents also do not disclose the detailed structure of important equipment in the system.

[0006] In view of the above technical problems, this invention is hereby introduced. Summary of the Invention

[0007] The main objective of this invention is to provide a containment heat removal system to eliminate risks such as steam hammer vibration, two-phase flow excitation and flow stagnation, as well as to eliminate the adverse effects of coolant tank level, effectively reduce the accumulation of non-condensable gases outside the heat exchanger tubes, significantly increase the working fluid flow rate between heat exchanger tubes, and thus greatly improve the system's heat removal capacity, enabling it to cope with reactor baseline accidents.

[0008] To achieve the above objectives, the present invention provides a containment heat removal system, comprising a heat exchanger disposed inside the containment, a coolant tank, and a steam collection device disposed within the coolant tank. The heat exchanger is in communication with a medium in the coolant tank. The medium in the heat exchanger absorbs heat from the containment and is discharged into the coolant tank through the steam collection device. The medium in the coolant tank returns to the heat exchanger.

[0009] The steam collection device includes a steam exhaust valve assembly corresponding to different liquid levels in the coolant tank. The steam exhaust valve assembly is configured to automatically open under its own force when the liquid level decreases, allowing at least part of the medium entering the steam collection device to enter the coolant tank through the steam exhaust valve assembly, thereby balancing the static pressure difference between the inside and outside of the steam collection device and increasing the system circulation driving force at low liquid levels.

[0010] Furthermore, the steam collecting device includes a steam collecting pipe and a multi-stage sleeve fitted onto the steam collecting pipe. The multi-stage sleeves are distributed along the liquid level height direction, with the first-stage sleeve located at the bottom and the number of stages increasing sequentially upwards along the liquid level height. Each sleeve in the multi-stage sleeve can move axially along the steam collecting pipe as the liquid level height changes, and is configured to move downwards sequentially from the higher to the lower stage when the liquid level height decreases.

[0011] Furthermore, the steam collecting pipe is provided with multi-stage exhaust ports in the height direction. The multi-stage exhaust ports are correspondingly set with multi-stage sleeves. The exhaust ports and sleeves are combined to form an exhaust valve assembly. The multi-stage sleeves move downwards in sequence from high to low, so that the multi-stage exhaust ports open sequentially from high to low.

[0012] Furthermore, multiple limiters are fitted on the outer wall of the steam collecting pipe. The limiters are distributed along the axial direction of the steam collecting pipe, dividing the steam collecting pipe into multiple independent areas. Multi-stage sleeves are respectively set in each independent area.

[0013] Furthermore, each sleeve in the multi-stage sleeve is independent of the others and corresponds to a different liquid level.

[0014] Furthermore, each sleeve in the multi-stage sleeve is arranged to form a hollow cavity, and the buoyancy of the hollow cavity in the coolant tank is greater than the weight of the sleeve.

[0015] Furthermore, in a multi-stage sleeve, the inner diameter of the upper-stage sleeve is larger than the outer diameter of the lower-stage sleeve, adjacent sleeves are nested together, and the upper-stage sleeve can move along the outer wall of the lower-stage sleeve.

[0016] Furthermore, it includes a first positioning part, which is sleeved on the outside of the steam collecting pipe. The first positioning part limits the highest position of the multi-stage sleeve to prevent the multi-stage sleeve from detaching from the upper part of the steam collecting pipe.

[0017] Furthermore, an exhaust area is defined above the first positioning part along the axial direction of the steam collecting pipe, and a reinforcing ring is provided on the outer wall of the steam collecting pipe corresponding to the exhaust area to enhance the stability of the steam collecting pipe.

[0018] Furthermore, the maximum axial length of the multi-stage sleeve along the steam collecting pipe is not less than the axial length of the exhaust area along the steam collecting pipe, so that the multi-stage sleeve can completely cover each exhaust port within the length range of the steam collecting pipe.

[0019] Furthermore, it also includes a fourth positioning part, which is sleeved on the outside of the steam collecting pipe. The fourth positioning part limits the lowest position of the multi-stage sleeve to prevent the multi-stage sleeve from detaching from the bottom of the steam collecting pipe.

[0020] Furthermore, each level of sleeve is provided with a second positioning part at the top, and the second positioning parts of adjacent sleeves are in contact with each other to prevent the upper level sleeve from detaching from the bottom of the lower level sleeve.

[0021] Furthermore, each level of sleeve is provided with a third positioning part at the bottom. The third positioning part of the upper level sleeve contacts the second positioning part of the lower level sleeve to prevent the upper level sleeve from disengaging from the lower level sleeve when it moves upward.

[0022] Furthermore, the inner diameter of the second positioning part is equal to the outer diameter of the steam collecting pipe, and the outer diameter of the second positioning part is equal to the inner diameter of the upper-level sleeve.

[0023] Furthermore, the inner diameter of the third positioning part is equal to the outer diameter of the next-level sleeve.

[0024] Furthermore, the outer diameter of the first positioning part is equal to the inner diameter of the first-stage sleeve.

[0025] Furthermore, it also includes a flow deflector, which is fitted over the multi-stage sleeve.

[0026] Furthermore, a drain port is provided at the bottom of the flow guide, through which the cooling medium in the flow guide is discharged, reducing disturbance to the liquid level.

[0027] Furthermore, a steam-water separation hood is installed at the top of the steam collecting pipe to separate the steam-water mixture flowing out of the steam collecting pipe outlet.

[0028] Furthermore, it also includes support columns, which support the steam-water separator to maintain a predetermined distance between the steam-water separator and the guide shield.

[0029] Furthermore, the heat exchanger includes a first heat transfer tube bundle and a second heat transfer tube bundle, which are distributed in a mirror-symmetric manner.

[0030] Furthermore, the heat exchanger also includes a distribution manifold and a manifold. The first heat transfer tube bundle is connected to the distribution manifold and the manifold, and the second heat transfer tube bundle is connected to the distribution manifold and the manifold. The medium enters the first heat transfer tube bundle and / or the second heat transfer tube bundle through the distribution manifold and flows out of the heat exchanger through the manifold.

[0031] Furthermore, the second heat transfer tube bundle is symmetrically arranged on both sides of the distribution manifold and / or the manifold, and the second heat transfer tube bundle, the first heat transfer tube bundle, the distribution manifold and the manifold enclose a hollow region, in which the medium is accelerated.

[0032] Furthermore, the distribution manifold and the junction manifold are horizontally positioned, and their openings are located on the same side.

[0033] Furthermore, the first heat transfer tube bundle and / or the second heat transfer tube bundle include multiple heat transfer tube rows arranged in parallel, with a pressure difference formed between the heat transfer tube rows near the hollow region and the heat transfer tube rows far from the hollow region, accelerating the flow of the medium.

[0034] Furthermore, the heat transfer tube bank includes multiple heat transfer tubes arranged axially along the distribution manifold and / or the manifold.

[0035] Furthermore, the heat transfer pipe includes a first pipe section, a second pipe section, and an intermediate pipe section connecting the first pipe section and the second pipe section. The first pipe section is connected to the manifold, and the second pipe section is connected to the distribution manifold.

[0036] Furthermore, the length of the first pipe segment is less than the length of the second pipe segment.

[0037] Furthermore, the angle between the second pipe section and the intermediate pipe section is 60-80°.

[0038] Furthermore, the spacing between adjacent heat transfer tubes is 2 to 3 times the diameter of the heat transfer tubes.

[0039] Furthermore, the heat exchanger includes a support partition, which is disposed between the heat transfer tubes and perpendicular to the middle section of the heat transfer tubes.

[0040] Furthermore, it also includes an ascending pipe section and a descending pipe section. The ascending pipe section connects to the manifold and the coolant tank, and the descending pipe section connects to the coolant tank and the distribution manifold.

[0041] The containment heat removal system proposed in this invention achieves the following technical effects:

[0042] 1. The steam collection device used in the containment heat removal system of the present invention can not only completely eliminate the risks of steam hammer vibration, two-phase flow excitation and flow stagnation during the steam-liquid two-phase flow stage, but also automatically balance the static pressure difference between the inner and outer sides of the steam collection pipe in a passive manner, thereby eliminating the adverse effects of the coolant tank level on the natural circulation flow of the passive containment heat removal system.

[0043] 2. The heat exchanger used in the containment heat removal system of the present invention not only significantly reduces flow resistance without increasing the manufacturing difficulty of the heat exchanger, but also has a compact structure and significantly enhances heat transfer inside and outside the heat transfer tube, making it a high-efficiency heat exchanger with low flow resistance and strong heat exchange capacity.

[0044] 3. By optimizing the configuration of the containment heat removal system, this invention significantly enhances the system's flow stability and natural circulation capability, and substantially improves the heat removal power level of the passive containment heat removal system, enabling it to cope with reactor baseline accidents.

[0045] 4. The containment heat removal system of the present invention has a simple composition, the steam collection device is easy to disassemble and assemble, and the system has strong stability. Attached Figure Description

[0046] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0047] Figure 1 This diagram shows the structure of the containment heat removal system of the present invention.

[0048] Figure 2 A schematic diagram of the steam collection device structure of Embodiment 1 of the present invention is shown;

[0049] Figure 3 A front view of the overall structure of the heat exchanger according to an embodiment of the present invention is shown;

[0050] Figure 4 A side view of a heat exchanger according to an embodiment of the present invention is shown;

[0051] Figure 5 A schematic diagram of the heat exchange tube arrangement structure according to an embodiment of the present invention is shown;

[0052] Figure 6 A schematic diagram of a single heat exchange tube structure according to an embodiment of the present invention is shown;

[0053] Figure 7The variation trend of heat exchanger exhaust power with containment pressure in an embodiment of the present invention is shown.

[0054] Figure 8 The diagram shows the pressure trend within the containment vessel over time under a hypothetical reactor accident according to an embodiment of the present invention.

[0055] Figure 9 A schematic diagram of the steam collection device according to Embodiment 2 of the present invention is shown;

[0056] Figure 10 A schematic diagram of the multi-stage sleeve structure in the steam collection device of Embodiment 2 of the present invention is shown;

[0057] Figure 11 A top view of the steam collection device according to Embodiment 2 of the present invention is shown;

[0058] Figure 12 A schematic diagram of the positioning structure in the steam collection device of Embodiment 2 of the present invention is shown;

[0059] Figure 13 A schematic diagram of the positioning structure located at the upper and lower parts of the sleeve in the steam collection device of Embodiment 2 of the present invention is shown.

[0060] The above figures include the following reference numerals:

[0061] 20. Heat exchanger; 30. Coolant tank; 40. Steam collection device; 480. Exhaust valve assembly; 410. Steam collection pipe; 415. Limiter; 420. Sleeve; 460. Exhaust port; 416. First positioning part; 411. Reinforcing ring; 418. Fourth positioning part; 422. Second positioning part; 424. Third positioning part; 430. Flow guide; 431. Drain port; 440. Steam-water separator; 450. Support column; 230. First heat transfer tube bundle; 240. Second heat transfer tube bundle; 210. Distribution manifold; 220. Manifold; 234. Heat transfer tube bank; 2342. Heat transfer tube; 2344. First tube section; 2346. Second tube section; 2348. Intermediate tube section; 260. Support partition; 50. Rising tube section; 60. Falling tube section. Detailed Implementation

[0062] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0063] The present invention will be further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed by the present invention. The term "comprising" indicates the presence of a feature, but does not exclude the presence or addition of one or more other features. The terms "lateral," "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the purpose of description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0064] In this description, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more. Example 1

[0065] This application proposes a containment heat removal system, such as Figure 1 As shown, the containment heat removal system includes a heat exchanger 20, a coolant tank 30, and a steam collection device 40 disposed inside the coolant tank 30. The heat exchanger 20 is in communication with the medium in the coolant tank 30. The medium in the heat exchanger 20 absorbs heat from the containment and is discharged into the coolant tank 30 through the steam collection device 40. The medium in the coolant tank 30 returns to the heat exchanger 20, forming a circulation loop.

[0066] As heat is continuously dissipated from the containment vessel, the medium in the coolant tank 30 continuously evaporates, leading to a drop in the liquid level, a decrease in the system's circulation driving force, and a reduction in heat dissipation capacity. To avoid this situation, this application proposes a vapor collection device to eliminate the adverse effects of a drop in liquid level.

[0067] like Figure 2As shown, the steam collecting device 40 includes a steam venting valve assembly 480 corresponding to different liquid levels in the coolant tank 30. The steam venting valve assembly 480 is configured to automatically open under its own force when the liquid level decreases, allowing at least a portion of the medium entering the steam collecting device 40 to enter the coolant tank 30 through the steam venting valve assembly 480. This balances the static pressure difference between the inner and outer sides of the steam collecting device 40, increasing the system's circulation driving force at low liquid levels. The force acting on the steam venting valve assembly 480 in this application mainly includes the buoyancy force and its own weight acting on the assembly in the cooling medium. The cooling medium in this application includes, but is not limited to, water.

[0068] Specifically, the steam collecting device 40 has a cylindrical structure, including a steam collecting pipe 410 and a multi-stage sleeve 420 sleeved on the steam collecting pipe 410. The multi-stage sleeves 420 are distributed along the liquid level height direction. The first-stage sleeve is located at the bottom of the multi-stage sleeve, and the number of stages increases sequentially along the liquid level height. Each sleeve in the multi-stage sleeve 420 can move axially along the steam collecting pipe 410 as the liquid level height changes. It is also configured that when the liquid level height decreases, the multi-stage sleeves move downward in sequence from the higher stage to the lower stage.

[0069] The steam collecting pipe 410 is provided with multi-stage exhaust ports in the height direction. The multi-stage exhaust ports are correspondingly set with multi-stage sleeves. The exhaust port 460 and the sleeve 420 are combined to form the exhaust valve assembly 480. The multi-stage sleeve 420 moves downward in sequence from high to low so that the multi-stage exhaust ports open in sequence from high to low.

[0070] When the coolant level in the tank is higher than the predetermined value, the buoyancy of the cooling medium on the sleeve is greater than its own weight, and the sleeve completely covers the vent, allowing the steam-water mixture entering the steam collector pipe to be discharged from the top. When the coolant level in the tank is lower than the predetermined value and is descending, the buoyancy of the sleeve decreases as the coolant level drops, and its own weight becomes greater than the buoyancy. At least one sleeve moves downward along the axial direction of the steam collector pipe, causing at least one vent to open, and at least a portion of the steam-water mixture entering the steam collector pipe is discharged from the vent.

[0071] The steam collecting device proposed in this application utilizes the change in buoyancy of the sleeve with the liquid level to realize the axial movement of the sleeve along the steam collecting pipe, thereby controlling the automatic opening and closing of the exhaust port, ensuring the heat dissipation capacity of the system at low liquid levels, and promoting the natural circulation of the system.

[0072] In one embodiment of this application, a plurality of limiters 415 are fitted onto the outer wall of the steam collecting pipe 410. The limiters 415 are distributed along the axial direction of the steam collecting pipe 410, dividing the steam collecting pipe 410 into multiple independent regions. Each sleeve in the multi-stage sleeve 420 is independent of each other and is respectively set in each independent region, corresponding to different liquid level heights to respond to changes in the liquid level of the cooling medium. The limiters 415 limit the maximum displacement of the sleeve's vertical movement, preventing the sleeve from detaching from the steam collecting pipe. In this application, the limiters 415 include, but are not limited to, baffle structures.

[0073] When the coolant in the coolant tank 30 is full, all the sleeves will be in the upper limit position under the action of buoyancy, keeping the vent closed. This prevents the steam from the upper outlet of the steam collector from directly contacting the cooling medium in the coolant tank 30. When a large amount of cooling medium in the coolant tank 30 evaporates due to heat dissipation from the passive containment heat removal system, the coolant level drops. First, the sleeve in the uppermost vent valve assembly 480 gradually moves downwards due to the decrease in buoyancy until it reaches the lower limit position. During this process, the corresponding vent is opened, maintaining a basic pressure balance between the inside and outside of the steam collector pipe 410. As the coolant level continues to drop, the remaining sleeves will repeat the action of the uppermost sleeve in sequence, automatically adjusting the opening and closing of the vent in a passive manner. On the one hand, it can avoid destructive risks such as steam hammer vibration and two-phase flow excitation, and at the same time eliminate the adverse effects of the liquid level in the coolant tank 30 on the natural circulation of the system, prevent the natural circulation flow from stagnating, and significantly improve the natural circulation flow rate and flow stability of the system.

[0074] To ensure that the sleeve moves axially along the steam collecting pipe as the buoyancy changes, each sleeve in the multi-stage sleeve 420 is arranged to form a hollow cavity. The buoyancy of the hollow cavity in the coolant tank 30 is greater than the weight of the sleeve.

[0075] In addition, such as Figure 2 As shown, the steam collecting device also includes a guide shroud 430, which is fitted over the multi-stage sleeve 420. The guide shroud 430 is concentrically arranged with the steam collecting pipe 410 to avoid the impact of changes in the coolant level in the coolant tank. A drain port 431 is provided at the bottom of the guide shroud 430. When the steam-water mixture enters the guide shroud 430, causing the coolant level to rise, the cooling medium in the guide shroud 430 is discharged through the drain port 431, reducing the disturbance of the steam-water mixture to the coolant tank level and ensuring the stability of the system's natural circulation drive.

[0076] In addition, a steam-water separation hood 440 is provided at the top of the steam collecting pipe 410, which separates the steam-water mixture flowing out of the outlet of the steam collecting pipe 410. The separated liquid phase enters the guide hood 430 to avoid excessive impact load on the coolant tank by the high-speed fluid at the upper outlet of the steam collecting pipe, and to reduce the entrainment loss of the liquid phase by the steam flow. In this application, the steam-water separation hood 440 has an arc-shaped structure.

[0077] In order to maintain a predetermined distance between the steam-water separator 440 and the guide shroud 430 and improve the steam-water separation effect, the steam collection device also includes a support column 450, which supports the steam-water separator 440.

[0078] To improve the system's heat transfer coefficient and enhance heat transfer performance, this application features an innovative design for the heat exchanger structure, enabling multiple enhanced heat transfer effects to be coupled together.

[0079] Specifically, such as Figure 3 As shown, the heat exchanger 20 includes a first heat transfer tube bundle 230 and a second heat transfer tube bundle 240, which are distributed in a mirror-symmetric manner.

[0080] The heat exchanger 20 also includes a distribution manifold 210 and a manifold 220. The first heat transfer tube bundle 230 is connected to the distribution manifold 210 and the manifold 220, and the second heat transfer tube bundle 240 is connected to the distribution manifold 210 and the manifold 220. The medium enters the first heat transfer tube bundle 230 and / or the second heat transfer tube bundle 240 through the distribution manifold 210 and flows out of the heat exchanger 20 through the manifold 220.

[0081] The second heat transfer tube bundle 240 is symmetrically arranged on both sides of the first heat transfer tube bundle 230 along the axial direction of the distribution manifold 210 and / or the manifold 220. The second heat transfer tube bundle 240, the first heat transfer tube bundle 230, the distribution manifold 210, and the manifold 220 enclose a hollow region where the medium is accelerated. The non-condensable gas entering the upper part of the heat transfer tube bundle flows vertically downward under the action of gravity, forming a relatively high-density fluid acceleration zone in the hollow barrel-shaped region of the heat exchanger. This allows the steam-air mixture to eventually sweep across the lower section of the heat transfer tube bundle at a high flow velocity, thereby further enhancing the external condensation heat transfer of the heat exchanger.

[0082] In addition, such as Figure 4As shown, the distribution manifold 210 and the manifold 220 in the heat exchanger are horizontally arranged, allowing steam containing a large amount of non-condensable gas on the outside of the heat exchanger to smoothly enter the heat transfer tube bundle region and undergo condensation heat transfer. Furthermore, the openings of the distribution manifold 210 and the manifold 220 are located on the same side, which not only minimizes eddy current losses at the heat exchanger inlet / outlet and improves heat transfer capacity, but also facilitates connection of the heat exchanger to other components. Preferably, in this application, both the distribution manifold 210 and the manifold 220 adopt a pipe structure with a cap at one end and an inlet / outlet at the other end. This results in a "U"-shaped flow path for the medium within the heat exchanger, which helps improve the uniformity of flow distribution between the heat transfer tubes, reduces the flow resistance of the heat exchanger, and improves heat transfer capacity.

[0083] Furthermore, in combination Figure 5 and Figure 3 As shown, the first heat transfer tube bundle 230 and / or the second heat transfer tube bundle 240 in this application include multiple heat transfer tube rows 234, which are arranged in parallel. Preferably, in this embodiment, the total number of tube rows is 3 to 5. As steam continues to condense, a pressure difference is formed between the heat transfer tube rows 234 near the hollow region and the heat transfer tube rows 234 far from the hollow region. This pressure difference accelerates the steam flow, thus effectively enhancing heat transfer.

[0084] Additionally, the heat transfer tube bank 234 includes multiple heat transfer tubes 2342, which are arranged axially along the distribution manifold 210 and / or the manifold 220. For example... Figure 5 As shown, adjacent heat transfer tubes form pitches a and b. In this embodiment, pitches a and b can be the same or different. The preferred pitch of the heat transfer tube is 2 to 3 times the diameter of the heat transfer tube, where a is preferably 2 times the diameter of the heat transfer tube and b is preferably 3 times the diameter of the heat transfer tube.

[0085] To further improve heat exchange efficiency, the heat exchanger in this application is composed of unequal-sided C-shaped heat transfer tubes. Specifically, as shown... Figure 6 As shown, the heat transfer tube 2342 includes a first tube section 2344, a second tube section 2346, and an intermediate tube section 2348 connecting the first tube section 2344 and the second tube section 2346. The first tube section 2344 is connected to the manifold 220, and the second tube section 2346 is connected to the distribution manifold 210. Preferably, the length of the first tube section 2344 is less than the length of the second tube section 2346. The angle between the second tube section 2344 and the intermediate tube section 2348 is 60-80°. Thus, the heat exchanger end face has a trapezoidal structure, and the axial direction has a polygonal hollow structure. The non-condensable gas entering the first tube section 2344 and the intermediate tube section 2348 flows vertically downward under the action of gravity, forming a relatively high-density fluid acceleration zone in the hollow area of ​​the heat exchanger. This allows the steam-air mixture to eventually sweep across and scour the lower part of the second tube section 2346 at a high flow velocity, thereby further enhancing the condensation heat transfer of the heat exchanger.

[0086] In addition, such as Figure 3 As shown, the heat exchanger 20 in this application is further provided with supporting baffles 260, which are disposed between the heat transfer tubes 2342 and perpendicular to the middle tube section 2348 of the heat transfer tubes 2342. On the one hand, the supporting baffles 260 serve to support the heat transfer tube bundle and prevent flow excitation of the heat transfer tubes. On the other hand, the supporting baffles 260 guide and divert the condensate outside the tubes and the non-condensable gas accumulated near the tube wall, reducing the thickness of the condensate film and the non-condensable gas film, thereby reducing the heat transfer resistance and enhancing the heat transfer effect. Preferably, the heat exchanger in this application includes multiple supporting baffles 260, which are long and narrow strips, and the spacing between adjacent guiding supporting baffles is preferably greater than 0.5m.

[0087] On the other hand, such as Figure 1 As shown, the containment heat removal system also includes an ascender section 50 and a descender section 60. The ascender section 50 connects to the manifold 220 and the coolant tank 30, while the descender section 60 connects to the coolant tank 30 and the distribution manifold 210. The descender section 60, the ascender section 50, and the heat exchanger 20 constitute the main flow resistance components of the containment heat removal system. During design, the proportion of each flow resistance component should be reasonably allocated to avoid one or two components having an excessively large proportion. Preferably, the diameter of the ascender section 50 should be larger than the diameter of the descender section 60 to ensure that the loop does not suffer from insufficient natural circulation capacity due to excessive flow resistance, thereby reducing the system's heat dissipation capacity.

[0088] In addition, the containment heat removal system also includes isolation valves located in the riser section 50 and the downcomer section 60, respectively. Under normal circumstances, these valves remain open. When a leak occurs in the pipeline or equipment located inside the containment in the containment heat removal system, the isolation valves are closed to maintain the integrity of the containment pressure boundary and prevent radioactive materials inside the containment from leaking into the external environment.

[0089] The following provides a detailed description of the composition of the containment heat removal system.

[0090] The heat exchanger 20 is mounted on the inner wall of the containment vessel, above the operating platform. The coolant tank 30 is positioned outside the containment vessel, higher than the heat exchanger 20, to maintain a sufficient height difference between them. The upper end of the downcomer section 60 is connected to the outlet of the coolant tank 30, and the lower end is connected to the inlet of the heat exchanger 20. Correspondingly, the upper end of the riser section 50 is connected to the inlet of the coolant tank 30, and the lower end is connected to the outlet of the heat exchanger 20. The steam collector 40 is installed inside the coolant tank 30, which is connected to the outlet of the riser section 50 via a flange located at its bottom. Isolation valves on both the downcomer section 60 and the riser section 50 are located outside the containment vessel.

[0091] When the containment heat removal system is in operation, the coolant in the coolant tank 30 flows into the tube side of the heat exchanger 20 through the downcomer section 60. Steam inside the containment condenses on the outer surface of the heat transfer tubes in the heat exchanger 20, releasing latent heat of vaporization which is transferred to the coolant in the tubes, causing its temperature to rise continuously during flow. The heated cooling medium then enters the riser section 50 until it flows back to the coolant tank 30. The flow of the medium in the system is driven solely by the density difference between the medium in the downcomer section 60 and the riser section 50, without external power input, and is in a natural circulation state. When the temperature of the cooling medium in the coolant tank is low, the system is in a single-phase natural circulation state, transferring the decay heat from the containment to the coolant tank 30. When the temperature of the cooling medium in the coolant tank 30 rises to the saturation temperature at the local pressure, the system enters a two-phase natural circulation state, and the resulting steam-water mixture is discharged into the atmosphere through the vent on the coolant tank 30, achieving passive heat removal.

[0092] Based on the completed individual experimental results and the experimentally verified calculation and analysis program, a comparative calculation and analysis was conducted on the containment heat removal system under the preferred scheme of this invention and the prior art, and the changes in the heat dissipation power of a single heat exchanger with the containment pressure were obtained as follows: Figure 7 As shown, the pressure change within the containment vessel over time under the most severe hypothetical reactor accident is obtained as follows: Figure 8 As shown, the heat exchange power of a single heat exchanger in this invention is several times higher than that of a single heat exchanger in the prior art. The system of this invention ensures that the pressure inside the containment can drop to less than half of the design pressure (0.52 MPa absolute pressure) within 24 hours after an accident and remain stable for a long period of time, meeting the requirements for responding to baseline accidents. In contrast, the system based on the prior art can only control the pressure inside the containment to fluctuate around 0.35 MPa, which only meets the needs of responding to accidents exceeding the design baseline.

[0093] In summary, the containment heat removal system proposed in this embodiment achieves the following technical effects:

[0094] 1. The steam collection device used in the containment heat removal system of the present invention can not only completely eliminate the risks of steam hammer vibration, two-phase flow excitation and flow stagnation during the steam-liquid two-phase flow stage, but also automatically balance the static pressure difference between the inner and outer sides of the steam collection pipe in a passive manner, thereby eliminating the adverse effects of the coolant tank level on the natural circulation flow of the passive containment heat removal system.

[0095] 2. The heat exchanger used in the containment heat removal system of the present invention not only significantly reduces flow resistance without increasing the manufacturing difficulty of the heat exchanger, but also has a compact structure and significantly enhances heat transfer inside and outside the heat transfer tube, making it a high-efficiency heat exchanger with low flow resistance and strong heat exchange capacity.

[0096] 3. By optimizing the configuration of the containment heat removal system, this invention significantly enhances the system's flow stability and natural circulation capability, and substantially improves the heat removal power level of the passive containment heat removal system, enabling it to cope with reactor baseline accidents.

[0097] 4. The containment heat removal system of the present invention has a simple composition, the steam collection device is easy to disassemble and assemble, and the system has strong stability. Example 2

[0098] The containment heat removal system in this embodiment is basically the same as that in Embodiment 1, such as... Figure 9 As shown, the sleeve 420 and the exhaust port 460 located on the outer wall of the steam collecting pipe 410 constitute the exhaust valve assembly 480. The difference lies in the combination... Figure 10 and Figure 11 As shown, in this embodiment, the inner diameter of the upper-level sleeve 420 is larger than the outer diameter of the lower-level sleeve, and adjacent sleeves 420 are nested together. The upper-level sleeve can move along the outer wall of the lower-level sleeve.

[0099] To prevent the multi-stage sleeve 420 from detaching from the steam collecting pipe 410, this application proposes a limiting structure for the steam collecting device.

[0100] Specifically, such as Figure 12 As shown, the steam collecting device includes a first positioning part 416, which is sleeved on the outside of the steam collecting pipe 410. The first positioning part 416 defines the highest position of the multi-stage sleeve, preventing the multi-stage sleeve from detaching from the upper part of the steam collecting pipe 410. In this application, the first positioning part 416 is located in the lower region of the steam collecting pipe. Preferably, the first positioning part 416 is welded to the outside of the steam collecting pipe 410, and the first positioning part 416 has an annular structure. The outer diameter of the first positioning part 416 is equal to the inner diameter of the first-stage sleeve.

[0101] The first positioning part 416 defines a steam exhaust area along the axial direction of the steam collecting pipe 410 above it, such as... Figure 10 As shown, a reinforcing ring 411 is provided on the outer wall of the steam collection pipe 410 corresponding to the exhaust area to enhance the stability of the steam collection pipe 410.

[0102] In addition, such as Figure 10 As shown, the steam collecting device also includes a fourth positioning part 418, which is sleeved on the outside of the steam collecting pipe 410. The fourth positioning part 418 limits the lowest position of the multi-stage sleeve 420 to prevent the multi-stage sleeve 420 from detaching from the lower part of the steam collecting pipe 410.

[0103] In this application, the fourth positioning part 418 is a limiting flange. The fourth positioning part 418 is located at the bottom of the steam collecting pipe 10 near the inlet and is lower than the position of the first positioning part 146.

[0104] Combination Figure 10 and Figure 12 As shown, the first positioning part 416 and the fourth positioning part 418 define a non-exhaust area along the axial direction of the steam collecting pipe 410, while the first positioning part 416 and above define an exhaust area along the axial direction of the steam collecting pipe 410. No exhaust port is provided on the outer wall of the steam collecting pipe in the non-exhaust area, but an exhaust port is provided on the outer wall of the steam collecting pipe in the exhaust area.

[0105] like Figure 10 As shown, the maximum axial length of the multi-stage sleeve 420 along the steam collecting pipe 410 is not less than the axial length of the exhaust area along the steam collecting pipe 410. When the coolant tank is full, the height of the multi-stage hollow sleeve is not less than the height of the steam collecting pipe 410. The multi-stage hollow sleeve can completely cover each exhaust port 460 in the exhaust area, exposing the non-exhaust area. In addition, the height of the first-stage sleeve is greater than the axial length of the non-exhaust area along the steam collecting pipe. When there is no coolant in the coolant tank, the first-stage sleeve can completely cover the non-exhaust area.

[0106] In addition, to prevent disengagement between multi-stage sleeves, this application provides positioning parts for each stage of the sleeve.

[0107] Specifically, such as Figure 13 As shown, each sleeve has a second positioning part 422 at its top. The second positioning parts 422 of adjacent sleeves are in contact with each other to prevent the upper sleeve from detaching from the bottom of the lower sleeve. Preferably, the second positioning part 422 of this application has an annular structure, and the inner diameter of the second positioning part 422 is equal to the outer diameter of the steam collecting pipe 410, and the outer diameter of the second positioning part 422 is equal to the inner diameter of the upper sleeve.

[0108] In addition, each sleeve has a third positioning part 424 at its bottom. The third positioning part 424 of the upper sleeve contacts the second positioning part 422 of the lower sleeve to prevent the upper sleeve from disengaging from the lower sleeve when it moves upward. Preferably, the third positioning part 424 in this application has an annular structure, and the inner diameter of the third positioning part 424 is equal to the outer diameter of the lower sleeve. The outer diameter of the third positioning part 424 is the outer diameter of the sleeve at that stage.

[0109] In this application, the second positioning part 422 and the third positioning part 424 are detachably connected to each stage of the sleeve 420. Preferably, the second positioning part 422 and the third positioning part 424 are fixed to the sleeve 420 by rivets, which facilitates disassembly and assembly.

[0110] When the buoyancy of the upper-level sleeve exceeds its own weight, the upper-level sleeve moves upward and attempts to escape from the lower-level sleeve. At this time, the second positioning part of the lower-level sleeve abuts against the third positioning part of the upper-level sleeve to prevent the upper-level sleeve from detaching from the top of the lower-level sleeve. The third positioning part of the lowest-level sleeve abuts against the first positioning part to prevent the multi-stage sleeves from detaching from the steam collecting pipe under the action of buoyancy.

[0111] When the buoyancy of the upper-level sleeve is less than its own weight, the upper-level sleeve moves downward and attempts to escape from the lower-level sleeve. At this time, the second positioning part of the lower-level sleeve abuts against the second positioning part of the upper-level sleeve, preventing the upper-level sleeve from leaving the bottom of the lower-level sleeve. The multi-stage sleeves move downward sequentially from high to low, eventually landing above the fourth positioning part.

[0112] In summary, the steam collecting device proposed in this embodiment achieves the following technical effects:

[0113] 1. Under the influence of buoyancy and its own weight in the cooling medium, the sleeve moves axially along the steam collecting pipe following the liquid level change, realizing the opening and closing of the exhaust port and ensuring the system's heat dissipation capacity at low liquid levels; 2. The multi-stage nested sleeve method and the setting of multiple positioning plates prevent the multi-stage sleeves from detaching from each other, ensuring the stability of the structure; 3. The containment heat conduction steam collecting device proposed in this application has a simple structure and is easy to disassemble and maintain; 4. By optimizing the multi-stage sleeve structure, the multi-stage sleeves completely block the exhaust area, increasing the height of the rising section, thereby increasing the length of the natural circulation two-phase section and increasing the system's driving force and heat dissipation capacity.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A containment heat removal system, comprising a heat exchanger (20) disposed inside the containment, a coolant tank (30), and a steam collection device (40) disposed in the coolant tank (30), wherein the heat exchanger (20) is in communication with a medium in the coolant tank (30), the medium in the heat exchanger (20) absorbs heat from the containment and discharges it into the coolant tank (30) through the steam collection device (40), and the medium in the coolant tank (30) returns to the heat exchanger (20). It is characterized in that The steam collection device (40) includes a steam exhaust valve assembly (480) corresponding to different liquid levels in the coolant tank (30). The steam exhaust valve assembly (480) is configured to automatically open under its own force when the liquid level decreases, so that at least part of the medium entering the steam collection device (40) enters the coolant tank (30) through the steam exhaust valve assembly (480) to balance the static pressure difference between the inside and outside of the steam collection device (40) and increase the system circulation driving force at low liquid levels.

2. The containment heat removal system according to claim 1, characterized in that, The steam collecting device (40) includes a steam collecting pipe (410) and a multi-stage sleeve sleeved on the steam collecting pipe (410). The multi-stage sleeves are distributed along the liquid level height direction. The first-stage sleeve is located at the bottom of the multi-stage sleeves, and the number of stages increases sequentially along the liquid level height. Each sleeve in the multi-stage sleeves can move axially along the steam collecting pipe (410) as the liquid level height changes. It is configured that when the liquid level height decreases, the multi-stage sleeves move downward in sequence from the higher stage to the lower stage.

3. The containment heat removal system according to claim 2, characterized in that, The steam collecting pipe (410) is provided with a multi-stage exhaust port in the height direction. The multi-stage exhaust port is correspondingly provided with the multi-stage sleeve. The exhaust port (460) and the sleeve (420) are combined to form the exhaust valve assembly (480). The multi-stage sleeve moves downward in sequence from high to low level so that the multi-stage exhaust port opens in sequence from high to low.

4. The containment heat removal system according to claim 3, characterized in that, Multiple limiters (415) are fitted on the outer wall of the steam collecting pipe (410). The limiters (415) are distributed along the axial direction of the steam collecting pipe (410) to divide the steam collecting pipe (410) into multiple independent regions. The multi-stage sleeves are respectively set in each of the independent regions.

5. The containment heat removal system according to claim 4, characterized in that, Each of the sleeves (420) in the multi-stage sleeve is independent of each other and corresponds to a different liquid level.

6. The containment heat removal system according to claim 2 or 3, characterized in that, Each of the sleeves (420) in the multi-stage sleeve is arranged to form a hollow cavity, and the buoyancy of the hollow cavity in the coolant tank (30) is greater than the weight of the sleeve (420).

7. The containment heat removal system according to claim 3, characterized in that, In the multi-stage sleeve, the inner diameter of the upper-stage sleeve is larger than the outer diameter of the lower-stage sleeve, and adjacent sleeves are nested together. The upper-stage sleeve can move along the outer wall of the lower-stage sleeve.

8. The containment heat removal system according to claim 3, characterized in that, It includes a first positioning part (416), which is sleeved on the outside of the steam collecting pipe (410). The first positioning part (416) defines the highest position of the multi-stage sleeve and prevents the multi-stage sleeve from detaching from the upper part of the steam collecting pipe (410).

9. The containment heat removal system according to claim 8, characterized in that, The first positioning part (416) defines a steam exhaust area along the axial direction of the steam collecting pipe (410) above it. The outer wall of the steam collecting pipe (410) corresponding to the steam exhaust area is provided with a reinforcing ring (411) to enhance the stability of the steam collecting pipe (410).

10. The containment heat removal system according to claim 9, characterized in that, The maximum axial length of the multi-stage sleeve along the steam collecting pipe (410) is not less than the axial length of the exhaust area along the steam collecting pipe (410), so that the multi-stage sleeve can completely cover each of the exhaust ports (460) within the length range of the steam collecting pipe (410).

11. The containment heat removal system according to claim 2 or 3, characterized in that, It also includes a fourth positioning part (418), which is sleeved on the outside of the steam collecting pipe (410). The fourth positioning part (418) limits the lowest position of the multi-stage sleeve to prevent the multi-stage sleeve from detaching from the lower part of the steam collecting pipe (410).

12. The containment heat removal system according to claim 2 or 3, characterized in that, Each sleeve has a second positioning part (422) at the top. The second positioning parts (422) of adjacent sleeves are in contact with each other to prevent the upper sleeve from detaching from the bottom of the lower sleeve.

13. The containment heat removal system according to claim 12, characterized in that, Each level of sleeve is provided with a third positioning part (424) at the bottom. The third positioning part (424) of the upper level sleeve contacts the second positioning part (422) of the lower level sleeve to prevent the upper level sleeve from disengaging from the lower level sleeve when it moves upward.

14. The containment heat removal system according to claim 12, characterized in that, The inner diameter of the second positioning part (422) is equal to the outer diameter of the steam collecting pipe (410), and the outer diameter of the second positioning part (422) is equal to the inner diameter of the sleeve of the previous stage.

15. The containment heat removal system according to claim 13, characterized in that, The inner diameter of the third positioning part (424) is equal to the outer diameter of the next-level sleeve, and the outer diameter of the third positioning part (424) is the outer diameter of the sleeve of that level.

16. The containment heat removal system according to claim 9, characterized in that, The outer diameter of the first positioning part (416) is equal to the inner diameter of the first-stage sleeve.

17. The containment heat removal system according to claim 2 or 3, characterized in that, It also includes a flow deflector (430), which is fitted over the outside of the multi-stage sleeve.

18. The containment heat removal system according to claim 17, characterized in that, The bottom of the flow guide (430) is provided with a drain port (431), through which the cooling medium in the flow guide (430) is discharged to reduce disturbance to the liquid level.

19. The containment heat removal system according to claim 18, characterized in that, The top of the steam collecting pipe (410) is provided with a steam-water separation hood (440), which separates the steam-water mixture flowing out of the outlet of the steam collecting pipe (410) from the water.

20. The containment heat removal system according to claim 19, characterized in that, It also includes a support column (450) that supports the steam-water separator (440) so that the steam-water separator (440) and the guide shield (430) maintain a predetermined distance.

21. The containment heat removal system according to claim 1, characterized in that, The heat exchanger (20) includes a first heat transfer tube bundle (230) and a second heat transfer tube bundle (240), which are distributed in a mirror-symmetric manner.

22. The containment heat removal system according to claim 21, characterized in that, The heat exchanger (20) further includes a distribution manifold (210) and a manifold (220). The first heat transfer tube bundle (230) is connected to the distribution manifold (210) and the manifold (220). The second heat transfer tube bundle (240) is connected to the distribution manifold (210) and the manifold (220). The medium enters the first heat transfer tube bundle (230) and / or the second heat transfer tube bundle (240) through the distribution manifold (210) and flows out of the heat exchanger (20) through the manifold (220).

23. The containment heat removal system according to claim 22, characterized in that, The second heat transfer tube bundle (240) is symmetrically arranged on both sides of the axial direction of the distribution manifold (210) and / or the manifold (220) with the first heat transfer tube bundle (230). The second heat transfer tube bundle (240), the first heat transfer tube bundle (230), the distribution manifold (210) and the manifold (220) form a hollow region in which the medium is accelerated.

24. The containment heat removal system according to claim 23, characterized in that, The distribution manifold (210) and the junction manifold (220) are arranged horizontally, and the openings of the distribution manifold (210) and the junction manifold (220) are located on the same side.

25. The containment heat removal system according to claim 23 or 24, characterized in that, The first heat transfer tube bundle (230) and / or the second heat transfer tube bundle (240) include a plurality of heat transfer tube rows (234), which are arranged in parallel. A pressure difference is formed between the heat transfer tube rows (234) near the hollow region and the heat transfer tube rows (234) away from the hollow region to accelerate the flow of the medium.

26. The containment heat removal system according to claim 25, characterized in that, The heat transfer tube bank (234) includes multiple heat transfer tubes (2342) arranged axially along the distribution manifold (210) and / or the manifold (220).

27. The containment heat removal system according to claim 26, characterized in that, The heat transfer pipe (2342) includes a first pipe section (2344), a second pipe section (2346), and an intermediate pipe section (2348) connecting the first pipe section (2344) and the second pipe section (2346). The first pipe section (2344) is connected to the manifold (220), and the second pipe section (2346) is connected to the distribution manifold (210).

28. The containment heat removal system according to claim 27, characterized in that, The length of the first pipe segment (2344) is less than the length of the second pipe segment (2346).

29. The containment heat removal system according to claim 28, characterized in that, The angle between the second pipe section (2344) and the intermediate pipe section (2348) is 60-80°.

30. The containment heat removal system according to any one of claims 26-28, characterized in that, The spacing between adjacent heat transfer tubes (2342) is 2 to 3 times the diameter of the heat transfer tube (2342).

31. The containment heat removal system according to claim 26 or 27, characterized in that, The heat exchanger (20) includes a support partition (260) disposed between the heat transfer tubes (2342) and perpendicular to the middle section (2348) of the heat transfer tubes (2342).

32. The containment heat removal system according to any one of claims 22-24, characterized in that, It also includes an ascending pipe section (50) and a descending pipe section (60), the ascending pipe section (50) connecting the manifold (220) and the coolant tank (30), and the descending pipe section (60) connecting the coolant tank (30) and the distribution manifold (210).

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