Passive containment venting system for pressurized water reactor

Abstract

The application discloses a kind of non-powered pressurized water reactor containment pressure relief system, non-powered pressurized water reactor containment pressure relief system includes at least two units, pressure relief device and residual heat removal device, each the unit is correspondingly provided with at least one first containment, the containment of the unit is connected with the first containment of another unit by pipeline, the pressure relief device is arranged on the pipeline to control the opening and closing of the pipeline, the preset trigger threshold of the pressure relief device is positively correlated with the rated design pressure of the first containment, the residual heat removal device is arranged in the first containment of the unit, and the residual heat removal device is connected with the first containment to lead out the heat of the first containment. The non-powered pressurized water reactor containment pressure relief system provided by the application has the advantages of flexible configuration, stable operation and low failure risk.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant safety equipment technology, and in particular to a passive pressurized water reactor containment depressurization system. Background Technology

[0002] The containment vessel of a pressurized water reactor (PWR) is the last safety barrier in a PWR nuclear power plant to control the release of radioactive materials into the environment, and is a critical piece of equipment for ensuring nuclear safety. When a nuclear power plant experiences certain design-basis accidents or even over-design accidents, the reactor primary circuit pressure boundary fails, and a large amount of high-temperature, high-pressure radioactive steam, non-condensable gases, and aerosols are rapidly released into the containment atmosphere. This causes a rapid rise in temperature and pressure within the containment. If appropriate measures are not taken to remove the heat released into the containment after the accident and reduce the temperature and pressure, the integrity of the last barrier of the nuclear power plant will be seriously jeopardized, leading to the risk of radioactive leakage. Among related technologies, the European Advanced Pressurized Water Reactor (EPR) represents a solution that uses multiple redundant active containment cooling systems to eliminate or mitigate the risk of containment failure. However, this approach has certain drawbacks: excessive redundancy leads to the high cost of the EPR; and if all power is lost, all heat sinks are lost, or active equipment experiences a common cause failure, the containment may lose cooling after the accident and ultimately fail. Technical solutions represented by AP1000, which use passive safety systems, have drawbacks such as slow system startup, uncontrollable system parameters, and inability to shut down in time after accidental triggering. In non-accident situations, daily operation and maintenance are cumbersome and pose industrial safety hazards. Summary of the Invention

[0003] The present invention aims to at least partially solve one of the technical problems in the related art.

[0004] Therefore, embodiments of the present invention propose a passive pressurized water reactor containment depressurization system, which has advantages such as flexible configuration, stable operation, and low failure risk. According to embodiments of the present invention, the passive pressurized water reactor containment depressurization system includes at least two reactor units, a depressurization device, and a residual heat removal device. Each reactor unit has at least one first containment. The containment of one reactor unit is connected to the first containment of the other reactor unit via a pipeline. The depressurization device is located on the pipeline to control its opening and closing. The preset trigger threshold of the depressurization device is positively correlated with the rated design pressure of the first containment. The residual heat removal device is located in the first containment of the reactor unit and connected to the first containment to remove heat from the first containment.

[0005] The passive pressurized water reactor containment depressurization system according to embodiments of the present invention has the advantages of flexible configuration, stable operation and low failure risk.

[0006] In some embodiments, the pressure relief device includes a gate valve, a connecting rod, and a pressure accumulator. The gate valve is located inside the pipeline. A first end of the connecting rod is connected to the gate valve, and a second end of the connecting rod is connected to the pressure accumulator. When the pressure inside the first containment is greater than a preset trigger threshold, the gate valve opens to relieve pressure. When the pressure inside the first containment is less than the preset trigger threshold, the gate valve closes.

[0007] In some embodiments, the accumulator includes a sleeve, a sealing ring, and a central baffle. The central baffle is connected to the second end of the connecting rod. As the gate valve is opened and closed, the connecting rod drives the central baffle to move within the sleeve. The sealing ring is disposed between the central baffle and the sleeve.

[0008] In some embodiments, a second containment is provided between the first containment of the unit and the first containment of another unit, and the second containment is connected to the first containment of the two units via pipelines.

[0009] In some embodiments, the passive pressurized water reactor containment relief system further includes a third containment, with a plurality of first containments and second containments arranged in a ring around the third containment, the second containments being staggered with the first containments, the first containment being connected to two adjacent second containments via pipelines, and the plurality of second containments being connected to the third containment via pipelines.

[0010] In some embodiments, the trigger threshold of the pressure relief device on the pipe connected to the second containment is 50% of the rated design pressure of the first containment.

[0011] In some embodiments, check valves are provided on the pipeline between the first containment and the adjacent second containment and on the pipeline between the second containment and the third containment.

[0012] In some embodiments, the elevation of the second containment and / or the third containment is 5 to 15 meters lower than the height of the first containment.

[0013] In some embodiments, the waste heat removal device is also provided on the second containment and the third containment.

[0014] In some embodiments, the preset trigger threshold of the pressure relief device is 75% of the rated design pressure of the first containment. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a passive pressurized water reactor containment depressurization system according to an embodiment of the present invention.

[0016] Figure 2 This is a schematic diagram of a passive pressurized water reactor containment depressurization system according to another embodiment of the present invention.

[0017] Figure 3 This is a schematic diagram of a passive pressurized water reactor containment depressurization system according to another embodiment of the present invention.

[0018] Reference numerals: 1. First containment; 2. Second containment; 3. Third containment; 4. Pressure relief device. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] The pressurized water reactor (PWR) in this invention primarily uses water (liquid light water) as both coolant and moderator. The different properties of the coolant and moderator compared to a liquid metal reactor (LMR) result in different containment design and connection methods. The solid beryllium moderator in LMRs is highly toxic and unsuitable for through-hole connections. Radioactive products leaked from a PWR mainly include water, hydrogen, and actinides. The free volume of the containment determines its overall volume. In the event of a PWR accident, cooling can be achieved through water immersion. Unlike PWRs, LMRs, due to sodium-water reactions, require external energy sources to operate the waste heat removal system. PWRs use liquid water as both coolant and moderator, with a primary loop operating pressure as high as 15.5 MPa. This places high demands on the containment's rated pressure and pressure relief components, typically requiring a larger free volume containment with added prestressed steel reinforcement. The chemical properties of the working fluid, water, are relatively stable, and hydrogen produced by water irradiation can be ignited within the containment using an open flame.

[0021] like Figures 1 to 3As shown, according to an embodiment of the present invention, the passive pressurized water reactor containment depressurization system includes at least two reactor units, a depressurization device 4, and a residual heat removal device. Each reactor unit has at least one first containment 1. The first containment 1 of one reactor unit is connected to the first containment 1 of the other reactor unit via a pipeline. The depressurization device 4 is located on the pipeline to control the opening and closing of the pipeline. The preset trigger threshold of the depressurization device 4 is positively correlated with the rated design pressure of the first containment 1. The residual heat removal device is located on the first containment 1 of the reactor unit and is connected to the first containment 1 to remove heat from the first containment 1. The first containment 1s of the two reactor units serve as backup containment 1s for each other. If one reactor unit experiences an accident, the temperature and pressure inside the first containment 1 of the affected reactor unit will rise. When the pressure in the first containment vessel 1 of the affected unit exceeds the preset trigger threshold of the pressure relief device 4, the device is activated. High-temperature, high-pressure steam and non-condensable gases from the first containment vessel 1 of the affected unit are discharged along the pressure gradient into the first containment vessel 1 of the unaffected unit. Since the two first containment vessels 1 are connected, their total volume increases. According to the ideal gas law, within the large containment space, the volume change is insufficient to cause a significant change in macroscopic temperature. Therefore, the temperature change due to the volume change is negligible; that is, the volume increases, and the pressure decreases rapidly. Furthermore, during the subsequent long-term cooling process, two residual heat removal devices can operate simultaneously, removing heat from the first containment vessels 1 of both units. The temperature of the gas phase space within the first containment vessel 1 decreases, and water vapor is rapidly condensed into liquid, further reducing the pressure within the first containment vessel 1. This achieves the goal of controlling the accident process and mitigating its consequences. Connecting the first containment vessels 1 of the two units to form a double containment pressure relief system is suitable for nuclear power plants that have already been designed and constructed, and the impact of retrofitting on daily operations is minimal.

[0022] The passive pressurized water reactor containment depressurization system according to embodiments of the present invention has the advantages of flexible configuration, stable operation and low failure risk.

[0023] In some embodiments, the pressure relief device 4 includes a gate valve, a connecting rod, and a pressure accumulator. The gate valve is located inside the pipeline. The first end of the connecting rod is connected to the gate valve, and the second end of the connecting rod is connected to the pressure accumulator. When the pressure inside the first containment 1 is greater than a preset trigger threshold, the gate valve opens to relieve pressure. When the pressure inside the first containment 1 is less than the preset trigger threshold, the gate valve closes.

[0024] Specifically, the accumulator can be filled with a large amount of nitrogen. Under normal circumstances, the pressure inside the first containment vessel 1 should be equal to or slightly lower than atmospheric pressure to form a negative pressure zone. This negative pressure zone can prevent the leakage of radioactive materials. At this time, the pressure inside the first containment vessel 1 is insufficient to actuate the gate valve, and the pressure relief device 4 remains closed. When an accident occurs, due to the leakage of a large amount of steam into the first containment vessel 1, the pressure and temperature of the first containment vessel 1 rise significantly. At this time, the sum of the pressure inside the accumulator and the weight of the pressure relief device 4 itself is less than the vertical component of the pressure in the first containment vessel 1. The pressure relief device 4 is triggered and opens the gate valve to perform pressure relief. As the pressure relief proceeds, when the pressure inside the first containment vessel 1 drops below the preset trigger threshold and is insufficient to open the gate valve, the gate valve closes.

[0025] In some embodiments, the accumulator includes a sleeve, a sealing ring, and a central baffle. The central baffle is connected to the second end of a connecting rod. As the gate valve opens and closes, the connecting rod drives the central baffle to move within the sleeve. The sealing ring is disposed between the central baffle and the sleeve.

[0026] Specifically, the central baffle slides relative to the inner wall of the sleeve. The central baffle is connected to the second end of the connecting rod. The connecting rod drives the central baffle to move inside the sleeve to change the size of the space inside the sleeve. When the amount of gas inside the sleeve is constant, the gas volume decreases and the gas pressure increases as the central baffle moves, eventually achieving the equilibrium position of the central baffle. The sealing ring is set on the central baffle to ensure the sealing effect.

[0027] In some embodiments, such as Figure 2 As shown, a second containment 2 is provided between the first containment 1 of the unit and the first containment 1 of another unit, and the second containment 2 is connected to the first containment 1 of the two units through pipelines.

[0028] Specifically, the first containment 1 of the two units is connected by the second containment 2. The second containment 2 can be an empty containment. After an accident occurs in one unit, the temperature and pressure inside the first containment 1 of the unit that is in the accident rise. When the pressure inside the first containment 1 of the unit that is in the accident exceeds the threshold of the pressure relief device 4, the pressure relief device 4 is triggered. The high temperature and high pressure steam and non-condensable gases inside the first containment 1 of the unit that is in the accident are discharged into the second containment 2 along the pressure gradient. Since the total volume of the containment increases, according to the ideal gas law, the change in volume is not enough to cause a significant change in macroscopic temperature in the large space of the containment. Therefore, the temperature change caused by the change in volume can be ignored. That is, the volume increases and the pressure drops rapidly. In the subsequent long-term cooling process, it is decided whether to discharge steam from the second containment 2 into the first containment 1 of the unit that is not in the faulty unit.

[0029] In some embodiments, such as Figure 3As shown, the passive pressurized water reactor containment depressurization system also includes a third containment 3. Multiple first containments 1 and second containments 2 are arranged in a ring around the third containment 3. The second containments 2 are staggered with the first containments 1. The first containment 1 is connected to two adjacent second containments 2 through pipelines. Multiple second containments 2 are connected to the third containment 3 through pipelines.

[0030] Specifically, multiple first containment vessels 1 form a ring array. A third containment vessel 3 is located in the middle of the ring array as a common containment vessel to store and cool high-temperature, high-pressure, flammable and explosive gases such as hydrogen. Second containment vessels 2 are separated from first containment vessels 1. The second and third containment vessels 2 and 3 may not house power generation equipment such as reactors or turbines, but only safety-related equipment and systems. In the event of an accident in one unit, the temperature and pressure inside the first containment vessel 1 of the unit experiencing the accident rise. When the pressure in the first containment vessel 1 exceeds the threshold of the pressure relief device 4, the pressure relief device 4 is triggered, releasing the high-temperature, high-pressure steam and non-condensable gases from the first containment vessel 1 into the second containment vessel 2 along the pressure gradient. Due to the increased overall volume of the containment vessels, according to the ideal gas law, the volume change within the large space of the containment vessel is insufficient to cause a significant change in macroscopic temperature. Therefore, the temperature change caused by the volume change is negligible; that is, the volume increases, and the pressure decreases rapidly. Furthermore, during the subsequent long-term cooling process, the decision to release steam from the second containment vessel 2 into the third containment vessel 3 is made based on the situation. Even if multiple first containment vessels 1 experience accidents, high-temperature gases can be vented into the second containment vessel 2 and the third containment vessel 3 to ensure the safety of the nuclear power plant. Preferably, the third containment vessel 3 is used as a backup under normal operating conditions and is only put into use in the event of an accident.

[0031] In some embodiments, such as Figure 2 As shown, the trigger threshold of the pressure relief device 4 on the pipeline connected to the second containment 2 is 50% of the rated design pressure of the first containment 1.

[0032] Specifically, the pressure relief device 4 adopts a passive triggering design, the pressure of the accumulator is equivalent to the preset triggering threshold, and the engineering margin is increased by 10%.

[0033] In some embodiments, such as Figure 2 and Figure 3 As shown, check valves are installed on the pipeline between the first containment 1 and the adjacent second containment 2, and on the pipeline between the second containment 2 and the third containment 3.

[0034] Specifically, the check valve adopts a shaft seal or gas seal design. Without the input of external energy to change the flow direction, the airflow direction is from the first safety housing 1 to the second safety housing 2, and from the second safety housing 2 to the third safety housing 3.

[0035] In some embodiments, such as Figure 2 and Figure 3 As shown, the elevation of the second containment 2 and / or the third containment 3 is 5 to 15 meters lower than the height of the first containment 1.

[0036] Specifically, the first containment 1 is the containment for normal operation, and the second containment 2 and the third containment 3 are at lower elevations than the first containment 1 so that the containment can be distinguished. When necessary, the second containment 2 and the third containment 3 can be directly externally cooled.

[0037] In some embodiments, the waste heat removal device is also provided on the second containment 2 and the third containment 3.

[0038] Specifically, the residual heat removal device can cool the second containment 2 and the third containment 3, ensuring that the reactor's heat can still be successfully removed even under accident conditions.

[0039] In some embodiments, the second containment 2 and the third containment 3 are directly cooled externally. The cooling methods include high-pressure fluid convection flushing and direct submersion of cooling water such as seawater or fresh water, to ensure that even under accident conditions, the heat of the reactor can still be smoothly discharged and exchanged with the final heat sink.

[0040] In some embodiments, the preset trigger threshold of the pressure relief device 4 is 75% of the rated design pressure of the first containment 1.

[0041] Specifically, the pressure relief device 4 adopts a passive triggering design, the pressure of the accumulator is equivalent to the preset triggering threshold, and the engineering margin is increased by 10%.

[0042] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0044] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0045] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0046] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0047] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A passive pressurized water reactor containment depressurization system, characterized in that, include: At least two units, each of the units having at least one first containment, the containment of one unit being connected to the first containment of the other unit via a pipeline; A pressure relief device is provided on the pipeline to control the opening and closing of the pipeline. The preset trigger threshold of the pressure relief device is positively correlated with the rated design pressure of the first containment. The pressure relief device includes a gate valve, a connecting rod, and a pressure accumulator. The gate valve is located inside the pipeline. The first end of the connecting rod is connected to the gate valve, and the second end of the connecting rod is connected to the pressure accumulator. When the pressure inside the first containment is greater than the preset trigger threshold, the gate valve opens to relieve pressure. When the pressure inside the first containment is less than the preset trigger threshold, the gate valve closes. The pressure relief device adopts a passive triggering design. The pressure in the pressure accumulator is equivalent to the preset trigger threshold and has an additional 10% engineering margin. The pressure accumulator includes a sleeve, a sealing ring, and a central baffle. The central baffle is connected to the second end of the connecting rod. As the gate valve opens and closes, the connecting rod moves the central baffle within the sleeve. The sealing ring is disposed between the central baffle and the sleeve. Waste heat removal device, wherein the waste heat removal device is disposed in the first containment of the unit, and the waste heat removal device is connected to the first containment to remove heat from the first containment.

2. The passive pressurized water reactor containment depressurization system according to claim 1, characterized in that, A second containment is provided between the first containment of the unit and the first containment of the other unit, and the second containment is connected to the first containment of the two units through pipelines.

3. The passive pressurized water reactor containment depressurization system according to claim 2, characterized in that, It also includes a third containment, with multiple first containment and second containment units arranged in a ring around the third containment, the second containment units being staggered with the first containment units, the first containment units being connected to two adjacent second containment units via pipelines, and multiple second containment units being connected to the third containment unit via pipelines.

4. The passive pressurized water reactor containment depressurization system according to claim 3, characterized in that, The trigger threshold of the pressure relief device on the pipeline connected to the second containment is 50% of the rated design pressure of the first containment.

5. The passive pressurized water reactor containment depressurization system according to claim 3, characterized in that, Check valves are installed on the pipeline between the first containment and the adjacent second containment and on the pipeline between the second containment and the third containment.

6. The passive pressurized water reactor containment depressurization system according to claim 3, characterized in that, The elevation of the second containment and / or the third containment is 5 to 15 meters lower than the height of the first containment.

7. The passive pressurized water reactor containment depressurization system according to claim 3, characterized in that, The waste heat removal device is also installed on the second containment and the third containment.

8. The passive pressurized water reactor containment depressurization system according to claim 2, characterized in that, The preset trigger threshold of the pressure relief device is 75% of the rated design pressure of the first containment.

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