Multi-stage pressure reducing device for high pressure input gas of nuclear power plant

Abstract

The application provides a multi-stage pressure reducing device for high-pressure input gas of a nuclear power plant, wherein at least two pressure reducing units are arranged in series, so that the high-pressure gas sequentially completes step-by-step pressure reduction through a gas discharge flow channel; and the gas downstream of a guide hole is guided into a rod cavity through an adjusting flow channel, so that the elastic member can be driven to elastically stretch and retract, and the piston can be driven to axially reciprocate along the guide hole, so that the flow cross section of the gas discharge flow channel at the guide hole can be dynamically adjusted, the high-pressure gas can be precisely reduced in pressure and stably output, the thermal impact and pressure impact of the high-temperature and high-pressure gas on the discharge container are greatly reduced, the problem that the traditional single-stage pressure reducing device cannot stably work due to a too large pressure difference is avoided, the discharge operation does not need to be frequently paused, and then the continuous discharge of the gas can be ensured.

Description

Technical Field

[0001] This invention relates to the field of gas pressure reduction technology, and more specifically to a multi-stage pressure reduction device for high-pressure input gas in nuclear power plants. Background Technology

[0002] During the operation of a nuclear power plant reactor coolant system, hydrogen needs to be injected into the system to maintain the reducing state of the coolant and prevent oxidation and corrosion of metal components. During this process, some hydrogen escapes from the coolant and accumulates in the pressurizer steam space. At the end of each fuel cycle, to eliminate safety risks, the mixture of steam and hydrogen must be discharged through the pressurizer steam space before reactor shutdown, completing the hydrogen removal process by venting the mixture into a venting container.

[0003] However, the mixed gas is characterized by high temperature, high pressure and radioactivity. When discharged into the low temperature and low pressure evacuation container, it will rapidly heat the medium inside the container, causing the pressure of the evacuation container to rise sharply. In order to prevent the container from overpressure, the discharge operation needs to be frequently stopped and resumed after the container pressure is restored. This cyclical operation makes the dehydrogenation process time-consuming, which seriously reduces the availability of nuclear power plant equipment and has a significant adverse impact on the economics of operation.

[0004] Existing high-pressure gas pressure reduction and circulation devices are limited by their single-stage pressure reduction structure design, making it difficult to adapt to the huge inlet and outlet pressure difference in the hydrogen removal operation of nuclear power plants, and thus unable to achieve efficient pressure reduction and stable output of high-pressure gas.

[0005] Based on this, the inventors of this application propose a multi-stage pressure reducing device for high-pressure input gas in nuclear power plants, in order to solve one or more of the aforementioned technical problems. Summary of the Invention

[0006] The present invention solves the above-mentioned technical problems through the following technical solution:

[0007] This invention provides a multi-stage pressure reducing device for high-pressure input gas in nuclear power plants, comprising:

[0008] At least two pressure reducing units are connected in series, and high-pressure gas flows through the pressure reducing units sequentially via a gas discharge channel;

[0009] Each of the aforementioned pressure-reducing units includes a housing having a receiving cavity, and the housing having a piston movable along the axial direction of the housing within the receiving cavity, the piston dividing the receiving cavity along its axial direction into a rod-type cavity and a rodless cavity;

[0010] The bottom of the accommodating cavity is provided with a guide hole that communicates with the gas discharge channel, and one end of the piston is inserted into the guide hole and is sealed to the wall of the guide hole.

[0011] The gas discharge channel branches downstream of the guide hole to form an adjustment channel. One end of the adjustment channel is connected to the gas discharge channel, and the other end penetrates the outer shell and extends into the rod cavity.

[0012] The outer shell is provided with an elastic element in the rod cavity. One end of the elastic element is connected to the top of the outer shell, and the other end abuts against the end of the piston away from the guide hole. The elastic element is driven by the gas pressure introduced into the rod cavity by the regulating channel, and can elastically extend and retract to press the piston to move back and forth axially along the guide hole, so as to dynamically adjust the flow cross section of the gas discharge channel at the guide hole.

[0013] According to one embodiment of the present invention, at least two of the pressure-reducing units are integrated into one housing, and the housing is provided with accommodating cavities corresponding to the number of the pressure-reducing units.

[0014] According to one embodiment of the present invention, each of the pressure-reducing units is provided with a corresponding housing.

[0015] According to one embodiment of the present invention, an emergency tributary is further included, which is arranged in parallel with the gas emission channel;

[0016] Along the flow direction of the gas emission channel, one end of the emergency tributary is connected to the inlet section of the upstream pressure reducing unit, and the other end is connected to the outlet section of the downstream pressure reducing unit.

[0017] According to one embodiment of the present invention, the emergency tributary is provided with an on / off switch, which is used to control the on / off state of the emergency tributary.

[0018] According to one embodiment of the present invention, the emergency tributary is provided with at least one branch channel, one end of the branch channel is connected to the emergency tributary, and the other end is connected to the gas emission channel in the pipe section located between adjacent pressure reducing units.

[0019] According to one embodiment of the present invention, along the gas flow direction of the gas discharge channel, the vertical distance from the guide hole of the downstream pressure reducing unit to the bottom surface of the housing is higher than the vertical distance from the guide hole of the upstream pressure reducing unit to the bottom surface of the housing.

[0020] According to one embodiment of the present invention, the elastic element is a spring, and the axis of the spring is collinear with the axis of the outer casing;

[0021] One end of the spring is fixedly connected to the piston, and the other end is fixedly connected to the top of the outer casing.

[0022] According to one embodiment of the present invention, a drive rod is provided on the top of the housing, the drive rod is threadedly engaged with the housing along the axial direction of the housing, one end of the drive rod extends into the rod cavity and is fixedly connected to the end of the elastic element away from the piston, and the drive rod is used to adjust the preload of the elastic element.

[0023] According to one embodiment of the present invention, the regulating channel is further provided with a flow control valve, which is used to adjust the gas flow rate through the regulating channel to the rod chamber.

[0024] The positive and progressive effects of this invention are as follows:

[0025] This invention relates to a multi-stage pressure reducing device for high-pressure input gas in nuclear power plants. By setting at least two pressure reducing units connected in series, the high-pressure gas undergoes a stepped pressure reduction through the gas discharge channel. By adjusting the flow channel, the gas downstream of the guide hole is introduced into the rod chamber, which drives the elastic element to elastically extend and retract, and drives the piston to reciprocate along the axial direction of the guide hole. This allows for dynamic adjustment of the flow cross-section of the gas discharge channel at the guide hole, achieving precise pressure reduction and stable output of the high-pressure gas. This significantly reduces the thermal and pressure shocks of high-temperature and high-pressure gas to the discharge container, avoiding the problem of unstable operation caused by excessive pressure difference in traditional single-stage pressure reducing devices. It eliminates the need for frequent interruptions to discharge operations, thus ensuring continuous gas discharge. Attached Figure Description

[0026] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0027] Figure 1 This is a schematic diagram of the multi-stage pressure reducing device for high-pressure input gas in a nuclear power plant under normal operating conditions.

[0028] Figure 2 This is a schematic diagram of the multi-stage pressure reducing device for high-pressure input gas in nuclear power plants according to the present invention in the condition of the pressure regulator exhaust.

[0029] Figure 3 This is a schematic diagram of the operation of the multi-stage pressure reducing device for high-pressure input gas in nuclear power plants under piston blockage conditions.

[0030] 1. Pressure reduction unit;

[0031] 2. Gas discharge channel; 21. Regulating channel; 22. Flow control valve;

[0032] 3. Outer shell; 31. Receiving cavity; 311. Rod cavity; 312. Rodless cavity; 313. Guide hole; 32. Piston; 33. Elastic element; 34. Drive rod;

[0033] 4. Emergency tributary; 41. Switch; 42. Branch channel. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0036] Currently, nuclear power plant reactor coolant systems face several technical challenges during hydrogen removal operations. These include the inability of existing single-stage pressure reduction devices to handle the large pressure differentials during the release of high-pressure, high-temperature, radioactive mixed gases; the lack of emergency backup leading to frequent shutdowns of evacuation containers due to overpressure; lengthy hydrogen removal times; and compromised operational economics.

[0037] Based on this, please refer to Figures 1 to 3 This application proposes a multi-stage pressure reducing device for high-pressure input gas in a nuclear power plant, comprising at least two pressure reducing units 1 connected in series. High-pressure gas flows sequentially through the pressure reducing units 1 via a gas discharge channel 2, and finally flows to a discharge container. Each pressure reducing unit 1 includes a housing 3, and the housing 3 has a receiving cavity 31. The housing 3 has a piston 32 that can move axially along the housing 3 within the receiving cavity 31. The piston 32 divides the receiving cavity 31 axially into a rod-type cavity 311 and a rodless cavity 312. A guide hole 313 communicating with the gas discharge channel 2 is opened at the bottom of the receiving cavity 31. One end of the piston 32 is inserted into the guide hole 313 and is tightly fitted against the wall of the guide hole 313. The gas discharge channel 2 branches downstream of the guide hole 313 to form an adjustment channel 21. One end of the adjustment channel 21 is connected to the gas discharge channel 2, and the other end passes through the outer shell 3 and extends into the rod cavity 311. The outer shell 3 is provided with an elastic element 33 in the rod cavity 311. One end of the elastic element 33 is connected to the top of the outer shell 3, and the other end abuts against the end of the piston 32 away from the guide hole 313. The elastic element 33 is driven by the gas pressure introduced into the rod cavity 311 by the adjustment channel 21, and can elastically extend and retract to press the piston 32 to move back and forth axially along the guide hole 313, so as to dynamically adjust the flow section of the gas discharge channel 2 at the guide hole 313.

[0038] The number of pressure relief units 1 can be two, three, or more. Figure 1 This explanation uses two pressure-reducing units as an example, but does not limit the specific number.

[0039] This application enables stepped pressure reduction of high-pressure gas by using at least two pressure reduction units 1 connected in series, thus avoiding the problem that single-stage pressure reduction cannot adapt to the huge pressure difference in nuclear power plants.

[0040] A regulating channel 21 is set on the gas emission channel 2. The gas introduced into the rod chamber 311 by the regulating channel 21 can drive the elastic element 33 to drive the piston 32 to dynamically adjust the flow section, thereby realizing the integration of pressure reduction and pressure stabilization. This effectively reduces the thermal and pressure shocks of high temperature and high pressure gas to the discharge container, avoids frequent shutdowns of the discharge operation, and ensures continuous gas discharge, shortens the hydrogen removal time of the nuclear power plant, and improves the economic efficiency and safety of nuclear power plant operation.

[0041] Furthermore, a flow control valve 22 is also provided on the regulating channel 21. The flow control valve 22 is used to adjust the gas flow rate that flows through the regulating channel 21 to the rod chamber 311.

[0042] By setting a flow control valve 22 on the regulating flow channel 21, the gas flow rate introduced into the rod chamber 311 can be precisely controlled, thereby controlling the moving speed and response sensitivity of the piston 32, avoiding excessive adjustment or overshoot of the piston 32 due to excessive gas flow, thus improving the stability of pressure reduction and stabilization.

[0043] Meanwhile, the response speed can be adjusted according to actual pressure reduction requirements to adapt to scenarios with different gas emission rates, enhancing the adaptability of the pressure reducing device. Furthermore, the flow control valve 22 can also cut off the regulating flow channel 21 in case of failure, facilitating maintenance and improving the operational safety of the pressure reducing device.

[0044] In one embodiment, each pressure-reducing unit 1 is provided with a corresponding housing 3. For example... Figure 1 As shown, adjacent pressure reducing units 1 are connected by gas discharge channels 2, but are not connected to each other.

[0045] By adopting a split structure with a single pressure-reducing unit 1 and an independent outer casing 3, the number of pressure-reducing units 1 can be flexibly increased or decreased according to the actual pressure-reducing needs of the nuclear power plant, adapting to gas handling scenarios of different pressure levels. Moreover, the independent disassembly and assembly design of each pressure-reducing unit 1 facilitates fault diagnosis and component replacement without requiring a complete shutdown, thereby reducing the impact of operation and maintenance on the nuclear power plant and improving the flexibility and reliability of the pressure-reducing device.

[0046] In some other embodiments, at least two pressure-reducing units 1 can be integrated into a housing 3, and the housing 3 is provided with a receiving cavity 31 corresponding to the number of pressure-reducing units 1.

[0047] That is, at least two accommodating cavities 31 are provided in a housing 3, and the piston 32 of the pressure reducing unit 1 is respectively placed in the matching accommodating cavity 31, thereby achieving step-by-step pressure reduction.

[0048] By integrating multiple pressure-reducing units 1 into a single housing 3 and achieving a compact layout through the built-in corresponding number of accommodating cavities 31, the overall space occupied by the pressure-reducing device can be significantly reduced, making it suitable for the compact installation environment of nuclear power plants. At the same time, the flow channel connection structure is simplified, which helps reduce assembly complexity and leakage risks, thereby improving the overall structural stability and ease of operation and maintenance of the pressure-reducing device.

[0049] Because the piston 32 and the guide hole 313 are in a movable fit, if they get stuck, it will affect the use of the gas discharge channel 2. Based on this, this application also provides an emergency branch 4, which is arranged in parallel with the gas discharge channel 2; along the flow direction of the gas discharge channel 2, one end of the emergency branch 4 is connected to the inlet section of the upstream pressure reducing unit 1, and the other end is connected to the outlet section of the downstream pressure reducing unit 1.

[0050] Specifically, the emergency branch 4 is connected in parallel with the gas discharge channel 2, thus forming a dual flow guarantee. When the normal channel cannot flow due to a fault such as piston 32 jamming, the gas can be continuously discharged through the emergency branch 4 to avoid interruption of the hydrogen removal operation.

[0051] Optionally, the diameter of the emergency branch 4 is smaller than that of the gas discharge channel 2, and the emergency branch 4 is connected across the upstream to the downstream side. This ensures that the basic pressure reduction and flow requirements of high-pressure gas can still be met in an emergency, further improving the continuity and safety of hydrogen removal operations in nuclear power plants.

[0052] Specifically, an on / off switch 41 is provided on the emergency tributary 4, which is used to control the on / off state of the emergency tributary 4.

[0053] In other words, the on / off switch 41 can achieve precise on / off control of the emergency tributary 4. Please refer to [link / reference needed] for details. Figure 1 Under normal operating conditions, the on / off switch 41 is in the closed position, thus preventing gas bypass and a decrease in pressure reduction and stabilization effect. In case of a fault, it can be quickly opened to activate the emergency passage, making operation convenient and efficient. For details, please refer to [link / reference needed]. Figure 3 .

[0054] Optionally, the on / off switch 41 can be a control valve, isolation valve, etc., which is not limited here.

[0055] Please continue to refer to Figure 1 and Figure 2At least one branch channel 42 is provided on the emergency tributary 4. One end of the branch channel 42 is connected to the emergency tributary 4, and the other end is connected to the gas discharge channel 2 located in the pipe section between adjacent pressure reducing units 1.

[0056] By setting up branch channels 42, when a certain stage pressure reducing unit 1 fails, the local emergency channel can be quickly opened through the corresponding branch channel 42 without activating the entire emergency branch 4, thus reducing the gas flow path length and pressure loss. At the same time, it can achieve precise bypassing of the failed unit, ensuring the normal operation of other pressure reducing units 1, and further improving the pertinence and efficiency of the pressure reducing device's emergency response.

[0057] In one embodiment, along the gas flow direction of the gas discharge channel 2, the vertical distance from the guide hole 313 of the downstream pressure reducing unit 1 to the bottom surface of the housing 3 is higher than the vertical distance from the guide hole 313 of the upstream pressure reducing unit 1 to the bottom surface of the housing 3.

[0058] The design of the downstream guide hole 313 being higher than the upstream guide hole 313 can adapt to the physical characteristics of the volume expansion of high-pressure gas after multi-stage pressure reduction, providing more sufficient flow space for the expanded gas and avoiding airflow congestion.

[0059] Meanwhile, the height difference creates a natural flow resistance gradient, buffering the gas flow rate. Combined with the dynamic adjustment of piston 32, this improves pressure stabilization accuracy. Furthermore, the height difference design reduces airflow interference between adjacent pressure-reducing units 1, ensuring independent and stable operation of each pressure-reducing unit 1, thereby optimizing the step-by-step pressure reduction effect.

[0060] Please continue to refer to Figure 1 and Figure 2 The elastic element 33 is a spring, and the axis of the spring is collinear with the axis of the outer shell 3; one end of the spring is fixedly connected to the piston 32, and the other end is fixedly connected to the top of the outer shell 3.

[0061] This application selects a spring as the elastic element 33 because of its simple and reliable structure, low cost, and suitability for the high temperature and high pressure conditions of nuclear power plants. By making the spring axis collinear with the axis of the outer casing 3, it can be ensured that the force is uniform when the spring extends and retracts, thereby avoiding sealing failure or adjustment jamming caused by piston 32 offset.

[0062] Furthermore, a drive rod 34 is provided on the top of the outer casing 3. The drive rod 34 is threadedly engaged with the outer casing 3 along the axial direction of the outer casing 3. One end of the drive rod 34 extends into the rod cavity 311 and is fixedly connected to the end of the elastic element 33 away from the piston 32. The drive rod 34 is used to adjust the preload of the elastic element 33.

[0063] The spring preload is adjusted by the threaded drive rod 34, which is easy to operate and has high adjustment accuracy. This allows for flexible setting of the outlet set pressure according to the different operating conditions of the nuclear power plant, and adapts to the handling of high-pressure gases of different pressure levels.

[0064] The following describes the operating status of the pressure reducing device during normal operation and gas emission at the nuclear power plant described in this application:

[0065] Please refer to Figure 1 When the nuclear power plant is operating normally and not venting gas, the elastic element 33 is in a contracted state, the piston 32 is in a non-throttling state, the gas emission path is in a normal passage state, and the on / off switch 41 is closed.

[0066] Please refer to Figure 2 When the pressurizer of the nuclear power plant discharges gas, the gas flows from the gas discharge channel 2 through the pressure reducing unit 1. After passing through the guide hole 313, some of the high-pressure gas enters the rod chamber 311 through the regulating channel 21, acting on the piston 32 and pushing it downward. This reduces the flow cross-section of the gas discharge channel 2 at the guide hole 313, thus throttling the gas. When the outlet pressure of the pressure reducing unit 1 reaches the set pressure, the force generated by the pressure difference acting on the piston 32 and the tensile force of the elastic element 33 are balanced, and the outlet pressure of the gas discharge channel 2 stabilizes. When the gas pressure decreases, the balance between the force generated by the pressure difference acting on the piston 32 and the tensile force of the elastic element 33 is disrupted. At this time, the tensile force of the elastic element 33 is greater than the force generated by the pressure difference on the piston 32, and the piston 32 moves upward under the pulling action of the elastic element 33. This automatically adjusts the flow cross-section of the gas discharge channel 2 at the piston 32.

[0067] Please refer to Figure 3 If, during the throttling process, a piston 32 gets stuck and blocks the guide hole 313, the on / off switch 41 can be opened to activate the emergency branch 4 for exhaust.

[0068] In summary, this application has at least the following advantages over traditional pressure-reducing devices:

[0069] By setting at least two pressure reducing units 1 connected in series to form a stepped pressure reducing structure, and with the sealing fit design of piston 32 and guide hole 313, leakage of high-pressure radioactive gas can be effectively avoided, which is suitable for the special operating conditions of nuclear power plants.

[0070] By using the regulating flow channel 21 to guide the gas downstream of the guide hole 313 into the rod chamber 311, the elastic element 33 drives the piston 32 to dynamically adjust the flow section, thereby achieving precise pressure reduction and stable output of high-pressure gas. This significantly reduces the thermal and pressure shocks of high-temperature and high-pressure gas to the discharge container, avoids the problem of traditional single-stage pressure reducing devices being unable to work stably due to excessive pressure difference, eliminates the need for frequent interruptions to discharge operations, and ensures continuous gas discharge.

[0071] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation", "connection", "joining", and "fixing" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can also refer to mechanical connections. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0072] This application uses specific terms to describe embodiments of the application. Terms such as "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of the application. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0073] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A multi-stage pressure reducing device for high-pressure input gas in a nuclear power plant, characterized in that, include: At least two pressure reducing units are connected in series, and high-pressure gas flows through the pressure reducing units sequentially via a gas discharge channel; Each of the aforementioned pressure-reducing units includes a housing having a receiving cavity, and a piston movable along the axial direction of the housing is provided within the receiving cavity, the piston dividing the receiving cavity along its axial direction into a rod-type cavity and a rodless cavity; The bottom of the accommodating cavity is provided with a guide hole that communicates with the gas discharge channel, and one end of the piston is inserted into the guide hole and is sealed to the wall of the guide hole. The gas discharge channel branches downstream of the guide hole to form an adjustment channel. One end of the adjustment channel is connected to the gas discharge channel, and the other end penetrates the outer shell and extends into the rod cavity. The outer casing is provided with an elastic element inside the rod cavity. One end of the elastic element is connected to the top of the outer casing, and the other end abuts against the end of the piston away from the guide hole. The elastic element is driven by the gas pressure introduced into the rod chamber by the regulating channel, and can elastically extend and retract to press the piston to reciprocate along the axial direction of the guide hole, so as to dynamically adjust the flow cross section of the gas discharge channel at the guide hole; Along the gas flow direction of the gas discharge channel, the vertical distance from the guide hole of the pressure reducing unit on the downstream side to the bottom surface of the housing is higher than the vertical distance from the guide hole of the pressure reducing unit on the upstream side to the bottom surface of the housing. The regulating channel is also equipped with a flow control valve, which is used to adjust the gas flow rate to the rod chamber through the regulating channel.

2. The multi-stage pressure reducing device for high-pressure input gas in nuclear power plants according to claim 1, characterized in that, At least two of the pressure-reducing units are integrated into one of the housings, and the housing is provided with accommodating cavities corresponding to the number of the pressure-reducing units.

3. The multi-stage pressure reducing device for high-pressure input gas in a nuclear power plant according to claim 1, characterized in that, Each of the aforementioned pressure-reducing units is provided with a corresponding housing.

4. The multi-stage pressure reducing device for high-pressure input gas in nuclear power plants according to claim 1, characterized in that, It also includes an emergency tributary, which is connected in parallel with the gas emission channel; Along the flow direction of the gas emission channel, one end of the emergency tributary is connected to the inlet section of the upstream pressure reducing unit, and the other end is connected to the outlet section of the downstream pressure reducing unit.

5. The multi-stage pressure reducing device for high-pressure input gas in a nuclear power plant according to claim 4, characterized in that, The emergency tributary is equipped with an on / off switch, which is used to control the on / off state of the emergency tributary.

6. The multi-stage pressure reducing device for high-pressure input gas in a nuclear power plant according to claim 5, characterized in that, The emergency tributary is provided with at least one branch channel, one end of which is connected to the emergency tributary and the other end is connected to the gas emission channel located in the pipe section between adjacent pressure reducing units.

7. The multi-stage pressure reducing device for high-pressure input gas in a nuclear power plant according to claim 1, characterized in that, The elastic element is a spring, and the axis of the spring is collinear with the axis of the outer shell; One end of the spring is fixedly connected to the piston, and the other end is fixedly connected to the top of the outer casing.

8. The multi-stage pressure reducing device for high-pressure input gas in a nuclear power plant according to claim 1, characterized in that, The top of the housing is provided with a drive rod, which is threaded to the housing along the axial direction of the housing. One end of the drive rod extends into the rod cavity and is fixedly connected to the end of the elastic element away from the piston. The drive rod is used to adjust the preload of the elastic element.

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