Hydraulic pressure relief valve assembly for primary circuit of nuclear power plant

Abstract

This invention provides a primary loop hydraulic pressure relief valve assembly for a nuclear power plant, comprising: a main valve and a three-position four-way control valve. The main valve includes: a main valve body and a valve core. The main valve body has a sealing cavity and a valve cavity. One end of the valve core is located in the sealing cavity, and the other end is located in the valve cavity. The valve core can slide within the main valve body under the pressure of the medium entering the sealing cavity to open or close the valve cavity. The pressure setpoint P of the medium opening the main valve is... 0main Satisfies: Atmospheric pressure < P 0main The Pacc three-position four-way control valve has its outlet connected to one of the first, second, and third inlets. Its outlet is connected to a sealed cavity. The first inlet is connected to the primary loop volume control box or pressure relief box, the second inlet is connected to the primary loop coolant, and the third inlet is connected to a constant pressure source. This invention enables automatic opening under primary loop conditions and maintains the valve in an always-open state. It also enables manual opening of the main valve and ensures effective isolation of the main valve during reactor shutdown and refueling.

Description

Technical Field

[0001] This invention relates to the field of nuclear power safety technology, specifically to a hydraulic pressure relief valve assembly for the primary loop of a nuclear power plant. Background Technology

[0002] In pressurized water reactor nuclear power plants, the reactor coolant system, as one of the most important barriers to contain radioactive materials, is directly related to the safety performance of the nuclear power plant.

[0003] Nuclear power plant reactor coolant systems operate at high pressures. To ensure that the system does not overpressure after an accident and that the reactor core is continuously cooled after an accident, overpressure protection valves and primary loop pressure relief valves need to be installed on the reactor coolant system.

[0004] The overpressure protection valves and pressure relief valves currently in use mainly include the following types:

[0005] (1) Spring-loaded safety valve: It automatically opens to relieve pressure when the system pressure reaches the set pressure of the safety valve. It is currently the most widely used overpressure protection valve in process systems. The characteristic of this type of safety valve is that it can only perform overpressure protection function. When the pressure is lower than the opening pressure, the valve closes and cannot be opened manually.

[0006] (2) Pilot-operated safety valve, similar to spring-loaded safety valve, automatically opens to relieve pressure when the system pressure reaches the set pressure of the safety valve. It has higher reliability than spring-loaded safety valve and is currently mainly used in pressure regulator safety valves. This type of safety valve requires less power to open. Its disadvantage is that it needs to be kept energized when it needs to be opened manually, and it cannot be kept open at low pressure.

[0007] (3) Electric or pneumatic isolation valves, which open or close via power supply when the system pressure reaches the design requirement. The advantage of this type of valve is that it can be opened at any time and maintains its original state after the power is lost. The disadvantage is that it requires a large amount of power to open.

[0008] (4) Explosive valve: The valve opening signal triggers the explosive unit inside the valve, generating high-pressure gas that drives the piston inside the valve. During the impact motion, the shear cover of the valve's flow path can be cut off, thereby connecting the valve inlet and outlet and realizing the safety function of system depressurization. The characteristic of this type of valve is that once opened, it always remains open and cannot be reversed. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a hydraulic pressure relief valve group for the primary loop of a nuclear power plant, which can realize the automatic opening of the main valve under the conditions of the primary loop and maintain it in the open state, and can also realize the manual opening of the main valve and ensure the effective isolation of the main valve during normal operation and reactor shutdown for refueling.

[0010] The technical solution adopted to solve the technical problem of this invention is:

[0011] This invention provides a primary loop hydraulic pressure relief valve assembly for a nuclear power plant, comprising: a main valve and a three-position four-way control valve.

[0012] The main valve includes a main valve body and a valve core. The main valve body has a sealing cavity and a valve cavity. The valve cavity is used to connect the primary coolant and the atmosphere. One end of the valve core is located in the sealing cavity, and the other end is located in the valve cavity. The valve core can slide within the main valve body under the pressure of the medium entering the sealing cavity to open or close the valve cavity.

[0013] The three-position four-way control valve has a first input port, a second input port, a third input port, and an output port. The output port is connected to the sealed cavity. The first input port is connected to an atmospheric pressure source. The second input port is connected to the primary coolant circuit. The third input port is connected to a constant pressure source.

[0014] The three-position four-way control valve has a first state where the output port is connected to the first input port and disconnected from both the second and third input ports; a second state where the output port is connected to the second input port and disconnected from both the first and third input ports; and a third state where the output port is connected to the third input port and disconnected from both the first and second input ports. It can switch between these three states to change the medium and pressure entering the sealed cavity. The pressure setpoint P of the medium entering the sealed cavity opens the main valve. 0main Satisfy: P0 < P 0main <Pacc, where P0 is atmospheric pressure and Pacc is the pressure of the constant pressure source.

[0015] Optionally, the three-position four-way control valve includes a control valve body, a control piston assembly, a first solenoid valve, and a second solenoid valve.

[0016] The control valve body has a main chamber, a first side chamber, and a second side chamber, which are located at opposite ends of the main chamber. A control piston assembly is located within the main chamber. A first solenoid valve is located within the first side chamber, and a second solenoid valve is located within the second side chamber.

[0017] The first input port, second input port, third input port, and output port are all located on the control valve body and communicate with the main chamber. The control piston assembly includes a control piston rod and multiple control pistons fixed to the control piston rod. The multiple control pistons are sequentially and slidably disposed within the main chamber along the axial direction of the control piston rod to divide the main chamber into multiple sub-chambers. Both ends of the control piston rod extend out of the main chamber, with one end connected to the first solenoid valve and the other end connected to the second solenoid valve.

[0018] The output port is located on one side of the control piston rod in the radial direction. The first input port, the second input port, and the third input port are all located on the other side of the control piston rod in the radial direction and are arranged sequentially along the axial direction of the piston rod. When the first solenoid valve is energized, it can drive the control piston assembly to move toward the second solenoid valve until the output port is connected to the third input port through one of its chambers, so that the three-position four-way control valve is in the third state. When the second solenoid valve is energized, it can drive the control piston assembly to move toward the first solenoid valve until the output port is connected to the first input port through one of its chambers, so that the three-position four-way control valve is in the first state. When both the first and second solenoid valves are de-energized, the control piston assembly can move axially until the output port is connected to the second input port through one of its chambers, so that the three-position four-way control valve is in the second state.

[0019] Optionally, the number of control pistons is five, and the five control pistons sequentially divide the main chamber into a first sub-chamber, a second sub-chamber, a third sub-chamber, a fourth sub-chamber, a fifth sub-chamber, and a sixth sub-chamber.

[0020] When the three-position four-way control valve is in the first state, the output port is connected to the first input port only through the third compartment.

[0021] When the three-position four-way control valve is in the third state, the output port is connected to the third input port only through the fourth sub-chamber.

[0022] When the three-position four-way control valve is in the second state, the output port is connected to the second input port only through the third chamber.

[0023] Optionally, the first solenoid valve includes a first suction cup, a first coil, and a first return spring; the second solenoid valve includes a second suction cup, a second coil, and a second return spring. The first coil and the second coil are respectively disposed on the outer end walls of the main chamber at both ends along the axial direction of the control piston rod. The first suction cup and the second suction cup are respectively disposed at both ends of the control piston rod. The first return spring is connected between the cavity wall of the first side chamber and the first suction cup, and the second return spring is connected between the cavity wall of the second side chamber and the second suction cup.

[0024] When the first solenoid valve is energized, the first suction cup moves toward the first coil until it is fixed thereto, thereby driving the control piston assembly to move toward the second solenoid valve until the three-position four-way control valve is in the third state. During the movement of the control piston assembly toward the second solenoid valve, the first return spring is stretched and the second return spring is compressed.

[0025] When the second solenoid valve is energized, the second suction cup moves toward the second coil until it is fixed thereto, thereby driving the control piston assembly to move toward the first solenoid valve until the three-position four-way control valve is in the first state. During the movement of the control piston assembly toward the first solenoid valve, the second return spring is stretched and the first return spring is compressed.

[0026] When both the first and second solenoid valves are de-energized, both the first and second reset springs are reset, thereby driving the control piston assembly to move axially to the second state of the three-position four-way control valve.

[0027] Optionally, multiple three-position four-way control valves are provided, and the multiple three-position four-way control valves are arranged in parallel.

[0028] Multiple first solenoid valves and multiple second solenoid valves are provided, with multiple first solenoid valves connected in series and multiple second solenoid valves also connected in series.

[0029] The valve core includes a main piston assembly and a main spring. The main piston assembly includes a main piston rod, a main piston, and a valve disc. The main piston rod is slidably disposed within the main valve body. The main piston is fixed on the main piston rod and located within the sealing cavity. The valve disc is fixed on the main piston rod and located within the valve cavity. The main spring is located within the sealing cavity and compressed between the main piston and the bottom wall of the valve cavity.

[0030] Optionally, the valve chamber is located in the lower part of the sealing chamber. The main valve body has a valve inlet and a valve outlet that communicate with the valve chamber respectively. The valve inlet is located at the bottom of the main valve body and is used to connect with the primary coolant circuit. The valve outlet is located on the side of the main valve body and is used to connect with the atmosphere. The main piston assembly is vertically slidable within the main valve body to open or close the valve inlet.

[0031] The pressure setpoint P of the medium entering the sealed cavity opens the main valve. 0main Also satisfies: P 0main ×(A1-A2)+G=F, where A1 is the cross-sectional area of ​​the main piston, A2 is the cross-sectional area of ​​the valve disc, G is the weight of the main piston assembly, and F is the elastic force of the main spring when the main valve is closed.

[0032] Optionally, the main spring passes through the main piston rod.

[0033] Optionally, the outer diameter of the valve disc gradually decreases from top to bottom, so that the outer wall of the valve disc forms a first conical surface.

[0034] The valve inlet is equipped with a nozzle, and the upper part of the inner wall of the nozzle has a second conical surface that mates with the first conical surface. When the main piston assembly moves down to mate with the first and second conical surfaces, the valve disc closes the valve inlet.

[0035] Optionally, the main valve body includes, from bottom to top, a valve housing, a valve seat, and a valve core that are sequentially fixed together, with the inner cavity of the valve housing forming the valve cavity.

[0036] The valve seat has a first groove on its top surface. The lower part of the valve core extends into the first groove and is sealed to the groove wall of the first groove. The bottom surface of the valve core has a second groove. The groove wall of the second groove and the bottom wall of the first groove enclose the sealing cavity.

[0037] Optionally, the main piston rod includes a working section and a positioning section. The lower end of the working section is fixedly connected to the valve disc, and its upper end passes through the valve seat and extends into the sealing cavity and is fixedly connected to the main piston. The main spring is sleeved on the working section.

[0038] The upper part of the valve core has a sealed exhaust cavity. A valve cover for opening or closing the exhaust cavity is provided at the top of the valve core. The lower end of the positioning section is fixedly connected to the piston, and its upper end passes through the valve core and extends into the exhaust cavity.

[0039] In the present invention, a three-position four-way control valve is combined with the main valve to form a hydraulic pressure relief valve group for the primary loop of a nuclear power plant. Among them, the main valve body of the main valve has a sealed cavity and a valve cavity. Its valve core slides in the main valve. The valve core can slide in the main valve body under the pressure of the medium entering the sealing cavity to open or close the valve cavity. The first input port of the three-position four-way control valve is connected to the atmospheric pressure (such as the volume control tank or the relief tank of the primary loop), its second input port is connected to the primary loop coolant, its third input port is connected to a constant pressure source, and its output port is connected to the sealing cavity of the main valve. The opening set value P of the main valve 0main satisfies: atmospheric pressure < P 0main < Pacc, thus:

[0040] When the pressure of the primary loop is normal (about 15.5 MPa), the three-position four-way control valve is switched to the second state (that is, its output port is connected to the second input port). At this time, the pressure in the sealing cavity of the main valve is the pressure of the primary loop, which is much greater than the opening set value P of the main valve 0main , and the main valve is closed, thereby achieving the isolation of the main valve during the normal operation of the primary loop and under high pressure (Prcs > P 0main ). When the primary loop fails and the pressure drop is less than the opening set value P of the main valve 0main , the main valve automatically opens, thereby achieving the automatic opening of the main valve when the pressure of the primary loop is abnormal;

[0041] When it is necessary to manually open the main valve under certain circumstances, the three-position four-way control valve is switched to the first state (that is, its output port is connected to the first input port). At this time, the pressure in the sealing cavity of the main valve is the atmospheric pressure, which is lower than the opening set value P of the main valve 0main , so the main valve opens;

[0042] When it is not desired for the main valve to open during reactor shutdown and refueling (when the pressure of the primary loop needs to be reduced to atmospheric pressure), the three-position four-way control valve is switched to the third state (that is, its output port is connected to the third input port). At this time, the pressure in the sealing cavity of the main valve is the pressure of the constant pressure source (such as the pressure of the accumulator tank is about 4 - 5 MPa), which is greater than the opening set value P of the main valve 0main , and the main valve is closed, thereby achieving the isolation of the main valve under low pressure conditions of the primary loop (Prcs < Pacc).

[0043] This pressure relief valve assembly design meets the primary circuit pressure relief requirements of subsequent Hualong models while possessing the following technical advantages:

[0044] 1) Manual opening is possible: The valve can be manually opened in any state simply by energizing the solenoid valve.

[0045] 2) Ensure effective isolation: Ensure effective valve isolation under different operating conditions of the power plant.

[0046] 3) Always maintains the open state: After the valve is opened, it can always maintain the open state without any power supply, ensuring long-term depressurization and long-term recirculation of the primary circuit. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the passive core cooling system;

[0048] Figure 2 This is a schematic diagram of the structure of the primary loop hydraulic pressure relief valve assembly for a nuclear power plant provided in Embodiment 1 of the present invention;

[0049] Figure 3 This is a schematic diagram of the main valve in the pressure relief valve assembly of Example 1.

[0050] In the diagram: 1. Three-position four-way control valve; 11. First side chamber; 12. Second side chamber; 13. First solenoid valve; 14. Second solenoid valve; 15. Main chamber; 16. Output port; 17. First input port; 18. Second input port; 19. Third input port; 110. Control valve body; 111. Control piston; 112. Control piston rod; 113. First coil; 114. First suction cup; 115. First return spring; 116. Second coil; 117. Second suction cup; 118. Second return spring; 2. Main valve; 21. Valve body; 22. Valve seat; 23. Valve core; 24. Valve chamber; 25. Piston; 26. Spring; 27. Working section; 28. Valve disc; 29. ​​Valve inlet; 210. Nozzle; 211. Valve outlet; 212. Exhaust chamber; 213. Positioning section; 214. Conduit; 215. Sealing chamber. Detailed Implementation

[0051] The technical solutions of the invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without creative effort are within the scope of the invention.

[0052] In the description of this invention, it should be noted that the use of terms such as "above" to indicate orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings and is only for the purpose of facilitating and simplifying the description. It does 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 this invention.

[0053] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0054] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection," "setting," "installation," "fixing," etc., 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 the above terms in this invention based on the specific circumstances.

[0055] This invention provides a primary loop hydraulic pressure relief valve assembly for a nuclear power plant, comprising: a main valve and a three-position four-way control valve.

[0056] The main valve includes a main valve body and a valve core. The main valve body has a sealing cavity and a valve cavity. The valve cavity is used to connect the primary coolant and the atmosphere. One end of the valve core is located in the sealing cavity, and the other end is located in the valve cavity. The valve core can slide within the main valve body under the pressure of the medium entering the sealing cavity to open or close the valve cavity.

[0057] The three-position four-way control valve has a first input port, a second input port, a third input port, and an output port. The output port is connected to the sealed cavity. The first input port is connected to an atmospheric pressure source. The second input port is connected to the primary coolant circuit. The third input port is connected to a constant pressure source.

[0058] The three-position four-way control valve has a first state where the output port is connected to the first input port and disconnected from both the second and third input ports; a second state where the output port is connected to the second input port and disconnected from both the first and third input ports; and a third state where the output port is connected to the third input port and disconnected from both the first and second input ports. It can switch between these three states to change the medium and pressure entering the sealed cavity. The pressure setpoint P of the medium entering the sealed cavity opens the main valve. 0main Satisfy: P0 < P 0main <Pacc, where P0 is atmospheric pressure and Pacc is the pressure of the constant pressure source.

[0059] Example 1:

[0060] like Figure 2 As shown, this embodiment provides a primary loop hydraulic pressure relief valve assembly for a nuclear power plant, including: a main valve 2 and a three-position four-way control valve 1.

[0061] The main valve 2 includes a main valve body and a valve core. The main valve body has a sealing cavity 215 and a valve cavity. The valve cavity is used to connect the primary coolant and the atmosphere. One end of the valve core is located in the sealing cavity 215, and the other end is located in the valve cavity 24. The valve core can slide within the main valve body under the pressure of the medium entering the sealing cavity 215 to open or close the valve cavity.

[0062] The three-position four-way control valve 1 has a first input port 17, a second input port 18, a third input port 19, and an output port 16. The output port 16 is connected to the sealing cavity 215, the first input port 17 is connected to an atmospheric pressure source, the second input port 18 is connected to the primary coolant circuit, and the third input port 19 is connected to a constant pressure source.

[0063] The three-position four-way control valve 1 has a first state where the output port 16 is connected to the first input port 17 and disconnected from the second input port 18 and the third input port 19; a second state where the output port 16 is connected to the second input port 18 and disconnected from the first input port 17 and the third input port 19; and a third state where the output port 16 is connected to the third input port 19 and disconnected from the first input port 17 and the second input port 18. It can switch between the first, second, and third states to change the medium and pressure entering the sealing cavity 215. The medium entering the sealing cavity 215 opens the pressure setpoint P of the main valve 2. 0main Satisfy: P0 < P 0main <Pacc, where P0 is atmospheric pressure and Pacc is the pressure of the constant pressure source.

[0064] Passive core cooling is one of the technical routes for third-generation pressurized water reactor nuclear power technology.

[0065] Taking AP1000 as an example, such as Figure 1 As shown, its passive core cooling system includes:

[0066] Core makeup water tank: The pressure is the same as that of the primary loop (15.5MPa), and it is responsible for the function of making the core makeup water under high pressure.

[0067] Water supply tank: around 4-5MPa, responsible for water replenishment when the pressure is below 4-5MPa.

[0068] IRWST (Gravity Water Tank): The pressure is the same as atmospheric pressure, as low as 0.1MPa, and it is responsible for replenishing water when the pressure of the primary circuit drops to normal pressure.

[0069] ADS valves (explosion valves): They perform the function of depressurization, gradually reducing the primary circuit pressure from 15.5 to atmospheric pressure, so that the above three water replenishment measures can be put into operation in sequence, and finally achieve IRWST gravity water injection, which can achieve long-term cooling of the reactor core and ensure long-term safety.

[0070] To avoid problems caused by excessively rapid depressurization, ADS1-3+ADS4 are put into operation in sequence.

[0071] Among them, ADS1-3 has a relatively low depressurization speed and mainly undertakes the function of depressurization under high pressure.

[0072] The ADS4 depressurizes quickly, so it can only be opened after the primary circuit pressure is below a certain threshold (approximately 8-9 MPa).

[0073] After ADS4 is activated, the primary circuit pressure can quickly drop to the pressure of the injection tank, and eventually drop to the IRWST injection pressure.

[0074] Current ADS technology primarily employs rupture valves and electric valves. Both types of valves open by outputting an electrical signal when the primary circuit pressure drops to a threshold. Electric valves, due to their large size and high energy requirement for opening, present numerous challenges in the design of pressure relief systems. Rupture valves offer advantages such as good sealing and low opening power, but certain issues remain regarding reliability data and intellectual property rights.

[0075] Subsequent models of the Hualong series adopt a passive safety system design concept, employing a passive safety system to address design baseline accidents. Under this design concept, a mature and reliable primary loop pressure relief system is required, capable of promptly and effectively reducing the primary loop pressure to the gravity injection pressure. Therefore, a new valve design solution is urgently needed to realize the primary loop pressure relief function and meet the application scenario requirements of subsequent Hualong models.

[0076] The pressure relief valve assembly of this invention is mainly used to replace the function of ADS-4, that is, when the primary circuit pressure drops to 8-9MPa, it can be manually opened, and the opening speed is required to be fast, without electricity or with little electricity (it can be powered by a battery to increase reliability after power loss).

[0077] This invention combines a three-position four-way control valve 1 with a main valve 2 to form a primary loop hydraulic pressure relief valve assembly for a nuclear power plant. The main valve 2 has a sealed cavity 215 and a valve chamber 24. Its valve core slides within the main valve 2, and can slide within the main valve body under the pressure of the medium entering the sealed cavity 215 to open or close the valve chamber 24. The first input port 17 of the three-position four-way control valve 1 is connected to atmospheric pressure (such as a primary loop volume control box or pressure relief box), its second input port 18 is connected to the primary loop coolant, its third input port 19 is connected to a constant pressure source, and its output port 16 is connected to the sealed cavity 215 of the main valve 2. The main valve 2 is set to open at a value P. 0main Satisfies: Atmospheric pressure < P 0main <Pacc, therefore:

[0078] When the primary circuit pressure is normal (approximately 15.5 MPa), the three-position four-way control valve 1 is switched to the second state (i.e., its output port 16 is connected to the second input port 18). At this time, the sealing chamber 215 of the main valve 2 is under primary circuit pressure, which is much greater than the main valve 2 opening set value P. 0main When main valve 2 is closed, it isolates the main valve 2 during normal operation of the primary circuit. In the event of a primary circuit fault, the pressure drop becomes less than the main valve 2 opening setpoint P. 0main When the pressure in the primary circuit is abnormal, the main valve 2 opens automatically, thus realizing the automatic opening of the main valve 2 when the pressure in the primary circuit is abnormal;

[0079] In the event of a primary circuit failure causing the pressure to drop to 8-9 MPa, requiring manual opening of the main valve 2, the three-position four-way control valve 1 is switched to the first state (i.e., its output port 16 is connected to the first input port 17). At this time, the pressure in the sealing chamber 215 of the main valve 2 is atmospheric pressure, which is lower than the opening set value P of the main valve 2. 0main This opens the main valve 2;

[0080] When it is undesirable for main valve 2 to open during a refueling shutdown (when the primary circuit pressure needs to be reduced to atmospheric pressure), the primary circuit pressure Prcs should be reduced to P... 0main When the pressure is between -Pacc, switch the three-position four-way control valve 1 to the third state (i.e., its output port 16 is connected to the third input port 19). At this time, the sealing chamber 215 of the main valve 2 is under constant pressure (such as the pressure of the safety injection tank, which is about 4-5 MPa), which is greater than the opening set value P of the main valve 2. 0main When main valve 2 is closed, isolation of main valve 2 is achieved under low pressure conditions in the primary circuit.

[0081] Furthermore, Table 1 shows a comparison of the advantages and disadvantages of the hydraulic pressure relief valve assembly of the present invention with several overpressure protection valves and pressure relief valves commonly used in the field of nuclear power safety mentioned in the background art.

[0082] Table 1

[0083]

[0084] In this embodiment, the three-position four-way control valve 1 includes a control valve body 110, a control piston assembly, a first solenoid valve 13, and a second solenoid valve 14.

[0085] The control valve body 110 has a main chamber 15, a first side chamber 11, and a second side chamber 12. The first side chamber 11 and the second side chamber 12 are respectively located at both ends of the main chamber 15. The control piston assembly is located in the main chamber 15. The first solenoid valve 13 is located in the first side chamber 11, and the second solenoid valve 14 is located in the second side chamber 12.

[0086] The first input port 17, the second input port 18, the third input port 19, and the output port 16 are all located on the control valve body 110 and are all connected to the main chamber 15. The control piston assembly includes a control piston rod 112 and multiple control pistons 111 fixed on the control piston rod 112. The multiple control pistons 111 are sequentially and slidably disposed within the main chamber 15 along the axial direction of the control piston rod 112 to divide the main chamber 15 into multiple sub-chambers. Both ends of the control piston rod 112 extend outside the main chamber 15, with one end connected to the first solenoid valve 13 and the other end connected to the second solenoid valve 14.

[0087] Output port 16 is located on one side of the control piston rod 112 in the radial direction. The first input port 17, the second input port 18, and the third input port 19 are all located on the other side of the control piston rod 112 in the radial direction and are arranged sequentially along the axial direction of the piston rod. When the first solenoid valve 13 is energized, it can drive the control piston assembly to move toward the second solenoid valve 14 until the output port 16 is connected to the third input port 19 through one of its chambers, so that the three-position four-way control valve 1 is in the third state. When the second solenoid valve 14 is energized, it can drive the control piston assembly to move toward the first solenoid valve 13 until the output port 16 is connected to the first input port 17 through one of its chambers, so that the three-position four-way control valve 1 is in the first state. When both the first solenoid valve 13 and the second solenoid valve 14 are de-energized, the control piston assembly can move axially until the output port 16 is connected to the second input port 18 through one of its chambers, so that the three-position four-way control valve 1 is in the second state.

[0088] In this embodiment, there are five control pistons 111. The five control pistons 111 divide the main chamber 15 into a first sub-chamber, a second sub-chamber, a third sub-chamber, a fourth sub-chamber, a fifth sub-chamber, and a sixth sub-chamber in sequence.

[0089] When the three-position four-way control valve 1 is in the first state, the output port 16 is connected to the first input port 17 only through the third sub-chamber. Furthermore, only the second input port 18 is located in the fourth sub-chamber, and only the third input port 19 is located in the fifth sub-chamber, thereby avoiding the axial force on the piston rod 112 caused by the pressure difference between the different input ports.

[0090] When the three-position four-way control valve 1 is in the third state, the output port 16 is connected to the third input port 19 only through the fourth sub-chamber. Furthermore, only the first input port 17 is located in the first sub-chamber, and only the second input port 18 is located in the fourth sub-chamber, thereby avoiding the axial force on the piston rod 112 caused by the pressure difference between the different input ports.

[0091] When the three-position four-way control valve 1 is in the second state, the output port 16 is connected to the second input port 18 only through the third sub-chamber. Furthermore, only the first input port 17 is located in the second sub-chamber, and only the third input port 19 is located in the fourth sub-chamber, thereby avoiding the axial force on the piston rod 112 caused by the pressure difference between different input ports.

[0092] In this embodiment, the first solenoid valve 13 includes a first suction cup 114, a first coil 113, and a first return spring 115. The second solenoid valve 14 includes a second suction cup 117, a second coil 116, and a second return spring 118. The first coil 113 and the second coil 116 are respectively disposed on the outer end walls of the main chamber 15 at both ends along the axial direction of the control piston rod 112. The first suction cup 114 and the second suction cup 117 are respectively disposed at both ends of the control piston rod 112. The first return spring 115 is connected between the cavity wall of the first side chamber 11 and the first suction cup 114. The second return spring 118 is connected between the cavity wall of the second side chamber 12 and the second suction cup 117.

[0093] When the first solenoid valve 13 is energized, the first suction cup 114 moves toward the first coil 113 until it is fixed thereto, thereby driving the control piston assembly to move toward the second solenoid valve 14 so that the three-position four-way control valve 1 is in the third state. During the movement of the control piston assembly toward the second solenoid valve 14, the first return spring 115 is stretched and the second return spring 118 is compressed.

[0094] When the second solenoid valve 14 is energized, the second suction cup 117 moves toward the second coil 116 until it is fixed thereto, thereby driving the control piston assembly to move toward the first solenoid valve 13 until the three-position four-way control valve 1 is in the first state. During the movement of the control piston assembly toward the first solenoid valve 13, the second return spring 118 is stretched and the first return spring 115 is compressed.

[0095] When both the first solenoid valve 13 and the second solenoid valve 14 are de-energized, the suction cups and coils of each solenoid valve are disconnected, and both the first return spring 115 and the second return spring 118 are reset, thereby driving the control piston assembly to move axially to the second state of the three-position four-way control valve 1.

[0096] In this embodiment, multiple three-position four-way control valves 1 are provided, and multiple three-position four-way control valves 1 are arranged in parallel.

[0097] In this embodiment, there are multiple first solenoid valves 13 and multiple second solenoid valves 14. Multiple first solenoid valves 13 are connected in series, and multiple second solenoid valves 14 are also connected in series.

[0098] In this embodiment, the valve core includes a main piston assembly and a main spring 26. The main piston assembly includes a main piston rod, a main piston 25, and a valve disc 28. The main piston rod is slidably disposed in the main valve body. The main piston 25 is fixed on the main piston rod and located in the sealing cavity 215. The valve disc 28 is fixed on the main piston rod and located in the valve cavity 24. The main spring 26 is located in the sealing cavity 215 and compressed between the main piston 25 and the bottom wall of the valve cavity 24.

[0099] In this invention, the main valve 2 serves as the primary flow path for fluid during primary circuit depressurization. The valve's interior is subjected to high-temperature, high-pressure fluid. To avoid the impact of high-temperature fluid and vibration on the valve control and drive system, this invention employs a drive piston and drive spring as the energy source for opening and closing the main valve 2. The main valve 2 is connected to a three-position four-way control valve 1 via a pilot line to control the pressure within the sealing cavity 215, further controlling the opening and closing of the main valve 2.

[0100] In this embodiment, the valve chamber 24 is located below the sealing chamber 215. The main valve body has a valve inlet 29 and a valve outlet 211 that communicate with the valve chamber. The valve inlet 29 is located at the bottom of the main valve body and is used to connect with the primary coolant. The valve outlet 211 is located on the side of the main valve body and is used to connect with the atmosphere. The main piston assembly is vertically slidable within the main valve body to open or close the valve inlet 29.

[0101] The medium entering the sealed cavity 215 opens the pressure set value P of the main valve 2. 0main Also satisfies: P 0main ×(A1-A2)+G=F, where A1 is the cross-sectional area of ​​the main piston 25, A2 is the cross-sectional area of ​​the valve disc 28, G is the weight of the main piston assembly, and F is the elastic force of the main spring when the main valve 2 is closed.

[0102] In the pressure relief valve assembly of the present invention, the opening, closing, and sealing of the main valve rely on the combined action of the drive spring, the pressure of the drive piston, and the system pressure, as detailed below:

[0103] The area of ​​the driving piston is larger than the area of ​​the valve disc. When the pressure of the sealing chamber × the area of ​​the driving piston + the weight of the piston assembly > the pressure of the driving spring + the pressure at the valve inlet × the area of ​​the valve disc, the valve is in the closed state and the valve is sealed by the pressure difference before and after the inequality.

[0104] When the pressure of the sealed chamber × the area of ​​the driving piston + the weight of the piston assembly < the pressure of the driving spring + the pressure at the valve inlet × the area of ​​the valve disc, the valve opens under the pressure of the driving spring and the internal pressure of the system, and the valve remains open by relying on the pressure of the driving spring.

[0105] like Figure 3 As shown, in this embodiment, the main spring 26 passes through the main piston rod and provides power for driving the piston to move up and down.

[0106] In this embodiment, the outer diameter of the valve disc 28 gradually decreases from top to bottom, so that the outer wall of the valve disc 28 forms a first conical surface.

[0107] A nozzle 210 is installed at the valve inlet 29. The upper part of the inner wall of the nozzle 210 has a second conical surface that mates with the first conical surface. When the main piston assembly moves down to mate with the first and second conical surfaces, the valve disc 28 closes the valve inlet 29.

[0108] The valve disc and nozzle have an inclined contact surface. When the valve is closed, the nozzle and valve disc can fit tightly under the action of pressure difference to better maintain the seal and prevent coolant leakage.

[0109] In this embodiment, the main valve body includes, from bottom to top, a valve housing 21, a valve seat 22, and a valve core 23, which are sequentially fixed together. The inner cavity of the valve housing 21 forms a valve cavity 24.

[0110] The top surface of the valve seat 22 has a first groove, the lower part of the valve core 23 extends into the first groove and is sealed to the groove wall of the first groove, and the bottom surface of the valve core 23 has a second groove, the groove wall of the second groove and the bottom wall of the first groove enclose to form a sealing cavity 215.

[0111] In this embodiment, a conduit 214 is fixed inside the valve core 23. One end of the conduit 214 extends into the sealing cavity 215, and the other end extends out of the valve core 23 and is connected to the output port 16 of the three-position four-way control valve 1.

[0112] In this embodiment, the main piston rod includes a working section 27 and a positioning section 213. The lower end of the working section 27 is fixedly connected to the valve disc 28, and its upper end passes through the valve seat 22 and extends into the sealing cavity 215 and is fixedly connected to the main piston 25. The main spring 26 passes through the working section 27.

[0113] The upper part of the valve core 23 has a sealed exhaust chamber 212, and the top of the valve core 23 is provided with a valve cover 216 that opens or closes the exhaust chamber 212. The lower end of the positioning section 213 is fixed to the piston, and its upper end passes through the valve core 23 and extends into the exhaust chamber 212.

[0114] The hydraulic pressure relief valve assembly of the present invention is used to achieve rapid pressure relief in a primary circuit, and its functions are as follows:

[0115] By controlling the first solenoid valve 13 and the second solenoid valve 14, the output pressure of the three-position four-way control valve 1 is controlled, thereby realizing the opening and closing control of the main valve 2.

[0116] Assume that the pressure of the primary loop is Prcs. Under the normal operating condition of the nuclear power plant, Prcs = 15.5 MPa. Under the condition of normal shutdown and refueling overhaul of the nuclear power plant, it can be gradually reduced to 0.1 MPa. The pressure of the constant pressure source accumulator tank is Pacc, and the normal pressure is about 4 - 5 MPa. The pressure of the pressure relief tank or the volume control tank is P0, and the normal pressure is 0.1 MPa.

[0117] When the first solenoid valve 13 and the second solenoid valve 14 are energized and de-energized respectively, the piston pressure of the main valve 2 and the functions achieved by the main valve 2 are shown in Table 2 below.

[0118] Table 2

[0119]

[0120] Function description of the main valve 2:

[0121] Automatic opening: When both the first solenoid valve 13 and the second solenoid valve 14 are de-energized, when the pressure of the accident primary loop drops from 15.5 MPa to a pressure lower than the opening pressure of the main valve 2, the main valve 2 automatically opens.

[0122] Manual opening: In some cases of the nuclear power plant, the operator needs to manually open the pressure relief valve. At this time, the first solenoid valve 13 is de-energized and the second solenoid valve 14 is energized, resulting in the piston pressure of the main valve 2 = P0. At this time, the main valve 2 opens under the action of the driving spring and the pressure of the primary loop and can always maintain the open state.

[0123] Isolation under high pressure: During the normal operation of the nuclear power plant, the pressure of the primary loop is 15.5 MPa. During the shutdown and refueling process, the pressure of the primary loop gradually drops from 15.5 MPa to P 0main until it drops to atmospheric pressure. During the normal operation and shutdown and refueling process, when the pressure of the primary loop Prcs > P 0main , it is not desired for the main valve 1 to open, so the pressure relief valve needs to be isolated. At this time, both the first solenoid valve 13 and the second solenoid valve 14 are de-energized, resulting in the piston pressure of the main valve = Prcs. Since the piston area of the main valve is larger than the valve disc area, when Prcs is greater than a certain pressure (P 0main , which is related to the piston area of the main valve and the driving force of the driving spring), the main valve still remains in the closed state.

[0124] Isolation under low pressure: When the pressure of the primary loop Prcs < Pacc and further drops to P0main, it is necessary to switch to the low-pressure isolation state. At this time, the first solenoid valve is energized, and the piston pressure of the main valve = Pacc. Since Pacc is always constant at 4 - 5 MPa, it can ensure that the main valve is always in the closed state.

[0125] This pressure relief valve group design not only meets the pressure relief requirements of the primary loop of the subsequent models of Hualong, but also has the following technical advantages:

[0126] 1) Manual opening is possible: The valve can be manually opened in any state simply by energizing the solenoid valve.

[0127] 2) Ensure effective isolation: Ensure effective valve isolation under different operating conditions of the power plant.

[0128] 3) Always maintains the open state: After the valve is opened, it can always maintain the open state without any power supply, ensuring long-term depressurization and long-term recirculation of the primary circuit.

[0129] 4) High reliability: By combining solenoid valves in parallel and series, the single fault principle of the system is met, providing a redundant means for valve opening and closing. This ensures that the valve can be reliably opened and closed under any condition, with a low probability of false triggering.

[0130] 5) Low leakage rate. During normal operation, the main valve piston is sealed by the pressure applied by the primary circuit itself.

[0131] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A primary loop hydraulic pressure relief valve assembly for a nuclear power plant, characterized in that, include: Main valve (2) and three-position four-way control valve (1). The main valve (2) includes a main valve body and a valve core. The main valve body has a sealing cavity (215) and a valve cavity. The valve cavity is used to connect the primary coolant and the atmosphere. One end of the valve core is located in the sealing cavity (215), and the other end is located in the valve cavity (24). The valve core can slide within the main valve body under the pressure of the medium entering the sealing cavity (215) to open or close the valve cavity. The three-position four-way control valve (1) has a first input port (17), a second input port (18), a third input port (19), and an output port (16). The output port (16) is connected to the sealed cavity (215), the first input port (17) is connected to an atmospheric pressure source, the second input port (18) is connected to the primary coolant, and the third input port (19) is connected to a constant pressure source. The three-position four-way control valve (1) has a first state in which the output port (16) is connected to the first input port (17) and disconnected from the second input port (18) and the third input port (19). It also has a second state in which the output port (16) is connected to the second input port (18) and disconnected from the first input port (17) and the third input port (19). Finally, it has a third state in which the output port (16) is connected to the third input port (19) and disconnected from the first input port (17) and the second input port (18). It can switch between the first state, the second state and the third state to change the medium and pressure entering the sealing cavity (215). The medium entering the sealing cavity (215) opens the pressure setting value P of the main valve (2). 0main Satisfy: P0 < P 0main <Pacc, where P0 is atmospheric pressure and Pacc is the pressure of the constant pressure source.

2. The primary loop hydraulic pressure relief valve assembly for nuclear power plants according to claim 1, characterized in that, The three-position four-way control valve (1) includes a control valve body (110), a control piston assembly, a first solenoid valve (13), and a second solenoid valve (14). The control valve body (110) has a main chamber (15), a first side chamber (11), and a second side chamber (12). The first side chamber (11) and the second side chamber (12) are located at opposite ends of the main chamber (15). The control piston assembly is located in the main chamber (15). The first solenoid valve (13) is located in the first side chamber (11), and the second solenoid valve (14) is located in the second side chamber (12). The first input port (17), the second input port (18), the third input port (19), and the output port (16) are all located on the control valve body (110) and are all connected to the main chamber (15). The control piston assembly includes a control piston rod (112) and multiple control pistons (111) fixed on the control piston rod (112). The multiple control pistons (111) are sequentially and sealed within the main chamber (15) along the axial direction of the control piston rod (112) to divide the main chamber (15) into multiple sub-chambers. Both ends of the control piston rod (112) extend outside the main chamber (15), with one end connected to the first solenoid valve (13) and the other end connected to the second solenoid valve (14). The output port (16) is located on one side of the control piston rod (112) in the radial direction. The first input port (17), the second input port (18), and the third input port (19) are all located on the other side of the control piston rod (112) in the radial direction and are arranged sequentially along the axial direction of the piston rod. When the first solenoid valve (13) is energized, it can drive the control piston assembly to move toward the second solenoid valve (14) to the output port (16). The output port (16) is connected to the third input port (19) through one of the chambers, so that the three-position four-way control valve (1) is in the third position. In the first state, when the second solenoid valve (14) is energized, it can drive the control piston assembly to move toward the first solenoid valve (13) to the output port (16) and communicate with the first input port (17) through one of its chambers, so that the three-position four-way control valve (1) is in the first state. When both the first solenoid valve (13) and the second solenoid valve (14) are de-energized, the control piston assembly can move axially to the output port (16) and communicate with the second input port (18) through one of its chambers, so that the three-position four-way control valve (1) is in the second state.

3. The primary loop hydraulic pressure relief valve assembly for nuclear power plants according to claim 2, characterized in that, The number of control pistons (111) is five, and the five control pistons (111) divide the main chamber (15) into a first sub-chamber, a second sub-chamber, a third sub-chamber, a fourth sub-chamber, a fifth sub-chamber, and a sixth sub-chamber in sequence. When the three-position four-way control valve (1) is in the first state, the output port (16) is connected only to the first input port (17) through the third compartment. When the three-position four-way control valve (1) is in the third state, the output port (16) is connected only to the third input port (19) through the fourth sub-chamber. When the three-position four-way control valve (1) is in the second state, the output port (16) is connected to the second input port (18) only through the third sub-chamber.

4. The primary loop hydraulic pressure relief valve assembly for nuclear power plants according to claim 2, characterized in that, The first solenoid valve (13) includes a first suction cup (114), a first coil (113), and a first return spring (115). The second solenoid valve (14) includes a second suction cup (117), a second coil (116), and a second return spring (118). The first coil (113) and the second coil (116) are respectively disposed on the outer end walls of the main chamber (15) along the axial direction of the control piston rod (112). The first suction cup (114) and the second suction cup (117) are respectively disposed at both ends of the control piston rod (112). The first return spring (115) is connected between the cavity wall of the first side chamber (11) and the first suction cup (114). The second return spring (118) is connected between the cavity wall of the second side chamber (12) and the second suction cup (117). When the first solenoid valve (13) is energized, the first suction cup (114) moves toward the first coil (113) until it is fixed to it, so as to drive the control piston assembly to move toward the second solenoid valve (14) to the third position of the three-position four-way control valve (1). During the movement of the control piston assembly toward the second solenoid valve (14), the first return spring (115) is stretched and the second return spring (118) is compressed. When the second solenoid valve (14) is energized, the second suction cup (117) moves toward the second coil (116) until it is fixed thereto, thereby driving the control piston assembly to move toward the first solenoid valve (13) to the three-position four-way control valve (1) in the first state. During the movement of the control piston assembly toward the first solenoid valve (13), the second return spring (118) is stretched and the first return spring (115) is compressed. When both the first solenoid valve (13) and the second solenoid valve (14) are de-energized, both the first reset spring (115) and the second reset spring (118) are reset to drive the control piston assembly to move axially to the second state of the three-position four-way control valve (1).

5. The primary loop hydraulic pressure relief valve assembly for nuclear power plants according to claim 1, characterized in that, The three-position four-way control valve (1) is provided in multiple units, and the multiple three-position four-way control valves (1) are arranged in parallel.

6. The primary loop hydraulic pressure relief valve assembly for nuclear power plants according to any one of claims 2-5, characterized in that, Multiple first solenoid valves (13) and multiple second solenoid valves (14) are provided. Multiple first solenoid valves (13) are connected in series, and multiple second solenoid valves (14) are also connected in series.

7. The primary loop hydraulic pressure relief valve assembly for nuclear power plants according to any one of claims 1-5, characterized in that, The valve core includes a main piston assembly and a main spring (26). The main piston assembly includes a main piston rod, a main piston (25), and a valve disc (28). The main piston rod is slidably disposed in the main valve body. The main piston (25) is fixed on the main piston rod and located in the sealing cavity (215). The valve disc (28) is fixed on the main piston rod and located in the valve cavity (24). The main spring (26) is located in the sealing cavity (215) and compressed between the main piston (25) and the bottom wall of the valve cavity (24).

8. The primary loop hydraulic pressure relief valve assembly for nuclear power plants according to claim 7, characterized in that, The valve chamber (24) is located at the lower part of the sealing chamber (215). The main valve body is provided with a valve inlet (29) and a valve outlet (211) that are respectively connected to the valve chamber. The valve inlet (29) is located at the bottom of the main valve body and is used to connect with the primary coolant. The valve outlet (211) is located on the side of the main valve body and is used to connect with the atmosphere. The main piston assembly is vertically slidable in the main valve body to open or close the valve inlet (29). The medium entering the sealed cavity (215) opens the pressure set value P of the main valve (2). 0main Also satisfies: P 0main ×(A1-A2)+G=F, where A1 is the cross-sectional area of ​​the main piston (25), A2 is the cross-sectional area of ​​the valve disc (28), G is the weight of the main piston assembly, and F is the elastic force of the main spring when the main valve (2) is closed.

9. The primary loop hydraulic pressure relief valve assembly for nuclear power plants according to claim 7, characterized in that, The main spring (26) is mounted on the main piston rod.

10. The primary loop hydraulic pressure relief valve assembly for nuclear power plants according to claim 8, characterized in that, The outer diameter of the valve disc (28) gradually decreases from top to bottom, so that the outer wall of the valve disc (28) forms a first conical surface. The valve inlet (29) is equipped with a nozzle (210), and the upper part of the inner wall of the nozzle (210) has a second conical surface that mates with the first conical surface. When the main piston assembly moves down to mate with the first and second conical surfaces, the valve disc (28) closes the valve inlet (29).

11. The primary loop hydraulic pressure relief valve assembly for nuclear power plants according to claim 7, characterized in that, The main valve body comprises, from bottom to top, a valve housing (21), a valve seat (22), and a valve core (23) that are fixedly connected in sequence, and the inner cavity of the valve housing (21) forms the valve cavity (24). The valve seat (22) has a first groove on its top surface. The lower part of the valve core (23) extends into the first groove and is sealed to the groove wall of the first groove. The bottom surface of the valve core (23) has a second groove. The groove wall of the second groove and the bottom wall of the first groove enclose the sealing cavity (215).

12. The primary loop hydraulic pressure relief valve assembly for nuclear power plants according to claim 11, characterized in that, The main piston rod includes a working section (27) and a positioning section (213). The lower end of the working section (27) is fixedly connected to the valve disc (28), and its upper end passes through the valve seat (22) and extends into the sealing cavity (215) and is fixedly connected to the main piston (25). The main spring (26) passes through the working section (27). The upper part of the valve core (23) has a sealed exhaust chamber (212), and the top of the valve core (23) is provided with a valve cover (216) for opening or sealing the exhaust chamber (212). The lower end of the positioning section (213) is fixed to the piston, and its upper end passes through the valve core (23) and extends into the exhaust chamber (212).

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