Isolation valve for passive water injection line of nuclear power plant

Abstract

The application provides an isolation valve for a passive water injection pipeline of a nuclear power plant, comprising a main valve and a two-position three-way control valve, the main valve comprising a main valve body and a valve core, the main valve body having a sealing cavity and a valve cavity, the valve cavity being used for connecting the water injection pipeline and a coolant system, the valve core being located in the sealing cavity at one end and in the valve cavity at the other end, and being capable of sliding in the main valve body under the pressure of a medium in the sealing cavity to open or close the valve cavity, the pressure value P of the medium opening the main valve being set 0main to satisfy: Pgmax < P < Pacc 0main The outlet of the two-position three-way control valve can be communicated with one of a first inlet and a second inlet, the output port is communicated with the sealing cavity, the first inlet is communicated with a primary coolant, and the second inlet is communicated with a constant pressure source. The application can realize automatic opening when the pressure of the primary loop satisfies the condition, maintain the opening state all the time, ensure effective isolation of the main valve during shutdown and refueling, and realize manual recovery of the isolation function after the valve is opened.

Description

Technical Field

[0001] This invention relates to the field of nuclear power safety technology, specifically to an isolation valve for passive water injection pipelines in nuclear power plants. Background Technology

[0002] Passive safety systems are a design feature of some third-generation nuclear power plants, and passive water injection is one of the main passive safety systems.

[0003] Passive water injection typically uses compressed gas or gravity to inject cooling water into the reactor coolant system, ensuring the safety of the reactor core after an accident.

[0004] Passive water injection systems are isolated during normal operation of a nuclear power plant, thus requiring highly reliable isolation valves. These valves are typically either electric valves or rupture valves. Electric valves can open at any time and remain open even after power loss; however, they require significant power to open. Rupture valves, on the other hand, are activated by a signal triggering an internal rupture unit. This generates high-pressure gas that drives a piston within the valve. The impact action cuts off the shear sash in the valve's flow path, opening the valve's inlet and outlet. A key characteristic of this type of valve is that once opened, it remains open and cannot be reversed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing an isolation valve for a passive water injection pipeline in a nuclear power plant, which can automatically open when the primary loop pressure meets the conditions and maintain the open state at all times, and can ensure effective isolation during normal operation and reactor shutdown for refueling, as well as manually restore the isolation function after the valve is opened.

[0006] The technical solution adopted to solve the technical problem of this invention is:

[0007] This invention provides an isolation valve for passive water injection pipelines in nuclear power plants, comprising: a main valve and a two-position three-way control valve.

[0008] 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 a passive water injection line and a primary coolant system. 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.

[0009] The two-position three-way control valve has a first input port, a second input port, and an output port. The output port is connected to the sealed cavity, the first input port is connected to the primary coolant circuit, and the second input port is connected to a constant pressure source.

[0010] The two-position three-way control valve has a first state where the output port is connected to the first input port and disconnected from the second input port, and a second state where the output port is connected to the second input port and disconnected from the first input port. It can switch between the first and second 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: Pgmax < P 0main <Pacc, where Pgmax is the maximum pressure of the passive water injection pipeline and Pacc is the pressure of the constant pressure source.

[0011] Optionally, the two-position three-way control valve includes a control valve body, a control piston assembly, a first solenoid valve, and a second solenoid valve.

[0012] 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.

[0013] The first input port, the second input port, and the 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.

[0014] The output port is located on one side of the control piston rod in the radial direction, and the first input port and the second input port are both located on the other side of the control piston rod in the radial direction. 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 second input port through one of its chambers, so that the two-position three-way control valve is in the second state. When the second solenoid valve is energized, the control piston assembly can 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 two-position three-way control valve is in the first state.

[0015] Optionally, the number of control pistons is four, and the four control pistons sequentially divide the main chamber into a first sub-chamber, a second sub-chamber, a third sub-chamber, a fourth sub-chamber, and a fifth sub-chamber.

[0016] When the two-position three-way control valve is in the first state, the output port is connected to the first input port only through the third branch chamber.

[0017] When the two-position three-way control valve is in the second state, the output port is connected to the second input port only through the third chamber.

[0018] Optionally, the first solenoid valve includes a first suction cup and a first coil, and the second solenoid valve includes a second suction cup and a second coil. 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, and the first suction cup and the second suction cup are respectively disposed at both ends of the control piston rod.

[0019] When the first solenoid valve is energized, the first suction cup moves toward the first coil until it is fixed to it, so as to drive the control piston assembly to move toward the second solenoid valve until the two-position three-way control valve is in the second state. When the second solenoid valve is energized, the second suction cup moves toward the second coil until it is fixed to it, so as to drive the control piston assembly to move toward the first solenoid valve until the two-position three-way control valve is in the first state.

[0020] Optionally, multiple two-position three-way control valves are provided, and the multiple two-position three-way control valves are arranged in parallel.

[0021] Optionally, 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.

[0022] Optionally, 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.

[0023] 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 respectively communicating with the valve chamber. The valve inlet is located at the bottom of the main valve body for connecting to the primary coolant system, and the valve outlet is located on the side of the main valve body for connecting to the gravity water injection pipeline. The main piston assembly is vertically slidable within the main valve body to open or close the valve inlet.

[0024] The pressure setpoint P of the medium entering the sealed cavity opens the main valve. 0main Also satisfies: P 0main ×A1-(P 0main -Pgmax)×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, F is the elastic force of the main spring when the main valve is closed, and Pgmax is the maximum pressure of the gravity water injection pipeline.

[0025] Optionally, the main spring passes through the main piston rod.

[0026] 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.

[0027] Optionally, 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.

[0028] 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.

[0029] Optionally, the top surface of the valve seat has a first groove, the lower part of the valve core extends into the first groove and is sealed to the groove wall of the first groove, and 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.

[0030] 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, extends into the sealing cavity, and is fixedly connected to the main piston. The main spring passes through the working section.

[0031] The upper part of the valve core has a sealed exhaust chamber, and the top of the valve core is provided with a valve cover that opens or closes the exhaust chamber. The lower end of the positioning section is fixed to the piston, and its upper end passes through the valve core and extends into the exhaust chamber.

[0032] This invention combines a two-position three-way control valve with a main valve to form an isolation valve for passive water injection pipelines in nuclear power plants. The main valve body has a sealed cavity and a valve cavity, with a valve core slidably disposed within the main valve. The valve core can slide within the main valve body under the pressure of the medium entering the sealed cavity to open or close the valve cavity. The first input port of the two-position three-way control valve is connected to the primary coolant circuit, its second input port is connected to a constant pressure source, and its output port is connected to the sealed cavity of the main valve. The main valve opening setpoint P... 0main Satisfy: Pgmax

[0033] <P 0main <Pacc, therefore:

[0034] When the primary circuit pressure is normal (approximately 15.5 MPa), the two-position three-way control valve is switched to the first state (i.e., its output port is connected to the first input port). At this time, the sealing chamber of the main valve is under the primary circuit pressure, which is much greater than the main valve opening set value P. 0main The main valve closes, thus isolating the main valve during normal operation of the primary circuit. In the event of a primary circuit fault, the pressure drop becomes less than the main valve opening setpoint P. 0main When the main valve opens automatically, gravity water injection function is realized;

[0035] During refueling after shutdown (primary circuit pressure Prcs is located at P...) 0main-Pacc (and will further decrease to atmospheric pressure) When you do not want the main valve to open, switch the two-position three-way control valve to the second state (i.e., its output port is connected to the second input port). At this time, the sealing chamber of the main valve is under constant pressure (such as the pressure of the safety injection tank, which is about 4-5 MPa), which is greater than the main valve opening set value P. 0main The main valve is closed, thus isolating the main valve under low pressure conditions in the primary circuit.

[0036] This isolation valve, while fulfilling the function of gravity water injection in nuclear power plants, possesses the following technical advantages:

[0037] 1) When the valve is in standby mode, it can automatically open without any external energy input when the primary circuit pressure reaches the opening condition.

[0038] 2) Ensure effective isolation: Ensure effective valve isolation under different operating conditions of the power plant.

[0039] 3) Once the valve is opened, it can remain in the open state without requiring any power supply to maintain the open state.

[0040] 4) After the valve is opened, the isolation function can be restored by switching the control valve state. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of an isolation valve for a passive water injection pipeline in a nuclear power plant, provided in Embodiment 1 of the present invention.

[0042] In the diagram: 1. Two-position three-way control valve; 11. Control valve body; 12. Main chamber; 13. First side chamber; 14. Second side chamber; 15. Control piston rod; 16. Control piston;

[0043] 17. First suction cup; 18. First coil; 19. Second suction cup; 110. Second coil;

[0044] 111. Output port; 112. First input port; 113. Second input port; 2. Main valve;

[0045] 21. Valve body; 22. Valve seat; 23. Valve core; 24. Valve cavity; 25. Piston; 26. Spring; 27. Working section; 28. Valve disc; 29. ​​Valve inlet; 210. Nozzle; 211. Valve outlet; 212. Exhaust cavity; 213. Positioning section; 214. Guide tube; 215. Sealing cavity. Detailed Implementation

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] This invention provides an isolation valve for passive water injection pipelines in nuclear power plants, comprising: a main valve and a two-position three-way control valve.

[0051] 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 a passive water injection line and a primary coolant system. 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.

[0052] The two-position three-way control valve has a first input port, a second input port, and an output port. The output port is connected to the sealed cavity, the first input port is connected to the primary coolant circuit, and the second input port is connected to a constant pressure source.

[0053] The two-position three-way control valve has a first state where the output port is connected to the first input port and disconnected from the second input port, and a second state where the output port is connected to the second input port and disconnected from the first input port. It can switch between the first and second 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: Pgmax < P 0main<Pacc, where Pgmax is the maximum pressure of the passive water injection pipeline and Pacc is the pressure of the constant pressure source.

[0054] Example 1:

[0055] like Figure 1 As shown, this embodiment provides an isolation valve for a passive water injection pipeline in a nuclear power plant, including: a main valve 2 and a two-position three-way control valve 1.

[0056] 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 passive water injection line and the primary coolant system. 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.

[0057] The two-position three-way control valve 1 has a first input port 112, a second input port 113, and an output port 111. The output port 111 is connected to the sealing cavity 215. The first input port 112 is connected to an atmospheric pressure source. The second input port 113 is connected to the primary circuit coolant and a constant pressure source.

[0058] The two-position three-way control valve 1 has a first state in which the output port 111 is connected to the first input port 112 and disconnected from the second input port 113, and also has a second state in which the output port 111 is connected to the second input port 113 and disconnected from the first input port 112. It can switch between the first state and the second state to change the medium and pressure entering the sealing chamber 215. The medium entering the sealing chamber 215 opens the pressure set value P of the main valve 2. 0main Satisfy: Pgmax < P 0main <Pacc, where Pgmax is the highest pressure of the passive water injection pipeline (Pgmax is approximately 0.2-0.3 MPa), and Pacc is the pressure of the constant pressure source.

[0059] This invention combines a two-position three-way control valve 1 with a main valve 2 to form an isolation valve for passive water injection pipelines in nuclear power plants. The main valve 2 has a sealed cavity 215 and a valve chamber 24. Its valve core is slidably disposed within the main valve 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. The first input port 112 of the two-position three-way control valve 1 is connected to the primary coolant circuit, its second input port 113 is connected to a constant pressure source, and its output port 111 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 Satisfy: Pgmax < P 0main <Pacc, therefore:

[0060] When the primary circuit pressure is normal (approximately 15.5 MPa), the two-position three-way control valve 1 is switched to the first state (i.e., its output port 111 is connected to the first input port 112). 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 this happens, main valve 2 opens automatically, thus enabling gravity water injection.

[0061] During refueling after shutdown (primary circuit pressure Prcs is located at P...) 0main -Pacc (and will further decrease to atmospheric pressure) When you do not want the main valve 2 to open, switch the two-position three-way control valve 1 to the second state (i.e., its output port 111 is connected to the second input port 113). At this time, the sealing cavity 215 of the main valve 2 is under constant pressure (such as the pressure of the safety injection box is about 4-5 MPa), which is greater than the opening setting value P of the main valve 2. 0main When the main valve 2 is closed, the isolation of the main valve 2 is achieved under low pressure conditions in the primary circuit.

[0062] Furthermore, Table 1 shows a comparison of the advantages and disadvantages of the gravity water injection isolation valve of the present invention with several gravity water injection isolation valves commonly used in the field of nuclear power safety mentioned in the background art.

[0063] Table 1

[0064]

[0065]

[0066] In this embodiment,

[0067] The two-position three-way control valve 1 includes a control valve body 11, a control piston assembly, a first solenoid valve, and a second solenoid valve.

[0068] The control valve body 11 has a main chamber 12, a first side chamber 13, and a second side chamber 14. The first side chamber 13 and the second side chamber 14 are respectively located at both ends of the main chamber 12. The control piston assembly is located in the main chamber 12. The first solenoid valve is located in the first side chamber 13, and the second solenoid valve is located in the second side chamber 14.

[0069] The first input port 112, the second input port 113, and the output port 111 are all located on the control valve body 11 and are all connected to the main chamber 12. The control piston assembly includes a control piston rod 15 and multiple control pistons 16 fixed on the control piston rod 15. The multiple control pistons 16 are sequentially and slidably disposed within the main chamber 12 along the axial direction of the control piston rod 15 to divide the main chamber 12 into multiple sub-chambers. Both ends of the control piston rod 15 extend outside the main chamber 12, with one end connected to the first solenoid valve and the other end connected to the second solenoid valve.

[0070] The output port 111 is located on one side of the control piston rod 15 in the radial direction, and the first input port 112 and the second input port 113 are both located on the other side of the control piston rod 15 in the radial direction. 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 111 is connected to the second input port 113 through one of its chambers, so that the two-position three-way control valve 1 is in the second state. When the second solenoid valve is energized, the control piston assembly can move toward the first solenoid valve until the output port 111 is connected to the first input port 112 through one of its chambers, so that the two-position three-way control valve 1 is in the first state.

[0071] In this embodiment, there are four control pistons 16, which divide the main chamber 12 into a first sub-chamber, a second sub-chamber, a third sub-chamber, a fourth sub-chamber, and a fifth sub-chamber in sequence.

[0072] When the two-position three-way control valve 1 is in the first state, the output port 111 is connected to the first input port 112 only through the third branch chamber.

[0073] When the two-position three-way control valve 1 is in the second state, the output port 111 is connected to the second input port 112 only through the third sub-chamber.

[0074] In this embodiment,

[0075] The first solenoid valve includes a first suction cup 17 and a first coil 18, and the second solenoid valve includes a second suction cup 19 and a second coil 110. The first coil 18 and the second coil 110 are respectively disposed on the outer end walls of the main chamber at both ends along the axial direction of the control piston rod, and the first suction cup 17 and the second suction cup 19 are respectively disposed at both ends of the control piston rod 15.

[0076] When the first solenoid valve is energized, the first suction cup 17 moves toward the first coil 18 until it is fixed to it, so as to drive the control piston assembly to move toward the second solenoid valve until the two-position three-way control valve 1 is in the second state. When the second solenoid valve is energized, the second suction cup 19 moves toward the second coil 110 until it is fixed to it, so as to drive the control piston assembly to move toward the first solenoid valve until the two-position three-way control valve 1 is in the first state.

[0077] Because the gravity-injection water isolation valve has a small working pressure range and only has two working states, open and closed, only a single valve is needed to achieve complete control of the main valve.

[0078] The input terminals of the two-position three-way control valve are connected to a primary circuit Prcs and a constant pressure source Pacc, respectively, to provide a constant pressure level for the control valve. The output terminal is connected to the pilot line of the main valve.

[0079] When the first solenoid valve is de-energized and the second solenoid valve is energized, the valve assembly is in standby mode. The piston moves to the left, connecting the pressure output terminal with the pressure input terminal Prcs. At this time, the pressure inside the piston driven by the main isolation valve is equal to Prcs. Due to the design characteristics of the main valve, when Prcs is greater than the automatic opening setpoint of the main valve, the isolation valve is in an isolated state. When the primary circuit pressure is lower than the automatic opening setpoint of the main valve, the isolation valve automatically opens under the action of the drive spring, and begins to perform the gravity water injection function.

[0080] When the first solenoid valve is energized and the second solenoid valve is de-energized, the valve assembly is in a low-pressure isolation state. The piston moves to the right, making the pressure output terminal connected to the pressure input terminal Pacc. At this time, the pressure inside the piston driven by the main isolation valve is equal to that of Pacc. When the pressure in the primary circuit is lower than Pacc, the isolation valves are all in the closed state.

[0081] In the event of a power outage in the current state, the control valve will remain in its original position.

[0082] In this embodiment,

[0083] Multiple two-position three-way control valves 1 are provided, and multiple two-position three-way control valves 1 are arranged in parallel.

[0084] In this embodiment, there are multiple first solenoid valves and multiple second solenoid valves, with multiple first solenoid valves connected in series and multiple second solenoid valves also connected in series.

[0085] 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.

[0086] In this invention, the main valve 2 is the primary flow path for gravity-fed water injection fluid. The invention employs a driving piston and a driving spring as the energy source for opening and closing the main valve 2. The main valve 2 is connected to a two-position three-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.

[0087] 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 system. The valve outlet 211 is located on the side of the main valve body and is used to connect with the gravity water injection pipeline. The main piston assembly is vertically slidable within the main valve body to open or close the valve inlet 29.

[0088] The medium entering the sealed cavity 215 opens the pressure set value P of the main valve 2. 0main Also satisfies: P 0main ×A1-(P 0main -Pgmax)×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.

[0089] In the isolation valve of the present invention, the opening, closing, and sealing of the main valve rely on the combined action of the drive spring, the drive piston pressure, and the system pressure, as detailed below:

[0090] 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 difference between the bottom and top surfaces of the valve disc × 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.

[0091] 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 difference between the bottom and top surfaces of the valve disc × 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.

[0092] In this embodiment, the main spring 26 is mounted on the main piston rod to provide power for driving the piston to move up and down.

[0093] In this embodiment,

[0094] 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.

[0095] 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.

[0096] In this embodiment,

[0097] The main valve body, from bottom to top, includes a valve housing 21, a valve seat 22, and a valve core 23 that are fixedly connected in sequence. The inner cavity of the valve housing 21 forms a valve cavity 24.

[0098] 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.

[0099] In this embodiment,

[0100] 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.

[0101] 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.

[0102] This invention is used to isolate passive gravity water injection pipelines.

[0103] The isolation valve controls the output pressure of the control valve through a solenoid valve, and controls the piston pressure of the main isolation valve through hydraulic pressure, thereby realizing the opening and closing of the valve.

[0104] Assuming the primary loop pressure is Prcs, under normal nuclear power plant operation, Prcs = 15.5 MPa. During normal reactor shutdowns and refueling overhauls, it can be gradually reduced to 0.1 MPa. The constant pressure source injection tank pressure is Pacc, typically around 4-5 MPa. At the outlet of the water injection pipeline connected to the primary loop at the isolation valve, the pressure is Prcs. At the inlet of the water injection pipeline connected to the water source at the isolation valve, the pressure is typically 0.2 MPa (maximum pressure Pgmax if gravity injection is used in the internal refueling tank).

[0105] When the first solenoid valve is de-energized and the second solenoid valve is energized, the piston pressure of the main isolation valve is equal to the pressure of the primary circuit. When the pressure of the primary circuit is much greater than 0.2 MPa, the main isolation valve is in standby (closed) state. After an accident, as the pressure of the primary circuit decreases, the pressure applied by the main circuit is insufficient to overcome the driving force of the main isolation valve drive spring. The main isolation valve opens under the pressure of the drive spring and begins to perform the gravity water injection function.

[0106] When the first solenoid valve is energized and the second solenoid valve is de-energized, the piston pressure of the main isolation valve is approximately 4-5 MPa. When the primary circuit pressure is lower than Pacc, the isolation valve is closed under the combined action of the piston and the pressure in the primary circuit. Even if the primary circuit pressure drops to 0.2 MPa, the pressure applied by the piston of the main isolation valve alone can ensure the reliable closure of the isolation valve.

[0107] Therefore, when the main valve is in standby mode, its opening does not require any action. When the pressure in the primary circuit drops to a certain level, it automatically opens without the need for the solenoid valve to operate. Furthermore, the solenoid valve does not require continuous power supply, allowing the isolation valve to remain open at all times, thus ensuring the long-term operation of the primary circuit's gravity-fed water injection.

[0108] Furthermore, the present invention can achieve reliable isolation of the valve under low pressure and automatic isolation under high pressure (>P0main).

[0109] This isolation valve, while fulfilling the functions of nuclear power plant gravity water injection isolation and water injection, possesses the following technical advantages:

[0110] 1) When the primary circuit pressure reaches the opening condition, the valve can be automatically opened without any external energy input.

[0111] 2) Ensure effective isolation: Ensure effective valve isolation under different operating conditions of the power plant.

[0112] 3) Once the valve is opened, it can remain in the open state without requiring any power supply to maintain the open state.

[0113] 4) After the valve is opened, the isolation function can be restored by switching the control valve state.

[0114] 5) 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.

[0115] 6) Low leakage rate. During normal operation, the valve is sealed by the pressure applied to the piston of the main isolation valve by the primary circuit itself.

[0116] 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. An isolation valve for a passive water injection pipeline in a nuclear power plant, characterized in that, include: Main valve (2) and two-position three-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 passive water injection line and the primary coolant system. 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 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 slides within the main valve body. The main piston (25) is fixed on the main piston rod and located within the sealing cavity (215). The valve disc (28) is fixed on the main piston rod and located within the valve cavity (24). The main spring (26) is located within the sealing cavity (215) and compressed between the main piston (25) and the bottom wall of the valve cavity (24). The two-position three-way control valve (1) has a first input port (112), a second input port (113), and an output port (111). The output port (111) is connected to the sealed cavity (215), the first input port (112) is connected to the primary circuit coolant, and the second input port is connected to a constant pressure source. The two-position three-way control valve (1) has a first state in which the output port (111) is connected to the first input port (112) and disconnected from the second input port (113), and also has a second state in which the output port (111) is connected to the second input port (113) and disconnected from the first input port (112). It can switch between the first state and the second 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: Pgmax < P 0main <Pacc, where Pgmax is the maximum pressure of the passive water injection pipeline and Pacc is the pressure of the constant pressure source; When the primary circuit pressure is normal, switch the two-position three-way control valve (1) to the first state. At this time, the sealing chamber (215) of the main valve (2) is at the primary circuit pressure, which is much greater than the pressure setting value P for opening the main valve. 0main The main valve is closed, thus achieving isolation of the main valve during normal operation of the primary circuit; A primary circuit fault occurs until the pressure drop is less than the pressure setting P required to open the main valve. 0main When the pressure in the sealed cavity (215) is insufficient to overcome the elastic force of the main spring (26), the main valve (2) opens automatically, thereby realizing the gravity water injection function; During the refueling process, the primary circuit pressure Prcs is located at P. 0main Between -Pacc, and further down to normal pressure, when the main valve (2) is not desired to be opened, the two-position three-way control valve (1) is switched to the second state. At this time, the sealing chamber (215) of the main valve is a constant pressure source, which is much greater than the pressure setting value P for opening the main valve. 0main The main valve is closed, thus achieving isolation of the main valve under low pressure conditions in the primary circuit; 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 (24). The valve inlet (29) is located at the bottom of the main valve body and is used to connect with the primary coolant system. The valve outlet (211) is located on the side of the main valve body and is used to connect with the gravity water injection pipeline. 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-(P 0main -Pgmax)×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 gravity of the main piston assembly, F is the elastic force of the main spring when the main valve (2) is closed, and Pgmax is the maximum pressure of the gravity water injection pipeline.

2. The isolation valve for passive water injection pipelines in nuclear power plants according to claim 1, characterized in that, The two-position three-way control valve (1) includes a control valve body (11), a control piston assembly, a first solenoid valve, and a second solenoid valve. The control valve body (11) has a main chamber (12), a first side chamber (13), and a second side chamber (14). The first side chamber (13) and the second side chamber (14) are located at opposite ends of the main chamber (12). The control piston assembly is located in the main chamber (12). The first solenoid valve is located in the first side chamber (13), and the second solenoid valve is located in the second side chamber (14). The first input port (112), the second input port (113), and the output port (111) are all located on the control valve body (11) and are all connected to the main chamber (12). The control piston assembly includes a control piston rod (15) and multiple control pistons (16) fixed on the control piston rod (15). The multiple control pistons (16) are sequentially and slidably sealed in the main chamber (12) along the axial direction of the control piston rod (15) to divide the main chamber (12) into multiple sub-chambers. Both ends of the control piston rod (15) extend out of the main chamber (12), with one end connected to the first solenoid valve and the other end connected to the second solenoid valve. The output port (111) is located on one side of the radial direction of the control piston rod (15), and the first input port (112) and the second input port (113) are both located on the other side of the radial direction of the control piston rod (15). When the first solenoid valve is energized, it can drive the control piston assembly to move toward the second solenoid valve to the output port (111) and communicate with the second input port (113) through one of the chambers, so that the two-position three-way control valve (1) is in the second state. When the second solenoid valve is energized, the control piston assembly can move toward the first solenoid valve to the output port (111) and communicate with the first input port (112) through one of the chambers, so that the two-position three-way control valve (1) is in the first state.

3. The isolation valve for passive water injection pipelines in nuclear power plants according to claim 2, characterized in that, The number of control pistons (16) is four, and the four control pistons (16) divide the main chamber (12) into a first sub-chamber, a second sub-chamber, a third sub-chamber, a fourth sub-chamber, and a fifth sub-chamber in sequence. When the two-position three-way control valve (1) is in the first state, the output port (111) is connected only to the first input port (112) through the third compartment. When the two-position three-way control valve (1) is in the second state, the output port (111) is connected to the second input port (113) only through the third sub-chamber.

4. The isolation valve for passive water injection pipelines in nuclear power plants according to claim 2, characterized in that, The first solenoid valve includes a first suction cup (17) and a first coil (18), and the second solenoid valve includes a second suction cup (19) and a second coil (110). The first coil (18) and the second coil (110) are respectively located on the outer end walls of the main chamber at both ends along the axial direction of the control piston rod, and the first suction cup (17) and the second suction cup (19) are respectively located at both ends of the control piston rod (15). When the first solenoid valve is energized, the first suction cup (17) moves toward the first coil (18) and is fixed thereto, so as to drive the control piston assembly to move toward the second solenoid valve until the two-position three-way control valve (1) is in the second state. When the second solenoid valve is energized, the second suction cup (19) moves toward the second coil (110) and is fixed thereto, so as to drive the control piston assembly to move toward the first solenoid valve until the two-position three-way control valve (1) is in the first state.

5. The isolation valve for passive water injection pipelines in nuclear power plants according to claim 1, characterized in that, The two-position three-way control valve (1) is provided in multiple ways, and the multiple two-position three-way control valves (1) are arranged in parallel.

6. The isolation valve for a passive water injection pipeline in a nuclear power plant according to any one of claims 2-5, characterized in that, 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.

7. The isolation valve for passive water injection pipelines in nuclear power plants according to claim 1, characterized in that, The main spring (26) is mounted on the main piston rod.

8. The isolation valve for passive water injection pipelines in nuclear power plants according to claim 1, 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).

9. The isolation valve for passive water injection pipelines in nuclear power plants according to claim 1, 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).

10. The isolation valve for passive water injection pipelines in nuclear power plants according to claim 9, 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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