Emergency boron injection system

Abstract

The utility model provides an emergency boron injection system which comprises a boron injection box, a gas inlet pipeline, a rupture disk safety device and a boron injection pipeline. The boron injection box is arranged at a position higher than the operation liquid level of the reactor pressure vessel and is used for containing a boron solution; one end of the gas inlet pipeline is connected to a loop gas cavity, and the other end is connected to the boron injection box; the rupture disk safety device is arranged on the air inlet pipeline; one end of the boron injection pipeline is connected to the boron injection box, the other end is connected to the reactor pressure vessel, and a check valve is arranged on the boron injection pipeline. When the reactor works normally, the gas inlet pipeline is closed, and the boron injection pipeline is closed due to the fact that the pressure in the primary loop gas cavity is higher than that in the boron injection box; when an ATWS accident occurs in the reactor, the gas inlet pipeline is opened through automatic action of the rupture disk safety device or manual operation, gas in the primary loop gas cavity enters the boron injection box to achieve pressure balance, a boron solution is injected into the reactor pressure vessel through the boron injection pipeline under the action of gravity, boron injection is achieved, and the whole system is simple in structure and high in reliability.

Description

Technical Field

[0001] The utility model belongs to the field of nuclear power plant system equipment and safety, and particularly relates to an emergency boron injection system. Background Art

[0002] Reactivity control is one of the three major safety functions that must be achieved in a pressurized water reactor, usually realized by the movement of control rods. After various anticipated operational events occur in the reactor, the reactor operating parameters deviate from the normal values. When the protection system set value is reached, an emergency shutdown signal will be triggered, causing the control rods to drop to achieve shutdown. If due to mechanical (such as control rod jamming), electrical (such as the shutdown circuit breaker failing to open), or I&C (such as protection system signal failure) common mode failures or common cause failures, the control rods cannot be inserted to shut down the reactor, that is, an ATWS (Anticipated Transient Without Scram) accident occurs, and the parameters of the reactor primary loop continue to deteriorate, which may cause serious consequences to the reactor.

[0003] For ATWS accidents, the reactor needs to be equipped with a second shutdown system other than control rods to achieve reactivity control and diverse shutdown protection functions under ATWS accidents. Different types of reactors can use different means to introduce negative reactivity into the core. For pressurized water reactors, usually, a boron-containing solution is injected into the primary loop, that is, an emergency boron injection system is set up to achieve diverse shutdowns to mitigate the consequences of ATWS accidents. The boron injection system mostly relies on active components such as pumps and motor-operated valves. When performing boron injection, there are many actions required, the response time is long, and due to the relatively high failure probability of active components, there are failures such as the pump being unable to start and the motor-operated valve being unable to open. When using a standby power supply, there are many loading processes and it cannot be started in time, resulting in the inability to inject boron in time to reduce the core reactivity. Some passive boron injection systems cannot cope with ATWS accidents where multiple initiating events are superimposed and emergency shutdown fails, or they have a complex structure, high operating requirements, and high cost. Therefore, it is necessary to design an emergency boron injection system that can cope with various accident conditions, does not bring additional safety risks, has high system reliability, can effectively improve the safety of the reactor, and at the same time has a low cost and good cost performance. Summary of the Utility Model

[0004] In view of the above-mentioned disadvantages of the prior art, the purpose of the utility model is to provide an emergency boron injection system that can provide passive, fast, and automatic boron injection functions for the most unfavorable type of ATWS accident (the initiating event causes overheating of the primary loop) in a pressurized water reactor, effectively control reactivity and mitigate the consequences of ATWS accidents, improve the reliability of the boron injection system and the safety of the reactor, and for other types of ATWS accidents or other accidents that require boron addition or water addition, the boron injection function can also be realized through manual operation, etc.

[0005] To achieve the above and other related objectives, the present utility model provides an emergency boron injection system, comprising:

[0006] A boron injection tank, which is located higher than the reactor pressure vessel;

[0007] An intake air pipeline, one end of which is connected to the boron injection tank and the other end is connected to the primary loop gas cavity;

[0008] A rupture disk safety device, which is arranged on the intake air pipeline;

[0009] A boron injection pipeline, one end of which is connected to the bottom of the boron injection tank and the other end is connected to the reactor pressure vessel, and a first check valve is arranged on the boron injection pipeline.

[0010] According to an embodiment provided by the present utility model, the boron injection tank is a closed box body, and a partition board is arranged therein. The partition board is connected to the bottom surface and the side surface of the boron injection tank, and the height of the partition board is lower than the height of the boron injection tank;

[0011] The boron injection tank is divided into a gas area and a liquid area by the partition board, and the upper parts of the gas area and the liquid area are communicated with each other.

[0012] According to an embodiment provided by the present utility model, the intake air pipeline comprises:

[0013] A first intake air pipeline, one end of which is connected to the gas area and the other end is connected to the primary loop gas cavity, and the rupture disk safety device is arranged on the first intake air pipeline;

[0014] A second intake air pipeline, one end of which is connected to the gas area and the other end is connected to the primary loop gas cavity, and a first electric valve is arranged thereon;

[0015] The connection ports of the first intake air pipeline and the second intake air pipeline with the gas area are lower than the height of the partition board.

[0016] According to an embodiment provided by the present utility model, at least a part of the first intake air pipeline is arranged as a U-shaped pipe, and the rupture disk safety device is arranged at a position near the bottom on one side of the U-shaped pipe. It comprises a rupture disk, and the bursting pressure of the rupture disk is greater than the difference between the normal operating pressure of the primary loop and the normal operating pressure of the boron injection tank, and less than the difference between the peak pressure of the primary loop in the ATWS accident and the normal operating pressure of the boron injection tank.

[0017] According to an embodiment provided by the present utility model, the boron injection pipeline comprises:

[0018] A first boron injection pipeline, which is connected to the liquid area, and the pipe orifice at the end connected to the liquid area is higher than the height of the bottom surface of the boron injection tank, and a second check valve is arranged on the first boron injection pipeline;

[0019] The second boron injection pipeline is connected to the liquid area, and the height of the pipe orifice at one end connected to the liquid area is higher than the height of the bottom surface of the boron injection tank. A second electric valve is provided on the second boron injection pipeline;

[0020] The third boron injection pipeline, one end of which is connected to the reactor pressure vessel, and the first check valve is provided on the third boron injection pipeline;

[0021] The first boron injection pipeline and the second boron injection pipeline are connected in parallel and are connected to the third boron injection pipeline.

[0022] According to an embodiment provided by the present invention, a first manual valve, a second manual valve and a third manual valve are respectively provided on the first boron injection pipeline, the second boron injection pipeline and the third boron injection pipeline; a fourth manual valve is provided on the second air inlet pipe.

[0023] According to an embodiment provided by the present invention, a fifth manual valve, a sixth manual valve and a first control valve are further provided on the first air inlet pipeline;

[0024] The fifth manual valve and the first control valve are arranged between the rupture disk safety device and the primary loop air cavity, and the sixth manual valve is arranged between the rupture disk safety device and the boron injection tank.

[0025] According to an embodiment provided by the present invention, it further includes:

[0026] A liquid filling pipeline, which is connected to the boron injection tank and injects a boron-containing solution into the boron injection tank;

[0027] A liquid draining pipeline, which is connected to the boron injection tank and discharges the boron solution in the boron injection tank to adjust the liquid level in the boron injection tank.

[0028] According to an embodiment provided by the present invention, it further includes:

[0029] An air filling pipeline, which is connected to the boron injection tank and fills the boron injection tank with gas;

[0030] An exhaust pipeline, on which a second control valve and a seventh manual valve are provided, and discharges the gas in the boron injection tank to adjust the pressure in the boron injection tank.

[0031] According to an embodiment provided by the present invention, it further includes a pressure relief pipeline, which is connected to the boron injection tank, and a safety valve is provided on it. When the pressure in the boron injection tank is too high, the gas is discharged through the safety valve to prevent overpressure.

[0032] The emergency boron injection system of the present utility model can quickly respond to the most unfavorable type of ATWS accident (the primary loop overheats caused by the initiating event), and can also respond to the ATWS accident where the primary loop is subcooled caused by other initiating events through simple and quick operations. In addition, under any accident conditions where boron or water needs to be supplemented to the reactor primary loop system, if other boron supplementation or water supplementation channels are unavailable, this system can also be manually activated to achieve water supplementation and boronization to the primary loop, being able to cope with various accident conditions, significantly enhancing the reactor's defense-in-depth level and safety; the system has a simple structure, is easy to implement, has high reliability, and requires a relatively low construction cost, and can be applied to newly built pressurized water reactors and can also be used for the transformation of existing pressurized water reactor systems, being able to improve the reactor's safety and having a good cost performance. Description of the Drawings

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings required for describing the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 It is a schematic structural diagram of an emergency boron injection system provided by an embodiment of the present utility model;

[0035] Figure 2 It is a front view of a boron injection tank of an emergency boron injection system provided by an embodiment of the present utility model;

[0036] Figure 3 It is a top view of a boron injection tank of an emergency boron injection system provided by an embodiment of the present utility model;

[0037] Figure 4 It is a side view of a boron injection tank of an emergency boron injection system provided by an embodiment of the present utility model.

[0038] Label Explanation:

[0039] 100, boron injection tank; 200, intake pipeline; 300, rupture disk safety device; 400, boron injection pipeline; 500, liquid filling pipeline; 600, liquid drainage pipeline; 700, gas filling pipeline; 800, exhaust pipeline; 900, pressure relief pipeline;

[0040] 110, partition board; 120, gas area; 130, liquid area;

[0041] 210, first intake pipeline; 211, first intake pipe; 212, first control valve; 213, fifth manual valve; 214, sixth manual valve;

[0042] 220. Second intake pipeline; 221. Second intake pipe; 222. First electric valve; 223. Fourth manual valve;

[0043] 410. First boron injection pipeline; 411. First boron injection pipe; 412. Second check valve; 413. First manual valve;

[0044] 420. Second boron injection pipeline; 421. Second boron injection pipe; 422. Second electric valve; 423. Second manual valve;

[0045] 430. Third boron injection pipeline; 431. First check valve; 432. Third manual valve;

[0046] 810. Second control valve; 820. Seventh manual valve; 910. Safety valve. Detailed implementation mode

[0047] The following uses specific specific examples to illustrate the implementation mode of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0048] It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the drawings, rather than being drawn according to the number, shape, and size of the components during actual implementation. The type, quantity, and ratio of each component during actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0049] Please refer to Figure 1, the present utility model provides an emergency boron injection system, including a boron injection tank 100, an air inlet pipeline 200, a rupture disk safety device 300, a boron injection pipeline 400, a liquid filling pipeline 500, a liquid draining pipeline 600, an air filling pipeline 700, an exhaust pipeline 800 and a pressure relief pipeline 900. The boron injection tank 100 is used to accommodate boron solution and gas, and its position is higher than that of the reactor pressure vessel; one end of the air inlet pipeline 200 is connected to the boron injection tank 100, and the other end is connected to the primary loop gas cavity. For a loop-type pressurized water reactor (such as CPR1000, AP1000, EPR, Hualong One, etc.), the primary loop gas cavity is the upper gas space of the pressurizer, and for an integral pressurized water reactor (such as NHR200, ACP100, etc.), the primary loop gas cavity is the upper gas space of the reactor pressure vessel; the rupture disk safety device 300 is arranged on the air inlet pipeline 200. When the pressure difference on both sides of the rupture disk safety device 300 reaches a predetermined value, the rupture disk immediately acts to form a relief port, and the gas in the primary loop gas cavity can enter the boron injection tank 100 through the air inlet pipeline 200; one end of the boron injection pipeline 400 is connected to the bottom of the boron injection tank 100, and the other end is connected to the reactor pressure vessel. A first check valve 431 is arranged thereon to prevent the fluid in the reactor pressure vessel from entering the boron injection tank 100 through the boron injection pipeline 400. The liquid filling pipeline 500 and the liquid draining pipeline 600 are connected to the boron injection tank 100 and are used to adjust the liquid level in the boron injection tank 100; the air filling pipeline 700 and the exhaust pipeline 800 are connected to the boron injection tank 100 and are used to adjust the pressure in the boron injection tank 100; the pressure relief pipeline 900 is connected to the boron injection tank 100 and is used to discharge gas to prevent the boron injection tank 100 from overpressurizing.

[0050] When the most unfavorable type I anticipated operational occurrence in the reactor (the initial event causes overheating of the primary loop, such as loss of power supply, loss of secondary loop load, loss of feedwater flow, uncontrolled lifting of control rods, etc.) is superimposed with an ATWS accident where the emergency shutdown fails, the pressure and temperature of the primary loop rise. The reactor should have been emergently shut down but the control rods failed to be inserted to shut down, the core power remains at a relatively high level, the heat in the primary loop cannot be completely removed, and the pressure of the primary loop continues to rise until the pressure difference with the boron injection tank 100 reaches the bursting pressure of the rupture disk safety device 300. The rupture disk safety device 300 immediately acts, the air inlet pipeline 200 opens, and the high-pressure gas in the primary loop gas cavity enters the boron injection tank 100, causing its pressure to rapidly increase and finally reach equilibrium with the pressure of the primary loop; since the liquid level of the boron injection tank 100 is higher than that of the reactor pressure vessel, the boron-containing solution is injected into the reactor pressure vessel through the boron injection pipeline 400 under the action of gravity. The primary loop gas cavity remains connected to the gas area of the boron injection tank, and the boron-containing solution can continuously be injected into the reactor pressure vessel to inhibit the core reactivity and shut down the reactor.

[0051] Please refer to Figures 1 to 4, according to an embodiment provided by the present utility model, the boron injection tank 100 is a sealed box, and its shape can be a cuboid, a cylinder, etc., for storing boron-containing solution; the boron injection tank 100 is arranged at a position higher than the operating liquid level of the reactor pressure vessel, and can realize the boron injection function through pressure balance and gravity when an accident occurs. A number of nozzles are provided on the boron injection tank 100 for connecting with pipelines on various pipelines such as the intake gas pipeline 200, the boron injection pipeline 400, the liquid filling pipeline 500, the liquid drainage pipeline 600, the gas filling pipeline 700, the exhaust gas pipeline 800 and the pressure relief pipeline 900.

[0052] Please refer to Figures 1 to 4 , according to an embodiment provided by the present utility model, a partition 110 is arranged inside the boron injection tank 100. For example, the partition 110 can be welded inside the boron injection tank 100. The partition 110 is connected to the bottom surface and the side surface of the boron injection tank 100, and the height of the partition 110 is lower than the height of the boron injection tank 100. The boron injection tank 100 is separated into a gas zone 120 and a liquid zone 130 by the partition 110, and the upper parts of the gas zone 120 and the liquid zone 130 are communicated; the gas zone 120 is filled with inert gases such as nitrogen, argon, etc. to maintain a certain pressure inside the boron injection tank. The liquid zone 130 is used to hold the boron-containing solution, and its liquid level should be lower than the height of the partition 110. The upper part of the liquid zone 130 is in gas-liquid contact and communicated to keep the pressure equal. The gas zone 120 and the liquid zone 130 are separated by the partition 110. When the high-pressure gas in the primary loop gas cavity enters the boron injection tank 100 from the intake gas pipeline 200, it first enters the gas zone 120, making the gas phase mix evenly, avoiding impact and fluctuation on the liquid zone 130, and at the same time preventing the airflow from entraining the fragments of the rupture disk into the boron-containing solution in the liquid zone 130.

[0053] Please refer to Figures 1 to 4 , according to an embodiment provided by the present utility model, the intake gas pipeline 200 includes two parallel first intake gas pipelines 210 and second intake gas pipelines 220. One end of the first intake gas pipeline 210 is connected to the gas zone 120, and the other end is connected to the primary loop gas cavity. The rupture disk safety device 300 is arranged on the first intake gas pipeline 210; one end of the second intake gas pipeline 220 is connected to the gas zone 120, and the other end is connected to the primary loop gas cavity; the connection ports of the first intake gas pipeline 210 and the second intake gas pipeline 220 with the gas zone 120 are lower than the height of the partition 110, and the airflow in the primary loop gas cavity enters the gas zone 120 through the first intake gas pipeline 210 and the second intake gas pipeline 220 without causing impact and fluctuation on the boron solution in the liquid zone 130.

[0054] Please refer to Figures 1 to 4, according to an embodiment provided by the present utility model, the upstream of the first intake pipeline 210 is connected to a loop gas chamber, and the downstream is connected to the boron injection tank 100 through the first intake pipe 211. A first control valve 212 is installed upstream of the first intake pipeline 210. The rupture disk safety device 300 is connected to the upstream and downstream pipelines. The first control valve 212 is arranged between the rupture disk safety device 300 and the loop gas chamber to regulate the medium flow rate and pipeline pressure. At least a part of the first intake pipeline 210 is arranged as a U-shaped pipe. The rupture disk safety device 300 is arranged at a position close to the bottom on one side of the U-shaped pipe to prevent the rupture fragments from being carried into the boron injection tank 100 when the first intake pipeline 210 discharges fluid.

[0055] Specifically, the first intake pipeline 210 is connected between the loop gas chamber and the boron injection tank 100. A section of U-shaped pipeline with an upward opening can be arranged thereon. The rupture disk safety device 300 is connected to one end of the U-shaped pipeline close to the boron injection tank 100 and is located at a lower position of the U-shaped pipeline. The first intake pipe 211 can also be arranged as an L-shaped pipe, with one end connected to the U-shaped pipeline and the other end connected to the boron injection tank 100. The fragments broken or fallen off after the rupture disk safety device 300 bursts can fall to the bottom of the pipeline. Since the fragments are located at the included angle at the bottom of the U-shaped pipeline, they are not easily directly carried into the boron injection tank 100 by the air flow through the first intake pipe 211, thereby effectively preventing the fragments from entering the boron injection tank 100.

[0056] Please refer to Figures 1 to 4, according to an embodiment provided by the present utility model, the rupture disk safety device 300 includes a rupture disk and other components such as a holder or a support ring. The rupture disk or the rupture disk assembly is clamped in a proper position by the holder, and the rupture disk safety device 300 is connected to the upstream and downstream pipelines by appropriate connection methods such as flanges and welding. When the pressure difference on both sides of the rupture disk reaches a predetermined value, the rupture disk will act immediately, rupture or fall off, and release the fluid medium. The bursting pressure of the rupture disk is greater than the difference between the normal operating pressure of the primary loop and the normal operating pressure of the boron injection tank, and less than the difference between the peak pressure of the primary loop in the ATWS accident (this pressure should be less than the pressure limit of the primary loop specified by the accident safety criterion) and the normal operating pressure of the boron injection tank 100, and a certain margin is reserved to ensure that the first intake pipeline 210 will not be opened due to the action of the rupture disk safety device 300 during the normal operation of the reactor, and the rupture disk safety device 300 can act quickly during the ATWS accident, release pressure and exhaust gas in time to achieve the boron injection and reactor shutdown action. When the reactor experiences the most unfavorable type of anticipated operational occurrence (the initiating event causes overheating of the primary loop, such as loss of power supply, loss of load in the secondary loop, loss of feedwater flow, uncontrolled rod withdrawal, etc.) superimposed on the ATWS accident of failed emergency shutdown, the pressure of the primary loop continues to rise. When the pressure difference between the pressure in the gas cavity of the primary loop and the pressure of the boron injection tank 100 reaches the bursting pressure of the rupture disk safety device 300, the rupture disk safety device 300 acts immediately to burst, and the intake pipeline where it is located becomes an open state. The high-pressure gas in the gas cavity of the primary loop enters the gas area 120 of the boron injection tank 100 through the first intake pipeline 210, causing the pressure in the boron injection tank 100 to increase rapidly and finally reach equilibrium with the pressure of the primary loop. The boron-containing solution in the boron injection tank 100 is injected into the reactor pressure vessel under the action of gravity to inhibit the core reactivity and shut down the reactor.

[0057] Please refer to Figures 1 to 4 , according to an embodiment provided by the present utility model, the upstream of the second intake pipeline 220 is connected to the gas cavity of the primary loop, and the downstream is connected to the boron injection tank 100 through the second intake pipe 221, and a first electric valve 222 is provided thereon. The first electric valve 222 is an electric globe valve and is arranged upstream of the pipeline to control the opening and closing of the second intake pipeline 220. When the reactor experiences other anticipated operational occurrences (the initiating event causes overcooling of the primary loop, such as an increase in feedwater flow in the secondary loop, an increase in load, etc.) superimposed on the ATWS accident of failed emergency shutdown, the pressure and temperature of the primary loop decrease, and the reactor should have been shut down emergently but the control rods failed to be inserted for shutdown, and the core power remains at a relatively high level. At this time, the rupture disk safety device 300 of the first intake pipeline 210 cannot act automatically, and the second intake pipeline 220 where it is located can be opened by controlling the first electric valve 222, so that the gas cavity of the primary loop is communicated with the boron injection tank 100, and boron injection and reactor shutdown are performed on the reactor by gravity after the pressures of the gas cavity of the primary loop and the boron injection tank 100 are balanced.

[0058] Please refer to Figures 1 to 4 According to an embodiment provided by the present utility model, the first electric valve 222 is powered by an external power supply and is also equipped with a plant-internal safety power supply. When off-site power is available, the operator can open the first electric valve 222, thereby opening the second intake gas pipeline 220 where it is located, keeping the primary loop gas cavity in communication with the boron injection tank 100, and realizing boron injection by relying on pressure balance and gravity; when off-site power fails, the operator can switch to the safety power supply and open the first electric valve 222 to achieve boron injection.

[0059] Please refer to Figures 1 to 4 According to an embodiment provided by the present utility model, the emergency boron injection system can quickly respond to the most unfavorable type of ATWS accident (the primary loop overheats caused by the initiating event) through the rupture disk safety device 300, open the first intake gas pipeline 210, and automatically start boron injection by gravity after the pressure in the primary loop gas cavity and the boron injection tank 100 is balanced to safely shut down the reactor. The analysis results of a 200MW integral pressurized water reactor losing all AC power for an ATWS accident show that the pressure difference set value of the rupture disk safety device 300 can be reached about 50 seconds after the accident occurs, triggering the automatic start of the emergency boron injection system and timely shutting down the reactor. For other ATWS accidents where the primary loop is subcooled caused by other initiating events, the accident process and consequences are relatively mild, and boron injection can be achieved by the operator manually opening the second intake gas pipeline 220, and only need to manually operate and open the first electric valve 222. The operation is convenient and reliable, reducing the probability of human error. This valve is equipped with a safety power supply and can effectively cope with the adverse situation of off-site power failure.

[0060] Please refer to Figures 1 to 4 According to an embodiment provided by the present utility model, the boron injection pipeline 400 includes a first boron injection pipeline 410, a second boron injection pipeline 420, and a third boron injection pipeline 430. The first boron injection pipeline 410 is connected to the liquid area 130, and the pipe orifice height of the end connected to the liquid area 130 is higher than the bottom surface height of the boron injection tank 100. The second boron injection pipeline 420 is connected to the liquid area 130, and the pipe orifice height of the end connected to the liquid area 130 is higher than the bottom surface height of the boron injection tank 100. The first boron injection pipeline 410 and the second boron injection pipeline 420 are connected in parallel and are connected to the third boron injection pipeline 430; one end of the third boron injection pipeline 430 is connected to the reactor pressure vessel. The boron solution in the boron injection tank 100 flows out through the first boron injection pipeline 410 and the second boron injection pipeline 420 and is injected into the reactor pressure vessel through the third boron injection pipeline 430 to achieve reactor shutdown; both the first boron injection pipeline 410 and the second boron injection pipeline 420 have the ability to achieve 100% boron injection to safely shut down the reactor after being opened. The second boron injection pipeline 420 serves as a redundant backup for the first boron injection pipeline 410.

[0061] Please refer to Figures 1 to 4, according to an embodiment provided by the present utility model, the upstream of the first boron injection pipeline 410 is connected to the boron injection tank 100 through the first boron injection pipe 411, and the downstream is connected to the reactor pressure vessel through the third boron injection pipeline 430. The first boron injection pipe 411 is inserted from the bottom of the liquid area 130 of the boron injection tank 100, and the end extends into the boron injection tank 100 for a certain length. A first check valve 431 is provided on the third boron injection pipeline 430, and a second check valve 412 is provided on the first boron injection pipeline 410 to prevent the fluid in the reactor pressure vessel from flowing back into the boron injection tank 100 and ensure that the boron solution in the boron injection tank 100 is smoothly injected into the reactor pressure vessel. When the intake air pipeline 200 is not opened, the pressure in the boron injection tank 100 is relatively low, and the first boron injection pipeline 410 and the third boron injection pipeline 430 are kept closed by the check valves; when the intake air pipeline 200 is opened, the pressure in the boron injection tank 100 reaches equilibrium with the primary loop gas cavity. Since the liquid level of the boron injection tank 100 is higher than the liquid level of the reactor pressure vessel, the boron-containing solution is injected into the reactor pressure vessel under the action of gravity through the first boron injection pipeline 410 and the third boron injection pipeline 430. At this time, the check valves are opened, and the boron injection tank 100 is connected to the reactor pressure vessel through the first boron injection pipeline 410 and the third boron injection pipeline 430. And because the primary loop gas cavity is kept connected to the gas area 120 of the boron injection tank 100, the boron-containing solution can be continuously injected into the reactor pressure vessel to inhibit the core reactivity and shut down the reactor. When the liquid level of the boron injection tank 100 is lower than the height of the end of the first boron injection pipe 411, the boron-containing solution below the end remains in the tank, and a small amount of boron-containing solution in the pipe will still be injected into the reactor pressure vessel under the action of gravity. The liquid level in the pipe finally reaches equilibrium with the liquid level of the reactor pressure vessel, and the gas fills the space above the remaining boron-containing solution in the tank, and the gas pressure is kept in balance with the primary loop pressure.

[0062] Please refer to Figures 1 to 4 , according to an embodiment provided by the present utility model, the upstream of the second boron injection pipeline 420 is connected to the boron injection tank 100 through the second boron injection pipe 421, a second electric valve 422 is installed downstream, and it is connected to the reactor pressure vessel through the third boron injection pipeline 430. The second boron injection pipe 421 is inserted from the bottom of the liquid area 130 of the boron injection tank 100, and the end extends into the boron injection tank 100 for a certain length. The second electric valve 422 is an electric globe valve, which is used to control the opening and closing of the second boron injection pipeline 420. The second electric valve 422 is also powered by an external power supply and is equipped with a safety power supply, which can effectively cope with the severe situation of off-site power failure. When the intake air pipeline 200 is opened, the pressure in the boron injection tank 100 reaches equilibrium with the primary loop gas cavity. At this time, by opening the second electric valve 422, the second boron injection pipeline 420 is kept open. Since the liquid level of the boron injection tank 100 is higher than the liquid level of the reactor pressure vessel, the boron-containing solution in the boron injection tank 100 is injected into the reactor pressure vessel under the action of gravity through the second boron injection pipeline 420 and the third boron injection pipeline 430 to inhibit the core reactivity and shut down the reactor.

[0063] Please refer to Figures 1 to 4 , according to an embodiment provided by the present utility model, when the intake pipeline 200 is opened, the high-pressure gas flow in the primary loop gas chamber enters the boron injection tank 100 through the intake pipeline 200. When the pressure in the primary loop gas chamber is balanced with that in the boron injection tank 100, the boron solution in the boron injection tank 100 is injected into the reactor pressure vessel through the first boron injection pipeline 410 and the third boron injection pipeline 430 under the action of gravity, inhibiting the core reactivity and shutting down the reactor; when the first boron injection pipeline 410 fails, the second boron injection pipeline 420 is opened by manually opening the second electric valve 422, and the boron solution in the boron injection tank 100 is injected into the reactor pressure vessel through the second boron injection pipeline 420 and the third boron injection pipeline 430 under the action of gravity; both the first boron injection pipeline 410 and the second boron injection pipeline 420 have the ability to inject 100% boron to safely shut down the reactor after being opened. The boron injection adopts a passive design concept, and the system components involved rely on gravity and pressure difference for driving, without external power supply, pump drive or manual operation, which can significantly improve the system reliability and reactor safety.

[0064] Please refer to Figures 1 to 4 , according to an embodiment provided by the present utility model, manual stop valves are respectively arranged on each pipeline for controlling the opening and closing of each pipeline and for adjusting and maintaining the pipeline, etc. Specifically, a first manual valve 413 is arranged on the first boron injection pipeline 410, a second manual valve 423 is arranged on the second boron injection pipeline 420, a third manual valve 432 is arranged on the third boron injection pipeline 430, a fourth manual valve 223 is arranged on the second intake pipeline 220, and a fifth manual valve 213 and a sixth manual valve 214 are arranged on the first intake pipeline 210. The fifth manual valve 213 is arranged between the rupture disc safety device 300 and the primary loop gas chamber, and the sixth manual valve 214 is arranged between the rupture disc safety device 300 and the boron injection tank 100.

[0065] Please refer to Figures 1 to 4, according to an embodiment provided by the present utility model, on the first intake pipeline 210, a fifth manual valve 213, a first control valve 212, a rupture disk safety device 300, and a sixth manual valve 214 are sequentially arranged from the primary loop gas cavity to the boron injection tank 100; on the second intake pipeline 220, a first electric valve 222 and a fourth manual valve 223 are sequentially arranged from the primary loop gas cavity to the boron injection tank 100; on the first boron injection pipeline 410, a first manual valve 413 and a second check valve 412 are sequentially arranged from the boron injection tank 100 to the third boron injection pipeline 430; on the second boron injection pipeline 420, a second manual valve 423 and a second electric valve 422 are sequentially arranged from the boron injection tank 100 to the third boron injection pipeline 430; on the third boron injection pipeline 430, a third manual valve 432 and a first check valve 431 are sequentially arranged from the boron injection tank 100 to the reactor pressure vessel. By setting the valves on each pipeline, it is ensured that the system will not affect the normal operation of the reactor in the standby state, and rapid boron injection can be achieved in the event of an ATWS accident to shut down the reactor in a timely manner, with high reliability.

[0066] Please refer to Figures 1 to 4 , according to an embodiment provided by the present utility model, the liquid filling pipeline 500 is connected to the boron injection tank 100 for injecting boron-containing solution into the boron injection tank 100; the liquid draining pipeline 600 is connected to the boron injection tank 100 for draining the boron solution in the boron injection tank 100 to adjust the liquid level in the boron injection tank 100. The boron solution in the boron injection tank 100 is adjusted to the required capacity through the liquid filling pipeline 500 and the liquid draining pipeline 600.

[0067] Please refer to Figures 1 to 4 , according to an embodiment provided by the present utility model, the gas filling pipeline 700 is connected to the boron injection tank 100 to fill gas into the boron injection tank 100; the exhaust pipeline 800 is connected to the boron injection tank 100 to discharge the gas in the boron injection tank 100 to adjust the pressure in the boron injection tank 100. A second control valve 810 and a seventh manual valve 820 are arranged on the exhaust pipeline 800. The opening and closing of the pipeline are adjusted through the second control valve 810 and the seventh manual valve 820, and the amount of discharged gas is controlled to adjust the pressure in the boron injection tank 100.

[0068] Please refer to Figures 1 to 4 , according to an embodiment provided by the present utility model, the pressure relief pipeline 900 is connected to the boron injection tank 100, and a safety valve 910 is arranged thereon. When the pressure in the boron injection tank 100 is too high, gas is discharged through the safety valve 910 to prevent overpressure.

[0069] Please refer to Figures 1 to 4, when the reactor is operating normally, the system is in standby state. At this time, the liquid level and pressure in the boron injection tank 100 have been pre-adjusted to preset values through the liquid filling pipeline 500, the liquid drainage pipeline 600, the gas filling pipeline 700 and the exhaust pipeline 800. The pressure in the boron injection tank 100 is less than the pressure of the primary loop, and the liquid level of the boron solution in the liquid area 130 is lower than the height of the partition 110. The rupture disc safety device 300 on the first gas inlet pipeline 210 is in the closed state, the first control valve 212, the fifth manual valve 213 and the sixth manual valve 214 are in the open state, and the first gas inlet pipeline 210 is closed; the first electric valve 222 on the second gas inlet pipeline 220 is in the closed state, the fourth manual valve 223 is in the open state, and the second gas inlet pipeline 220 is closed; the first manual valve 413 on the first boron injection pipeline 410, the second manual valve 423 on the second boron injection pipeline 420 and the third manual valve 432 on the third boron injection pipeline 430 are in the open state, and the second electric valve 422 on the second boron injection pipeline 420 is in the closed state. Since the pressure of the primary loop is higher than the pressure in the boron injection tank 100 during normal operation of the reactor, the second check valve 412 on the first boron injection pipeline 410 and the first check valve 431 on the third boron injection pipeline 430 are both in the closed state, that is, the first boron injection pipeline 410, the second boron injection pipeline 420 and the third boron injection pipeline 430 are closed. Therefore, all the gas inlet pipes and boron injection pipes are in the closed state during normal operation of the reactor, and there is no fluid flow.

[0070] Please refer to Figures 1 to 4, when the most unfavorable type of anticipated operational occurrence in the reactor (the initiating event causes overheating in the primary circuit, such as loss of power, loss of load in the secondary circuit, loss of feedwater flow, uncontrolled rod withdrawal, etc.) is superimposed with an ATWS accident where emergency shutdown fails, the pressure and temperature in the primary circuit rise. The reactor should have been emergently shut down but the control rods failed to insert for shutdown, the core power remains at a relatively high level, the heat in the primary circuit cannot be fully removed, and the pressure in the primary circuit continues to rise until the pressure difference between the primary circuit and the boron injection tank 100 reaches the bursting pressure of the rupture disk safety device 300, causing the rupture disk to actuate and the first intake pipe 211 where it is located to become in an open state. After the intake pipe is opened, the high-pressure gas in the gas cavity of the primary circuit enters the gas area 120 of the boron injection tank 100, causing the pressure in the boron injection tank 100 to increase rapidly and eventually reach equilibrium with the pressure in the primary circuit. Since the liquid level of the boron injection tank 100 is higher than the liquid level of the reactor pressure vessel, the boron-containing solution is injected into the reactor pressure vessel under the action of gravity through the first boron injection pipeline 410 where the second check valve 412 is located and the third boron injection pipeline 430 where the first check valve 431 is located, suppressing the core reactivity and shutting down the reactor. Since the gas cavity of the primary circuit remains connected to the gas area 120 in the boron injection tank 100, the boron-containing solution can be continuously injected into the reactor pressure vessel. When the liquid level in the boron injection tank 100 is lower than the height of the end of the boron injection pipe, the boron-containing solution below the end remains in the tank, and a small amount of the boron-containing solution in the pipe will still be injected into the reactor pressure vessel under the action of gravity, and the liquid level in the pipe will eventually reach equilibrium with the liquid level of the reactor pressure vessel, and the gas fills the space above the remaining boron-containing solution in the tank, and the gas pressure remains in equilibrium with the pressure in the primary circuit.

[0071] Please refer to Figures 1 to 4 , when other anticipated operational occurrences in the reactor (the initiating event causes subcooling in the primary circuit, such as an increase in feedwater flow in the secondary circuit, an increase in load, etc.) are superimposed with an ATWS accident where emergency shutdown fails, the pressure and temperature in the primary circuit drop. The reactor should have been emergently shut down but the control rods failed to insert for shutdown, and the core power remains at a relatively high level. In this case, the rupture disk safety device 300 cannot actuate automatically, and it is necessary to rely on manual operation to open the flow path of the second intake pipeline 220. When off-site power is available, the operator can open the first electric valve 222, and the second intake pipeline 220 where it is located will be opened, and boron injection can be achieved by relying on pressure balance and gravity; when off-site power fails, the operator switches to the safety power supply and opens the first electric valve 222 to achieve boron injection.

[0072] The operation of the emergency boron injection system of the present utility model does not depend on the instrument control protection platform. Even in the case of an ATWS accident where the instrument control protection system has a common cause failure, the emergency boron injection system can still be automatically started or manually started by the operator. Moreover, for manual start, only the first electric valve 222 needs to be opened to achieve boron injection, and the operation is simple. In addition, under any accident conditions where boron or water needs to be supplemented to the primary loop system of the reactor, if other boron or water supplementing channels are unavailable, this system can also be manually started to achieve water supplement and boronization of the primary loop. It can effectively enhance the depth of defense level and safety of the reactor.

[0073] Please refer to Figures 1 to 4 , if the first control valve 212 is accidentally closed, it will not affect the emergency boron injection system and the primary loop, but will prevent the first air inlet pipeline 210 where the rupture disk safety device 300 is located from automatically opening, affecting the automatic boron injection function. Therefore, subsequently, the operator needs to reset and open the first control valve 212 according to the monitored valve position signal.

[0074] Please refer to Figures 1 to 4 , if the first electric valve 222 is accidentally opened, the second air inlet pipeline 220 where it is located will be opened, causing the emergency boron injection system to start, injecting boron-containing solution into the primary loop, resulting in a decrease in the core power, a decrease in the primary loop pressure, an increase in the water level, triggering an emergency shutdown by the protection signal related to the primary loop pressure or water level, or causing the reactor to shut down due to the accumulation of boron concentration in the core, which will not pose a challenge to the reactor safety.

[0075] Please refer to Figures 1 to 4 , if the second electric valve 422 is accidentally opened, the second boron injection pipeline 420 where it is located will be opened. Since the pressure of the boron injection tank 100 (even with the pressure corresponding to the liquid level height difference) is less than the primary loop pressure, under the action of the first check valve 431, it will not cause boron injection into the primary loop, and the emergency boron injection system and the primary loop will not be affected. Subsequently, the operator needs to reset and close the second electric valve 422 according to the monitored valve position signal.

[0076] Please refer to Figures 1 to 4, if the safety valve 910 is accidentally opened, the pressure of the boron injection tank 100 will decrease. If the safety valve 910 can return to its seat in time, the emergency boron injection system will be hardly affected; if the safety valve 910 cannot return to its seat, that is, it remains stuck open (with a very low probability), the pressure of the boron injection tank 100 will continue to decrease, which may cause the bursting disc safety device 300 to actuate and the first intake pipeline 210 to open, resulting in the startup of the emergency boron injection system. After the first intake pipeline 210 is opened, the stuck-open state of the safety valve 910 is equivalent to a break in the primary loop. Its transient response process is similar to that of other primary loop loss-of-coolant accidents in a pressurized water reactor (such as accidental opening of the pressurizer safety valve or the safety valve on the reactor pressure vessel). Since the pressurizer safety valve or the safety valve on the reactor pressure vessel is larger in size, the stuck-open state of the safety valve 910 can be enveloped by other loss-of-coolant accidents and will not cause more severe accident consequences.

[0077] Please refer to Figures 1 to 4 , if the second control valve 810 is accidentally opened, since the seventh manual valve 820 remains closed, it will not affect the emergency boron injection system and the primary loop.

[0078] Therefore, if a system component malfunction event occurs in the emergency boron injection system of the present utility model, it will not affect the reactor, or can be enveloped by other accidents already considered in the design. Applying it to the reactor will not bring additional safety risks and has relatively high reliability.

[0079] The emergency boron injection system of the present utility model has a simple structure and is easy to implement. Through two schemes of automatic boron injection and manual boron injection, it can quickly respond to the most unfavorable type of ATWS accident (the primary loop overheats caused by the initiating event). For ATWS accidents where the primary loop is subcooled due to other initiating events, boron injection can also be achieved through manual operation, and the operation is simple, convenient, and reliable; the malfunction of system components will not bring additional safety risks to the reactor. The entire system has high reliability, can cope with various accident conditions, effectively enhances the depth of defense level and safety of the reactor, can be applied to newly built pressurized water reactors or the transformation of existing pressurized water reactor systems, has a relatively low construction cost, and has good cost performance.

[0080] The above-described embodiments are only used to illustrate the technical solutions of the present utility model and are not intended to limit them; although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present utility model, and should all be included within the protection scope of the present utility model.

[0081] Except for the technical features described in the specification, the remaining technical features are well-known technologies to those skilled in the art. To highlight the innovative features of the present utility model, the remaining technical features will not be elaborated herein.

Claims

1. An emergency boron injection system, characterized in that: include: The boron injection box is located higher than the reactor pressure vessel; An air inlet pipeline, one end of which is connected to the boron injection box, and the other end of which is connected to the primary circuit air cavity; A bursting disc safety device, the bursting disc safety device being arranged on the air inlet pipeline; The boron injection pipeline has one end connected to the bottom of the boron injection box and the other end connected to the reactor pressure vessel. The boron injection pipeline is provided with a first check valve.

2. The emergency boron injection system according to claim 1, characterized in that: The boron injection box is a closed box, in which a partition is arranged, the partition is connected to the bottom and side of the boron injection box, and the height of the partition is lower than the height of the boron injection box; The boron injection box is divided into a gas zone and a liquid zone by the partition, and the gas zone is communicated with the upper part of the liquid zone.

3. The emergency boron injection system according to claim 2, characterized in that: The air inlet pipeline comprises: a first air inlet pipeline, one end of which is connected to the air zone and the other end of which is connected to a primary circuit air cavity, the bursting disc safety device being arranged on the first air inlet pipeline; A second air inlet pipeline, one end of which is connected to the air zone, and the other end of which is connected to the primary air cavity, and a first electric valve is arranged on the second air inlet pipeline; The heights of the connection ports of the first air inlet pipeline and the second air inlet pipeline with the air zone are lower than the height of the partition.

4. The emergency boron injection system according to claim 3, characterized in that: The first air inlet pipeline is at least partially configured as a U-shaped tube, and the bursting disc safety device is arranged on one side of the U-shaped tube near the bottom, which includes a bursting disc, and the bursting pressure of the bursting disc is greater than the difference between the normal operating pressure of a circuit and the normal operating pressure of the boron injection box, and is less than the difference between the peak pressure of a circuit under an ATWS accident and the normal operating pressure of the boron injection box.

5. The emergency boron injection system according to claim 3, characterized in that: The boron injection pipeline comprises: A first boron injection pipeline is connected to the liquid area, and the height of the pipe opening connected to one end of the liquid area is higher than the height of the bottom surface of the boron injection box, and a second check valve is arranged on the first boron injection pipeline; A second boron injection pipeline is connected to the liquid area, and the height of the pipe opening connected to one end of the liquid area is higher than the height of the bottom surface of the boron injection box, and a second electric valve is arranged on the second boron injection pipeline; A third boron injection pipeline, one end of which is connected to the reactor pressure vessel, and the first check valve is arranged on the third boron injection pipeline; The first boron injection pipeline is connected in parallel with the second boron injection pipeline, and is connected to the third boron injection pipeline.

6. The emergency boron injection system according to claim 5, characterized in that: The first boron injection pipeline, the second boron injection pipeline and the third boron injection pipeline are respectively provided with a first manual valve, a second manual valve and a third manual valve; the second air inlet pipeline is provided with a fourth manual valve.

7. The emergency boron injection system according to claim 3, characterized in that: The first air inlet pipeline is also provided with a fifth manual valve, a sixth manual valve and a first control valve; The fifth manual valve and the first control valve are arranged between the bursting disc safety device and the primary circuit air cavity, and the sixth manual valve is arranged between the bursting disc safety device and the boron injection box.

8. The emergency boron injection system according to claim 1, characterized in that: Also includes: A liquid filling pipeline is connected to the boron injection box to inject a boron-containing solution into the boron injection box; The drain pipe is connected to the boron injection box and discharges the boron solution in the boron injection box to adjust the liquid level in the boron injection box.

9. The emergency boron injection system according to claim 1, characterized in that: Also includes: A gas filling pipeline is connected to the boron injection box to fill the boron injection box with gas; The exhaust pipeline is provided with a second control valve and a seventh manual valve for exhausting the gas in the boron injection box to adjust the pressure in the boron injection box.

10. The emergency boron injection system according to claim 1, characterized in that: It also includes a pressure relief pipeline, which is connected to the boron injection box and is provided with a safety valve. When the pressure in the boron injection box is too high, gas is discharged through the safety valve to prevent overpressure.

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