A passive medium pressure injection system and nuclear power plant system

Abstract

The present invention discloses a passive medium-pressure injection system, which includes an injection box, a first injection pipeline, a second injection pipeline, and a linkage valve, wherein the first injection pipeline and the second injection pipeline are both connected to the injection box and are used to inject cooling water in the injection box into the reactor coolant system of a nuclear power plant; the linkage valve has a first valve channel and a second valve channel, wherein the first valve channel is arranged on the first injection pipeline, the second valve channel is arranged on the second injection pipeline, and a control valve is arranged on the second injection pipeline, the first valve channel of the linkage valve is in a normally open state, and the second valve channel is in a normally closed state, when the nuclear power plant enters a low power and shutdown condition and the pressure of the reactor coolant system is reduced to a preset pressure threshold, the first valve channel of the linkage valve is switched to a closed state, and the second valve channel is switched to an open state. The present invention can ensure that the injection box is not started by mistake under low power and shutdown conditions, and can also ensure that the injection of cooling water to the injection box is completed after an accident condition.

Description

Technical Field

[0001] The invention belongs to the field of nuclear technology, and in particular relates to a passive medium-pressure injection system and a nuclear power plant system. Background Art

[0002] Generally, the medium-pressure injection system of a nuclear power plant includes a nitrogen pressurized injection tank. When an accident occurs in a nuclear power plant and the pressure in one circuit is lower than the pressure of the nitrogen in the injection tank, the boric acid solution in the injection tank will be automatically injected into the reactor coolant system.

[0003] However, after the nuclear power plant enters low power and shutdown conditions, the pressure of the reactor coolant system may also drop to a level lower than the pressure of the nitrogen in the injection tank, and the above-mentioned medium-pressure injection system is prone to false start-up. In order to prevent the false start-up of the medium-pressure injection system due to the pressure reduction of the reactor coolant system under low power and shutdown conditions, it is necessary to close the valve on the pipeline between the injection tank and the reactor coolant system when the pressure of the reactor coolant system reaches about 7MPa. However, under low power and shutdown conditions, if the valve is always closed, when an accident occurs in the nuclear power plant, the cooling water (boric acid solution) in the injection tank cannot be automatically injected into the reactor coolant system. For accidents such as large LOCA or induced serious accidents under low power and shutdown conditions, the rapid injection of cooling water from the injection tank is the key to quickly alleviate the loss of primary coolant, maintain the core water level, and delay the progress of the accident. The valve is always closed, which will affect the rapid injection of cooling water from the injection tank.

[0004] Therefore, nuclear power plants need a medium-pressure injection system that can start up without error under low power and shutdown conditions and complete the injection of cooling water into the injection tank after an accident condition. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a passive medium-pressure injection system and a nuclear power plant system in view of the above-mentioned deficiencies in the prior art. The passive medium-pressure injection system can ensure that it is not started incorrectly under low power and shutdown conditions, and can ensure that cooling water injection into the injection box is completed after an accident condition.

[0006] The technical solution of the present invention to solve the above technical problems is:

[0007] According to one aspect of the present invention, there is provided a passive medium-pressure safety injection system, comprising a safety injection box, a first injection pipeline, a second injection pipeline, and a linkage valve, wherein:

[0008] The first injection pipeline and the second injection pipeline are both connected to the safety injection tank, and are used to inject the cooling water in the safety injection tank into the reactor coolant system of the nuclear power plant;

[0009] The linkage valve comprises a first valve channel and a second valve channel, the first valve channel is arranged on the first injection pipeline, the second valve channel is arranged on the second injection pipeline, and a control valve is arranged on the second injection pipeline. The first valve channel of the linkage valve is in a normally open state, and the second valve channel is in a normally closed state. When the nuclear power plant enters a low power and shutdown condition and the pressure of the reactor coolant system drops to a preset pressure threshold, the first valve channel of the linkage valve is switched to a closed state, and the second valve channel is switched to an open state.

[0010] Preferably, the control valve is a pressure-sensitive bursting valve, and the setting value of the pressure-sensitive bursting valve is 0.12-0.24 MPa.

[0011] Preferably, a check valve is provided on the first injection pipeline, and the check valve is located downstream of the linkage valve.

[0012] Preferably, a shut-off valve is provided on the second injection pipeline, and the shut-off valve is located downstream of the control valve, and is used to disconnect the second injection pipeline in an emergency.

[0013] Preferably, the system further comprises a controller and a detector, wherein:

[0014] The detector is electrically connected to the controller and is used to detect the pressure of the reactor coolant system after the nuclear power plant enters a low power and shutdown condition, and transmit the detected pressure value to the controller;

[0015] The controller is electrically connected to the linkage valve, and the pressure threshold is preset in the controller. The controller is used to receive the pressure value and compare it with the pressure threshold. When the pressure value is equal to the pressure threshold, the linkage valve is controlled to close the first valve channel and open the second valve channel.

[0016] Preferably, the pressure threshold is 6.5-7.5 MPa.

[0017] Preferably, the safety injection box is provided with a safety valve for reducing the pressure of the safety injection box when the pressure in the safety injection box exceeds the design pressure.

[0018] Preferably, the safety valve is a pilot-operated safety valve group.

[0019] According to another aspect of the present invention, a nuclear power plant system is provided, including a reactor coolant system and also the above-mentioned passive medium-pressure safety injection system, wherein the first injection pipeline and the second injection pipeline in the passive medium-pressure safety injection system are both connected to the reactor coolant system.

[0020] Beneficial effects:

[0021] The passive medium-pressure injection system and nuclear power plant system of the present invention can ensure that the injection system is not mistakenly started under low power and shutdown conditions, and can ensure that the injection tank cooling water injection is completed after the accident condition, so that the nuclear power plant can automatically shut down the injection tank cooling water injection function under low power and shutdown conditions and can restore the injection tank cooling water injection function again under accident conditions, thereby improving the utilization rate of the injection tank cooling water, reducing the accident risk of the nuclear power plant, and improving the overall safety of the nuclear power plant. In addition, the present invention adopts a passive design, which can solve the problem of being unable to open the active valve that may be encountered in the event of a power outage in the entire plant, reduce the probability of human failure, improve the success rate of system operation, and extend the access time of the standby emergency power supply system, thereby improving the ability of the nuclear power plant to mitigate accidents, which is beneficial to reducing the frequency of core damage and the frequency of large-scale radioactive release in nuclear power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the operation of the passive medium pressure injection system under power conditions in an embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the operation of the passive medium-pressure injection system under low power and shutdown conditions in an embodiment of the present invention.

[0024] In the figure: 1- injection box; 2- first injection pipeline; 3- linkage valve; 4- check valve; 5- second injection pipeline; 6- control valve; 7- stop valve; 8- safety valve. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0026] In the description of the present invention, it should be noted that the term "upper" and the like to indicate orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience and simplification of description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0027] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0028] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connect", "set", "install", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, an indirect connection through an intermediate medium, or the internal communication of two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] Example 1

[0030] like Figure 1 As shown, this embodiment discloses a passive medium-pressure injection system, including an injection box 1, a first injection pipeline 2, a second injection pipeline 5, and a linkage valve 3, wherein:

[0031] The first injection pipeline 2 and the second injection pipeline 5 are both connected to the injection tank 1, and both are used to inject the cooling water (boric acid solution) in the injection tank 1 into the reactor coolant system of the nuclear power plant, wherein the first injection pipeline 2 is put into operation when an accident such as LOCA or a severe accident occurs when the nuclear power plant is in an operating condition other than low power and shutdown conditions and the pressure of the reactor coolant system is greater than a preset pressure threshold (such as 7MPa) (specifically, it may include power operating conditions, hot standby, hot shutdown, partially normal intermediate shutdown conditions, etc.), and the second injection pipeline 5 is put into operation when an accident such as LOCA or a severe accident occurs when the nuclear power plant is in a low power and shutdown condition;

[0032] The linkage valve 3 has a first valve channel and a second valve channel. The first valve channel is connected to the first injection pipeline 2, and the second valve channel is connected to the second injection pipeline 5, that is, a part of the linkage valve 3 is installed on the first injection pipeline 2, and the other part is installed on the second injection pipeline 5, and a control valve 6 is provided on the second injection pipeline 2. The first valve channel and the second valve channel of the linkage valve 3 are not opened or closed at the same time, that is: when the first valve channel is opened / closed, the second valve channel is closed / opened in linkage. Specifically, when the nuclear power plant is in the above-mentioned power condition, such as Figure 1As shown, the first valve channel of the linkage valve 3 is in a normally open state, and the second valve channel is in a normally closed state. At this time, if an accident such as LOCA occurs or a serious accident is induced, the pressure of the reactor coolant system will decrease. When the pressure decreases to a value lower than the pressure in the injection tank 1, the cooling water in the injection tank 1 is automatically and passively injected into the reactor coolant system through the first injection pipeline 2 under the action of the pressure difference; when the nuclear power plant enters a low power and shutdown condition and the pressure of the reactor coolant system decreases to a preset pressure threshold (such as 7MPa), as shown in FIG. Figure 2 As shown, the first valve channel of the linkage valve 3 is switched to a closed state, and the second valve channel is switched to an open state. At this time, since the control valve 6 is provided on the second injection pipeline 5, the second injection pipeline 5 has not been connected. Even if the pressure of the reactor coolant system is reduced to be lower than the pressure in the injection tank 1, the system of this embodiment will not be mistakenly started to cause the cooling water (boric acid solution) in the injection tank 1 to be mistakenly injected into the reactor coolant system. Moreover, under low power and shutdown conditions, if an accident such as LOCA occurs or a serious accident is induced, the second injection pipeline 5 can be connected by opening the control valve 6, so that the cooling water in the injection tank 1 is passively and automatically injected into the reactor coolant system through the second injection pipeline 5 under the action of the pressure difference, thereby completing the injection of cooling water into the injection tank under low power and shutdown conditions and without mistaken injection.

[0033] In this embodiment, the control valve 6 is preferably a pressure-sensitive bursting valve, and the setting value of the pressure-sensitive bursting valve is 0.11-0.24 MPa, preferably 0.13 MPa. When an accident such as LOCA occurs or a serious accident is induced, the pressure in the containment of the nuclear power plant will increase. When the pressure in the containment is greater than or equal to the setting value of the pressure-sensitive bursting valve, the sleeve shear cover of the pressure-sensitive bursting valve automatically opens, and the second injection pipeline 5 is connected.

[0034] In this embodiment, the preset pressure threshold may be 6.5-7.5 MPa, preferably 7 MPa.

[0035] In some embodiments, a check valve 4 is provided on the first injection pipeline 2, and the check valve 4 is located downstream of the linkage valve 3. The check valve 4 is passively opened according to the difference between the pressure in the injection tank 1 and the pressure of the reactor coolant system. Specifically, the check valve 4 is opened when the pressure of the reactor coolant system is lower than the pressure in the injection tank 1 (such as 4.2MPa).

[0036] In some embodiments, a shut-off valve 7 is provided on the second injection pipeline 5 . The shut-off valve 7 is located downstream of the control valve 6 and is used to disconnect the second injection pipeline 5 in any emergency situation.

[0037] In this embodiment, the stop valve is preferably an electric stop valve.

[0038] In some embodiments, the system further includes a controller and a detector (not shown in the figure).

[0039] Specifically, the detector is electrically connected to the controller, and is used to detect the pressure of the reactor coolant system after the nuclear power plant enters the low power and shutdown conditions, and transmits the detected pressure value to the controller. The controller is electrically connected to the linkage valve 3, and the pressure threshold is preset in the controller. The controller is used to receive the pressure value and compare it with the pressure threshold. When the pressure value is equal to the pressure threshold, the linkage valve 3 is automatically controlled to close the first valve channel and open the second valve channel, that is, the first valve channel of the linkage valve 3 is switched from the normally open state to the closed state, and the second valve channel is switched from the normally closed state to the open state.

[0040] In some embodiments, the safety injection tank 1 is provided with a safety valve 8 for reducing the pressure of the safety injection tank 1 when the pressure in the safety injection tank 1 exceeds the design pressure, so as to control the pressure in the safety injection tank 1 to be stable within the design value.

[0041] In this embodiment, the safety valve 8 is preferably a pilot-operated safety valve group.

[0042] The working process of the passive medium pressure injection system of this embodiment is described in detail below, as follows:

[0043] When the nuclear power plant is in an operating condition other than low power and shutdown conditions and the pressure of the reactor coolant system is greater than a preset pressure threshold (such as 7MPa), the first valve channel of the linkage valve 3 is in a normally open state and the second valve channel is in a normally closed state. At this time, if an accident such as LOCA occurs or a serious accident is induced, when the pressure of the reactor coolant system drops to below the pressure in the injection tank 1, the check valve 4 automatically opens, and the cooling water in the injection tank 1 is automatically injected into the reactor coolant system through the first injection pipeline 2 under the action of the pressure difference.

[0044] When the nuclear power plant enters low power and shutdown conditions and the pressure of the reactor coolant system drops to less than or equal to the preset pressure threshold (such as 7MPa), the first valve channel of the linkage valve 3 is switched from a normally open state to a closed state, and the second valve channel is switched from a normally closed state to an open state. At this time, the first injection pipeline 2 and the second injection pipeline 5 are not connected, thereby avoiding false start-up. Under this premise, if an accident such as LOCA occurs or a serious accident is induced, when the pressure in the containment reaches the set value of the pressure-sensing burst valve (i.e., the control valve), it will automatically open, thereby connecting the second injection pipeline 5. The cooling water in the injection tank 1 is automatically injected into the reactor coolant system through the second injection pipeline 5 under the action of the pressure difference, thereby completing the injection of cooling water into the injection tank under low power and shutdown conditions and without false injection.

[0045] The passive medium-pressure injection system of this embodiment can ensure that it is not started incorrectly under low power and shutdown conditions, and can ensure that the injection tank cooling water is injected after the accident condition, so that the nuclear power plant can automatically shut down the injection tank cooling water injection function under low power and shutdown conditions and can restore the injection tank cooling water injection function under accident conditions, thereby improving the utilization rate of the injection tank cooling water, reducing the accident risk of the nuclear power plant, and improving the overall safety of the nuclear power plant. In addition, the present invention adopts a passive design, which can solve the problem of being unable to open the active valve in the event of a power outage in the whole plant, reduce the probability of human failure, improve the success rate of system operation, and extend the access time of the standby emergency power supply system, thereby improving the ability of the nuclear power plant to mitigate accidents, which is beneficial to reducing the frequency of core damage and the frequency of large-scale radioactive release in nuclear power plants.

[0046] Example 2

[0047] This embodiment discloses a nuclear power plant system, including a reactor coolant system, and also includes the passive medium-pressure safety injection system described in Example 1, wherein the first injection pipeline 2 and the second injection pipeline 5 in the passive medium-pressure safety injection system are both connected to the reactor coolant system.

[0048] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A passive medium pressure injection system, characterized in that: It comprises an injection box (1), a first injection pipeline (2), a second injection pipeline (5), and a linkage valve (3). The first injection pipeline and the second injection pipeline are both connected to the safety injection tank, and are used to inject the cooling water in the safety injection tank into the reactor coolant system of the nuclear power plant; The linkage valve comprises a first valve channel and a second valve channel, wherein the first valve channel is arranged on the first injection pipeline, the second valve channel is arranged on the second injection pipeline, and a control valve (6) is arranged on the second injection pipeline. When the nuclear power plant is in a condition other than low power and shutdown conditions and the pressure of the reactor coolant system is greater than the preset pressure threshold, the first valve channel of the linkage valve is normally open and the second valve channel is normally closed. When the nuclear power plant enters a low power and shutdown condition and the pressure of the reactor coolant system drops to a preset pressure threshold, the first valve channel of the linkage valve is switched to a closed state and the second valve channel is switched to an open state. At this time, the first injection pipeline and the second injection pipeline are not connected to avoid false start-up. Under this premise, the control valve is used to automatically open when the pressure in the containment reaches the set value of the control valve (6) when a LOCA accident occurs or a serious accident is induced, so that the second injection pipeline is connected. The cooling water in the injection tank is automatically injected into the reactor coolant system through the second injection pipeline under the action of the pressure difference, so as to complete the injection of cooling water into the injection tank under low power and shutdown conditions and without false injection.

2. The passive medium pressure injection system according to claim 1, characterized in that: The control valve is a pressure-sensitive bursting valve, and the setting value of the pressure-sensitive bursting valve is 0.11-0.24 MPa.

3. The passive medium pressure injection system according to claim 1, characterized in that: A check valve (4) is provided on the first injection pipeline, and the check valve is located downstream of the linkage valve.

4. The passive medium pressure injection system according to claim 1, characterized in that: The second injection pipeline is provided with a stop valve (7), which is located downstream of the control valve and is used to disconnect the second injection pipeline in an emergency.

5. The passive medium pressure injection system according to any one of claims 1 to 4, characterized in that: It also includes controllers, detectors, The detector is electrically connected to the controller and is used to detect the pressure of the reactor coolant system after the nuclear power plant enters a low power and shutdown condition, and transmit the detected pressure value to the controller; The controller is electrically connected to the linkage valve, and the pressure threshold is preset in the controller. The controller is used to receive the pressure value and compare it with the pressure threshold. When the pressure value is equal to the pressure threshold, the linkage valve is controlled to close the first valve channel and open the second valve channel.

6. The passive medium pressure injection system according to claim 5, characterized in that: The pressure threshold is 6.5-7.5 MPa.

7. The passive medium pressure injection system according to claim 5, characterized in that: The injection box is provided with a safety valve (8) for reducing the pressure of the injection box when the pressure in the injection box exceeds the design pressure.

8. The passive medium pressure injection system according to claim 7, characterized in that: The safety valve is a pilot-operated safety valve group.

9. A nuclear power plant system, comprising a reactor coolant system, characterized in that: It also includes the passive medium pressure injection system according to any one of claims 1 to 8, The first injection pipeline (2) and the second injection pipeline (5) in the passive medium-pressure injection system are both connected to the reactor coolant system.

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