A passive flow adaptive injection box and nuclear power plant safety system

Abstract

The present invention discloses a passive flow adaptive injection tank, including an injection tank shell and a flow channel assembly. The injection tank shell is used to hold cooling water. A water outlet pipeline is provided at the bottom of the injection tank shell. The flow channel assembly is arranged in the inner shell of the injection tank, which includes a pipeline, a movable shaft, and a floating plug. The pipeline is erected in the injection tank shell. The bottom outlet of the pipeline is connected to the water outlet pipeline. A through hole is provided on the bottom wall of the pipeline. The floating plug is arranged in the injection tank shell and floats on the cooling water surface. The movable shaft is inserted in the pipeline and connected to the floating plug. The present invention also discloses a nuclear power plant safety system. The injection tank of the present invention can automatically adapt the injection flow to the demand, realize the functions of short-term rapid water injection and long-term slow water injection after a LOCA accident occurs, reduce the risk of failure of the active safety system, reduce the risk of power outage accidents in the entire nuclear power plant, extend the access time of the backup emergency power supply system, and improve the ability of the nuclear power plant to mitigate accidents and the overall safety of the nuclear power plant.

Description

Technical Field

[0001] The invention belongs to the field of nuclear technology, and in particular relates to a passive flow adaptive injection box and a nuclear power plant safety system. Background Art

[0002] After a large-breach loss of coolant accident (LOCA) occurs in a nuclear power plant, the core liquid level drops and the primary circuit pressure drops rapidly. When the pressure is lower than the pressure of the passive injection tank of the emergency core cooling system (ECCS), the boron-containing cooling water in the injection tank is injected into the lower head and lower chamber through the descending section of the pressure vessel. As the cooling water is continuously injected, the core liquid level gradually recovers. When all the water in the injection tank is injected, the coolant in the primary circuit will continue to flow out of the breach, causing the core liquid level to drop again. At this time, if there is no injection system to inject cooling water, the core will gradually be exposed, the core temperature will rise, the fuel rods will gradually melt and reposition, and finally the lower head may be melted through. Therefore, in addition to injecting water into the core for cooling in the short term after a LOCA accident, the core should also be cooled for a long time.

[0003] At present, the solutions adopted by nuclear power plants at home and abroad are generally: short-term water injection uses passive injection tanks, and long-term water injection uses other injection systems or containers, such as setting up low-pressure injection systems or passive injection containers with lower pressure. However, the low-pressure injection system may fail when the whole plant is powered off, and adding a passive injection container with lower pressure will make the overall system more complicated. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a passive flow adaptive injection box and a nuclear power plant safety system in view of the above-mentioned deficiencies in the prior art. The injection box can automatically adapt the injection flow to the demand, and realize the functions of short-term rapid water injection and long-term slow water injection after a LOCA accident occurs, thereby reducing the risk of failure of the active safety system, reducing the risk of power outages in the entire nuclear power plant, extending the access time of the backup emergency power supply system, and improving the reliability of the safety system of the nuclear power plant, thereby improving the ability of the nuclear power plant to mitigate accidents and the overall safety of the nuclear power plant.

[0005] The technical solution of the present invention to solve the above technical problems is:

[0006] According to one aspect of the present invention, there is provided a passive flow adaptive injection box, comprising an injection box housing and a flow channel assembly, wherein:

[0007] The injection tank shell is used to hold cooling water, and a water outlet pipeline is provided at the bottom of the injection tank shell. A check valve is provided on the water outlet pipeline, and the water outlet pipeline is used to inject the cooling water in the injection tank shell into the reactor core;

[0008] The flow channel assembly is arranged in the inner shell of the injection box, and includes a pipe, a movable shaft, and a floating plug. The pipe is erected in the injection box shell, and the bottom outlet of the pipe is connected to the water outlet pipeline, and a through hole is provided on the bottom wall of the pipe. The floating plug is arranged in the injection box shell and floats on the surface of the cooling water. It floats up and down with the change of the cooling water level and is used to block the top entrance of the pipe to control the opening and closing of the top entrance of the pipe. The movable shaft is inserted in the pipe and connected to the floating plug to ensure that the floating plug is blocked in the top entrance of the pipe when the cooling water drops to the top entrance of the pipe and below.

[0009] Preferably, a gas charging pipeline is provided on the top of the injection box shell for charging gas into the injection box shell so that a certain pressure exists in the injection box shell.

[0010] Preferably, the flow channel assembly further comprises a support frame, the support frame is fixed in the pipeline, a hole is opened on the support frame, and the movable shaft passes through the hole.

[0011] Preferably, the support frame is a cross structure, and the opening is arranged at the center of the cross structure.

[0012] Preferably, the top inlet of the pipeline is a tapered hole, and the outer shape of the floating plug is a cone that matches the tapered hole.

[0013] Preferably, the floating plug is a hollow structure.

[0014] Preferably, there are multiple through holes, and the multiple through holes are evenly distributed in a ring shape.

[0015] According to another aspect of the present invention, there is provided a nuclear power plant safety system, comprising a safety injection tank, wherein the safety injection tank adopts the above-mentioned passive flow adaptive safety injection tank.

[0016] Beneficial effects:

[0017] The passive flow adaptive injection box and nuclear power plant safety system of the present invention can automatically adapt the injection flow of cooling water to demand, and can realize both passive short-term rapid injection function and passive long-term slow injection function after accidents such as LOCA. Compared with traditional technologies, the failure risk of active safety systems (such as low-pressure injection systems) can be reduced, and the risk of being unable to open active valves in the event of a power outage in the entire nuclear power plant can be reduced. The access time of the backup emergency power supply system can be extended, so that the backup emergency power supply can be put into use later, and the reliability and success rate of the nuclear power plant safety system can be improved, thereby improving the nuclear power plant's ability to mitigate accidents and the overall safety of the nuclear power plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1This is a schematic diagram of the structure of a passive flow adaptive injection box according to an embodiment of the present invention;

[0019] Figure 2 is a schematic structural diagram of a flow channel assembly in an embodiment of the present invention;

[0020] Figure 3 A cross-sectional view showing the structure of a flow channel assembly in an embodiment of the present invention

[0021] Figure 4 It is a schematic diagram of a passive flow adaptive injection box in an embodiment of the present invention when the inlet at the top of the pipeline is opened;

[0022] Figure 5 It is a schematic diagram of the passive flow adaptive injection box in an embodiment of the present invention when the inlet at the top of the pipeline is closed.

[0023] In the figure: 1- injection box shell; 2- inflation pipeline; 3- water outlet pipeline; 4- pipeline; 5- floating plug; 6- moving shaft; 7- support frame; 8- through hole. DETAILED DESCRIPTION

[0024] 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 embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] Example 1

[0029] like Figure 1 As shown, this embodiment discloses a passive flow adaptive injection box, which includes an injection box housing 1 and a flow channel assembly, wherein:

[0030] The injection tank shell 1 is used to store cooling water. A water outlet pipeline 3 is provided at the bottom of the injection tank shell 1. A check valve (not shown in the figure) is provided on the water outlet pipeline. The check valve is used to control the on-off of the water outlet pipeline 3. The check valve is generally in a normally closed state, and the water outlet pipeline 3 is in a disconnected state. When the pressure of a primary circuit or a pressure vessel in a nuclear reactor is lower than the pressure in the injection tank shell 1, the check valve automatically opens under the action of the pressure difference, and the water outlet pipeline 3 is automatically connected. The water outlet pipeline 3 is used to be connected to the primary circuit or the pressure vessel in the nuclear reactor, so that the cooling water in the injection tank shell 1 is injected into the primary circuit or the pressure vessel after a LOCA accident or other breach accidents occur, thereby ensuring the safety of the reactor core.

[0031] The flow channel assembly is arranged in the injection box shell 1, which includes a pipe 4, a movable shaft 6, and a floating plug 5, wherein the pipe 4 is erected in the injection box shell 1, and the bottom outlet of the pipe 4 is connected to the water outlet pipeline 3. The floating plug 5 is arranged in the injection box shell 1 and floats on the cooling water surface. It floats up and down with the rise and fall of the cooling water level and is used to block the top inlet of the pipe 4 to control the opening and closing of the top inlet of the pipe 4. Specifically, when the cooling water level is above the top of the pipe 4, the top inlet of the pipe 4 is opened, and the cooling water can quickly enter the water outlet pipeline 3 through the top inlet of the pipe 4 and be injected into a circuit or a pressure vessel. When the cooling water level drops to the top inlet of the pipe 4 and below, the floating plug 5 is blocked in the top inlet of the pipe 4, and the top inlet of the pipe 4 is closed. The cooling water stops and quickly enters the water outlet line 3 through the top inlet of the pipe 4, thereby realizing the short-term rapid injection of cooling water function; the movable shaft 6 is inserted in the pipe 4 and connected to the floating plug 5, which can move up and down along the length direction of the pipe 4 with the floating plug 5, and is used to limit the floating position of the floating plug 5, so as to ensure that the floating plug 5 can be blocked in the top inlet of the pipe 4 when the cooling water drops to the top inlet of the pipe 4 and below; a through hole 8 is provided on the bottom wall of the pipe 4, and the through hole 8 can be used to pass cooling water into the water outlet line 3 for a long time, thereby realizing the long-term slow injection function. Specifically, the specific position, size, number, shape, and arrangement of the through hole 8 can be selected according to actual needs to ensure that the cooling water can be slowly injected into the cooling water at a flow rate that meets the requirements. In this embodiment, if Figure 2 As shown, the number of through holes 8 is preferably multiple, and the multiple through holes 8 are preferably evenly distributed in a ring shape, and the multiple through holes 8 can be divided into one row or multiple rows. The aperture size of the through holes 8 is preferably 1-10 cm, which is adjusted according to actual needs to ensure that cooling water can be slowly injected at a flow rate that meets the requirements. The position of the through holes 8 is preferably set at a height of 0.5-1.5m from the bottom of the injection box shell 1, and the shape of the through holes 8 is preferably circular.

[0032] In some embodiments, an air charging pipeline 2 is provided on the top of the injection tank shell 1, and the air charging pipeline 2 is used to charge gas (preferably nitrogen) into the injection tank shell 1 so that the injection tank shell 1 has a certain pressure (generally 4MPa-6MPa). In this way, in the event of a LOCA accident or other breach accidents, it can be ensured that the pressure in the injection tank shell 1 is greater than the pressure of a primary circuit or a pressure vessel, thereby passively injecting cooling water from the injection tank shell 1 into the primary circuit or the pressure vessel.

[0033] In some embodiments, the flow channel assembly further includes a support frame 7, which is fixed in the pipe 4, specifically, fixed on the inner wall of the pipe 4, and has an opening on the support frame 7, through which the movable shaft 6 passes. By providing the support frame 7, the position of the movable shaft 6 moving up and down along the length direction of the pipe 4 can be fixed, further ensuring that the floating plug 5 can block the top entrance of the pipe 4.

[0034] In some embodiments, Figure 2 As shown, the support frame 7 is preferably a cross structure, and the opening is arranged at the center of the cross structure. Figure 4 , Figure 5 As shown, the support frame 7 is preferably located at the upper end of the pipeline 4.

[0035] In some embodiments, the top entrance of the pipe 4 is preferably a tapered hole, that is, the inner wall of the top entrance of the pipe 4 has a certain inclination angle, and the shape of the floating plug 5 is a cone that matches the tapered hole so that the floating plug can seal and open the top entrance of the pipe 4.

[0036] In this embodiment, the inclination angle of the inner wall of the top inlet of the pipe 4 is preferably 10-30°.

[0037] In some embodiments, Figure 3 As shown, the floating plug 5 is a hollow structure, and the floating plug 5 is fixed on the top end of the moving shaft 6.

[0038] Taking the LOCA accident of a nuclear power plant as an example, the working process of the passive flow adaptive injection box of this embodiment is described in detail as follows:

[0039] Under normal working conditions, the injection tank shell 1 is filled with sufficient cooling water, and the water level of the cooling water is at least above the top inlet of the pipe 4, and a certain amount of nitrogen is introduced into the injection tank shell 1 through the charging pipeline 2 until the pressure in the injection tank shell 1 reaches 4.2MPa), and the floating plug 5 floats on the cooling water surface. At this time, the top inlet of the pipe 4 is in an open state (such as Figure 4 However, since the primary circuit of the nuclear power plant is intact under normal operating conditions, the pressure of the primary circuit (generally 15.5MPa) is higher than the pressure in the installation box shell, and the check valve on the outlet pipe 3 is in a closed state, the water in the injection box shell 1 will not be injected into the primary circuit.

[0040] After a LOCA accident occurs, the pressure of the primary circuit of the nuclear power plant drops rapidly. When the pressure drops to a level lower than the pressure in the injection tank shell 1 (e.g., 4.2 MPa and below), the check valve on the outlet pipe 3 automatically opens, allowing the cooling water in the injection tank shell 1 to quickly enter the outlet pipe 3 through the top inlet of the pipe 4. At the same time, the cooling water in the injection tank shell 1 also enters the outlet pipe 3 through the through hole 8 at the bottom end of the pipe 4, and then is injected into the primary circuit or the pressure vessel through the outlet pipe 3, thereby realizing passive short-term rapid water injection, until the cooling water level in the injection tank shell 1 drops to the top inlet of the pipe 4 and below, and the floating plug 5 is sealed in the top inlet of the pipe 4 (e.g., Figure 5 As shown), the rapid water injection is stopped. At this time, since the pressure in the injection tank shell 1 is still much greater than the pressure in the primary circuit, and the top inlet of the pipe 4 has been blocked by the floating plug 5, the cooling water in the injection tank shell 1 can only enter the water outlet pipeline 3 through the through hole 8 at the bottom end of the pipe 4, thereby realizing long-term slow water injection.

[0041] The passive flow adaptive injection box of this embodiment can automatically adapt the injection flow of cooling water to the demand. After an accident such as LOCA occurs, it can realize both passive short-term rapid injection function and passive long-term slow injection function. Compared with traditional technologies, it can reduce the failure risk of active safety systems (such as low-pressure injection systems), reduce the risk of being unable to open active valves in the event of a power outage in the entire nuclear power plant, extend the access time of the backup emergency power supply system, and allow the backup emergency power supply to be put into use later, thereby improving the reliability and success rate of the nuclear power plant safety system, and further improving the nuclear power plant's ability to mitigate accidents and the overall safety of the nuclear power plant.

[0042] Example 2

[0043] This embodiment discloses a nuclear power plant safety system, including a safety injection box, and the safety injection box adopts the passive flow adaptive safety injection box described in Example 1.

[0044] The nuclear power plant safety system of this embodiment adopts the non-passive flow adaptive injection box described in Example 1. Compared with the traditional technology, it not only has a simple process, but also can reduce the risk of human failure and the risk of being unable to open the active valve in the event of a power outage in the entire nuclear power plant, extend the access time of the backup emergency power supply system, so that the backup emergency power supply can be put into use later, improve reliability and success rate, thereby improving the nuclear power plant's ability to mitigate accidents and the overall safety of the nuclear power plant.

[0045] 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 flow adaptive injection box, It is characterized in that It comprises an injection box housing (1) and a flow channel assembly, The injection tank shell is used to hold cooling water, a water outlet pipeline (3) is provided at the bottom of the injection tank shell, a check valve is provided on the water outlet pipeline, and the water outlet pipeline is used to inject the cooling water in the injection tank shell into the reactor core; The flow channel assembly is arranged in the inner shell of the injection box, and comprises a pipeline (4), a movable shaft (6), and a floating plug (5). The pipeline is erected in the injection box housing, the bottom outlet of the pipeline is connected to the water outlet pipeline, and a through hole (8) is provided on the bottom wall of the pipeline. The floating plug is arranged in the injection box housing and floats on the cooling water surface, floating up and down with the change of the cooling water level, and is used to block the top entrance of the pipeline (4) to control the opening and closing of the top entrance of the pipeline (4). The movable shaft (6) is inserted into the pipeline (4) and connected to the floating plug (5), and can move up and down along the length direction of the pipeline as the floating plug floats up and down, limiting the floating position of the floating plug, and is used to ensure that the floating plug is sealed in the top entrance of the pipeline (4) when the cooling water drops to the top entrance of the pipeline (4) and below. The flow channel assembly further comprises a support frame (7), the support frame being fixed in the pipeline, the support frame having a hole, and the movable shaft passing through the hole.

2. The passive flow adaptive injection box according to claim 1, It is characterized in that A gas charging pipeline (2) is provided on the top of the injection box shell for charging gas into the injection box shell so that a certain pressure is formed in the injection box shell.

3. The passive flow adaptive injection box according to claim 1, It is characterized in that The support frame is a cross structure, and the opening is arranged at the center of the cross structure.

4. The passive flow adaptive injection box according to claim 1, It is characterized in that The top entrance of the pipeline is a tapered hole, and the outer shape of the floating plug is a cone that matches the tapered hole.

5. The passive flow adaptive injection box according to claim 1, It is characterized in that The floating plug is a hollow structure.

6. The passive flow adaptive injection box according to claim 1, It is characterized in that There are multiple through holes, and the multiple through holes are evenly distributed in a ring shape.

7. A nuclear power plant safety system, comprising an injection box, It is characterized in that The injection safety box adopts the passive flow adaptive injection safety box as described in any one of claims 1-6.

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