Advanced injection system and pressurized water reactor

Abstract

The application discloses an advanced safety injection system and a pressurized water reactor, and belongs to the nuclear power field. The advanced safety injection system comprises an integrated pressure water tank, the integrated pressure water tank comprises a CMT cavity and an ACC cavity which are separated by a conical wall extending vertically along an axis, the ACC cavity is arranged outside the CMT cavity, the cross-sectional area of the ACC cavity gradually decreases from top to bottom, and upper and lower through holes are arranged on the conical wall to communicate the CMT cavity and the ACC cavity. The ACC cavity is provided with pressure gas at the top; the CMT cavity is provided with a top inlet communicated with a reactor primary cooling system at the top end and is provided with an injection pipeline for injecting coolant into a reactor core at the bottom end. The advanced safety injection system has simple structure, can play the CMT and ACC functions under different accident conditions by using a single water tank, effectively reduces the manufacturing and maintenance costs, and improves the safety of the reactor.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power, specifically relating to an advanced safety injection system and a pressurized water reactor. Background Technology

[0002] The safety injection system (SEIS) is a crucial component of the safety system for commercial pressurized water reactors. In the event of a loss-of-coolant accident or other emergency, the SEIS injects cooling water into the reactor core to ensure its immersion and cooling, thereby mitigating the accident and controlling its consequences. Conventional SEIS systems consist of an Accident Controlled Injection Tank (ACC) and a Makeup Water Tank (CMT). When water injection is required, the CMT provides high-pressure injection, while the ACC provides medium-pressure injection. Currently, dual-tank systems are relatively complex, difficult to manufacture and maintain, and costly. Furthermore, the injection process cannot fully utilize boron-containing water. Therefore, providing a simpler and more reliable SEIS system is of significant importance for improving reactor safety and economic efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide an advanced safety injection system to improve safety and economy under reactor accident conditions. This invention also provides a pressurized water reactor.

[0004] According to one aspect of the present invention, an advanced safety injection system is provided for reactor core cooling under accident conditions, the system comprising an integrated pressure tank containing a coolant;

[0005] The integrated pressure tank includes a CMT chamber and an ACC chamber, which are separated by a conical wall, the axis of which extends vertically.

[0006] The ACC cavity surrounds the outside of the CMT cavity, and the cross-sectional area of ​​the ACC cavity gradually decreases from top to bottom;

[0007] The conical wall is provided with an upper through hole and a lower through hole so that the ACC cavity and the CMT cavity can be connected through the upper through hole and the lower through hole;

[0008] The top of the ACC chamber stores pressurized gas, and the storage area of ​​the pressurized gas is higher than the upper through hole;

[0009] The top of the CMT cavity is provided with a top inlet, which is connected to the primary coolant system of the reactor. The bottom of the CMT cavity is provided with an injection line for injecting the coolant into the reactor core.

[0010] Because the system uses an integrated pressure tank, the ACC and CMT are structurally integrated, which effectively simplifies the system structure, allows the ACC and CMT to share pipelines, reduces the number of valves and pipes, improves the reliability of the device, reduces manufacturing and maintenance costs, and facilitates safe injection in a passive manner.

[0011] Furthermore, in some embodiments, the CMT chamber is connected to the primary cooling system via a balancing pipeline to balance the pressure between the CMT chamber and the primary cooling system under normal operating conditions; a check valve is provided between the balancing pipeline and the CMT chamber to prevent the contents of the CMT chamber from flowing back into the balancing pipeline in case of an accident.

[0012] Furthermore, in some embodiments, an isolation valve is provided between the CMT cavity and the injection line, and the isolation valve opens when the pressure of the primary cooling system drops to a given threshold.

[0013] Furthermore, in some embodiments, the pressurized gas is configured as an inert gas, which may be nitrogen.

[0014] Furthermore, in some embodiments, the coolant is configured as a boron-containing aqueous solution.

[0015] Furthermore, in some embodiments, the top inlet is provided with a diffuser, which is used to reduce the fluid velocity entering the integrated pressure tank.

[0016] Furthermore, in some embodiments, the integrated pressure tank includes a hemispherical head and a cylindrical intermediate section, and is configured as a Class I seismic-resistant device with a safety rating of Class C.

[0017] Furthermore, in some embodiments, the upper through hole and the lower through hole are provided with opening adjustment devices.

[0018] The injection flow rate of ACC can be adjusted by changing the opening degree of the upper and lower through holes.

[0019] Furthermore, in some embodiments, the opening adjustment device includes a drive motor, an electric push rod, a guide rail, and a sliding baffle. The guide rail is disposed on the surface of the conical wall, the sliding baffle is slidably connected to the guide rail, and the electric push rod connects the drive motor and the sliding baffle to allow the drive motor to drive the sliding baffle to slide along the guide rail.

[0020] By setting up an opening adjustment device, the sump injection system can also actively inject coolant into the reactor core.

[0021] According to another aspect of the present invention, a pressurized water reactor is provided, comprising a core, a cooling system and a safety injection system, wherein the cooling system is connected to the core and provides cooling, and the safety injection system injects coolant into the core under accident conditions, wherein the safety injection system employs an advanced safety injection system provided in any of the foregoing embodiments.

[0022] Furthermore, in some embodiments, the advanced injection system is installed above the main pipe of the cooling system to allow the advanced injection system to perform passive injection in the event of an accident. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of an advanced safety injection system in one embodiment.

[0024] Figure 2 This is a schematic diagram of the upper through-hole structure in one embodiment;

[0025] Figure 3 This is a schematic diagram of the opening adjustment device in another embodiment.

[0026] Meaning of the reference numerals in the attached figures:

[0027] 1-Check valve; 2-Diffuser; 3-Integrated pressure vessel; 4-Conical wall; 5-CMT chamber; 6-ACC chamber; 7-Nitrogen; 8-Upper through hole; 9-Lower through hole; 10-Check valve; 11-Balancing line; 12-Injection line; 13-Opening adjustment device; 14-Sliding baffle; 15-Guide rail; 16-Electric push rod; 17-Motor; 18-Pin; 19-Locking hole; 20-Isolation valve; 21-Throttle orifice plate.

[0028] The purpose of the above-described drawings is to provide a detailed description of the present invention so that those skilled in the art can understand the technical concept of the invention, and is not intended to limit the invention. For the sake of brevity, the above-described drawings only schematically depict the structures related to the technical features of the present invention, and do not depict the complete structure and all details strictly according to actual scale. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0030] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment herein. The phrase appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive, independent, or alternative embodiments. Those skilled in the art will understand that the embodiments herein can be combined with other embodiments without causing structural conflicts.

[0031] In this description, unless otherwise explicitly specified and limited, the technical terms "installation," "connection," "joining," etc., should be interpreted broadly, for example, referring to movable connections, fixed connections, or integration. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0032] In this description, terms such as "upper," "lower," "left," "right," "lateral," "longitudinal," "height," "length," and "width," which indicate orientation or positional relationships, are intended to accurately describe the embodiments and simplify the description, rather than limiting the parts or structures involved to have a specific orientation, or to be installed or operated in a specific orientation, and should not be construed as limiting the embodiments in this document.

[0033] In this description, terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating relative importance or limiting the number, specific order, or primary / secondary relationship of the described technical features. In this description, "multiple" means at least two.

[0034] Pressurized water reactors (PWRs) consist of a core and a cooling system. Under normal operating conditions, the cooling system removes heat generated by the fuel assemblies in the core and transfers it to the steam generator for power output. However, during a loss-of-coolant (LOD) accident in a PWR, the cooling water in the cooling system is lost, causing the core water level to drop. Once the core is exposed, its heat transfer capacity decreases, making it prone to core meltdown and exacerbating the accident's consequences. Therefore, PWR cores require a safety injection system to replenish coolant in a timely manner during an accident, ensuring core reflooding. The effective injection flow rate and injection time of the safety injection system are crucial for mitigating the accident's consequences. For large-break LOD accidents, a large safety injection flow rate is required to quickly fill the lower core chamber. After the lower chamber is filled, the flow rate required for core reflooding is smaller. However, the commonly used safety injection systems, which include separate safety injection tanks (ACC) and replenishment tanks (CMT), often provide flow rates exceeding the required flow rate for the reflooding phase. This causes excessive boron-containing water to overflow from the break, resulting in waste of boron-containing water in the early stages of the accident and a lack of continuous replenishment capacity in the later stages. Furthermore, ACC and CMT each require independent supporting equipment, resulting in high manufacturing and maintenance costs and a large size of the safety injection system.

[0035] To address the aforementioned problems, one embodiment of the present invention provides an advanced safety injection system, such as... Figure 1 As shown.

[0036] The system stores the coolant in an integrated pressure vessel 3. In a preferred embodiment, the coolant is a boron-containing aqueous solution. In a further preferred embodiment, to improve the pressure resistance of the integrated pressure vessel 3, its overall structure is columnar, including hemispherical heads at the top and bottom ends and a cylindrical intermediate section in the middle. The integrated pressure vessel is designed as a Class I seismic-resistant device with a safety level of C.

[0037] The integrated pressure vessel 3 includes a CMT cavity 5 and an ACC cavity 6, which are separated by a conical wall 4. The axis of the conical wall 4 extends vertically, enclosing the CMT cavity 5, while the ACC cavity 6 is distributed around the outside of the CMT cavity 5. Due to the inclination angle of the conical wall 4, the cross-sectional area of ​​the ACC cavity 6 gradually decreases from top to bottom. The conical wall 4 is provided with an upper through-hole 8 and a lower through-hole 9, through which the CMT cavity 5 and the ACC cavity 6 are connected. Taking the upper through-hole 8 as an example... Figure 2 As shown, a set of upper through holes 8 are provided on the conical wall 4, and these upper through holes 8 are arranged at different heights in the vertical direction.

[0038] Under normal operating conditions, the CMT chamber 5 is filled with a boron-containing aqueous solution, while the top of the ACC chamber 6 stores a certain volume of pressurized gas. In a preferred embodiment, the pressurized gas is nitrogen 7. The gas chamber formed by nitrogen 7 is positioned above the upper through-hole 8.

[0039] The top of the CMT cavity 5 is provided with a top inlet, which connects to the balance line 11, which in turn connects to the reactor primary coolant system. In a preferred embodiment, a check valve 1 is provided at the top inlet. The check valve 1 ensures that fluid can only enter the CMT cavity 5 through the balance line 11, thus balancing the pressure inside the integrated pressure vessel 3 with the primary coolant system, while preventing fluid from flowing back from the CMT cavity 5 into the balance line 11. An injection line 12 is provided at the bottom of the CMT cavity 5 for injecting a boron-containing aqueous solution into the reactor core. In a preferred embodiment, an isolation valve 20 is provided between the CMT cavity 5 and the injection line. When the pressure of the primary coolant system drops below the set value of the isolation valve 20, the isolation valve 20 opens, and the CMT cavity 5 begins injecting water into the reactor core. A throttling orifice plate 21 is provided on the injection line 12. The resistance characteristics of the throttling orifice plate 21 and the size of the balance line 11 together determine the injection flow rate when the CMT cavity 5 begins injecting water. In a further preferred embodiment, a diffuser 2 is also provided at the top inlet. The diffuser 2 can reduce the flow rate of fluid entering the CMT cavity 5, thereby reducing the risk of water hammer when the CMT cavity 5 begins to inject water into the reactor core. A check valve 10 is provided on the injection line 12 to prevent the fluid in the injection line from being drawn back into the integrated pressure vessel 3.

[0040] The advanced safety injection system provided in the above embodiments, when applied to pressurized water reactors, can effectively simplify the structure of the safety injection system, improve reliability, and optimize safety performance under accident conditions. In a preferred embodiment, the installation position of the advanced safety injection system should ensure that the bottom height of the integrated pressure vessel 3 is higher than the main pipe of the cooling system, so that the advanced safety injection system can inject in a passive manner after an accident.

[0041] In one embodiment, after a small breach accident, primary coolant leaks out through the breach, causing the primary cooling system pressure to drop. When the pressure drops to the set value of isolation valve 20, after a preset time delay, isolation valve 20 opens, and the advanced safety injection system begins to replenish the cooling system with a boron-containing aqueous solution. In the initial stage of the accident, the core water level is higher than the cold section, and the main pipeline cold section is filled with water. Water is injected through CMT cavity 5 and relies on density difference to establish natural circulation, carrying away the core decay heat. At this time, the injection flow rate is relatively small.

[0042] As the primary coolant level drops due to coolant loss, a gas chamber appears in the cold section of the main pipeline. The upper part of CMT chamber 5 is essentially balanced with the pressure of the gas chamber. During this stage, the pressure is balanced by steam condensation and the advanced injection system, installed at a higher position, injects coolant passively, increasing the injection flow rate. The advanced injection system performs high-pressure injection. As coolant leaks from the rupture, the pressure continues to drop. When the system pressure falls below the pressure of nitrogen 7, the boron-containing aqueous solution in ACC chamber 6, driven by the pressure buildup of nitrogen 7, enters CMT chamber 5 through the upper through-hole 8 to replenish the coolant. Figure 2 Because the conical wall 4 has an inclined structure, the cross-sectional area of ​​the ACC cavity 6 decreases from top to bottom. During the process of water level drop in the ACC cavity 6, the pressure of nitrogen 7 can drop at a smaller rate, thereby maintaining the injection pressure from dropping too quickly and providing a higher injection flow rate to perform the medium-pressure safety injection function.

[0043] During the long-term cooling process in the later stages of the accident, the lower core chamber was already full, requiring only a small injection flow rate. At this point, the pressure of nitrogen 7 had dropped significantly, reducing the injection pressure; while the boron-containing aqueous solution in ACC chamber 6 continued to flow into CMT chamber 5 through the lower through-hole 9 and maintain the injection.

[0044] In another embodiment, after a large breach accident occurs, the primary coolant is rapidly lost through the breach. After the isolation valve 20 is opened, the pressure drops rapidly due to the large amount of coolant loss. The pressure in the cooling system drops rapidly to below the pressure of nitrogen 7. At this time, nitrogen 7 jointly drives the rapid high-flow-rate injection of boron-containing aqueous solution in ACC cavity 6 and CMT cavity 5, which quickly cools the reactor and causes the core water level to rise rapidly.

[0045] By rationally configuring the arrangement angle of the barrel baffle 4, as well as the number and height of the upper openings 8, the speed of nitrogen entering the CMT from the ACC and the amount of boron water entering the CMT from the ACC can be adjusted, thereby controlling the injection flow rate in different accident processes.

[0046] In some preferred embodiments, to further improve the ability to adjust the amount of water supplied from the ACC chamber 6 to the CMT chamber 5, an opening adjustment device 13 is also provided on the upper through hole 8 and the lower through hole 9. Taking the opening adjustment device 13 provided at the upper through hole 8 as an example, its structure is as follows: Figure 3 As shown. Specifically, the opening adjustment device 13 includes a sliding baffle 14, a guide rail 15, an electric push rod 16, and a motor 17. The guide rail 15 is fixedly mounted on the outer surface of the conical wall 4; the sliding baffle 14 is an arc-shaped plate that matches the curvature of the conical wall 4, slidably connected to the guide rail 15, and can slide along the guide rail 15. The upper through hole 8 specifically includes a through hole group composed of multiple small through holes. When the sliding baffle 14 is at one end of its sliding stroke, the upper through hole 8 is completely unobstructed; when the sliding baffle 14 slides to the other end of its sliding stroke, the upper through hole 8 is completely blocked. The flow rate of the upper through hole 8 can be adjusted by sliding the sliding baffle 14.

[0047] The motor 17 is fixedly mounted on the wall of the integrated pressure vessel and connected to the sliding baffle 14 via an electric push rod 16, allowing the sliding baffle 14 to slide back and forth along the guide rail 15 under the drive of the motor 17. Multiple locking holes 19 are further provided at different positions on the guide rail 15, and correspondingly, electrically controlled pins 18 are provided on the sliding baffle 14. When the baffle 14 moves to a designated position, the pins 18 can be inserted into the corresponding locking holes 19 to lock and fix the sliding baffle 14.

[0048] Under normal operating conditions, the sliding baffle 14 can completely close the upper through hole 8. Under emergency operating conditions, the opening of the through hole can be adjusted according to the required flow rate, so that the safety injection system can also inject in an active manner.

[0049] In one embodiment, the advanced safety injection system is configured as follows: Figure 3 The opening adjustment device is shown. Under initial normal operating conditions, the opening adjustment devices at the upper through hole 8 and the lower through hole 9 are both kept closed, and the nitrogen gas 7 accumulating pressure in the ACC chamber is 4.8 MPa.

[0050] After a small breach occurs, injection is first initiated in CMT chamber 5. When the primary cooling system pressure drops below 4.8 MPa, motor 17 drives sliding baffle 14 to move from the closed position, partially or fully opening the upper through-hole 8. This allows the boron-containing aqueous solution in ACC chamber 6 to flow into CMT chamber 5 through the upper through-hole 8, replenishing the injection water. When the boron-containing aqueous solution drops below the upper through-hole 8, nitrogen gas 7 in ACC chamber 6 diffuses into the top of CMT chamber 5, maintaining a certain pressure and injection flow rate within CMT chamber 5. In the later stages of the incident, if long-term injection is required, sliding baffle 14 at the lower through-hole 9 opens, allowing the boron-containing aqueous solution in ACC chamber 6 below the height of the upper through-hole 8 to continue flowing into CMT chamber 5, maintaining the injection.

[0051] After the large breach accident, the pressure dropped rapidly, and the opening adjustment devices 13 at the upper through hole 8 and the lower through hole 9 were fully opened. The ACC cavity 6 and the CMT cavity 5 together rapidly injected a high flow rate of boron-containing aqueous solution into the reactor core, so that the core was cooled rapidly.

[0052] By rationally configuring the arrangement angle of the barrel baffle 4, the number and height of the upper openings 8, and adjusting the height of the barrel-shaped slide plate 13 during the accident, the speed of nitrogen entering the CMT from the ACC and the amount of boron water entering the CMT from the ACC can be adjusted, thereby controlling the injection flow rate in different accident processes.

[0053] The advanced safety injection system provided in the above embodiments has a simple structure, low manufacturing and maintenance costs, and can effectively improve the safety performance of pressurized water reactors and enhance accident mitigation capabilities.

[0054] The purpose of the above embodiments is to provide a further detailed description of the present invention in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, optimization or equivalent substitution of the technical features involved, as well as combination of implementation methods in different embodiments without causing structural and principle conflicts, all fall within the protection scope of the present invention.

Claims

1. An advanced safety injection system for reactor core cooling under accident conditions, characterized in that, Includes an integrated pressure tank, which stores coolant; The integrated pressure tank includes a CMT chamber and an ACC chamber, which are separated by a conical wall, the axis of which extends vertically. The ACC cavity surrounds the outside of the CMT cavity, and the cross-sectional area of ​​the ACC cavity gradually decreases from top to bottom; The conical wall is provided with an upper through hole and a lower through hole so that the ACC cavity and the CMT cavity can be connected through the upper through hole and the lower through hole; The top of the ACC chamber stores pressurized inert gas, and the initial storage area of ​​the pressurized inert gas is higher than the upper through hole; The top of the CMT cavity is provided with a top inlet, which is connected to the primary coolant system of the reactor. The bottom of the CMT cavity is provided with an injection line for injecting the coolant into the reactor core.

2. The advanced injection system according to claim 1, characterized in that, The CMT chamber is connected to the primary cooling system via a balancing pipeline to balance the pressure between the CMT chamber and the primary cooling system under normal operating conditions. A check valve is installed between the balancing pipeline and the CMT chamber to prevent the contents of the CMT chamber from flowing back into the balancing pipeline in case of an accident.

3. The advanced injection system according to claim 1, characterized in that, An isolation valve is provided between the CMT chamber and the injection line. When the pressure of the primary cooling system drops to a given threshold, the isolation valve opens.

4. The advanced injection system according to claim 1, 2, or 3, characterized in that, The coolant is prepared as a boron-containing aqueous solution.

5. The advanced injection system according to claim 1, 2, or 3, characterized in that, The top inlet is equipped with a diffuser, which is used to reduce the fluid velocity entering the integrated pressure tank.

6. The advanced injection system according to claim 1, 2, or 3, characterized in that, The integrated pressure tank includes a hemispherical head and a cylindrical intermediate section, and is configured as a Class I seismic-resistant device with a safety level of C.

7. The advanced injection system according to claim 1, 2, or 3, characterized in that, The upper through hole and the lower through hole are equipped with opening adjustment devices.

8. The advanced injection system according to claim 7, characterized in that, The opening adjustment device includes a drive motor, an electric push rod, a guide rail, and a sliding baffle. The guide rail is disposed on the surface of the conical wall, and the sliding baffle is slidably connected to the guide rail. The electric push rod connects the drive motor and the sliding baffle to allow the drive motor to drive the sliding baffle to slide along the guide rail.

9. A pressurized water reactor, comprising a core, a cooling system, and a safety injection system, wherein the cooling system is connected to the core and provides cooling, and the safety injection system injects coolant into the core under accident conditions, characterized in that, The injection system employs the advanced injection system as described in any one of claims 1 to 8.

10. The pressurized water reactor according to claim 9, characterized in that, The advanced injection system is installed above the main pipeline of the cooling system to allow it to perform injections in case of an accident.

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