Emergency core cooling system

Abstract

An emergency core cooling system, comprising a first line (1) and a second line (2), wherein the first line (1) comprises a first safety injection pump (101), a second safety injection pump (102), a f

Description

TECHNICAL FIELD

[0001] The present invention belongs to the technical field of nuclear power, and particularly relates to an emergency core cooling system. BACKGROUND

[0002] Loss of coolant accident (LOCA) is a typical design basis accident condition that needs to be considered m the design of nuclear power plants. After a LOCA accident, one of the main objectives of accident handling is to achieve emergency core cooling. If emergency cooling water cannot be supplied to the reactor core in a timely manner, the reactor will be unable to effectively cool the core due to the loss of emergency coolant, which will eventually lead to damage to the core fuel cladding and uncontrolled release of radioactive materials. Therefore, in order to cope with the LOCA accident condition, pressurized water reactor nuclear power plants will set up an emergency core cooling system to perform emergency core injection after the LOCA accident.

[0003] The emergency core cooling system is one of the important safety systems in a nuclear power plant. Its setup must meet the requirements of independence and satisfy the single failure criterion. The independence requirement requires that appropriate means such as physical isolation, electrical isolation, functional independence, and communication (data transmission) independence be used to prevent mutual interference between systems or between redundant components of the same system. The single failure criterion requires that the emergency core cooling system be in the most unfavorable permissible configuration state under a LOCA accident, that is, the failure of any equipment in the emergency core cooling system would render the function unavailable.

[0004] In the existing design of emergency core cooling systems for nuclear power plants, the independence and single fault criteria requirements of the system are generally achieved through redundancy configuration and physical isolation. Redundancy configuration means configuring "N+l" trains of emergency core cooling systems. "N" indicates the number of trains that take into account LOCA initiation events, single faults, and failures of the emergency core cooling system caused by online system maintenance. "1" indicates that one train remains valid. The independence design is a further design optimization based on the redundancy design, that is, through appropriate means such as physical isolation, electrical isolation, functional independence, and communication (data transmission) independence, mutual interference between trains of the emergency core cooling system is prevented. For example, as shown in FIG. 2, the prior art one constructs an emergency core cooling system, which consists of three systems: high head safety injection, medium head safety injection, and low head safety injection. The high head safety injection system is equipped with three high head safety injection pumps (HHSI), the medium head safety injection system is mainly equipped with three medium head accumulator (ACC), and the low head safety injection system is equipped with two low head safety injection pumps (LHSI). For example, as shown in FIG. 3, the emergency core cooling system constructed by the prior art two includes three trains of independent and redundant systems. Each system consists of a low head safety injection (LHSI), a medium head safety injection (MHSI), and an accumulator subsystem. For example, as shown in FIG. 4, an emergency core cooling system constructed in the prior art three includes two trains of independent HHSI pumps, two trams of ACC pumps, and two trains of LHSI pumps, which inject water into the core through two trains of DVI pumps. For example, as shown in FIG. 5, an emergency core cooling system constructed in the prior art four consists of four strictly physically separated independent pipelines, each train corresponding to a loop of the reactor coolant system. Each train is located in a separate safety zone, which includes an accumulator, a MHSI pump and a LHSI pump (which also serves as a residual heat removal pump).

[0005] Among them, the prior art one does not meet the requirements for independence between safety systems. The three HHSI pumps and two LHSI are connected in parallel to the RCP system by header. The header scheme causes interconnection between the trains of the ECCS system. Under the LOCA accident condition, part of the emergency coolant m the effective injection train flows out through the break, affecting the effective flow rate injected into the emergency core. Both prior art two and prior art four have high redundancy, increasing the number of trains in the system's own configuration. Correspondingly, the number of trains in supporting auxiliary systems (such as emergency diesel generators, cold chain systems, and HVAC systems) also needs to be set accordingly, resulting in an increase in the scale of the safety plant and room for optimization in terms of economic efficiency. The prior art three cannot meet the single failure criterion. The system configuration scheme only configures one HHSI and one LHSI per train. Considering the DVI pipeline LOCA between the check valve and RPV, according to the single failure criterion, if the failure of another train of HHSI and LHSI is considered, the emergency core injection function will be lost and it will be unable to cope with the DVI pipeline LOCA. SUMMARY OF THE INVENTION

[0006] In view of the defects in the prior art, the technical problem to be solved by the present invention is to provide an improved emergency core cooling system.

[0007] The technical solution adopted by the present invention to solve the above technical problem is to provide an emergency core cooling system, including:

[0008] A first pipeline, including a first safety injection pump, a second safety injection pump, a first emergency core water injection pipe, and a first connecting pipe for supplying emergency coolant to a second interface of the reactor pressure vessel; the input end of the first emergency core water injection pipe is connected to an in-containment refueling water storage tank, and the output end is connected to a first interface of the reactor pressure vessel; the first safety injection pump is arranged on the first emergency core water injection pipe; the input end of the first connecting pipe is connected to the in-containment refueling water storage tank, and the output end is connected to the second interface; the second safety injection pump is arranged on the first connecting pipe; and

[0009] A second pipeline, including a third safety injection pump, a fourth safety injection pump, a second emergency core water injection pipe, and a second connecting pipe for supplying emergency coolant to the first interface; the input end of the second emergency core water injection pipe is connected to the in-containment refueling water storage tank, and the output end is connected to the second interface; the third safety injection pump is arranged on the second emergency core water injection pipe; the input end of the second connecting pipe is connected to the in-containment refueling water storage tank, and the output end is connected to the first interface; the fourth safety injection pump is arranged on the second connecting pipe.

[0010] In some embodiments, the first pipeline further includes a first accumulator, the first accumulator is disposed downstream of the first safety injection pump, and the second pipeline further includes a second accumulator, the second accumulator is disposed downstream of the third safety injection pump.

[0011] In some embodiments, the first pipeline further includes a first safety injection heat exchanger, the second pipeline further includes a second safety injection heat exchanger, the first safety injection heat exchanger is disposed downstream of the first safety injection pump, and the second safety injection heat exchanger is disposed downstream of the third safety injection pump.

[0012] The output end of the first connecting pipe is connected to the pipe between the second safety injection heat exchanger and the third safety injection pump, and the output end of the second connecting pipe is connected to the pipe between the first safety injection heat exchanger and the first safety injection pump.

[0013] In some embodiments, the first emergency core water injection pipe includes a first cold leg pipe section located outside the containment boundary and a first output pipe section located inside the containment boundary; the two ends of the first cold leg pipe section are respectively connected to the in-containment refueling water storage tank and the input end of the first output pipe section; the output end of the first output pipe section is connected to the first interface, the first safety injection pump is disposed on the first cold leg pipe section, the first accumulator is connected to the first output pipe section.

[0014] The second pipeline includes a second cold leg pipe section located outside the containment boundary and a second output pipe section located inside the containment boundary; the two ends of the second cold leg pipe section are respectively connected to the in-containment refueling water storage tank and the input end of the second output pipe section; the output end of the second output pipe section is connected to the second interface, the third safety injection pump is disposed on the second cold leg pipe section, and the second accumulator is connected to the second output pipe section.

[0015] In some embodiments, the first pipeline further includes a first hot leg pipe, the input end of the first hot leg pipe is connected to the output end of the first cold leg pipe section, and the output end of the first hot leg pipe is communicated with one of hot legs of the reactor loop.

[0016] The second pipeline further includes a second hot leg pipe, the input end of which is connected to the output end of the second cold leg pipe section, and the output end of the second hot leg pipe is communicated with another hot leg of the reactor loop.

[0017] In some embodiments, the first pipeline further includes a third connecting pipe whose two ends are respectively connected to the first accumulator and the first output pipe section, and the third connecting pipe is provided with a check valve and an electrically controlled valve; the second pipeline further includes a fourth connecting pipe whose two ends are respectively connected to the second accumulator and the second output pipe section, and the fourth connecting pipe is provided with a check valve and an electrically controlled valve.

[0018] In some embodiments, the first pipeline further includes a first water intake pipe section located within the containment boundary, the two ends of which are respectively connected to the in-containment refueling water storage tank and the input end of the first cold leg pipe section.

[0019] The second pipeline further includes a second water intake pipe section located within the containment boundary, the two ends of which are respectively connected to the in-containment refueling water storage tank and the input end of the second cold leg pipe section.

[0020] In some embodiments, the input end of the first connecting pipe is connected to the output end of the first water intake pipe section, and is connected to the in-containment refueling water storage tank through the first water intake pipe section.

[0021] The input end of the second connecting pipe is connected to the output end of the second water intake pipe section, and is connected to the in-containment refueling water storage tank through the second water intake pipe section.

[0022] In some embodiments, a sump screen is provided between the first water intake pipe section and the second water intake pipe section and the in-containment refueling water storage tank.

[0023] In some embodiments, both ends of the first cold leg pipe section and the second cold leg pipe section are provided with electrically controlled valves, and the first output pipe section and the second output pipe section are each provided with three check valves.

[0024] In some embodiments, the first hot leg pipe and the second hot leg pipe are partially located outside the containment boundary and partially located inside the containment boundary, and are respectively provided with an electrically controlled valve and three check valves; the electrically controlled valves on the first hot leg pipe and the second hot leg pipe are all located outside the containment boundary, and the three check valves on the first hot leg pipe and the second hot leg pipe are all located inside the containment boundary.

[0025] In some embodiments, the output ends of the first safety injection pump, the second safety injection pump, the third safety injection pump and the fourth safety injection pump are all equipped with check valves.

[0026] In some embodiments, the first safety injection pump, the second safety injection pump, the third safety injection pump and the fourth safety injection pump are all medium head safety injection pumps.

[0027] Implementing the embodiments of the present invention provides at least the following beneficial effects:

[0028] The invention includes two pipelines, with two safety injection pumps connected in parallel on each pipeline. One of the two safety injection pumps is connected to the other pipeline, allowing all four safety injection pumps to independently pump emergency coolant into the reactor pressure vessel through the DVI pipeline. For a large-break LOCA, at least two safety injection pumps can simultaneously inject coolant into the core. For a small-break LOCA with a break diameter smaller than the inner diameter of the DVI pipeline, at least one safety injection pump injects coolant into the core. This meets the requirements for the amount of coolant needed for the reactor under different accident conditions and eliminates the need to switch safety injection pumps during the injection process, which effectively shortens the emergency core water injection process after an accident, reduces operational steps, avoids the possibility of operational errors, and improves the reliability of the emergency core injection function.

[0029] Meanwhile, in response to various reactor coolant system pipeline LOCA, and considering the worst-case scenario of a single failure, there are corresponding safety injection pumps to pump emergency coolant into the reactor, reducing the probability of core damage from LOCA. At the same time, the system structure is simple, and the HVAC, electrical, and instrumentation and control systems corresponding to the two independent safety injection trains are also fewer, reasonably reducing redundancy, reducing the number of safety injection pumps and supporting systems, as well as the scale of the plant to accommodate these systems and equipment, greatly reducing the system construction cost, and facilitating a balanced design of system safety and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below in conjunction with accompanying drawings and embodiments. In the drawings,

[0031] FIG. 1 is a structural schematic diagram of an emergency core cooling system according to an embodiment of the present invention;

[0032] FIG. 2 is a structural schematic diagram of the emergency core cooling system of the prior art one;

[0033] FIG. 3 is a structural schematic diagram of the emergency core cooling system of the prior art two;

[0034] FIG. 4 is a structural schematic diagram of the emergency core cooling system of the prior art three; and

[0035] FIG. 5 is a structural schematic diagram of the emergency core cooling system of the prior art four. EMBODIMENTS FOR IMPLEMENTING THE INVENTION

[0036] To provide a clearer understanding of the technical features, objectives, and effects of this application, the specific embodiments of this application will now be described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientation or positional relationship indicated by terms such as "front", "back", "up", "down", "left", "right", "longitudinal", "transverse", "vertical", "horizontal", "top", "bottom", "inner", "outer", "head", and "tail" are based on the orientation or positional relationship shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing this technical solution and do not indicate that the device or component referred to must have a specific orientation. Therefore, they should not be construed as limitations on this application.

[0037] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "install", "connect", "link", "fix", and "set" should be interpreted broadly. For example, it can refer to fixed connections, detachable connections, or integral connections; it can refer to mechanical connections or electrical connections; it can refer to direct connections or indirect connections through an intermediate medium and it can refer to the internal connection of two components or the interaction between two components. When an element is referred to as being "above" or "below" another element, the element is able to be located "directly" or "indirectly" on the other element, or there may be one or more intermediary elements. The terms "first", "second", "third", etc., are used only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first", "second", "third", etc., may explicitly or implicitly include one or more of that feature. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0038] In the following description, specific details such as particular system architectures and technologies are set forth for illustrative purposes and not for limiting purposes, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted to avoid unnecessary detail from obscuring the description of this application.

[0039] FIG. 1 shows an emergency core cooling system constructed according to the present invention, used to inject emergency coolant (cooling water in this embodiment) into the reactor in a timely manner during a loss of coolant accident (LOCA) caused by a reactor break, to avoid damage to the core fuel cladding and uncontrolled release of radioactive materials. The emergency core cooling system includes a first pipeline 1 and a second pipeline 2.

[0040] The first pipeline 1 includes a first safety injection pump 101, a second safety injection pump 102, a first emergency core water injection pipe, and a first connecting pipe 15. The second pipeline 2 includes a third safety injection pump 201, a fourth safety injection pump 202, a second emergency core water injection pipe, and a second connecting pipe 25. The input ends of both the first emergency core water injection pipe and the second emergency core water injection pipe are connected to the in-contamment refueling water storage tank (IRWST) 001. The water in the in-containment refueling water storage tank 001 is used as an emergency coolant and injected into the core in the event of an emergency coolant loss accident. The output ends of the first emergency core water injection pipe and the second emergency core water injection pipe are respectively connected to the reactor pressure vessel to inject emergency coolant into the reactor pressure vessel. The arrangement of the first emergency core water injection pipe and the second emergency core water injection pipe allows both to carry out water injection operations independently, thus meeting the independence requirements. Specifically, the output end of the first emergency core water injection pipe is connected to the first interface 109 of the reactor pressure vessel, and the output end of the second emergency core water injection pipe is connected to the second interface 209 of the reactor pressure vessel.

[0041] The first safety injection pump 101 is arranged on the first emergency core water injection pipe and is used to pump cooling water from the in-containment refueling water storage tank 001 to the first interface 109 through the first emergency core water injection pipe. The input end of the first connecting pipe 15 is connected to the in-containment refueling water storage tank 001, and the output end is connected to the second interface 209. The second safety injection pump 102 is arranged on the first connecting pipe 15 and is used to pump emergency coolant to the second interface 209 using the power of the first pipeline 1. This prevents the emergency core cooling system from being unable to inject emergency coolant into the reactor when, for example, the second pipeline 2 loses its power source and the first emergency core water injection pipe breaks.

[0042] The third safety injection pump 201 is arranged on the second emergency core water injection pipe and is used to pump cooling water from the in-containment refueling water storage tank 001 to the second interface 209 through the second emergency core water injection pipe. The input end of the second connecting pipe 25 is connected to the in-containment refueling water storage tank 001, and the output end is connected to the first interface 109. The fourth safety injection pump 202 is arranged on the second connecting pipe 25 and is used to pump emergency coolant to the first interface 109 using the power of the second pipeline 2. This prevents the emergency core cooling system from being unable to inject emergency coolant into the reactor when, for example, the first pipeline 1 loses its power source and the second emergency core water injection pipe breaks.

[0043] This invention, by arranging two safety injection pumps in parallel on each pipeline, ensures that even in the event of a large-break LOCA in the main pipeline of the reactor coolant system, even under the most unfavorable condition according to the single failure criterion, one pipeline fails (for example, the second pipeline 2 loses its power source, and the third safety injection pump 201 and the fourth safety injection pump 202 cannot operate), the two safety injection pumps (the first safety injection pump 101 and the second safety injection pump 102) on one pipeline (the first pipeline 1) can simultaneously inject water into the reactor core, ensuring that the water injection flow rate meets the water demand in the event of a large-break LOCA in the main pipeline.

[0044] When a small-break LOCA with a break diameter smaller than the inner diameter of the DVI pipeline occurs (such as a LOCA in the second pipeline 2), the pressure drop is relatively slow because the break size of the pipeline is smaller than that of the main pipeline. At the same time, the amount of water that needs to be added is small. In this case, it is only necessary to ensure that one injection pump is effective to compensate for the loss of the primary circuit coolant in the accident condition. Therefore, under this premise, even according to the single failure criterion, in the most unfavorable condition, if one of the injection pumps (such as the second safety injection pump 102) on another pipeline (the first pipeline 1) without a break fails and cannot operate, the remaining injection pump (the first safety injection pump 101) can still perform water injection operation independently.

[0045] In other words, the application employs two pipelines, each equipped with two parallel safety injection pumps, ensuring that under any accident conditions, only one startup is required to handle all accident conditions. There is no need to switch between different safety injection pumps for different accident conditions. The operation of starting the safety injection pumps once can complete the accident handling and response. This avoids the risk of safety injection flow interruption caused by the safety injection pump switching process, reduces operation steps, and avoids the possibility of operation errors.

[0046] Meanwhile, the emergency core injection system constructed in the application does not require different types of safety injection pumps (such as high head, medium head, and low head safety injection pumps). Only one type of safety injection pump is needed to handle all accident conditions, which reduces the number of safety injection pumps and the arrangement of other supporting systems (such as HVAC, electrical, instrumentation and control, plant, power source equipment, etc.). The system configuration is simpler, the cost is lower, and the economy is higher. In this embodiment, all equipment in the first pipeline 1 shares a single train of emergency diesel generator for power supply. All equipment in the second pipeline 2 also shares a single train of emergency diesel generator for power supply to ensure the independence between the two pipelines. It should be understood that "loss of power source" in this embodiment means that the emergency diesel generator shared by the pipeline is unable to supply power to the pipeline.

[0047] It should be understood that the first pipeline 1 and the second pipeline 2 can be directly connected to the descending section of the reactor pressure vessel through the first interface 109 and the second interface 209, respectively, so that the emergency coolant can be pumped to the descending section of the reactor pressure vessel, thereby achieving the effect of rapid emergency injection.

[0048] In some embodiments, the first safety injection pump 101, the second safety injection pump 102, the third safety injection pump 201, and the fourth safety injection pump 202 are all medium head safety injection pumps. The selection of this medium head safety injection pump, along with the configuration of two pipelines and two safety injection pumps per pipeline, enables this emergency core cooling system to cope with various types of accidents, including large break and small break. In the event of a large break, four safety injection pumps can be activated simultaneously to increase the overall flow rate. In cases of a minor break, where a large flow rate is not required, only one or two safety injection pumps may be used.

[0049] It should be understood that existing safety injection pumps are divided into high head safety injection pumps, medium head safety injection pumps, and low head safety injection pumps. The higher the applicable pressure of the safety injection pump, the lower its pumping flow rate. However, in a large-break LOCA, the primary circuit back pressure drops rapidly due to the occurrence of a large break, which can meet the startup requirements of the medium head safety injection pump. In this case, multiple safety injection pumps need to be connected in parallel to meet the flow rate requirements. In a small-break LOCA, the back pressure drops slowly due to the small break size. Initially, it may not meet the startup requirements of the medium head safety injection pump (i.e , reach its head range). In this case, the safety injection pump can be used in conjunction with the medium-pressure rapid cooling valve on the secondary side of the steam generator. The reactor is rapidly depressurize by the medium-pressure rapid cooling valve, allowing the primary circuit back pressure to drop quickly to meet the startup requirements of the medium head safety injection pump.

[0050] In some embodiments, the first pipeline 1 further includes a first accumulator 104, and the second pipeline 2 further includes a second accumulator 204. Both are used to passively inject emergency coolant into the reactor as a passive supplementary injection function. Regardless of the type of LOCA, water can be injected into the primary circuit as long as the pressure drops below the target pressure.

[0051] Specifically, the first accumulator 104 is disposed on the first emergency core water injection pipe and is disposed downstream of the first safety injection pump 101. The second accumulator 204 is disposed on the second emergency core water injection pipe and is disposed downstream of the third safety injection pump 201 to facilitate faster injection of emergency coolant into the reactor.

[0052] It should be understood that both the first accumulator 104 and the second accumulator 204 contain boron water and rely on compressed nitrogen to provide rapid injection, which can be achieved using prior art.

[0053] In some embodiments, the first pipeline 1 further includes a first safety injection heat exchanger 103, and the second pipeline 2 further includes a second safety injection heat exchanger 203. Both are used to exchange heat with the water pumped by each safety injection pump, thereby reducing the temperature of the cooling water, improving the cooling effect, and thus shorten the path for the core heat to be discharged to the outside of the containment.

[0054] Specifically, the first safety injection heat exchanger 103 is disposed downstream of the first safety injection pump 101, and the second safety injection heat exchanger 203 is disposed downstream of the third safety injection pump 201.

[0055] In this embodiment, the output end of the first connecting pipe 15 is connected to the pipe between the second safety injection heat exchanger 203 and the third safety injection pump 201, so that the cooling water pumped out by the second safety injection pump 102 can be cooled by heat exchange in the second safety injection heat exchanger 203. The output end of the second connecting pipe 25 is connected to the pipe between the first safety injection heat exchanger 103 and the first safety injection pump 101. This allows the cooling water pumped out by the fourth safety injection pump 202 to be cooled by heat exchange in the first safety injection heat exchanger 103.

[0056] In some embodiments, the first emergency core water injection pipe includes a first cold leg pipe section 11 and a first output pipe section 13. The first cold leg pipe section 11 is located outside the containment boundary, its input end is connected to the in-containment refueling water storage tank 001, and its output end is connected to the input end of the first output pipe section 13, which is located inside the containment boundary and its output end is connected to the first interface 109. The first safety injection pump 101 and the first safety injection heat exchanger 103 are both disposed on the first cold leg pipe section 11, and the first accumulator 104 is connected to the first output pipe section 13.

[0057] The second emergency core water injection pipe includes a second cold leg pipe section 21 and a second output pipe section 23. The second cold leg pipe section 21 is located outside the containment boundary, with its input end connected to the in-containment refueling water storage tank 001 and its output end connected to the input end of the second output pipe section 23. The second output pipe section 23 is located inside the containment boundary, and its output end is connected to the second interface 209. The third safety injection pump 201 and the second safety injection heat exchanger 203 are both disposed on the second cold leg pipe section 21, and the second accumulator 204 is connected to the second output pipe section 23.

[0058] It should be understood that, since the in-containment refueling water storage tank 001 is located inside the containment, the first emergency core water injection pipe also includes a first water intake pipe section 12, the input end of which is connected to the in-containment refueling water storage tank 001, and the output end of which is connected to the input end of the first cold leg pipe section 11. The second emergency core water injection pipe also includes a second water intake pipe section 22, the input end of which is connected to the in-contamment refueling water storage tank 001, and the output end of which is connected to the input end of the second cold leg pipe section 21.

[0059] In some other alternative embodiments, the first emergency core water injection pipe and the second emergency core water injection pipe may also share a water intake pipe section, which can be achieved by connecting the output end of the water intake pipe section to the input end of the first cold leg pipe section 11 and the second cold leg pipe section 21 respectively, so as to reduce the number of penetrations on the containment.

[0060] In some embodiments, a sump screen is also provided between the first water intake pipe section 12 and the second water intake pipe section 22 and the in-containment refueling water storage tank 001 to filter out impurities in the cooling water.

[0061] In some embodiments, the input end and the output end of the first cold leg pipe section 11 are respectively provided with electrically controlled valves, namely a first electrically controlled valve 108 and a second electrically controlled valve 110. The input end and the output end of the second cold leg pipe section 21 are also respectively provided with electrically controlled valves, namely the third electrically controlled valve 208 and the fourth electrically controlled valve 210.

[0062] In some embodiments, the first output pipe section 13 is provided with three check valves, namely a first check valve 105, a second check valve 106 and a third check valve 107. The second output pipe section 23 is also provided with three check valves, namely the fourth check valve 205, the fifth check valve 206 and the sixth check valve 207.

[0063] It should be understood that, since the equipment structure connected to the first output pipe section 13 and the second output pipe section 23 is the pressure boundary of the reactor, at least two check valves should be respectively arranged on the parts of the first output pipe section 13 and the second output pipe section 23 closest to the first interface 109 and the second interface 209. The containment is another pressure boundary of the reactor, so a check valve and an electrically controlled valve need to be arranged inside and outside the containment, respectively. Therefore, three check valves are respectively arranged in the first output pipe section 13 and the second output pipe section 23, and an electrically controlled valve is arranged at the output end of each of the first cold leg pipe section 11 and the second cold leg pipe section 21.

[0064] In some embodiments, the input end of the first connecting pipe 15 is connected to the output end of the first water intake pipe section 12, and the first connecting pipe 15 is connected to the in-containment refueling water storage tank 001 through the first water intake pipe section 12. The input end of the second connecting pipe 25 is connected to the output end of the second water intake pipe section 22, and the second connecting pipe 25 is connected to the in-containment refueling water storage tank 001 through the second water intake pipe section 22. By sharing the first water intake pipe section 12 and the second water intake pipe section 22 to draw water from the in-containment refueling water storage tank 001, the number of through holes at the containment boundary can be reduced, thereby reducing the risk of containment leakage or bypass. At the same time, the number and total length of pipes are reduced, improving the economy of the emergency core cooling system.

[0065] In this embodiment, the output end of the first connecting pipe 15 is connected to the first cold leg pipe section 11 between the first electrically controlled valve 108 and the first safety injection pump 101, and then connected to the output end of the first water intake pipe section 12. The output end of the second connecting pipe 25 is connected to the second cold leg pipe section 21 between the third electrically controlled valve 208 and the third safety injection pump 201, and then connected to the output end of the second water intake pipe section 22. This can reduce the number of electrically controlled valves arranged at the containment boundary, further improving the economic performance of the emergency core cooling system.

[0066] In some other alternative embodiments, the output end of the first water intake pipe section 12 (the output end of the second water intake pipe section 22) can also be connected to the input end of the first cold leg pipe section 11 (the second cold leg pipe section 21) and the input end of the first connecting pipe 15 (the second connecting pipe 25) through a connecting valve such as a three-way valve, and the input end of the first cold leg pipe section 11 (the second cold leg pipe section 21) and the input end of the first connecting pipe 15 (the second connecting pipe 25) are respectively provided with an electrically controlled valve.

[0067] In some other alternative embodiments, the output end of the first water intake pipe section 12 (the output end of the second water intake pipe section 22) can be connected to the input end of the first connecting pipe 15 (the second connecting pipe 25), and the input end of the first cold leg pipe section 11 (the second cold leg pipe section 21) can be connected to the first connecting pipe 15 (the second connecting pipe 25) upstream of the second safety injection pump 102 (the fourth safety injection pump 202), so that the connection with the output end of the first water intake pipe section 12 (the output end of the second water intake pipe section 22) can be achieved through a portion of the first connecting pipe 15 (the second connecting pipe 25).

[0068] In some other alternative embodiments, four water intake pipe sections can be provided, with their input ends connected to the in-containment refueling water storage tank 001, and their output ends connected to the input end of the first connecting pipe 15, the input end of the second connecting pipe 25, the input end of the first cold leg pipe section 11, and the input end of the second cold leg pipe section 21, respectively.

[0069] In some embodiments, the first pipeline 1 further includes a first hot leg pipe 14, the input end of which is connected to the first cold leg pipe section 11, and the output end of which is communicated with one of hot legs of the reactor loop. The second pipeline 2 further includes a second hot leg pipe 24, the input end of which is connected to the second cold leg pipe section 21, and the output end of which is communicated with another hot leg of the reactor loop. The first hot leg pipe 14 and the second hot leg pipe 24 are used to inject emergency coolant into hot legs of the reactor loop when a break occurs. The arrangement of two independent hot leg pipes not only satisfies the principle of independence but also the single fault criterion, ensuring that if one pipe fails, the other can still be put into use.

[0070] It should be understood that there are three hot legs of the reactor loop, and they are interconnected. Therefore, the output ends of the first hot leg pipe 14 and the second hot leg pipe 24 can be arbitrarily communicated with two different hot legs of the reactor loop.

[0071] In some embodiments, the first hot leg pipe 14 and the second hot leg pipe 24 are respectively partially located outside the containment boundary and partially located inside the containment boundary. Furthermore, electrically controlled valves are further provided on partial pipes located outside the containment boundary, and three check valves are further provided on partial pipes located inside the containment boundary. To protect the two pressure boundaries, further details will not be elaborated here.

[0072] In this embodiment, the input end of the first hot leg pipe 14 is connected to the pipe between the first safety injection heat exchanger 103 and the second electrically controlled valve 110, and the input end of the second hot leg pipe 24 is connected to the pipe between the second safety injection heat exchanger 203 and the fourth electrically controlled valve 210.

[0073] It should be understood that the output ends of the first hot leg pipe 14 and the second hot leg pipe 24 can share a connection port with the residual heat removal system and be communicated with hot legs of the reactor loop. This reduces the number of openings on the reactor main equipment, lowering the probability of a LOCA in the main pipe of the reactor coolant system.

[0074] In some embodiments, the first pipeline 1 further includes a third connecting pipe 16, the two ends of which are connected to the first accumulator 104 and the first output pipe section 13 respectively, for outputting the emergency coolant in the first accumulator 104 to the reactor pressure vessel through the first output pipe section 13. The second pipeline 2 further includes a fourth connecting pipe 26, the two ends of which are connected to the second accumulator 204 and the second output pipe section 23, respectively, for outputting the emergency coolant m the second accumulator 204 to the reactor pressure vessel through the second output pipe section 23.

[0075] Specifically, the third connecting pipe 16 is further provided with a fifth electrically controlled valve 113 and a seventh check valve 114, the fifth electrically controlled valve 113 is located upstream of the seventh check valve 114. The fourth connecting pipe 26 is further provided with a sixth electrically controlled valve 213 and an eighth check valve 214, the sixth electrically controlled valve 213 is located upstream of the eighth check valve 214.

[0076] In some embodiments, the output end of the first safety injection pump 101 is provided with a ninth check valve 111, the output end of the second safety injection pump 102 is provided with a tenth check valve 112, the output end of the third safety injection pump 201 is provided with an eleventh check valve 211, and the output end of the fourth safety injection pump 202 is provided with a twelfth check valve 212, to prevent backflow of emergency coolant.

[0077] In this embodiment, the output end of the first connecting pipe 15 is connected to the pipe between the eleventh check valve 211 and the second safety injection heat exchanger 203, and the output end of the second connecting pipe 25 is connected to the pipe between the ninth check valve 111 and the first safety injection heat exchanger 103.

[0078] The emergency core cooling system is further explained below through its different responses under various operating conditions of the nuclear power plant:

[0079] During normal operation of the unit. To ensure a timely response in the event of an accident, the emergency core cooling system is always in a standby state. At this time, all valves (except check valves) on the two main pipes, the third connecting pipe 16, and the fourth connecting pipe 26 are open, while the valves on the first hot leg pipe 14 and the second hot leg pipe 24 are closed. The first safety injection pump 101, the second safety injection pump 102, the third safety injection pump 201, and the fourth safety injection pump 202 are all in a shutdown standby state.

[0080] Under conditions of large break-loss of coolant accident (LB-LOCA) and medium LOCA with relatively large break size in the unit. Since the unit has a large break, the primary circuit depressurizes quickly, and the back pressure can be rapidly reduced to below the applicable pressure of each medium head safety injection pump. The emergency core injection signal triggers the four safety injection pumps to start (at the same time, when the pressure of the primary circuit drops below the nitrogen pressure of the two accumulators, the two passive accumulators also inject emergency coolant into the core), injecting cooling water into the core to achieve core re-flooding and restore the water capacity of the reactor core.

[0081] At this point, considering the most unfavorable single failure, one of the pipelines (such as the first pipeline 1) becomes unavailable, the emergency core cooling system can still inject emergency coolant into the core through two safety injection pumps in another intact pipeline (the second pipeline 2).

[0082] In the event of a direct vessel injection LOCA (DVI-LOCA), that is, a LOCA occurs in the first output pipe section 13 or the second output pipe section 23. At this time, if one of the pipelines is unavailable (such as the first pipeline 1), the emergency core cooling system can only inject emergency coolant into the core through two safety injection pumps in another pipeline (the second pipeline 2). When the back pressure drops below the applicable pressure of the two medium head safety injection pumps, the emergency core injection signal triggers the two safety injection pumps to start (during this process, when the pressure of the primary circuit drops below the nitrogen pressure of the second accumulator 204, it also begins to inject emergency coolant into the core), injecting cooling water into the core to achieve core re-flooding and restore the water capacity of the reactor core.

[0083] At this point, considering the most unfavorable single failure, such as the failure of the power supply to the second pipeline 2 (failure of the emergency diesel generator), the two safety injection pumps of the second pipeline 2 cannot be started and used. At this time, the emergency diesel generator of the first pipeline 1 can also supply the second safety injection pump 102 of the first pipeline 1, the first connecting pipe 15 is connected to the second emergency core water injection pipe, thereby realizing the injection of cooling water into the core.

[0084] It should be understood that, if such a LOCA occurs during this process, and such a single failure occurs, resulting in only one safety injection pump being available, but the reactor back pressure is too high to be reduced to the starting pressure of safety injection pump, then the primary circuit pressure can be quickly reduced in conjunction with the medium-pressure rapid cooling valve on the secondary side of the steam generator.

[0085] A break occurs in the residual heat removal system pipeline during the residual heat removal state. At this point, one of the two residual heat removal systems that had broke was isolated, leaving only the other system in operation. At this point, considering the single fault criterion, the operating residual heat removal system fails and shuts down. At this time, water can be injected into the primary circuit through the emergency core cooling system, and the safety valve of the pressurizer (PZR) can be opened at the same time. Water can be drained into the in-containment refueling water storage tank through the depressurization tank and the return water pipeline connected to the depressurization tank and the in-containment refueling water storage tank, thereby realizing the injecting-draining function of the primary circuit. The heat of the core will be discharged into the in-contamment refueling water storage tank and the heat in the in-containment refueling water storage tank is finally carried away by the first safety injection heat exchanger 103 and the second safety injection heat exchanger 203 through heat exchange and cooling, thereby replacing the residual heat removal system for heat removal, so as to shorten the path of core heat to be discharged outside the containment.

[0086] It is understood that the above embodiments only illustrate some implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that for those skilled m the art, the above technical features can be freely combined, and several modifications and improvements can be made without departing from the concept of the present invention, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

What is claimed is:1 .An emergency core cooling system, comprising:a first pipeline (1), comprising a first safety injection pump (101), a second safety injection pump (102), a first emergency core water injection pipe, and a first connecting pipe (15) for supplying emergency coolant to a second interface (209) of the reactor pressure vessel; the input end of the first emergency core water injection pipe is connected to an in-containment refueling water storage tank (001), and the output end is connected to a first interface (109) of the reactor pressure vessel; the first safety injection pump (101) is arranged on the first emergency core water injection pipe; the input end of the first connecting pipe (15) is connected to the in-containment refueling water storage tank (001), and the output end is connected to the second interface (209); the second safety injection pump (102) is arranged on the first connecting pipe (15); anda second pipeline (2), comprising a third safety injection pump (201), a fourth safety injection pump (202), a second emergency core water injection pipe, and a second connecting pipe (25) for supplying emergency coolant to the first interface (109); the input end of the second emergency core water injection pipe is connected to the in-containment refueling water storage tank (001), and the output end is connected to the second interface (209); the third safety injection pump (201) is arranged on the second emergency core water injection pipe; the input end of the second connecting pipe (25) is connected to the in-containment refueling water storage tank (001), and the output end is connected to the first interface (109); the fourth safety injection pump (202) is arranged on the second connecting pipe (25).

2. The emergency core cooling system according to claim 1, wherein the first pipeline (1) further comprises a first accumulator (104), the first accumulator (104) is disposed downstream of the first safety injection pump (101), and the second pipeline (2) further comprises a second accumulator (204), the second accumulator (204) is disposed downstream of the third safety injection pump (201).3.The emergency core cooling system according to claim 1, wherein the first pipeline (1) further comprises a first safety injection heat exchanger (103), the second pipeline (2) further comprisesa second safety injection heat exchanger (203), the first safety injection heat exchanger (103) is disposed downstream of the first safety injection pump (101), and the second safety injection heat exchanger (203) is disposed downstream of the third safety injection pump (201); andthe output end of the first connecting pipe (15) is connected to the pipe between the second safety injection heat exchanger (203) and the third safety injection pump (201), and the output end of the second connecting pipe (25) is connected to the pipe between the first safety injection heat exchanger (103) and the first safety injection pump (101).

4. The emergency core cooling system according to claim 2, wherein the first emergency core water injection pipe comprises a first cold leg pipe section (11) located outside the containment boundary and a first output pipe section (13) located inside the containment boundary; the two ends of the first cold leg pipe section (11) are respectively connected to the in-containment refueling water storage tank (001) and the input end of the first output pipe section (13); the output end of the first output pipe section (13) is connected to the first interface (109), the first safety injection pump (101) is disposed on the first cold leg pipe section (11), the first accumulator (104) is connected to the first output pipe section (13); andthe second pipeline (2) comprises a second cold leg pipe section (21) located outside the containment boundary and a second output pipe section (23) located inside the containment boundary; the two ends of the second cold leg pipe section (21) are respectively connected to the in-containment refueling water storage tank (001) and the input end of the second output pipe section (23); the output end of the second output pipe section (23) is connected to the second interface (209), the third safety injection pump (201) is disposed on the second cold leg pipe section (21), and the second accumulator (204) is connected to the second output pipe section (23).5.The emergency core cooling system according to claim 4, wherein the first pipeline (1) further comprises a first hot leg pipe (14), the input end of the first hot leg pipe (14) is connected to the output end of the first cold leg pipe section (11), and the output end of the first hot leg pipe (14) is communicated with one of hot legs of the reactor loop; andthe second pipeline (2) further comprises a second hot leg pipe (24), the input end of which is connected to the output end of the second cold leg pipe section (21), and the output end of the second hot leg pipe (24) is communicated with another hot leg of the reactor loop.

6. The emergency core cooling system according to claim 4, wherein the first pipeline (1) further comprises a third connecting pipe (16) whose two ends are respectively connected to the first accumulator (104) and the first output pipe section (13), and the third connecting pipe (16) is provided with a check valve and an electrically controlled valve; the second pipeline (2) further comprises a fourth connecting pipe (26) whose two ends are respectively connected to the second accumulator (204) and the second output pipe section (23), and the fourth connecting pipe (26) is provided with a check valve and an electrically controlled valve.

7. The emergency core cooling system according to claim 4, wherein the first pipeline (1) further comprises a first water intake pipe section (12) located within the containment boundary, the two ends of which are respectively connected to the in-containment refueling water storage tank (001) and the input end of the first cold leg pipe section (11); andthe second pipeline (2) further comprises a second water intake pipe section (22) located within the containment boundary, the two ends of which are respectively connected to the in-containment refueling water storage tank (001) and the input end of the second cold leg pipe section (21).

8. The emergency core cooling system according to claim 7, wherein the input end of the first connecting pipe (15) is connected to the output end of the first water intake pipe section (12), and is connected to the in-containment refueling water storage tank (001) through the first water intake pipe section (12); andthe input end of the second connecting pipe (25) is connected to the output end of the second water intake pipe section (22), and is connected to the in-containment refueling water storage tank (001) through the second water intake pipe section (22).

9. The emergency core cooling system according to claim 7, wherein a sump screen is provided between the first water intake pipe section (12) and the second water intake pipe section (22) and the in-containment refueling water storage tank (001).10.The emergency core cooling system according to claim 4, wherein both ends of the first cold leg pipe section (11) and the second cold leg pipe section (21) are provided with electrically controlled valves, and the first output pipe section (13) and the second output pipe section (23) are each provided with three check valves.11.The emergency core cooling system according to claim 5, wherein the first hot leg Pipe (14) and the second hot leg pipe (24) are partially located outside the containment boundary and partially located inside the containment boundary, and are respectively provided with an electrically controlled valve and three check valves; the electrically controlled valves on the first hot leg pipe (14) and the second hot leg pipe (24) are all located outside the containment boundary, and the three check valves on the first hot leg pipe (14) and the second hot leg Pipe (24) are all located inside the containment boundary.

12. The emergency core cooling system according to claim 1, wherein the output ends of the first safety injection pump (101), the second safety injection pump (102), the third safety injection pump (201) and the fourth safety injection pump (202) are all equipped with check valves.13.The emergency core cooling system according to claim 1, wherein the first safety injection pump (101), the second safety injection pump (102), the third safety injection pump (201) and the fourth safety injection pump (202) are all medium head safety injection pumps.PCT / CN2025 / 089326A. CLASSIFICATION OF SUBJECT MATTER G21C15 / 18(2006.01)i; G21C15 / 14(2006.01)i According to International Patent Classification (IPC) or to both national classification and IPC B. FIELDS SEARCHED Minimum documentation searched (classification system followed by classification symbols) IPC- G21C15 / - Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched Electronic data base consulted during the international search (name of data base and, where practicable, search terms used) CNTXT, ENTXTC, DWPI, CNKI: ¢-—emergency, core, cooling, system, safety injection, pump, single failure C. DOCUMENTS CONSIDERED TO BE RELEVANT Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. PX CN 118507088 A (CHINA NUCLEAR POWER ENGINEERING CO., LTD. et al.) 16 August 2024 (2024-08-16) claims 1-13, description paragraphs 0039-0085, and figure 1 1-13 A A CN 111081399 A (CHINA NUCLEAR POWER ENGINEERING CO., LTD. et al.) 28 April 2020 (2020-04-28) description, paragraphs 0035-0077, and figure 1 CN 203596180 U (CHINA NUCLEAR POWER ENGINEERING CO., LTD.) 14 May 2014 (2014-05-14) entire document 1-13 1-13 A CN 209232422 U (CHINA NUCLEAR POWER INSTITUTE CO., LTD. et al.) 09 August 2019 (2019-08-09) entire document 1-13 A US 2014016734 Al (KOREA ATOMIC ENERGY RESEARCH INSTITUTE) 16 January 2014 (2014-01-16) entire document 1-13 | | Further documents are listed in the continuation of Box C. | J | See patent family annex. * Special categories of cited documents: “T” later document published after the international filing date or priority “A” document defining the general state of the art which is not considered date and not in conflict with the application but cited to understand the to be of particular- relevance principle or theory underlying the invention “D” document cited by the applicant in the international application “X” document of particular- relevance; the claimed invention cannot be “E” earlier application orpatent but published on or after the international considered novel or cannot be considered to involve an inventive step filing date when the document is taken alone “L” document which may throw doubts on priority claim(s) or which is “Y” document of particular relevance; the claimed invention cannot be cited to establish the publication date of another citation or other considered to involve an inventive step when the document is special reason (as specified) combined with one or more other such documents, such combination “O” document referring to an oral disclosure, use, exhibition or other being obvious to a person skilled in the art means document member of the same patent family “P” document published prior to the international filing date but later than the priority date claimed Date of the actual completion of the international search 29 July 2025 Date of mailing of the international search report 04 August 2025 Name and mailing address of the ISA / CN China National Intellectual Property Administration (ISA / CN) China No. 6, Xitucheng Road, Jimenqiao, Haidian District, Beijing 100088 Authorized officer Telephone No.PCT / CN2025 / 089326C. DOCUMENTS CONSIDERED TO BE RELEVANTCategory* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. A US 2014050292 Al (KOREA ATOMIC ENERGY RESEARCH INSTITUTE) 20 February 2014 (2014-02-20) entire document 1-13 A JP 2011107001 A (HITACHI GE NUCLEAR ENERGY LTD.) 02 June 2011 (2011-06-02) entire document 1-13INTERNATIONAL SEARCH REPORT Information on patent family membersInternational application No.PCT / CN2025 / 089326Patent document cited in search report Publication date (day / month / year) Patent family member, s) Publication date (day / month / year) CN 118507088 A 16 August 2024 None CN 111081399 A 28 April 2020 None CN 203596180 U 14 May 2014 None CN 209232422 U 09 August 2019 WO 2020098490 Al 22 May 2020 US 2014016734 Al 16 January 2014 US 9583224 B2 28 February 2017 KR 20140009835 A 23 January 2014 KR 101389276 Bl 25 April 2014 US 2014050292 Al 20 February 2014 KR 20140023067 A 26 February 2014 KR 101389836 Bl 29 April 2014 US 9905320 B2 27 February 2018 JP 2011107001 A 02 June 2011 JP 5586213 B2 10 September 2014

Images