Emergency core cooling system for nuclear power plant and cooling method

Abstract

Disclosed in the present invention are an emergency core cooling system for a nuclear power plant and a cooling method. The emergency core cooling system for a nuclear power plant comprises: a suppression pool provided in a containment, the suppression pool being provided with a guide part, and the guide part being used for guiding steam from the containment to the suppression pool; and a low-pressure safety injection unit, comprising a low-pressure safety injection pump, a heat exchange device and a spraying device, an inlet end of the low-pressure safety injection pump being connected to the suppression pool and a primary loop hot leg, an outlet end of the low-pressure safety injection pump being connected to an inlet end of the heat exchange device, an outlet end of the heat exchange device being connected to a primary loop cold leg and the spraying device, and the spraying device being arranged in the containment. The present invention can realize the intensive design of three functions, i.e. safety injection, emergency residual heat discharge and containment spraying, and quickly and efficiently implement pressure control in containments when loss-of-coolant accidents occur, thereby satisfying process design of compact / integrated pressurized water reactors.

Description

Nuclear power plant emergency core cooling system and cooling method TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear power engineering, in particular to a nuclear power plant emergency core cooling system and a cooling method. BACKGROUND

[0002] In order to achieve the three safety functions of residual heat removal, radioactive containment and reactivity control after an accident, a series of special safety facilities are provided in a nuclear power plant for relieving the three safety functions after an accident. In the configuration of special safety facilities of a traditional land commercial pressurized water reactor, independent systems such as safety injection, emergency residual heat removal and containment spray are configured to achieve the safety target after an accident. With the development of small pressurized water reactors, in order to achieve compact arrangement and improve economy, higher intensive design requirements are put forward for the configuration of special safety facilities on the basis of meeting relevant safety criteria; while achieving safety functions, the configuration and arrangement of each system in a very limited space need to be ensured; in addition, for compact / integrated pressurized water reactors, the pressure rises quickly after a break occurs due to the small size of the containment. In the design of the special safety system of the traditional pressurized water reactor, the containment spray system is directly triggered by the high containment pressure signal after a break accident, and there is a time difference between system start-up and accident occurrence, so the pressure in the containment cannot be quickly and effectively controlled in the early stage of the accident. SUMMARY

[0003] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a nuclear power plant emergency core cooling system, which can realize the intensive design of the three functions of safety injection, emergency residual heat removal and containment spray, and can quickly and effectively control the pressure in the containment when a break accident occurs, meeting the design requirements of compact / integrated pressurized water reactors.

[0004] The present application also provides a cooling method of the nuclear power plant emergency core cooling system according to the first aspect of the present application.

[0005] The nuclear power plant emergency core cooling system according to the first aspect of the present application comprises:

[0006] The pressure suppression pool is arranged in the containment, and the pressure suppression pool is provided with a guide portion for guiding the steam in the containment into the pressure suppression pool.

[0007] The low-pressure injection unit comprises a low-pressure injection pump, a heat exchange device and a spraying device, an inlet end of the low-pressure injection pump is connected with the pressure-suppression pool and a loop hot section, an outlet end of the low-pressure injection pump is connected with an inlet end of the heat exchange device, an outlet end of the heat exchange device is connected with a loop cold section and the spraying device, and the spraying device is arranged in the containment.

[0008] According to the nuclear power plant emergency core cooling system provided by the embodiment of the present application, at least the following beneficial effects are achieved:

[0009] In the embodiment of the present application, water can be taken from the pressure-suppression pool and injected into the spraying device by controlling the connection of the inlet end of the low-pressure injection pump with the pressure-suppression pool and the connection of the outlet end of the heat exchange device with the spraying device, so as to perform the containment spraying function; water can be taken from the loop hot section and injected into the loop cold section by controlling the connection of the inlet end of the low-pressure injection pump with the loop hot section and the connection of the outlet end of the heat exchange device with the loop cold section, so as to perform the emergency residual heat removal function; water can be taken from the pressure-suppression pool and injected into the loop cold section by controlling the connection of the inlet end of the low-pressure injection pump with the pressure-suppression pool and the connection of the outlet end of the heat exchange device with the loop cold section, so as to perform the low-pressure safety injection function, thereby realizing the intensive design of the three functions of safety injection, emergency residual heat removal and containment spraying; and when a break accident occurs, the steam generated by the break can be guided into the pressure-suppression pool by the guiding part of the pressure-suppression pool to be condensed in a short period of time, so as to quickly reduce the pressure of the containment, and the medium and long-term pressure control can be realized by the low-pressure injection unit performing the containment spraying function; the above-mentioned arrangement can meet the design requirements of the compact / integrated pressurized water reactor process.

[0010] According to some embodiments of the present application, the high-pressure injection unit comprises a high-pressure injection pump and a high-pressure injection pipeline, the high-pressure injection pump is arranged on the high-pressure injection pipeline, and at least part of the high-pressure injection pipeline is connected with the pressure-suppression pool and the loop cold section at two ends respectively.

[0011] According to some embodiments of the present application, the medium-pressure injection unit comprises a medium-pressure injection tank and a medium-pressure injection pipeline, and the medium-pressure injection pipeline is connected with the medium-pressure injection tank and the loop hot section at two ends respectively.

[0012] According to some embodiments of the present application, a water supplement pipeline is connected between the high-pressure injection pipeline and the medium-pressure injection tank, and the water supplement pipeline is located on one side of the outlet end of the high-pressure injection pump.

[0013] According to some embodiments of the present application, the heat exchange device comprises a heat exchanger, a first regulating valve and a second regulating valve, the heat exchanger is arranged in series with the first regulating valve, and the second regulating valve is arranged in parallel with the heat exchanger and the first regulating valve.

[0014] According to some embodiments of the present application, when the inlet end of the low-pressure injection pump is connected to the depressurized pool and the outlet end of the heat exchange device is connected to the spray device, the first regulating valve is opened and the second regulating valve is closed.

[0015] According to some embodiments of the present application, the guide part comprises a plurality of depressurized pipes, each of which has a depressurized pipe inlet for being connected to the inner cavity of the containment vessel and a depressurized pipe outlet for being connected to the inner cavity of the depressurized pool.

[0016] According to some embodiments of the present application, a first circulation pipeline is further arranged between the outlet end of the heat exchange device and the depressurized pool.

[0017] According to some embodiments of the present application, a second circulation pipeline is further arranged between the inlet end of the low-pressure injection pump and the outlet end of the heat exchange device.

[0018] The nuclear power plant emergency core cooling method according to the second aspect of the embodiments of the present application comprises:

[0019] In a design basis accident condition, when a break accident occurs and a containment pressure high signal is triggered, the low-pressure injection unit is manually started, the inlet end of the low-pressure injection pump is controlled to be connected to the depressurized pool, the outlet end of the heat exchange device is controlled to be connected to the spray device, water is taken from the depressurized pool and injected into the spray device, and a containment spray function is performed.

[0020] In a design basis accident condition, when a non-break accident occurs, the low-pressure injection unit is manually started, the inlet end of the low-pressure injection pump is controlled to be connected to the primary loop hot section, and the outlet end of the heat exchange device is controlled to be connected to the primary loop cold section, water is taken from the primary loop hot section and injected into the primary loop cold section, and an emergency residual heat removal function is performed.

[0021] In a design extension condition, the low-pressure injection unit is manually started, the inlet end of the low-pressure injection pump is controlled to be connected to the depressurized pool, and the outlet end of the heat exchange device is controlled to be connected to the primary loop cold section, water is taken from the depressurized pool and injected into the primary loop cold section, and a safety injection function is performed.

[0022] The nuclear power plant emergency core cooling method according to the embodiments of the present application has at least the following beneficial effects:

[0023] The cooling method of the nuclear power plant emergency core cooling system based on the first aspect of the embodiment can realize the intensive design of the three functions of safety injection, emergency residual heat removal and containment spray; and when a break accident occurs, the steam generated by the break can be guided into the depressurization pool through the guide part of the depressurization pool for condensation in a short period of time, so as to quickly reduce the pressure of the containment, and the long-term pressure control is realized by the low-pressure safety injection unit to perform the containment spray function, so as to meet the compact / integrated pressurized water reactor process design.

[0024] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter in the description. BRIEF DESCRIPTION OF DRAWINGS

[0025] The present application will be further described below in conjunction with the accompanying drawings and embodiments, wherein:

[0026] Fig. 1 is a schematic diagram of a nuclear power plant emergency core cooling system according to an embodiment of the present application.

[0027] Reference signs: depressurization pool 1, depressurization pipe 11, water taking pipe 12, low-pressure safety injection unit 2, low-pressure safety injection pump 21, heat exchange device 22, heat exchanger 221, first regulating valve 222, second regulating valve 223, spray device 23, first pipe 24, second pipe 25, third pipe 26, fourth pipe 27, safety valve 28, isolation valve 3, check valve 4, high-pressure safety injection unit 5, high-pressure safety injection pump 51, high-pressure safety injection pipe 52, cut-off check valve 53, medium-pressure safety injection unit 6, medium-pressure safety injection tank 61, medium-pressure safety injection pipe 62, water supply pipe 7, first circulation pipe 8, second circulation pipe 9. DETAILED DESCRIPTION

[0028] The embodiments of the present application will be described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0029] In the description of the present application, it should be understood that the orientation description, such as the orientation or position relationship indicated by up, down, front, back, left, right, etc. is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as a limitation of the present application, which indicates or implies that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation.

[0030] In the description of the present application, if several meanings are one or more, the meaning of multiple is two or more, greater than, less than, more than, etc. are understood as not including the number, above, below, within, etc. are understood as including the number. If it is described as first, second, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0031] In the description of the present application, unless otherwise explicitly limited, the words such as setting, installing, connecting, etc. should be broadly understood, and those skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical solution.

[0032] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "illustrative embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0033] Referring to FIG. 1, the emergency core cooling system of a nuclear power plant according to an embodiment of the present application includes a depressurization pool 1 and a low pressure injection unit 2. It should be noted that the reactor core generates huge heat energy due to nuclear fuel fission, and the water pumped into the core (located in the pressure vessel) by the main pump is heated, and the heated water flows through the steam generator to exchange heat with the secondary circuit, releases heat, and is then pumped back to the core by the main pump to be reheated and then enters the steam generator. The water is continuously circulated in a closed loop, which is called a primary circuit; the cold section of the primary circuit is the part between the main pump and the core in the primary circuit, and the hot section of the primary circuit is the part between the core and the steam generator in the primary circuit.

[0034] The depressurization pool 1 is arranged in the containment, and the depressurization pool 1 is provided with a guide portion for guiding the steam in the containment into the depressurization pool 1; it can be understood that for a compact / integrated pressurized water reactor, when a break accident occurs, the pressure rises very quickly after the break due to the small size of the containment, at this time the steam in the containment can be guided into the depressurization pool 1 through the guide portion for condensation, to relieve the pressure rise effect in the containment and achieve short-term containment pressure control.

[0035] The low-pressure injection unit 2 comprises a low-pressure injection pump 21, a heat exchange device 22 and a spray device 23. The inlet end of the low-pressure injection pump 21 is connected to the suppression pool 1 and a hot section of a primary loop, the outlet end of the low-pressure injection pump 21 is connected to the inlet end of the heat exchange device 22, the outlet end of the heat exchange device 22 is connected to a cold section of the primary loop and the spray device 23, and the spray device 23 is arranged in the containment. In this embodiment, the spray device 23 comprises a spray ring, which can be arranged on the inner top of the containment. The low-pressure injection pump 21 can take water from the suppression pool 1 and inject it into the spray device 23 to perform the spray function of the containment by controlling the connection of the inlet end of the low-pressure injection pump 21 to the suppression pool 1 and the connection of the outlet end of the heat exchange device 22 to the spray device 23. The low-pressure injection pump 21 can take water from the hot section of the primary loop and inject it into the cold section of the primary loop to perform the emergency residual heat removal function by controlling the connection of the inlet end of the low-pressure injection pump 21 to the hot section of the primary loop and the connection of the outlet end of the heat exchange device 22 to the cold section of the primary loop. The low-pressure injection pump 21 can take water from the suppression pool 1 and inject it into the cold section of the primary loop to perform the safety injection function by controlling the connection of the inlet end of the low-pressure injection pump 21 to the suppression pool 1 and the connection of the outlet end of the heat exchange device 22 to the cold section of the primary loop.

[0036] With the above arrangement, the intensive design of the three functions of safety injection, emergency residual heat removal and containment spray can be realized. In the event of a break accident, the steam generated by the break can be guided into the suppression pool 1 through the guide part of the suppression pool 1 to condense and rapidly reduce the pressure of the containment in the short term, and the long-term pressure control is realized by the low-pressure injection unit 2 performing the containment spray function, thereby meeting the compact / integrated pressurized water reactor process design.

[0037] It can be understood that in some embodiments, isolation valves 3 are arranged on the pipeline connecting the inlet end of the low-pressure injection pump 21 to the suppression pool 1, the pipeline connecting the inlet end of the low-pressure injection pump 21 to the hot section of the primary loop, the pipeline connecting the outlet end of the heat exchange device 22 to the cold section of the primary loop, and the pipeline connecting the outlet end of the heat exchange device 22 to the spray device 23. The isolation valves 3 are used to control the opening and closing of the pipelines, and can be electric valves. By controlling the opening and closing of the isolation valves 3 to control the connection of different pipelines, the low-pressure injection unit 2 can realize different functions. Further, in some embodiments, check valves 4 can also be arranged on the pipeline connecting the inlet end of the low-pressure injection pump 21 to the suppression pool 1, the pipeline connecting the inlet end of the low-pressure injection pump 21 to the hot section of the primary loop, the pipeline connecting the outlet end of the heat exchange device 22 to the cold section of the primary loop, and the pipeline connecting the outlet end of the heat exchange device 22 to the spray device 23. The check valves 4 are used to prevent the backflow of water in the pipelines.

[0038] Specifically, as shown in FIG. 1, in the embodiment, the suppression pool 1 is connected with a water taking pipeline 12, an isolation valve 3 is arranged on the water taking pipeline 12, an inlet end of the low-pressure injection pump 21 is connected with the water taking pipeline 12 through a first pipeline 24 to connect the suppression pool 1, and an isolation valve 3 is arranged on the first pipeline 24; the inlet end of the low-pressure injection pump 21 is connected with a loop heat section through a second pipeline 25, an isolation valve 3 is arranged on the second pipeline 25 outside the containment vessel, and two isolation valves 3 are arranged in the containment vessel, a plurality of isolation valves 3 are arranged to segmentally isolate the first pipeline 24, which can reduce the probability of pressure spreading outside the containment vessel caused by the false opening of the valve and improve the safety; an outlet end of the heat exchange device 22 is connected with a loop cold section through a third pipeline 26, two isolation valves 3 are arranged in parallel on the third pipeline 26 outside the containment vessel, and two check valves 4 are arranged in the containment vessel, the parallel arrangement of the two isolation valves 3 can prevent the third pipeline 26 from being connected due to the failure of a single isolation valve 3 to open, thereby improving the stability and reliability of the system; the outlet end of the heat exchange device 22 is connected with the spraying device 23 through a fourth pipeline 27, an isolation valve 3 is arranged on the fourth pipeline 27 outside the containment vessel, and a check valve 4 is arranged in the containment vessel; it should be noted that the above only shows one embodiment, and in actual application, the number and position of the isolation valves 3 or check valves 4 on each pipeline can be adaptively adjusted according to the actual application requirements.

[0039] Further, to prevent the pressure of the second pipeline 25 from being too high when emergency residual heat is discharged, a safety valve 28 is further arranged on the second pipeline 25, the safety valve 28 can be arranged between two adjacent isolation valves 3 on the second pipeline 25, and when the pressure of the second pipeline 25 is too high, part of the medium can be discharged through the safety valve 28 to prevent the pressure in the pipeline from exceeding the specified value.

[0040] In some embodiments of the present application, the nuclear power plant emergency core cooling system further comprises a high-pressure injection unit 5 and a medium-pressure injection unit 6, the high-pressure injection unit 5 is provided in plurality, the high-pressure injection unit 5 adopts an active system configuration, which comprises a high-pressure injection pump 51 and a high-pressure injection pipeline 52, the high-pressure injection pump 51 is arranged on the high-pressure injection pipeline 52, the high-pressure injection pump 51 is arranged as a constant-flow plunger pump, and a driving pressure head is provided by the high-pressure injection pump 51, wherein at least part of the high-pressure injection pipeline 52 is connected to the suppression pool 1 and a cold section of the primary loop at both ends, and at least part of the high-pressure injection pipeline 52 is connected to the suppression pool 1 and a hot section of the primary loop at both ends, that is, the high-pressure injection unit 5 is correspondingly arranged in the hot section and the cold section of the primary loop. It can be understood that in the conventional pressurized water reactor dedicated safety system, the safety injection is first injected into the cold section, and then switched to the cold-hot section simultaneous injection, and through one main pipeline, two branches are branched out, and the two branches correspond to the cold section and the hot section of the primary loop respectively, and the water flow direction is controlled by the valve, so that when the injection point is switched, the problem of flow redistribution will be involved; therefore, in the present embodiment, the high-pressure injection unit 5 is provided in plurality, the high-pressure injection unit 5 is correspondingly arranged in the hot section and the cold section of the primary loop, and the high-pressure injection unit 5 corresponding to the cold section of the primary loop and the high-pressure injection unit 5 corresponding to the hot section of the primary loop are independent of each other, so that independent injection of the cold section and the hot section of the primary loop can be realized, simultaneous injection after the accident can be realized, and the problem of injection flow redistribution caused by injection point switching is avoided, and the system control is more simple and convenient. Specifically, the high-pressure injection pipeline 52 is connected to the suppression pool 1 through the water taking pipeline 12, and the isolation valve 3 and the check valve 4 are arranged on the high-pressure injection pipeline 52, when an accident occurs, after the high-pressure injection unit 5 receives the injection signal, the isolation valve 3 on the high-pressure injection pipeline 52 is opened, and water is taken from the suppression pool 1 to perform safety injection.

[0041] The medium-pressure injection unit 6 adopts a passive system configuration, which comprises a medium-pressure injection tank 61 and a medium-pressure injection pipeline 62, the medium-pressure injection tank 61 is located in the containment, the medium-pressure injection tank 61 is pre-charged with covering nitrogen, a driving pressure head is provided by the pre-charged nitrogen, the medium-pressure injection pipeline 62 is connected to the medium-pressure injection tank 61 and the hot section of the primary loop at both ends, the isolation valve 3 and the check valve 4 are arranged on the medium-pressure injection pipeline 62, when an accident occurs, after the medium-pressure injection unit 6 receives the injection signal (i.e. when the pressure of the primary loop is less than the pressure of the pre-charged nitrogen in the medium-pressure injection tank 61), the isolation valve 3 on the medium-pressure injection pipeline 62 is opened to perform safety injection function. Obviously, the number and position of the isolation valve 3 or the check valve 4 on the high-pressure injection pipeline 52 and the medium-pressure injection pipeline 62 can be adaptively adjusted according to actual application requirements. It can be conceived that the medium-pressure injection unit 6 can be provided in plurality, and each medium-pressure injection unit 6 corresponds to an injection point of the hot section of the primary loop.

[0042] In the embodiment, in the design reference accident condition, when the break accident occurs, the high-pressure injection unit 5 and the medium-pressure injection unit 6 are triggered by the injection signal to automatically start to perform the safety injection function. The safety injection function in the short-term accident is performed by the high-pressure injection unit 5 and the medium-pressure injection unit 6, the long-term function is performed by the high-pressure injection unit 5, and the low-pressure injection unit 2 is in the injection standby state. In the design extension condition, when the break / non-break accident iteratively fails the high-pressure injection unit 5, the low-pressure injection unit 2 is manually started by the main control room operator to perform the safety injection function. In the design reference accident condition, when the break accident occurs and the containment pressure high signal triggers, the low-pressure injection unit 2 is manually started by the main control room operator, the inlet end of the low-pressure injection pump 21 is connected to the suppression pool 1, and the outlet end of the heat exchange device 22 is connected to the spray device 23, water is taken from the suppression pool 1, injected into the spray device 23, and the containment spray function is performed. In the design reference accident condition, when the non-break accident occurs, the low-pressure injection unit 2 is manually started by the main control room operator, the inlet end of the low-pressure injection pump 21 is connected to the primary loop hot section, and the outlet end of the heat exchange device 22 is connected to the primary loop cold section, water is taken from the primary loop hot section, injected into the primary loop cold section, and the emergency residual heat removal function is performed. In this way, various design reference accident conditions and design extension conditions can be coped with.

[0043] In some embodiments of the application, a water supplement pipeline 7 is connected between the high-pressure injection pipeline 52 and the medium-pressure injection tank 61. The water supplement pipeline 7 is located on the outlet side of the high-pressure injection pump 51. During the overhaul, the primary loop is opened and is in the normal pressure state. The system needs to be watered during the recovery stage. At this time, the water supplement pipeline 7 can be connected, water is taken from the suppression pool 1 by the high-pressure injection pump 51, and the medium-pressure injection tank 61 is watered by the water supplement pipeline 7. The isolation valve 3 is arranged on the water supplement pipeline 7 to control the opening and closing thereof. In addition, it can be understood that, in order to prevent water from flowing into the primary loop when the medium-pressure injection tank 61 is watered, a stop check valve 53 is arranged on the high-pressure injection pipeline 52 in the embodiment. The stop check valve 53 is located at the rear end of the connection point of the water supplement pipeline 7 and the high-pressure injection pipeline 52, so as to isolate the primary loop when the medium-pressure injection tank 61 is watered. When the system is normally operated, the stop check valve 53 functions as a check valve.

[0044] In some embodiments of the present application, the heat exchange device 22 comprises a heat exchanger 221, a first regulating valve 222 and a second regulating valve 223, the heat exchanger 221 is connected in series with the first regulating valve 222, and the second regulating valve 223 is connected in parallel with the heat exchanger 221 and the first regulating valve 222. In this way, the flow rate through the heat exchanger 221 can be adjusted by adjusting the first regulating valve 222, so as to adjust the heat removal rate of the heat exchanger 221. When the first regulating valve 222 is adjusted, the second regulating valve 223 is adjusted synchronously, so as to keep the flow rate of the low-pressure injection pump 21 within a constant range, prevent frequent fluctuations of the pump flow rate, and ensure stable operation of the system. For example, when the opening of the first regulating valve 222 is reduced, the flow rate through the heat exchanger 221 is reduced, and then the opening of the second regulating valve 223 is increased, so as to keep the flow rate of the low-pressure injection pump 21 constant. When the inlet end of the low-pressure injection unit 2 is connected to the depressurized pool 1 and the outlet end of the heat exchange device 22 is connected to the spray device 23, i.e. when the low-pressure injection unit 2 performs the containment spray function, the first regulating valve 222 is opened, and the second regulating valve 223 is closed. In this way, when the spray is performed, the flow rate output by the low-pressure injection pump 21 can pass through the heat exchanger 221, so as to maximize the heat removal rate of the heat exchanger 221 and ensure the effect of spray cooling.

[0045] In some embodiments of the present application, the guide part of the depressurized pool 1 comprises a plurality of depressurized pipes 11, each of the depressurized pipes 11 has a depressurized pipe inlet for being connected to the containment cavity and a depressurized pipe outlet for being connected to the inner cavity of the depressurized pool 1, and the outlet of each of the depressurized pipes 11 extends below the water surface of the depressurized pool 1. For a compact / integrated pressurized water reactor, when a break occurs, the pressure rises rapidly due to the small size of the containment, and at this time, the steam generated by the break can be guided into the depressurized pool 1 through the plurality of depressurized pipes 11 to be condensed, so as to relieve the pressure rise in the containment. In addition, it can be understood that, in order to prevent the water from being violently fluctuated when the steam enters the depressurized pool 1 to be condensed, the outlet of each of the depressurized pipes 11 can be provided in a plurality of small holes, so as to reduce the size of the bubbles.

[0046] In some embodiments of the present application, the nuclear power plant emergency core cooling system further comprises a first circulation pipeline 8, which is connected between the outlet end of the heat exchange device 22 and the depressurized pool 1. Specifically, one end of the first circulation pipeline 8 is connected to the outlet end of the heat exchanger 221. In this way, when the temperature of the depressurized pool 1 is high, the first circulation pipeline 8 can be connected, so that the water circulates between the low-pressure injection pump 21, the heat exchanger 221 and the depressurized pool 1 to be cooled. In addition, when the low-pressure injection unit 2 performs the safety injection function, the first circulation pipeline 8 can be connected to assist the system startup, perform a small flow circulation, and prevent the low-pressure injection pump 21 from failing due to pressure build-up during startup. Specifically, an isolation valve 3 is arranged on the first circulation pipeline 8, and the opening and closing of the first circulation pipeline 8 is controlled by the isolation valve 3.

[0047] In some embodiments of the present application, the nuclear power plant emergency core cooling system further comprises a second circulation pipeline 9 connected between the inlet end of the low-pressure injection pump 21 and the outlet end of the heat exchange device 22, before the low-pressure injection unit 2 performs the emergency residual heat removal function, the low-pressure injection pump 21 can be started, and the second circulation pipeline 9 is connected to make the water circulate in the pipelines, and the water temperature is raised and the oxygen is discharged before being connected to the primary loop to achieve the water quality connection condition. Specifically, the second circulation pipeline 9 is provided with an isolation valve 3, and the opening and closing of the second circulation pipeline 9 is controlled through the isolation valve 3.

[0048] The present application further provides a cooling method applied to the nuclear power plant emergency core cooling system, and the method comprises:

[0049] In the design reference accident condition, when the break accident occurs and the containment pressure high signal is triggered, the low-pressure injection unit 2 is manually started by the main control room operator, the inlet end of the low-pressure injection pump 21 is connected to the suppression pool 1, and the outlet end of the heat exchange device 22 is connected to the spray device 23, the water is taken from the suppression pool 1 and injected into the spray device 23, and the containment spray function is performed, and it can be understood that for the compact / integrated pressurized water reactor, when the break accident occurs, the pressure rises quickly after the break due to the small size of the containment, at this time, the steam in the containment can be guided into the suppression pool 1 through the guide part (a plurality of suppression pipes 11) for condensation, to relieve the pressure rise effect in the containment and realize short-term containment pressure control, and the medium and long-term pressure control and heat export are realized by the low-pressure injection unit 2 performing the containment spray function, that is, the pressure control of the containment is realized by the guide part of the suppression pool 1 and the low-pressure injection unit 2 together;

[0050] In the design reference accident condition, when the non-break accident occurs, the low-pressure injection unit 2 is manually started by the main control room operator, the inlet end of the low-pressure injection pump 21 is connected to the primary loop hot section, and the outlet end of the heat exchange device 22 is connected to the primary loop cold section, the water is taken from the primary loop hot section and injected into the primary loop cold section, and the emergency residual heat removal function is performed;

[0051] In the design reference accident condition, when the break accident occurs, the high-pressure injection unit 5 and the medium-pressure injection unit 6 are automatically started to perform the safety injection function after receiving the injection signal, the safety injection function in the short-term accident is performed by the high-pressure injection unit 5 and the medium-pressure injection unit 6, and the long-term stage is performed by the high-pressure injection unit 5;

[0052] In the design extension condition, for example, in the iteration of high pressure safety injection unit 5 failure (standard assumed condition) in the break / non-break accident, the low pressure safety injection unit 2 can be manually started by the operator in the main control room, the inlet end of the low pressure safety injection pump 21 is connected to the suppression pool 1, and the outlet end of the heat exchange device 22 is connected to the primary loop cold section, water is taken from the suppression pool 1 and injected into the primary loop cold section to perform the safety injection function.

[0053] The cooling method of the nuclear power plant emergency core cooling system based on the first aspect of the embodiment can realize the intensive design of the three functions of safety injection, emergency residual heat removal and containment spray, and can cope with various design basis accident conditions or design extension conditions; and in the event of a break accident, the steam generated by the break can be guided into the suppression pool 1 through the guide part of the suppression pool 1 for condensation in the short term, so as to quickly reduce the pressure of the containment, and the medium and long term pressure control is realized by the low pressure safety injection unit 2 to perform the containment spray function, so as to meet the compact / integrated pressurized water reactor process design.

[0054] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. An emergency core cooling system for a nuclear power plant, characterized in that, include: A pressure-suppressing water tank is located inside the containment vessel. The pressure-suppressing water tank is equipped with a guide section for guiding steam inside the containment vessel into the pressure-suppressing water tank. The low-pressure injection unit includes a low-pressure injection pump, a heat exchange device, and a spray device. The inlet end of the low-pressure injection pump is connected to the pressure-suppressing water tank and the primary loop hot section. The outlet end of the low-pressure injection pump is connected to the inlet end of the heat exchange device. The outlet end of the heat exchange device is connected to the primary loop cold section and the spray device. The spray device is located inside the containment.

2. The nuclear power plant emergency core cooling system according to claim 1, characterized in that: It also includes multiple high-pressure injection units, each of which includes a high-pressure injection pump and a high-pressure injection pipeline. The high-pressure injection pump is located on the high-pressure injection pipeline. At least a portion of the high-pressure injection pipeline is connected at both ends to the pressure-suppressing water tank and the primary cold section, respectively. At least a portion of the high-pressure injection pipeline is connected at both ends to the pressure-suppressing water tank and the primary hot section, respectively.

3. The nuclear power plant emergency core cooling system according to claim 2, characterized in that: It also includes a medium-pressure safety injection unit, which includes a medium-pressure safety injection box and a medium-pressure safety injection pipeline. The two ends of the medium-pressure safety injection pipeline are respectively connected to the medium-pressure safety injection box and the primary circuit hot section.

4. The nuclear power plant emergency core cooling system according to claim 3, characterized in that: A water supply line is connected between the high-pressure safety injection pipeline and the medium-pressure safety injection tank, and the water supply line is located on one side of the outlet end of the high-pressure safety injection pump.

5. The nuclear power plant emergency core cooling system according to claim 1, characterized in that: The heat exchange device includes a heat exchanger, a first regulating valve, and a second regulating valve. The heat exchanger is connected in series with the first regulating valve, and the second regulating valve is connected in parallel with the heat exchanger and the first regulating valve.

6. The nuclear power plant emergency core cooling system according to claim 5, characterized in that: When the inlet end of the low-pressure injection pump is connected to the pressure-suppressing water tank and the outlet end of the heat exchange device is connected to the spray device, the first regulating valve opens and the second regulating valve closes.

7. The nuclear power plant emergency core cooling system according to claim 1, characterized in that: The guide section includes a plurality of pressure-suppressing pipes, each pressure-suppressing pipe having a pressure-suppressing pipe inlet for communicating with the inner cavity of the containment vessel and a pressure-suppressing pipe outlet for communicating with the inner cavity of the pressure-suppressing pool.

8. The nuclear power plant emergency core cooling system according to claim 1, characterized in that: It also includes a first circulation pipeline, which is connected between the outlet end of the heat exchange device and the pressure-suppressing water tank.

9. The nuclear power plant emergency core cooling system according to claim 1, characterized in that: It also includes a second circulation pipeline, which is connected between the inlet end of the low-pressure injection pump and the outlet end of the heat exchange device.

10. A cooling method applied to the emergency core cooling system of a nuclear power plant according to any one of claims 1 to 9, characterized in that, The method includes: Under design baseline accident conditions, when a breach accident occurs and a high containment pressure signal is triggered, the low-pressure injection unit is activated, the inlet of the low-pressure injection pump is connected to the pressure-suppressing water tank, and the outlet of the heat exchange device is connected to the spray device. Water is drawn from the pressure-suppressing water tank and injected into the spray device to perform the containment spray function. Under the design baseline accident conditions, when a non-breakage accident occurs, the low-pressure safety injection unit is activated, the inlet end of the low-pressure safety injection pump is connected to the primary circuit hot section, and the outlet end of the heat exchange device is connected to the primary circuit cold section. Water is drawn from the primary circuit hot section and injected into the primary circuit cold section to perform the emergency waste heat discharge function. Under extended operating conditions, the low-pressure safety injection unit is activated, the inlet of the low-pressure safety injection pump is connected to the pressure-suppressing water tank, and the outlet of the heat exchange device is connected to the primary cold circuit section. Water is drawn from the pressure-suppressing water tank and injected into the primary cold circuit section to perform the safety injection function.

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