Debugging system and debugging method for medium-and-long-term heat extraction system under severe accident condition of nuclear power station

Abstract

The invention relates to the field of nuclear power, in particular to a debugging system and a debugging method for a medium-and-long-term heat extraction system under severe accident conditions of a nuclear power station. According to the debugging system, a cooling water pipeline of the cooling water side medium-and-long-term heat extraction system is connected with a cooling water side pipeline of an original equipment cooling system in parallel. A steam pipeline of the steam generator secondary side passive cooling system is connected with a main steam pipeline of the steam generator, and a condensed water pipeline is connected with a water supply pipeline of the steam generator; and the passive cooling system heat exchanger is respectively connected with a steam pipeline and a condensed water pipeline. The debugging method comprises the steps of debugging the medium-and-long-term heat removal system on the cooling water side and debugging the passive cooling system on the secondary side of the steam generator. According to the method, the debugging work cost and the debugging work time of the medium-and-long-term heat extraction system are greatly reduced, and meanwhile, the method meets the requirements of environmental protection, energy conservation and emission reduction.

Description

Technical Field

[0001] The present invention relates to the field of nuclear power, and in particular to a debugging system and a debugging method for a medium- and long-term heat removal system under severe accident conditions in a nuclear power plant. Background Art

[0002] Under severe accident conditions, the heat removal capacity of nuclear power plants is very important. Most operating power plants increase their ability to cope with severe accidents by adding emergency water replenishment facilities, emergency diesel engines and mobile power supplies. For new nuclear power plants built after a nuclear power plant accident, some new systems were added during the design phase. These systems can remove the heat from the spent pool in severe accident conditions in active or passive ways, greatly increasing the power plant's ability to cope with severe accidents.

[0003] The medium- and long-term heat removal system used by nuclear power plants is mainly to export the heat of equipment and spent pools to the air through a new system in severe accident conditions, such as tsunamis and earthquakes that cause the loss of seawater used for equipment cooling. In severe accident conditions, only the heat of related systems and equipment such as spent pools needs to be exported, and this heat is much lower than the heat that needs to be exported during normal operation. This makes it possible to export waste heat for important equipment such as spent pools through mechanical ventilation cooling towers under extreme conditions.

[0004] In order to save the cost of the newly added medium- and long-term heat removal systems of nuclear power plants, these systems usually use the existing equipment cooling water system pipelines of nuclear power plants to directly connect the newly added medium- and long-term heat removal systems with some important users of the equipment cooling water system, and replace the equipment cooling water system to cool the important heat sources such as the spent pool under extreme accident conditions. The other side is cooled by mechanical ventilation cooling towers, which replace important plant water systems under extreme accident conditions (such as loss of seawater), while reducing dependence on water sources such as seawater during extreme accidents, and meeting the heat removal needs of nuclear power plants under severe accident conditions.

[0005] The addition of these new medium- and long-term heat removal systems under severe accident conditions has forced nuclear power plants to increase commissioning plans and commissioning work for medium- and long-term heat removal systems during the installation and commissioning phase. To verify the heat removal capacity of these new systems, it is usually necessary to verify them under sufficient heat sources. During the installation and commissioning phase of the unit, there are very few high-power heat-releasing equipment or conditions, so it is necessary to purchase external heat sources, such as external boiler equipment, for the commissioning of these new systems. These external heat sources require a large amount of additional costs, which greatly increases the commissioning cost of new power plants. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a debugging system and a debugging method for a medium- and long-term heat removal system under severe accident conditions in a nuclear power plant, which greatly reduces the debugging cost and time required for the medium- and long-term heat removal system, and at the same time, the method takes into account the requirements of environmental protection and energy conservation and emission reduction.

[0007] The present invention provides a debugging system for a medium- and long-term heat removal system under severe accident conditions in a nuclear power plant, wherein the cooling water pipeline of the medium- and long-term heat removal system on the cooling water side is connected in parallel with the cooling water side pipeline of the original equipment cooling system;

[0008] The steam pipeline of the passive cooling system on the secondary side of the steam generator is connected to the main steam pipeline of the steam generator, and the condensate pipeline is connected to the feed water pipeline of the steam generator;

[0009] The passive cooling system heat exchanger is connected to the steam pipeline and the condensate pipeline respectively.

[0010] In a specific embodiment of the present invention, the waste heat removal system is connected to a circuit, and includes a waste heat removal pump and a waste heat removal system heat exchanger.

[0011] In the cooling water side medium- and long-term heat removal system, the cooling water pipeline is connected to one side of the cooling water heat exchanger of the medium- and long-term heat removal system, and forms a first circulation loop with the waste heat removal system heat exchanger.

[0012] The other side of the cooling water heat exchanger of the medium- and long-term heat rejection system forms a second circulation loop with the ventilation cooling tower fan through a pipeline.

[0013] In a specific embodiment of the present invention, the original equipment cooling system includes a heat exchanger and connecting pipelines, and forms a third circulation loop with the heat exchanger of the waste heat removal system.

[0014] The cold water output by the heat exchanger realizes heat exchange in the waste heat removal system heat exchanger, and the hot water obtained by the heat exchange returns to the heat exchanger, realizes heat exchange again in the heat exchanger, and the cold water with exchanged heat enters the waste heat removal system heat exchanger again.

[0015] In a specific embodiment of the present invention, in the first circulation loop, the pipelines on both sides of the waste heat removal pump are respectively provided with a first valve and a fourth valve;

[0016] In the second circulation loop, a second valve and a third valve are respectively provided on the pipelines on both sides of the cooling water heat exchanger of the medium- and long-term heat rejection system.

[0017] In a specific embodiment of the present invention, the steam pipeline is also connected to a nitrogen pipeline, a fifth valve is provided on the steam pipeline, a sixth valve is provided on the condensate pipeline, and a seventh valve is provided on the nitrogen pipeline.

[0018] The present invention provides a method for debugging a medium- and long-term heat removal system under a severe accident condition of a nuclear power plant, including: debugging a medium- and long-term heat removal system on a cooling water side and debugging a passive cooling system on a secondary side of a steam generator;

[0019] The debugging of the medium- and long-term heat removal system on the cooling water side includes the following steps:

[0020] Step 1-1: In the late stage of the hot test of the nuclear power plant unit, when the unit is in a down state, the primary circuit temperature is gradually reduced to the operating temperature of the residual heat removal system or as close as possible to the upper limit of the spent pool cooling temperature under severe accident conditions through the steam generator to simulate the actual operating conditions;

[0021] Step 1-2: When the temperature of the primary circuit drops to the temperature at which the waste heat removal system is put into operation, the waste heat removal system is put into operation and the waste heat removal pump is started;

[0022] Step 1-3: When the temperature of the primary loop approaches the designed maximum temperature of the spent pool under severe accident conditions, close the third circulation loop pipeline, open the cooling water pipeline of the medium- and long-term heat removal system on the cooling water side, and realize heat exchange between the cooling water pipeline of the medium- and long-term heat removal system on the cooling water side and the heat exchanger of the waste heat removal system;

[0023] Step 1-4: Check the temperature change of the primary circuit, check the inlet and outlet temperatures of the heat exchanger of the waste heat removal system, check the temperature of the medium- and long-term heat removal system on the cooling water side and the operation of the equipment;

[0024] The commissioning of the steam generator secondary side passive cooling system comprises the following steps:

[0025] Step 2-1: Use main steam to provide heat for the passive cooling system on the secondary side of the steam generator;

[0026] Step 2-2: Monitor the water level change and primary circuit temperature of the steam generator;

[0027] Step 2-3: Determine the heat transfer efficiency of the passive cooling system heat exchanger by calculating the heat release of the main pump, steam pipeline flow, condensate flow, and temperature.

[0028] In a specific embodiment of the present invention, the step 1-1 further includes:

[0029] Filling the first circulation loop and the second circulation loop with water and exhausting the air;

[0030] Establishing circulating cooling water for the first circulation loop and the second circulation loop;

[0031] Start the ventilation cooling tower fan;

[0032] Confirm that all equipment in the medium- and long-term heat removal system on the cooling water side starts up without abnormalities and that circulating cooling water has been established.

[0033] In a specific embodiment of the present invention, the steps 1-2 further include:

[0034] Close the atmospheric release valve and transfer as much heat as possible generated by the main pump to the medium- and long-term heat removal system on the cold water side through the waste heat removal system heat exchanger.

[0035] In a specific embodiment of the present invention, before commissioning the steam generator secondary side passive cooling system,

[0036] Perform nitrogen filling maintenance on steam pipelines of passive cooling system heat exchangers;

[0037] Fill the condensate pipeline of the passive cooling system heat exchanger with desalted water.

[0038] In a specific embodiment of the present invention, the step 2-1 specifically includes:

[0039] During the unit hot test, confirm that the primary circuit temperature is close to the actual operating temperature and close the atmospheric release valve;

[0040] Use the main steam to discharge the nitrogen in the steam pipeline;

[0041] The main steam is used to provide heat for the passive cooling system on the secondary side of the steam generator.

[0042] Compared with the prior art, the debugging system and debugging method of the medium- and long-term heat removal system under severe accident conditions of a nuclear power plant of the present invention have the following beneficial effects:

[0043] (1) A debugging method for a new medium- and long-term heat removal system in a nuclear power plant is proposed. This method combines the debugging work of the medium- and long-term heat removal system with the original debugging work of the power plant. There is no need to create additional test conditions for the medium- and long-term heat removal system, which greatly saves the debugging time of the new medium- and long-term heat removal system in the nuclear power plant. By using this method, during the hot test of the nuclear power plant, this test can be completed in 10-12 hours. If the external heat source method is used, due to the large amount of preparation work, it will take 5-7 days to complete this test. Therefore, this method can save 4-6 days in the unit commissioning period.

[0044] (2) There is no need to purchase additional heat sources and install them for the commissioning of the medium- and long-term heat removal system, which reduces the equipment cost and labor cost of the commissioning of the medium- and long-term heat removal system. Taking a million-kilowatt pressurized water reactor as an example, it can save 500,000 yuan in equipment costs and save 4-6 days of work for two system engineers.

[0045] (3) By making full use of the pipelines between the newly added system and the original system of the power plant, the heat generated by the main pump during the hot function test of the nuclear power plant can be introduced into the newly added system to truly test the heat exchange capacity of the newly added system, making the test results more accurate;

[0046] (4) The heat generated by the hot functional test of the nuclear power plant is cleverly utilized, and no additional heat sources such as boilers are used to debug the medium- and long-term heat removal system, which has the advantages of energy saving and environmental protection. At the same time, this patented method helps to promote the transformation of commercial power plants on the original basis, adding medium- and long-term heat removal systems to enhance the ability of power plants to cope with severe accident conditions, and help pressurized water reactor nuclear power plants develop in a safer and more environmentally friendly direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic diagram showing the structure of the commissioning system of the medium- and long-term heat removal system under severe accident conditions of a nuclear power plant;

[0048] In the figure, 1-reactor, 2-steam generator, 3-main pump, 4-waste heat removal pump, 5-waste heat removal system heat exchanger, 6-original equipment cooling water heat exchanger, 7-cooling water pipeline inlet, 8-cooling water pipeline outlet, 9-medium and long-term heat removal system cooling water heat exchanger, 10-circulation pump, 11-mechanical ventilation cooling water circulation pump, 12-ventilation cooling tower fan, 13-first valve, 14-second valve, 15-third valve, 16-fourth valve, 17-fifth valve, 18-sixth valve, 19-passive cooling system heat exchanger, 20-seventh valve. DETAILED DESCRIPTION

[0049] In order to further understand the present invention, the embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the present invention.

[0050] In the present invention, the medium- and long-term heat removal system includes a medium- and long-term heat removal system on the cooling water side and a passive cooling system on the secondary side of the steam generator.

[0051] This method uses the characteristics of the medium- and long-term heat removal system of a nuclear power plant being connected to the original equipment cooling water pipeline of the power plant in terms of system layout. During the hot test phase of the nuclear power plant, the main pump is usually kept running continuously to simulate the actual operation state of the unit. The primary circuit equipment of a nuclear power plant, such as the main pump, generates a large amount of heat during operation, causing the medium in the primary circuit pipeline to be continuously heated. This part of the heat can be transferred to the secondary circuit through the steam generator and discharged through the atmospheric release valve. The method provided by the present invention is to use this part of the heat for the debugging of the medium- and long-term heat removal system, thereby replacing the external heat source.

[0052] The embodiment of the present invention discloses a debugging system for a medium- and long-term heat removal system under severe accident conditions of a nuclear power plant, such as Figure 1 As shown,

[0053] The cooling water pipeline of the medium- and long-term heat removal system on the cooling water side is connected in parallel with the cooling water pipeline of the original equipment cooling system;

[0054] The waste heat removal system is connected to a primary circuit and includes a waste heat removal pump 4 and a waste heat removal system heat exchanger 5.

[0055] In the cooling water side medium- and long-term heat removal system, the cooling water pipeline is connected to one side of the cooling water heat exchanger 9 of the medium- and long-term heat removal system, and forms a first circulation loop with the waste heat removal system heat exchanger 5.

[0056] In the first circulation loop, a second valve 14 and a third valve 15 are respectively provided on the pipelines on both sides of the cooling water heat exchanger 9 of the medium- and long-term heat rejection system.

[0057] The original equipment cooling system includes a heat exchanger and connecting pipelines, wherein the heat exchanger is the original equipment cooling water heat exchanger 6; one end of the original equipment cooling water heat exchanger 6 is a cooling water pipeline inlet 7, and the other end is a cooling water pipeline outlet 8;

[0058] The heat exchanger and the waste heat removal system heat exchanger 5 form a third circulation loop.

[0059] In the third circulation loop, the pipelines on both sides of the waste heat discharge pump 4 are respectively provided with a first valve 13 and a fourth valve 16;

[0060] The cold water output by the heat exchanger realizes heat exchange in the waste heat discharge system heat exchanger 5, and the hot water obtained by the heat exchange returns to the heat exchanger, realizes heat exchange again in the heat exchanger, and the cold water after the heat exchange enters the waste heat discharge system heat exchanger 5 again.

[0061] The other side of the cooling water heat exchanger 9 of the medium- and long-term heat rejection system forms a second circulation loop with the ventilation cooling tower fan 12 through a pipeline.

[0062] The second circulation loop is provided with a mechanical ventilation cooling water circulation pump 11 .

[0063] The primary circuit consists of a reactor 1, a steam generator 2, a main pump 3 and connecting pipelines.

[0064] The heat generated by the first circuit is given to the waste heat removal system, and the heat received by the waste heat removal system undergoes heat exchange at the waste heat removal system heat exchanger 5, and the heat after heat exchange is transferred out through the third circulation circuit; or the first valve 13 and the fourth valve 16 on the third circuit are closed to ensure that the heat discharged by the waste heat removal system heat exchanger 5 is all transferred to the medium- and long-term heat removal system on the cooling water side, and then dissipated into the air through the cooling tower; that is, it is dissipated into the air through the first circulation circuit and the second circulation circuit.

[0065] The steam pipeline of the passive cooling system on the secondary side of the steam generator is connected to the main steam pipeline of the steam generator, and the condensate pipeline is connected to the feed water pipeline of the steam generator;

[0066] The passive cooling system heat exchanger 19 is connected to the steam pipeline and the condensate pipeline respectively.

[0067] The steam pipeline is also connected to a nitrogen pipeline. A fifth valve 17 is provided on the steam pipeline. A sixth valve 18 is provided on the condensate pipeline. A seventh valve 20 is provided on the nitrogen pipeline.

[0068] Based on the above debugging system, the embodiment of the present invention also discloses a debugging method for a medium- and long-term heat removal system under a severe accident condition of a nuclear power plant, including: debugging of a medium- and long-term heat removal system on the cooling water side and debugging of a passive cooling system on the secondary side of a steam generator;

[0069] The debugging of the medium- and long-term heat removal system on the cooling water side includes the following steps:

[0070] Step 1-1: Installation and preparation:

[0071] During the design phase or later modification of a nuclear power plant, the cooling water pipeline of the medium- and long-term heat removal system is connected to the cooling water pipeline of the equipment originally designed for the power plant.

[0072] The connection point should be selected to ensure that the heat exchanger 5 of the waste heat removal system can be directly or indirectly cooled by the cooling water of the medium and long-term heat removal system, that is, to meet the requirements of the following figure. Figure 1 Require.

[0073] Filling the first circulation loop and the second circulation loop with water and exhausting the air;

[0074] Establish circulating cooling water for the first circulation loop and the second circulation loop; specifically, start the circulation pump 10 and the mechanical ventilation cooling water circulation pump 11;

[0075] Start the ventilation cooling tower fan 12;

[0076] Confirm that all equipment in the medium- and long-term heat removal system on the cooling water side starts up without abnormalities and that circulating cooling water has been established.

[0077] Step 1-2: In the late stage of the hot test of the nuclear power plant unit, when the unit is in a down state, the primary circuit temperature is gradually reduced to the operating temperature of the residual heat removal system or as close as possible to the upper limit of the spent pool cooling temperature under severe accident conditions through the steam generator 2 to simulate the actual operating conditions;

[0078] Step 1-3: When the temperature of the primary circuit drops to the temperature at which the waste heat removal system is put into operation, the waste heat removal system is put into operation and the waste heat removal pump 4 is started;

[0079] Step 1-4: When the temperature of the primary circuit approaches the designed maximum temperature of the spent pool under severe accident conditions, close the first valve 13 and the fourth valve 16, and open the second valve 14 and the third valve 15 at the same time, so that heat exchange is achieved between the cooling water pipeline of the medium- and long-term heat removal system on the cooling water side and the heat exchanger 5 of the waste heat removal system;

[0080] That is, the cooling water of the waste heat removal system heat exchanger 5 is changed from the original equipment cooling water system cooling to the medium- and long-term heat removal system cooling water cooling;

[0081] Step 1-5: Close the atmospheric release valve in the secondary circuit, and transfer as much heat generated by the main pump 3 as possible to the medium- and long-term heat removal system through the waste heat removal system heat exchanger;

[0082] Step 1-6: Check the temperature change of the primary circuit, check the inlet and outlet temperatures of the heat exchanger 5 of the waste heat removal system, check the temperature of the medium- and long-term heat removal system on the cooling water side and the operation of the equipment;

[0083] The commissioning of the steam generator secondary side passive cooling system comprises the following steps:

[0084] Step 2-1: Installation and preparation:

[0085] During the design phase or later modification of a nuclear power plant, the steam pipeline of the passive cooling system on the secondary side of the steam generator is connected to the main steam pipeline, and the condensate pipeline is connected to the feed water pipeline;

[0086] Fill the pipeline from the passive cooling system heat exchanger 17 to the sixth valve 18 with deionized water;

[0087] Fill the section from the fifth valve 17 to the passive cooling system heat exchanger 17 with nitrogen;

[0088] Step 2-2: During the unit hot test, confirm that the primary circuit temperature is close to the actual operating temperature and close the atmospheric release valve;

[0089] Step 2-2: Open the fifth valve 17 and the seventh valve 20 at the same time to discharge the nitrogen in the pipeline;

[0090] Step 2-2: Open the sixth valve 18 after a period of time;

[0091] Step 2-2: monitor the water level change and primary circuit temperature of the steam generator 2;

[0092] Step 2-3: Determine the heat transfer efficiency of the passive cooling system heat exchanger 19 by calculating the heat release of the main pump, the steam pipeline flow, the condensate flow, and the temperature.

[0093] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0094] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A debugging system for a medium- and long-term heat removal system under severe accident conditions in a nuclear power plant, characterized in that: The cooling water pipeline of the medium- and long-term heat removal system on the cooling water side is connected in parallel with the cooling water pipeline of the original equipment cooling system; The steam pipeline of the passive cooling system on the secondary side of the steam generator is connected to the main steam pipeline of the steam generator, and the condensate pipeline is connected to the feed water pipeline of the steam generator; The passive cooling system heat exchanger is connected to the steam pipeline and the condensate pipeline respectively.

2. The debugging system of the medium- and long-term heat removal system under severe accident conditions of a nuclear power plant according to claim 1, characterized in that: The waste heat removal system is connected to a primary circuit and includes a waste heat removal pump and a waste heat removal system heat exchanger. In the cooling water side medium- and long-term heat removal system, the cooling water pipeline is connected to one side of the cooling water heat exchanger of the medium- and long-term heat removal system, and forms a first circulation loop with the waste heat removal system heat exchanger. The other side of the cooling water heat exchanger of the medium- and long-term heat rejection system forms a second circulation loop with the ventilation cooling tower fan through a pipeline.

3. The debugging system of the medium- and long-term heat removal system under severe accident conditions of a nuclear power plant according to claim 2, characterized in that: The original equipment cooling system includes a heat exchanger and connecting pipelines, which form a third circulation loop with the heat exchanger of the waste heat removal system. The cold water output by the heat exchanger realizes heat exchange in the waste heat removal system heat exchanger, and the hot water obtained by the heat exchange returns to the heat exchanger, realizes heat exchange again in the heat exchanger, and the cold water with exchanged heat enters the waste heat removal system heat exchanger again.

4. The debugging system of the medium- and long-term heat removal system under severe accident conditions of a nuclear power plant according to claim 1, characterized in that: On the first circulation loop, the pipelines on both sides of the waste heat discharge pump are respectively provided with a first valve and a fourth valve; In the second circulation loop, a second valve and a third valve are respectively provided on the pipelines on both sides of the cooling water heat exchanger of the medium- and long-term heat rejection system.

5. The debugging system of the medium- and long-term heat removal system under severe accident conditions of a nuclear power plant according to claim 1, characterized in that: The steam pipeline is also connected to a nitrogen pipeline. A fifth valve is arranged on the steam pipeline. A sixth valve is arranged on the condensate pipeline. A seventh valve is arranged on the nitrogen pipeline.

6. A method for debugging a medium- and long-term heat removal system under severe accident conditions in a nuclear power plant, characterized in that: include: Debugging of the medium- and long-term heat removal system on the cooling water side and the passive cooling system on the secondary side of the steam generator; The debugging of the medium- and long-term heat removal system on the cooling water side includes the following steps: Step 1-1: In the late stage of the hot test of the nuclear power plant unit, when the unit is in a down state, the primary circuit temperature is gradually reduced to the operating temperature of the residual heat removal system or as close as possible to the upper limit of the spent pool cooling temperature under severe accident conditions through the steam generator to simulate the actual operating conditions; Step 1-2: When the temperature of the primary circuit drops to the temperature at which the waste heat removal system is put into operation, the waste heat removal system is put into operation and the waste heat removal pump is started; Step 1-3: When the temperature of the primary loop approaches the designed maximum temperature of the spent pool under severe accident conditions, close the third circulation loop pipeline, open the cooling water pipeline of the medium- and long-term heat removal system on the cooling water side, and realize heat exchange between the cooling water pipeline of the medium- and long-term heat removal system on the cooling water side and the heat exchanger of the waste heat removal system; Step 1-4: Check the temperature change of the primary circuit, check the inlet and outlet temperatures of the heat exchanger of the waste heat removal system, check the temperature of the medium- and long-term heat removal system on the cooling water side and the operation of the equipment; The commissioning of the steam generator secondary side passive cooling system comprises the following steps: Step 2-1: Use main steam to provide heat for the passive cooling system on the secondary side of the steam generator; Step 2-2: Monitor the water level change and primary circuit temperature of the steam generator; Step 2-3: Determine the heat transfer efficiency of the passive cooling system heat exchanger by calculating the heat release of the main pump, steam pipeline flow, condensate flow, and temperature.

7. The method for debugging a medium- and long-term heat removal system under severe accident conditions of a nuclear power plant according to claim 6, characterized in that: The step 1-1 also includes: Filling the first circulation loop and the second circulation loop with water and exhausting the air; Establishing circulating cooling water for the first circulation loop and the second circulation loop; Start the ventilation cooling tower fan; Confirm that all equipment in the medium- and long-term heat removal system on the cooling water side starts up without abnormalities and that circulating cooling water has been established.

8. The method for debugging a medium- and long-term heat removal system under severe accident conditions of a nuclear power plant according to claim 6, characterized in that: The steps 1-2 further include: Close the atmospheric release valve and transfer as much heat as possible generated by the main pump to the medium- and long-term heat removal system on the cold water side through the waste heat removal system heat exchanger.

9. The method for debugging a medium- and long-term heat removal system under severe accident conditions of a nuclear power plant according to claim 6, characterized in that: Before commissioning the steam generator secondary side passive cooling system, Perform nitrogen filling maintenance on steam pipelines of passive cooling system heat exchangers; Fill the condensate pipeline of the passive cooling system heat exchanger with desalted water.

10. The method for debugging a medium- and long-term heat removal system under severe accident conditions of a nuclear power plant according to claim 9, characterized in that: The step 2-1 specifically includes: During the unit hot test, confirm that the primary circuit temperature is close to the actual operating temperature and close the atmospheric release valve; Use the main steam to discharge the nitrogen in the steam pipeline; The main steam is used to provide heat for the passive cooling system on the secondary side of the steam generator.

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