An offline water charging and discharging system for nuclear power emergency diesel generator set and a control method thereof

Abstract

This invention relates to an offline charging and draining system and control method for nuclear power emergency diesel generator sets. The system includes a water treatment tank located at the lowest point of the system; an expansion tank located at the highest point of the system, with a vent at its upper end; and a water treatment pump for drawing coolant from the water treatment tank and delivering it to a target location via a pipeline system. When coolant is initially added to the expansion tank and the equipment, the water treatment pump sequentially injects the coolant from the water treatment tank into the heat exchange system and the expansion tank from bottom to top. When coolant needs to be added to the expansion tank during equipment operation, the water treatment pump directly injects the coolant from the water treatment tank into the expansion tank. The equipment is located at a height between the water treatment tank and the expansion tank. The system and control method of this invention can switch between different pipeline system states, meeting the needs of charging and draining water under different conditions, and are safe and reliable.

Description

Technical Field

[0001] This invention relates to the field of nuclear power water cooling system technology, specifically to an offline charging and draining system and control method for nuclear power emergency diesel generator sets. Background Technology

[0002] Emergency diesel generator sets in nuclear power plants are the ultimate safety guarantee, playing a crucial role in providing emergency power to the nuclear reactor when external power sources fail. They are the "last line of defense." To ensure that the units are always in a hot standby state, their cooling water systems must maintain stable and reliable operation. Offline filling and draining systems are an important component in ensuring the timeliness of emergency diesel generator sets during maintenance, commissioning, and nuclear safety response.

[0003] Traditional water filling and draining systems place the water treatment tank on a high floor, and the water replenishment method involves pumping water from the water treatment tank to the expansion tank. This top-down replenishment method from the expansion tank easily causes air bubbles to form in the cooling water system, reducing the system's heat exchange efficiency. Furthermore, traditional water treatment tanks have small design capacities and cannot collect the entire cooling water system's discharge. In addition, the traditional water treatment pump replenishment to the expansion tank is controlled locally. By monitoring the expansion tank's liquid level in the central control room, the water treatment pump is manually started to replenish the expansion tank when the liquid level is low, and manually shut off when the liquid level is high. This requires constant monitoring by personnel, is labor-intensive, and lacks flexibility and convenience. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an offline filling and draining system and control method for nuclear power emergency diesel generator sets. This system enables switching of pipeline systems in different states to meet the filling and draining needs under different conditions. It is applicable to preheating systems of emergency diesel generator sets for nuclear power plants or other diesel generator sets with high reliability requirements.

[0005] The technical objective of this invention is achieved through the following technical solution: This invention provides an offline charging and draining system for nuclear power emergency diesel generator sets, comprising: The water treatment tank is used to store coolant and supply coolant to the expansion tank when the liquid level in the expansion tank is lower than a set value. The water treatment tank is located at the lowest point of the system; a vent is also provided at the top of the water treatment tank. An expansion tank is used to store coolant and supply coolant to the heat exchange system of the equipment for heat exchange to reduce the operating temperature of the equipment. The expansion tank is located at the highest point of the system and has a vent at the top. The water treatment pump is used to extract coolant from the water treatment tank and deliver it to the target location through the pipeline system. When the expansion tank and equipment are initially filled with coolant, the water treatment pump injects the coolant from the water treatment tank into the heat exchange system and expansion tank of the equipment from bottom to top. When the equipment is running and needs to be filled with coolant into the expansion tank, the water treatment pump injects the coolant from the water treatment tank directly into the expansion tank. The equipment is located at a height between the water treatment tank and the expansion tank.

[0006] Furthermore, a pump suction port is provided at the bottom of the water treatment tank; The expansion tank has a system water inlet at the bottom and a water outlet at the top. A first pipeline system connects the pump inlet and the equipment's heat exchange system, and the water treatment pump is connected to the first pipeline system. A second pipeline system is connected between the heat exchange system and the system water inlet of the equipment. The second pipeline system is used to add coolant to the expansion tank before the equipment is put into operation and to replenish the heat exchange system of the equipment by gravity during the operation of the equipment. The first pipeline system is connected to a third pipeline system at the output end of the water treatment pump. A third pipeline interface is provided on the first pipeline system at the output end of the water treatment pump. One end of the third pipeline system is connected to the third pipeline interface, and the other end of the third pipeline system is connected to the expansion tank inlet to replenish coolant into the expansion tank during system operation.

[0007] Furthermore, a system drain return port is provided at the upper end of the water treatment tank. A fourth pipeline system is connected between the system drain return port and the first pipeline system. A fourth pipeline interface is provided on the first pipeline system at the output end of the water treatment pump. The fourth pipeline interface is located at the rear end of the third pipeline interface. One end of the fourth pipeline system is connected to the system drain return port, and the other end of the fourth pipeline system is connected to the fourth pipeline interface. The fourth pipeline system is used to drain and return the coolant to the water treatment tank.

[0008] Furthermore, a fifth pipeline interface is provided between the third and fourth pipeline interfaces on the first pipeline system. The fifth pipeline interface is connected to a fifth pipeline system for adding coolant to the water treatment tank and discharging coolant. The fifth pipeline system is indirectly connected to the fourth pipeline system through the first pipeline system.

[0009] Furthermore, the expansion tank is equipped with an expansion tank overflow port at the top, and the water treatment tank is equipped with an overflow return port at the top. A sixth pipeline system is connected between the expansion tank overflow port and the overflow return port. The sixth pipeline system is used to return the overflow coolant in the expansion tank to the water treatment tank.

[0010] Furthermore, a fifth control valve, a sixth control valve, and a third control valve are installed on the first pipeline system; the fifth control valve is located between the pump suction port and the input end of the water treatment pump, the sixth control valve is located between the output end of the water treatment pump and the third pipeline interface, and the third control valve is located between the fourth pipeline interface and the heat exchange system of the equipment; a first control valve is installed on the third pipeline system; a second control valve is installed on the fourth pipeline system; and a fourth control valve is installed on the fifth pipeline system.

[0011] Furthermore, a check valve is installed on the first pipeline system between the output end of the water treatment pump and the third pipeline interface to prevent coolant from flowing back into the water treatment pump.

[0012] Furthermore, the design capacity of the water treatment tank is greater than the sum of the expansion tank capacity, the liquid storage capacity of the equipment's heat exchange system, the liquid storage capacity of the pipeline, and the amount of coolant used to replenish the expansion tank during system operation; the design capacity of the expansion tank is greater than the volume change of the coolant in the system as it rises from a low temperature to the highest temperature.

[0013] Furthermore, the water treatment tank is also equipped with a first liquid level monitoring device for monitoring the liquid level inside the water treatment tank, and the expansion tank is also equipped with a second liquid level monitoring device for monitoring the liquid level inside the expansion tank.

[0014] This invention also provides a control method for an offline charging and draining system for a nuclear power emergency diesel generator set, the method comprising: When the water treatment tank is filled with water for the first time, the second, fourth, fifth, and sixth control valves are opened, the first and third control valves are closed, the fifth pipeline system is connected to the fourth pipeline system, and coolant is injected into the water treatment tank through the fifth pipeline system. When the liquid level in the water treatment tank reaches the set high level, the fourth control valve is closed. Before the system is started, the water treatment pump is started. The coolant in the water treatment tank flows along the first pipeline system to the fourth pipeline system and then flows back to the water treatment tank to achieve coolant homogenization. When the expansion tank and equipment heat exchange system are first filled with coolant, the third, fifth and sixth control valves are opened, and the first, second and fourth control valves are closed. The water treatment pump is started, and the coolant in the water treatment tank flows along the first pipeline system to the equipment heat exchange system, and then from the equipment heat exchange system to the expansion tank through the second pipeline system. When the liquid level in the expansion tank reaches the set high level, the water treatment pump is turned off and the third control valve is closed. During equipment operation, the first, fifth, and sixth control valves remain normally open, while the second, third, and fourth control valves remain normally closed. When the coolant in the equipment's heat exchange system decreases, the expansion tank automatically replenishes the coolant to the heat exchange system by gravity. When the liquid level in the expansion tank falls below the set low level, the water treatment pump starts, and coolant is supplied to the expansion tank from the first and third pipeline systems until the liquid level in the expansion tank reaches the set high level. During equipment maintenance, the second, third, fifth, and sixth control valves are opened, while the first and fourth control valves are closed, allowing the coolant in the expansion tank and the coolant in the equipment's heat exchange system to flow back into the water treatment tank. When the coolant in the water treatment tank needs to be drained, the fourth, fifth, and sixth control valves open, while the first, second, and third control valves close, and the water treatment pump starts to drain the coolant in the water treatment tank through the first and fifth pipeline systems.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In the nuclear power emergency diesel generator set offline charging and draining system of the present invention, when water is initially supplied to the expansion tank and equipment, water is supplied from bottom to top to the equipment through the water treatment tank, and then water is supplied from bottom to top to the expansion tank through the equipment. The generated air bubbles are discharged from the vent at the top of the expansion tank, so as to avoid generating a large number of air bubbles in the heat exchange system of the equipment when supplying water to the equipment, thereby reducing the heat exchange efficiency.

[0016] 2. The offline charging and draining system for nuclear power emergency diesel generator sets of the present invention can also achieve homogenization of coolant in the water treatment tank by adjusting the control valve and with the help of the water treatment pump, so that the different substances in the coolant are mixed more evenly.

[0017] 3. In the process of using the nuclear power emergency diesel generator set offline charging and draining system of the present invention, once the coolant in the equipment decreases, the coolant in the expansion tank can automatically compensate for the coolant by its own gravity, which is more energy-efficient and reliable.

[0018] 4. The present invention can realize automatic monitoring of liquid level through the first liquid level monitoring device and the second liquid level monitoring device, and the liquid level monitoring is more timely.

[0019] 5. The present invention can also return the overflowing coolant in the expansion tank to the water treatment tank through the sixth pipeline system. When the liquid level in the expansion tank exceeds the set maximum liquid level, but the system continues to supply coolant to the expansion tank due to faults or other factors, the excess coolant will be returned to avoid coolant waste and avoid overload in the expansion tank.

[0020] 6. The use of the offline filling and draining system for nuclear power emergency diesel generator sets of the present invention can meet the needs of adding and recovering coolant in equipment, expansion tank and pipeline during equipment maintenance, which is convenient for maintenance and can also recover and reuse the returned coolant. Attached Figure Description

[0021] Figure 1 A schematic diagram of the offline charging and draining system for nuclear power emergency diesel generator sets of the present invention.

[0022] Figure 2 This is a schematic diagram of the pipeline connection when the water treatment tank is filled with water for the first time in an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram of the pipeline connection when the coolant circulates in the water treatment tank in an embodiment of the present invention.

[0024] Figure 4 This is a schematic diagram of the pipeline connection when adding coolant to the expansion tank and equipment for the first time in an embodiment of the present invention.

[0025] Figure 5 This is a schematic diagram of pipeline connection during the operation of the equipment in an embodiment of the present invention.

[0026] Figure 6 This is a schematic diagram of the pipeline connection when the equipment needs maintenance and the coolant is flowing back in the current state.

[0027] Figure 7 This is a schematic diagram of the pipeline connection when the coolant in the water treatment tank is discharged in an embodiment of the present invention.

[0028] In the picture: 1. Water treatment tank; 2. Expansion tank; 3. Water treatment pump; 4. Equipment; 5. First pipeline system; 6. Second pipeline system; 7. Third pipeline system; 8. Fourth pipeline system; 9. Fifth pipeline system; 10. Sixth pipeline system; 11. Pump suction port; 12. System vent return port; 13. Overflow return port; 14. Vent; 15. Manhole; 16. First liquid level monitoring device; 21. Vent; 22. System water filling port; 23. Expansion tank water filling port; 24. Expansion tank overflow port; 25. Manhole; 26. Second liquid level monitoring device; 51. Third pipeline interface; 52. Fourth pipeline interface; 53. Fifth pipeline interface; 54. Fifth control valve; 55. Sixth control valve; 56. Third control valve; 57. Check valve; 71. First control valve; 81. Second control valve; 91. Fourth control valve. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to specific embodiments: An offline charging and draining system for nuclear power emergency diesel generator sets, such as Figure 1 As shown, it includes: Water treatment tank 1 is used to store coolant and supply coolant to the expansion tank when the liquid level in the expansion tank is lower than a set value. Water treatment tank 1 is arranged at the lowest point of the system. The upper end of water treatment tank 1 is also provided with vent 14 and manhole 15. For example, the coolant is a mixture of water and ethylene glycol.

[0030] Expansion tank 2 is used to store coolant and supply coolant to the heat exchange system of equipment 4 for heat exchange to reduce the operating temperature of the equipment. Expansion tank 2 is located at the highest point of the system and has a vent 21 at the top. More specifically, a manhole 25 is also provided at the top of the expansion tank. Water treatment pump 3 is used to extract coolant from water treatment tank 1 and deliver it to the target location through the pipeline system. When coolant is initially added to expansion tank 2 and equipment 4, water treatment pump 3 injects coolant from the water treatment tank into the heat exchange system of equipment 4 and expansion tank 2 sequentially from bottom to top. When equipment 4 is running and coolant needs to be added to expansion tank 2, water treatment pump 3 directly injects the coolant from water treatment tank 1 into expansion tank 2. The flow rate of water treatment pump 3 can be designed to fill the expansion tank in half an hour. The head of the water treatment pump is not less than the height difference between the expansion tank and the pump input end plus the hydraulic losses along the way. In one implementation process, the control mode of the water treatment pump adopts local / remote switching: local control mode is used when the system is initially filled with water, before formal operation, and during maintenance; remote control mode is used when the system is formally put into operation. Specifically, the start and stop of the water treatment pump can be controlled by the level sensor of the second liquid level monitoring device.

[0031] The equipment 4 is located at a height between the water treatment tank 1 and the expansion tank 2. The equipment includes, but is not limited to, an air-cooled radiator, a diesel engine, a plate heat exchanger, a temperature control valve, and pipelines between the equipment. Vent 21 and vent 14 can be in the form of a vent mast, with bends to prevent debris from entering; manhole 25 and manhole 15 are normally sealed with sealing plates, etc., and are only opened when personnel need to pass through.

[0032] More specifically, the bottom of the water treatment tank 1 is provided with a pump suction port 11; the bottom of the expansion tank 2 is provided with a system water filling port 22, and the top of the expansion tank 2 is provided with an expansion tank water filling port 23. A first pipeline system 5 is connected between the pump suction port 11 and the heat exchange system of the equipment 4, and the water treatment pump 3 is connected to the first pipeline system 5. A second pipeline system 6 is connected between the heat exchange system of equipment 4 and the system water inlet 22. The second pipeline system 6 is used to add coolant to the expansion tank 2 before the equipment is running and to replenish the heat exchange system of equipment 4 with coolant by gravity during the operation of the equipment. The first pipeline system 5 is also connected to the third pipeline system 7 at the output end of the water treatment pump 3. The first pipeline system 5 at the output end of the water treatment pump 3 is provided with a third pipeline interface 51. One end of the third pipeline system 7 is connected to the third pipeline interface 51, and the other end of the third pipeline system 7 is connected to the expansion tank water inlet 23 to replenish coolant into the expansion tank 23 during system operation.

[0033] The upper end of the water treatment tank 1 is provided with a system drain return port 12. A fourth pipeline system 8 is connected between the system drain return port 12 and the first pipeline system 5. A fourth pipeline interface 52 is provided on the first pipeline system 5 at the output end of the water treatment pump 3. The fourth pipeline interface 52 is located at the rear end of the third pipeline interface 51. One end of the fourth pipeline system 8 is connected to the system drain return port 12, and the other end of the fourth pipeline system 8 is connected to the fourth pipeline interface 52. The fourth pipeline system 8 is used to drain and return the coolant in the expansion tank, equipment and pipelines to the water treatment tank 1.

[0034] A fifth pipeline interface 53 is also provided on the first pipeline system 5 between the third pipeline interface 51 and the fourth pipeline interface 52. The fifth pipeline interface 53 is connected to a fifth pipeline system 9 for adding coolant to and discharging coolant from the water treatment tank 1. The fifth pipeline system 9 is indirectly connected to the fourth pipeline system 8 through the first pipeline system 5. For example, during filling, the fifth pipeline system is connected to a coolant supply end with a pressure of 3 to 5 bar. The coolant supply end is connected to the water treatment tank through the fifth pipeline system, the pipe section of the first pipeline system, and the fourth pipeline system, and supplies coolant with a pressure of 3 to 5 bar into the water treatment tank.

[0035] Preferably, the upper end of the expansion tank 2 is provided with an expansion tank overflow port 24, and the upper end of the water treatment tank 1 is provided with an overflow return port 13. A sixth pipeline system 10 is connected between the expansion tank overflow port 24 and the overflow return port 13. The sixth pipeline system 10 is used to return the coolant overflowing from the expansion tank 2 to the water treatment tank 1.

[0036] More specifically, a fifth control valve 54, a sixth control valve 55, and a third control valve 56 are provided on the first pipeline system 5; the fifth control valve 54 is located between the pump suction port 11 and the input end of the water treatment pump 3, the sixth control valve 55 is located between the output end of the water treatment pump 3 and the third pipeline interface 51, and the third control valve 56 is located between the fourth pipeline interface 52 and the heat exchange system of the equipment 4; a first control valve 71 is provided on the third pipeline system 7; a second control valve 81 is provided on the fourth pipeline system 8; and a fourth control valve 91 is provided on the fifth pipeline system 9.

[0037] Preferably, a check valve 57 is also provided on the first pipeline system 5 between the output end of the water treatment pump 3 and the third pipeline interface 51 to prevent coolant from flowing back into the water treatment pump 3. In one embodiment, the check valve 57 is located between the output end of the water treatment pump 3 and the sixth control valve 55.

[0038] Preferably, the water treatment tank 1 is further equipped with a first liquid level monitoring device 16 for monitoring the liquid level inside the water treatment tank 1, and the expansion tank 2 is further equipped with a second liquid level monitoring device 26 for monitoring the liquid level inside the expansion tank 2. Exemplarily, the first liquid level monitoring device 16 and the second liquid level monitoring device 26 are respectively employed as magnetic level gauges, each equipped with a liquid level sensor. When the liquid level in the water treatment tank 1 is lower than the set low liquid level or higher than the set high liquid level, the liquid level sensor of the first liquid level monitoring device can issue an alarm signal; similarly, when the liquid level in the expansion tank 2 is lower than the set low liquid level or higher than the set high liquid level, the liquid level sensor of the second liquid level monitoring device can issue an alarm signal; furthermore, the liquid level changes can be visually observed through the magnetic level gauges.

[0039] In one implementation process, when the liquid level in the expansion tank 2 is lower than the set low liquid level, the liquid level sensor of the second liquid level monitoring device 26 sends a control signal to the water treatment pump to start the water treatment pump 3; when the liquid level in the expansion tank 2 is higher than the set high liquid level, the liquid level sensor of the second liquid level monitoring device 26 sends a control signal to the water treatment pump 3 to shut down the water treatment pump 3.

[0040] Preferably, the design capacity of the water treatment tank 1 is greater than the expansion tank capacity 2, the liquid storage capacity of the heat exchange system of the equipment 4, the liquid storage capacity of the pipeline, and the amount of coolant replenished to the expansion tank 2 during the operation of all systems using coolant; the design capacity of the expansion tank 2 is greater than the volume change of the coolant volume in all systems using coolant as it rises from a low temperature to the highest temperature.

[0041] More specifically, the third control valve 56 has a nuclear safety rating, while the other control valves are not required to be nuclear-grade. The opening and closing of each valve in this application can be achieved through manual / remote control. For example, the first control valve 71, the second control valve 81, the third control valve 56, the fourth control valve 91, the fifth control valve 54, and the sixth control valve 55 are ball valves.

[0042] This invention also provides a control method for an offline charging and draining system for a nuclear power emergency diesel generator set, comprising: When filling the water treatment tank with water for the first time, if Figure 2 As shown, the second control valve 81, the fourth control valve 91, the fifth control valve 54, and the sixth control valve 55 are open, the first control valve 71 and the third control valve 56 are closed, the fifth pipeline system 9 is connected to the fourth pipeline system 8, and coolant is injected into the water treatment tank 1 through the fifth pipeline system 9; when the liquid level in the water treatment tank 1 reaches the set high level, the fourth control valve 91 is closed. Before the system runs, such as Figure 3 As shown, the water treatment pump 3 is manually started. At this time, the second control valve 81, the fourth control valve 91, the fifth control valve 54 and the sixth control valve 55 are kept open, while the first control valve 71, the third control valve 56 and the fourth control valve 91 are closed. The coolant in the water treatment tank 1 flows along the first pipeline system 5 to the fourth pipeline system 8 and then flows back to the water treatment tank to achieve coolant homogenization, so that the water and ethylene glycol are mixed more evenly. When the heat exchange system of expansion tank 2 and equipment 4 is first filled with coolant, if Figure 4 As shown, the third control valve 56, the fifth control valve 54, and the sixth control valve 55 are open, while the first control valve 71, the second control valve 81, and the fourth control valve 91 are closed. The water treatment pump 3 is manually started, and the coolant in the water treatment tank 1 flows along the first pipeline system 5 to the heat exchange system of the equipment 4, and then from the heat exchange system of the equipment 4 to the expansion tank 2 via the second pipeline system 6. When the liquid level in the expansion tank 2 reaches the set high level, the water treatment pump 3 is turned off and the third control valve 56 is closed. When the device is running, such as Figure 5 As shown, the first control valve 71, the fifth control valve 54, and the sixth control valve 55 remain normally open, while the second control valve 81, the third control valve 56, and the fourth control valve 91 remain normally closed. When the coolant in the heat exchange system of the equipment 4 decreases, the coolant in the expansion tank 2 is automatically replenished to the heat exchange system of the equipment 4 by gravity. When the liquid level in the expansion tank 2 is lower than the set low liquid level, the water treatment pump 3 starts. At this time, the water treatment pump 3 is controlled by the liquid level sensor of the second liquid level monitoring device, and the coolant is supplied to the expansion tank 2 by the first pipeline system 5 and the third pipeline system 7 until the liquid level in the expansion tank 2 reaches the set high liquid level.

[0043] When maintenance is required, the coolant in the system must be completely drained, such as... Figure 6 As shown, the third control valve 56, the second control valve 81, the fifth control valve 54 and the sixth control valve 55 are opened, and the first control valve 71 and the fourth control valve 91 are closed, so that the coolant in the expansion tank 2 flows to the heat exchange system of the equipment 4 along the second pipeline system, and the coolant in the heat exchange system of the equipment 4 flows back to the water treatment tank 1 along the first pipeline system 5 and the fourth pipeline system 8 where the third control valve 56 is located.

[0044] When it is necessary to drain the cold liquid from the water treatment tank, such as Figure 7 As shown, close the first control valve 71, the second control valve 81 and the third control valve 56, open the fourth control valve 91, the fifth control valve 54 and the sixth control valve 55, connect the fifth pipeline system to the coolant collection container, and manually start the water treatment pump to discharge the coolant in the water treatment tank 1 from the first pipeline system 5 and the fifth pipeline system 9 to the coolant collection container.

[0045] This embodiment is merely a further explanation of the present invention and is not intended to limit the present invention. Those skilled in the art can make non-inventive modifications to this embodiment as needed after reading this specification, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. An off-line draining system for a nuclear emergency diesel generator set, characterized by, include: A water treatment tank is used to store coolant and supply coolant to the expansion tank when the liquid level in the expansion tank is lower than a set value. The water treatment tank is located at the lowest point of the system. A vent is also provided at the top of the water treatment tank. An expansion tank is used to store coolant and supply coolant to the heat exchange system of the equipment for heat exchange to reduce the operating temperature of the equipment. The expansion tank is located at the highest point of the system and has a vent at the top. A water treatment pump is used to extract coolant from the water treatment tank and deliver it to the target location through the pipeline system. When the expansion tank and the equipment are initially filled with coolant, the water treatment pump injects the coolant from the water treatment tank into the heat exchange system and the expansion tank of the equipment from bottom to top. When the equipment is running and needs to be filled with coolant into the expansion tank, the water treatment pump directly injects the coolant from the water treatment tank into the expansion tank. The device is located at a height between the water treatment tank and the expansion tank.

2. The off-line draining and charging system for nuclear emergency diesel generator set according to claim 1, characterized in that, The bottom of the water treatment tank is equipped with a pump suction port; The bottom of the expansion tank is provided with a system water inlet, and the top of the expansion tank is provided with an expansion tank water outlet. A first pipeline system is connected between the pump inlet and the heat exchange system of the equipment, and the water treatment pump is connected to the first pipeline system. A second pipeline system is connected between the heat exchange system and the system water inlet of the equipment. The second pipeline system is used to add coolant to the expansion tank before the equipment is running and to replenish the heat exchange system of the equipment with coolant by gravity during the operation of the equipment. The first pipeline system is also connected to a third pipeline system at the output end of the water treatment pump. A third pipeline interface is provided on the first pipeline system at the output end of the water treatment pump. One end of the third pipeline system is connected to the third pipeline interface, and the other end of the third pipeline system is connected to the expansion tank inlet to replenish coolant into the expansion tank during system operation.

3. The offline charging and draining system for nuclear power emergency diesel generator sets according to claim 2, characterized in that, The upper end of the water treatment tank is provided with a system drain return port. A fourth pipeline system is connected between the system drain return port and the first pipeline system. A fourth pipeline interface is provided on the first pipeline system at the output end of the water treatment pump. The fourth pipeline interface is located at the rear end of the third pipeline interface. One end of the fourth pipeline system is connected to the system drain return port, and the other end of the fourth pipeline system is connected to the fourth pipeline interface. The fourth pipeline system is used to drain and return coolant to the water treatment tank.

4. The off-line draining and charging system for nuclear emergency diesel generator set according to claim 3, characterized in that, The first pipeline system is further provided with a fifth pipeline interface between the third pipeline interface and the fourth pipeline interface. The fifth pipeline interface is connected to a fifth pipeline system for adding coolant to the water treatment tank and discharging coolant. The fifth pipeline system is indirectly connected to the fourth pipeline system through the first pipeline system.

5. The off-line draining and charging system for nuclear emergency diesel generator set according to claim 1, characterized in that, The expansion tank is provided with an expansion tank overflow port at its upper end, and the water treatment tank is provided with an overflow return port at its upper end. A sixth pipeline system is connected between the expansion tank overflow port and the overflow return port. The sixth pipeline system is used to return the overflow coolant in the expansion tank to the water treatment tank.

6. The off-line draining and charging system for nuclear emergency diesel generator set according to claim 4, characterized in that, A fifth control valve, a sixth control valve, and a third control valve are installed on the first pipeline system; the fifth control valve is located between the pump suction port and the input end of the water treatment pump, the sixth control valve is located between the output end of the water treatment pump and the third pipeline interface, and the third control valve is located between the fourth pipeline interface and the heat exchange system of the equipment; a first control valve is installed on the third pipeline system; a second control valve is installed on the fourth pipeline system; and a fourth control valve is installed on the fifth pipeline system.

7. The off-line draining and charging system for nuclear emergency diesel generator set according to claim 6, characterized in that, A check valve is also installed on the first pipeline system between the output end of the water treatment pump and the third pipeline interface to prevent coolant from flowing back into the water treatment pump.

8. The off-line draining and charging system for emergency diesel generator set of nuclear power plant according to claim 1, characterized in that, The design capacity of the water treatment tank is greater than the sum of the expansion tank capacity, the liquid storage capacity of the equipment's heat exchange system, the liquid storage capacity of the pipeline, and the amount of coolant used to replenish the expansion tank during system operation; the design capacity of the expansion tank is greater than the volume change of the coolant in the system as it rises from a low temperature to the highest temperature.

9. The off-line drainage system for nuclear emergency diesel generator set according to any one of claims 1-8, characterized in that, The water treatment tank is also equipped with a first liquid level monitoring device for monitoring the liquid level inside the water treatment tank, and the expansion tank is also equipped with a second liquid level monitoring device for monitoring the liquid level inside the expansion tank.

10. A method of controlling an off-line charging and draining system for a nuclear emergency diesel generator set as defined in claim 9, characterized in that, include: When the water treatment tank is filled with water for the first time, the second control valve, the fourth control valve, the fifth control valve and the sixth control valve are opened, the first control valve and the third control valve are closed, the fifth pipeline system is connected to the fourth pipeline system, and coolant is injected into the water treatment tank through the fifth pipeline system. When the liquid level in the water treatment tank reaches the set high level, the fourth control valve is closed. Before the system is started, the water treatment pump is started. The coolant in the water treatment tank flows along the first pipeline system to the fourth pipeline system and then flows back to the water treatment tank to achieve coolant homogenization. When the expansion tank and equipment heat exchange system are first filled with coolant, the third, fifth, and sixth control valves are opened, and the first, second, and fourth control valves are closed. The water treatment pump is started, and the coolant in the water treatment tank flows along the first pipeline system to the equipment heat exchange system, and then from the equipment heat exchange system to the expansion tank via the second pipeline system. When the liquid level in the expansion tank reaches the set high level, the water treatment pump is turned off and the third control valve is closed. During equipment operation, the first, fifth, and sixth control valves remain normally open, while the second, third, and fourth control valves remain normally closed. When the coolant in the equipment's heat exchange system decreases, the expansion tank automatically replenishes the coolant to the heat exchange system by gravity. When the liquid level in the expansion tank falls below the set low level, the water treatment pump starts, and the coolant is supplied to the expansion tank by the first and third pipeline systems until the liquid level in the expansion tank reaches the set high level. During equipment maintenance, the second, third, fifth, and sixth control valves are opened, while the first and fourth control valves are closed, and the coolant in the expansion tank and the coolant in the equipment heat exchange system are returned to the water treatment tank. When the coolant in the water treatment tank needs to be drained, the fourth, fifth, and sixth control valves open, the first, second, and third control valves close, and the water treatment pump is started to discharge the coolant in the water treatment tank through the first and fifth pipeline systems.

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