Pressure relief method for active type parking sealing nitrogen tank of nuclear power main pump

Abstract

The invention discloses a nuclear power main pump active type parking sealing nitrogen tank pressure relief method which comprises the steps that S1, a containment isolation valve on a nitrogen supply pipeline of an SGN system is opened, and a temporary pressure relief device is installed on a quick connector on the downstream of an exhaust pipeline of the SGN system; s2, an exhaust valve on the exhaust pipeline is opened, the exhaust pipeline and a containment isolation valve are communicated, and the main pump active type parking sealing nitrogen tank conducts pressure relief through the containment isolation valve and the exhaust valve; s3, when the pressure of the temporary pressure relief device is displayed as 0 MPa. G, the exhaust valve is closed; and S4, closing the containment isolation valve, and observing the pressure change of the main pump active type parking sealing nitrogen tank. The pressure of the active parking sealing nitrogen tank is effectively reduced, important equipment related to nuclear safety is protected, and the pressure of the whole nitrogen supply pipeline can be adjusted to meet the system requirement; and the abnormal working condition of the active parking sealing nitrogen tank can be quickly responded.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power plant operation control, and in particular to a method for depressurizing a sealed nitrogen tank for an active shutdown of a nuclear power main pump. Background Art

[0002] In a nuclear power plant, the main pump plays a crucial role. It circulates the coolant in the primary circuit, transferring heat generated by the reactor to the steam generator, generating steam to drive the turbine. It also maintains sufficient coolant pressure, ensuring the primary circuit operates at high pressure, preventing coolant boiling and ensuring reactor safety. The active shutdown seal system is a crucial component of the main pump shaft seal system. If the shutdown seal nitrogen tank pressure exceeds 1.4 MPa.g, operating the shutdown seal may damage the seal components. Therefore, operating the main pump shutdown seal is prohibited to prevent equipment damage. If the shutdown seal line pressure continues to rise to 1.8 MPa.g, the safety valve on the nitrogen supply main pipe may fail, potentially causing overpressure damage to the nitrogen tank solenoid valve. This could lead to inadvertent activation of the shutdown seal and potentially damage the main pump. Due to the inherent leakage rate of the self-operated pressure reducing valve, combined with the upstream nitrogen pressure of 4.8 MPa.g and the downstream nitrogen pressure of 1.0 MPa.g, the nitrogen tank pressure may continue to rise slowly. Even if the containment isolation valves inside and outside the reactor building are closed at the same time, the pressure rise in the nitrogen tank cannot be effectively suppressed. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for depressurizing a sealed nitrogen tank during active shutdown of a nuclear power main pump.

[0004] The technical solution adopted by the present invention to solve the technical problem is: to provide a method for depressurizing a sealed nitrogen tank during active shutdown of a nuclear power main pump, comprising the following steps:

[0005] S1. Open the containment isolation valve on the nitrogen supply pipeline of the SGN system and install a temporary pressure relief device on the quick connector downstream of the exhaust pipeline of the SGN system;

[0006] The nitrogen supply pipeline is connected to the main pump active stop sealed nitrogen tank through a self-operated pressure reducing valve; when the containment isolation valve is open, the main pump active stop sealed nitrogen tank located downstream of the self-operated pressure reducing valve is connected to the containment isolation valve;

[0007] S2. Open the exhaust valve on the exhaust pipeline to connect the exhaust pipeline and the containment isolation valve. The main pump active shutdown sealed nitrogen tank is depressurized through the containment isolation valve, the exhaust valve and the temporary pressure relief device.

[0008] S3. When the pressure of the temporary pressure relief device is displayed as 0 MPa.g, close the exhaust valve;

[0009] S4. Close the containment isolation valve and observe the pressure change of the main pump's active shutdown sealing nitrogen tank.

[0010] In some embodiments, in step S1, when the nitrogen supply isolation valve of the injection box, the nitrogen supply isolation valve on the nitrogen supply pipeline of the SGN system, and the main pump shutdown sealing solenoid valve are in the closed state, the containment isolation valve is opened.

[0011] In some embodiments, during steps S1 to S4, the nitrogen pressure in the safety injection box should satisfy the following: 4.4 MPa.g ≤ nitrogen pressure in the safety injection box ≤ 4.9 MPa.g.

[0012] In some embodiments, when the nitrogen pressure in the safety injection box is lower than 4.4 MPa.g, the safety injection box is pressurized;

[0013] The pressure replenishment for the safety injection tank includes: opening the containment isolation valve and the nitrogen supply isolation valve on the nitrogen supply pipeline, and nitrogen enters the safety injection tank through the nitrogen supply isolation valve, the containment isolation valve and the nitrogen supply isolation valve, and the pressure replenishment is ended when the nitrogen pressure in the safety injection tank is greater than or equal to 4.4 MPa.g and less than or equal to 4.9 MPa.g; re-executing steps S1 to S4 until the pressure of the pipeline upstream of the self-operated pressure reducing valve drops to 0 MPa.g.

[0014] In some embodiments, the method for depressurizing a sealed nitrogen tank for an active shutdown of a nuclear power main pump further comprises the following steps:

[0015] S5. When the pressure of the main pump active parking sealing nitrogen tank drops to 1.0 MPa.g, the upstream pipeline of the self-operated pressure reducing valve is pressurized to the target pressure, and the target pressure is 1.0 MPa.g to 1.3 MPa.g.

[0016] In some embodiments, charging the upstream pipeline of the self-operated pressure reducing valve to a target pressure comprises the following steps:

[0017] S5.1. Open the exhaust valve, and the temporary pressure relief device downstream of the exhaust valve is in the closed state;

[0018] S5.2. Open the nitrogen supply isolation valve on the nitrogen supply line of the SGN system;

[0019] S5.3. When the pressure of the temporary pressure relief device is displayed as 1.0 MPa.g to 1.3 MPa.g, close the nitrogen supply isolation valve;

[0020] S5.4. After the pressure of the downstream pipeline of the self-operated pressure reducing valve is stabilized, the pressure of the downstream pipeline is adjusted to reach the target pressure by opening and closing the temporary pressure relief device, and then the exhaust valve is closed.

[0021] In some embodiments, the temporary pressure relief device includes a valve body with a pressure gauge and a male connector for detachably plugging into the valve body; the valve body has a first end and a second end opposite to each other, the first end being configured to be mated with the quick connector; when the male connector is plugged into the second end, the male connector communicates with an internal passage of the valve body for pressure relief; after the male connector is detached from the valve body, the second end of the valve body is closed;

[0022] In step S5.1, the temporary pressure relief device is not provided with the male connector, and the temporary pressure relief device is in a closed state.

[0023] In some embodiments, the method for relieving pressure of a sealed nitrogen tank for active shutdown of a nuclear power main pump is used for relieving pressure when the pressure of a sealed nitrogen tank for active shutdown of a nuclear power main pump reaches 1.4 MPa.g or above.

[0024] In some embodiments, the temporary pressure relief device includes a valve body with a pressure gauge and a male head for detachably plugging into the valve body; the valve body has a first end and a second end relative to each other, and the first end is used to cooperate with the quick connector; when the male head is plugged into the second end, the male head is connected to the internal channel of the valve body for pressure relief; after the male head is detached from the valve body, the second end of the valve body is closed.

[0025] In some embodiments, in step S1 , the temporary pressure relief device is provided with the male connector, and at this time the temporary pressure relief device is in a pressure relief state.

[0026] The beneficial effects of the present invention are as follows: the pressure of the active shutdown sealed nitrogen tank is effectively reduced, important nuclear safety-related equipment is protected, and the pressure of the entire nitrogen supply pipeline can be adjusted to meet system requirements; the method can quickly respond to abnormal operating conditions of the active shutdown sealed nitrogen tank, and at the same time, the response can be completed outside the reactor building, avoiding staff from entering the reactor building to perform meter removal and pressure relief, absorbing unnecessary radioactive doses, and reducing the collective dose of the power plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0028] Figure 1 This is a schematic diagram of the connection of a nuclear power system used in a method for pressure relief of a sealed nitrogen tank during active shutdown of a nuclear power main pump according to an embodiment of the present invention;

[0029] Figure 2It is a structural schematic diagram of a temporary pressure relief device in one embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0031] The present invention provides a method for relieving pressure in a sealed nitrogen tank during active shutdown of a nuclear power main pump. The nuclear power system involved includes a RIS system (safety injection system), an SGN system (nitrogen distribution system), and an RCP system (reactor coolant system). The SGN system (nitrogen distribution system) is used to supply nitrogen to at least the RIS system (safety injection system) and the RCP system (reactor coolant system).

[0032] like Figure 1 As shown, the main pump active shutdown sealed nitrogen tank 100 is subordinate to the RCP system. The SGN system is connected to the RIS system and the RCP system respectively through the nitrogen supply pipeline 10. The nitrogen supply pipeline 10 includes a nitrogen supply isolation valve 11, a containment isolation valve 12 and a self-operated pressure reducing valve 13; the nitrogen supply isolation valve 11 is outside the containment, Figure 1 There are two nitrogen supply isolation valves 11 and two containment isolation valves 12. The nitrogen supply pipeline 10 is also connected to an exhaust pipeline 14, which is equipped with an exhaust valve 15. A quick connector 16 is provided downstream of the exhaust valve 15 to connect various required pipelines or tools. The downstream of the self-operated pressure reducing valve 13 is connected to the main pump active shutdown sealed nitrogen tank 100 through a check valve 20 and a pipeline. The main pump active shutdown sealed nitrogen tank 100, the check valve 20 and the pipeline also form the downstream pipeline of the self-operated pressure reducing valve 13. The nitrogen supply pipeline 10 and the containment isolation valve 12 upstream of the self-operated pressure reducing valve 13 form the upstream pipeline of the self-operated pressure reducing valve 13.

[0033] The main pump active stop sealing nitrogen tank 100 is connected to the main pump shaft seal through the main pump stop sealing solenoid valve 21. Figure 1 In the illustrated embodiment, the RCP system has three main pump active parking sealing nitrogen tanks 100, which are respectively connected to the No. 1 main pump shaft seal, the No. 2 main pump shaft seal and the No. 3 main pump shaft seal through their own main pump parking sealing solenoid valves 21.

[0034] The RIS system (safety injection system) includes a safety injection tank 200, an injection pipeline 30 connected between the safety injection tank 200 and the nitrogen supply pipeline 10, a check valve 31 and a nitrogen supply isolation valve 32 provided on the injection pipeline 30; the location where the injection pipeline 30 is connected to the nitrogen supply pipeline 10 is between the self-operated pressure reducing valve 13 and the containment isolation valve 12. Figure 1In the illustrated embodiment, the RIS system includes three safety injection tanks 200 , which are respectively connected to the upstream of the self-operated pressure reducing valve 13 via respective nitrogen supply isolation valves 32 and check valves 31 .

[0035] The self-operated pressure-reducing valve 13 is used to reduce the medium-pressure nitrogen pressure of 4.8 MPa.g to 1.0 MPa.g for use in the downstream main pump's active shutdown sealed nitrogen tank 100. The self-operated pressure-reducing valve 13 relies on the set spring force to determine the outlet pressure, ensuring stable downstream pressure. When the upstream pipeline of the self-operated pressure-reducing valve 13 is reversely relieved, the downstream pressure gradually leaks upstream due to the self-operated pressure-reducing valve 13's certain leakage rate. When the downstream pressure drops below the set value, the self-operated pressure-reducing valve 13 opens under the action of the spring force to replenish pressure, effectively releasing pressure, thus completing the pressure relief operation.

[0036] The check valve 20 at the front end of the main pump active parking sealed nitrogen tank 100 is a lift check valve with a hard sealing structure and a certain leakage rate, so it can reversely relieve pressure.

[0037] refer to Figure 1 A method for relieving pressure in a sealed nitrogen tank for an active shutdown of a nuclear power main pump according to an embodiment of the present invention is used to relieve pressure when the pressure of the sealed nitrogen tank 100 for an active shutdown of a nuclear power main pump reaches 1.4 MPa.g or above. The pressure relief method may include the following steps:

[0038] S1. When the nitrogen supply isolation valve 32 of the injection tank 200, the nitrogen supply isolation valve 11 on the nitrogen supply pipeline 10 of the SGN system, and the main pump shutdown sealing solenoid valve 21 are in the closed state, open the containment isolation valve 12 on the nitrogen supply pipeline 10 of the SGN system; install a temporary pressure relief device 40 on the quick connector 16 downstream of the exhaust pipeline 14 of the SGN system.

[0039] The nitrogen supply pipeline 10 is connected to the main pump active parking sealed nitrogen tank 100 through a self-operated pressure reducing valve 13.

[0040] After executing step S1 , when the containment isolation valve 12 is in the open state, the main pump active shutdown sealing nitrogen tank 100 located downstream of the self-operated pressure reducing valve 13 is communicated with the containment isolation valve 12 .

[0041] Among them, Figure 2As shown, the temporary pressure relief device 40 includes a valve body 42 with a pressure gauge 41 and a male connector 43 for removably connecting to the valve body 42. The valve body 42 has a first end 421 and a second end 422, with the first end 421 being adapted to mate with the quick connector 16. When the male connector 43 is connected to the second end 422, the male connector 43 communicates with the internal passageway of the valve body 42 for pressure relief. When the male connector 43 is removed from the valve body 42, the second end 422 of the valve body 42 is closed. In step S1, the temporary pressure relief device 40 is equipped with the male connector 43 and is in a pressure relief state.

[0042] S2. Open the exhaust valve 15 on the exhaust pipeline 14 to connect the exhaust pipeline 14 and the containment isolation valve 12. The main pump active shutdown sealed nitrogen tank 100 is depressurized through the containment isolation valve 12 and the exhaust valve 15. That is, the nitrogen in the main pump active shutdown sealed nitrogen tank 100 is discharged through the check valve 20, the self-operated pressure reducing valve 13, the containment isolation valve 12, the exhaust valve 15 and the temporary pressure relief device 40 in sequence.

[0043] Since the check valve 20 is a lift check valve with a hard seal structure, it has a certain leakage rate and can release pressure in the reverse direction.

[0044] Control the valve opening of the exhaust valve 15 to release pressure at an appropriate opening. Excessive valve opening will cause large vibration in the pipeline and a sharp, piercing sound. A reasonable opening avoids high vibration and rupture of the pipeline, while ensuring the safety of on-site workers.

[0045] During the pressure relief process, the pressure of the three main pumps' active stop sealing nitrogen tank 100 must be closely monitored, and the pressure relief must be stopped in time if any abnormality is detected.

[0046] S3. When the pressure of the temporary pressure relief device 40 is displayed as 0 MPa.g, close the exhaust valve 15.

[0047] S4. Close the containment isolation valve 12 and observe the pressure change of the main pump active shutdown sealing nitrogen tank 100.

[0048] During steps S1 to S4, the nitrogen pressure in the safety injection tank 200 should satisfy the following: 4.4 MPa.g ≤ nitrogen pressure in the safety injection tank 200 ≤ 4.9 MPa.g. When the nitrogen pressure in the safety injection tank 200 is lower than 4.4 MPa.g, the safety injection tank 200 is pressurized.

[0049] Pressure replenishment for injection tank 200 includes opening containment isolation valve 12 and nitrogen supply isolation valve 11 on nitrogen supply pipeline 10. Nitrogen enters injection tank 200 through nitrogen supply isolation valve 11, containment isolation valve 12, and nitrogen supply isolation valve 32. Pressure replenishment is completed when the nitrogen pressure within injection tank 200 is greater than or equal to 4.4 MPa.g and less than or equal to 4.9 MPa.g. Steps S1 to S4 are repeated until the pressure in the pipeline upstream of self-operated pressure reducing valve 13 drops to 0 MPa.g.

[0050] In some embodiments, the method for depressurizing a sealed nitrogen tank for active shutdown of a nuclear power main pump further includes the following steps:

[0051] S5. When the pressure of the sealed nitrogen tank 100 drops to 1.0 MPa.g after the main pump is automatically stopped, the upstream pipeline of the self-operated pressure reducing valve 13 is pressurized to the target pressure, which is 1.0 MPa.g to 1.3 MPa.g.

[0052] In step S5, the pressure change of the nitrogen tank 100 sealed by the active parking of the main pump is continuously observed until the pressure drops to 1.0 MPa.g. This observation period generally needs to last for several days.

[0053] Furthermore, charging the upstream pipeline of the self-operated pressure reducing valve 13 to the target pressure includes the following steps:

[0054] S5.1. Open the exhaust valve 15. The temporary pressure relief device 40 downstream of the exhaust valve 15 is in the closed state.

[0055] In step S5.1, the temporary pressure relief device 40 is not provided with the male connector 43, and the temporary pressure relief device 40 is in a closed state (cannot relieve pressure).

[0056] S5.2. Open the nitrogen supply isolation valve 11 on the nitrogen supply pipeline 10 of the SGN system.

[0057] The nitrogen supply isolation valve 11 is pressurized with a relatively small opening. Excessive valve opening will cause large vibration of the pipeline and sharp and harsh sound.

[0058] Nitrogen enters the main pump active shutdown sealed nitrogen tank 100 through the nitrogen supply isolation valve 11, the containment isolation valve 12, the nitrogen supply pipeline 10 and the self-operated pressure reducing valve 13. At the same time, nitrogen also enters the exhaust pipeline 14 and reaches the temporary pressure relief device 40 through the exhaust valve 15.

[0059] S5.3. When the pressure of the temporary pressure relief device 40 is displayed as 1.0 MPa.g to 1.3 MPa.g, close the nitrogen supply isolation valve 11.

[0060] S5.4. Continue to observe until the pressure of the downstream pipeline of the self-operated pressure reducing valve 13 (including the main pump active shutdown sealing nitrogen tank 100) stabilizes, adjust the downstream pipeline pressure to the target pressure by opening and closing the temporary pressure relief device 40, and then close the exhaust valve 15.

[0061] It takes 30 minutes or more for the pressure in the downstream pipeline of the self-operated pressure reducing valve 13 to stabilize.

[0062] The opening and closing adjustment of the temporary pressure relief device 40 is performed by plugging and unplugging the male connector 43 ; when the pressure in the downstream pipeline is higher than the target pressure, the male connector 43 is inserted to relieve the pressure.

[0063] After the above is completed, the disassembly and restoration work can be carried out, including: removing the temporary pressure relief device 40 on the quick connector 16, closing the containment isolation valve 12, and opening the nitrogen supply isolation valve 11.

[0064] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for depressurizing a sealed nitrogen tank during active shutdown of a nuclear power main pump, characterized in that: The following steps are involved: S1. Open the containment isolation valve on the nitrogen supply pipeline of the SGN system and install a temporary pressure relief device on the quick connector downstream of the exhaust pipeline of the SGN system; Wherein, the nitrogen supply pipeline is connected to the main pump active stop sealed nitrogen tank through a self-operated pressure reducing valve; when the containment isolation valve is open, the main pump active stop sealed nitrogen tank located downstream of the self-operated pressure reducing valve is connected to the containment isolation valve; S2, opening the exhaust valve on the exhaust pipeline, connecting the exhaust pipeline and the containment isolation valve, and the main pump active parking sealed nitrogen tank is depressurized through the containment isolation valve, the exhaust valve and the temporary pressure relief device; S3. When the pressure of the temporary pressure relief device is displayed as 0 MPa.g, close the exhaust valve; S4. Close the containment isolation valve and observe the pressure change of the main pump active parking sealing nitrogen tank.

2. The method for depressurizing a sealed nitrogen tank for an active shutdown of a nuclear power main pump according to claim 1 is characterized in that: In step S1, when the nitrogen supply isolation valve of the injection box, the nitrogen supply isolation valve on the nitrogen supply pipeline of the SGN system and the main pump stop sealing solenoid valve are in the closed state, the containment isolation valve is opened.

3. The method for depressurizing a sealed nitrogen tank for an active shutdown of a nuclear power main pump according to claim 1 is characterized in that: During steps S1 to S4, the nitrogen pressure in the safety injection box should satisfy the following condition: 4.4MPa.g≤nitrogen pressure in the safety injection box≤4.9MPa.g.

4. The method for depressurizing a sealed nitrogen tank for an active shutdown of a nuclear power main pump according to claim 3 is characterized in that: When the nitrogen pressure in the safety injection box is lower than 4.4 MPa.g, the safety injection box is pressurized; The pressure replenishment for the safety injection box includes: opening the containment isolation valve and the nitrogen supply isolation valve on the nitrogen supply pipeline, and nitrogen enters the safety injection box through the nitrogen supply isolation valve, the containment isolation valve and the nitrogen supply isolation valve, and the pressure replenishment is terminated when the nitrogen pressure in the safety injection box is greater than or equal to 4.4MPa.g and less than or equal to 4.9MPa.g; re-executing steps S1 to S4 until the pressure of the upstream pipeline of the self-operated pressure reducing valve drops to 0MPa.g.

5. The method for depressurizing a sealed nitrogen tank for an active shutdown of a nuclear power main pump according to any one of claims 1 to 4, characterized in that: The following steps are also included: S5. When the pressure of the main pump active parking sealed nitrogen tank drops to 1.0 MPa.g, the upstream pipeline of the self-operated pressure reducing valve is pressurized to a target pressure, and the target pressure is 1.0 MPa.g to 1.3 MPa.g.

6. The method for depressurizing a sealed nitrogen tank for an active shutdown of a nuclear power main pump according to claim 5 is characterized in that: The process of pressurizing the upstream pipeline of the self-operated pressure reducing valve to a target pressure comprises the following steps: S5.

1. Open the exhaust valve, and the temporary pressure relief device downstream of the exhaust valve is in a closed state; S5.

2. Open the nitrogen supply isolation valve on the nitrogen supply pipeline of the SGN system; S5.

3. When the pressure of the temporary pressure relief device is displayed as 1.0 MPa.g to 1.3 MPa.g, close the nitrogen supply isolation valve; S5.

4. After the pressure of the downstream pipeline of the self-operated pressure reducing valve is stabilized, the pressure of the downstream pipeline is adjusted to reach the target pressure by opening and closing the temporary pressure relief device, and then the exhaust valve is closed.

7. The method for depressurizing a sealed nitrogen tank for an active shutdown of a nuclear power main pump according to claim 6 is characterized in that: The temporary pressure relief device comprises a valve body with a pressure gauge and a male head for detachably plugging into the valve body; the valve body has a first end and a second end opposite to each other, the first end being used for mating and connecting with the quick connector; when the male head is plugged into the second end, the male head is connected to the internal passage of the valve body for pressure relief; after the male head is detached from the valve body, the second end of the valve body is closed; In step S5.1, the temporary pressure relief device is not provided with the male connector, and the temporary pressure relief device is in a closed state.

8. The method for depressurizing a sealed nitrogen tank during active shutdown of a nuclear power main pump according to any one of claims 1 to 4, characterized in that: The method for relieving pressure of a sealed nitrogen tank for active shutdown of a nuclear power main pump is used for relieving pressure when the pressure of a sealed nitrogen tank for active shutdown of a nuclear power main pump reaches 1.4 MPa.g or above.

9. The method for depressurizing a sealed nitrogen tank during active shutdown of a nuclear power main pump according to any one of claims 1 to 4, characterized in that: The temporary pressure relief device comprises a valve body with a pressure gauge and a male connector for detachably plugging into the valve body; the valve body has a first end and a second end opposite to each other, and the first end is used for mating with the quick connector; When the male connector is plugged into the second end, the male connector is connected to the internal passage of the valve body for pressure relief; after the male connector is detached from the valve body, the second end of the valve body is closed.

10. The method for depressurizing a sealed nitrogen tank during active shutdown of a nuclear power main pump according to claim 9, characterized in that: In step S1, the temporary pressure relief device is provided with the male connector, and at this time, the temporary pressure relief device is in a pressure relief state.

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