Secondary circuit reverse pressure-bearing protection system of steam generator

Abstract

The utility model discloses a reverse pressure-bearing protection system for a secondary circuit of a steam generator, which belongs to the technical field of nuclear power and is characterized in that a secondary pipe side inlet of the steam generator is communicated with an outlet of a three-way valve through an air compressor, an inlet of the three-way valve is divided into two paths, an inlet of the air storage tank is communicated with an outlet of the second electric control valve; the other path is communicated with an outlet of a nitrogen storage tank, an inlet of the nitrogen storage tank is communicated with an outlet of a third electric valve, and an inlet of the second electric control valve and an inlet of the third electric valve are communicated with a secondary pipe side outlet of the steam generator; according to the system, the risk of suffocation gas in the testing process can be reduced, precise control over the pressure and the temperature of the secondary pipe side in the testing process of the steam generator is achieved, and reverse pressure bearing of a heat transfer pipe of the steam generator is effectively avoided.

Description

Technical Field

[0001] The utility model belongs to the technical field of nuclear power, and relates to a reverse pressure bearing protection system and method for the secondary circuit of a steam generator. Background Art

[0002] The steam generator of a high-temperature gas-cooled reactor is a once-through steam generator. To ensure the heat exchange effect, the pressure on the secondary tube side is higher than that on the primary shell side during the operation of the steam generator. At the same time, the heat transfer tubes on the secondary tube side and the outlet tube sheet adopt an expansion joint plus seal welding form. This welding structure requires that the pressure on the secondary tube side of the steam generator be greater than that on the primary shell side during operation. During the primary circuit heating and pressurization test in the reactor core, the primary shell side of the steam generator serves as the test boundary of the primary circuit and needs to cooperate with the primary circuit for relevant tests. During this period, the secondary tube side remains isolated. To avoid the pressure on the secondary tube side of the steam generator being less than that on the primary shell side during the test, that is, to avoid reverse pressure bearing on the heat transfer tubes of the steam generator, the existing test method is to stagewise charge nitrogen into the heat transfer tube side by operators on site to increase the pressure on the secondary tube side. There are at least the following drawbacks: First, it is very difficult to accurately control the pressure and temperature on the secondary tube side by the on-site manual nitrogen charging method, and the parameter fluctuations thereof are extremely likely to affect the stability of the test pressure and temperature on the primary shell side. Especially when the temperature difference between the secondary tube side and the primary shell side is large, there is heat conduction inside and outside the tube, affecting the accuracy of the primary circuit heating and pressurization test results. Second, the medium charged into the heat transfer tube side is nitrogen. Nitrogen is an asphyxiating gas and is not easy to diffuse. Since the nitrogen charging part is at the bottom of the secondary tube side of the steam generator, which is located at the bottommost layer of the nuclear island building, nitrogen leakage will bring a safety hazard of asphyxiation to the personnel in the working area. Third, during the pressure relief process after the test, the original test method did not consider how to avoid reverse pressure bearing on the heat transfer tubes of the steam generator. Summary of the Utility Model

[0003] The purpose of the utility model is to overcome the above-mentioned drawbacks of the prior art, and provides a reverse pressure bearing protection system and method for the secondary circuit of a steam generator. The system and method can reduce the risk of asphyxiating gas during the test, realize the control of the pressure and temperature on the secondary tube side during the steam generator test, and effectively avoid reverse pressure bearing on the heat transfer tubes of the steam generator.

[0004] To achieve the above purpose, the utility model discloses a reverse pressure bearing protection system for the secondary circuit of a steam generator, which includes a steam generator, an electric heater, an air compressor, a three-way valve, an air storage tank, and a nitrogen storage tank;

[0005] The secondary tube side inlet of the steam generator is connected to the outlet of the three-way valve through an electric heater and an air compressor. The inlet of the three-way valve is divided into two paths. Among them, one path is connected to the outlet of the air storage tank, and the inlet of the air storage tank is connected to the secondary tube side outlet of the steam generator; the other path is connected to the outlet of the nitrogen storage tank and the secondary tube side outlet of the steam generator. A second pressure monitor, a second temperature monitor and a nitrogen purity monitor are connected to the secondary tube side outlet of the steam generator.

[0006] The inlet of the air storage tank is connected to the secondary tube side outlet of the steam generator through a second electric control valve;

[0007] The other path is connected to the outlet of the nitrogen storage tank. The inlet of the nitrogen storage tank is connected to the outlet of the third electric valve. The inlets of the second electric control valve and the third electric valve are connected to the secondary tube side outlet of the steam generator.

[0008] The secondary tube side inlet of the steam generator is connected to the outlet of the three-way valve through a second electric valve, an electric heater and an air compressor.

[0009] It also includes a main helium blower, a helium compressor and a helium storage tank;

[0010] The main helium blower is located on the primary shell side of the steam generator. The primary shell side inlet of the steam generator is connected to the outlet of the helium storage tank through a helium compressor; the primary shell side outlet of the steam generator is connected to the inlet of the helium storage tank.

[0011] A first pressure monitor and a first temperature monitor are connected to the pipeline between the primary shell side outlet of the steam generator and the first electric control valve.

[0012] The primary shell side inlet of the steam generator is connected to the outlet of the helium storage tank through a first electric valve and a helium compressor.

[0013] The primary shell side outlet of the steam generator is connected to the inlet of the helium storage tank through a first electric control valve.

[0014] The utility model has the following beneficial effects:

[0015] When the reverse pressure protection system for the secondary circuit of the steam generator described in this utility model is in specific operation, a second pressure monitor, a second temperature monitor, and a nitrogen purity monitor are connected to the outlet of the secondary tube side of the steam generator. By detecting the pressure, temperature, and nitrogen purity at the outlet of the secondary tube side of the steam generator, the air compressor and the electric heater are controlled to automatically track the pressure and temperature of the primary shell side of the steam generator, achieving precise control of the pressure and temperature of the secondary tube side of the steam generator. During the pressure increase process of the primary circuit, it is ensured that the pressure of the secondary tube side of the steam generator is always greater than the pressure of the primary shell side, effectively avoiding reverse pressure on the heat transfer tubes of the steam generator. At the same time, during the temperature increase process of the primary circuit, it is ensured that the temperature of the secondary tube side of the steam generator is always close to the temperature of the primary shell side, thereby improving the accuracy of the test results. At the same time, the pressurizing medium on the secondary tube side uses compressed air to replace nitrogen, greatly reducing the risk of asphyxiating gas during the test process.

[0016] Furthermore, electric control valves are configured on the primary shell side and the secondary tube side of the steam generator to automatically adjust the pressure relief rate through the electric control valves, avoiding the problem of reverse pressure on the heat transfer tubes of the steam generator during the pressure relief process.

[0017] Furthermore, remote automatic control is achieved during the pressure increase and pressure relief processes, effectively reducing the risk of personnel operation. Brief Description of the Drawings

[0018] Figure 1 It is a structural schematic diagram of this utility model.

[0019] Among them, 1 is the steam generator, 2 is the main helium blower, 3 is the helium storage tank, 4 is the helium compressor, 5 is the first electric valve, 6 is the first electric control valve, 7 is the air storage tank, 8 is the nitrogen storage tank, 9 is the three-way valve, 10 is the air compressor, 11 is the electric heater, 12 is the second electric valve, 13 is the second electric control valve, 14 is the third electric valve, 15 is the first pressure monitor, 16 is the first temperature monitor, 17 is the second pressure monitor, 18 is the second temperature monitor, and 19 is the nitrogen purity monitor. Detailed Embodiment

[0020] In order to enable those skilled in the art to better understand the solution of this utility model, the technical solutions in the embodiments of this utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, not all of the embodiments, and are not intended to limit the scope of the disclosure of this utility model. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts disclosed in this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this utility model.

[0021] The structural schematic diagrams according to the disclosed embodiments of the present utility model are shown in the accompanying drawings. These drawings are not drawn to scale, where for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the drawings, their relative sizes, and positional relationships are merely exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0022] Embodiment 1

[0023] Reference Figure 1 , the secondary loop reverse pressure-bearing protection system of the steam generator described in the present utility model includes a steam generator 1, a main helium blower 2, a helium storage tank 3, a helium compressor 4, a first electric valve 5, a first electric regulating valve 6, an air storage tank 7, a nitrogen storage tank 8, a three-way valve 9, an air compressor 10, an electric heater 11, a second electric valve 12, a second electric regulating valve 13, a third electric valve 14, a first pressure monitor 15, a first temperature monitor 16, a second pressure monitor 17, a second temperature monitor 18, and a nitrogen purity monitor 19.

[0024] The main helium blower 2 is located on the primary shell side of the steam generator 1. The inlet of the primary shell side of the steam generator 1 is communicated with the outlet of the first electric valve 5. The inlet of the first electric valve 5 is communicated with the outlet of the helium compressor 4. The inlet of the helium compressor 4 is communicated with the outlet of the helium storage tank 3. The outlet of the primary shell side of the steam generator 1 is communicated with the inlet of the first electric regulating valve 6. The outlet of the first electric regulating valve 6 is communicated with the inlet of the helium storage tank 3. A first pressure monitor 15 and a first temperature monitor 16 are connected to the pipeline between the outlet of the primary shell side of the steam generator 1 and the first electric regulating valve 6 to form a pressurization loop for the primary shell side of the steam generator 1.

[0025] The inlet of the secondary tube side of the steam generator 1 is communicated with the outlet of the second electric valve 12. The inlet of the second electric valve 12 is communicated with the outlet of the electric heater 11. The inlet of the electric heater 11 is communicated with the outlet of the air compressor 10. The inlet of the air compressor 10 is communicated with the outlet of the three-way valve 9. The inlet of the three-way valve 9 is divided into two paths. Among them, one path is communicated with the outlet of the air storage tank 7. The inlet of the air storage tank 7 is communicated with the outlet of the second electric regulating valve 13. The other path is communicated with the outlet of the nitrogen storage tank 8. The inlet of the nitrogen storage tank 8 is communicated with the outlet of the third electric valve 14. The inlets of the second electric regulating valve 13 and the third electric valve 14 are communicated with the outlet of the secondary tube side of the steam generator 1. A second pressure monitor 17, a second temperature monitor 18, and a nitrogen purity monitor 19 are connected to the outlet of the secondary tube side of the steam generator 1 to form a pressurization loop for the secondary tube side of the steam generator 1.

[0026] Example 2

[0027] Taking the demonstration project of a high-temperature gas-cooled reactor nuclear power unit as an example, the primary shell side of the steam generator 1 is helium, the secondary tube side of the steam generator 1 is a steam-water mixture, and the main helium blower 2 conducts a startup test when the pressure on the primary shell side of the steam generator 1 is 4 MPa, and the rotational speed range is 1000 - 4000 rpm; the rated operating conditions on the primary shell side of the steam generator 1 are 7 MPa and 250 °C.

[0028] It includes the following steps:

[0029] (1) Gas replacement process before pressure bearing

[0030] Initial state: The steam generator 1 is in a nitrogen-filled maintenance state, a certain amount of nitrogen is filled in the secondary tube side of the steam generator 1, compressed air is filled in the air storage tank 7, and nitrogen is filled in the nitrogen storage tank 8. The helium compressor 4, the air compressor 10, and the electric heater 11 are shut down, the first electric valve 5, the second electric valve 12, the third electric valve 14, the first electric regulating valve 6, and the second electric regulating valve 13 are closed, and the first air side and the second nitrogen side of the three-way valve 9 are closed.

[0031] Open the third electric valve 14, the nitrogen output from the secondary tube side of the steam generator 1 enters the nitrogen storage tank 8 through the third electric valve 14, open the second electric valve 12, open the first air side of the three-way valve 9, and the air in the air storage tank 7 enters the secondary tube side of the steam generator 1 in sequence through the three-way valve 9, the air compressor 10, the electric heater 11, and the second electric valve 12. Gradually increase the opening degree of the first air side of the three-way valve 9. As the nitrogen in the secondary tube side of the steam generator 1 is continuously discharged into the nitrogen storage tank 8, the air content in the secondary tube side of the steam generator 1 increases continuously. Use the nitrogen purity monitor 19 to monitor the nitrogen purity at the outlet of the secondary tube side of the steam generator 1. When the measured nitrogen purity is lower than 0.2%, the gas replacement process ends, and the third electric valve 14 is closed.

[0032] (2) Performance test process

[0033] Initial state: The secondary tube side of the steam generator 1 has been replaced with air, the helium compressor 4, the air compressor 10, and the electric heater 11 are shut down, the first electric valve 5, the third electric valve 14, the first electric regulating valve 6, and the second electric regulating valve 13 are closed, and the second electric valve 12 and the first air side of the three-way valve 9 are open.

[0034] 1) Pressurization process on the primary and secondary sides of the steam generator 1

[0035] Start the air compressor 10 and keep it running at the minimum frequency. Gradually fill the air in the air storage tank 7 into the secondary tube side of the steam generator 1. Monitor the pressure at the secondary tube side of the steam generator 1 through the second pressure monitor 17. After the pressure at the secondary tube side of the steam generator 1 reaches above 1 MPa, open the first electric valve 5, start the helium compressor 4, and keep it running at the minimum frequency. Then start to gradually fill the helium in the helium storage tank 3 into the primary shell side of the steam generator 1. Monitor the pressure at the primary shell side of the steam generator 1 through the first pressure monitor 15, and keep the pressure at the primary shell side of the steam generator 1 below 1 MPa.

[0036] 2) Startup test of the main helium blower 2

[0037] Gradually increase the frequency of the helium compressor 4. The pressure at the primary shell side of the steam generator 1 gradually rises. Put the air compressor 10 into automatic operation and track the pressure at the primary shell side of the steam generator 1 to ensure that the pressure measured by the second pressure monitor 17 is always greater than the pressure measured by the first pressure monitor 15. When the pressure measured by the first pressure monitor 15 reaches 4 MPa, start the main helium blower 2 and keep it running at the minimum frequency, with the rotational speed maintained at 1000 rpm, and start the startup operation test.

[0038] 3) Test under the rated condition of the primary shell side of the steam generator 1

[0039] Gradually increase the frequency of the helium compressor 4, and continue to pressurize the primary shell side of the steam generator 1 to 7 MPa. During the pressurization process, keep the air compressor 10 in the automatic operation state and track the pressure at the primary shell side of the steam generator 1 to ensure that the pressure measured by the second pressure monitor 17 is always greater than the pressure measured by the first pressure monitor 15.

[0040] Gradually increase the frequency of the main helium blower 2. The temperature of the helium in the primary shell side of the steam generator 1 rises after absorbing the thermal power of the main helium blower 2. Put the electric heater 11 into automatic operation and track the temperature at the primary shell side of the steam generator 1 to ensure that the temperature measured by the first temperature monitor 16 is close to the temperature measured by the second temperature monitor 18. Until the temperature at the primary shell side of the steam generator 1 rises to 250 °C, conduct the performance test under the rated condition of the steam generator 1.

[0041] (3) Maintenance process after the test

[0042] Initial state: The secondary tube side of the steam generator 1 has been replaced with air. The helium compressor 4, air compressor 10, and electric heater 11 are running. The first electric valve 5, second electric valve 12, and the first air side of the three-way valve 9 are open; the third electric valve 14, first electric regulating valve 6, and second electric regulating valve 13 are closed.

[0043] 1) Pressure relief process

[0044] After the performance test is completed, stop the main helium blower 2, stop the electric heater 11, stop the helium compressor 4, close the first electric valve 5, stop the helium compressor 4 and the air compressor 10, close the second electric valve 12, close the first air side of the three-way valve 9, put the first electric control valve 6 into automatic and track the primary shell side pressure of the steam generator 1. The primary shell side pressure of the steam generator 1 gradually decreases. Put the second electric control valve 13 into automatic and track the secondary tube side pressure of the steam generator 1. The secondary tube side pressure of the steam generator 1 decreases following the primary shell side pressure of the steam generator 1, ensuring that the pressure measured by the second pressure monitor 17 is greater than the pressure measured by the first pressure monitor 15. When the primary shell side pressure of the steam generator 1 drops to atmospheric pressure, the pressure relief is completed, and close the first electric control valve 6.

[0045] 2) Nitrogen replacement of air process

[0046] Open the second electric valve 12 and the second electric control valve 13, open the second nitrogen side of the three-way valve 9. The nitrogen in the nitrogen storage tank 8 enters the secondary tube side of the steam generator 1 successively through the three-way valve 9, the air compressor 10, the electric heater 11 and the second electric valve 12. Gradually increase the opening of the second nitrogen side of the three-way valve 9. As the nitrogen in the secondary tube side of the steam generator 1 increases, the remaining air in the secondary tube side of the steam generator 1 is continuously discharged to the air storage tank 7 through the second electric control valve 13. The nitrogen content in the secondary tube side of the steam generator 1 increases. Use the nitrogen purity monitor 19 to monitor the nitrogen purity at the outlet of the secondary tube side of the steam generator 1. When the nitrogen purity measured by the nitrogen purity monitor 19 is higher than 98%, close the second electric valve 12, the second electric control valve 13 and the second nitrogen side of the three-way valve 9, and the gas replacement process ends.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: still can modify the specific implementation manners of the present invention or make equivalent replacements. Any modification or equivalent replacement without departing from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A steam generator secondary circuit reverse pressure protection system, characterized in that: It comprises a steam generator (1), an electric heater (11), an air compressor (10), a three-way valve (9), an air storage tank (7) and a nitrogen storage tank (8); The secondary pipe side inlet of the steam generator (1) is connected to the outlet of the three-way valve (9) via the electric heater (11) and the air compressor (10). The inlet of the three-way valve (9) is divided into two paths, one of which is connected to the outlet of the air storage tank (7), and the inlet of the air storage tank (7) is connected to the secondary pipe side outlet of the steam generator (1); the other path is connected to the outlet of the nitrogen storage tank (8) and the secondary pipe side outlet of the steam generator (1). The secondary pipe side outlet of the steam generator (1) is connected to a second pressure monitor (17), a second temperature monitor (18) and a nitrogen purity monitor (19).

2. The steam generator secondary circuit reverse pressure protection system according to claim 1, characterized in that: The inlet of the air storage tank (7) is connected to the secondary pipe side outlet of the steam generator (1) via the second electric regulating valve (13); The other path is connected to the outlet of the nitrogen storage tank (8), the inlet of the nitrogen storage tank (8) is connected to the outlet of the third electric valve (14), and the inlet of the second electric regulating valve (13) and the inlet of the third electric valve (14) are connected to the outlet of the secondary pipe side of the steam generator (1).

3. The steam generator secondary circuit reverse pressure protection system according to claim 2, characterized in that: The secondary pipe side inlet of the steam generator (1) is connected to the outlet of the three-way valve (9) via the second electric valve (12), the electric heater (11) and the air compressor (10).

4. The steam generator secondary circuit reverse pressure protection system according to claim 1, characterized in that: It also includes a main helium blower (2), a helium compressor (4) and a helium storage tank (3); The main helium blower (2) is located on the primary shell side of the steam generator (1); the primary shell side inlet of the steam generator (1) is connected to the outlet of the helium storage tank (3) via the helium compressor (4); the primary shell side outlet of the steam generator (1) is connected to the inlet of the helium storage tank (3).

5. The steam generator secondary circuit reverse pressure protection system according to claim 4, characterized in that: A first temperature monitor (16) is connected to the pipeline between the primary shell side outlet of the steam generator (1) and the first electric regulating valve (6).

6. The steam generator secondary circuit reverse pressure protection system according to claim 4, characterized in that: A first pressure monitor (15) is connected to the pipeline between the primary shell side outlet of the steam generator (1) and the first electric regulating valve (6).

7. The steam generator secondary circuit reverse pressure protection system according to claim 4, characterized in that: The primary shell side inlet of the steam generator (1) is connected to the outlet of the helium storage tank (3) via the first electric valve (5) and the helium compressor (4).

8. The steam generator secondary circuit reverse pressure protection system according to claim 4, characterized in that: The primary shell side outlet of the steam generator (1) is connected to the inlet of the helium storage tank (3) via a first electric regulating valve (6).

9. The steam generator secondary circuit reverse pressure protection system according to claim 4, characterized in that: A first temperature monitor (16) and a first pressure monitor (15) are connected to a pipeline between the primary shell side outlet of the steam generator (1) and the first electric regulating valve (6).

10. The steam generator secondary circuit reverse pressure protection system according to claim 4, characterized in that: The primary shell side inlet of the steam generator (1) is connected to the outlet of the helium storage tank (3) via a first electric valve (5) and a helium compressor (4), and the primary shell side outlet of the steam generator (1) is connected to the inlet of the helium storage tank (3) via a first electric regulating valve (6).

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