Nuclear Power Plant Pipe Flange Normal Operation and Accident Condition Simulation Test System and Method

Abstract

A simulation test system and method for normal operation and accident conditions of a nuclear power plant pipe flange is disclosed. The system includes a water supply system, a preheating system, a test section system, a temperature control system, and a condensation system. The water supply system includes a makeup water tank, a filter, a makeup water pump, a main water tank, a high-pressure plunger pump, a high-pressure regulating valve, a cooler, and a mass flow meter. The preheating system includes a preheater. The test section system includes a pipe flange test section. The temperature control system includes a main flow branch, a rapid temperature switching branch, and a cooling water injection branch. The condensation system consists of a condenser, a cooling tower, a condensate tank, a cooling pump, a filter, a safety valve, and a relief valve. The test system of this invention can simulate the transient temperature and pressure shocks experienced inside the pipe flange structure under normal operation and accident conditions of a nuclear power plant.

Description

Technical Field

[0001] This invention belongs to the field of high temperature and high pressure testing technology for pipe flanges, specifically relating to a simulation test system and method for normal operation and accident conditions of pipe flanges in nuclear power plants. Background Technology

[0002] In the research and development and application of nuclear-grade equipment, it is necessary to test the safety of the equipment under long-term normal operating conditions and sudden accident conditions. Nuclear power plant accident conditions are accompanied by rapid increases and decreases in temperature and pressure. The pipe flange structure of a nuclear power plant is a major safety barrier. Studying the impact of transient temperature and pressure changes on the pipe flange structure under normal operating and accident conditions is of great significance to the safety and economy of nuclear power plants.

[0003] Currently, numerous experiments and finite element analyses have been conducted by scholars both domestically and internationally regarding pipe flange structures. However, the vast majority of these experiments focus on measuring media such as high-pressure inert gases or high-pressure room-temperature water, with limited research on transient operating conditions of pipe flanges under high temperature and pressure. Therefore, conducting experimental research on pipe flange structures under normal operation and accident conditions in nuclear power plants can help analyze the safety of pipe flange structures when subjected to high-temperature and high-pressure shocks during nuclear power plant operation. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a simulation test system and method for the normal operation and accident conditions of nuclear power plant pipe flanges. This system can simulate the impact of sudden and drastic temperature and pressure changes on pipe flanges under normal operation and accident conditions of a nuclear reactor, providing guidance for the design and operational safety of nuclear reactors.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A simulation test system for normal operation and accident conditions of nuclear power plant pipe flanges includes a water supply system, a preheating system, a test section system, a temperature control system, and a condensation system;

[0007] The water supply system includes a makeup water tank 1, a first filter 201, a makeup water pump 2, a main water tank 3, a second filter 202, a high-pressure plunger pump 4, a second high-pressure regulating valve 302, a third high-pressure regulating valve 303, a mass flow meter 5, and a cooler 6. The downstream pipe of the makeup water tank 1 is connected to the first filter 201 and the makeup water pump 2, receiving water from the outlet of the first filter 201 upstream and entering the downstream main water tank 3. The downstream pipe of the main water tank 3 is connected to the second filter 202. The high-pressure plunger pump 4 receives water from the outlet of the second filter 202 upstream, pressurizes it, and then flows out in two branches. One branch connects to the third high-pressure regulating valve 303 and flows to the cooler 6. The water from the outlet of the cooler 6 enters the main water tank 3. The other branch connects to the second high-pressure regulating valve 302 and flows to the mass flow meter 5 to detect the flow rate. This continuously supplies the deionized water required for the test to the entire test section system. The pressure value of the water in the test section system is adjusted by adjusting the operating frequency of the high-pressure plunger pump 4 to simulate the pressure adjustment requirements under normal operation and accident conditions of a nuclear power plant.

[0008] The preheating system includes a preheater 7. Water from the outlet of the mass flow meter 5 in the water supply system flows out in two branches. One branch flows to the cold water injection branch of the temperature control system, and the other branch flows to the preheater 7 for heating. The preheater 7 is heated by a two-point heating method. Copper electrodes are provided at both ends. It is directly energized by low voltage and high current. The voltage is continuously adjusted by an autotransformer. The temperature of the water at the inlet of the test section system is adjusted by changing the electric heating power value to simulate the temperature adjustment requirements under normal operation and accident conditions of a nuclear power plant.

[0009] The test section system includes a pipe flange test section 14, which consists of a flange with connecting pipes. In order to measure the temperature and pressure at the center of the flange, temperature measuring points and pressure measuring points are set at the inlet and outlet of the flange, respectively. The average value of the two values ​​at the inlet and outlet is taken to obtain the temperature and pressure values ​​at the center of the flange.

[0010] The temperature control system includes a main flow branch, a rapid temperature switching branch, and a cooling water injection branch, simulating the slow and rapid temperature rise and fall processes under normal operation and accident conditions of a nuclear power plant. The main flow branch includes the pipeline connecting the outlet of preheater 7 to the flange test section 14 and the pipeline connecting the flange test section 14 to the condensing system. Water from the outlet of preheater 7 in the preheating system enters the first high-pressure shut-off valve 501, and water from the outlet of the first high-pressure shut-off valve 501 enters the flange test section 14 and then flows into the condensing system through the third high-pressure shut-off valve 503. The rapid temperature switching branch is the pipeline connecting the outlet of preheater 7 to the condensing system. Water from the outlet of preheater 7 in the preheating system enters the second high-pressure shut-off valve 502 and then flows into the condensing system. The cooling water injection branch is the pipeline connecting the outlet of mass flow meter 5 to the flange test section 14. Water from the outlet of mass flow meter 5 in the water supply system enters the first high-pressure regulating valve 301 and then flows into the flange test section 14.

[0011] The condensation system includes a condenser 8, a cooling tower 11, a condensate tank 12, a cooling pump 13, a third filter 203, a fourth filter 204, and a fourth high-pressure regulating valve 304. Water from the second high-pressure shut-off valve 502 and the third high-pressure shut-off valve 503 enters the primary side of the condenser 8 through the primary side inlet. The secondary side outlet of the condenser 8 is connected to the cooling tower 11. The water cooled by the cooling tower 11 is stored in the condensate tank 12. The water stored in the condensate tank 12 flows into the secondary side inlet of the condenser 8 through the fourth filter 204 under the action of the cooling pump 13. Water is used as a circulating coolant on the secondary side of the condenser 8 to discharge the heat of the high-temperature water at the outlet of the test section system to the secondary side of the condenser, thereby cooling the water entering the primary side of the condenser from the outlet of the test section system. The water at the primary side outlet of the condenser 8 enters the main water tank 3 of the water supply system through the third filter 203 and the fourth high-pressure regulating valve 304.

[0012] A relief valve 9 and a safety valve 10 are connected between the primary outlet of the condenser 8 and the third filter 203 to ensure the safety of the test section system.

[0013] The first high-pressure regulating valve 301, the second high-pressure regulating valve 302, the third high-pressure regulating valve 303, the fourth high-pressure regulating valve 304, the first high-pressure shut-off valve 501, the second high-pressure shut-off valve 502, and the third high-pressure shut-off valve 503 are adjusted in opening and closing according to temperature regulation needs throughout the entire cycle of normal operation and accident condition simulation test of nuclear power plant pipe flanges. Since the temperature changes relatively rapidly in actual nuclear power plant accident conditions, it is necessary to use electric valves with high safety and efficiency.

[0014] The test method for the nuclear power plant pipe flange normal operation and accident condition simulation test system is as follows:

[0015] Deionized water from the water purification system is stored in makeup water tank 1. Water in makeup water tank 1 is pumped into main water tank 3 via first filter 201 and makeup water pump 2. Water in main water tank 3 passes through second filter 202 and is pressurized by high-pressure plunger pump 4 to the pressure required for normal operation and accident conditions in the nuclear power plant, thus regulating the pressure within the flange test section 14. The high-pressure water flowing out of high-pressure plunger pump 4 is divided into two branches. One branch returns to main water tank 3 via third high-pressure regulating valve 303 and cooler 6 for auxiliary pressure regulation. The other branch flows out through second high-pressure regulating valve 302 and mass flow meter 5, splitting into two branches. Water in one branch is heated by preheater 7 and then flows out via the main flow branch or temperature rapid switching branch. The other branch contains unheated cold water. After flowing out through the cooling water branch, the water is regulated by valves in the main flow branch, the rapid temperature switching branch, and the cooling water branch to meet the needs of slow and rapid temperature rise and fall during normal operation and accident conditions of the nuclear power plant. Water from the second high-pressure shut-off valve 502 and the third high-pressure shut-off valve 503 passes through the condensation system and carries away the heat from the preheating system and the test section system through the condenser 8. Water from the secondary side outlet of the condenser 8 absorbs the heat in the test section system through the cooling tower 11 and is discharged into the atmosphere. Water in the condensate tank 12 continuously flows back to the secondary side inlet of the condenser 8 through the cooling pump 13 and the fourth filter 204. Water from the primary side outlet of the condenser 8 flows back to the main water tank 3, forming a complete test system. This test system simulates the transient temperature and pressure shocks experienced inside the pipe flange during normal operation and accident conditions of the nuclear power plant.

[0016] The process of slow temperature rise and slow temperature fall within the pipe flange test section 14: By opening the first high-pressure shut-off valve 501 and the third high-pressure shut-off valve 503, the main flow branch is activated, and the water from the outlet of the preheater 7 flows through the pipe flange test section 14. By adjusting the electric heating power of the preheater 7, the inlet water temperature of the pipe flange test section is changed, ultimately achieving the adjustment requirements of slow temperature rise and slow temperature fall during normal operation and accident conditions of the nuclear power plant.

[0017] The rapid temperature rise process within the pipe flange test section 14: First, the main flow branch is activated, allowing water flowing from the preheater 7 to pass through the pipe flange test section 14. Then, the second high-pressure shut-off valve 502 is opened and the third high-pressure shut-off valve 503 is closed, activating the rapid temperature switching branch. At this time, water flowing from the preheater 7 flows into the condenser 8 only through the second high-pressure shut-off valve 502. By increasing the electric heating power of the preheater 7, the temperature of the water flowing through the second high-pressure shut-off valve 502 is raised to the target high temperature. Then, the third high-pressure shut-off valve 503 is opened and the second high-pressure shut-off valve 502 is closed. The high-temperature water heated by the preheater 7 flows through the pipe flange test section 14 instantly, ultimately achieving the regulation requirement for rapid temperature rise during normal operation and accident conditions of the nuclear power plant.

[0018] The rapid temperature drop process within the pipe flange test section 14 involves several steps: First, the main flow branch is activated, allowing water from the preheater 7 to pass through the pipe flange test section 14. Then, the second high-pressure shut-off valve 502 is opened, and the third high-pressure shut-off valve 503 is closed, activating the rapid temperature switching branch to ensure the water in the preheater remains in a flowing state. Finally, the first high-pressure regulating valve 301 is opened, activating the cold water injection branch. At this point, cold water flowing from the mass flow meter 5, which has not been heated by the preheater 7, directly enters the pipe flange test section 14 from the cold water injection branch for rapid cooling. The rate of rapid temperature drop is adjusted by regulating the opening of the first high-pressure regulating valve 301, ultimately meeting the regulation requirements for the rapid temperature drop rate during normal operation and accident conditions of the nuclear power plant.

[0019] The beneficial effects of this invention are:

[0020] 1. The test system and method described in this invention simulate the impact of instantaneous temperature and pressure changes on the pipe flange structure of a nuclear power plant under normal operation and accident conditions.

[0021] 2. The test uses a preheater to heat the water at the inlet of the test section of the inflow pipe flange. By constructing a main flow branch, a rapid temperature switching branch, and a cold water injection branch, the test achieves slow and rapid temperature rise and fall.

[0022] 3. The established high-temperature and high-pressure water circuit system can be used to study various types of structures under high-temperature and high-pressure steady-state or transient conditions. Only the test section needs to be modified according to the size, making it widely applicable. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the test system of the present invention;

[0024] Figure 2 This is a schematic diagram of the pipe flange test section of the present invention.

[0025] Figure reference numerals: 1-Makeup water tank, 2-Makeup water pump, 3-Main water tank, 4-High-pressure plunger pump, 5-Mass flow meter, 6-Cooler, 7-Preheater, 8-Condenser, 9-Relief valve, 10-Safety valve, 11-Cooling tower, 12-Condensate tank, 13-Cooling pump, 14-Pipe flange test section, 201-First filter, 202-Second filter, 203-Third filter, 204-Fourth filter, 301-First high-pressure regulating valve, 302-Second high-pressure regulating valve, 303-Third high-pressure regulating valve, 304-Fourth high-pressure regulating valve, 501-First high-pressure shut-off valve, 502-Second high-pressure shut-off valve, 503-Third high-pressure shut-off valve.

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments:

[0027] like Figure 1 As shown, the present invention provides a simulation test system and method for normal operation and accident conditions of nuclear power plant pipe flanges, including a water supply system, a preheating system, a test section system, a temperature control system, and a condensation system.

[0028] like Figure 1 As shown, the water supply system includes a makeup water tank 1, a first filter 201, a makeup water pump 2, a main water tank 3, a second filter 202, a high-pressure plunger pump 4, a second high-pressure regulating valve 302, a third high-pressure regulating valve 303, a mass flow meter 5, and a cooler 6. The first filter 201 and makeup water pump 2 are connected to a pipe downstream of the makeup water tank 1, receiving water from the outlet of the first filter 201 upstream and entering the main water tank 3 downstream. The second filter 202 is connected to a pipe downstream of the main water tank 3. The high-pressure plunger pump 4 receives water from the outlet of the second filter 202 upstream, pressurizes it, and then splits it into two branches. One branch connects to the third high-pressure regulating valve 303 and flows to the cooler 6. Water from the outlet of the cooler 6 enters the main water tank 3. The other branch connects to the second high-pressure regulating valve 302 and flows to the mass flow meter 5 to detect the flow rate, continuously supplying the deionized water required for the entire test section system. The pressure value of the water in the test section system is adjusted by regulating the operating frequency of the high-pressure plunger pump 4, simulating the pressure regulation requirements under normal operation and accident conditions of a nuclear power plant.

[0029] like Figure 1 As shown, the preheating system includes a preheater 7. Water from the outlet of the mass flow meter 5 in the water supply system flows out in two branches. One branch flows to the cold water injection branch of the temperature control system, and the other branch flows to the preheater 7 for heating. The preheater 7 is heated by a two-point heating method, with copper electrodes at both ends. It is directly energized by low voltage and high current, and the voltage is continuously adjusted by an autotransformer. The temperature of the water at the inlet of the test section system is adjusted by changing the electric heating power value to simulate the temperature adjustment requirements under normal operation and accident conditions of a nuclear power plant.

[0030] like Figure 1As shown, the temperature control system includes a main flow branch, a rapid temperature switching branch, and a cooling water injection branch, simulating the slow and rapid temperature rise and fall processes under normal operation and accident conditions of a nuclear power plant. The main flow branch includes the pipeline connecting the outlet of preheater 7 to the flange test section 14 and the pipeline connecting the flange test section 14 to the condensing system. Water from the outlet of preheater 7 in the preheating system enters the first high-pressure shut-off valve 501, and water from the outlet of the first high-pressure shut-off valve 501 enters the flange test section 14 and then flows into the condensing system through the third high-pressure shut-off valve 503. The rapid temperature switching branch is the pipeline connecting the outlet of preheater 7 to the condensing system. Water from the outlet of preheater 7 in the preheating system enters the second high-pressure shut-off valve 502 and then flows into the condensing system. The cooling water injection branch is the pipeline connecting the outlet of mass flow meter 5 to the flange test section 14. Water from the outlet of mass flow meter 5 in the water supply system enters the first high-pressure regulating valve 301 and then flows into the flange test section 14.

[0031] like Figure 1 As shown, the process of slow temperature rise and slow temperature fall within the pipe flange test section 14 is as follows: by opening the first high-pressure shut-off valve 501 and the third high-pressure shut-off valve 503, the main flow branch is activated, and the water from the outlet of the preheater 7 flows through the pipe flange test section 14. By adjusting the electric heating power of the preheater 7, the inlet water temperature of the pipe flange test section is changed, ultimately achieving the adjustment requirements of slow temperature rise and slow temperature fall during normal operation and accident conditions of the nuclear power plant.

[0032] like Figure 1 As shown, the rapid temperature rise process within the pipe flange test section 14 is as follows: First, the main flow branch is activated, allowing water flowing from the preheater 7 to pass through the pipe flange test section 14. Then, the second high-pressure shut-off valve 502 is opened and the third high-pressure shut-off valve 503 is closed, activating the rapid temperature switching branch. At this time, water flowing from the preheater 7 flows into the condenser 8 only through the second high-pressure shut-off valve 502. By increasing the electric heating power of the preheater 7, the temperature of the water flowing through the second high-pressure shut-off valve 502 is raised to the target high temperature. Then, the third high-pressure shut-off valve 503 is opened and the second high-pressure shut-off valve 502 is closed. The high-temperature water heated by the preheater 7 flows through the pipe flange test section 14 instantly, ultimately achieving the regulation requirement for rapid temperature rise during normal operation and accident conditions of the nuclear power plant.

[0033] like Figure 1As shown, the rapid temperature drop process within the pipe flange test section 14 is as follows: First, the main flow branch is activated, allowing water flowing from the preheater 7 to pass through the pipe flange test section 14. Then, the second high-pressure shut-off valve 502 is opened and the third high-pressure shut-off valve 503 is closed, activating the rapid temperature switching branch to ensure that the water in the preheater is in a flowing state. Finally, the first high-pressure regulating valve 301 is opened, activating the cold water injection branch. At this time, the cold water flowing from the mass flow meter 5, which has not been heated by the preheater 7, directly enters the pipe flange test section 14 from the cold water injection branch for rapid cooling. The rate of rapid temperature drop is adjusted by regulating the valve opening of the first high-pressure regulating valve 301, ultimately achieving the regulation requirements of the rapid temperature drop rate during normal operation and accident conditions of the nuclear power plant.

[0034] like Figure 1 As shown, the condensation system includes a condenser 8, a cooling tower 11, a condensate tank 12, a cooling pump 13, a third filter 203, a fourth filter 204, and a fourth high-pressure regulating valve 304. Water from the second high-pressure shut-off valve 502 and the third high-pressure shut-off valve 503 enters the primary side of the condenser 8 through the primary side inlet. The secondary side outlet of the condenser 8 is connected to the cooling tower 11. The water cooled by the cooling tower 11 is stored in the condensate tank 12. The water stored in the condensate tank 12 is then cooled by the fourth high-pressure regulating valve 304 under the action of the cooling pump 13. The filter 204 flows into the secondary inlet of the condenser 8. Water is used as the circulating coolant on the secondary side of the condenser 8 to discharge the heat of the high-temperature water at the outlet of the test section system to the secondary side of the condenser, thus cooling the water entering the primary side of the condenser from the outlet of the test section system. The water at the outlet of the primary side of the condenser 8 passes through the third filter 203 and the fourth high-pressure regulating valve 304 and enters the main water tank 3 of the water supply system. A relief valve 9 and a safety valve 10 are connected between the primary outlet of the condenser 8 and the third filter 203 to ensure the safety of the test circuit.

[0035] like Figure 2 As shown, the test section system includes a pipe flange test section 14, which consists of a flange with connecting pipes. In order to measure the temperature and pressure at the center of the flange, temperature measuring points and pressure measuring points are set at the inlet and outlet of the flange, respectively. The average value of the two values ​​at the inlet and outlet is taken to obtain the temperature and pressure values ​​at the center of the flange.

[0036] The test method for the nuclear power plant pipe flange normal operation and accident condition simulation test system described in this invention is as follows:

[0037] Deionized water from the water purification system is stored in makeup water tank 1. Water in makeup water tank 1 is pumped into main water tank 3 via first filter 201 and makeup water pump 2. Water in main water tank 3 passes through second filter 202 and is pressurized by high-pressure plunger pump 4 to the pressure required for normal operation and accident conditions in the nuclear power plant, thus regulating the pressure within the flange test section 14. The high-pressure water flowing out of high-pressure plunger pump 4 is divided into two branches. One branch returns to main water tank 3 via third high-pressure regulating valve 303 and cooler 6 for auxiliary pressure regulation. The other branch flows out through second high-pressure regulating valve 302 and mass flow meter 5, splitting into two branches. Water in one branch is heated by preheater 7 and then flows out via the main flow branch or temperature rapid switching branch. The other branch contains unheated cold water. After flowing out through the cooling water branch, the water is regulated by valves in the main flow branch, the rapid temperature switching branch, and the cooling water branch to meet the needs of slow and rapid temperature rise and fall during normal operation and accident conditions of the nuclear power plant. Water from the second high-pressure shut-off valve 502 and the third high-pressure shut-off valve 503 passes through the condensation system and carries away the heat from the preheating system and the test section system through the condenser 8. Water from the secondary side outlet of the condenser 8 absorbs the heat in the test section system through the cooling tower 11 and is discharged into the atmosphere. Water in the condensate tank 12 continuously flows back to the secondary side inlet of the condenser 8 through the cooling pump 13 and the fourth filter 204. Water from the primary side outlet of the condenser 8 flows back to the main water tank 3, forming a complete test system. This test system simulates the transient temperature and pressure shocks experienced inside the pipe flange during normal operation and accident conditions of the nuclear power plant.

[0038] The above description is only used to illustrate the present invention and should not be construed as limiting the specific embodiments of the present invention to this. For those skilled in the art, any changes and modifications to the above embodiments that are within the essential spirit and scope of the present invention should be considered as being within the scope of the claims of the present invention.

Claims

1. A simulation test system for normal operation and accident conditions of nuclear power plant pipe flanges, characterized in that: The test system includes a water supply system, a preheating system, a test section system, a temperature control system, and a condensation system; The water supply system includes a water supply tank (1), a first filter (201), a water supply pump (2), a main water tank (3), a second filter (202), a high-pressure plunger pump (4), a second high-pressure regulating valve (302), a third high-pressure regulating valve (303), a mass flow meter (5), and a cooler (6). The water supply tank (1) is connected to the first filter (201) and the water supply pump (2) via a downstream pipe, receiving water from the outlet of the first filter (201) upstream and entering the main water tank (3) downstream. The main water tank (3) is connected to the second filter (202) and the high-pressure plunger pump (4) via a downstream pipe. The water from the outlet of the second filter (202) upstream is pressurized and then flows out in two branches. One branch is connected to the third high-pressure regulating valve (303) and flows to the cooler (6). The water from the outlet of the cooler (6) enters the main water tank (3). The other branch is connected to the second high-pressure regulating valve (302) and flows to the mass flow meter (5) to detect the flow rate value, so as to continuously supply the deionized water required for the test for the entire test section system. The pressure value of the water in the test section system is adjusted by adjusting the working frequency value of the high-pressure plunger pump (4) to simulate the pressure value adjustment requirements under normal operation and accident conditions of the nuclear power plant. The preheating system includes a preheater (7). Water from the outlet of the mass flow meter (5) in the water supply system flows out through two branches. One branch flows to the cold water branch of the temperature control system, and the other branch flows to the preheater (7) for heating. The preheater (7) is heated by a two-point heating method. Copper electrodes are provided at both ends. The preheater is directly energized by a low voltage and high current method. The voltage is continuously adjusted by an autotransformer. The temperature of the water at the inlet of the test section system is adjusted by changing the electric heating power value to simulate the temperature adjustment requirements under normal operation and accident conditions of a nuclear power plant. The test section system includes a pipe flange test section (14), which consists of a flange with connecting pipes. In order to measure the temperature and pressure at the center of the flange, temperature measuring points and pressure measuring points are set at the inlet and outlet of the flange respectively. The average value of the two values ​​at the inlet and outlet is taken to obtain the temperature and pressure values ​​at the center of the flange. The temperature control system includes a main flow branch, a rapid temperature switching branch, and a cooling water injection branch, simulating the slow and rapid temperature rise and fall processes under normal operation and accident conditions of a nuclear power plant. The main flow branch includes the pipeline connecting the preheater (7) outlet to the flange test section (14) and the pipeline connecting the flange test section (14) to the condensing system. Water from the preheater (7) outlet of the preheating system enters the first high-pressure shut-off valve (501), and water from the outlet of the first high-pressure shut-off valve (501) enters the flange test section (14) and then flows into the condensing system through the third high-pressure shut-off valve (503). The rapid temperature switching branch is the pipeline connecting the preheater (7) outlet to the condensing system. Water from the preheater (7) outlet of the preheating system enters the second high-pressure shut-off valve (502) and then flows into the condensing system. The cooling water injection branch is the pipeline connecting the mass flow meter (5) outlet to the flange test section (14). Water from the mass flow meter (5) outlet of the water supply system enters the first high-pressure regulating valve (301) and then flows into the flange test section (14). The condensation system includes a condenser (8), a cooling tower (11), a condensate tank (12), a cooling pump (13), a third filter (203), a fourth filter (204), and a fourth high-pressure regulating valve (304). Water from the second high-pressure shut-off valve (502) and the third high-pressure shut-off valve (503) enters the primary side of the condenser (8) through the primary side inlet. The secondary side outlet of the condenser (8) is connected to the cooling tower (11). The water cooled by the cooling tower (11) is stored in the condensate tank (12). In the process, the water stored in the condensate tank (12) flows into the secondary side inlet of the condenser (8) through the fourth filter (204) under the action of the cooling pump (13). The secondary side of the condenser (8) uses water as a circulating coolant to discharge the heat of the high temperature water at the outlet of the test section system to the secondary side of the condenser, thereby completing the cooling of the water entering the primary side of the condenser from the outlet of the test section system. The water at the outlet of the primary side of the condenser (8) enters the main water tank (3) of the water supply system through the third filter (203) and the fourth high pressure regulating valve (304).

2. The nuclear power plant pipe flange normal operation and accident condition simulation test system according to claim 1, characterized in that: A vent valve (9) and a safety valve (10) are connected between the primary outlet of the condenser (8) and the third filter (203) to ensure the safety of the test section system.

3. The nuclear power plant pipe flange normal operation and accident condition simulation test system according to claim 1, characterized in that: The first high-pressure regulating valve (301), the second high-pressure regulating valve (302), the third high-pressure regulating valve (303), the fourth high-pressure regulating valve (304), the first high-pressure shut-off valve (501), the second high-pressure shut-off valve (502), and the third high-pressure shut-off valve (503) are adjusted in opening and closing according to temperature regulation needs throughout the entire cycle of normal operation and accident condition simulation test of nuclear power plant pipe flanges. Since the temperature changes relatively rapidly in actual nuclear power plant accident conditions, it is necessary to use electric valves with high safety and efficiency.

4. The test method of the nuclear power plant pipe flange normal operation and accident condition simulation test system according to any one of claims 1-3, characterized in that: Specifically as follows: Deionized water from the water purification system is stored in the makeup water tank (1). The water in the makeup water tank (1) is pumped into the main water tank (3) through the first filter (201) and the makeup water pump (2). The water in the main water tank (3) is pressurized to the required pressure value under normal operation and accident conditions of the nuclear power plant by the high-pressure plunger pump (4) through the second filter (202), so as to meet the pressure adjustment requirements in the pipe flange test section (14). The high-pressure water flowing out through the high-pressure plunger pump (4) is divided into two branches. One branch returns to the main water tank (3) through the third high-pressure regulating valve (303) and the cooler (6) for auxiliary pressure adjustment. The other branch flows out through the second high-pressure regulating valve (302) and the mass flow meter (5) into two branches. The water in one branch is heated by the preheater (7) and then flows out through the main flow branch or the temperature rapid switching branch. The water in the other branch is not heated. Hot cold water flows out through the cold water injection branch. According to the valve regulation process of the main flow branch, the temperature rapid switching branch, and the cold water injection branch, the slow rise and fall and rapid rise and fall of temperature under normal operation and accident conditions of the nuclear power plant are realized. The water from the second high pressure shut-off valve (502) and the third high pressure shut-off valve (503) passes through the condensation system and carries away the heat of the preheating system and the test section system through the condenser (8). The water at the secondary side outlet of the condenser (8) absorbs the heat in the test section system through the cooling tower (11) and is discharged into the atmosphere. The water in the condensate tank (12) continuously flows back to the secondary side inlet of the condenser (8) through the cooling pump (13) and the fourth filter (204). The water at the primary side outlet of the condenser (8) flows back to the main water tank (3) to form a complete test system. This test system simulates the transient impact of temperature and pressure inside the pipe flange under normal operation and accident conditions of the nuclear power plant.

5. The test method according to claim 4, characterized in that: The process of slow temperature rise and slow temperature fall in the pipe flange test section (14): By opening the first high pressure shut-off valve (501) and the third high pressure shut-off valve (503), the main flow branch is activated, and the water at the outlet of the preheater (7) flows through the pipe flange test section (14). By adjusting the electric heating power of the preheater (7), the inlet water temperature of the pipe flange test section is changed, and finally the adjustment requirements of slow temperature rise and slow temperature fall during normal operation and accident conditions of the nuclear power plant are realized.

6. The test method according to claim 4, characterized in that: The rapid temperature rise process in the pipe flange test section (14): First, the main flow branch is activated so that the water flowing out of the preheater (7) passes through the pipe flange test section (14). Then, the second high-pressure shut-off valve (502) is opened and the third high-pressure shut-off valve (503) is closed. The rapid temperature switching branch is activated. At this time, the water flowing out of the preheater (7) flows into the condenser (8) only through the second high-pressure shut-off valve (502). By increasing the electric heating power of the preheater (7), the temperature of the water flowing through the second high-pressure shut-off valve (502) is raised to the target high temperature. Then, the third high-pressure shut-off valve (503) is opened and the second high-pressure shut-off valve (502) is closed. The high-temperature water heated by the preheater (7) flows through the pipe flange test section (14) instantly, and finally the regulation requirements for rapid temperature rise during normal operation and accident conditions of the nuclear power plant are realized.

7. The test method according to claim 4, characterized in that: The rapid temperature drop process in the pipe flange test section (14): First, the main flow branch is activated so that the water flowing out of the preheater (7) passes through the pipe flange test section (14). Then, the second high pressure shut-off valve (502) is opened and the third high pressure shut-off valve (503) is closed. The rapid temperature switching branch is activated to ensure that the water in the preheater is in a flowing state. Finally, the first high pressure regulating valve (301) is opened to activate the cold water injection branch. At this time, the cold water flowing out from the mass flow meter (5) without being heated by the preheater (7) directly enters the pipe flange test section (14) from the cold water injection branch for rapid cooling. The rate of rapid temperature drop is adjusted by adjusting the valve opening of the first high pressure regulating valve (301), and finally the adjustment requirements of the rapid temperature drop rate during normal operation and accident conditions of the nuclear power plant are achieved.

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