Nuclear power plant pipe flange normal operation and accident condition simulation test system and method

Abstract

The invention relates to a nuclear power plant pipe flange normal operation and accident condition simulation test system and method, the system comprises a water supply system, a preheating system, a test section system, a temperature adjusting system and a condensation system, the water supply system comprises a water supplementing tank, a filter, a water supplementing pump, a main water tank, a high-pressure plunger pump, a high-pressure adjusting valve, a cooler and a mass flow meter; the preheating system comprises a preheater, the test section system comprises a pipe flange test section, the temperature adjusting system comprises a main circulation branch, a temperature rapid switching branch and a cold water injection branch, and the condensation system comprises a condenser, a cooling tower, a condensation water tank, a cooling pump, a filter, a safety valve and a release valve. The test system can simulate temperature and pressure transient impact on the interior of a pipe flange structure under normal operation and accident conditions of a nuclear power plant.

Description

Technical Field

[0001] The invention belongs to the technical field of high temperature and high pressure testing of pipe flanges, and in particular relates to a normal operation and accident condition simulation testing system and method for pipe flanges in a nuclear power plant. Background Art

[0002] In the process of research, development and application of nuclear-grade equipment, it is necessary to test the safety of the equipment under long-term normal operation conditions and sudden accident conditions. Accident conditions in nuclear power plants are accompanied by rapid rise and fall of temperature and pressure. The pipe flange structure of a nuclear power plant is the main safety barrier of a nuclear power plant. Studying the impact of temperature and pressure transients on the pipe flange structure under normal operation and accident conditions is of great significance to the safety and economy of nuclear power plants.

[0003] At present, domestic and foreign scholars have carried out a large number of tests and finite element analysis on the test of pipe flange structure. However, most of the current tests are aimed at measuring the medium of high-pressure inert gas or high-pressure normal temperature water, and there are few studies on transient working conditions of pipe flanges under high temperature and high pressure. Therefore, the test research of pipe flange structure under normal operation and accident conditions of nuclear power plants can analyze the safety of pipe flange structure under high temperature and pressure shock during the operation of nuclear power plants. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a nuclear power plant pipe flange normal operation and accident condition simulation test system and method, which can simulate the impact of the nuclear reactor under normal operation and accident conditions on the pipe flange caused by the instantaneous drastic changes in temperature and pressure, and has guiding significance for the design and operation safety of the nuclear reactor.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A nuclear power plant pipe flange normal operation and accident condition simulation test system, including a water supply system, a preheating system, a test section system, a temperature adjustment system, and a condensation system;

[0007] The water supply system comprises 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 downstream pipeline of the water supply tank 1 is connected with the first filter 201 and the water supply pump 2, and receives water from the outlet of the upstream first filter 201 to enter the downstream main water tank 3. The downstream pipeline of the main water tank 3 is connected with the second filter 202. The high-pressure plunger pump 4 receives water from the outlet of the upstream second filter 202 and flows out in two branches after pressurization, one of which is connected to the third high-pressure regulating valve 303 to flow to the cooler 6, and the water at the outlet of the cooler 6 enters the main water tank 3, and the other branch is connected to the second high-pressure regulating valve 302 to flow to the mass flow meter 5 to detect the flow value, so as to continuously supply the deionized water required for the test for the entire test section system, and adjust the pressure value of the water in the test section system by adjusting the working frequency value of the high-pressure plunger pump 4, so as to simulate the pressure value adjustment requirements under normal operation and accident conditions of the nuclear power plant;

[0008] The preheating system includes a preheater 7. The water from the outlet of the mass flowmeter 5 in the water supply system flows out in two branches, one of which flows to the cold water injection branch of the temperature control system, and the other flows to the preheater 7 for heating. The heating method of the preheater 7 is to adopt a two-point heating method, with copper electrodes at both ends, and to directly heat with low voltage and high current. The voltage is continuously adjusted by the autotransformer, and the temperature value of the water at the inlet of the test section system is adjusted by changing the electric heating power value, simulating the temperature value adjustment requirements under normal operation and accident conditions of the nuclear power plant;

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

[0010] The temperature regulating system includes a main flow branch, a temperature rapid switching branch and a cold water injection branch, which simulate the slow rise and fall and rapid rise and fall process of the temperature under normal operation and accident conditions of the nuclear power plant; the main flow branch includes a pipeline connecting the outlet of the preheater 7 to the pipe flange test section 14 and a pipeline connecting the pipe flange test section 14 to the condensation system, and the water from the outlet of the preheater 7 of the preheating system enters the first high-pressure stop valve 501, and the water from the outlet of the first high-pressure stop valve 501 enters the pipe flange test section 14 and then flows into the condensation system through the third high-pressure stop valve 503; the temperature rapid switching branch is a pipeline connecting the outlet of the preheater 7 to the condensation system, and the water from the outlet of the preheater 7 of the preheating system enters the second high-pressure stop valve 502 and then flows into the condensation system; the cold water injection branch is a pipeline connecting the outlet of the mass flowmeter 5 to the pipe flange test section 14, and the water from the outlet of the mass flowmeter 5 of the water supply system enters the first high-pressure regulating valve 301 and then flows into the pipe flange test section 14;

[0011] The condensation system includes a condenser 8, a cooling tower 11, a condensation water tank 12, a cooling pump 13, a third filter 203, a fourth filter 204 and a fourth high-pressure regulating valve 304. The water from the second high-pressure stop valve 502 and the third high-pressure stop valve 503 enters the primary side of the condenser through the primary side inlet of the condenser 8. 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 condensation water tank 12. The water stored in the condensation water 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 primary side outlet of the condenser 8 passes through the third filter 203 and the fourth high-pressure regulating valve 304 and enters the main water tank 1 of the water supply system.

[0012] A discharge valve 9 and a safety valve 10 are connected between the primary side 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 stop valve 501, the second high-pressure stop valve 502, and the third high-pressure stop valve 503 are opened and closed according to the temperature regulation needs during the entire period of normal operation of the nuclear power plant pipe flange and the accident condition simulation test. Since the temperature changes relatively rapidly under actual nuclear power plant accident conditions, it is necessary to use safe and efficient electric valves.

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

[0015] Deionized water from the water purification system is stored in the water supply tank 1. The water in the water supply tank 1 is pumped into the main water tank 3 through the first filter 201 and the water supply pump 2. The water in the main water tank 3 passes through the second filter 202 and is pressurized by the high-pressure plunger pump 4 to the required pressure value under normal operation and accident conditions of the nuclear power plant, so as to achieve the pressure value adjustment demand in the pipe flange test section 14. The high-pressure water flowing out of the high-pressure plunger pump 4 is divided into two branches, one of which returns to the main water tank 3 through the third high-pressure regulating valve 303 and the cooler 6 for auxiliary pressure adjustment, and the other branch flows out through the second high-pressure regulating valve 302 and the mass flow meter 5. The water in one branch is heated by the preheater 7 and flows out after passing through the main flow branch or the temperature rapid switching branch. The unheated cold water in the other branch, The water flows out through the cold water injection branch, and according to the valve adjustment process of the main flow branch, the temperature rapid switching branch, and the cold water injection branch, the slow and rapid temperature rise and fall adjustment requirements of the nuclear power plant under normal operation and accident conditions are realized. The water from the second high-pressure stop valve 502 and the third high-pressure stop valve 503 passes through the condensation system, and takes 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 condensation water tank 12 continuously flows back to the secondary side inlet of the condenser 8 through the cooling pump 13 and the fourth filter 204, and 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. The test system simulates the transient temperature and pressure impact on the inside of the pipe flange under normal operation and accident conditions of the nuclear power plant.

[0016] The process of slow temperature rise and slow temperature drop in the pipe flange test section 14: by opening the first high-pressure stop valve 501 and the third high-pressure stop valve 503, the main flow branch is enabled, 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 regulation requirements of slow temperature rise and slow temperature drop during normal operation and accident conditions of the nuclear power plant are realized.

[0017] The rapid temperature rise process in the pipe flange test section 14: first, the main flow branch is activated to allow the water flowing out of the preheater 7 to pass through the pipe flange test section 14, then the second high-pressure stop valve 502 is opened, the third high-pressure stop valve 503 is closed, and the temperature rapid switching branch is activated. At this time, the water flowing out of the preheater 7 only flows into the condenser 8 through the second high-pressure stop valve 502. By increasing the electric heating power of the preheater 7, the temperature of the water flowing through the second high-pressure stop valve 502 is raised to the target high temperature, and then the third high-pressure stop valve 503 is opened and the second high-pressure stop valve 502 is closed. The high-temperature water heated by the preheater 7 instantly flows through the pipe flange test section 14, and finally the regulation requirements for rapid temperature rise during normal operation and accident conditions of the nuclear power plant are met.

[0018] The temperature in the pipe flange test section 14 drops rapidly; first, the main flow branch is activated to allow the water flowing out of the preheater 7 to pass through the pipe flange test section 14, then the second high-pressure stop valve 502 is opened, the third high-pressure stop valve 503 is closed, and the temperature rapid switching branch is activated to ensure that the water in the preheater is in a circulation state, and finally the first high-pressure regulating valve 301 is opened, and the cold water injection branch is activated. At this time, the cold water flowing out of the mass flow meter 5 that 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, wherein the rate of rapid temperature drop is adjusted by adjusting the valve opening of the first high-pressure regulating valve 301, and finally the regulation demand for the rapid temperature drop rate during normal operation and accident conditions of the nuclear power plant is achieved.

[0019] The beneficial effects of the present invention are:

[0020] 1. The test system and method described in the present invention simulate the impact caused by the instantaneous changes in temperature and pressure of 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 flowing into the inlet of the test section of the pipe flange. By constructing a main flow branch, a temperature rapid switching branch, and a cold water injection branch, the temperature can be slowly and quickly raised or lowered.

[0022] 3. The established high-temperature and high-pressure water circuit system can be used to study the tests of various types of structures under high-temperature and high-pressure steady-state or transient conditions. It only needs to modify the test section according to the size, and has a wide range of applicability. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0025] Figure markings: 1-water make-up tank, 2-water make-up pump, 3-main water tank, 4-high-pressure plunger pump, 5-mass flow meter, 6-cooler, 7-preheater, 8-condenser, 9-discharge valve, 10-safety valve, 11-cooling tower, 12-condensate water 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 stop valve, 502-second high-pressure stop valve, 503-third high-pressure stop valve.

[0026] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments:

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

[0028] like Figure 1 As shown, 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 first filter 201 and the water supply pump 2 are connected to the downstream pipeline of the water supply tank 1, and receive water from the outlet of the first filter 201 upstream to enter the downstream main water tank 3. The downstream pipeline 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 and flows out in two branches after pressurization. One branch is connected to the third high-pressure regulating valve 303 to flow to the cooler 6. The water at the outlet of the cooler 6 enters the main water tank 3, and the other branch is connected to the second high-pressure regulating valve 302 to flow to the mass flow meter 5 to detect the flow 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, so as to simulate the pressure value adjustment requirements under normal operation and accident conditions of the nuclear power plant.

[0029] like Figure 1 As shown, the preheating system includes a preheater 7. The water from the outlet of the mass flow meter 5 in the water supply system flows out in two branches, one of which flows to the cold water injection branch of the temperature control system, and the other flows to the preheater 7 for heating. The heating method of the preheater 7 is a two-point heating method. Copper electrodes are provided at both ends. Low voltage and high current are used for direct heating. The voltage is continuously adjusted by an autotransformer. The temperature value of the water at the inlet of the test section system is adjusted by changing the electric heating power value, simulating the temperature value adjustment requirements under normal operation and accident conditions of the nuclear power plant.

[0030] like Figure 1As shown, the temperature regulating system includes a main flow branch, a temperature rapid switching branch, and a cold water injection branch, which simulate the slow rise and fall and rapid rise and fall processes of the temperature under normal operation and accident conditions of the nuclear power plant; the main flow branch includes a pipeline connecting the outlet of the preheater 7 to the pipe flange test section 14 and a pipeline connecting the pipe flange test section 14 to the condensation system, and the water from the outlet of the preheater 7 of the preheating system enters the first high-pressure stop valve 501, and the water from the outlet of the first high-pressure stop valve 501 enters the pipe flange test section 14 and then flows into the condensation system through the third high-pressure stop valve 503; the temperature rapid switching branch is a pipeline connecting the outlet of the preheater 7 to the condensation system, and the water from the outlet of the preheater 7 of the preheating system enters the second high-pressure stop valve 502 and then flows into the condensation system; the cold water injection branch is a pipeline connecting the outlet of the mass flowmeter 5 to the pipe flange test section 14, and the water from the outlet of the mass flowmeter 5 of the water supply system enters the first high-pressure regulating valve 301 and then flows into the pipe flange test section 14.

[0031] like Figure 1 As shown, the temperature in the pipe flange test section 14 slowly rises and slowly drops in the process: by opening the first high-pressure stop valve 501 and the third high-pressure stop valve 503, the main flow branch is enabled, 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 regulation requirements of slowly rising and slowly dropping the temperature during the normal operation and accident conditions of the nuclear power plant are realized.

[0032] like Figure 1 As shown, the temperature in the pipe flange test section 14 rises rapidly: first, the main flow branch is enabled to allow the water flowing out of the preheater 7 to pass through the pipe flange test section 14, then the second high-pressure stop valve 502 is opened, the third high-pressure stop valve 503 is closed, and the temperature rapid switching branch is enabled. At this time, the water flowing out of the preheater 7 flows into the condenser 8 only through the second high-pressure stop valve 502. By increasing the electric heating power of the preheater 7, the temperature of the water flowing through the second high-pressure stop valve 502 is raised to the target high temperature, the third high-pressure stop valve 503 is opened, and the second high-pressure stop valve 502 is closed. The high-temperature water heated by the preheater 7 instantly flows through the pipe flange test section 14, and finally the regulation requirements for rapid temperature rise during normal operation and accident conditions of the nuclear power plant are met.

[0033] like Figure 1As shown, the temperature in the pipe flange test section 14 drops rapidly during the following steps: first, the main flow branch is enabled to allow the water flowing out of the preheater 7 to pass through the pipe flange test section 14; then, the second high-pressure stop valve 502 is opened, the third high-pressure stop valve 503 is closed, and the temperature rapid switching branch is enabled to ensure that the water in the preheater is in a circulation state; finally, the first high-pressure regulating valve 301 is opened, and the cold water injection branch is enabled. At this time, the cold water flowing out of the mass flow meter 5 that 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; wherein, the rate of rapid temperature drop is adjusted by adjusting the valve opening of the first high-pressure regulating valve 301, thereby ultimately achieving the adjustment requirements for the rate of rapid temperature drop 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 condensation water 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 stop valve 502 and the third high-pressure stop valve 503 enters the primary side of the condenser through the primary side inlet of the condenser 8. 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 condensation water tank 12. The water stored in the condensation water tank 12 is cooled by the cooling pump 13 through the fourth filter 204. The filter 204 flows into the secondary side inlet of the condenser 8. 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 primary side outlet of the condenser 8 passes through the third filter 203 and the fourth high-pressure regulating valve 304 and enters the main water tank 1 of the water supply system. A discharge valve 9 and a safety valve 10 are connected between the primary side 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 is composed of a flange with a connecting pipe. In order to measure the temperature and pressure at the center of the flange, temperature measuring points and pressure measuring points are respectively set at the inlet and outlet of the flange, and the average values ​​of the two values ​​at the inlet and outlet are taken to obtain the temperature value and pressure value of the center of the flange.

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

[0037] Deionized water from the water purification system is stored in the water supply tank 1. The water in the water supply tank 1 is pumped into the main water tank 3 through the first filter 201 and the water supply pump 2. The water in the main water tank 3 passes through the second filter 202 and is pressurized by the high-pressure plunger pump 4 to the required pressure value under normal operation and accident conditions of the nuclear power plant, so as to achieve the pressure value adjustment demand in the pipe flange test section 14. The high-pressure water flowing out of the high-pressure plunger pump 4 is divided into two branches, one of which returns to the main water tank 3 through the third high-pressure regulating valve 303 and the cooler 6 for auxiliary pressure adjustment, and the other branch flows out through the second high-pressure regulating valve 302 and the mass flow meter 5. The water in one branch is heated by the preheater 7 and flows out after passing through the main flow branch or the temperature rapid switching branch. The unheated cold water in the other branch, The water flows out through the cold water injection branch, and according to the valve adjustment process of the main flow branch, the temperature rapid switching branch, and the cold water injection branch, the slow and rapid temperature rise and fall adjustment requirements of the nuclear power plant under normal operation and accident conditions are realized. The water from the second high-pressure stop valve 502 and the third high-pressure stop valve 503 passes through the condensation system, and takes 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 condensation water tank 12 continuously flows back to the secondary side inlet of the condenser 8 through the cooling pump 13 and the fourth filter 204, and 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. The test system simulates the transient temperature and pressure impact on the inside of the pipe flange under normal operation and accident conditions of the nuclear power plant.

[0038] The above contents are only used to illustrate the present invention, and it cannot be determined that the specific implementation modes of the present invention are limited to these. For ordinary technicians in this technical field, as long as they are within the essential spirit of the present invention, changes and modifications to the above-mentioned embodiments should be deemed to be within the scope of the claims of the present invention.

Claims

1. A nuclear power plant pipe flange normal operation and accident condition simulation test system, characterized by: The test system includes water supply system, preheating system, test section system, temperature regulation system and condensation system; The water supply system comprises 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 downstream pipeline of the water supply tank (1) is connected to the first filter (201) and the water supply pump (2), and receives water from the outlet of the upstream first filter (201) into the downstream main water tank (3); the downstream pipeline of the main water tank (3) is connected to the second filter (202), and the high-pressure plunger pump (4 ) receives water from the outlet of the second filter (202) upstream and, after pressurization, flows out in two branches, one of which is connected to the third high-pressure regulating valve (303) and flows to the cooler (6). The water at the outlet of the cooler (6) enters the main water tank (3), and 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 value, so as to continuously supply 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 working frequency value of the high-pressure plunger pump (4), so as to simulate the pressure value adjustment requirements under normal operation and accident conditions of the nuclear power plant; The preheating system comprises a preheater (7), water from the outlet of the mass flow meter (5) in the water supply system flows out in two branches, one of which flows to the cold water injection branch of the temperature control system, and the other flows to the preheater (7) for heating. The heating method of the preheater (7) is to adopt a two-point heating method, copper electrodes are provided at both ends, and low voltage and high current are used for direct heating. The voltage is continuously adjusted by an autotransformer, and the temperature value of the water at the inlet of the test section system is adjusted by changing the electric heating power value, so as to simulate the temperature value adjustment requirements under normal operation and accident conditions of the nuclear power plant; The test section system comprises a pipe flange test section (14), which is composed of a flange with a connecting pipe. In order to measure the temperature and pressure at the center of the flange, a temperature measuring point and a pressure measuring point are respectively arranged at the inlet and outlet of the flange, and the average values ​​of the two values ​​at the inlet and outlet are respectively taken to obtain the temperature value and pressure value at the center of the flange; The temperature regulating system comprises a main flow branch, a temperature rapid switching branch and a cold water injection branch, simulating the slow rise and fast rise process of the temperature under normal operation and accident conditions of the nuclear power plant; the main flow branch comprises a pipeline connecting the outlet of the preheater (7) to the pipe flange test section (14) and a pipeline connecting the pipe flange test section (14) to the condensation system, water from the outlet of the preheater (7) of the preheating system enters the first high-pressure stop valve (501), and water from the outlet of the first high-pressure stop valve (501) enters the pipe flange test section (14) and then flows into the condensation system through the third high-pressure stop valve (503); the temperature rapid switching branch is a pipeline connecting the outlet of the preheater (7) to the condensation system, and water from the outlet of the preheater (7) of the preheating system enters the second high-pressure stop valve (502) and then flows into the condensation system; the cold water injection branch is a pipeline connecting the outlet of the mass flow meter (5) to the pipe flange test section (14), and water from the outlet of the mass flow meter (5) of the water supply system enters the first high-pressure regulating valve (301) and then flows into the pipe flange test section (14); The condensation system comprises a condenser (8), a cooling tower (11), a condensation water 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 stop valve (502) and the third high-pressure stop valve (503) enters the primary side of the condenser through the primary side inlet of the condenser (8); the secondary side outlet of the condenser (8) is connected to the cooling tower (11); and the water cooled by the cooling tower (11) is stored in the condensation water tank (12). In the process, the water stored in the condensation water 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 primary side outlet of the condenser (8) passes through the third filter (203) and the fourth high-pressure regulating valve (304) and enters the main water tank (1) of the water supply system.

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

3. A 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 stop valve (501), the second high-pressure stop valve (502), and the third high-pressure stop valve (503) are opened and closed according to the need for temperature regulation during the entire period of normal operation of the nuclear power plant pipe flange and the accident condition simulation test. Since the temperature changes relatively quickly under the actual nuclear power plant accident condition, it is necessary to use electric valves with high safety and efficiency.

4. A test method for a normal operation and accident condition simulation test system of a nuclear power plant pipe flange according to any one of claims 1 to 3, characterized in that: The details are as follows: Deionized water from the water purification system is stored in a water supply tank (1). The water in the water supply tank (1) is pumped into a main water tank (3) through a first filter (201) and a water supply pump (2). The water in the main water tank (3) passes through a second filter (202) and is pressurized to a required pressure value under normal operation and accident conditions of the nuclear power plant by a high-pressure plunger pump (4), so as to meet the pressure value regulation requirements in the pipe flange test section (14). The high-pressure water flowing out of the high-pressure plunger pump (4) is divided into two branches, one of which passes through a third high-pressure regulating valve (303) and a cooler (6) to return to the main water tank (3) for auxiliary pressure regulation, and the other branch passes through a second high-pressure regulating valve (302) and a mass flow meter (5) to flow out in two branches. The water in one branch is heated by a preheater (7) and then flows out through a main flow branch or a temperature rapid switching branch. The water in the other branch that has not been pressurized flows out through a main flow branch or a temperature rapid switching branch. Hot cold water flows out through the cold water injection branch. According to the valve adjustment process of the main flow branch, the temperature rapid switching branch and the cold water injection branch, the slow rise and fast rise and fall adjustment requirements of the temperature under normal operation and accident conditions of the nuclear power plant are realized. The water from the second high-pressure stop valve (502) and the third high-pressure stop valve (503) passes through the condensation system and takes 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 condensation water 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. The test system simulates the temperature and pressure transient impact on the inside of 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 slowly increasing and decreasing the temperature in the pipe flange test section (14) is as follows: by opening the first high-pressure stop valve (501) and the third high-pressure stop valve (503), the main flow branch is enabled, 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 water temperature at the inlet of the pipe flange test section is changed, and finally the regulation requirements of slowly increasing and slowly decreasing the temperature during the normal operation and accident conditions of the nuclear power plant are achieved.

6. The test method according to claim 4, characterized in that: The rapid temperature rise process in the pipe flange test section (14) is as follows: first, the main flow branch is activated to allow water flowing out of the preheater (7) to pass through the pipe flange test section (14); then, the second high-pressure stop valve (502) is opened, the third high-pressure stop valve (503) is closed, and the temperature rapid 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 stop valve (502); by increasing the electric heating power of the preheater (7), the temperature of the water flowing through the second high-pressure stop valve (502) is raised to a target high temperature; then, the third high-pressure stop valve (503) is opened, and the second high-pressure stop valve (502) is closed. The high-temperature water heated by the preheater (7) instantly flows through the pipe flange test section (14), and finally the regulation requirements for rapid temperature rise during normal operation and accident conditions of the nuclear power plant are met.

7. The test method according to claim 4, characterized in that: The temperature in the pipe flange test section (14) is rapidly reduced. First, the main flow branch is activated to allow water flowing out of the preheater (7) to pass through the pipe flange test section (14). Then, the second high-pressure stop valve (502) is opened, the third high-pressure stop valve (503) is closed, and the temperature rapid switching branch is activated to ensure that the water in the preheater is in a circulating state. Finally, the first high-pressure regulating valve (301) is opened and the cold water injection branch is activated. At this time, the cold water flowing out of the mass flow meter (5) and not heated by the preheater (7) directly enters the pipe flange test section (14) from the cold water injection branch for rapid temperature reduction. The valve opening of the first high-pressure regulating valve (301) is adjusted to adjust the rate of rapid temperature reduction, thereby finally achieving the adjustment requirement of the rate of rapid temperature reduction during normal operation and accident conditions of the nuclear power plant.

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