A method for starting up the secondary circuit of a nuclear reactor thermal hydraulic system test

Abstract

The invention discloses a method for starting a secondary circuit of a nuclear reactor thermal hydraulic system test. By coordinating a primary circuit with a secondary circuit and designing reasonable and orderly operation steps, the problem of difficulty in starting the secondary circuit during a high-temperature and high-pressure nuclear reactor thermal hydraulic system test is solved, and the secondary circuit of the system test can be started safely and effectively. During the starting process, the temperature information of the primary circuit is obtained in real time, and the water supply flow rate of the water supply unit of the secondary circuit is adjusted according to the temperature information of the primary circuit. The method closely cooperates with the primary circuit and takes into account the parameter requirements of the secondary circuit equipment during operation, so that the nuclear reactor thermal hydraulic system test can be started safely and stably, providing a data basis for the actual nuclear reactor transient thermal hydraulic system.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear reactor thermal hydraulic system testing, and in particular to a nuclear reactor thermal hydraulic system testing secondary loop starting method. Background Art

[0002] The nuclear reactor thermal hydraulic system test generally includes a primary loop system and a secondary loop system. The secondary loop structure of the system test device is relatively complex and contains many devices. The key to the start-up of the reactor system test lies in the start-up of the secondary loop. The start-up of the secondary loop is closely coupled with the power change of the primary loop, and it involves the process of the loop system changing from pure water to steam. Any carelessness during operation may lead to dangerous physical phenomena such as water hammer and low condenser liquid level. The startup process is complicated and requires a scientific and reasonable startup method to safely and effectively start the secondary loop of the nuclear reactor thermal hydraulic system experiment. Summary of the invention

[0003] The technical problem to be solved by the present invention is that the startup process of the secondary circuit of the nuclear reactor thermal hydraulic system test is closely coupled with the power change of the primary circuit, which makes the startup difficult and involves the process of the circuit system changing from pure water to steam. The operation process may cause dangerous physical phenomena such as water hammer and low condenser liquid level if the operator is not careful. The purpose of the present invention is to provide a method for starting the secondary circuit of the nuclear reactor thermal hydraulic system test, which starts the secondary circuit in combination with the power and temperature changes of the primary circuit to solve the above technical problems.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention provides a method for starting a secondary circuit of a nuclear reactor thermal hydraulic system test, wherein the secondary circuit comprises: a water supply unit, a steam unit and a condenser, wherein the water supply unit, the steam unit and the condenser are connected in sequence to form a circuit; the method for starting the secondary circuit comprises the following steps:

[0006] Step 1: Raise the temperature and pressure of the primary circuit of the nuclear reactor thermal hydraulic system test, and obtain the temperature information of the primary circuit in real time;

[0007] Step 2: Pre-treat the steam unit and condenser of the secondary circuit;

[0008] Step 3: Start the water supply unit of the second circuit, while maintaining the heating rate of the first circuit at V1;

[0009] When the pressure of the condenser exceeds a threshold value, the condenser and the water supply unit are connected so that the cooling water in the water supply unit flows into the condenser; the pressure of the condenser is kept constant;

[0010] Step 4: According to the comparison result between the temperature status information of the first circuit and the reference temperature, the second circuit is adjusted so that the water supply flow rate of the water supply unit reaches the reference flow rate.

[0011] Working principle of this scheme: Due to the power and temperature changes of the primary circuit, the startup of the secondary circuit of the nuclear reactor thermal-hydraulic system test is a complicated process. If the operation is not appropriate during the startup process, it is easy to cause water hammer, low condenser liquid level and other phenomena, and there are great safety hazards. The present invention provides a secondary circuit startup method for a nuclear reactor thermal-hydraulic system test, which solves the problem of difficulty in starting the secondary circuit during the high-temperature and high-pressure nuclear reactor thermal-hydraulic system test by coordinating the primary circuit with the secondary circuit and designing reasonable and orderly operation steps, so as to enable the secondary circuit of the system test to be started safely and effectively.

[0012] During the startup process, the temperature information of the primary circuit is obtained in real time, and the water flow of the secondary circuit to the water supply unit is adjusted according to the temperature information of the primary circuit; it works closely with the primary circuit and takes into account the parameter requirements of the secondary circuit equipment during operation, so that the nuclear reactor thermal-hydraulic system test can be started safely and stably, providing a data basis for the actual nuclear reactor transient thermal-hydraulic system.

[0013] A further optimization scheme is that the pretreatment process includes:

[0014] Isolate the steam unit and condenser from the secondary circuit, drain the liquid water in the steam unit and reduce the liquid level in the condenser to the initial threshold;

[0015] The steam unit is made to discharge steam, and after a time t, the steam unit stops discharging steam.

[0016] Before starting the water supply unit, the steam unit and the condenser are pre-treated to initialize the excess liquid water in the steam unit and the liquid level of the condenser to prevent affecting subsequent adjustment operations.

[0017] A further optimization scheme is that the initial threshold is half of the maximum value of the condenser liquid level.

[0018] A further optimization solution is to isolate the steam unit from the condenser and the steam unit from the water supply unit when starting the water supply unit of the secondary circuit.

[0019] A further optimization scheme is that step 4 includes the following sub-steps:

[0020] S41. When the temperature of the primary circuit meets the first temperature level, adjust the water supply unit, the steam unit and the primary circuit heating rate so that the water supply flow rate of the water supply unit reaches the minimum value required for the formal test;

[0021] S42, when the temperature of the primary circuit meets the second temperature level, adjusting the water supply unit so that the water supply flow rate of the water supply unit reaches the maximum value required for the formal test;

[0022] S43. When the temperature of the primary circuit meets the third temperature level, adjust the water supply unit, the steam unit and the heating rate of the primary circuit so that the water supply flow rate of the water supply unit reaches the reference flow rate.

[0023] A further optimized solution is that the steam unit includes a steam regulating valve and a steam generator; the water supply unit includes: a water supply tank, a water supply pump and a water supply regulating valve;

[0024] The steam regulating valve is installed between the steam generator and the condenser, the feed water regulating valve is installed between the steam generator and the feed water pump, the feed water pump is connected to the feed water tank, and the feed water tank and the condenser are connected through a stop valve.

[0025] A further optimization scheme is that the first temperature level is 160°C, the second temperature level is Tref-30°C, and the third temperature level is Tref-10°C; Tref is the temperature that a circuit needs to maintain during formal testing.

[0026] A further optimization scheme is that step S41 specifically includes:

[0027] When the average temperature of the primary circuit rises to 160°C, ensure that the feed water pump has been cranked and cooling water is supplied to the condenser;

[0028] Start the feedwater pump at 40% of its maximum frequency, adjust the steam control valve opening to 10%, and maintain the heating rate of the primary circuit at V2; adjust the feedwater control valve opening to increase the feedwater flow rate of the feedwater unit to the minimum value required for the formal test;

[0029] Increase the frequency of the water supply pump to 60% of the maximum frequency, while maintaining the heating rate of the primary circuit at V3, where V3 ≤ 60°C / h, and V1 < V2 < V3;

[0030] When the condenser pressure exceeds 20% P ref When the temperature is high, open the stop valve to connect the condenser and the water supply tank, and adjust the cooling water valve opening to allow cooling water to enter the condenser, keeping the condenser pressure at 20%P ref . Among them, P ref It refers to the reference pressure of the secondary circuit steam. The pressure point is located before the Venturi on the steam pipe.

[0031] A further optimization scheme is that step S42 specifically includes:

[0032] When the average temperature of the primary circuit rises to Tref-30℃, increase the frequency of the feedwater pump and reduce the opening of the feedwater regulating valve to keep the feedwater flow of the feedwater unit unchanged, and increase the pressure of the steam unit until the frequency of the feedwater pump rises to the maximum value required for the formal test;

[0033] A further optimization scheme is that step S43 specifically includes:

[0034] When the average temperature of the primary circuit rises to Tref-10℃, the frequency of the feedwater pump is maintained unchanged and the opening of the feedwater regulating valve is increased. The opening of the steam regulating valve is adjusted so that the feedwater flow rate of the feedwater unit reaches the reference flow rate and the steam pressure is close to P ref , while maintaining the heating rate of one circuit ≤60℃ / h.

[0035] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0036] The invention provides a method for starting a secondary circuit of a nuclear reactor thermal hydraulic system test. The method solves the problem of difficulty in starting the secondary circuit during a high-temperature and high-pressure nuclear reactor thermal hydraulic system test by coordinating a primary circuit with a secondary circuit and designing reasonable and orderly operation steps, and enables the secondary circuit of the system test to be started safely and effectively. During the starting process, the temperature information of the primary circuit is obtained in real time, and the water supply flow rate of the water supply unit of the secondary circuit is adjusted according to the temperature information of the primary circuit. The method closely cooperates with the primary circuit and takes into account the parameter requirements of the secondary circuit equipment during operation, so that the nuclear reactor thermal hydraulic system test can be started safely and stably, and provides a data basis for the actual nuclear reactor transient thermal hydraulic system. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0038] Figure 1 This is a schematic diagram of the secondary circuit structure of the nuclear reactor thermal hydraulic system test.

[0039] Marks and corresponding parts names in the attached drawings:

[0040] 1-feedwater pump, 2-feedwater regulating valve, 3-feedwater flowmeter, 4-steam generator, 5-steam flowmeter, 6-steam regulating valve, 7-condenser, 8-stop valve, 9-feedwater tank, 10-drain valve, 11-cooling water regulating valve, 12-feedwater pipe, 13-steam pipe. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0042] The key to the start-up of the nuclear reactor system test lies in the start-up of the secondary loop. The start-up of the secondary loop is closely coupled with the power change of the primary loop, and involves the process of the loop system changing from pure water to steam. Any carelessness during the operation may lead to dangerous physical phenomena such as water hammer and low condenser liquid level. The start-up process is complicated, and a scientific and reasonable start-up method is required to safely and effectively start the secondary loop of the nuclear reactor thermal hydraulic system experiment. In view of this, the present invention provides the following embodiments to solve the above technical problems.

[0043] Example 1

[0044] This embodiment provides a method for starting a secondary circuit of a nuclear reactor thermal hydraulic system test, wherein the secondary circuit comprises: a water supply unit, a steam unit and a condenser, wherein the water supply unit, the steam unit and the condenser are connected in sequence to form a circuit; the steam unit comprises a steam regulating valve and a steam generator; the water supply unit comprises: a water supply tank, a water supply pump and a water supply regulating valve;

[0045] The steam regulating valve is installed between the steam generator and the condenser, the feed water regulating valve is installed between the steam generator and the feed water pump, the feed water pump is connected to the feed water tank, and the feed water tank and the condenser are connected through a stop valve.

[0046] The secondary circuit starting method comprises the following steps:

[0047] Step 1: Raise the temperature and pressure of the primary circuit of the nuclear reactor thermal hydraulic system test, and obtain the temperature information of the primary circuit in real time;

[0048] Step 2: Pre-treat the steam unit and condenser of the secondary circuit;

[0049] Step 3: Start the water supply unit of the second circuit, while maintaining the heating rate of the first circuit at V1;

[0050] When the pressure of the condenser exceeds a threshold value, the condenser and the water supply unit are connected so that the cooling water in the water supply unit flows into the condenser; the pressure of the condenser is kept constant;

[0051] Step 4: According to the comparison result between the temperature status information of the first circuit and the reference temperature, the second circuit is adjusted so that the water supply flow rate of the water supply unit reaches the reference flow rate.

[0052] The pretreatment process includes:

[0053] Isolate the steam unit and condenser from the secondary circuit, drain the liquid water in the steam unit and reduce the liquid level in the condenser to the initial threshold;

[0054] The steam unit is made to discharge steam, and after a time t, the steam unit stops discharging steam.

[0055] The initial threshold is half of the maximum value of the condenser liquid level.

[0056] When starting the water supply unit of the secondary circuit, the steam unit is isolated from the condenser, and the steam unit is isolated from the water supply unit at the same time.

[0057] Step 4 includes the following sub-steps:

[0058] S41. When the temperature of the primary circuit meets the first temperature level, adjust the water supply unit, the steam unit and the primary circuit heating rate so that the water supply flow rate of the water supply unit reaches the minimum value required for the formal test;

[0059] When the average temperature of the primary circuit rises to 160°C, ensure that the feed water pump has been cranked and cooling water is supplied to the condenser;

[0060] Start the feedwater pump at 40% of its maximum frequency, adjust the steam regulating valve opening to 10%, and maintain the heating rate of the primary circuit at V2; adjust the feedwater regulating valve opening to increase the feedwater flow rate of the feedwater unit to the minimum value required for the formal test;

[0061] Increase the frequency of the water supply pump to 60% of the maximum frequency, while maintaining the heating rate of the primary circuit at V3, where V3 ≤ 60°C / h, and V1 < V2 < V3;

[0062] When the condenser pressure exceeds 20% P ref When the temperature is high, open the stop valve to connect the condenser and the water supply tank, and adjust the cooling water valve opening to allow cooling water to enter the condenser, keeping the condenser pressure at 20%P ref ; where P ref It refers to the reference pressure of the secondary circuit steam; the pressure point is located before the Venturi on the steam pipe.

[0063] S42, when the temperature of the primary circuit meets the second temperature level, adjusting the water supply unit so that the water supply flow rate of the water supply unit reaches the maximum value required for the formal test;

[0064] When the average temperature of the primary circuit rises to Tref-30℃, increase the frequency of the feedwater pump and reduce the opening of the feedwater regulating valve to keep the feedwater flow of the feedwater unit unchanged, and increase the pressure of the steam unit until the frequency of the feedwater pump rises to the maximum value required for the formal test;

[0065] S43. When the temperature of the primary circuit meets the third temperature level, adjust the water supply unit, the steam unit and the heating rate of the primary circuit so that the water supply flow rate of the water supply unit reaches the reference flow rate.

[0066] When the average temperature of the primary circuit rises to Tref-10℃, the frequency of the feedwater pump is maintained unchanged and the opening of the feedwater regulating valve is increased. The opening of the steam regulating valve is adjusted so that the feedwater flow rate of the feedwater unit reaches the reference flow rate and the steam pressure is close to P ref , while maintaining the heating rate of one circuit ≤60℃ / h.

[0067] The Tref is the temperature that a circuit needs to maintain during a formal test.

[0068] Example 2

[0069] like Figure 1 As shown, the secondary circuit of the thermal hydraulic system test includes a feedwater pump 1, a feedwater regulating valve 2, a feedwater flowmeter 3, a steam generator 4, a steam flowmeter 5, a steam regulating valve 6, a condenser 7, a stop valve 8, a cooling water regulating valve 9, a feedwater tank 9, a steam pipe 13, a drain pipe, and an exhaust pipe. It is necessary to arrange a temperature measuring point in the primary circuit of the test device to measure the average temperature of the primary circuit. The feedwater flowmeter 3 and the steam flowmeter 5 in the secondary circuit are used to measure the feedwater flow, steam flow, and steam temperature of the secondary circuit.

[0070] The specific startup steps of the secondary circuit of the test device are as follows:

[0071] a. During the process of increasing temperature and pressure in the first circuit, adjust the regulating valves in the water supply section and steam section of the second circuit system to appropriate openings. The opening of the regulating valve in the water supply section is 0, and the opening of the regulating valve in the steam section is set to any opening value between 40% and 80%.

[0072] b. Close the feed water regulating valve 2, close the stop valve 8, and keep the steam pipe 13 and the inlet and outlet of the condenser 7 separated from other devices in the secondary circuit; open the steam regulating valve 6 to keep the steam pipe 13 connected to the condenser 7; close the cooling water regulating valve 11 of the condenser; prevent the cooling water from entering the condenser 7 to form a negative pressure in the condenser.

[0073] c. Open the downstream exhaust valve of the steam pipe 13, open the two drain valves of the steam pipe 13, drain all the liquid water in the steam pipe 13, and close the two drain valves of the steam pipe 13; open the primary exhaust valve of the condenser 7, open the bottom drain valve 10 of the condenser 7, and close the drain valve 10 of the condenser when the liquid level of the condenser 7 drops to half of the maximum value. After many experiments, it was found that when the condenser liquid level drops to half of the maximum value, the condenser liquid level will remain in a reasonable range in the subsequent experiments. If the condenser liquid level is too high, it will cause water hammer phenomenon. If the condenser liquid level is too low, it will cause all the water in the condenser to be lost during the subsequent working condition change experiment and the experiment cannot be completed.

[0074] d. Keep the exhaust valve downstream of the steam pipe 13 and the exhaust valve on the primary side of the condenser 7 open; when steam comes out of the exhaust valve downstream of the steam pipe 13, close the exhaust valve; after a large amount of steam comes out of the exhaust valve on the primary side of the condenser 7 for 5 minutes, close the exhaust valve; at this time, the air above the liquid level of the condenser is discharged from the exhaust valve along with the steam, and there is no air above the condenser.

[0075] e. When the average temperature of the primary circuit rises to 160°C, ensure that the feedwater pump 1 has been cranked and there is cooling water to cool the feedwater pump, and supply power to the feedwater pump 1. Start the feedwater pump 1 at 40% of the maximum frequency of the feedwater pump, slowly adjust the opening of the steam regulating valve 6 to 10%, and at the same time increase the primary circuit heating power to maintain the primary circuit system heating rate V2. Slowly adjust the opening of the feedwater regulating valve 3 so that the feedwater flow rate of the water supply unit reaches the minimum value required for the formal test; the frequency of the feedwater pump 1 is increased to 60% of the maximum frequency, and at the same time increase the primary circuit heating power to control the primary circuit system heating rate to V3, V3 is less than or equal to 60°C / h; observe the pressure of the condenser 7, when the pressure of the condenser 7 exceeds the threshold value of 20%P ref , open the stop valve 8 to connect the condenser 7 with the water supply tank 9, and adjust the opening of the cooling water valve 11 to allow the cooling water to enter the condenser 7, and keep the pressure of the condenser 7 at 20%P ref About. ref Refers to the secondary circuit steam reference pressure. The pressure point is located before the Venturi on the steam pipe. If the condenser pressure is too low, the water in the water tank will be sucked back into the condenser; and if the condenser pressure is too high, the condenser liquid level will be too low.

[0076] f. When the average temperature of the primary circuit rises to (Tref-30)℃, slowly increase the frequency of the feedwater pump 1 while reducing the opening of the feedwater regulating valve 2 and appropriately adjust the opening of the steam regulating valve to keep the feedwater flow of the feedwater unit basically unchanged and increase the pressure of the steam unit slowly until the feedwater pump frequency rises to the maximum value required for this test. Tref is the temperature that the primary circuit needs to maintain during the formal test.

[0077] g. When the average temperature of the primary circuit rises to (Tref-10)℃, maintain the frequency of the feedwater pump 1 unchanged and slowly increase the opening of the feedwater regulating valve 3 and appropriately adjust the opening of the steam regulating valve 6, so that the feedwater flow rate of the feedwater unit reaches the required value for the test and the steam pressure is close to P ref . Adjust the opening of the water supply regulating valve 3 to control the heating rate of the primary circuit system to no more than 60℃ / h. If the heating rate is too fast, it will cause leakage in the primary circuit.

[0078] h. Adjust the secondary circuit flow to the required working conditions, and manually adjust the primary circuit power to match the secondary circuit flow changes.

[0079] The present invention is a novel two-loop start-up method for a reactor thermal-hydraulic system test device, which is developed based on the need for starting a reactor thermal-hydraulic system test loop. The two-loop start-up method can ensure that the reactor thermal-hydraulic system test can be started safely and stably. The two-loop includes a steam generator, a steam regulating valve, a condenser, a feed water tank, a feed water pump, a steam pipeline drain pipe and an exhaust pipe, etc. Through close cooperation with the first loop, the second loop is started in steps, which effectively protects various equipment, avoids the occurrence of water hammer and low condenser liquid level, and ensures the smooth generation of steam.

[0080] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for starting up a secondary circuit of a nuclear reactor thermal hydraulic system test, the secondary circuit comprising: A water supply unit, a steam unit and a condenser, wherein the water supply unit, the steam unit and the condenser are connected in sequence to form a loop; characterized in that the steps include: Step 1: Raise the temperature and pressure of the primary circuit of the nuclear reactor thermal hydraulic system test, and obtain the temperature information of the primary circuit in real time; Step 2: Pre-treating the steam unit and condenser of the secondary circuit; the pre-treating process includes: Isolate the steam unit and condenser from the secondary circuit, drain the liquid water in the steam unit and reduce the liquid level in the condenser to the initial threshold; The steam unit is ordered to discharge steam, and after a time t, the steam unit stops discharging steam; Step 3: Start the water supply unit of the second circuit, while maintaining the heating rate of the first circuit at V1; When the pressure of the condenser exceeds a threshold value, the condenser and the water supply unit are connected so that the cooling water in the water supply unit flows into the condenser; the pressure of the condenser is kept constant; Step 4: According to the comparison result between the temperature status information of the first circuit and the reference temperature, the second circuit is adjusted so that the water supply flow rate of the water supply unit reaches the reference flow rate; this step includes the following sub-steps: S41. When the temperature of the primary circuit meets the first temperature level, adjust the water supply unit, the steam unit and the primary circuit heating rate so that the water supply flow rate of the water supply unit reaches the minimum value required for the formal test; S42, when the temperature of the primary circuit meets the second temperature level, adjusting the water supply unit so that the water supply flow rate of the water supply unit reaches the maximum value required for the formal test; S43. When the temperature of the primary circuit meets the third temperature level, adjust the water supply unit, the steam unit and the heating rate of the primary circuit so that the water supply flow rate of the water supply unit reaches the reference flow rate.

2. A method for starting up a secondary circuit of a nuclear reactor thermal hydraulic system test according to claim 1, characterized in that: The initial threshold is half of the maximum value of the condenser liquid level.

3. A method for starting up a secondary circuit of a nuclear reactor thermal hydraulic system test according to claim 1, characterized in that: When starting the water supply unit of the secondary circuit, the steam unit is isolated from the condenser, and the steam unit is isolated from the water supply unit at the same time.

4. A method for starting up a secondary circuit of a nuclear reactor thermal hydraulic system test according to claim 1, characterized in that: The steam unit includes a steam regulating valve and a steam generator; the water supply unit includes a water supply tank, a water supply pump and a water supply regulating valve; The steam regulating valve is installed between the steam generator and the condenser, the feed water regulating valve is installed between the steam generator and the feed water pump, the feed water pump is connected to the feed water tank, and the feed water tank and the condenser are connected through a stop valve.

5. A method for starting up a secondary circuit of a nuclear reactor thermal hydraulic system test according to claim 4, characterized in that: The first temperature level is 160°C, the second temperature level is Tref-30°C, and the third temperature level is Tref-10°C; Tref is the temperature that a circuit needs to maintain during formal testing.

6. A method for starting up a secondary circuit of a nuclear reactor thermal hydraulic system test according to claim 5, characterized in that: Step S41 specifically includes: When the average temperature of the primary circuit rises to 160°C, ensure that the feed water pump has been cranked and cooling water is supplied to the condenser; Start the feedwater pump at 40% of its maximum frequency, adjust the steam regulating valve opening to 10%, and maintain the heating rate of the primary circuit at V2; adjust the feedwater regulating valve opening to increase the feedwater flow rate of the feedwater unit to the minimum value required for the formal test; Increase the frequency of the water supply pump to 60% of the maximum frequency, while maintaining the heating rate of the primary circuit at V3, where V3 ≤ 60℃ / h, and V1<V2<V3; When the condenser pressure exceeds 20%P ref When the temperature is high, open the stop valve to connect the condenser and the water supply tank, and adjust the cooling water valve opening to allow cooling water to enter the condenser, keeping the condenser pressure at 20%P ref , where P ref It refers to the reference pressure of the secondary circuit steam. The pressure point is located before the Venturi on the steam pipe.

7. A method for starting up a secondary circuit of a nuclear reactor thermal hydraulic system test according to claim 6, characterized in that: Step S42 specifically includes: When the average temperature of a circuit rises to Tref-30℃, increase the frequency of the feedwater pump and reduce the opening of the feedwater regulating valve to keep the feedwater flow of the feedwater unit unchanged, and increase the pressure of the steam unit until the frequency of the feedwater pump reaches the maximum value required for the formal test.

8. A method for starting up a secondary circuit of a nuclear reactor thermal hydraulic system test according to claim 7, characterized in that: Step S43 specifically includes: When the average temperature of the primary circuit rises to Tref-10℃, the frequency of the feedwater pump is maintained unchanged and the opening of the feedwater regulating valve is increased. The opening of the steam regulating valve is adjusted so that the feedwater flow rate of the feedwater unit reaches the reference flow rate and the steam pressure is close to P ref , while maintaining the heating rate of one circuit ≤60℃ / h.

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