A method for testing the airtightness of a nuclear power plant generator set without a cold source

Abstract

The present application relates to a kind of nuclear power plant generator unit without cold source air tightness test method, applied to the working condition of the pump outage of circulating water system, comprising: starting generator seal oil system carries out air tightness test, the heat generated by generator seal oil system, conventional island closed cooling water system operation is transferred to circulating water system;The cooling water of conventional island closed cooling water system is replaced by the desalted water distribution system of conventional island, and / or the heat exchange of using drinking water system is used to cool auxiliary cooling water system, to take away the heat of conventional island closed cooling water system, the sealing oil of generator seal oil system is maintained at first set temperature.The present application has the following beneficial effects: air tightness test can be carried out without the pump of circulating water system as cold source, provides diversity for generator air tightness test window, avoids affecting overhaul key path;Without changing the original generator air tightness test mode, also without modifying field equipment, with very high adaptability.

Description

Technical Field

[0001] This application relates to the field of nuclear power plant control, and in particular to a method for testing the airtightness of a nuclear power plant generator unit without a cooling source. Background Technology

[0002] Nuclear power plant turbine generators generally employ the currently mainstream water-hydrogen cooling method, namely water cooling of the stator windings and hydrogen cooling of the stator core and rotor windings. Since hydrogen is a flammable and explosive gas, in addition to sealing the hydrogen inside the generator, it is also essential to verify the generator's pressure-holding capacity. Otherwise, a large-scale hydrogen leak inside the generator will, on the one hand, worsen the generator's cooling effect, cause internal components to expand due to heat, and uneven expansion will lead to increased unit vibration; on the other hand, air may leak into the generator, reaching the hydrogen explosion limit and causing a serious operational accident. Therefore, after the generator is disassembled and overhauled, test gas must be injected into the generator to check the oil lines of the generator's sealing oil system and the sealing condition of the generator's sealing devices.

[0003] In existing airtightness tests, the sealing oil of the generator sealing oil system needs to be maintained at a set temperature. Therefore, the heat generated needs to be carried away by the cooling water of the conventional island closed-loop cooling water system, and then the cooling water of the conventional island closed-loop cooling water system is cooled by the auxiliary cooling water system.

[0004] However, during nuclear power plant overhauls, the pumps in the circulating water system often cannot be restored or started as planned due to maintenance work. This prevents the auxiliary cooling water system from removing the heat from the conventional island closed-loop cooling water system, causing the cooling water temperature to rise continuously. Consequently, the sealing oil in the generator sealing oil system cannot be maintained at the set temperature, making it impossible to conduct the generator airtightness test. The success of the generator airtightness test marks the smooth completion of the generator maintenance work during the nuclear power plant overhaul. Summary of the Invention

[0005] To address the problem in existing technologies that the circulating water system pumps in nuclear power plants often cannot be restored or started as planned during overhauls, thus preventing the conduct of generator airtightness tests, this invention provides a method for conducting airtightness tests on nuclear power plant generator sets without a cold source.

[0006] This invention provides a method for airtightness testing of nuclear power plant generator units without a cooling source, applicable to the condition of pump shutdown in the circulating water system. The method includes:

[0007] The generator sealing oil system is started for an airtightness test, wherein the heat generated by the operation of the generator sealing oil system and the conventional island closed-loop cooling water system is transferred to the circulating water system;

[0008] The cooling water of the conventional island closed-loop cooling water system is replaced by the conventional island demineralized water distribution system, and / or the auxiliary cooling water system is cooled by heat exchange using the drinking water system, so as to remove the heat from the conventional island closed-loop cooling water system and maintain the sealing oil of the generator sealing oil system at a first set temperature.

[0009] Preferably, the step of replacing the cooling water in the conventional island closed-loop cooling water system through the conventional island demineralized water distribution system includes:

[0010] Open the outlet vent valve of the pump in the conventional island closed-loop cooling water system and the vent valve on the cooling water side of the heat exchanger in the conventional island closed-loop cooling water system to discharge the cooling water;

[0011] The conventional island demineralized water distribution system replenishes water by opening the headbox bypass water supply valve of the conventional island closed-loop cooling water system.

[0012] Preferably, the step of using the drinking water system for heat exchange to cool the auxiliary cooling water system includes:

[0013] The drinking water is injected into the seawater side of the tubular cooler in the auxiliary cooling water system, and the drinking water is discharged through the exhaust pipe upstream of the seawater side after flowing through the seawater side.

[0014] Preferably, the method for testing the airtightness of a nuclear power plant generator unit without a cooling source further includes:

[0015] The calculation shows that maintaining the sealing oil of the generator sealing oil system at a first set temperature results in the heat Q generated by the conventional island closed-loop cooling water system. 总 ;

[0016] Calculate the heat Q removed by the conventional island demineralized water distribution system during the water exchange of the conventional island closed-loop cooling water system. 排 ;

[0017] Calculate the amount of heat Q removed by the drinking water system for cooling the auxiliary cooling water system. 换 ;

[0018] According to Q 总 Q 排 and Q 换 Calculate the water exchange volume X and the flow rate Y, where the water exchange volume X is the flow rate of the cooling water in the conventional island closed-loop cooling water system that is exchanged through the conventional island demineralized water distribution system, and the flow rate Y is the flow rate of the drinking water in the drinking water system when the drinking water system is used for heat exchange to cool the auxiliary cooling water system.

[0019] An airtightness test was conducted based on the water exchange volume X and the flow rate Y.

[0020] Preferably, the Q 总 This includes the heat generated by the hydrogen-side motor of the generator sealing oil system, the heat generated by the air-side motor of the generator sealing oil system, and the heat generated by the motor of the conventional island closed-loop cooling water system.

[0021] Preferably, the Q 排 The formula for calculating Q is: 排 =c 水 *X*(T1-T2);

[0022] Among them, c 水 T1 is the specific heat capacity of water, T2 is the set discharge temperature of the cooling water, and T3 is the temperature of the makeup water for the conventional island demineralized water distribution system.

[0023] Preferably, the Q 换 The formula for calculating Q is: 换 =c 水 *Y*(T3-T4);

[0024] Wherein, T3 is the temperature at which the drinking water is discharged, and T4 is the initial temperature of the drinking water in the drinking water system.

[0025] Preferably, when the system temperature of the conventional island closed-loop cooling water system is greater than the warning temperature, the generator depressurization is determined based on the temperature rise of the system and the oil temperature of the sealing oil.

[0026] Preferably, if the system temperature is greater than or equal to the second set temperature, the airtightness test is stopped and the generator depressurization step is performed.

[0027] Preferably, if the temperature of the sealing oil is greater than or equal to the third set temperature, the airtightness test ends and the generator depressurization step is performed.

[0028] The technical solution of this invention involves replacing the cooling water in the conventional island closed-loop cooling water system through a conventional island demineralized water distribution system, and / or using a drinking water system for heat exchange to cool the auxiliary cooling water system, thereby removing heat from the conventional island closed-loop cooling water system and maintaining the sealing oil of the generator sealing oil system at a first set temperature. The technical solution of this invention has the following beneficial effects:

[0029] 1. It can perform airtightness tests without a circulating water system or a pump as a cold source, providing diversity for generator airtightness test windows and avoiding impact on critical overhaul paths;

[0030] 2. It does not require changing the original generator airtightness test method or modifying the on-site equipment, and has extremely high adaptability. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a circuit diagram of the sealing oil system cooling method for the airtightness test method of nuclear power plant generator set without cold source provided by the present invention;

[0033] Figure 2 This is a flowchart of an embodiment of the airtightness test method for nuclear power plant generator sets without a cooling source provided by the present invention;

[0034] Figure 3 This is a flowchart of another embodiment of the airtightness test method for nuclear power plant generator sets without a cooling source provided by the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Reference Figure 1 and Figure 2 , Figure 1 This is a circuit diagram of the sealing oil system cooling of the nuclear power plant generator unit airtightness test method without cold source provided by the present invention. In the diagram, CRF represents the circulating water system, SER represents the conventional island demineralized water distribution system, SRI represents the conventional island closed-loop cooling water system, SEN represents the auxiliary cooling system, SEP represents the drinking water system, and GHE represents the generator sealing oil system. Figure 2 This is a flowchart of an embodiment of the airtightness test method for nuclear power plant generator sets without a cooling source provided by the present invention. This embodiment of the airtightness test method for nuclear power plant generator sets without a cooling source is applied under the condition that the pumps of the circulating water system are shut down. The method includes:

[0037] The generator sealing oil system was started for an airtightness test, during which the heat generated by the generator sealing oil system and the conventional island closed-loop cooling water system was transferred to the circulating water system.

[0038] The cooling water of the conventional island closed-loop cooling water system is replaced by the conventional island demineralized water distribution system, and / or the auxiliary cooling water system is cooled by heat exchange using the drinking water system, so as to remove the heat from the conventional island closed-loop cooling water system and maintain the sealing oil of the generator sealing oil system at the first set temperature.

[0039] It should be noted that the standard oil temperature for the sealing oil in the generator sealing oil system is 44°C to 50°C. Those skilled in the art can set the first set temperature between 44°C and 50°C according to actual needs.

[0040] Preferably, the first set temperature can be set to 46°C.

[0041] It should be noted that the conventional island closed-loop cooling water system is a closed-loop circulation system. Under normal circumstances, the system does not require water replenishment. When a leak occurs, the conventional island demineralized water distribution system will automatically replenish water through a valve to ensure sufficient water volume in the entire system, thereby ensuring the reliable operation of the pumps in the conventional island closed-loop cooling water system. During the airtightness test without a cooling source, the temperature of the entire conventional island closed-loop cooling water system will continue to rise due to continuous system heating and the lack of cooling. By draining the high-temperature cooling water from the conventional island closed-loop cooling water system and replenishing it with lower-temperature water from the conventional island demineralized water distribution system, the heat can be removed, thereby lowering the temperature of the conventional island closed-loop cooling water system.

[0042] It should be noted that during normal airtightness testing, the pumps in the circulating water system drive seawater through the auxiliary cooling water system to cool the conventional island's closed-loop cooling water system. However, during airtightness testing without a cooling source, since the pumps in the circulating water system cannot operate, drinking water from the drinking water system can be used instead of seawater to flow into the auxiliary cooling water system to cool the conventional island's closed-loop cooling water system.

[0043] The method for conducting a cold-source-free airtightness test of a nuclear power plant generator unit provided in this embodiment involves replacing the cooling water in the conventional island closed-loop cooling water system through the conventional island demineralized water distribution system, and / or using a drinking water system for heat exchange to cool the auxiliary cooling water system. This removes heat from the conventional island closed-loop cooling water system and maintains the sealing oil in the generator sealing oil system at a first set temperature. The technical solution of this invention has the following beneficial effects:

[0044] 1. It can perform airtightness tests without a circulating water system or a pump as a cold source, providing diversity for generator airtightness test windows and avoiding impact on critical overhaul paths;

[0045] 2. It does not require changing the original generator airtightness test method or modifying the on-site equipment, and has extremely high adaptability.

[0046] In some embodiments of the present invention, the step of replacing the cooling water of the conventional island closed-loop cooling water system through the conventional island demineralized water distribution system includes:

[0047] Open the outlet vent valve of the pump in the conventional island closed-loop cooling water system and the vent valve on the cooling water side of the heat exchanger in the conventional island closed-loop cooling water system to discharge the cooling water.

[0048] The conventional island demineralized water distribution system replenishes water by opening the headbox bypass water supply valve of the conventional island closed-loop cooling water system.

[0049] It should be noted that the largest heat source of the conventional island closed-loop cooling water system is the pump of the conventional island closed-loop cooling water system, and the pump is located upstream of the heat exchanger of the conventional island closed-loop cooling water system. Therefore, the temperature near the pump is the highest. Opening the outlet exhaust valve of the pump of the conventional island closed-loop cooling water system and the exhaust valve on the cooling water side of the heat exchanger of the conventional island closed-loop cooling water system to discharge the cooling water is beneficial to the discharge of high-temperature cooling water and thus enhances the cooling efficiency.

[0050] It should be noted that, since the water supply rate from the demineralized water distribution system of the conventional island to the closed-loop cooling water system of the conventional island must be less than or equal to 20 cubic meters per hour, the discharge rate of the closed-loop cooling water system of the conventional island must also be adjusted to match the water supply rate. Therefore, the water exchange rate of the cooling water in the closed-loop cooling water system of the conventional island must also be less than or equal to 20 cubic meters per hour.

[0051] In some embodiments of the present invention, the step of using a drinking water system for heat exchange to cool an auxiliary cooling water system includes:

[0052] Drinking water is injected into the seawater side of the tubular cooler in the auxiliary cooling water system. After flowing through the seawater side, the drinking water is discharged through the exhaust pipe upstream of the seawater side.

[0053] It should be noted that during normal airtightness testing, the pumps in the circulating water system drive seawater through the seawater side of the tubular cooler in the auxiliary cooling water system, while the pumps in the conventional island closed-loop cooling water system drive cooling water through the cooling water side of the tubular cooler in the auxiliary cooling water system. The tubular cooler transfers heat from the conventional island closed-loop cooling water system side to the seawater side, thus cooling the conventional island closed-loop cooling water system. However, during airtightness testing without a cooling source, since the pumps in the circulating water system cannot operate, drinking water can be injected into the seawater side of the tubular cooler in the auxiliary cooling water system. The drinking water then flows through the seawater side and is discharged through the exhaust pipe upstream of the seawater side, thus cooling the cooling water side of the auxiliary cooling water system and consequently the conventional island closed-loop cooling water system.

[0054] Reference Figure 3 , Figure 3This is a flowchart of another embodiment of the cold-source-free airtightness test method for nuclear power plant generator sets provided by the present invention. This embodiment of the cold-source-free airtightness test method for nuclear power plant generator sets further includes:

[0055] Calculate the heat Q generated by the conventional island closed-loop cooling water system to maintain the sealing oil of the generator sealing oil system at the first set temperature. 总 ;

[0056] Calculate the heat Q removed by exchanging the cooling water in the conventional island closed-loop cooling water system through the conventional island demineralized water distribution system. 排 ;

[0057] Calculate the heat Qexchange carried away by the auxiliary cooling water system when using the drinking water system for heat exchange to cool it.

[0058] According to Q 总 Q 排 and Q 换 Calculate the water exchange volume X and the flow rate Y. The water exchange volume X is the flow rate of the cooling water in the closed-loop cooling water system of the conventional island through the conventional island demineralized water distribution system. The flow rate Y is the flow rate of the drinking water in the drinking water system when the drinking water system is used for heat exchange to cool the auxiliary cooling water system.

[0059] It is conceivable that, based on Q within the same time period 总 ≦Q 排 +Q 换 The formula can be used to calculate the relationship between water exchange volume X and flow rate Y, and then the specific values ​​of water exchange volume X and flow rate Y can be determined according to the actual situation.

[0060] An airtightness test was conducted based on the water exchange volume X and flow rate Y.

[0061] It is conceivable that, given the specific values ​​of water exchange volume X and flow rate Y, the flow rate of cooling water discharged from the conventional island closed-loop cooling water system and the makeup water volume of the conventional island demineralized water distribution system can be set according to the water exchange volume X, and the flow rate of drinking water in the drinking water system when using the drinking water system for heat exchange to cool the auxiliary cooling water system can be set according to the flow rate Y, and an airtightness test can be conducted.

[0062] In some embodiments of the present invention, Q 总 This includes the heat generated by the hydrogen-side motor of the generator sealing oil system, the heat generated by the air-side motor of the generator sealing oil system, and the heat generated by the motor of the conventional island closed-loop cooling water system.

[0063] It should be noted that during the airtightness test without a cooling source, at least one hydrogen-side motor and one air-side motor of the generator sealing oil system are required to operate. The kinetic energy of the motors is converted into heat energy of the oil. To maintain the sealing oil temperature at the first set temperature, the conventional island closed-loop cooling water system needs to operate to cool the generator sealing oil system. Therefore, at least one pump of the conventional island closed-loop cooling water system needs to operate to ensure the circulation of the entire conventional island closed-loop cooling water system. The kinetic energy of the motors in the conventional island closed-loop cooling water system will be converted into heat energy of the cooling water in the conventional island closed-loop cooling water system. This heat energy causes the cooling water temperature of the conventional island closed-loop cooling water system to rise. Therefore, Q 总 This includes the heat generated by the hydrogen-side motor of the generator sealing oil system, the heat generated by the air-side motor of the generator sealing oil system, and the heat generated by the motor of the conventional island closed-loop cooling water system.

[0064] It should be noted that the hydrogen-side motor power of the generator sealing oil system is 37KW, the air-side motor power is 7.5KW, and the motor power of the conventional island closed-loop cooling water system is 280KW. Assuming that the kinetic energy of all three motors is converted into the cooling water heat energy of the conventional island closed-loop cooling water system, the total heat generated per hour is:

[0065] Q 总 =(37+7.5+280)*3600=1168200(KJ).

[0066] In some embodiments of the present invention, Q 排 The formula for calculating Q is: 排 =c 水 *X*(T1-T2);

[0067] Among them, c 水 T1 is the specific heat capacity of water, T2 is the set discharge temperature of cooling water, and T3 is the temperature of the makeup water for the conventional island demineralized water distribution system.

[0068] It should be noted that the standard oil temperature for the generator sealing oil system is 44℃ to 50℃, and the set discharge temperature T1 for the cooling water in the conventional island closed-loop cooling water system can be set to 40℃; the temperature of the conventional island demineralized water distribution system is between 29℃ and 30℃, and the make-up water temperature T2 for the conventional island demineralized water distribution system is conservatively taken as 30℃. When the water exchange rate is X, the heat removed per hour is:

[0069] Q 排 =4.2*1000*X*1000*(40-30)=42000X(KJ).

[0070] In some embodiments of the present invention, Q 换 The formula for calculating Q is: 换 =c水 *Y*(T3-T4);

[0071] Where T3 is the temperature when the drinking water is discharged, and T4 is the initial temperature of the drinking water in the drinking water system.

[0072] It should be noted that the system temperature of the drinking water system is between 29℃ and 30℃, and the initial temperature T4 of the drinking water in the system is conservatively taken as 30℃. The temperature rise of the drinking water is estimated to be 5℃, therefore the temperature T3 when the drinking water is discharged is 35℃. The heat removed per hour when the drinking water flow rate is Y is:

[0073] Q 换 =4.2*1000*Y*1000*(35-30)=21000Y(KJ).

[0074] In some embodiments of the present invention, when the system temperature of the conventional island closed-loop cooling water system is greater than the warning temperature, the generator depressurization is determined based on the temperature rise of the system and the oil temperature of the sealing oil.

[0075] It should be noted that the design temperature requirement for the conventional island closed-loop cooling water system is no greater than 60℃, and the standard oil temperature for the generator sealing oil system is 44℃ to 50℃. However, in practical testing, it was found that when the temperature of the conventional island closed-loop cooling water system exceeds 40℃, the rate of temperature rise significantly accelerates. Therefore, a warning temperature can be set at 40℃. When the system temperature of the conventional island closed-loop cooling water system exceeds the warning temperature, the generator depressurization should be initiated based on the system temperature rise and the oil temperature of the sealing oil to stop or end the airtightness test, thus ensuring equipment safety.

[0076] In some embodiments of the present invention, if the system temperature is greater than or equal to the second set temperature, the airtightness test is stopped and the generator depressurization step is performed.

[0077] It is conceivable that the second set temperature should be set between the warning temperature and the first set temperature to ensure that the sealing oil of the generator sealing oil system is always cooled by the conventional island closed-loop cooling water system during the airtightness test.

[0078] Preferably, the second set temperature can be set to 43°C.

[0079] In some embodiments of the present invention, if the temperature of the sealing oil is greater than or equal to a third set temperature, the airtightness test is terminated and the generator depressurization step is performed.

[0080] It is conceivable that the third set temperature should be set between the first set temperature and 50°C to prevent the oil temperature of the generator sealing oil system from exceeding the standard.

[0081] Preferably, the third set temperature can be set to 50°C.

[0082] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that all or part of the processes for implementing the above embodiments, and equivalent variations made in accordance with the claims of the present invention, still fall within the scope of the invention.

Claims

1. A method for airtightness testing of a nuclear power plant generator unit without a cooling source, applied under the condition of pump shutdown in a circulating water system, characterized in that, The method includes: The generator sealing oil system is started for an airtightness test, wherein the heat generated by the operation of the generator sealing oil system and the conventional island closed-loop cooling water system is transferred to the circulating water system; The cooling water of the conventional island closed-loop cooling water system is replaced by the conventional island demineralized water distribution system, and the auxiliary cooling water system is cooled by using the drinking water system for heat exchange, so as to remove the heat of the conventional island closed-loop cooling water system and maintain the sealing oil of the generator sealing oil system at a first set temperature. Also includes: The calculation shows that maintaining the sealing oil of the generator sealing oil system at a first set temperature results in the heat Q generated by the conventional island closed-loop cooling water system. 总 ; Calculate the heat Q removed by the conventional island demineralized water distribution system during the water exchange of the conventional island closed-loop cooling water system. 排 ; Calculate the amount of heat Q removed by the drinking water system for cooling the auxiliary cooling water system. 换 ; According to Q 总 Q 排 and Q 换 Calculate the water exchange volume X and the flow rate Y, where the water exchange volume X is the flow rate of the cooling water in the conventional island closed-loop cooling water system that is exchanged through the conventional island demineralized water distribution system, and the flow rate Y is the flow rate of the drinking water in the drinking water system when the drinking water system is used for heat exchange to cool the auxiliary cooling water system. An airtightness test was conducted based on the water exchange volume X and the flow rate Y.

2. The method for testing the airtightness of a nuclear power plant generator unit without a cooling source according to claim 1, characterized in that, The step of replacing the cooling water in the conventional island closed-loop cooling water system through the conventional island demineralized water distribution system includes: Open the outlet vent valve of the pump in the conventional island closed-loop cooling water system and the vent valve on the cooling water side of the heat exchanger in the conventional island closed-loop cooling water system to discharge the cooling water; The conventional island demineralized water distribution system replenishes water by opening the headbox bypass water supply valve of the conventional island closed-loop cooling water system.

3. The method for airtightness test of nuclear power plant generator units without cooling source according to claim 1, characterized in that, The step of using a drinking water system for heat exchange to cool the auxiliary cooling water system includes: The drinking water is injected into the seawater side of the tubular cooler in the auxiliary cooling water system, and the drinking water is discharged through the exhaust pipe upstream of the seawater side after flowing through the seawater side.

4. The method for airtightness test of nuclear power plant generator units without cooling source according to claim 1, characterized in that, The Q 总 This includes the heat generated by the hydrogen-side motor of the generator sealing oil system, the heat generated by the air-side motor of the generator sealing oil system, and the heat generated by the motor of the conventional island closed-loop cooling water system.

5. The method for airtightness test of nuclear power plant generator units without cooling source according to claim 4, characterized in that, The Q 排 The formula for calculating Q is: 排 =c 水 X (T1-T2); Among them, c 水 T1 is the specific heat capacity of water, T2 is the set discharge temperature of the cooling water, and T3 is the temperature of the makeup water for the conventional island demineralized water distribution system.

6. The method for airtightness test of nuclear power plant generator units without cooling source according to claim 5, characterized in that, The Q 换 The formula for calculating Q is: 换 =c 水 Y (T3-T4); Wherein, T3 is the temperature at which the drinking water is discharged, and T4 is the initial temperature of the drinking water in the drinking water system.

7. The method for testing the airtightness of a nuclear power plant generator unit without a cooling source according to claim 1, characterized in that, When the system temperature of the conventional island closed-loop cooling water system exceeds the warning temperature, the generator depressurization is initiated based on the temperature rise of the system and the oil temperature of the sealing oil.

8. The method for testing the airtightness of a nuclear power plant generator unit without a cooling source according to claim 7, characterized in that, If the system temperature is greater than or equal to the second set temperature, stop the airtightness test and proceed with the generator depressurization step.

9. The method for testing the airtightness of a nuclear power plant generator unit without a cooling source according to claim 7, characterized in that, If the temperature of the sealing oil is greater than or equal to the third set temperature, the airtightness test ends, and the generator depressurization step is performed.

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