Method for adjusting running state of one circulating water pump unit when VVER unit stops running

Abstract

The invention belongs to the field of nuclear power operation, and particularly relates to a method for adjusting the operation state of a VVER unit stopping one circulating water pump unit, which comprises the following steps: step 1, before stopping the circulating water pump, stably reducing the power to preset power; step 2, putting into a condensed water fine treatment system; 3, starting a standby vacuum pump; 4, water is supplemented to the condenser to the high position; 5, when the power is stably reduced to be below the preset power, the circulating water pump is stopped; 6, one circulating water pump is locked and stopped; and 7, the unit power is slowly increased, and unit operation state adjustment is completed. According to the method, the fault circulating water pump can be safely shut down to enter a maintenance state, and unfavorable conditions such as shutdown of a trigger reactor and shutdown of a steam turbine generator are prevented.

Description

Technical Field

[0001] The invention belongs to the field of nuclear power operation, and in particular relates to a method for adjusting the operating state of a circulating water pump unit when a VVER unit is shut down. Background Art

[0002] When the VVER1000 nuclear power plant is operating normally, four circulating cooling water pumps cool the condenser to form a vacuum. If it is discovered in advance that one of the circulating cooling water pumps fails and cannot operate for a long time, effective methods are needed to prevent the vacuum change caused by the shutdown of one circulating cooling water pump. The corresponding protection is triggered, and the turbine power is shed from 1060MW to 800MW. The main steam header pressure before entering the turbine will fluctuate. When this pressure is too low, it will trigger the reactor shutdown and the turbine generator shutdown.

[0003] Therefore, a relatively stable and controllable method is needed to adjust the operating status of the unit to prevent the occurrence of adverse situations such as triggering reactor shutdown and steam turbine generator shutdown. Summary of the invention

[0004] The purpose of the present invention is to provide a method for adjusting the operating status of a circulating water pump unit when a VVER unit is shut down. The method can safely shut down the faulty circulating water pump and put it into a maintenance state to prevent the occurrence of adverse situations such as triggering reactor shutdown and steam turbine generator shutdown.

[0005] The technical solution to achieve the purpose of the present invention is:

[0006] A method for adjusting the operating state of a circulating water pump unit when a VVER unit is shut down, the method comprising:

[0007] Step 1: Before the circulating water pump stops operating, steadily reduce the power to the preset power;

[0008] Step 2: Put the condensate polishing system into operation;

[0009] Step 3: Start the standby vacuum pump;

[0010] Step 4: Fill the condenser with water to a high level;

[0011] Step 5: When the power is stably reduced to below the preset power, the circulating water pump is stopped;

[0012] Step 6: Lock and stop one circulating water pump;

[0013] Step 7: Slowly increase the unit power to complete the unit operating status adjustment.

[0014] The preset power in step 1 and step 5 is below 780MW.

[0015] The step 2 comprises:

[0016] Step 2.1: Put into operation a condensate polishing system;

[0017] Step 2.2: When water quality deteriorates, put the backup condensate polishing system into use.

[0018] In the step 2.1, a condensate polishing system is introduced into the circulating cooling water pipeline of the condenser to purify the quality of the condensate.

[0019] In step 2.2, a standby condensate polishing system is put into use according to the water quality of the secondary circuit condensate, feed water and wastewater from the steam generator.

[0020] In step 4, water is added to the condenser to a high level by manually opening a valve.

[0021] In step 6, the protection logic of shutting down a circulating water pump to shed load to 800MW is locked.

[0022] In step 7, the unit power is slowly increased to meet the value of the unit power and vacuum curve.

[0023] The beneficial technical effects of the present invention are:

[0024] 1. The present invention provides a method for adjusting the operating status of a VVER unit when a circulating water pump unit is shut down. The method slowly reduces the power to a power value below the load shedding protection condition to avoid large fluctuations in system operation caused by protection triggering. In addition, based on the past phenomenon of shutting down a circulating water pump, actions to prevent related consequences are taken in advance. Condenser-related parameters are mutually verified in multiple ways to avoid inaccurate instruments that may lead to incorrect actions.

[0025] 2. The present invention provides a method for adjusting the operating status of a VVER unit when a circulating water pump unit is shut down. The method can effectively reduce the significant change in the output power of the steam turbine generator when the circulating cooling water pump is shut down, avoid the shutdown of the steam turbine generator and the reactor, effectively reduce the power loss of the steam turbine generator, ensure the stable output of the nuclear power plant's power, and achieve the goals of carbon neutrality and carbon peak as soon as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention provides a flow chart of a method for adjusting the operating state of a circulating water pump unit when a VVER unit is shut down. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0028] like Figure 1 As shown, the present invention provides a method for adjusting the operating state of a VVER unit by shutting down a circulating water pump unit, which specifically includes the following steps:

[0029] Step 1: Before the circulating water pump is shut down, stabilize the power reduction to below 780MW

[0030] When the power is greater than 820MW, stopping a circulating water pump will trigger the load shedding to 800MW protection. This protection is allowed to be locked only when the vacuum is greater than -98KPa. In addition, this protection lock requires the instrumentation and control personnel to go through the declaration process, which takes a long time and brings great hidden dangers to the unit. Therefore, the reactor needs to be switched to the power reduction mode first, and the power should be steadily reduced to below 780MW to avoid the triggering of this protection.

[0031] Step 2: Put the condensate polishing system into operation

[0032] Step 2.1: Commissioning a condensate polishing system

[0033] After the circulating water pump stops operating, the exhaust temperature rises, causing the expansion of the circulating cooling water pipe of the condenser to loosen, or the titanium tube plug falls off or the titanium tube is damaged, which deteriorates the condensate quality. According to experience, after the circulating water pump is stopped, the micro-leakage of the condenser will become larger, and seawater will enter the condensate, causing the water quality to deteriorate. According to the unit operation requirements, the power needs to be reduced. Therefore, while reducing the power, a condensate polishing system is put into use for large-flow purification.

[0034] Step 2.2: Use the backup condensate polishing system when water quality deteriorates

[0035] Pay attention to the water quality of secondary circuit condensate, feed water and steam generator wastewater, and put into use a spare condensate polishing system when necessary.

[0036] Step 3: Start the backup vacuum pump

[0037] After the circulating water pump is removed, the condenser vacuum will deteriorate, so the standby vacuum pump needs to be started to maintain the condenser vacuum;

[0038] Step 4: Fill the condenser with water to the highest level

[0039] The condensate in the condenser will flow to the place with good vacuum. After the circulating water pump is cut off, the vacuum of the condenser corresponding to the circulating water pump will deteriorate and the liquid level will decrease. The condenser feed water pump will be overloaded and tripped. The vacuum of other condensers is relatively good, and a large amount of condensate will flow into it, causing the liquid level to exceed the range. Therefore, before stopping the circulating water pump, manually open the valve to feed water to the condenser to a high level.

[0040] Step 5: When the power is steadily reduced to below 780MW, stop the circulating water pump

[0041] When the power is stably reduced to below 780MW, the circulating water pump is cut off, the circulating water pump is opened to destroy the siphon valve to prevent the circulating water pump from reversing, and attention is paid to the idling of the circulating water pump; and the faulty circulating water pump is isolated for repair;

[0042] Step 6: Lock out the protection logic of shutting down a circulating water pump to 800MW load

[0043] After the unit is stable, the protection logic of shutting down a circulating water pump and shedding the load to 800MW is implemented;

[0044] Step 7: Slowly increase the unit power to complete the unit operating status adjustment

[0045] Slowly increase the unit power to meet the value of the unit power and vacuum curve. Stop increasing the power when the maximum value of the condenser vacuum reading reaches -90kPa, pay attention to the low-pressure cylinder exhaust temperature to prevent it from exceeding 60℃, and check whether the low-pressure cylinder exhaust temperature and condenser vacuum meet the water saturation vacuum diagram; 1KPa vacuum difference corresponds to about 100mm water level height difference, so as to check the condenser liquid level difference under different vacuum, and prevent the condenser vacuum gauge from displaying inaccurately from these two aspects.

[0046] The present invention is described in detail above with reference to the accompanying drawings and embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the field without departing from the purpose of the present invention. The contents not described in detail in the present invention can adopt the existing technology.

Claims

1. A method for adjusting the operating state of a circulating water pump unit when a VVER unit is shut down, characterized in that: The method comprises: Step 1: Before the circulating water pump stops operating, steadily reduce the power to the preset power; Step 2: Put the condensate polishing system into operation; Step 3: Start the standby vacuum pump; Step 4: Fill the condenser with water to a high level; Step 5: When the power is stably reduced to below the preset power, the circulating water pump is stopped; Step 6: Lock and stop one circulating water pump; Step 7: Slowly increase the unit power to complete the unit operating status adjustment.

2. The method for adjusting the operating state of a circulating water pump unit when a VVER unit is shut down according to claim 1, characterized in that: The preset power in step 1 and step 5 is below 780MW.

3. The method for adjusting the operating state of a circulating water pump unit when a VVER unit is shut down according to claim 1, characterized in that: The step 2 comprises: Step 2.1: Put into operation a condensate polishing system; Step 2.2: When water quality deteriorates, put the backup condensate polishing system into use.

4. The method for adjusting the operating state of a VVER unit when one circulating water pump unit is shut down according to claim 3, characterized in that: In the step 2.1, a condensate polishing system is introduced into the circulating cooling water pipeline of the condenser to purify the quality of the condensate.

5. The method for adjusting the operating state of a VVER unit when one circulating water pump unit is shut down according to claim 3, characterized in that: In step 2.2, a standby condensate polishing system is put into use according to the water quality of the secondary circuit condensate, feed water and wastewater from the steam generator.

6. The method for adjusting the operating state of a circulating water pump unit when a VVER unit is shut down according to claim 1, characterized in that: In step 4, water is added to the condenser to a high level by manually opening a valve.

7. The method for adjusting the operating state of a VVER unit when one circulating water pump unit is shut down according to claim 2, characterized in that: In step 6, the protection logic of shutting down a circulating water pump to shed load to 800MW is locked.

8. The method for adjusting the operating state of a VVER unit when one circulating water pump unit is shut down according to claim 1, characterized in that: In step 7, the unit power is slowly increased to meet the value of the unit power and vacuum curve.

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