Hydraulic pressure test method for sealing performance of main equipment of nuclear power unit

Abstract

The invention relates to the technical field of nuclear power, in particular to a hydraulic test method for sealing performance of main equipment of a nuclear power unit. The method comprises the following steps: confirming states of primary loop equipment and secondary loop equipment and closing of all valves and pipelines at a primary loop hydraulic pressure test boundary; performing a cold-state hydrostatic test on the primary loop; performing dynamic exhaust on the primary loop; starting a main pump to heat the primary loop, synchronously heating the secondary loop by using the coolant temperature of the primary loop, and performing leak detection during heating; increasing the pressure of a loop to a pressure platform of 16.1-16.3 MPa by temporarily changing and modifying the pressure constant value of the pressure stabilizer, and performing leak detection; after the test is finished, the pressure constant value of the pressure stabilizer is recovered, the primary loop pressure is reduced to rated pressure, and the reactor is kept in a thermal state. According to the invention, the test process is simplified, the test pressure is reduced, the control precision of the test process is improved, the accuracy and reliability of the test are effectively improved, and the potential damage risk to the component is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power, and in particular to a method for hydrostatic pressure test of the main equipment sealing of a nuclear power unit. Background Art

[0002] In accordance with the requirements of nuclear safety regulations, in order to test the strength and integrity of pipelines and equipment, nuclear power plant operators need to regularly conduct pressure tests during the operation of the unit. According to different inspection purposes, the pressure tests are divided into strength hydrostatic pressure tests and sealing tests. During the refueling overhaul of the unit, some nuclear-grade equipment within the normal operation boundary has been disassembled and resealed. In order to confirm the sealing of the restored operation boundary and meet the operation requirements of the unit, a sealing test is carried out before the reactor resumes operation.

[0003] As a highly complex and extremely safety-demanding energy system, the pressure-bearing components of a nuclear power plant (such as pressure vessels, main coolant pumps, steam generators, pressurizers, main pipelines, valves, etc.) need to withstand extremely high pressures and temperatures under normal operation and accident conditions. Hydrostatic pressure test, as an important means to test the sealing of these components, is crucial for ensuring the safety of nuclear power plants. However, the traditional method for hydrostatic pressure test of sealing has the following defects:

[0004] (1) Long test duration: The test requires the unit to be shut down, which affects power generation efficiency and economy. The equipment operates at a pressure higher than the design pressure for a long time, and there is a relatively high risk of potential damage to the pressure-bearing components of the primary circuit. Moreover, with the long-term heating of the residual heat of the reactor, there is a high risk of misoperation of the reactor and the dedicated safety system protection due to the over-limit temperature of the primary coolant.

[0005] (2) High overpressure risk: Under frequent and relatively high sealing test pressures, there is a relatively high risk of fatigue damage to the main equipment and pipelines. The reliability of valves and other components at the sealing boundary will be affected. Since the method of manual inspection is used to detect leaks during the test, the industrial safety risk of the inspection personnel is relatively high.

[0006] (3) Complex operation: Traditional hydrostatic pressure test requires first filling the reactor and heating it to the hydrostatic pressure test temperature for the test. After the test, the reactor and the steam generator need to be depressurized and drained, and the states of the primary and secondary circuits need to be restored before the unit can be started. The operation is cumbersome and requires high skills for personnel, and human error is likely to occur.

[0007] (4) Online complexity: The boundary of the traditional hydrostatic pressure test is the second isolation valve connected to the pipeline and equipment, which is inconsistent with the normal operation boundary, and the hydrostatic pressure test boundary needs to be changed multiple times during the test process. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for hydrostatic test of the main equipment sealing of a nuclear power unit. By optimizing the test method and using the reactor heating section for the main equipment sealing hydrostatic test, the test process is simplified, the test pressure is reduced, the control accuracy of the test process is improved, the accuracy and reliability of the test are effectively improved, and the potential damage risk to components is reduced.

[0009] The present invention provides a method for hydrostatic test of the main equipment sealing of a nuclear power unit, with the primary loop sealing hydrostatic test boundary as the operating boundary, including the following steps:

[0010] Step 1: Confirm the states of the primary loop equipment and the secondary loop equipment, and close all valves and pipelines at the primary loop hydrostatic test boundary;

[0011] Step 2: Conduct a cold hydrostatic test on the primary loop;

[0012] Step 3: Conduct dynamic gas exhaust on the primary loop;

[0013] Step 4: Start the main pump to heat the primary loop, and use the primary loop coolant temperature to synchronously heat the secondary loop. During the heating period, conduct leak detection;

[0014] Step 5: Temporarily modify the pressure setting value of the pressurizer to raise the primary loop pressure to the pressure platform of 16.1 - 16.3 MPa and conduct leak detection;

[0015] Step 6: After the test, restore the pressure setting value of the pressurizer, reduce the primary loop pressure to the rated pressure, and the reactor maintains the hot state.

[0016] In a specific embodiment of the present invention, the specific content of Step 1 includes:

[0017] Step 1-1: Confirm that all primary loop equipment participating in the test is in good condition and the primary loop has the heating condition;

[0018] Step 1-2: Check and close all valves and channels at the primary loop hydrostatic test boundary to ensure that the pressure will not leak to other systems during the test process;

[0019] Step 1-3: Confirm that the secondary loop equipment is in good condition and the secondary loop has the starting condition.

[0020] In a specific embodiment of the present invention, the specific content of Step 2 includes:

[0021] Step 2-1: Fill the primary loop and conduct sufficient gas exhaust to ensure that the primary loop is completely filled;

[0022] Step 2-2: Use the charging pump to inject coolant into the primary loop, raise the primary loop pressure to the 3.2 MPa platform at a speed not exceeding 0.98 MPa / min, and conduct leak detection.

[0023] In a specific embodiment of the present invention, step 3 specifically includes:

[0024] Step 3-1: After the primary circuit has the heating condition, start the main pump to heat the primary circuit, and ensure that the pressure of the primary circuit is increased to the rated pressure of 15.78 MPa at a rate not exceeding 0.98 MPa / min by controlling the heating rate of the primary circuit. During this period, leak detection is carried out at the pressure platforms of 2.9 - 3.4 MPa and 9.5 - 10.1 MPa in the primary circuit;

[0025] Step 3-2: Use the temperature of the primary circuit coolant to heat the feed water of the secondary circuit synchronously, and leak detection is carried out at the pressure platforms of 2.0 - 3.0 MPa and 6.0 - 6.4 MPa in the secondary circuit.

[0026] In a specific embodiment of the present invention, step 4 specifically includes:

[0027] Step 3-1: Reduce the pressure of the primary circuit to 1.5 - 1.8 MPa and establish a nitrogen cushion in the pressurizer;

[0028] Step 3-2: After starting the main pump and running for 10 - 20 min, conduct dynamic exhaust of the primary circuit.

[0029] In a specific embodiment of the present invention, in step 5, the set value of the pressurizer pressure is temporarily changed and modified to 16.15 MPa.

[0030] In a specific embodiment of the present invention, in step 6, after the test is completed, the set value of the pressurizer pressure is restored to 15.78 MPa.

[0031] In a specific embodiment of the present invention, the boundary of the primary circuit seal water pressure test is that the reactor primary circuit coolant enters the reactor through the reactor main coolant pipeline driven by the main pump. After the coolant absorbs the heat released by the fission reaction in the reactor, it flows out of the reactor, enters the steam generator through the main coolant pipeline, is cooled by the secondary circuit medium in the steam generator, and then returns to the inlet of the main pump of each loop to form a closed cycle. A pressurizer is arranged on the third and fourth loops to maintain the pressure of the primary circuit during the reactor power operation; on the reactor main coolant pipeline, medium-pressure safety injection pipelines, high-pressure safety injection pipelines, low-pressure safety injection pipelines, emergency boron injection pipelines, residual heat removal pipelines, and emergency spray pipeline nozzles are arranged to ensure the safe shutdown of the reactor under accident conditions; on the reactor main coolant pipeline, volume and boron control system pipelines are also arranged to fill the primary circuit and compensate for the change in the coolant water inventory.

[0032] Compared with the prior art, the main equipment seal water pressure test method of the nuclear power unit of the present invention has the following beneficial effects:

[0033] (1)Effectively reduce the nuclear risk and operation risk during the hydrostatic test operation, avoid overpressure in the primary and secondary circuits, and increase the economic benefits of the generator set.

[0034] (2)Improve the accuracy and reliability of the test, reduce the test pressure and increase the test temperature, effectively control the pressure change rate of the primary and secondary circuit equipment and pipelines during the test, prevent their deformation and damage, and reduce the potential damage risk to components.

[0035] (3)Effectively shorten the test duration, improve work efficiency, reduce the operation event risk of the primary and secondary circuit equipment under high-pressure conditions, and provide a strong guarantee for the safe operation of the nuclear power plant.

[0036] (4)Greatly simplify the test steps, significantly reduce the operation difficulty of personnel during the hydrostatic test, improve work efficiency and reduce the risk of human error;

[0037] (5)During the sealed hydrostatic test, the safety valve of the pressurizer and the main steam valve group are normally put into use, ensuring the overpressure protection function of the primary and secondary circuits.

[0038] (6)Reduce the test pressure and test time, increase the test temperature, eliminate the fatigue damage risk of the primary and secondary circuit equipment and pipelines, and reduce the industrial safety risk of the inspection personnel.

[0039] (7)Adjust the sealed hydrostatic test boundary of the primary circuit to be consistent with the normal operation boundary, cancel the hydrostatic test boundary of the secondary circuit, which can truly represent the sealing performance during the normal operation of the unit, and is more conducive to the optimization of the test duration and the collective dose of personnel. Description of the Drawings

[0040] Figure 1 It represents a simplified diagram of the sealed hydrostatic test boundary of the primary circuit of the VVER reactor;

[0041] In the figure, 1 - reactor; 2 - main coolant pump; 3 - steam generator; 4 - pressurizer; 5 - reactor main coolant pipeline; 6 - medium-pressure safety injection pipeline; 7 - pressurizer emergency spray pipeline; 8 - emergency boron injection pipeline; 9 - high-pressure safety injection pipeline; 10 - low-pressure safety injection pipeline; 11 - reactor residual heat removal pipeline; 12 - volume and boron control system pipeline. Detailed Embodiments

[0042] In order to further understand the present invention, the implementation scheme of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the present invention.

[0043] When the reactor of the present invention is heated to the hot state, the main equipment sealing test is carried out synchronously. By controlling the heating rate of the primary loop, it is ensured that the pressure change rate during the hydrostatic test does not exceed the limit. After the reactor reaches the rated pressure of the hot state, the pressure of the primary loop is continuously increased to the sealing hydrostatic test platform by temporarily changing the pressure setting value of the pressurizer to continue the main equipment sealing test. During the reactor heating process, the feed water of the secondary loop is heated synchronously by using the temperature of the primary loop coolant, and the secondary loop sealing hydrostatic test is carried out synchronously.

[0044] An embodiment of the present invention discloses a method for the main equipment sealing hydrostatic test of a nuclear power unit, with the primary loop sealing hydrostatic test boundary as the operating boundary, as Figure 1 shown

[0045] The primary loop coolant of the reactor 1 enters the reactor through the reactor main coolant pipeline driven by the main pump 2. After the coolant absorbs the heat released by the fission reaction in the reactor, it flows out of the reactor, enters the steam generator 3 through the main coolant pipeline, and returns to the inlet of the main pump of each loop after being cooled by the secondary loop medium in the steam generator, forming a closed cycle. A pressurizer 4 is arranged on the third and fourth loops to maintain the pressure of the primary loop during the reactor power operation; a medium-pressure safety injection pipeline 6, a high-pressure safety injection pipeline 9, a low-pressure safety injection pipeline 10, an emergency boron injection pipeline 8, a residual heat removal pipeline 11, and an emergency spray pipeline 7 are connected to the reactor main coolant pipeline to ensure the safe shutdown of the reactor in case of an accident; a volume and boron control system pipeline 7 is also arranged on the reactor main coolant pipeline to fill the primary loop and compensate for the change in the coolant water inventory.

[0046] The method for the main equipment sealing hydrostatic test of a nuclear power unit includes the following steps:

[0047] Step 1: Confirm the states of the primary loop equipment and the secondary loop equipment, and close all valves and pipelines at the primary loop hydrostatic test boundary;

[0048] Specifically, it includes:

[0049] Step 1-1: Confirm that all primary loop equipment participating in the test is in good condition and the primary loop has the heating condition;

[0050] The primary loop equipment includes primary loop main equipment, charging pumps, letdown regulating valves, etc.;

[0051] Step 1-2: Check and close all valves and channels at the primary loop hydrostatic test boundary to ensure that the pressure will not leak to other systems during the test;

[0052] Step 1-3: Confirm that the secondary loop equipment is in good condition and the secondary loop has the start-up condition;

[0053] The secondary loop equipment includes steam generators, auxiliary feed pumps, main feed pumps, main feed water valve groups, main steam valve groups, etc.;

[0054] Step 2: Conduct a cold hydrostatic test on the primary loop;

[0055] Specifically:

[0056] Step 2-1: Fill the primary loop and exhaust it thoroughly to ensure that the primary loop is completely filled;

[0057] Step 2-2: Use the charging pump to inject coolant into the primary loop, raise the pressure of the primary loop to the 3.2 MPa plateau at a rate not exceeding 0.98 MPa / min, and conduct leak detection;

[0058] Step 3: Conduct dynamic exhaust on the primary loop;

[0059] Specifically:

[0060] Step 3-1: Lower the pressure of the primary loop to 1.5 - 1.8 MPa and establish a nitrogen cushion in the pressurizer;

[0061] Step 3-2: Start the main pump and run it for 10 - 20 minutes, then conduct dynamic exhaust on the primary loop;

[0062] Step 4: Heat the primary loop;

[0063] Step 4-1: After the primary loop meets the heating conditions, start the main pump to heat the primary loop. Ensure that the pressure of the primary loop is raised to the rated pressure of 15.78 MPa at a rate not exceeding 0.98 MPa / min by controlling the heating rate of the primary loop. During this period, conduct leak detection at the 2.9 - 3.4 MPa and 9.5 - 10.1 MPa plateaus of the primary loop pressure;

[0064] Step 4-2: Synchronously heat the secondary loop feed water using the temperature of the primary loop coolant, and conduct leak detection at the 2.0 - 3.0 MPa and 6.0 - 6.4 MPa pressure plateaus of the secondary loop pressure;

[0065] Step 4: Temporarily modify the pressure setting value of the pressurizer to 16.15 MPa, raise the pressure of the primary loop to the 16.1 - 16.3 MPa plateau and conduct leak detection;

[0066] Step 5: After the test, restore the pressure setting value of the pressurizer to 15.78 MPa, lower the pressure of the primary loop to the rated pressure, and maintain the reactor in a hot state.

[0067] By optimizing the test method, the main equipment seal hydrostatic test is carried out using the heating section of the reactor, which simplifies the test process, reduces the test pressure, improves the control accuracy of the test process, saves 20 hours of the main line duration of the reactor refueling overhaul, effectively improves the accuracy and reliability of the test, reduces the potential damage risk to components, and provides a strong guarantee for the safe operation of nuclear power plants.

[0068] The present invention changes the preheating method. When the reactor is heated to the hot state, the main equipment sealing test is carried out synchronously, and there is no need to preheat equipment and pipelines such as the reactor and steam generator separately.

[0069] The present invention changes the pressure boosting method. By controlling the heating rate of the primary loop, it is ensured that the pressure change rate during the hydrostatic test does not exceed the limit, and there is no need to raise the reactor to the full liquid level and use a hydrostatic test pump to boost the pressure.

[0070] The present invention optimizes the test method. After the reactor reaches the rated pressure of the hot state, the pressure setting value of the pressurizer is modified by temporary change to continue raising the pressure of the primary loop to the sealing hydrostatic test platform to continue the main equipment sealing test, and the test pressure is no longer maintained by a hydrostatic test pump.

[0071] The present invention simplifies the hydrostatic test steps, cancels steps such as raising and lowering the liquid level of the reactor and restoring the system heating condition after the hydrostatic test, realizes shortening the hydrostatic test time, and reduces the reactor refueling overhaul cycle.

[0072] The present invention raises the hydrostatic test temperature, eliminates the fatigue damage risk of equipment and pipelines in the primary and secondary loops, and reduces the industrial safety risk of inspection personnel.

[0073] The present invention reduces the hydrostatic test pressure, cancels the locking steps of the pressurizer safety valve and the main steam valve group, and ensures the overpressure protection function of the primary and secondary loops.

[0074] The present invention adjusts the hydrostatic test boundary, adjusts the sealing hydrostatic test boundary of the primary loop to be consistent with the normal operation boundary, and at the same time cancels the hydrostatic test boundary of the secondary loop, which can truly represent the sealing performance during the normal operation of the unit and is more conducive to optimizing the test duration and the collective dose of personnel.

[0075] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0076] The foregoing description of the disclosed embodiments enables those skilled in the art to practice or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for hydrostatic pressure test of the main equipment sealing of a nuclear power unit, characterized in that, Taking the primary circuit sealed hydrostatic test boundary as the operating boundary, it includes the following steps: Step 1: Confirm the states of the primary circuit equipment and the secondary circuit equipment, and close all valves and pipelines of the primary circuit hydrostatic test boundary; Step 2: Conduct a cold hydrostatic test on the primary circuit; Step 3: Conduct dynamic gas exhaust on the primary circuit; Step 4: Start the main pump to heat the primary circuit, and use the primary circuit coolant temperature to synchronously heat the secondary circuit. Conduct leak detection during the heating period; Step 5: Modify the pressure setting value of the pressurizer by temporary change, raise the primary circuit pressure to the pressure platform of 16.1 - 16.3 MPa and conduct leak detection; Step 6: After the test, restore the pressure setting value of the pressurizer, lower the primary circuit pressure to the rated pressure, and the reactor maintains the hot state.

2. The method for the hydrostatic test of the sealing performance of the main equipment of a nuclear power unit according to claim 1, wherein The specific content of Step 1 includes: Step 1-1: Confirm that all primary circuit equipment participating in the test is in good condition and the primary circuit has the heating condition; Step 1-2: Check and close all valves and channels of the primary circuit hydrostatic test boundary to ensure that the pressure will not leak to other systems during the test; Step 1-3: Confirm that the secondary circuit equipment is in good condition and the secondary circuit has the starting condition.

3. The main equipment sealing hydrostatic test method for nuclear power units according to claim 1, characterized in that The specific content of Step 2 includes: Step 2-1: Fill the primary circuit and conduct sufficient gas exhaust to ensure that the primary circuit is completely filled; Step 2-2: Use the charging pump to inject coolant into the primary circuit, raise the primary circuit pressure to the 3.2 MPa platform at a speed not exceeding 0.98 MPa / min, and conduct leak detection.

4. The main equipment sealing hydrostatic test method for nuclear power units according to claim 1, wherein The specific content of Step 3 includes: Step 3-1: After the primary circuit has the heating condition, start the main pump to heat the primary circuit. By controlling the primary circuit heating speed, ensure that the primary circuit pressure is raised to the rated pressure of 15.78 MPa at a speed not exceeding 0.98 MPa / min. Conduct leak detection during the primary circuit pressure at the 2.9 - 3.4 MPa and 9.5 - 10.1 MPa platforms; Step 3-2: Use the primary circuit coolant temperature to synchronously heat the secondary circuit feed water. Conduct leak detection at the secondary circuit pressure at the 2.0 - 3.0 MPa and 6.0 - 6.4 MPa platforms.

5. The main equipment sealing water pressure test method for nuclear power units according to claim 1, characterized in that, The specific content of Step 4 includes: Step 3-1: Lower the primary circuit pressure to 1.5 - 1.8 MPa and establish a nitrogen cushion in the pressurizer; Step 3-2: Start the main pump and conduct dynamic gas exhaust on the primary circuit after running for 10 - 20 min.

6. The main equipment sealing water pressure test method for nuclear power units according to claim 1, characterized in that In Step 5, modify the pressure setting value of the pressurizer to 16.15 MPa by temporary change.

7. The method for the hydrostatic test of the main equipment sealing performance of a nuclear power unit according to claim 1, wherein In Step 6, after the test, restore the pressure setting value of the pressurizer to 15.78 MPa.

8. The method for the hydrostatic test of the sealing performance of the main equipment of a nuclear power unit according to claim 1, wherein, The primary circuit sealed hydrostatic test boundary is that the primary coolant of the reactor enters the reactor through the reactor primary coolant pipeline driven by the main pump. After the coolant absorbs the heat released by the fission reaction in the reactor, it flows out of the reactor, enters the steam generator through the primary coolant pipeline, is cooled by the secondary circuit medium in the steam generator, and then returns to the inlet of the main pump of each loop to form a closed cycle. A pressurizer is arranged on the third and fourth loops to maintain the primary circuit pressure during the reactor power operation; medium-pressure safety injection pipelines, high-pressure safety injection pipelines, low-pressure safety injection pipelines, emergency boron injection pipelines, residual heat removal pipelines, and emergency spray pipeline nozzles are arranged on the reactor primary coolant pipeline to ensure the safe shutdown of the reactor under accident conditions; volume and boron control system pipelines are also arranged on the reactor primary coolant pipeline to fill the primary circuit and compensate for the change in the coolant water inventory.

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