A method for overpressure protection of primary circuit water pressure test in nuclear power plant

Abstract

The present invention belongs to the technical field of overpressure protection during the water pressure test of the primary circuit of a nuclear power plant, and specifically relates to a method for realizing simple and effective overpressure protection of the primary circuit water pressure test when the entire primary circuit needs a water pressure test after the overhaul of the nuclear power plant. The measurement signals of four pressure gauges are connected to the DCS signal acquisition cabinet, and the designed overpressure protection setting value is written into the DCS software. The DCS software processes and calculates the collected signals according to the overpressure protection setting value. When the measured pressure value exceeds the setting value, the pressure relief valve is opened to release the pressure or the water pressure test pump is shut down to prevent the primary circuit from overpressure; and a preliminary experiment of the water pressure test of the primary circuit is carried out. The present invention can avoid accidental pressure relief of the primary circuit due to malfunction of the protection system during overpressure or boosting of the primary circuit, which ultimately leads to water pressure failure of the entire primary circuit.

Description

Technical Field

[0001] The invention belongs to the technical field of overpressure protection during a primary circuit water pressure test of a nuclear power plant, and specifically relates to a method for realizing simple and effective primary circuit water pressure test overpressure protection when the entire primary circuit needs a water pressure test after an overhaul of a nuclear power plant. Background Art

[0002] The purpose of the primary circuit water pressure test of a nuclear power plant is to make the reactor coolant system withstand an appropriate water pressure test pressure higher than the normal operating pressure, so as to prove that the reactor primary circuit system is safe in normal operation and designed accident conditions during the period from the end of this test to the implementation of the next test, and meets the requirements of nuclear safety regulations. According to the requirements of nuclear safety regulations: the interval between two water pressure tests shall not exceed 10 years, but the first water pressure test must be completed within 30 months after the first test.

[0003] Therefore, nuclear power plants should perform primary circuit water pressure tests during the engineering construction and overhaul stages. The main risk faced by the test is that the primary circuit is over-pressurized or the protection system malfunctions during the pressure increase, resulting in accidental pressure relief in the primary circuit, which ultimately leads to the failure of the entire water pressure. During the test, the primary circuit pressure needs to be raised to 20.6MPa (1.2 times the design pressure). If the overpressure is small, it will affect the service life of the primary circuit main equipment, and if it is serious, the primary circuit boundary will be damaged and a large amount of radioactive materials will leak. During the primary circuit water pressure test, in order to prevent accidental pressure relief in the primary circuit, the safety valve used for primary circuit overpressure protection during operation is locked and cannot play the overpressure protection function. Therefore, how to establish a set of highly stable and operable overpressure protection methods has become an important issue. Summary of the invention

[0004] The purpose of the present invention is to provide a method for overpressure protection of a primary circuit water pressure test in a nuclear power plant with high stability and strong operability, so as to avoid accidental pressure relief of the primary circuit due to malfunction of the protection system during overpressure or pressure increase of the primary circuit, and ultimately cause water pressure failure of the entire primary circuit.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for overpressure protection of a primary circuit water pressure test in a nuclear power plant,

[0007] Step 1: Prepare four pressure gauges with different ranges. The first pressure gauge has a range of 0-25MPa, the second pressure gauge has a range of 15-25MPa, the third pressure gauge has a range of 0-40MPa, and the fourth pressure gauge has a range of 11-18MPa.

[0008] Step 2: Install the four pressure gauges at the designated positions of a circuit for pressure measurement. The first and second pressure gauges are installed by leading out an instrument pipeline separately on the negative pressure side of the level measuring instrument of the pressurizer. The third pressure gauge is installed at the highest point of the pressurizer. The fourth pressure gauge is an original device of the process system and does not need to be installed again.

[0009] Step 3: After the pressure gauge is installed, put it into operation, add water pressure to the installed pressure gauge pipeline to the test pressure, and observe whether there is leakage. If there is leakage, it needs to be handled. After each treatment, it is necessary to re-test the pressure until there is no leakage;

[0010] Step 4: Connect the measurement signals of the four pressure gauges to the DCS signal acquisition cabinet, and write the designed overpressure protection setting value into the DCS software. The DCS software processes and calculates the collected signals according to the overpressure protection setting value. When the measured pressure value exceeds the setting value, the pressure relief valve is opened to release the pressure or the water pressure test pump is shut down to prevent overpressure in the primary circuit.

[0011] Preliminary experiment of primary circuit water pressure test;

[0012] Step 5: Pressurize until the third pressure gauge displays 2.5 MPa, and record the readings of the four pressure gauges respectively;

[0013] Step 6: Pressurize until the third pressure gauge displays 7MPa, and record the readings of the four pressure gauges respectively;

[0014] Step 7: Pressurize until the third pressure gauge displays 10 MPa, and record the readings of the four pressure gauges respectively;

[0015] Step 8: Pressurize until the third pressure gauge displays 15.4MPa, and record the readings of the four pressure gauges respectively; continue to increase the pressure until the third pressure gauge displays 16.8MPa, and the pressure measured by the fourth pressure gauge will be compared with the set value of 16.8MPa in the DCS software. When the measured pressure exceeds the set value of 16.8MPa, the fourth pressure gauge will generate an alarm in the DCS software to remind that the primary circuit pressure has risen abnormally;

[0016] Step 9: Pressurize until the third pressure gauge displays 17.2MPa, and record the readings of the four pressure gauges respectively; the pressure measured by the fourth pressure gauge will be compared with the set value of 17.2MPa in the DCS software. When the measured pressure exceeds the set value of 17.2MPa in the DCS software, the fourth pressure gauge will generate a control command to open the primary pressure relief valve in the DCS software to achieve pressure relief;

[0017] Step 10: In the DCS software, lock the fourth pressure gauge to generate a control command to open the primary circuit pressure relief valve when the pressure measured exceeds the set value of 17.2MPa;

[0018] Step 11: Pressurize until the third pressure gauge displays 20.6MPa, and record the readings of the four pressure gauges respectively; continue to increase the pressure until the third pressure gauge displays 21.0MPa, and the pressure measured by the first pressure gauge will be compared with the set value 21.0MPa in the DCS software. When the measured pressure exceeds the set value 21.0MPa, the first pressure gauge will generate a control command to stop the water pressure test pump in the DCS software, and the water pressure test pump will stop, and the pressure increase of the first circuit will stop to avoid overpressure in the first circuit; if the third pressure gauge continues to rise to 21.2MPa at this time, the measured value of the second pressure gauge will be compared with the set value 21.2MPa in the DCS software, and the second pressure gauge will generate a control command to open the pressure relief valve of the first circuit in the DCS software to achieve pressure relief;

[0019] Step 12: Release the pressure until the third pressure gauge shows 15.4 MPa. In the DCS software, restore the pressure measured by the fourth pressure gauge to exceed the set value of 17.2 MPa, generate a control command to open the primary circuit pressure relief valve, and the pressure continues to drop to 0 MPa.

[0020] Step 13: Verify that the overpressure protection function is operating normally through simulation from step 5 to step 12. When the readings of the four pressure gauges are consistent at 2.5MPa, 7MPa, 10MPa, 15.4MPa, 17.2MPa, and 20.6MPa, the formal water pressure test will begin;

[0021] Step 14: To enter the formal water pressure test, you only need to replace the manual pressurization in steps 5 to 12 with the pressurization of the formal water pressure test pump. Repeat steps 5 to 12 to achieve overpressure protection for the single-circuit water pressure test.

[0022] Step 2: After the pressure gauge is installed, the pressure gauge range needs to be moved according to the actual height on site.

[0023] Step 3: Use a manual pressure pump to increase the water pressure test pressure on the installed pressure gauge pipeline.

[0024] Step 3: Add water pressure to the installed pressure gauge pipeline to the test pressure and maintain the pressure for 10 minutes.

[0025] Step 5: Use a manual pressure pump to increase the pressure until the third pressure gauge displays 2.5MPa.

[0026] Step 6: Use a manual pressure pump to increase the pressure until the third pressure gauge displays 7MPa.

[0027] Step 7: Use a manual pressure pump to increase the pressure until the third pressure gauge displays 10MPa.

[0028] Step 8: Use a manual pressure booster pump to increase the pressure until the third pressure gauge displays 15.4 MPa; continue to increase the pressure using the manual pressure booster pump until the third pressure gauge displays 16.8 MPa.

[0029] Step 9: Use a manual pressure pump to increase the pressure until the third pressure gauge displays 17.2MPa.

[0030] Step 11: Use a manual pressure booster pump to increase the pressure until the third pressure gauge displays 20.6 MPa; continue to increase the pressure using the manual pressure booster pump until the third pressure gauge displays 21.0 MPa.

[0031] The beneficial effects achieved by the present invention are:

[0032] 1) Overpressure protection is achieved through a digital DCS system. The software is easy to write, and the data during the test can be displayed and stored in real time, with strong data traceability.

[0033] 2) Conduct a preliminary test before the water pressure test: mainly to verify that there is no leakage in the pressure transmitter interface and the correctness of the overpressure logic. This can effectively avoid the failure of the single-loop water pressure test due to problems in the pressure transmitter installation, range setting, and protection logic link during the formal water pressure test.

[0034] 3) This method uses multiple pressure transmitters to measure the pressure of a circuit, which can effectively avoid test failure caused by a single failure of the pressure transmitter.

[0035] 4) Temporary instruments are installed in places with low environmental dose rates on the nuclear island, effectively reducing the radiation dose of workers. DETAILED DESCRIPTION

[0036] The present invention is described in detail below with reference to specific embodiments.

[0037] The method for overpressure protection of a primary circuit water pressure test in a nuclear power plant according to the present invention comprises the following steps:

[0038] Step 1: Prepare four pressure gauges with different ranges. The first pressure gauge has a range of 0-25MPa, the second pressure gauge has a range of 15-25MPa, the third pressure gauge has a range of 0-40MPa, and the fourth pressure gauge has a range of 11-18MPa.

[0039] Step 2: Install the four pressure gauges at the designated positions of a circuit for pressure measurement. The first and second pressure gauges are installed by leading out a separate instrument pipeline on the negative pressure side of the level measuring instrument of the pressurizer. The third pressure gauge is installed at the highest point of the pressurizer. The fourth pressure gauge is an original device of the process system and does not need to be installed again. After the pressure gauge is installed, the range of the pressure gauge needs to be migrated according to the actual height of the site.

[0040] Step 3: After the pressure gauge is installed, put it into operation, use a manual pressure pump to increase the water pressure test pressure on the installed pressure gauge pipeline, and maintain the pressure for 10 minutes to observe whether there is any leakage. If there is any leakage, it needs to be handled (after each treatment, the pressure test needs to be carried out again until there is no leakage).

[0041] Step 4: Connect the measurement signals of the four pressure gauges in step 1 to the DCS signal acquisition cabinet, and write the designed overpressure protection setting value into the DCS software. The DCS software processes and calculates the collected signals according to the overpressure protection setting value. When the measured pressure value exceeds the setting value, open the pressure relief valve to release the pressure or shut down the water pressure test pump to prevent overpressure in one circuit.

[0042] Preliminary experiment of primary circuit water pressure test;

[0043] Step 5: Use a manual pressure pump to increase the pressure until the third pressure gauge displays 2.5 MPa, and record the readings of the four pressure gauges in step 1 respectively.

[0044] Step 6: Use a manual pressure pump to increase the pressure until the third pressure gauge displays 7MPa, and record the readings of the four pressure gauges in step 1 respectively.

[0045] Step 7: Use a manual pressure pump to increase the pressure until the third pressure gauge displays 10 MPa, and record the readings of the four pressure gauges in step 1 respectively.

[0046] Step 8: Use the manual booster pump to increase the pressure until the third pressure gauge displays 15.4MPa, and record the readings of the four pressure gauges in step 1 respectively; continue to increase the pressure by the manual booster pump until the third pressure gauge displays 16.8MPa, and the pressure measured by the fourth pressure gauge will be compared with the set value of 16.8MPa in the DCS software. When the measured pressure exceeds the set value (16.8MPa), the fourth pressure gauge will generate an alarm in the DCS software to remind that the pressure in the first circuit has risen abnormally.

[0047] Step 9: Use a manual pressure pump to increase the pressure until the third pressure gauge displays 17.2MPa, and record the readings of the four pressure gauges in step 1 respectively; the pressure measured by the fourth pressure gauge will be compared with the set value of 17.2MPa in the DCS software. When the measured pressure exceeds the set value (17.2MPa) in the DCS software, the fourth pressure gauge will generate a control command in the DCS software to open the primary pressure relief valve to achieve pressure relief.

[0048] Step 10: In the DCS software, lock the fourth pressure gauge to generate a control command to open the primary pressure relief valve when the pressure measured exceeds the set value (17.2MPa).

[0049] Step 11: Use the manual pressure booster pump to increase the pressure until the third pressure gauge displays 20.6MPa, and record the readings of the four pressure gauges in step 1 respectively; continue to increase the pressure by the manual pressure booster pump until the third pressure gauge displays 21.0MPa, and the pressure measured by the first pressure gauge will be compared with the set value 21.0MPa in the DCS software. When the measured pressure exceeds the set value (21.0MPa), the first pressure gauge will generate a control command to stop the water pressure test pump in the DCS software, and the water pressure test pump will stop, and the pressure in the first circuit will stop increasing to avoid overpressure in the first circuit; if the third pressure gauge continues to rise to 21.2MPa at this time, the measured value of the second pressure gauge will be compared with the set value 21.2MPa in the DCS software, and the second pressure gauge will generate a control command to open the pressure relief valve of the first circuit in the DCS software to achieve pressure relief.

[0050] Step 12: Release the pressure until the third pressure gauge shows 15.4 MPa. In the DCS software, restore the pressure measured by the fourth pressure gauge to exceed the set value of 17.2 MPa, generate a control command to open the primary circuit pressure relief valve, and the pressure continues to drop to 0 MPa.

[0051] Step 13: Verify through steps 5 to 12 that the overpressure protection function can be normally executed. When the readings of the four pressure gauges are consistent at the platforms of 2.5MPa, 7MPa, 10MPa, 15.4MPa, 17.2MPa and 20.6MPa, the formal water pressure test can be started.

[0052] Step 14: To enter the formal water pressure test, you only need to replace the manual pressure pump pressurization in steps 5 to 12 with the formal water pressure test pump pressurization. Repeat steps 5 to 12 to achieve overpressure protection for the single-circuit water pressure test.

Claims

1. A method for overpressure protection of a primary circuit water pressure test in a nuclear power plant, characterized in that: Step 1: Prepare four pressure gauges with different ranges. The first pressure gauge has a range of 0-25MPa, the second pressure gauge has a range of 15-25MPa, the third pressure gauge has a range of 0-40MPa, and the fourth pressure gauge has a range of 11-18MPa. Step 2: Install the four pressure gauges at the designated positions of a circuit for pressure measurement. The first and second pressure gauges are installed by leading out an instrument pipeline separately on the negative pressure side of the level measuring instrument of the pressurizer. The third pressure gauge is installed at the highest point of the pressurizer. The fourth pressure gauge is an original device of the process system and does not need to be installed again. Step 3: After the pressure gauge is installed, put it into operation, add water pressure to the installed pressure gauge pipeline to the test pressure, and observe whether there is leakage. If there is leakage, it needs to be handled. After each treatment, it is necessary to re-test the pressure until there is no leakage; Step 4: Connect the measurement signals of the four pressure gauges to the DCS signal acquisition cabinet, and write the designed overpressure protection setting value into the DCS software. The DCS software processes and calculates the collected signals according to the overpressure protection setting value. When the measured pressure value exceeds the setting value, the pressure relief valve is opened to release the pressure or the water pressure test pump is shut down to prevent overpressure in the primary circuit. Preliminary experiment of primary circuit water pressure test; Step 5: Pressurize until the third pressure gauge displays 2.5 MPa, and record the readings of the four pressure gauges respectively; Step 6: Pressurize until the third pressure gauge displays 7MPa, and record the readings of the four pressure gauges respectively; Step 7: Pressurize until the third pressure gauge displays 10 MPa, and record the readings of the four pressure gauges respectively; Step 8: Pressurize until the third pressure gauge displays 15.4MPa, and record the readings of the four pressure gauges respectively; continue to increase the pressure until the third pressure gauge displays 16.8MPa, and the pressure measured by the fourth pressure gauge will be compared with the set value of 16.8MPa in the DCS software. When the measured pressure exceeds the set value of 16.8MPa, the fourth pressure gauge will generate an alarm in the DCS software to remind that the primary circuit pressure has risen abnormally; Step 9: Pressurize until the third pressure gauge displays 17.2MPa, and record the readings of the four pressure gauges respectively; the pressure measured by the fourth pressure gauge will be compared with the set value of 17.2MPa in the DCS software. When the measured pressure exceeds the set value of 17.2MPa in the DCS software, the fourth pressure gauge will generate a control command to open the primary pressure relief valve in the DCS software to achieve pressure relief; Step 10: In the DCS software, lock the fourth pressure gauge to generate a control command to open the primary circuit pressure relief valve when the pressure measured exceeds the set value of 17.2MPa; Step 11: Pressurize until the third pressure gauge displays 20.6MPa, and record the readings of the four pressure gauges respectively; continue to increase the pressure until the third pressure gauge displays 21.0MPa, and the pressure measured by the first pressure gauge will be compared with the set value 21.0MPa in the DCS software. When the measured pressure exceeds the set value 21.0MPa, the first pressure gauge will generate a control command to stop the water pressure test pump in the DCS software, and the water pressure test pump will stop, and the pressure increase of the first circuit will stop to avoid overpressure in the first circuit; if the third pressure gauge continues to rise to 21.2MPa at this time, the measured value of the second pressure gauge will be compared with the set value 21.2MPa in the DCS software, and the second pressure gauge will generate a control command to open the pressure relief valve of the first circuit in the DCS software to achieve pressure relief; Step 12: Release the pressure until the third pressure gauge shows 15.4 MPa. In the DCS software, restore the pressure measured by the fourth pressure gauge to exceed the set value of 17.2 MPa, generate a control command to open the primary circuit pressure relief valve, and the pressure continues to drop to 0 MPa. Step 13: Verify that the overpressure protection function is operating normally through simulation from step 5 to step 12. When the readings of the four pressure gauges are consistent at 2.5MPa, 7MPa, 10MPa, 15.4MPa, 17.2MPa, and 20.6MPa, the formal water pressure test will begin; Step 14: To enter the formal water pressure test, you only need to replace the pressurization in steps 5 to 12 with the pressurization of the formal water pressure test pump, and repeat steps 5 to 12 to achieve overpressure protection for the single-circuit water pressure test.

2. The method for overpressure protection of a primary circuit water pressure test in a nuclear power plant according to claim 1, characterized in that: Step 2: After the pressure gauge is installed, the pressure gauge range needs to be moved according to the actual height on site.

3. The method for overpressure protection of a primary circuit water pressure test in a nuclear power plant according to claim 1, characterized in that: Step 3: Use a manual pressure pump to increase the water pressure test pressure on the installed pressure gauge pipeline.

4. The method for overpressure protection of a primary circuit water pressure test in a nuclear power plant according to claim 1, characterized in that: Step 3: Add water pressure to the installed pressure gauge pipeline to the test pressure and maintain the pressure for 10 minutes.

5. The method for overpressure protection of a primary circuit water pressure test in a nuclear power plant according to claim 1, characterized in that: Step 5: Use a manual pressure pump to increase the pressure until the third pressure gauge displays 2.5MPa.

6. The method for overpressure protection of a primary circuit water pressure test in a nuclear power plant according to claim 1, characterized in that: Step 6: Use a manual pressure pump to increase the pressure until the third pressure gauge displays 7MPa.

7. The method for overpressure protection of a primary circuit water pressure test in a nuclear power plant according to claim 1, characterized in that: Step 7: Use a manual pressure pump to increase the pressure until the third pressure gauge displays 10MPa.

8. The method for overpressure protection of a primary circuit water pressure test in a nuclear power plant according to claim 1, characterized in that: Step 8: Use a manual pressure booster pump to increase the pressure until the third pressure gauge displays 15.4 MPa; continue to increase the pressure using the manual pressure booster pump until the third pressure gauge displays 16.8 MPa.

9. The method for overpressure protection of a primary circuit water pressure test in a nuclear power plant according to claim 1, characterized in that: Step 9: Use a manual pressure pump to increase the pressure until the third pressure gauge displays 17.2MPa.

10. The method for overpressure protection of a primary circuit water pressure test in a nuclear power plant according to claim 1, characterized in that: Step 11: Use a manual pressure booster pump to increase the pressure until the third pressure gauge displays 20.6 MPa; continue to increase the pressure using the manual pressure booster pump until the third pressure gauge displays 21.0 MPa.