Method for measuring leakage current of in-core vanadium fixed probe

Abstract

The present application belongs to the technical field of leakage current measurement, and particularly relates to a kind of reactor internal vanadium fixed probe leakage current measurement method, comprising: step 1, in the detection circuit, series connection access known resistance;Step 2, calculate the leakage current and leakage correction factor of vanadium probe during operation;Step 3, statistical analysis leakage current correction factor range;Step 4, analyze whether the leakage current correction factor of the same probe changes with the change of random group, cycle, power platform;Step 5, confirm the power platform and measurement times of leakage correction factor measurement test.The present application can accurately and efficiently measure leakage current, so that the corrected current value can accurately represent the true value of the probe signal, while simplifying the requirements of vanadium probe leakage correction factor measurement test, reducing the measurement times, selecting the appropriate measurement implementation power platform, and reducing the risk of probe leakage current measurement.

Description

Technical Field

[0001] This invention belongs to the field of leakage current measurement technology, specifically relating to a method for measuring leakage current using a fixed vanadium detector inside a reactor. Background Technology

[0002] The AP1000 nuclear power plant uses in-core vanadium fixed detectors to measure current and obtain the neutron flux distribution in the reactor core. For vanadium detectors, the detector signal attenuates during transmission, requiring a leakage correction factor to correct the measured current and make it more accurately represent the true value of the detector signal. The corrected detector signal is then used to calculate the power distribution of the reactor core assemblies.

[0003] The leakage correction factor is obtained through power distribution measurement tests during reactor power ramp-up. These tests need to be repeated at different power platforms during power ramp-up. To ensure the accuracy of the leakage correction factor measurement at each power platform, a leakage correction factor measurement must be performed before measuring the power distribution at each platform. Because the current obtained from the vanadium fixed detectors is weak, and because an additional resistor is required when measuring the leakage correction factor, there is a risk that the leakage correction factor may fail to be measured successfully and require repeated measurements, or that the system may not be able to return to normal operation after measurement. During the commissioning of Unit 1 of the Sanmen Nuclear Power Plant, a signal processing cabinet malfunction occurred during leakage correction factor measurement at the 25% power platform, and 50% of the detectors could not be restored to normal operation. This was ultimately resolved through containment-side fault handling. If a fault requires personnel to enter the containment to operate the cabinet, it could lead to an unplanned reactor shutdown.

[0004] Therefore, there is a need for a simple and feasible method for measuring the leakage current of vanadium fixed detectors during power operation, which would reduce the number of repeated leakage current measurements required for power distribution measurement tests on different power platforms, and be able to be implemented at low power levels, thereby reducing the risk of detector leakage current measurement. Summary of the Invention

[0005] The purpose of this invention is to provide a method for measuring the leakage current of a fixed vanadium detector in a reactor. This method can accurately and efficiently measure the leakage current, so that the corrected current value can accurately represent the true value of the detector signal. At the same time, it simplifies the requirements for measuring the leakage correction factor of the vanadium detector, reduces the number of measurements, selects a suitable measurement implementation power platform, and reduces the risk of measuring the detector leakage current.

[0006] Technical solution to achieve the purpose of this invention:

[0007] A method for measuring leakage current of a vanadium-fixed detector in a reactor, the method comprising:

[0008] Step 1: Connect a known resistor in series in the detection circuit;

[0009] Step 2: Calculate the leakage current and leakage correction factor of the vanadium detector during operation;

[0010] Step 3: Statistically analyze the range of leakage current correction factors;

[0011] Step 4: Analyze whether the leakage current correction factor of the same detector changes with the random group, cycle, and power plateau.

[0012] Step 5: Confirm the power platform and the number of measurements to be performed for the leakage correction factor measurement test.

[0013] The formula for calculating the leakage current in step 2 is as follows:

[0014]

[0015] In the formula,

[0016] I L Leakage current;

[0017] I A : Detector current;

[0018] R1: Detector resistance;

[0019] I B : The detector current after the series resistor in the detection circuit;

[0020] R2: Temporary connection resistor.

[0021] The formula for calculating the leakage correction factor in step 2 is as follows:

[0022]

[0023] In the formula,

[0024] K A Leakage correction factor.

[0025] In step 3, the leakage correction factor ranges from 1 to (1+a), where...

[0026] Step 4 includes:

[0027] Step 4.1: Confirm the original maximum negative deviation X0, the original maximum positive deviation Y0, the location of the original maximum negative deviation in the reactor core assembly, and the location of the original maximum positive deviation in the reactor core assembly.

[0028] Step 4.2: Confirm the maximum negative deviation X1 and the maximum positive deviation Y1 of the measurement-prediction value correction;

[0029] Step 4.3: Confirm the impact of variations in the detector leakage correction factor within its distribution range on the results.

[0030] In step 4.2, the maximum negative deviation X1 of the measurement-prediction value correction is: the detector measurement current at the core assembly position where the original maximum negative deviation is located and the adjacent position multiplied by (1-a); the maximum positive deviation Y1 of the measurement-prediction value correction is: the detector measurement current at the core assembly position where the original maximum positive deviation is located and the adjacent position multiplied by (1+a).

[0031] In step 4.3, if and This proves that the variation of the detector leakage correction factor within its distribution range has little impact on the results.

[0032] Step 5 specifically involves the following: Since the leakage correction factor does not change with the power level and its impact on the power distribution measurement results is negligible, the number of leakage current measurements on different power platforms should be reduced to lower the risk. Furthermore, since the lower the power level, the lower the risk of performing the measurement, a low-power platform should be selected to conduct the leakage correction factor measurement test.

[0033] The beneficial technical effects of this invention are as follows:

[0034] 1. The present invention provides a method for measuring leakage current of a fixed vanadium detector in a reactor, which can measure the leakage current attenuated during the transmission of the detector signal under reactor power operation conditions. After correcting the detector current, it can more accurately represent the true value of the detector signal and more accurately obtain the neutron flux distribution in the reactor core.

[0035] 2. The method for measuring leakage current of a fixed vanadium detector in a reactor provided by the present invention reduces the number of leakage current measurements on different power platforms and lowers the risk of multiple measurements by determining the range of leakage current data and power distribution of the detector and measuring the sensitivity of the leakage correction factor.

[0036] 3. The method for measuring leakage current of a fixed vanadium detector in a reactor provided by this invention reduces the number of leakage current measurements at different power platforms, which can reduce experimental time and power platform waiting time, and help power plants increase power generation and improve economic efficiency. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the normal operating circuit of a vanadium detector in the prior art;

[0038] Figure 2 This is a schematic diagram of the vanadium detector leakage correction factor measurement circuit after connecting a temporary resistor in a reactor fixed detector leakage current measurement method provided by the present invention. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0040] The present invention provides a method for measuring leakage current of a fixed vanadium detector in a reactor, comprising the following steps:

[0041] Step 1: Connect a known resistor in series in the detection circuit.

[0042] The circuit loop of the vanadium detector during normal operation is as follows: Figure 1 As shown, the actual current passing through the detector (I) D ) should be the detector current (I) A ) and leakage current (I L The sum of ) and the detector current (I) in the detector loop diagram L The detector resistance (R1) can be measured, due to the leakage current (I) L ) and leakage resistance (R L Since the leakage current cannot be directly measured, to solve for it, another known resistor R2 is temporarily connected in series in the detection circuit during the measurement. Figure 2 As shown.

[0043] Step 2: Calculate the leakage current and leakage correction factor of the vanadium detector during operation.

[0044] Depend on Figure 1 and Figure 2 The relationship between currents can be obtained as follows:

[0045] I L +I A =I D (1)

[0046] I' L ·+I B =I D (2)

[0047] In the formula:

[0048] I L Leakage current, an unknown quantity;

[0049] I A Detector current, known quantity (measured value);

[0050] I D Actual current, unknown quantity.

[0051] I L’ : Leakage current after the series resistor in the detection circuit, an unknown quantity;

[0052] I B: The detector current after the series resistor in the detection circuit, a known quantity (measured value).

[0053] Combining equations (1) and (2), we can obtain:

[0054] I' L · = I L +I A -I B (3)

[0055] According to Kirchhoff's voltage and current laws, the following formula is obtained:

[0056] I L ·R L =I A ·R1 (4)

[0057] I' L ·R L =I B ·(R1+R2) (5)

[0058] In the formula:

[0059] R L Leakage resistance, an unknown quantity;

[0060] R1: Detector resistance, a known quantity;

[0061] R2: Temporary connection resistor, known quantity.

[0062] Combining equations (3), (4), and (5), we obtain the detector leakage current:

[0063]

[0064] Define the leakage correction factor K A for:

[0065]

[0066] Combining equations (6) and (7), we obtain the leakage correction factor:

[0067]

[0068] Step 3: Statistical analysis of the leakage current correction factor range

[0069] When the reactor has power, leakage correction measurements are performed at <10%, 15%, 25%, 50%, 75%, and 100% rated power platforms for different units and cycles. The leakage correction factor measured by the detectors at different rated power is recorded. According to equation (8), the lower limit of the leakage correction factor is 1. The leakage correction factor values ​​of all detectors are compared, and the upper limit of the leakage correction factor (1+a) is statistically determined. Therefore, the leakage correction factor ranges from 1 to (1+a).

[0070] Step 4: Analyze whether the leakage current correction factor of the same detector changes with the random group, cycle, and power plateau.

[0071] Keeping all other inputs constant, only the detector current value is modified to simulate changes in the leakage correction factor. The sensitivity of power distribution measurements to the leakage correction factor is evaluated by comparing the impact of different leakage correction factors on the final measurement results. The specific steps are as follows:

[0072] Step 4.1: Confirm the original maximum negative deviation X0, the original maximum positive deviation Y0, the location of the core assembly containing the original maximum negative deviation, and the location of the core assembly containing the original maximum positive deviation.

[0073] The core power distribution was calculated based on data obtained from different power platforms to confirm the original maximum negative deviation X0, the original maximum positive deviation Y0, the location of the original maximum negative deviation in the core assembly, and the location of the original maximum positive deviation in the core assembly.

[0074] Step 4.2: Confirm the maximum negative deviation X1 and the maximum positive deviation Y1 of the measurement-prediction correction.

[0075] Keeping other inputs constant, multiplying the detector measurement currents at the core assembly location where the original maximum negative deviation is located and at adjacent locations by (1-a) yields the corrected maximum negative deviation X1 of the measurement-prediction value; multiplying the detector measurement currents at the core assembly location where the original maximum positive deviation is located and at adjacent locations by (1+a) yields the corrected maximum positive deviation Y1 of the measurement-prediction value. This increases the amount of deviation in the results while ensuring that the change in the leakage correction factor amplitude can encompass the range of change in the leakage correction factor.

[0076] Step 4.3: Confirm the impact of variations in the detector leakage correction factor within its distribution range on the results. Compare the maximum negative and maximum positive deviations calculated from the original and modified data, respectively. and This proves that the variation of the detector leakage correction factor within its distribution range has little impact on the results.

[0077] Step 5: Confirm the power platform and the number of measurements to be performed for the leakage correction factor measurement test.

[0078] Based on the above analysis, it is proven that the leakage correction factor distribution range between different power platforms is between 1 and (1+a), does not change with the power level, and has a negligible impact on the power distribution measurement results. To reduce the risk, the number of leakage current measurements on different power platforms can be reduced. Since the lower the power level, the lower the risk of measurement, only one low-power platform can be selected to carry out the leakage correction factor measurement test.

[0079] The embodiment takes the Sanmen Nuclear Power Plant during the first, second, and third cycles of Unit 1 and the first, second, and third cycles of Unit 2 as examples. It employs a method for measuring leakage current using a fixed vanadium detector within the reactor, as provided by this invention. The specific implementation steps are as follows:

[0080] Step 1: Apply temporary resistors to multiple power platforms respectively.

[0081] Step 2: Calculate the leakage current I of the vanadium detector under the given conditions according to formulas (6) and (8). L With leakage correction factor K A ;

[0082] Step 3: Statistical analysis of the leakage current correction factor range

[0083] Statistical analysis of leakage correction factors measured under different units, cycles, and power platforms determined that the leakage correction factors did not show significant differences due to different power levels, and that the leakage correction factors were distributed between 1.0000 and 1.0001, i.e., a = 0.0001. This proves that the leakage correction factors distributed between different power platforms are within the range of 1.0000 to 1.0001 and do not change with power level.

[0084] Step 4: Analyze whether the leakage current correction factor of the same detector changes with the random group, cycle, and power plateau.

[0085] Step 4.1: Statistically analyze the core power distribution data obtained from different power platforms, and confirm the maximum negative deviation of the measurement-prediction value X0 = -7.12%, the maximum positive deviation Y0 = +8.16%, the core assembly location of the maximum negative deviation M-03, and the core assembly location of the maximum positive deviation H-08.

[0086] Step 4.2: Keeping other inputs unchanged, multiply the detector measurement current at the core assembly location and adjacent locations where the maximum negative deviation is located by 0.9999, and multiply the detector measurement current at the core assembly location and adjacent locations where the maximum positive deviation is located by 1.0001. At this time, the maximum negative deviation of the measurement-prediction value X1 = -7.12% and the maximum positive deviation Y1 = +8.18%.

[0087] Step 4.3, according to All values ​​are much less than 0.01, proving that the variation of the detector leakage correction factor within the distribution range of 1.0000 to 1.0001 has little impact on the power distribution measurement results;

[0088] Step 5: After analyzing the results, it was confirmed that only one leakage correction factor measurement needs to be performed on the 15% rated power platform per cycle.

[0089] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. All contents not described in detail in the present invention can be derived from existing technologies.

Claims

1. A method for measuring leakage current of a fixed vanadium detector in a reactor, characterized in that, The method includes: Step 1: Connect a known resistor in series in the detection circuit; Step 2: Calculate the leakage current and leakage correction factor of the vanadium detector during operation; Step 3: Statistically analyze the range of leakage current correction factors; Step 4: Analyze whether the leakage current correction factor of the same detector changes with the random group, cycle, and power plateau. Step 5: Confirm the power platform and the number of measurements to be performed for the leakage correction factor measurement test.

2. The method for measuring leakage current of a fixed vanadium detector in a reactor according to claim 1, characterized in that, The formula for calculating the leakage current in step 2 is as follows: In the formula, I L Leakage current; I A : Detector current; R1: Detector resistance; I B : The detector current after the series resistor in the detection circuit; R2: Temporary connection resistor.

3. The method for measuring leakage current of a fixed vanadium detector in a reactor according to claim 2, characterized in that, The formula for calculating the leakage correction factor in step 2 is as follows: In the formula, K A Leakage correction factor.

4. The method for measuring leakage current of a fixed vanadium detector in a reactor according to claim 3, characterized in that, In step 3, the leakage correction factor ranges from 1 to (1+a), where...

5. A method for measuring leakage current of a fixed vanadium detector in a reactor according to claim 4, characterized in that, Step 4 includes: Step 4.1: Confirm the original maximum negative deviation X0, the original maximum positive deviation Y0, the location of the original maximum negative deviation in the reactor core assembly, and the location of the original maximum positive deviation in the reactor core assembly. Step 4.2: Confirm the maximum negative deviation X1 and the maximum positive deviation Y1 of the measurement-prediction value correction; Step 4.3: Confirm the impact of variations in the detector leakage correction factor within its distribution range on the results.

6. The method for measuring leakage current of a fixed vanadium detector in a reactor according to claim 5, characterized in that, In step 4.2, the maximum negative deviation X1 of the measurement-prediction value correction is: the detector measurement current at the core assembly position where the original maximum negative deviation is located and the adjacent position multiplied by (1-a); the maximum positive deviation Y1 of the measurement-prediction value correction is: the detector measurement current at the core assembly position where the original maximum positive deviation is located and the adjacent position multiplied by (1+a).

7. A method for measuring leakage current of a fixed vanadium detector in a reactor according to claim 6, characterized in that, In step 4.3, if and This proves that the variation of the detector leakage correction factor within its distribution range has little impact on the results.

8. A method for measuring leakage current of a fixed vanadium detector in a reactor according to claim 7, characterized in that, Step 5 specifically involves the following: Since the leakage correction factor does not change with the power level and its impact on the power distribution measurement results is negligible, the number of leakage current measurements on different power platforms should be reduced to lower the risk. Furthermore, since the lower the power level, the lower the risk of performing the measurement, a low-power platform should be selected to conduct the leakage correction factor measurement test.

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