A temperature measurement correction method for a primary loop pipe of a nuclear power plant
By adjusting the GD calibration function and the gain coefficient of the primary loop temperature difference ΔT, the problem of inaccurate measurement signals in the primary loop main pipeline temperature measurement of nuclear power plants after equipment replacement or overhaul was solved, ensuring the accuracy and safety of the measurement signals, and is applicable to Hualong One units.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CNNC FUJIAN FUQING NUCLEAR POWER
- Filing Date
- 2023-11-20
- Publication Date
- 2026-06-09
AI Technical Summary
In the temperature measurement of the primary loop main pipeline in a nuclear power plant, after the replacement of thermometer equipment or the refueling and overhaul of the unit, the previously determined temperature instrument GD calibration function and the primary loop temperature difference ΔT gain coefficient can no longer accurately reflect the unit's power level, resulting in inaccurate measurement signals and affecting safety.
A method for correcting the temperature measurement of the primary loop main pipeline in a nuclear power plant is provided. By adjusting the GD calibration function and the primary loop temperature difference ΔT gain coefficient, and based on the latest instrument manufacturer calibration data and core temperature distribution, the calibration function and gain coefficient of the temperature instrument are recalibrated to ensure the accuracy and safety of the measurement signal.
It enables accurate reflection of the unit's power level after the replacement of thermometer equipment or after a major overhaul of the unit's refueling, improving the accuracy and safety of the primary loop temperature measurement signal and temperature difference signal, and is suitable for Hualong One units.
Smart Images
Figure CN117727477B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of nuclear power plant maintenance technology, specifically relating to a method for correcting the temperature measurement of the primary loop main pipeline in a nuclear power plant. Background Technology
[0002] Fuqing Units 5 and 6 are Hualong One reactors. Their reactor coolant system design includes three loops in the primary loop. Each loop is equipped with two narrow-range cold-section thermometers and four narrow-range hot-section thermometers, all measured using platinum resistance thermometers. The temperature signals from the cold and hot sections of the primary loop main piping of the RCS system directly participate in safety shutdown functions such as over-temperature and over-power tests, and are considered important safety protection parameters.
[0003] To improve the accuracy of temperature measurement channels and ensure the accuracy of measurement signals, the reactor coolant system design incorporates GD calibration functions for individual temperature signals in the narrow-range hot and cold sections. After the raw temperature signals are acquired and processed in the DCS cabinet, the individual temperature signals are calibrated using the GD function in the DCS software, based on calibration data provided by the thermometer manufacturer. Specifically, due to the influence of thermal stratification in the main pipeline, the calibration of the narrow-range hot section temperature signal requires not only the calibration data provided by the thermometer manufacturer but also calibration based on temperature data measured on different platforms during the commissioning phase. Furthermore, to ensure that the primary loop temperature difference signal accurately reflects the unit's power level, a ΔT gain coefficient adjustment module is implemented for the primary loop hot and cold section temperature difference signal.
[0004] The aforementioned single-instrument temperature GD calibration function and primary loop temperature difference ΔT gain coefficient were determined during unit commissioning through reactor coolant temperature measurement channel calibration tests and main pipe thermal stratification tests. During subsequent unit operation and maintenance, such as after thermometer equipment replacement or refueling overhauls, the previously determined temperature instrument GD calibration function and primary loop temperature difference ΔT gain coefficient need to be revised based on the latest instrument manufacturer calibration data and core temperature distribution. Furthermore, after commercial operation, the unit will not have the conditions to perform main pipe thermal stratification tests and reactor coolant temperature measurement channel calibration tests.
[0005] Therefore, there is an urgent need to develop a method for correcting the temperature measurement of the primary loop main pipeline in nuclear power plants. This method would allow maintenance personnel to easily perform on-site corrections of the GD calibration function of the primary loop main pipeline temperature instrument and the gain coefficient of the primary loop temperature difference ΔT after the replacement of thermometer equipment or refueling overhaul of the unit. This would ensure the accuracy of the temperature signal of the primary loop main pipeline and the safety of the unit. Summary of the Invention
[0006] The purpose of this invention is to provide a method for correcting the temperature measurement of the primary loop main pipeline in a nuclear power plant. This method can correct the previously determined temperature instrument GD calibration function and the primary loop temperature difference ΔT gain coefficient based on the latest instrument manufacturer calibration data and core temperature distribution during the operation and maintenance of the nuclear power unit (such as after the replacement of thermometer equipment or after the unit refueling overhaul). This ensures the accuracy and safety of the primary loop temperature measurement signal and temperature difference signal, and enables it to accurately reflect the unit's power level.
[0007] Technical solution to achieve the purpose of this invention:
[0008] A method for correcting the temperature measurement of the primary loop main pipeline in a nuclear power plant, the method comprising:
[0009] Step (1), correction of the primary loop temperature measurement calibration function;
[0010] Step (2): Correction of the gain coefficient of the temperature difference ΔT between the hot and cold sections of the primary loop.
[0011] Step (1) includes the correction of the primary loop temperature measurement calibration function during the unit operation phase and the unit maintenance phase.
[0012] The correction of the primary loop temperature measurement calibration function during the unit operation phase includes: confirming whether the thermometer signal is malfunctioning; if the thermometer signal is malfunctioning, the abnormal signal is removed; if the thermometer signal is not malfunctioning, but the temperature signal is abnormal and has a deviation, the reading of the abnormal signal is adjusted to the normal value by adjusting the GD calibration function.
[0013] If the thermometer signal is not faulty, but the temperature signal is abnormally biased, adjusting the reading of the abnormal signal to the normal value by adjusting the GD calibration function includes:
[0014] Using the average value of the valid signals at the same location in the same loop as a benchmark, the readings of abnormal signals are adjusted to normal values by adjusting the GD calibration function;
[0015] If both narrow-range thermometers in the same loop cold section have abnormal deviations, the average value of the four narrow-range thermometers in the other two loop cold sections is taken as the benchmark, and the readings of the abnormal signals are adjusted to normal values by adjusting the GD calibration function.
[0016] The correction of the primary loop temperature measurement calibration function during the unit overhaul phase includes:
[0017] Confirm whether the thermometer has been replaced. If the thermometer has been replaced, recalculate and adjust it according to the thermometer calibration data provided by the manufacturer. If the adjusted temperature signal still deviates from the signal of the thermometer in the loop that has not been replaced, or if the signals of the two narrow-range thermometers in the cold section of the same loop both have abnormal deviations, adjust the temperature signal with the deviation to the normal value by adjusting the GD calibration function.
[0018] If the thermometer has not been replaced, and the temperature signal deviation is caused by the change in core power distribution during the unit refueling overhaul, the average value of the effective signal of the unbiased thermometer in that loop will be used as the benchmark to recalculate the calibration function. The deviation temperature signal will be adjusted to the normal value by adjusting the GD calibration function.
[0019] If the adjusted temperature signal still deviates from the signal of the unreplaced thermometer in the loop, or if both narrow-range thermometers in the cold section of the same loop exhibit abnormal deviations, the temperature signal is adjusted to a normal value by adjusting the GD calibration function. Specifically: If the temperature signal still deviates from the signal of the unreplaced thermometer in the loop, the average value of the effective signals from the unreplaced thermometers in the loop is used as a benchmark to recalculate the calibration function, and the temperature signal is adjusted to a normal value by adjusting the GD calibration function; If both narrow-range thermometers in the cold section of a loop have been replaced, and a deviation still exists after readjustment based on the thermometer calibration curve provided by the manufacturer, the average value of the two narrow-range thermometers is used as a benchmark, and the temperature signal is adjusted to a normal value by adjusting the GD calibration function.
[0020] When the temperature signal of the narrow-range thermometer in the primary loop deviates from the signals of the other thermometers in the loop, the average value of the effective signal of the unbiased thermometer in the loop is used as the reference. After the temperature of the primary loop of the unit rises into the temperature measurement range, the values of all thermometers in the loop after the GD calibration function are read simultaneously in the DCS system. The average value of the GD calibration function of the unbiased thermometer signal is calculated. The difference (C) between the value of the GD calibration function of the biased thermometer and this average value is calculated. The GD calibration function of the biased thermometer is f(x) = Ax + B. Then the corrected GD calibration function is f(x) = Ax + BC.
[0021] If there is a deviation between two narrow-range thermometers in the cold section of a certain loop in the primary circuit, the average value of the two narrow-range thermometers is taken as the benchmark. After the temperature of the primary circuit of the unit rises into the temperature measurement range, the values of the two narrow-range thermometers after the GD calibration function are read simultaneously in the DCS system. The average value of the values after the GD calibration function of the two narrow-range thermometers is calculated, and the difference (C') between the values after the GD calibration function of the two narrow-range thermometers and this average value is calculated. The GD calibration function of the two narrow-range thermometers is f(x) = A'x + B'. Then the corrected GD calibration function is f(x) = A'x + B' - C'.
[0022] Step (2) includes: during the commissioning phase of the unit, adjusting and confirming the gain coefficient according to the calibration test requirements of the reactor coolant temperature measurement channel; during the operation and maintenance phase of the unit, the unit needs to periodically check the temperature difference ΔT gain coefficient calibration module of the hot and cold sections in each refueling cycle. If the calibration coefficient determined in the previous operating cycle cannot fully match the temperature distribution after refueling, and if the condition exceeds the criteria, the ΔT gain coefficient adjustment module needs to be corrected.
[0023] The beneficial technical effects of this invention are as follows:
[0024] 1. The present invention provides a method for correcting the temperature measurement of the primary loop main pipeline in a nuclear power plant. This method can correct the previously determined temperature instrument GD calibration function and the primary loop temperature difference ΔT gain coefficient based on the latest instrument manufacturer calibration data and core temperature distribution during the operation and maintenance of the nuclear power unit (such as after the replacement of thermometer equipment or after the unit refueling overhaul). This improves the accuracy and safety of the primary loop temperature measurement signal and temperature difference signal, enabling it to accurately reflect the unit's power level.
[0025] 2. The method for temperature measurement correction of the primary loop main pipeline in a nuclear power plant provided by this invention is applicable to the Hualong One unit and is worth promoting and using. Attached Figure Description
[0026] Figure 1 A flowchart for correcting the calibration function of primary loop temperature measurement in a nuclear power plant, provided by the present invention;
[0027] In the diagram: A: Primary loop temperature measurement calibration function correction process; B: Unit operation phase; C: Unit maintenance phase; D: Whether the thermometer signal is faulty; E: Whether the thermometer has been replaced; F: Whether there is a deviation between the two narrow-range thermometers in the same loop and the thermometers in the other two loops; G: Recalculate and adjust the GD calibration function based on the thermometer calibration data provided by the manufacturer; H: Whether there is a deviation between the temperature signal and the signal from the thermometer that has not been replaced; I: Whether there is a deviation between the temperature signal and the temperature signal in the same loop; J: Perform temperature signal rejection; K: Adjust the GD calibration function based on the average value of the effective temperature signal at the same location in the same loop; L: Adjust the GD calibration function based on the average value of the four narrow-range thermometer signals in the cold section of the other two loops; M: Work completed. Detailed Implementation
[0028] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.
[0029] This invention provides a method for correcting the temperature measurement of the primary loop main pipeline in a nuclear power plant, comprising:
[0030] Step (1) Correction of primary loop temperature measurement calibration function
[0031] like Figure 1 As shown, the specific steps of the primary loop temperature measurement calibration function correction process include:
[0032] Step (1.1): When the unit experiences a thermometer signal abnormality or failure during operation, the primary loop temperature measurement calibration function correction method is as follows:
[0033] Step (1.1.1): If it is confirmed that this temperature signal is invalid, the abnormal signal will be removed and will no longer participate in subsequent protection and control functions.
[0034] Step (1.1.2): Confirm that the thermometer signal is not faulty. If the temperature signal is abnormal and has a deviation, then use the average value of the valid signal at the same position in the same loop as the benchmark, and adjust the reading of the abnormal signal to the normal value by adjusting the GD calibration function.
[0035] Step (1.1.3): Confirm that the thermometer signal is not invalid. If both narrow-range thermometer signals in the same loop cold section have abnormal deviations, take the average value of the four narrow-range thermometer signals in the other two loop cold sections as the benchmark, and adjust the reading of the abnormal signal to the normal value by adjusting the GD calibration function.
[0036] Step (1.2): When the thermometer is replaced during the unit's maintenance phase, the primary loop temperature measurement calibration function correction method is as follows:
[0037] Step (1.2.1): Recalculate the calibration function based on the thermometer calibration data provided by the manufacturer, and use DCS software to adjust the GD calibration function to complete the correction of the corresponding temperature signal of the replaced thermometer.
[0038] Step (1.2.2): During the unit's uplink, if the narrow-range thermometer in the primary loop main pipeline enters the range, and the replaced thermometer is readjusted according to the thermometer calibration data provided by the manufacturer, if the adjusted temperature signal still deviates from the signal of the unreplaced thermometer in the loop, the calibration function is recalculated based on the average value of the effective signal of the unreplaced thermometer in the loop. The deviated temperature signal is adjusted to the normal value by adjusting the GD calibration function.
[0039] Step (1.2.3): When there are no thermometers to replace in the narrow range of the primary loop, but the temperature signal deviation is caused by the change in the core power distribution due to the refueling overhaul of the unit, the average value of the effective signal of the unbiased thermometer in the loop is used as the benchmark to recalculate the calibration function. The deviation temperature signal is adjusted to the normal value by adjusting the GD calibration function.
[0040] Step (1.2.4): When both narrow-range thermometers in the cold section of a loop are replaced, and there is still a deviation after readjustment according to the thermometer calibration curve provided by the manufacturer, the average value of the two narrow-range thermometers is taken as the benchmark, and the temperature signal with deviation is adjusted to the normal value by adjusting the GD calibration function.
[0041] Step (2), Correction of gain coefficient for temperature difference ΔT between hot and cold sections of primary loop
[0042] According to the design requirements of the reactor coolant system, in order to ensure that the temperature difference between the hot and cold sections of the reactor coolant can accurately reflect the power level of the unit, the hot and cold section temperature difference signal is equipped with a ΔT gain coefficient calibration module. The deviation between the output value after calibration and the rated value should not exceed 0.5℃.
[0043] During the commissioning phase, the gain coefficient must be adjusted and confirmed strictly in accordance with the calibration test requirements for the reactor coolant temperature measurement channel. At the same time, during the operation and maintenance phase, according to the "Technical Requirements for Periodic Testing of Reactor Coolant Systems", the unit must periodically check the temperature difference ΔT calibration module of the hot and cold sections during each refueling cycle. The main reason is that after the core refueling, the core power distribution changes, and the calibration coefficient determined in the previous operating cycle cannot fully match the temperature distribution after refueling. If the condition exceeds the criteria, the ΔT gain coefficient adjustment module needs to be corrected.
[0044] Therefore, during each refueling cycle, when the unit ascends to 75% power, after the RNI core power range parameter is corrected, the ΔT gain coefficient adjustment module is periodically checked. (Based on the trend analysis of the thermal power values of each loop and the average core nuclear power (RNI001VE) during the current power increase period, the upper limit of the cold and hot section temperature difference ΔT when the unit reaches the full power platform does not exceed 102%FP). If there is a risk of exceeding the limit, the ΔT gain coefficient is adjusted at the corresponding power platform, and ultimately the output of the ΔT gain coefficient adjustment module is ensured to meet the requirements (the upper limit of the cold and hot section temperature difference ΔT does not exceed 102%FP) when the unit reaches 100% power.
[0045] Specific adjustment method: On the unit's stable power platform, calculate the average thermal power within 20 minutes based on the results of the physical thermal balance test, and at the same time calculate the average temperature difference between the hot and cold sections of the deviation loop during the same time period. Calculate the calibration gain coefficient based on the current actual thermal power / loop temperature difference, and complete the correction of the channel ΔT calibration module gain coefficient based on the calibration gain coefficient.
[0046] Example 1: Correction of the primary loop temperature measurement calibration function
[0047] 1) Each single-loop thermometer's factory test report includes thermometer calibration data, which is used to fit and calculate the calibration function on-site.
[0048] 2) When the temperature signal of the narrow-range thermometer in the first loop deviates from the signals of the other thermometers in the loop, the average value of the effective signal of the unbiased thermometer in the loop is used as the reference. After the unit's first loop temperature rises into the temperature measurement range, the GD calibration function values of all thermometers in the loop are read simultaneously in the DCS system. The average value of the GD calibration function value of the unbiased thermometer signal is calculated. The difference (C) between the GD calibration function value of the biased thermometer and this average value is calculated. The GD calibration function of the biased thermometer is f(x) = Ax + B. Then the corrected GD calibration function is f(x) = Ax + BC.
[0049] 3) If there is a deviation between two narrow-range thermometers in the cold section of a certain loop in the primary circuit, the average value of the two narrow-range thermometers is taken as the benchmark. After the temperature of the primary circuit of the unit rises into the temperature measurement range, the values of the two narrow-range thermometers after the GD calibration function are read simultaneously in the DCS system. The average value of the values after the GD calibration function of the two narrow-range thermometers is calculated. The difference (C') between the values after the GD calibration function of the two narrow-range thermometers and this average value is calculated. The GD calibration function of the two narrow-range thermometers is f(x) = A'x + B'. Then the corrected GD calibration function is f(x) = A'x + B' - C'.
[0050] 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 correcting the temperature measurement of the primary loop main pipeline in a nuclear power plant, characterized in that, The method includes: Step (1), correction of the primary loop temperature measurement calibration function; Step (2), correction of the gain coefficient of the temperature difference ΔT between the hot and cold sections of the primary loop; Step (1) includes the correction of the primary loop temperature measurement calibration function during the unit operation phase and the unit maintenance phase. The correction of the primary loop temperature measurement calibration function during the unit operation phase includes: confirming whether the thermometer signal is malfunctioning; if the thermometer signal is malfunctioning, the abnormal signal is removed; if the thermometer signal is not malfunctioning, but the temperature signal is abnormal and has a deviation, the reading of the abnormal signal is adjusted to the normal value by adjusting the GD calibration function. If the thermometer signal is not faulty, but the temperature signal is abnormally biased, adjusting the reading of the abnormal signal to the normal value by adjusting the GD calibration function includes: Using the average value of the valid signals at the same location in the same loop as a benchmark, the readings of abnormal signals are adjusted to normal values by adjusting the GD calibration function; When both narrow-range thermometers in the same loop cold section have abnormal deviations, the average value of the four narrow-range thermometers in the other two loop cold sections is taken as the benchmark, and the readings of the abnormal signals are adjusted to normal values by adjusting the GD calibration function. The correction of the primary loop temperature measurement calibration function during the unit overhaul phase includes: Confirm whether the thermometer has been replaced. If the thermometer has been replaced, recalculate and adjust it according to the thermometer calibration data provided by the manufacturer. If the adjusted temperature signal still deviates from the signal of the thermometer in the loop that has not been replaced, or if the signals of the two narrow-range thermometers in the cold section of the same loop both have abnormal deviations, adjust the temperature signal with the deviation to the normal value by adjusting the GD calibration function. If the thermometer has not been replaced, and the temperature signal deviation is caused by the change in core power distribution during the unit refueling overhaul, the average value of the effective signal of the unbiased thermometer in this loop will be used as the benchmark to recalculate the calibration function. The deviation temperature signal will be adjusted to the normal value by adjusting the GD calibration function. Step (2) includes: during the commissioning phase of the unit, adjusting and confirming the gain coefficient according to the requirements of the reactor coolant temperature measurement channel calibration test; during the operation and maintenance phase of the unit, the unit needs to periodically check the temperature difference ΔT gain coefficient calibration module of the hot and cold sections in each refueling cycle. If the calibration coefficient determined in the previous operating cycle cannot fully match the temperature distribution after refueling, and if the condition exceeds the criteria, the ΔT gain coefficient adjustment module needs to be corrected.
2. The method for correcting the temperature measurement of the primary loop main pipeline in a nuclear power plant according to claim 1, characterized in that, If the adjusted temperature signal still deviates from the signal of the unreplaced thermometer in the loop, or if both narrow-range thermometers in the cold section of the same loop exhibit abnormal deviations, the temperature signal is adjusted to a normal value by adjusting the GD calibration function. Specifically: If the temperature signal still deviates from the signal of the unreplaced thermometer in the loop, the average value of the effective signals from the unreplaced thermometers in the loop is used as a benchmark to recalculate the calibration function, and the temperature signal is adjusted to a normal value by adjusting the GD calibration function; If both narrow-range thermometers in the cold section of a loop have been replaced, and a deviation still exists after readjustment based on the thermometer calibration curve provided by the manufacturer, the average value of the two narrow-range thermometers is used as a benchmark, and the temperature signal is adjusted to a normal value by adjusting the GD calibration function.
3. A method for correcting the temperature measurement of the primary loop main pipeline in a nuclear power plant according to claim 1 or 2, characterized in that, When the temperature signal of the narrow-range thermometer in the primary loop deviates from the signals of the other thermometers in the loop, the average value of the effective signal of the unbiased thermometer in the loop is used as the reference. After the temperature of the primary loop of the unit rises into the temperature measurement range, the values of all thermometers in the loop after the GD calibration function are read simultaneously in the DCS system. The average value of the unbiased thermometer signal after the GD calibration function is calculated. The difference C between the value of the biased thermometer after the GD calibration function and this average value is calculated. The biased thermometer GD calibration function is f(x) = Ax + B. Then the corrected GD calibration function is f(x) = Ax + BC.
4. A method for correcting the temperature measurement of the primary loop main pipeline in a nuclear power plant according to claim 1 or 2, characterized in that, If there is a deviation between two narrow-range thermometers in the cold section of a certain loop in the primary circuit, the average value of the two narrow-range thermometers is taken as the benchmark. After the temperature of the primary circuit of the unit rises into the temperature measurement range, the values of the two narrow-range thermometers after the GD calibration function are read simultaneously in the DCS system. The average value of the values after the GD calibration function of the two narrow-range thermometers is calculated. The difference C' between the values after the GD calibration function of the two narrow-range thermometers and this average value is calculated. The GD calibration function of the two narrow-range thermometers is f(x)=A'x+B'. Then the corrected GD calibration function is f(x)=A'x+B'-C'.