A method for correcting fluid temperature in a reactor pressurizer spray line and its application

Abstract

The present invention provides a method for correcting the temperature of a fluid in a reactor pressurizer spray line and its application. The correction method performs linear fitting on the resistance value of a temperature measuring element and the measured value of the fluid temperature to obtain a gain bias algorithm formula. The measured value of the fluid temperature is corrected using the formula to obtain the actual value of the fluid temperature. The correction method is simple and highly accurate, and can guide an operator to promptly identify insufficient opening or abnormal closure conditions of a pressurizer bypass spray valve, thereby promptly regulating the pressurizer bypass spray valve, thereby having high value for promotion and use.

Description

Technical Field

[0001] The present invention relates to the field of measurement and control technology, and in particular to a method and application for correcting the temperature of a fluid in a spray line of a reactor pressurizer. Background Art

[0002] Three chip resistor temperature sensors were installed in the pressurizer spray lines of a certain type of nuclear power plant to measure the temperature of the fluid within the lines. Low-temperature alarms were set on the measurement channels of the three temperature sensors to alert operators in the main control room of insufficient flow through the pressurizer spray line bypass valve. The low-temperature alarm setpoint ensured that the minimum spray line temperature remained within the assumed envelope used in fatigue analysis of the pressurizer spray line and pressurizer nozzle.

[0003] Chip resistor temperature sensors cannot accurately reflect the temperature of the fluid within the pipeline due to differences in clearance, contact area, insulation covering the sensor, and ventilation conditions. During normal operation at a nuclear power plant, the pressurizer spray bypass valve remains open at a specified valve opening. However, if the chip resistor temperature sensor reading falls below the low alarm setting, a low-temperature alarm will be issued. When operators partially open the pressurizer main spray valve, increasing the amount of fluid in the pressurizer spray line, the chip resistor temperature sensor reading will still fall below the low alarm setting. This prevents operators from identifying the true status of the pressurizer bypass valve and making timely adjustments.

[0004] The current improvement approach at nuclear power plants involves measuring the difference between the temperature measured by a chip resistor temperature sensor during pressurizer spray at maximum flow and the primary circuit cold leg temperature. The new alarm value is then subtracted from the original low-temperature alarm value by the temperature difference. However, this method results in inconsistent alarm values for each unit, placing a burden on operators. Furthermore, the temperature sensor readings do not represent the actual fluid temperature. Under-temperature alarms can still be generated during unit operation under variable operating conditions, disrupting operator judgment.

[0005] CN105527038A discloses a platinum thermal resistor sensor error correction method and a heat meter using the method for temperature measurement. The platinum thermal resistor sensor error correction method includes obtaining the temperature range and accuracy of the platinum thermal resistor temperature sensor; calculating an error correction point; performing error correction on the platinum thermal resistor temperature sensor to obtain an average measurement temperature-correction compensation coefficient curve; selecting an error correction point as a basic temperature point; performing measurement correction on the platinum thermal resistor temperature sensor to be corrected at the basic temperature point; and performing temperature measurement error correction on the platinum thermal resistor temperature sensor to be corrected within the full temperature range.

[0006] CN112067166A discloses a calibration method for a thermal resistor, which includes: obtaining a working range temperature value corresponding to the thermal resistor and calculating a selected value in the working range temperature value; calculating the linearity and deviation value of the thermal resistor using the selected value, and outputting a qualified result of the thermal resistor when both the linearity and the deviation value meet corresponding preset requirements; when the linearity and the deviation value do not meet the corresponding preset requirements, obtaining the Gain and Offset coefficients of the thermal resistor, and correcting the Gain and Offset coefficients using a preset coefficient correction method.

[0007] However, the above correction method is relatively complicated and there is still a certain measurement error when measuring the fluid temperature in the reactor pressurizer spray line.

[0008] Therefore, it is of great significance to provide a method and application for correcting the fluid temperature in the spray line of a reactor pressurizer with a simple method and high accuracy. Summary of the Invention

[0009] To solve the above technical problems, the present invention provides a method and application for correcting the fluid temperature in a reactor pressurizer spray line, wherein the actual value of the fluid temperature in the pipeline is obtained by performing a proportional correction on the reading of a temperature measuring element; the correction method is simple, reliable, and has high promotion and utilization value.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a method for correcting the temperature of a fluid in a reactor pressurizer spray line, the correction method comprising the following steps:

[0012] (1) Obtain the resistance value of the temperature measuring element and the measured value of the fluid temperature, perform linear fitting, and obtain the gain bias algorithm formula F(x) = ax + b;

[0013] (2) Establishing a full spray operating condition for the pressurizer and obtaining the parameters a and b in the gain bias algorithm formula;

[0014] (3) The measured value of the fluid temperature is corrected using the gain bias algorithm formula to obtain the actual value of the fluid temperature.

[0015] During the operation of the reactor pressurizer spray pipeline, the inventor discovered that although the gap between the temperature measuring element and the pipeline, the different contact areas, the insulation installation covering the outside of the temperature measuring element, and the different ventilation conditions resulted in the measured value of the fluid temperature being unable to accurately reflect the temperature of the fluid in the pipeline, these conditions can be comprehensively evaluated as different total thermal resistances. The total thermal resistance at the installation position of each temperature measuring element remains unchanged due to the unchanged layout conditions, that is, there is a certain proportional relationship between the measured value and the actual value of the fluid temperature.

[0016] Therefore, the method for correcting the fluid temperature in the reactor pressurizer spray pipeline described in the present invention performs linear fitting on the resistance value of the temperature measuring element and the measured value of the fluid temperature to obtain a gain bias algorithm formula, and uses this formula to correct the measured value of the fluid temperature to obtain the actual value of the fluid temperature.

[0017] Preferably, the temperature measuring element in step (1) includes a chip resistance temperature measuring element.

[0018] Preferably, the temperature measuring element in step (1) is arranged on the spray line of the pressurizer.

[0019] Preferably, after obtaining the resistance value of the temperature measuring element and the measured value of the fluid temperature in step (1), a scatter plot is drawn and a linear fit is performed on the plot using a least squares method tool.

[0020] Preferably, the goodness of fit R of the linear fit in step (1) is 2 >0.95, for example, it can be 0.955, 0.96, 0.966, 0.97, 0.98, 0.99, 0.995 or 0.998, etc., but it is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0021] Preferably, in the gain bias algorithm formula F(x)=ax+b in step (1),

[0022]

[0023] Among them, T c is the median temperature of the primary coolant circuit of the reactor pressurizer cold pipe section;

[0024] T0: The lower limit temperature value measured by the temperature measuring element;

[0025] T1: The measured value of the fluid temperature before the temperature measuring element is corrected under the full spray condition of the stabilizer.

[0026] Preferably, the full spraying working condition of the pressurizer in step (2) includes that all the standby heaters of the pressurizer are put into operation and the main spraying valve of the pressurizer is opened to the corresponding opening state.

[0027] As a preferred technical solution of the present invention, the correction method includes the following steps:

[0028] (1) Obtain the resistance value of the temperature measuring element and the measured value of the fluid temperature, draw a scatter plot, and use the least squares method tool to perform linear fitting to obtain the gain bias algorithm formula F(x) = ax + b;

[0029] The temperature measuring element includes a patch resistance temperature measuring element arranged on the spray line of the stabilizer; the goodness of fit R of the linear fitting 2 >0.95;

[0030] In the gain bias algorithm formula F(x)=ax+b

[0031]

[0032] Among them, T c is the median temperature of the primary coolant circuit of the reactor pressurizer cold pipe section;

[0033] T0: The lower limit temperature of the temperature measuring element;

[0034] T1: The measured value of the fluid temperature before the temperature measuring element is corrected under the full spraying condition of the pressurizer;

[0035] (2) Put all the standby electric heaters of the pressurizer into operation, open the main spray valve of the pressurizer to the corresponding opening state, establish the full spray working condition of the pressurizer, and obtain the parameters a and b in the gain bias algorithm formula;

[0036] (3) The measured value of the fluid temperature is corrected using the gain bias algorithm formula.

[0037] In a second aspect, the present invention further provides a use of the method for correcting the temperature of the fluid in the spray line of the reactor pressurizer as described in the first aspect in a nuclear power plant reactor.

[0038] Preferably, the measured value of the fluid temperature is first renamed to a new mark point, and then the gain bias algorithm formula F(x)=ax+b is written into the power plant control system, the measured value of the fluid temperature is corrected to obtain the actual value of the fluid temperature, and transmitted to the operator screen.

[0039] Preferably, an alarm signal is issued when the actual value of the fluid temperature is lower than an alarm value.

[0040] Compared with the prior art, the present invention has at least the following beneficial effects:

[0041] (1) The method for correcting the fluid temperature in the reactor pressurizer spray line provided by the present invention utilizes the proportional relationship between the measured value and the actual value of the fluid temperature to derive a gain bias algorithm formula. The measured value of the fluid temperature is corrected according to the formula to obtain the actual value of the fluid temperature. This can guide the operator to promptly identify the insufficient opening or abnormal closing condition of the pressurizer bypass spray valve and promptly adjust the pressurizer bypass spray valve;

[0042] (2) The method for correcting the fluid temperature in the reactor pressurizer spray line provided by the present invention is simple and highly accurate, and has high promotion and utilization value. DETAILED DESCRIPTION

[0043] For the convenience of understanding the present invention, the present invention is given below with examples. It should be understood by those skilled in the art that the examples are only for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0044] The present invention is further described in detail below. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0045] As a specific embodiment of the present invention, a method for correcting the temperature of a fluid in a reactor pressurizer spray line is provided, the correction method comprising the following steps:

[0046] (1) Obtain the resistance value of the temperature measuring element and the measured value of the fluid temperature, draw a scatter plot, and use the least squares method tool to perform linear fitting to obtain the gain bias algorithm formula F(x) = ax + b;

[0047] The temperature measuring element includes a patch resistance temperature measuring element arranged in the spray line of the stabilizer; the goodness of fit R of the linear fitting 2 is 0.9997;

[0048] In the gain bias algorithm formula F(x)=ax+b

[0049]

[0050] Among them, T c is the median temperature of the primary coolant circuit of the reactor pressurizer cold pipe section;

[0051] T0: The lower limit temperature of the temperature measuring element;

[0052] T1: The measured value of the fluid temperature before the temperature measuring element is corrected under the full spraying condition of the pressurizer;

[0053] (2) Put all the backup electric heaters of the pressurizer into operation, open the main spray valve of the pressurizer to the corresponding opening state, and establish the full spray working condition of the pressurizer.

[0054] Under this working condition, the spray flow reaches its maximum value, and the heat dissipation of the pipe before the measuring point can be ignored. At this time, the test condition is obtained that the temperature of the inner wall of the measuring point is consistent with that of the cold pipe section. At this time, the actual temperature difference between the inner wall temperature of the pipe and the outer wall temperature can be measured. By measuring the actual temperature difference, T1 is obtained, and T is obtained by reading the cold pipe section temperature. c , and knowing that 37.8℃ is T0, substitute

[0055] Determine the parameters a and b in the gain bias algorithm formula;

[0056] Take a correction job as an example:

[0057] Under the condition of 37.8℃ water temperature, the temperature of the SMD resistor temperature measuring element was also 37.8℃, so T0 was calibrated to 37.8℃ (which is also the starting point of the calibration curve). After the unit was up to full power operation for more than 24 hours, the plan was arranged to carry out all the operation of the stabilizer electric heater to meet the test conditions. In this test, the temperature of the cold pipe section was measured to be 279.6℃ and stable, so T c After the full spray test conditions are met, the temperature T1 of the measuring point of the SMD resistor temperature measuring element is 274.7°C.

[0058]

[0059]

[0060] (3) The measured value of the fluid temperature is corrected using the gain bias algorithm formula.

[0061] This specific embodiment also provides a use of the above-mentioned method for correcting the temperature of the fluid in the spray line of the reactor pressurizer in a nuclear power plant reactor.

[0062] First, the measured value of the fluid temperature is renamed to a new mark point. Then, the gain bias algorithm formula F(x) = ax + b is written into the power plant control system. The measured value of the fluid temperature is corrected to obtain the actual value of the fluid temperature and transmitted to the operator screen.

[0063] If the actual value of the fluid temperature is lower than the alarm value, an alarm signal is issued.

[0064] In summary, the method for correcting the fluid temperature in the reactor pressurizer spray pipeline provided by the present invention utilizes the proportional relationship between the measured value and the actual value of the fluid temperature to derive a gain bias algorithm formula, and the measured value of the fluid temperature is corrected according to the formula to obtain the actual value of the fluid temperature; the correction method is simple and highly accurate, and can be applied to the regulation of the reactor pressurizer spray pipeline of a nuclear power plant.

[0065] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for correcting the fluid temperature in a reactor pressurizer spray line, characterized in that: The calibration method comprises the following steps: (1) After obtaining the resistance value of the temperature measuring element and the measured value of the fluid temperature, a scatter plot is drawn and a linear fit is performed on the temperature measuring element using a least squares method tool to obtain a gain bias algorithm formula F(x)=ax+b; the temperature measuring element is set on the spray line of the stabilizer; Among them, T c is the median temperature of the primary coolant circuit of the reactor pressurizer cold pipe section; T0: The lower limit temperature value measured by the temperature measuring element; T1: The measured value of the fluid temperature before the temperature measuring element is corrected under the full spraying condition of the pressurizer; (2) Establishing a full spray operating condition for the pressurizer and obtaining the parameters a and b in the gain bias algorithm formula; (3) The measured value of the fluid temperature is corrected using the gain bias algorithm formula to obtain the actual value of the fluid temperature.

2. The calibration method according to claim 1, wherein: The temperature measuring element in step (1) includes a chip resistance temperature measuring element.

3. The calibration method according to claim 1, wherein: The goodness of fit R of the linear fit in step (1) 2 >0.

95.

4. The calibration method according to claim 1, wherein: The full spraying working condition of the pressurizer in step (2) includes that all the standby heaters of the pressurizer are put into operation and the main spraying valve of the pressurizer is opened to the corresponding opening state.

5. Use of the method for correcting the temperature of the fluid in the spray line of a reactor pressurizer according to any one of claims 1 to 4 in a reactor of a nuclear power plant.

6. The use according to claim 5, characterized in that First, the measured value of the fluid temperature is renamed to a new mark point. Then, the gain bias algorithm formula F(x) = ax + b is written into the power plant control system. The measured value of the fluid temperature is corrected to obtain the actual value of the fluid temperature and transmitted to the operator screen.

7. The use according to claim 6, characterized in that If the actual value of the fluid temperature is lower than the alarm value, an alarm signal is issued.

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