Nuclear power calibration method considering quadrant power tilt

Abstract

The present application belongs to the technical field of nuclear power calibration of nuclear power unit, and particularly relates to a nuclear power calibration method considering quadrant power tilt, comprising the following steps: step 1, carrying out heat balance measurement to obtain the core power; step 2, obtaining the quadrant power tilt coefficient according to the core measurement system; step 3, obtaining the quadrant power of four quadrants according to the core power and the quadrant power tilt coefficient; and step 4, calibrating the nuclear power of the corresponding channel according to the quadrant power of the four quadrants. The present application uses the quadrant power tilt coefficient measured by the online core measurement system to calculate the real quadrant power corresponding to the out-of-core detector, uses the real quadrant power to calibrate the nuclear power, and obtains the real power coefficient, which can more finely represent the real situation of the core and effectively improve the accuracy of the nuclear power.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power calibration technology for nuclear power units, and specifically relates to a nuclear power calibration method that takes into account quadrant power tilt. Background Technology

[0002] A typical pressurized water reactor nuclear power plant's instrumentation system has four power range detectors. These detectors measure the neutron flux in the reactor core and generate current signals, which are then multiplied by a corresponding coefficient within the control cabinet to obtain the nuclear power. At the same power level, as reactor burnup increases, the rated neutron flux continuously rises, leading to a corresponding increase in the relative power of peripheral components near the detectors, resulting in a larger current signal. Therefore, the nuclear power of the instrumentation system needs to be checked and calibrated regularly, typically through weekly heat balance measurements, monthly power distribution measurements, and quarterly power range coefficient calibrations.

[0003] Based on traditional offline core measurement systems, the quadrant power tilt ratio needs to be obtained during power distribution measurements, which are performed monthly, failing to meet the weekly nuclear power calibration requirement. Therefore, traditional nuclear power calibration methods do not consider quadrant power tilt, directly calibrating the nuclear power of the four channels of the nuclear instrumentation system to the reference power of the entire core. The quadrant power tilt ratio calculated using the calibrated nuclear power consistently yields a result of 1.0, which is inconsistent with reality. Therefore, the quadrant power tilt ratio cannot be calculated using nuclear power; it must be replaced by the larger of the ratio of the maximum to the average value of the calibration outputs from either the upper half of the external neutron detectors or the lower half.

[0004] According to the Operating Technical Specifications document in the license, if the quadrant power tilt ratio is not within the limit, the required measure is to reduce the thermal power by at least 3% FP for every 1% of the quadrant power tilt ratio exceeding 1.00.

[0005] Therefore, it is necessary to design a more accurate method for nuclear power calibration. Summary of the Invention

[0006] The purpose of this invention is to provide a nuclear power calibration method that takes into account quadrant power tilt. This method uses the quadrant power tilt coefficient measured by an online core measurement system to calculate the true quadrant power corresponding to the external detector, and uses the true quadrant power to calibrate the nuclear power to obtain the true power coefficient. This method can more accurately characterize the true state of the core and effectively improve the accuracy of nuclear power.

[0007] Technical solution to achieve the purpose of this invention:

[0008] A method for nuclear power calibration that takes into account quadrant power tilt includes:

[0009] Step 1: Conduct thermal balance measurements to obtain core power;

[0010] Step 2: Obtain the quadrant power tilt coefficient based on the core measurement system;

[0011] Step 3: Based on the core power and quadrant power tilt coefficient, obtain the quadrant power of the four quadrants;

[0012] Step 4: Calibrate the core power of the corresponding channel based on the quadrant power of the four quadrants.

[0013] Step 1 includes: conducting heat balance measurement under stable unit power conditions, subtracting the heat power of other heat sources in the primary loop from the heat power measured by high-precision thermal instruments in the secondary loop to obtain the accurate core power; the determination of reactor heat power in the heat balance measurement test is based on the enthalpy balance of each steam generator, that is: heat power transferred from the primary side of the steam generator to the secondary side = heat power of wet steam at the steam generator outlet - heat power of main feedwater + heat power of blowdown.

[0014] The formula for calculating the core power in step 1 is as follows:

[0015]

[0016] in,

[0017] W R —Core power, MW;

[0018] W SG —The thermal power provided by each steam generator, in MW;

[0019] —The thermal power input to the reactor coolant system from heat sources other than the reactor core, in MW;

[0020] Q e —Water supply flow rate, kg / s;

[0021] Q p —Sewage discharge flow rate, kg / s;

[0022] Q v —Wet steam flow rate, kg / s;

[0023] H e —Water enthalpy, kJ / kg;

[0024] H p —Enthalpy of discharged wastewater, kJ / kg;

[0025] H v —Enthalpy of wet steam at the steam generator outlet, kJ / kg.

[0026] Step 2 includes: the core measurement system arranges multiple core neutron flux measurement channels along the core radial direction, and each measurement channel arranges multiple self-powered detectors (SPNDs) at equal intervals along the height of the active section of the core; under normal operating conditions, the system continuously acquires current signals from each fixed SPND; combined with the power plant operating condition signals from the DCS, the system processes the signals in the control cabinet and provides the three-dimensional power distribution of the fuel assemblies in real time, obtaining the assembly power in the four quadrants of the core; based on the assembly power, the quadrant power tilt coefficient is calculated;

[0027] The formula for calculating the quadrant power tilt coefficient is:

[0028]

[0029] Among them, Q i This represents the quadrant power tilt coefficient in the i-th quadrant; i = 1, 2, 3, 4, representing the four quadrant power range measurement channels; P i This represents the average power of components within the i-th quadrant.

[0030] The formula for calculating quadrant power in step 3 is as follows:

[0031] W i =W R ×Q i

[0032] Among them, W i W represents the quadrant power in the i-th quadrant; R Q represents the core power; i This represents the quadrant power tilt coefficient for the i-th quadrant.

[0033] Step 4 includes: collecting the core power of four power ranges during the thermal balance measurement, averaging the core power of each power range as the core power of that channel; calculating the deviation between the core power of the channel and the quadrant power of the corresponding quadrant, and determining whether the core power needs to be calibrated based on the deviation calculation result; if the core power needs to be calibrated, calculating the current-power conversion coefficient of each calibrated channel according to the calibration coefficient correction formula; and obtaining the calibrated core power of the corresponding channel through the current-power conversion coefficient of each calibrated channel.

[0034] In step 4, the correspondence between channels and quadrants is as follows: channel 1 corresponds to quadrant 4, channel 2 corresponds to quadrant 2, channel 3 corresponds to quadrant 3, and channel 4 corresponds to quadrant 1.

[0035] In step 4, when the core power P of the channel Ri Quadrant power W corresponding to the quadrant i When the deviation exceeds 1.5%FP, the nuclear power needs to be calibrated.

[0036] In step 4, the calibration coefficient correction formula for each channel is as follows:

[0037] Channel 1:

[0038] Channel 2:

[0039] Channel 3:

[0040] Channel 4:

[0041] Where i = 1, 2, 3, 4, represents the four quadrant power range measurement channels; P Ri (i = 1, 2, 3, 4) represents the core power of the i-th channel; W i (i = 1, 2, 3, 4) represents the quadrant power in the i-th quadrant; K i (i = 1, 2, 3, 4) represents the current-to-power conversion coefficient of the ith channel after calibration; K 0i (i = 1, 2, 3, 4) represents the current-power conversion coefficient of the i-th channel before calibration.

[0042] The beneficial technical effects of this invention are as follows:

[0043] 1. This invention provides a nuclear power calibration method that considers quadrant power tilt, enabling the nuclear power of the four channels to be calibrated to the thermal power of their respective quadrants. Compared to uniform calibration to the core thermal power, this method provides a more precise characterization of the actual core situation. Using the calibrated nuclear power in unit protection is a safety-oriented approach.

[0044] 2. The present invention provides a nuclear power calibration method that takes into account quadrant power tilt. In the event of a core measurement system failure, the quadrant power tilt ratio (QPTR) can be replaced by the ratio of the maximum value to the average value of the four nuclear powers, that is, the larger of the ratio of the maximum value to the average value of the calibration output of the upper half of the external neutron detector or the ratio of the maximum value to the average value of the calibration output of the lower half of the external neutron detector.

[0045] 3. Using the nuclear power calibration method provided by this invention that takes into account quadrant power tilt, the QPTR-P obtained by the improved nuclear power calculation is within the limit of 1.02, and the unit does not need to reduce power or deactivate defense. Attached Figure Description

[0046] Figure 1 A flowchart of a nuclear power calibration method considering quadrant power tilt provided by the present invention;

[0047] Figure 2 The component power distribution diagram of the reactor core provided by this invention;

[0048] Figure 3 The cabinet layout diagram provided by the present invention is shown in the figure. UIC is a power range detector and CIC is an intermediate range detector.

[0049] Figure 4 Power tilt coefficient diagrams for the "×" and "+" quadrants provided in embodiments of the present invention.

[0050] Figure 5 Statistical QPTR results graphs for different calculation methods provided in the embodiments of the invention. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0052] like Figure 1 As shown, this invention provides a nuclear power calibration method considering quadrant power tilt, specifically including the following steps:

[0053] Step 1: Conduct thermal balance measurements to obtain accurate core power.

[0054] Under stable unit power conditions, a heat balance measurement is performed. The heat power measured by high-precision thermal instruments in the secondary loop is subtracted from the heat power of other heat sources in the primary loop to obtain the accurate core power W. R .

[0055] The determination of reactor thermal power in the heat balance measurement experiment is based on the enthalpy balance of each steam generator, that is:

[0056] The heat power transferred from the primary side of the steam generator to the secondary side + the heat power of the main feedwater = the heat power of the wet steam at the outlet of the steam generator + the heat power of the blowdown.

[0057] The enthalpy balance of the steam generator is converted into the actual output heat power of the reactor using the following formula:

[0058]

[0059] In the formula, Q vi =Q ei -Q pi

[0060] The above equation can then be derived as:

[0061]

[0062] In the formula:

[0063] W R —Core power, MW;

[0064] W SG—The thermal power provided by each steam generator, in MW;

[0065] —The thermal power input to the reactor coolant system from heat sources other than the reactor core, in MW;

[0066] Q e —Water supply flow rate, kg / s;

[0067] Q p —Sewage discharge flow rate, kg / s;

[0068] Q v —Wet steam flow rate, kg / s;

[0069] H e —Water enthalpy, kJ / kg;

[0070] H p —Enthalpy of discharged wastewater, kJ / kg;

[0071] H v —Enthalpy of wet steam at the steam generator outlet, kJ / kg

[0072] H v The calculation formula can be expressed as:

[0073] H v =x×H vs +(1-x)×H es (3)

[0074] H es —Enthalpy of saturated water, kJ / kg;

[0075] H vs —Saturated vapor enthalpy, kJ / kg;

[0076] x — vapor content, dimensionless;

[0077] 1-x — the amount of water entrained in the steam, dimensionless;

[0078] This is the net thermal power input to the reactor coolant system from heat sources other than the reactor core. This can be determined by commissioning tests and can be considered to remain constant at all power levels.

[0079] Step 2: Obtain the quadrant power tilt coefficient based on the core measurement system.

[0080] The in-line core measurement system (RII) measures the neutron flux of the reactor using a self-sufficient neutron detector (SPND). The rhodium in the rhodium self-sufficient neutron detector... 45 Rh 103 ) undergoes a radiotracer capture reaction (n, γ) with neutrons, producing 45Rh 104 Isotopes, after β decay, generate current, which is sent to a processing cabinet and undergoes a series of standardization processes to obtain a standard current.

[0081] The system comprises 44 core neutron flux measurement channels arranged radially along the reactor core. Each channel has seven self-powered point-and-distribution (SPND) detectors spaced equidistantly along the height of the active section of the core. Under normal operating conditions (after reactor startup), the system continuously acquires current signals from 308 fixed SPND detectors. Combined with power plant operating signals from the DCS, the system processes the data in the control cabinet and provides the real-time three-dimensional power distribution of the fuel assemblies.

[0082] In an online core measurement system, the Quadrant Power Tilt Ratio (QPTR) is the ratio of the maximum to the average output power in each of the four quadrants of the core, characterizing the degree of radial power tilt in the core. For clarity, the Quadrant Power Tilt Coefficient Q is used. i This represents the ratio of the output power in each of the four quadrants of the reactor core to the average value. Therefore, the quadrant power tilt coefficient Q during thermal equilibrium measurement is... i The average power of the modules within each quadrant can be used to calculate the average power of all modules in the entire stack. Module power is as follows: Figure 2 As shown:

[0083]

[0084] Where i = 1, 2, 3, 4, represents the four quadrant power range measurement channels. P i This represents the average power of components within the i-th quadrant.

[0085] Considering that the reactor core is arranged in a 1 / 8 symmetrical manner, the quadrant division has two types: "+" and "×".

[0086] Step 3: Combining the core power from Step 1 and the quadrant power tilt coefficient from Step 2, obtain the quadrant power for each of the four quadrants.

[0087] The accurate core power W of the unit was obtained from thermal balance measurements. R Combined with the quadrant power tilt coefficient Q i Calculate the quadrant power W in each quadrant during the thermal equilibrium measurement. i .

[0088] W i =W R ×Q i (5)

[0089] Step 4: Calibrate the core power of the corresponding channel based on the quadrant power of the four quadrants.

[0090] Nuclear power P RThe current is obtained by multiplying the current measured by the detector by the corresponding current-power conversion factor. The current measured by the detector is mainly affected by the power of nearby components. To accurately reflect the power in the quadrant where the detector is located, the quadrant division should include the detector. For power range detectors, a power tilt in the "+" quadrant better reflects the core power measured by the power range detector, such as... Figure 3 As shown.

[0091] The core power of each of the four power ranges was collected during the thermal equilibrium measurement. The average core power of each power range was then used as the core power P of that channel. Ri .

[0092] according to Figure 3 The correspondence between the core quadrants and the detector channels is shown in Table 1.

[0093] Table 1. Correspondence between core quadrants and detector channels

[0094] Quadrant Quadrant 4 Quadrant 2 Quadrant 3 Quadrant 1

[0095] The core power P of the channel Ri Quadrant power W corresponding to the quadrant i Perform deviation calculations and determine whether nuclear power calibration is necessary based on the results.

[0096] According to the requirements of the upstream technology guidelines, when the deviation between the displayed nuclear power value and the core power exceeds 1.5%FP (FP represents full power), the nuclear power needs to be calibrated.

[0097] After considering quadrant power tilt, the averaged core power is replaced with a more refined quadrant power. That is, when the displayed nuclear power value deviates from the corresponding quadrant power by more than 1.5% FP, the nuclear power needs to be calibrated. The purpose of calibration is to correct the current nuclear power to the current quadrant power. The current-power conversion factor K before calibration is adjusted according to the calibration factor correction formula. 0i After correction, the current-to-power conversion coefficient K of each channel after calibration is calculated. i The current-to-power conversion coefficient K of each calibrated channel. i The nuclear power after the corresponding channel calibration is obtained.

[0098] The calibration coefficient correction formulas for each channel are as follows:

[0099] Channel 1:

[0100] Channel 2:

[0101] Channel 3:

[0102] Channel 4:

[0103] Where i = 1, 2, 3, 4, represents the four quadrant power range measurement channels; P Ri (i = 1, 2, 3, 4) represents the core power of the i-th channel; W i (i = 1, 2, 3, 4) represents the quadrant power in the i-th quadrant; K i (i = 1, 2, 3, 4) represents the current-to-power conversion coefficient of the ith channel after calibration; K 0i (i = 1, 2, 3, 4) represents the current-power conversion coefficient of the i-th channel before calibration.

[0104] Example 1

[0105] Taking the nuclear power calibration after a certain thermal equilibrium as an example, the nuclear power calibration method of the present invention considering quadrant power tilt will be explained and described, specifically including the following steps:

[0106] Step 1: Perform a thermal balance measurement under stable unit power conditions. The measurement data is shown in Table 2, and the core power W is obtained. R = 99.2291%FP.

[0107] Table 2 Thermal balance measurement data

[0108]

[0109]

[0110] Step 2: Print the quadrant power tilt coefficient Q during thermal equilibrium from the RII system. i The division of quadrants into two types, "+" and "×", such as... Figure 4 As shown in Table 3, the power tilt coefficient values ​​for the "+" quadrant are selected.

[0111] Table 3 Power tilt coefficient values ​​for the "+" quadrant

[0112] <![CDATA[Q i ]]> 0.9982 0.9988 1.0013 1.0017

[0113] Step 3: Calculate the quadrant power W of the power range detector based on the results of Step 1 and Step 2. i The calculation results are shown in Table 4.

[0114] Table 4 Power Limit Calculation Results

[0115]

[0116]

[0117] Step 4: Export the core power of the four power ranges during the thermal equilibrium measurement from the DCS system, and take the average value as the core power P of the channel. R The core power of each channel is shown in Table 5.

[0118] Table 5. Nuclear power data for each channel.

[0119]

[0120] Step 5: Calculate the power factor after considering quadrant power tilt.

[0121] The calibration coefficient correction formula for each channel, combined with the data from steps four and five, is used to calculate the calibrated current-power conversion coefficient, and the results are shown in Table 6.

[0122] Table 6. Calculation results of the calibrated current-to-power conversion coefficient

[0123]

[0124] The current-to-power conversion coefficient K of each calibrated channel i The nuclear power after the corresponding channel calibration is obtained.

[0125] Example 2

[0126] When the RII (Research In-Instrumentation) measurement system is unavailable, the QPTR (Quality Pt Ratio) is monitored using the nuclear instrumentation system. Statistical results from different calculation methods are as follows: Figure 5 As shown.

[0127] According to the Operational Technical Specifications, when the QPTR exceeds the limit of 1.02, the unit needs to reduce power by at least 15% FP. The QPTR-I calculated using existing methods is always greater than 1.05, requiring the unit to reduce power and de-escalate protection; however, the QPTR-P calculated using the improved nuclear power rating is within the limit of 1.02, meaning the unit does not need to reduce power and de-escalate protection.

[0128] 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 nuclear power calibration considering quadrant power tilt, characterized in that, include: Step 1: Conduct thermal balance measurements to obtain core power; Step 2: Obtain the quadrant power tilt coefficient based on the core measurement system; Step 3: Based on the core power and quadrant power tilt coefficient, obtain the quadrant power of the four quadrants; Step 4: Calibrate the core power of the corresponding channel based on the quadrant power of the four quadrants.

2. The nuclear power calibration method considering quadrant power tilt according to claim 1, characterized in that, Step 1 includes: conducting heat balance measurement under stable unit power conditions, subtracting the heat power of other heat sources in the primary loop from the heat power measured by high-precision thermal instruments in the secondary loop to obtain the core power; the determination of reactor heat power in the heat balance measurement test is based on the enthalpy balance of each steam generator, that is: heat power transferred from the primary side of the steam generator to the secondary side = heat power of wet steam at the steam generator outlet - heat power of main feedwater + heat power of blowdown.

3. The nuclear power calibration method considering quadrant power tilt according to claim 2, characterized in that, The formula for calculating the core power in step 1 is as follows: in, W R —Core power, MW; W SG —The thermal power provided by each steam generator, in MW; —The thermal power input to the reactor coolant system from heat sources other than the reactor core, in MW; Q e —Water supply flow rate, kg / s; Q p —Sewage discharge flow rate, kg / s; Q v —Wet steam flow rate, kg / s; H e —Water enthalpy, kJ / kg; H p —Enthalpy of discharged wastewater, kJ / kg; H v —Enthalpy of wet steam at the steam generator outlet, kJ / kg.

4. The nuclear power calibration method considering quadrant power tilt according to claim 3, characterized in that, Step 2 includes: the core measurement system arranges multiple core neutron flux measurement channels radially along the core, and each measurement channel arranges multiple self-powered detectors (SPNDs) at equal intervals along the height of the active section of the core; under normal operating conditions, the system continuously acquires current signals from each fixed SPND; combined with the power plant operating condition signals from the DCS, the system processes the data in the control cabinet and provides the three-dimensional power distribution of the fuel assemblies in real time, obtaining the assembly power in the four quadrants of the core; based on the assembly power, the quadrant power tilt coefficient is calculated; the formula for calculating the quadrant power tilt coefficient is: Among them, Q i This represents the quadrant power tilt coefficient in the i-th quadrant; i = 1, 2, 3, 4, representing the four quadrant power range measurement channels; P i This represents the average power of components within the i-th quadrant.

5. The nuclear power calibration method considering quadrant power tilt according to claim 4, characterized in that, The formula for calculating quadrant power in step 3 is as follows: IN i =In R ×Q i Among them, W i W represents the quadrant power in the i-th quadrant; R Q represents the core power; i This represents the quadrant power tilt coefficient for the i-th quadrant.

6. The nuclear power calibration method considering quadrant power tilt according to claim 5, characterized in that, Step 4 includes: collecting the core power of four power ranges during the thermal balance measurement, averaging the core power of each power range as the core power of that channel; calculating the deviation between the core power of the channel and the quadrant power of the corresponding quadrant, and determining whether the core power needs to be calibrated based on the deviation calculation result; if the core power needs to be calibrated, calculating the current-power conversion coefficient of each calibrated channel according to the calibration coefficient correction formula; and obtaining the calibrated core power of the corresponding channel through the current-power conversion coefficient of each calibrated channel.

7. A nuclear power calibration method considering quadrant power tilt according to claim 6, characterized in that, In step 4, the correspondence between channels and quadrants is as follows: channel 1 corresponds to quadrant 4, channel 2 corresponds to quadrant 2, channel 3 corresponds to quadrant 3, and channel 4 corresponds to quadrant 1.

8. A nuclear power calibration method considering quadrant power tilt according to claim 7, characterized in that, In step 4, when the core power P of the channel Ri Quadrant power W corresponding to the quadrant i When the deviation exceeds 1.5%FP, the nuclear power needs to be calibrated.

9. A nuclear power calibration method considering quadrant power tilt according to claim 8, characterized in that, In step 4, the calibration coefficient correction formula for each channel is as follows: Channel 1: Channel 2: Channel 3: Channel 4: Where i = 1, 2, 3, 4, represents the four quadrant power range measurement channels; P Ri (i = 1, 2, 3, 4) represents the core power of the i-th channel; W i (i = 1, 2, 3, 4) represents the quadrant power in the i-th quadrant; K i (i = 1, 2, 3, 4) represents the current-to-power conversion coefficient of the ith channel after calibration; K 0i (i = 1, 2, 3, 4) represents the current-power conversion coefficient of the i-th channel before calibration.

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