Reactor coolant system and its loop flow rate correction method

Abstract

The present invention discloses a reactor coolant system and a method for correcting the loop flow rate thereof. The reactor coolant system includes a plurality of loops. Each individual loop includes a pressure vessel, a steam generator, a main pump, and a channel pipeline connected between the steam generator and the main pump. The channel pipeline is provided with an elbow section at the outlet of the steam generator. A high-pressure side interface is provided at the outer diameter of the elbow section, and a plurality of low-pressure side interfaces are provided at the inner diameter thereof. A measurement circuit for measuring the flow rate value in the corresponding channel pipeline is provided on each channel pipeline. The measurement circuit includes a main measurement path connected to the high-pressure side interface and at least two measurement branches respectively connected to the main measurement path. A flow transmitter is provided on each measurement branch. One end of the flow transmitter is connected to the main measurement path, and the other end is connected to the low-pressure side interface. It realizes the accurate measurement of the loop flow rate of the reactor coolant system and prevents the measured loop flow rate data from being reduced in accuracy due to the scouring effect of the fluid on the bending section.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power, and in particular to a reactor coolant system and a method for correcting the loop flow rate thereof. Background Art

[0002] In the related art, a reactor coolant system is provided in a nuclear power plant, that is, the main loop of the primary loop of a nuclear power unit. Its main function is to make the coolant circulate, transfer the heat generated by nuclear fission in the reactor core to the secondary loop through a steam generator, and at the same time cool the reactor core to prevent the fuel elements from burning or being damaged. Therefore, as an important parameter, the loop flow rate needs to be measured, sent to the screen for display, and participate in the reactor protection logic. If the flow rate of a certain loop is less than the rated flow rate, a low coolant loop flow rate signal is generated; if the reactor power is greater than the first preset value and the flow rates of more than two loops are low, or the reactor power is greater than the second preset value and the flow rate of more than one loop is low, an emergency reactor shutdown signal is issued.

[0003] After the nuclear power unit has been operating for a long time, due to the certain scouring effect of the fluid on the bending section, the differential pressure value generated by the elbow section will also change, that is to say, its differential pressure range will also change to a certain extent. These changes will cause deviations in the measured loop flow rate. If the actual working conditions cannot be accurately reflected, it is easy to cause signal confusion and even lead to the occurrence of accident conditions. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a reactor coolant system and a method for correcting the loop flow rate thereof in view of at least one defect existing in the prior art.

[0005] The technical solution adopted by the present invention to solve its technical problems is to construct a reactor coolant system, including several loops for circulating cooling. Each loop includes a pressure vessel, a steam generator, a main pump, and a channel pipeline connecting between the steam generator and the main pump; a bending section is provided at the outlet of the steam generator of the channel pipeline.

[0006] A high-pressure side interface is provided at the outer diameter of the bending section, and several low-pressure side interfaces are provided at its inner diameter; a measurement loop for measuring the flow rate value in the corresponding channel pipeline is provided on each channel pipeline; the measurement loop includes a measurement main path connected to the high-pressure side interface, and at least two measurement branches respectively connected to the measurement main path; a flow transmitter is provided on each measurement branch; one end of the flow transmitter is connected to the measurement main path, and the other end is connected to the low-pressure side interface.

[0007] The present invention also constructs a method for correcting the loop flow rate of a reactor coolant system, which is realized based on the above reactor coolant system. The correction method includes the following steps:

[0008] S10. Channel pipeline deviation judgment: Obtain the flow values of the flow transmitters in each channel pipeline, and combine the error factors of the thermal measurement instruments to calculate and judge whether the corresponding channel pipeline has no deviation. If there is no deviation, proceed to the next step;

[0009] Among them, the thermal measurement instruments include flow transmitters for collecting differential pressure signals, channel circuit boards for receiving and processing the collected differential pressure signals, and display panels for displaying pictures;

[0010] S20. Channel pipeline failure judgment: Obtain the failure criterion through the analysis of the channel pipeline failure probability, calculate and judge the failure probability of the corresponding channel pipeline. If the failure probability is not higher than the failure criterion, proceed to the next step;

[0011] S30. Differential pressure zero adjustment: Obtain the shutdown flow standard value when the reactor coolant system operates under the condition of hot shutdown of the steam generator in the nuclear power unit, and combine the accuracy of the flow transmitter, its interference factors, and the uncertainty factors caused on-site to adjust the zero value of each flow transmitter;

[0012] S40. Differential pressure range adjustment: Obtain the full-scale differential pressure value measured by the flow transmitter on the corresponding channel pipeline in the original state, and combine the actual operating flow parameters of the corresponding channel pipeline to calculate the actual differential pressure value of the corresponding channel pipeline;

[0013] S50. Differential pressure range correction: Obtain the loop flow standard value under the preset working condition, and combine the actual differential pressure value of the corresponding channel pipeline to calculate the corrected full-scale differential pressure value.

[0014] Preferably, in step S10, the following sub-steps are included:

[0015] S11: Obtain the error factors of the thermal measurement instruments, and the error factors include the technical accuracy of the flow transmitter, the uncertainty of the channel circuit board, and the uncertainty of the display picture in the display panel;

[0016] S12: Correspondingly obtain the comprehensive uncertainty of the channel pipeline according to the error factors, and the comprehensive uncertainty includes layer 0 uncertainty U0, layer 1 uncertainty U1, and layer 2 uncertainty U2;

[0017] S13: According to the comprehensive uncertainty, calculate the full-channel uncertainty Δε1 by using formula (1); formula (1) is expressed as:

[0018]

[0019] S14: Obtain the flow values of the flow transmitters in each channel pipeline respectively, and calculate and determine whether the difference between the flow value of each flow transmitter and the average value of the flow values of the remaining flow transmitters is not higher than the overall channel uncertainty Δε1. If so, determine that there is no deviation in the corresponding channel pipeline and execute the next step.

[0020] Preferably, in step S20, the following sub-steps are included:

[0021] S21: Obtain and calculate the failure criterion Δε2 according to the functional tolerance, technical accuracy of the flow transmitter, and the number of redundant flow transmitters, using Equation (4); Equation (4) is expressed as:

[0022]

[0023] where δ(FS) is the functional tolerance of the flow transmitter; ε(t) is the technical accuracy of the flow transmitter; X is a coefficient determined by the number of flow transmitters in a single channel pipeline;

[0024] S22: Obtain the average flow value measured by the flow transmitter in each channel pipeline and the flow standard value under the preset working condition;

[0025] S23: Calculate and determine whether the difference between the average flow value and the flow standard value is not higher than the failure criterion Δε2; if so, execute the next step.

[0026] Preferably, in step S30, the following sub-steps are included:

[0027] S31: Calculate the zero point criterion Δε3 according to the accuracy of the flow transmitter, its interference factors, and the uncertainty factors caused on-site, using Equation (7); Equation (7) is expressed as:

[0028]

[0029] where ε 1-1 is the accuracy of the flow transmitter; ε 1-2 is the root mean square of all uncertainty factors caused on-site; ε 1-3 , ε 1-4 , ε 1-5 , ε 1-6 are the interference factors of the flow transmitter respectively;

[0030] S32: Adjust the zero point value of each flow transmitter according to the zero point criterion Δε3, in combination with Equation (8), Equation (8) is expressed as;

[0031] |Q”’ An -λ3|≤Δε3 (8)

[0032] Among them, Q''' An is the zero value of any flow transmitter in a single-channel pipeline; λ3 is the shutdown flow standard value under the cooling heat shutdown condition of the steam generator in the nuclear power unit.

[0033] Preferably, in step S40, it includes the following sub-steps:

[0034] S41: Obtain the original full-scale differential pressure value of the flow transmitter on the corresponding channel pipeline;

[0035] S42: Obtain the actual operating flow parameters of the corresponding channel pipeline, and the actual operating flow parameters include the average operating flow value of the corresponding channel pipeline under the operation of all main pumps in the same period and the non-operating flow value of the corresponding channel pipeline when all main pumps are not operating;

[0036] S43: Calculate the average operating flow current value and the non-operating flow current value of the corresponding channel pipeline according to the average operating flow value and the non-operating flow value of the corresponding channel pipeline;

[0037] S44: Calculate the actual differential pressure value of the corresponding channel pipeline by using Equation (9) according to the average operating flow current value, the non-operating flow current value and the original full-scale differential pressure value; Equation (9) is expressed as:

[0038]

[0039] Among them, ΔP Xn refers to the actual differential pressure value of any channel pipeline, refers to the average operating flow current value of the channel pipeline to be obtained, C' Xn refers to the non-operating flow current value of the channel pipeline to be obtained, ΔP max refers to the original full-scale differential pressure value on the channel pipeline to be obtained.

[0040] Preferably, the preset conditions include the full-power operation condition of the nuclear power unit and the cooling heat shutdown condition of the steam generator of the nuclear power unit.

[0041] Preferably, in step S50, it includes the following sub-steps:

[0042] S51: Obtain the first flow standard value under the full-power operation condition of the nuclear power unit;

[0043] S52: Calculate the corrected full-scale differential pressure value by using Equation (10) according to the actual differential pressure value of the corresponding channel pipeline and the first flow standard value; Equation (10) is expressed as:

[0044]

[0045] Among them, ΔP' maxXnis the corrected full-scale differential pressure value for each flow transmitter in any channel pipeline; λ1 is the first flow standard value; ΔP Xn refers to the actual differential pressure value corresponding to the channel pipeline to be determined.

[0046] Preferably, in step S50, the following sub-steps are included:

[0047] S53: Obtain the second flow standard value under the condition of the cooling heat shutdown of the steam generator of the nuclear power unit;

[0048] S54: According to the actual differential pressure value of the corresponding channel pipeline and the second flow standard value, calculate and obtain the corrected full-scale differential pressure value by using formula (11); the formula (11) is expressed as:

[0049]

[0050] where, ΔP’ maxXn is the corrected full-scale differential pressure value for each flow transmitter in any channel pipeline; λ2 is the second flow standard value; Δp Xn refers to the actual differential pressure value corresponding to the channel pipeline to be determined.

[0051] Preferably, when the range of the flow transmitter is 120%, it displays its full-scale differential pressure value.

[0052] Implementing the present invention has the following beneficial effects: It can accurately measure the loop flow rate of the reactor coolant system and prevent the measured loop flow rate data from being inaccurate due to the scouring effect of the fluid on the bending section. Description of the Drawings

[0053] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0054] Figure 1 is a schematic structural diagram of the reactor coolant system in the present invention. Detailed Embodiments

[0055] In order to have a clearer understanding of the technical features, objectives and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the drawings.

[0056] It should be noted that the flowcharts shown in the drawings are only illustrative and do not necessarily include all the contents and operations / steps, nor do they necessarily need to be executed in the described order. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined. Therefore, the actual execution order may change according to the actual situation.

[0057] The block diagrams shown in the drawings are only functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0058] In the related art, as Figure 1 shown, the reactor coolant system includes several loops. A single loop includes a pressure vessel 4, a steam generator 1, a main pump 2, and a channel pipeline 3 for connecting the steam generator 1 and the main pump 2; the steam generator 1 is connected to the main pump 2 through the channel pipeline 3. Among them, in some related arts, the reactor coolant system includes three loops, corresponding to three steam generators 1, three main pumps 2, and three corresponding connecting channel pipelines 3; a single channel pipeline 3 has a bent structure at the outlet of the steam generator 1, forming a bent pipe section 31.

[0059] As an important parameter, the loop flow rate needs to be measured, sent to the display screen, and participate in the reactor protection logic. If the flow rate of a certain loop is less than 88.8% Qn (rated flow rate), a low coolant loop flow rate signal (2 / 3 logic) is generated. If the reactor power is greater than 10% Pn (the first preset value) and there are more than two loops with low flow rates, or the reactor power is greater than 30% Pn (the second preset value) and there is more than one loop with a low flow rate, an emergency reactor shutdown signal is issued.

[0060] After the reactor coolant system has been operating for a long time, due to the scouring effect of the fluid on the bending section, the differential pressure value generated by the bent pipe section 31 will also change, that is, its differential pressure range will also change to a certain extent. Therefore, it is necessary to calculate and correct the differential pressure values of these flow transmitters 53 according to the test results so that their measured values can accurately reflect the actual working conditions.

[0061] Therefore, the present invention constructs a reactor coolant system and its loop flow rate correction method, which acts on the reactor coolant system, can achieve accurate measurement of the loop flow rate, and prevent the accuracy from decreasing under the scouring action of the fluid on the bending section.

[0062] The correction method includes the following steps:

[0063] S10. Channel pipeline deviation judgment: Obtain the flow rate values of the flow transmitters in each channel pipeline, and combine the error factors of the thermal measurement instruments to calculate and judge whether the corresponding channel pipeline has no deviation. If there is no deviation, execute the next step;

[0064] Further, if not, it is judged that the corresponding channel pipeline has a deviation, and the measurement circuit is checked for errors. After the check, step S10 is executed again.

[0065] Understandably, since the fluid has a certain scouring effect on the channel pipeline, the differential pressure value generated in the elbow section will also change to some extent. Therefore, it is necessary to track and monitor the change trend.

[0066] As Figure 1 shown, in the present invention, a single common high-pressure side interface 32 is provided at the outer diameter of the elbow section 31 of the channel pipeline 3, and a plurality of low-pressure side interfaces 33 are provided on the inner side of the channel pipeline 3; these interfaces can be used to connect a flow transmitter 53 to measure the single-loop flow rate. Understandably, the inner side of the channel pipeline 3 is the opposite side of the high-pressure side interface 32 provided on the channel pipeline 3. In addition, a measurement circuit 5 for measuring the differential pressure value inside the channel pipeline 3 is provided on each channel pipeline 3. The measurement circuit 5 includes a measurement main path 51 and at least two measurement branches 52. One end of the measurement main path 51 is connected to the high-pressure side interface 32, and the other end thereof is respectively connected to all the measurement branches 52; further, a single measurement branch 52 includes a flow transmitter 53 and a branch valve for switching the fluid. One end of the flow transmitter 53 is connected to the measurement main path 51, and the other end thereof is connected to the corresponding single low-pressure side interface 33 through the branch valve.

[0067] In some embodiments, the measurement main path 51 is further provided with a main valve for controlling the switching of the fluid in all the measurement branches 52. In the first embodiment, in order to avoid misjudgment of the measurement deviation caused by the measurement channel deviation of the individual loop flow transmitter, redundant loop flow transmitters are provided for cross-verification. Specifically: three measurement circuits 5 are provided on each channel pipeline 3, and correspondingly, three flow transmitters 53 are provided on each channel pipeline 3.

[0068] The flow transmitter uses the inertia principle of the fluid to generate a differential pressure and convert it into an electrical signal to measure the flow rate value. The specific principle can be referred to the relevant technical manual. Due to the action of the centrifugal force, there is a differential pressure value ΔP between the outer diameter and the inner diameter of the elbow, and the relationship between it and the flow rate Q is: ΔP∝Q 2 , theoretically, the measured values obtained by each flow transmitter are consistent, but in fact, there is uncertainty in the measurement link, which is very likely to cause deviation in the measurement channel pipeline. Therefore, it is first necessary to ensure the accuracy of each channel pipeline to prevent measurement deviation caused by channel pipeline deviation, resulting in incorrect correction of the flow transmitter.

[0069] Therefore, further, in step S10, it includes the following sub-steps:

[0070] S11: Obtain the error factors of the thermal measurement instrument, and the error factors include the technical accuracy of the flow transmitter, the uncertainty of the channel board, and the uncertainty of the display screen in the display section;

[0071] S12: Obtain the comprehensive uncertainty of the channel pipeline corresponding to the error factor, where the comprehensive uncertainty includes the uncertainty U0 of layer 0, the uncertainty U1 of layer 1, and the uncertainty U2 of layer 2;

[0072] S13: According to the comprehensive uncertainty, calculate the full-channel uncertainty Δε1 using Equation (1); Equation (1) is expressed as:

[0073]

[0074] It can be understood that the full-channel uncertainty Δε1 is affected by the error factors of the thermal measurement instrument. The thermal measurement instrument includes a flow transmitter for collecting differential pressure signals, a channel board for receiving and processing the collected differential pressure signals, and a display panel for displaying the screen; the specific composition of the thermal measurement instrument can refer to the prior art and will not be elaborated here. The full-channel uncertainty Δε1 includes the uncertainty U0 of layer 0, the uncertainty U1 of layer 1, and the uncertainty U2 of layer 2; further, the uncertainty U0 of layer 0 is the technical accuracy of the flow transmitter, the uncertainty U1 of layer 1 is the uncertainty of the channel board, and the uncertainty U2 of layer 2 is the uncertainty of the displayed screen in the display panel; it should be noted that the uncertainty U0 of layer 0, the uncertainty U1 of layer 1, and the uncertainty U2 of layer 2 can all be provided by the manufacturer or obtained by referring to relevant technical manuals.

[0075] In each channel pipeline, if the difference between the flow value of a single flow transmitter and the average value of the flow values of the remaining flow transmitters does not exceed the full-channel uncertainty Δε1, it indicates that the measurement loop is accurate; otherwise, the measurement loop needs to be checked for errors. The specific calculation method is as follows:

[0076]

[0077] Among them, in Equations (2) and (3), Q A1 , Q A2 ... Q A(n-1) , Q An respectively represent the flow values corresponding to all flow transmitters in a single channel pipeline; among them, the number of flow transmitters in the measurement loop is n, n≥2, and n is a positive integer.

[0078] In the first embodiment, since three flow transmitters are set in a single channel pipeline, and the flow values corresponding to the three flow transmitters are Q A1 , Q A2 , Q A3 . According to Equations (2) and (3), it can be obtained that:

[0079]

[0080] Therefore, if the flow values Q corresponding to the three flow transmittersA1 , Q A2 , Q A3 If they respectively meet the conditions in the above formulas (2-1), (3-1) and (3-2), it is determined that the corresponding channel pipeline has no deviation.

[0081] S20. Failure judgment of the channel pipeline: Obtain the failure criterion through the analysis of the failure probability of the channel pipeline, calculate and judge the failure probability of the corresponding channel pipeline. If the failure probability is not higher than the failure criterion, execute the next step;

[0082] Furthermore, if the failure probability is higher than the failure criterion, the differential pressure correction of the flow transmitter needs to be carried out.

[0083] Specifically, in step S20, the following sub-steps are included:

[0084] S21: Obtain and calculate the failure criterion Δε2 by using formula (4) according to the functional tolerance, technical accuracy of the flow transmitter and the number of redundant flow transmitters; the formula (4) is expressed as:

[0085]

[0086] Wherein, δ(FS) is the functional tolerance of the flow transmitter; ε(t) is the technical accuracy of the flow transmitter; X is a coefficient determined by the number of flow transmitters in a single channel pipeline; it can be understood that since the flow transmitters all adopt the same specification and model, therefore, the functional tolerances and technical accuracies of several flow transmitters can be considered consistent; and the number n of redundant flow transmitters refers to the number n of flow transmitters in the above channel pipeline.

[0087] S22: Obtain the average flow value measured by the flow transmitter in each channel pipeline and the flow standard value under the preset working condition;

[0088] S23: Calculate and judge whether the difference between the average flow value and the flow standard value is not higher than the failure criterion Δε2; if so, execute the next step.

[0089] It can be understood that the failure probability of the channel pipeline is affected by the functional tolerance, technical accuracy of the flow transmitter and the number of redundant flow transmitters; in some embodiments, the failure criterion Δε2 is to ensure a failure detection success rate of more than 95%.

[0090] Obtain the flow standard value of the reactor coolant system under the preset working condition, calculate and compare the average value of the flow values of all the flow transmitters in the measurement loop with this flow standard value to obtain the failure probability; if the difference between the average flow value and the flow standard value under the preset working condition is not higher than the failure criterion Δε2, there is no need to carry out differential pressure correction on the flow transmitter; if it exceeds the allowable range, that is, exceeds the failure criterion Δε2, differential pressure correction of the flow transmitter is required.

[0091] Since the loop standard values of the reactor coolant system are not the same under different unit operating conditions, in order to better complete the correction work, different loop flow standard values are set according to different preset conditions. In some embodiments, the preset conditions include the full power operation condition of the nuclear power unit and the hot shutdown condition of the steam generator of the nuclear power unit for cooling; among them, in the full power operation condition of the nuclear power unit, the first flow standard value λ1 = 100%, and in the hot shutdown condition of the steam generator of the nuclear power unit for cooling, the second flow standard value λ2 = 101%.

[0092] The specific calculation and comparison formula is as follows:

[0093]

[0094] Among them, in the first embodiment, since three flow transmitters are arranged on the measurement loop, according to formulas (5) and (6), it can be obtained that:

[0095]

[0096] Therefore, if the flow values Q A1 、Q A2 、Q A3 corresponding to the three flow transmitters respectively meet the conditions in the above formulas (5-1) and (6-1), the next step can be executed.

[0097] S30. Differential pressure zero adjustment: Obtain the shutdown flow standard value when the reactor coolant system operates under the hot shutdown condition of the steam generator of the nuclear power unit, and adjust the zero value of each flow transmitter in combination with the accuracy of the flow transmitter, its interference factors, and the uncertainty factors caused on site;

[0098] Furthermore, in step S30, the following sub-steps are included:

[0099] S31: Calculate the zero standard Δε3 using formula (7) according to the accuracy of the flow transmitter, its interference factors, and the uncertainty factors caused on site; the formula (7) is expressed as:

[0100]

[0101] Among them, the zero standard Δε3 is calculated based on the uncertainty of the flow transmitter; among them, in formula (7), ε 1-1 is the accuracy of the flow transmitter, which is an inherent value, and its value generally refers to the reference accuracy provided by the manufacturer; ε 1-2 is the root mean square of all uncertainty factors introduced by on-site or laboratory calibration, such as: the accuracy of multimeters, pressure generators, and resistors; ε 1-3 、ε 1-4 、ε1-5 , ε 1-6 are the interference factors on the flow transmitter. In some embodiments, the interference factors may be temperature, inlet pressure, radiation factors, etc.

[0102] S32: Adjust the zero value of each flow transmitter according to the zero standard Δε3 in combination with Equation (8), and Equation (8) is expressed as;

[0103] |Q”’ An -λ3| ≤ Δε3 (8)

[0104] where Q”’ An is the zero value of any flow transmitter in a single-channel pipeline; λ3 is the flow standard value under the cooling heat stop condition of the steam generator of the nuclear power unit. Since the three main pumps are shut down under this condition and the strong circulation is lost, the stop-flow standard value λ3 = 0 at this time.

[0105] In the first embodiment, since three flow transmitters are provided on the measurement loop, it can be obtained according to Equation (8):

[0106] |Q”’ A1 -λ3| ≤ Δε3 (8-1)

[0107] |Q”’ A2 -λ3| ≤ Δε3 (8-2)

[0108] |Q”’ A3 -λ3| ≤ Δε3 (8-3)

[0109] S40: Differential pressure range adjustment: Obtain the full-scale differential pressure value of the flow transmitter measured on the corresponding channel pipeline in the original state, and calculate the actual differential pressure value of the corresponding channel pipeline in combination with the actual operating flow parameters of the corresponding channel pipeline;

[0110] Further, in step S40, it includes the following sub-steps:

[0111] S41: Obtain the original full-scale differential pressure value of the flow transmitter on the corresponding channel pipeline;

[0112] S42: Obtain the actual operating flow parameters of the corresponding channel pipeline. The actual operating flow parameters include the average operating flow value of the corresponding channel pipeline under the operation of all main pumps in the same period and the non-operating flow value of the corresponding channel pipeline when all main pumps are not operating;

[0113] Understandably, several main pumps operate simultaneously. At this time, the flow in the same loop is established. To eliminate the deviation in the measurement of the short-term flow fluctuation of the flow transmitter, the average operation flow value of each channel pipeline during the operation of all main pumps is obtained by taking the average value over a certain period T. In the first embodiment, there are three channel pipelines. Therefore, the average operation flow values are respectively

[0114] It should be noted that the average operation flow value is obtained by measuring with a flow transmitter. When there are several flow transmitters in a single channel pipeline, the data measured by any one of the flow transmitters can be used to calculate the average operation flow value of this channel pipeline.

[0115] Similarly, the non-operating flow current value is obtained, which will not be elaborated here.

[0116] S43: Calculate the average operation flow current value and the non-operating flow current value of the corresponding channel pipeline according to the average operation flow value and the non-operating flow value of the corresponding channel pipeline;

[0117] Understandably, since the working principle of the flow transmitter is to convert the collected flow value into a corresponding electrical signal, when the flow transmitter measures the average operation flow value and the non-operating flow value of each channel pipeline, the flow transmitter can display the corresponding average operation flow current value and the non-operating flow current value; in the first embodiment, there are three channel pipelines. Therefore, the average operation flow values are respectively and while the non-operating flow current values are respectively C’ An 、C’ Bn 、C’ Cn .

[0118] S44: Calculate the actual differential pressure value of the corresponding channel pipeline according to the average operation flow current value, the non-operating flow current value and the original full-scale differential pressure value, using Equation (9); Equation (9) is expressed as:

[0119]

[0120] where, ΔP Xn refers to the actual differential pressure value of any channel pipeline, refers to the average operation flow current value of the channel pipeline to be obtained, C’ Xn refers to the non-operating flow current value of the channel pipeline to be obtained, ΔP max refers to the original full-scale differential pressure value on the channel pipeline to be obtained.

[0121] Understandably, the original full-scale differential pressure value of each flow transmitter is set as ΔP max , that is: 0~ΔP maxCorresponding to 0 to 120% of the flow rate. The original full-scale differential pressure value can be obtained when the fluid is first introduced into the channel pipeline. When the display range of the flow transmitter reaches 120%, the corresponding original full-scale differential pressure value ΔP is measured. max It should be noted that the original full-scale differential pressure value ΔP is not necessarily obtained only when the fluid is first introduced. max As long as the channel pipeline is not affected by the erosion effect caused by the fluid.

[0122] In the first embodiment, there are three channel pipelines. Therefore, X in Equation (9) can be A, B, and C; according to Equation (9), the respective actual differential pressure values of the three channel pipelines are obtained by substitution, specifically:

[0123]

[0124]

[0125] Among them, the parameter meanings in Equations (9-1), (9-2), and (9-3) can refer to Equation (9), which will not be elaborated here.

[0126] S50. Differential pressure range correction: Obtain the standard value of the loop flow rate under the preset working conditions, and calculate the corrected full-scale differential pressure value in combination with the actual differential pressure value of the corresponding channel pipeline.

[0127] It can be understood that, as described above, the preset working conditions include the full-power operation condition of the nuclear power unit and the cold shutdown condition of the steam generator of the nuclear power unit; among them, the first flow rate standard value λ1 = 100% under the full-power operation condition of the nuclear power unit, and the second flow rate standard value λ2 = 101% under the cold shutdown condition of the steam generator of the nuclear power unit.

[0128] Under different working conditions, based on the differential pressure and flow rate relationship ΔP∝Q 2 , calculate the corrected full-scale differential pressure value according to the standard value of the loop flow rate and the actual differential pressure value of the corresponding channel pipeline under the corresponding working conditions;

[0129] Furthermore, in step S50, it includes the following sub-steps:

[0130] S51: Obtain the first flow rate standard value under the full-power operation condition of the nuclear power unit;

[0131] S52: Calculate the corrected full-scale differential pressure value by using Equation (10) according to the actual differential pressure value of the corresponding channel pipeline and the first flow rate standard value; Equation (10) is expressed as:

[0132]

[0133] Among them, ΔP’ maxXnis the corrected full-scale differential pressure value for each flow transmitter in any channel pipeline; λ1 is the first flow standard value; ΔP Xn refers to the actual differential pressure value corresponding to the channel pipeline to be determined.

[0134] Further, in step S50, the following sub-steps are included:

[0135] S53: Obtain the second flow standard value under the condition of the nuclear power unit steam generator cooling heat stop.

[0136] S54: According to the actual differential pressure value of the corresponding channel pipeline and the second flow standard value, calculate the corrected full-scale differential pressure value by using formula (11); the formula (11) is expressed as:

[0137]

[0138] where, ΔP’ maxXn is the corrected full-scale differential pressure value for each flow transmitter in any channel pipeline; λ2 is the second flow standard value; ΔP Xn refers to the actual differential pressure value corresponding to the channel pipeline to be determined.

[0139] In the first embodiment, there are three channel pipelines. Therefore, X in formula (9) can be A, B, and C; according to formula (10), substitute to obtain the corrected full-scale differential pressure values of the flow transmitters of the three channel pipelines respectively under the condition of the nuclear power unit full power operation, specifically:

[0140]

[0141] Similarly, according to formula (11), substitute to obtain the corrected full-scale differential pressure values of the flow transmitters of the three channel pipelines respectively under the condition of the nuclear power unit steam generator cooling heat stop, specifically:

[0142]

[0143] S60. Transmitter calibration: Calibrate the flow transmitters in the corresponding channel pipelines according to the corrected full-scale differential pressure values to complete the correction of the reactor coolant system loop flow.

[0144] Understandably, according to the corrected full-scale differential pressure value obtained under the preset working conditions, all flow transmitters in the channel pipeline corresponding to the corrected full-scale differential pressure value are calibrated to change the differential pressure range in the corresponding flow transmitter. For example, the differential pressure range of the original flow transmitter is 0 to 1.23 bar corresponding to 0 to 120% flow. Due to fluid scouring of the channel pipeline, the differential pressure value generated in the elbow section of the channel pipeline deviates. The range is calibrated according to the above method, and the differential pressure range of the corrected flow transmitter is 0 to 1.12 bar corresponding to 0 to 120% flow, completing the correction of the loop flow of the reactor coolant system.

[0145] It is understandable that the above embodiments only express the preferred embodiments of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present invention; it should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can also be made, which all belong to the protection scope of the present invention; therefore, all equivalent transformations and modifications made to the scope of the claims of the present invention shall fall within the scope covered by the claims of the present invention.

Claims

1. A method for correcting the loop flow rate of a reactor coolant system, which is applied to a reactor coolant system. The reactor coolant system includes several loops for circulating cooling. Each loop includes a pressure vessel (4), a steam generator (1), a main pump (2), and a channel pipeline (3) connected between the steam generator (1) and the main pump (2); a bent pipe section (31) is provided at the outlet of the steam generator (1) on the channel pipeline (3); a high-pressure side interface (32) is provided at the outer diameter of the bent pipe section (31), and several low-pressure side interfaces (33) arranged axially at intervals along the channel pipeline (3) are provided at the downstream position of its inner diameter; a measurement loop (5) for measuring the flow rate value in the corresponding channel pipeline (3) is provided on each channel pipeline (3); the measurement loop (5) includes a measurement main path (51) connected to the high-pressure side interface, and at least two measurement branches (52) respectively connected to the measurement main path (51); a flow transmitter (53) is provided on each measurement branch (52); one end of the flow transmitter (53) is connected to the measurement main path (51), and the other end is connected to the low-pressure side interface (33), and it is characterized in that, The correction method includes the following steps: S10. Channel pipeline deviation judgment: Obtain the flow values of the flow transmitters in each channel pipeline, and combine the error factors of the thermal measurement instruments to calculate and judge whether the corresponding channel pipeline has no deviation. If there is no deviation, proceed to the next step; Among them, the thermal measurement instruments include a flow transmitter for collecting differential pressure signals, a channel board for receiving and processing the collected differential pressure signals, and a display board for displaying the screen; S20. Channel pipeline failure judgment: Obtain the failure standard through the analysis of the channel pipeline failure probability, calculate and judge the failure probability of the corresponding channel pipeline. If the failure probability is not higher than the failure standard, proceed to the next step; S30. Differential pressure zero adjustment: Obtain the shutdown flow standard value when the reactor coolant system operates under the condition of hot shutdown of the steam generator of the nuclear power unit, and combine the accuracy of the flow transmitter, its interference factors, and the uncertainty factors caused on site to adjust the zero value of each flow transmitter; Among them, in step S30, the following sub-steps are included: S31: Calculate the zero point standard using Equation (7) based on the accuracy of the flow transmitter, its interference factors, and the uncertainty factors caused on-site. ; Equation (7) is expressed as: Among them, is the accuracy of the flow transmitter; is the root mean square of all uncertainty factors caused by the field; , , , are the interference factors of the flow transmitter respectively; S32: According to the zero point standard , adjust the zero point value of each flow transmitter in combination with formula (8), and the formula (8) is expressed as; Among them, is the zero value of any flow transmitter in a single-channel pipeline; is the shutdown flow standard value under the condition of the cooling heat shutdown of the steam generator in the nuclear power unit; S40. Differential pressure range adjustment: Obtain the full-scale differential pressure value measured by the flow transmitter on the corresponding channel pipeline in the original state, and combine the actual operating flow parameters of the corresponding channel pipeline to calculate the actual differential pressure value of the corresponding channel pipeline; Among them, in step S40, the following sub-steps are included: S41: Obtain the original full-scale differential pressure value of the flow transmitter on the corresponding channel pipeline. The original full-scale differential pressure value is the full-scale differential pressure value measured without being affected by the fluid erosion effect of the channel pipeline; S42: Obtain the actual operating flow parameters of the corresponding channel pipeline. The actual operating flow parameters include the average operating flow value of the corresponding channel pipeline under the operation of all main pumps in the same cycle and the non-operating flow value of the corresponding channel pipeline when all main pumps are not operating; S43: Calculate the average operating flow current value and the non-operating flow current value of the corresponding channel pipeline according to the average operating flow value and the non-operating flow value of the corresponding channel pipeline; S44: Calculate the actual differential pressure value of the corresponding channel pipeline by using formula (9) according to the average operating flow current value, the non-operating flow current value, and the original full-scale differential pressure value. The formula (9) is expressed as: Among them, represents the actual differential pressure value of any channel pipeline, represents the average operating flow current value of the channel pipeline to be obtained, represents the non-operating flow current value of the channel pipeline to be obtained, represents the original full-scale differential pressure value on the channel pipeline to be obtained; S50. Differential pressure range correction: Obtain the loop flow standard value under the preset working condition, and combine the actual differential pressure value of the corresponding channel pipeline to calculate the corrected full-scale differential pressure value.

2. The method for correcting the loop flow rate of the reactor coolant system according to claim 1, wherein In step S10, the following sub-steps are included: S11: Obtain the error factors of the thermal measurement instruments. The error factors include the technical accuracy of the flow transmitter, the uncertainty of the channel board, and the uncertainty of the display screen in the display board; S12: Obtain the comprehensive uncertainty of the channel pipeline corresponding to the error factor, and the comprehensive uncertainty includes the uncertainty of layer 0 , the uncertainty of layer 1 , the uncertainty of layer 2 ; S13: Calculate the full-channel uncertainty according to the comprehensive uncertainty by using Equation (1). ; Equation (1) is expressed as: S14: Obtain the flow values of the flow transmitters in each channel pipeline respectively, and calculate and determine whether the difference between the flow value of each flow transmitter and the average value of the flow values of the remaining flow transmitters is not higher than the full-channel uncertainty If so, it is determined that there is no deviation in the corresponding channel pipeline, and the next step is executed.

3. The method for correcting the loop flow rate of the reactor coolant system according to claim 1, characterized in that In step S20, the following sub-steps are included: S21: Obtain and calculate the failure criterion using Equation (4) based on the functional tolerance, technical accuracy of the flow transmitter, and the number of redundant flow transmitters ; Equation (4) is expressed as: Among them, is the functional tolerance of the flow transmitter; is the technical accuracy of the flow transmitter; is a coefficient determined by the number of flow transmitters in a single-channel pipeline; S22: Obtain the average flow value measured by the flow transmitter in each channel pipeline and the flow standard value under the preset working condition; S23: Calculate and determine whether the difference between the average flow value and the flow standard value is not higher than the failure standard ; If so, perform the next step.

4. The method for correcting the loop flow rate of the reactor coolant system according to claim 1, wherein The preset working conditions include the full-power operation condition of the nuclear power unit and the hot shutdown condition of the steam generator of the nuclear power unit.

5. The method for correcting the loop flow rate of the reactor coolant system according to claim 4, characterized in that, In step S50, the following sub-steps are included: S51: Obtain the first flow standard value under the full-power operation condition of the nuclear power unit; S52: Calculate the corrected full-scale differential pressure value by using Equation (10) according to the actual differential pressure value of the corresponding channel pipeline and the first flow standard value; Equation (10) is expressed as: Wherein, is the corrected full-scale differential pressure value for each flow transmitter in any channel pipeline; is the first flow standard value; refers to the actual differential pressure value corresponding to the channel pipeline to be obtained.

6. The method for correcting the loop flow rate of the reactor coolant system according to claim 1, wherein In step S50, the following sub-steps are included: S53: Obtain the second flow standard value under the condition of the cooling heat stop of the steam generator of the nuclear power unit. S54: Calculate the corrected full-scale differential pressure value by using Equation (11) according to the actual differential pressure value of the corresponding channel pipeline and the second flow standard value; Equation (11) is expressed as: wherein, is the corrected full-scale differential pressure value for each flow transmitter in any channel pipeline; is the second flow standard value; refers to the actual differential pressure value corresponding to the channel pipeline to be determined.

7. The method for correcting the loop flow rate of the reactor coolant system according to claim 1, characterized in that, The measuring range of the flow transmitter is when it shows the full-scale differential pressure value.

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