CN116028758A - Method for predicting residual wall thickness of heat transfer tube of shell-and-tube heat exchanger of nuclear power plant - Google Patents
Method for predicting residual wall thickness of heat transfer tube of shell-and-tube heat exchanger of nuclear power plant Download PDFInfo
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- CN116028758A CN116028758A CN202211533042.2A CN202211533042A CN116028758A CN 116028758 A CN116028758 A CN 116028758A CN 202211533042 A CN202211533042 A CN 202211533042A CN 116028758 A CN116028758 A CN 116028758A
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Abstract
The invention relates to a method for predicting the residual wall thickness of a heat transfer tube of a shell-and-tube heat exchanger of a nuclear power plant, which is used for obtaining the defect depth of the heat transfer tube at each cycle end before the first cycle end, calculating the expansion rate of the defect depth of the heat transfer tube according to the defect depth of the heat transfer tube at each cycle end before the first cycle end, predicting the defect depth of the heat transfer tube after the completion of the first cycle end, and predicting the residual wall thickness of the heat transfer tube after the completion of the first cycle end according to the defect depth of the heat transfer tube after the completion of the first cycle end. The method is based on the data of the residual wall thickness of the eddy current inspection of the heat transfer tube, and fits a defect growth rate equation according to a mathematical calculation method aiming at the heat transfer tube with the defect type of pitting or wearing, so as to iteratively calculate the residual wall thickness of the heat transfer tube at the end of the future cycle life.
Description
Technical Field
The invention belongs to the technical field of heat transfer tube maintenance, and particularly relates to a method for predicting the residual wall thickness of a heat transfer tube of a shell-and-tube heat exchanger of a nuclear power plant.
Background
The shell-and-tube heat exchanger is an important device in a thermodynamic system of a nuclear power plant, which takes heat transfer as a main process (or purpose), and the performance of the heat exchanger directly influences the safe, stable and economic operation of the device, and further influences the safe, stable and economic operation of the system and the unit. During operation, the primary failure mode of the heat exchanger is structural failure, manifested primarily as degradation, failure of the various structural components, including support plates, access tubes, impact plates, heat transfer tubes, and the like. Studies of the reliability data system of a nuclear power plant show that heat transfer tube failure is the failure mechanism with the largest duty cycle of a shell-and-tube heat exchanger. When a heat transfer tube fails or is predicted to fail, then a preventive tube blocking of the heat transfer tube is required. In summary, how to ensure safe, stable and economical operation of shell-and-tube heat exchangers is an important issue facing nuclear power plants.
If unexpected defect expansion of the heat transfer pipe of the heat exchanger occurs to cause leakage failure of the heat transfer pipe with large area, a series of system equipment related to the heat exchanger may have to be taken out of operation, so that the unit has to be operated in a power-down mode, and even the unit enters a shutdown maintenance mode; if the number of defective tubes of the heat transfer tube of the heat exchanger has been found to have reached the "allowable tube plugging margin" in the design specification during the secondary overhaul or forced shut down overhaul, the heat exchanger tube bundle or whole plant has to be better, but it takes at least 4 years to restock the heat exchanger tube bundle or whole plant, which can have serious consequences for a long-term shutdown of the unit. There is a need to monitor and predict the structural integrity of heat transfer tubes of a heat exchanger.
In order to monitor the structural integrity of the heat transfer tube of the heat exchanger, timely find out the occurrence of defects and the expansion condition of the predicted defect depth, the heat transfer tube needs to be subjected to periodic wall thickness vortex inspection and prospective residual wall thickness prediction calculation.
Disclosure of Invention
In view of the foregoing drawbacks and deficiencies of the prior art, it is an object of the present invention to at least solve one or more of the above-mentioned problems of the prior art, in other words, to provide a method for predicting the residual wall thickness of a heat transfer tube of a shell-and-tube heat exchanger of a nuclear power plant, which satisfies one or more of the aforementioned needs.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for predicting a remaining wall thickness of a heat transfer tube of a shell-and-tube heat exchanger of a nuclear power plant, which is used for predicting the remaining wall thickness of the heat transfer tube after completion of the end of a first cycle, and specifically comprises the following steps:
s1, acquiring the defect depth of a heat transfer tube at the end of each cycle before the end of the first cycle;
s2, calculating the expansion rate of the defect depth of the heat transfer tube according to the defect depth of the heat transfer tube at each cycle end before the cycle end of the first time;
s3, predicting the defect depth of the heat transfer tube after finishing the end of the first cycle according to the expansion rate of the defect depth of the heat transfer tube;
s4, predicting the residual wall thickness of the heat transfer tube after the end of the first circulation according to the defect depth of the heat transfer tube after the end of the first circulation.
2. The method for predicting the residual wall thickness of a heat transfer tube of a shell-and-tube heat exchanger of a nuclear power plant according to claim 1, wherein the step S2 specifically comprises:
s21, screening out a heat transfer tube which completes eddy current rechecking of multiple times of circulation before the end of the first time of circulation and taking the heat transfer tube as a data source heat transfer tube;
s22, forming a heat transfer tube defect depth data set by using the heat transfer tube defect depth of the data source heat transfer tube at the end of each cycle;
s23, fitting and calculating the expansion rate of the defect depth of the heat transfer tube by using the data set of the defect depth of the heat transfer tube.
As a preferred scheme, the fitting of step S23 is specifically:
and (3) using a least square method to complete linear regression fit of the expansion rate of the defect depth of the heat transfer tube.
As a preferred embodiment, the calculation in step S23 specifically includes:
and (5) completing expansion rate calculation of the defect depth of the heat transfer tube by using a coefficient method to be determined.
As a preferred embodiment, step S1 uses specifically the heat transfer tube defect depth values actually measured at the 1 st cycle end and the 2 nd cycle end.
As a preferable mode, the defect depth of the heat transfer tube at the end of the 1 st cycle is set: d1 =d1act;
depth of heat transfer tube defect at end of cycle 2: d2 =d2act;
d1act and D2act are the depths of heat transfer tube defects actually measured at the end of the 1 st and 2 nd cycles, respectively.
As a preferable scheme, the expansion rate K of the defect depth of the heat transfer tube 2 Calculated as follows:
wherein, (T) 1 ∪T 2 ) Is the heat transfer tube defect depth at the end of the 1 st cycle and the heat transfer tube defect depth data set at the end of the 2 nd cycle, | (T) 1 Y T 2 ) I is the number of points of the heat transfer tube defect depth dataset.
As a preferred embodiment, the depth value of the defect of the heat transfer tube at the end of the 3 rd cycle is calculated as follows:
Compared with the prior art, the invention has the beneficial effects that:
the method is based on the data of the residual wall thickness of the eddy current inspection of the heat transfer tube, and fits a defect growth rate equation according to a mathematical calculation method aiming at the heat transfer tube with the defect type of pitting or wearing, so that the residual wall thickness of the heat transfer tube at the end of the future cycle life is calculated in an iterative manner. By the calculation method, the growth rate of all defects of the heat transfer tubes of the heat exchanger can be quantitatively obtained, and the residual wall thickness value of each heat transfer tube after the heat transfer tube is subjected to one or a plurality of subsequent cycle operation conditions is calculated in an iterative manner according to the actual measurement result of the defect depth of the heat transfer tube during overhaul.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below in connection with the embodiments of the present application.
In the following description, various embodiments of the present application are provided, as alternative or in combination, between different embodiments, and thus the present application is also to be construed as embracing all possible combinations of the same and/or different embodiments as described. Thus, if one embodiment includes feature A, B, C and another embodiment includes feature B, D, then the present application should also be considered to include embodiments that include one or more of all other possible combinations including A, B, C, D, although such an embodiment may not be explicitly recited in the following.
The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements described without departing from the scope of the application. Various examples may omit, replace, or add various procedures or components as appropriate. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.
The embodiment of the application provides a method for predicting the residual wall thickness of a heat transfer tube of a shell-and-tube heat exchanger of a nuclear power plant, which is used for predicting the residual wall thickness of the heat transfer tube after the end of a first cycle, and comprises the following steps:
the invention simulates the defect depth change process of the heat transfer tube at different circulation stages of the unit, and supposing that the last circulation stage of the above-mentioned several times is the (n+1) th circulation, the last circulation stage of the (n+1) th circulation is the current overhaul, the thickness of the heat transfer tube at the last circulation stage of the (n+1) th circulationDepth of defect D n+1 Calculation method and residual wall thickness X n+1 The calculation formula is shown in the following table 1:
TABLE 1 calculation of Heat transfer tube defect depth and residual wall thickness at the end of the n+1th cycle
| Defect depth calculation formula | Residual wall thickness calculation formula |
| D n-1 ＝D n-1_act | X n-1 ＝(1-D n-1_act )·δ |
| D n ＝D n_act2 | X n ＝(1-D n_act )·δ |
| D n+1 ＝f(D n ) | X n+1 ＝(1-D n+1 )·δ |
Wherein:
delta: the heat transfer tube is designed with a wall thickness;
D act : the actual measured defect depth of the heat transfer tube at the current overhaul is expressed as a percentage of the remaining wall thickness of the heat transfer tube relative to the design wall thickness delta.
First, step S1 is performed to obtain the depth of the heat transfer tube defect at the end of each cycle before the end of the first cycle.
S2, calculating the expansion rate of the defect depth of the heat transfer tube according to the defect depth of the heat transfer tube at each cycle end before the cycle end of the first time.
According to the method, a heat transfer tube wall thickness damage model is built through a defect depth actual measurement data set of heat transfer tube vortex inspection at the end of an n-1 cycle and an n cycle, and the defect growth rate of the heat transfer tube wall thickness is calculated.
It is assumed that the heat exchanger apparatus is operated for n cycles (n.gtoreq.1) in total, and that measured defect depth data for eddy current inspection of the heat transfer tube has been collected at the end of both the n-1 th cycle and the n-th cycle (when the secondary overhaul). For those heat transfer tubes with defects, all the defect depth values were collated into a data set, and the defect depth expansion rate of the heat transfer tube with defects (hereinafter simply referred to as a defect tube) of the heat exchanger was calculated as shown in the following table 2:
table 2 heat exchanger heat transfer tube defect depth spread rate calculation
Wherein:
K n or K n-1 : completing a fitted straight line of a linear regression equation, representing the growth rate of the defect depth during the nth cycle or the n-1 th cycle; wherein K is n-1 For reference, can be used for evaluating the calculated value K n Is reasonable in (1);
|(T n-2 Y T n-1 ) I (L): representing the T n-1 ∪T n-2 Points of the union set;
|(T n-1 Y T n ) I (L): representing the T n-1 ∪T n Points of the union set.
In the actual operation process of the power plant, eddy current rechecking can be carried out on the defect heat transfer pipe (unblocked) found in the previous overhaul during each subsequent overhaul period so as to calculate and obtain an accurate defect depth expansion speed value K n The method comprises the steps of carrying out a first treatment on the surface of the In addition, K can also be used n-1 To evaluate the calculated value K n Is reasonable.
The step S2 preferably specifically comprises the following steps:
s21, screening out the heat transfer tube which completes eddy current rechecking of multiple times of circulation before the end of the first time of circulation, and taking the heat transfer tube as a data source heat transfer tube.
Specifically, in one embodiment of the present application, step S21 takes the remaining wall thickness of the heat transfer tube of the high-pressure feedwater heater (shell-and-tube heat exchanger) at the end of the 3 rd cycle of the three-door nuclear power prediction No. two unit as an example. Both the eddy current inspection of the heat transfer tube and the eddy current review of the defective tube were performed during the overhaul at the end of the 1 st and 2 nd cycles, so that:
depth of heat transfer tube defect at end of cycle 1: d1 =d1act;
depth of heat transfer tube defect at end of cycle 2: d2 =d2act;
wherein D1act and D2act are heat transfer tube defect depth values obtained through actual measurement at the end of the 1 st and 2 nd cycles respectively.
S22, forming a heat transfer tube defect depth data set by using the heat transfer tube defect depth of the data source heat transfer tube at the end of each cycle;
screening out the defect tubes of the eddy current retest after the 2 nd cycle in the 1 st cycle, and taking the depth values of the defects as a data set (T 1 ∪T 2 ) And the point number of the set is | (T) 1 ∪T 2 )|。
S23, fitting and calculating the expansion rate of the defect depth of the heat transfer tube by using the data set of the defect depth of the heat transfer tube.
Thereby, K is related to the depth spread rate of heat transfer tube defects during cycle 2 2 The calculation formula is as follows:
s3, predicting the defect depth of the heat transfer tube after the end of the first cycle is finished according to the expansion rate of the defect depth of the heat transfer tube.
The increase rate K of all defects of the heat transfer tube of the heat exchanger at the end of a certain cycle can be quantitatively obtained by the calculation method shown in the table 2 of the invention n The method comprises the steps of carrying out a first treatment on the surface of the Then according to the heat transfer tube T during the current overhaul n Defect depth measurement result D of { a … … v } n And b (using the coefficient of uncertainty method), iteratively calculating the number of cycles each heat transfer tube undergoesThe value of the remaining wall thickness after the ring operating conditions. Assuming the nth cycle is the current overhaul, the calculation method is as follows:
TABLE 3 predictive calculations of defect depth values and residual wall thickness values for heat transfer tubes of heat exchanger
Wherein:
K n or K n-1 : take the calculated values in Table 2, where K n-1 For reference, can be used for evaluating the calculated value K n Is reasonable in (1); and in the ith cycle after the nth cycle, a fixed K is always used n And carrying out predictive calculation on the value.
b: the intercept of a fitting straight line of a linear regression equation can be used for obtaining a value b by substituting the actual measured value of the defect depth of the defect tube of the existing front and rear cycles by using a undetermined coefficient method;
n+i: the ith cycle after the end of the nth cycle (when the next overhaul).
The defect depth value and the residual wall thickness value of the heat transfer tube of the heat exchanger shown in Table 3 are calculated according to the method for predicting the residual wall thickness of the heat transfer tube of the shell-and-tube heat exchanger of a nuclear power plant of the present invention
Specifically, based on the above example, predictive calculation of the heat transfer tube defect depth value at the end of the 3 rd cycle:
D 3 ＝K 2 ·D 2 +b, b can be obtained by substituting the measured eddy current inspection values at the time of the 1 st and 2 nd cycle end-of-cycle overhaul using the coefficient to be determined method act A value;
then:
s4, predicting the residual wall thickness of the heat transfer tube after the end of the first circulation according to the defect depth of the heat transfer tube after the end of the first circulation.
Also based on the above example, the predicted values for the remaining wall thickness values of the heat transfer tube at the end of the 3 rd cycle are:
according to the method, the residual wall thickness of the heat transfer pipe at the later cycle end stage under the condition of a relatively fixed corrosion/aging mechanism of the nuclear power plant system is predicted according to the calculated depth expansion rate of the defect of the heat transfer pipe, so that long-period planning management of the heat exchanger of the nuclear power plant is guided. By reasonable preventive maintenance strategy, the ageing speed and defect expansion speed of the heat transfer tube are relieved, and the service life of the heat exchanger equipment is prolonged
It will be apparent to those skilled in the art that the embodiments of the present application may be implemented in software and/or hardware. "module" in this specification refers to software and/or hardware capable of performing a specific function, either alone or in combination with other components, such as Field programmable gate arrays (Field-Programmable Gate Array, FPGA), integrated circuits (Integrated Circuit, IC), etc.
It should be noted that, for simplicity of description, the foregoing method embodiments are all expressed as a series of action combinations, but it should be understood by those skilled in the art that the present application is not limited by the order of actions described, as some steps may be performed in other order or simultaneously in accordance with the present application. Further, those skilled in the art will also appreciate that the embodiments described in the specification are all preferred embodiments, and that the acts and modules referred to are not necessarily required in the present application.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and for parts of one embodiment that are not described in detail, reference may be made to related descriptions of other embodiments.
In the several embodiments provided in this application, it should be understood that the disclosed apparatus may be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative, such as the division of the units, merely a logical function division, and there may be additional manners of dividing the actual implementation, such as multiple units or components may be combined or integrated into another system, or some features may be omitted, or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be through some service interface, device or unit indirect coupling or communication connection, electrical or otherwise.
The modules described as separate components may or may not be physically separate, and components shown as modules may or may not be physical modules, i.e., may be located in one place, or may be distributed over a plurality of network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
In addition, each functional module in each embodiment of the present application may be integrated in one processing unit, or each module may exist alone physically, or two or more modules may be integrated in one unit. The integrated modules may be implemented in hardware or in software functional modules.
The integrated modules, if implemented in the form of software functional modules and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, embodiments of the present application provide a computer program product that, when run on a computer, causes the computer to perform and implement all or part of the flow of the method embodiments described above.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
The foregoing is merely exemplary embodiments of the present disclosure and is not intended to limit the scope of the present disclosure. That is, equivalent changes and modifications are contemplated by the teachings of this disclosure, which fall within the scope of the present disclosure. Embodiments of the present disclosure will be readily apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This application is intended to cover any adaptations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a scope and spirit of the disclosure being indicated by the claims.
Claims (8)
1. A method for predicting the residual wall thickness of a heat transfer tube of a shell-and-tube heat exchanger of a nuclear power plant is used for predicting the residual wall thickness of the heat transfer tube after the end of a first cycle, and is characterized by comprising the following steps:
s1, acquiring the defect depth of a heat transfer tube at the end of each cycle before the end of the first cycle;
s2, calculating the expansion rate of the defect depth of the heat transfer tube according to the defect depth of the heat transfer tube at each cycle end before the first cycle end;
s3, predicting the defect depth of the heat transfer tube after the end of the first cycle is finished according to the expansion rate of the defect depth of the heat transfer tube;
s4, predicting the residual wall thickness of the heat transfer tube after the end of the first number of times of circulation according to the defect depth of the heat transfer tube after the end of the first number of times of circulation.
2. The method for predicting the residual wall thickness of a heat transfer tube of a shell-and-tube heat exchanger of a nuclear power plant according to claim 1, wherein the step S2 specifically comprises:
s21, screening out the heat transfer tubes subjected to eddy current rechecking, which are circulated for a plurality of times before the last circulation for the first time, and taking the heat transfer tubes as data source heat transfer tubes;
s22, forming a heat transfer tube defect depth data set by using the heat transfer tube defect depth of the data source heat transfer tube at the end of each cycle;
s23, fitting and calculating the expansion rate of the defect depth of the heat transfer tube by using the defect depth data set of the heat transfer tube.
3. The method for predicting the residual wall thickness of a heat transfer tube of a shell-and-tube heat exchanger of a nuclear power plant according to claim 2, wherein the fitting in the step S23 is specifically:
and (3) using a least square method to complete linear regression fit of the expansion rate of the defect depth of the heat transfer tube.
4. The method for predicting the residual wall thickness of a heat transfer tube of a shell-and-tube heat exchanger of a nuclear power plant according to claim 2, wherein the calculation in the step S23 is specifically:
and using a pending coefficient method to complete the expansion rate calculation of the defect depth of the heat transfer tube.
5. The method for predicting the residual wall thickness of a heat transfer tube of a shell-and-tube heat exchanger of a nuclear power plant according to claim 2, wherein the step S1 specifically uses the depth values of the defects of the heat transfer tube actually measured at the 1 st cycle end and the 2 nd cycle end.
6. The method for predicting residual wall thickness of heat transfer tube in shell-and-tube heat exchanger in nuclear power plant as claimed in claim 5, wherein the defect depth of the heat transfer tube at the end of the 1 st cycle is set: d1 =d1act;
depth of heat transfer tube defect at end of cycle 2: d2 =d2act;
d1act and D2act are the depths of heat transfer tube defects actually measured at the end of the 1 st and 2 nd cycles, respectively.
7. The method for predicting residual wall thickness of heat transfer tube of shell-and-tube heat exchanger in nuclear power plant as set forth in claim 6, wherein said expansion rate K of defect depth of heat transfer tube 2 Calculated as follows:
wherein, (T) 1 ∪T 2 ) Is the heat transfer tube defect depth at the end of the 1 st cycle and the heat transfer tube defect depth data set at the end of the 2 nd cycle, | (T) 1 Y T 2 ) I is the number of points of the heat transfer tube defect depth dataset.
8. The method for predicting residual wall thickness of heat transfer tube in shell-and-tube heat exchanger in nuclear power plant as claimed in claim 7, wherein the depth value of defect of heat transfer tube at the end of the 3 rd cycle is calculated by the following formula:
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